ELECTRONIC 1 EPC - Oilgear · The EPC is a microcontroller-operated motion controller and amplifier for servo controlled pumps and valves. The unit can be configured for several

ELECTRONIC 1

Telephone:Fax:E-Mail:

(414) 327-1700(414) [email protected]

Oilgear Automation Systems2300 So. 51st. Street

Milwaukee, WI USA 53219

Issued: September 1999Bulletin 836100A

TECHNICAL DOCUMENT

EPCSERVO AMPLIFIER MODULE

Part Number L723888-xxx

AnalogInputs

Program Block 1(Program 0..10)

Program Block 2(Program 0..10)

BlockSelection

PumpController

Stroke Feedback

Pressure Feedback

DigitalInput

DigitalOutputDiagnostics

AnalogOutput

1 Introduction

The EPC is a microcontroller-operated motion controller and amplifier forservo controlled pumps and valves. The unit can be configured for severaltypes of control applications including:n Flow Controln Pressure Control or Load Controln Flow Control with Pressure Limit (PQ-Control)n Horsepower Control (Pump Stroke and Pressure)

2 Basic System Overview

The EPC allows one (1) single control axis with a power amplifier to driveVS-, VV- and VM-controlled pumps and valves. The basic pump controllerconfiguration allows for fast (up to a 1600Hz) closed loop response withboth stroke position and pressure feedback. In addition, two (2) independentfunction programs can be dynamically selected with a digital input signal. The unit provides a digitaloutput for simple diagnostics or a watchdog signal.

Two (2) general-purpose analog inputs are provided for command and pressure feedback signals (± 10VDC, 0-to-20 mA, or 4-to-20 mA). Additionally, one (1) analog input is provided as a dedicated fine-adjustable LVDT or DCDT stroke feedback device. The module allows for the option of a second LVDTor DCDT stroke feedback or a low-power programmable output signal.

The device is configured by first assigning one of ten (10) built-in function programs to each of the two(2) program blocks. Typically, the output of the function programs is then passed to the PumpController, which provides the valve command.

Figure 1: EPC Module

Figure 2: System Overview

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If the full features of the module are used, up to three (3) independent closed loop PI (Proportional withIntegral) control algorithms are utilized. Most function programs provide a closed loop control algorithmfor pressure or stroke, while the Pump Controller can be configured for both stroke and power feedback.

The module is programmable either through the on-board keypad and display, or optimally through thePC Interface software.

Table of Contents1 Introduction ............................................................................................................................................. 12 Basic System Overview ........................................................................................................................... 13 General Instructions................................................................................................................................ 4

3.1 Password Protection ......................................................................................................................... 43.2 LCD Display Groupings .................................................................................................................. 43.3 Menu Selection and Configuration .................................................................................................. 5

3.3.1 Changing the Menu Item Number .......................................................................................... 53.3.2 Changing the Menu Value ...................................................................................................... 6

3.4 PC Interface Groupings.................................................................................................................... 64 Module Configuration ............................................................................................................................. 7

4.1 General Configuration ..................................................................................................................... 74.1.1 Password Protection (000) ..................................................................................................... 74.1.2 Operating Modes (200) .......................................................................................................... 7

4.1.2.1 Dynamic Function Selection with Fault Monitor ......................................................... 74.1.2.2 Dynamic Function Selection with Watchdog Monitor ................................................. 84.1.2.3 Static Function Selection with Watchdog Daisy Chain ................................................ 8

4.1.3 Program Block Configuration (21x) ...................................................................................... 84.2 Program Configuration .................................................................................................................... 9

4.2.1 Overview ................................................................................................................................ 94.2.2 PI Control Algorithms .......................................................................................................... 104.2.3 Pressure Control Programs (40x, 41x) ................................................................................. 104.2.4 Flow with Pressure Limit Programs (42x, 43x) ................................................................... 124.2.5 Load Sense Control Programs (44x, 45x) ............................................................................ 154.2.6 Simple Flow Control Programs (46x, 47x) .......................................................................... 184.2.7 Advanced Flow with Pressure Limit Programs (48x, 49x) .................................................. 19

4.3 Pump Controller Configuration ..................................................................................................... 194.3.1 Overview .............................................................................................................................. 194.3.2 Configuration........................................................................................................................ 19

4.3.2.1 Function Zero Stroke Command ................................................................................ 194.3.2.2 Stroke Controller ......................................................................................................... 204.3.2.3 HP Limiter .................................................................................................................. 204.3.2.4 Output Polarity ............................................................................................................ 214.3.2.5 Output Current Limit .................................................................................................. 21

4.3.3 Configuration Example ........................................................................................................ 224.4 Analog IO Configuration ............................................................................................................... 23

4.4.1 General Purpose Analog Input Configuration ...................................................................... 23

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4.4.2 LVDT/DCDT Fine-Adjustable Analog Input Configuration ............................................... 264.5 Ramp Configuration ...................................................................................................................... 274.6 Advanced Configuration ................................................................................................................ 29

4.6.1 LVDT Adjustment Algorithm .............................................................................................. 294.6.1.1 Adjustment Mode ....................................................................................................... 294.6.1.2 Determining LVDT Configuration Range .................................................................. 314.6.1.3 Adjustment Algorithm ................................................................................................ 32

4.6.2 HP Limit Factor Calculation ................................................................................................ 344.6.2.1 Experimental HP Limit Factor.................................................................................... 344.6.2.2 Theoretical HP Limit Factor ....................................................................................... 35

5 Module Diagnostics ............................................................................................................................... 365.1 Diagnostic Representation of Numbers ......................................................................................... 36

5.1.1 DAC Counts ......................................................................................................................... 365.1.2 Voltage and Percentages ...................................................................................................... 37

5.2 Basic Diagnostics ........................................................................................................................... 375.3 Programmable Output Diagnostic ................................................................................................. 375.4 Advanced Diagnostics ................................................................................................................... 38

5.4.1 Module Faults ....................................................................................................................... 385.4.2 Run-Time Messages ............................................................................................................. 39

6 Technical Data ....................................................................................................................................... 406.1 Module Pin-Out ............................................................................................................................. 406.2 Test Point, DIP-Switch, and Pot Settings ...................................................................................... 416.3 Sample Connection Diagram ......................................................................................................... 426.4 Specifications ................................................................................................................................. 436.5 IO Summary ................................................................................................................................... 43

7 Technical Support ................................................................................................................................. 448 Ordering Information ........................................................................................................................... 45

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3 General Instructions

3.1 Password Protection

The EPC allows for edit protection of all programmable parameters. Please refer to Section 4.1.1 fora thorough discussion of Password Protection.

3.2 LCD Display Groupings

The EPC is designed for a variety of applications. A numerical menu is provided to program thedevice through the on-board keypad and display. The menu items range from 000 to 999 and areloosely grouped in the following manner:

000 Password Protection2xx Program Selection and Digital IO Configuration4xx Program Configuration80x, 81x Pump Controller Configuration83x, 84x Fine-Adjustable Input Configuration (LVDT/DCDT)85x, 86x General Purpose Input Configuration87x Ramp Configuration90x, 91x, 92x, 93x General Diagnostics96x Factory Preset Fine DAC Adjustment98x, 999 Fault Diagnostics

Most menu displays show three (3) items:n The Menu Item Number.n A brief Text Description of the Menu Item.n The Configuration or Diagnostic Value of the Menu Item.

Menu I temNumber

TextDescription

Configuration orDiagnostic Value

Figure 3: Standard Menu Layout

For some menu items, a graphical indicator bar corresponding to the Configuration or DiagnosticValue is provided.

Menu I temNumber

TextDescription

Configuration orDiagnostic Value

Figure 4: Menu Layout with Graphical Indicator Bar

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3.3 Menu Selection and Configuration

The onboard keypad on the front panel allows for selection and editing of menu items. The menuitems are defined by a number that appears in the upper left corner of the display and is always athree-digit number in the range of 000 to 999. The position of the underscore indicates the editabledigit.

3.3.1 Changing the Menu Item Number

The cursor keys change the position of the editable digit cursor. For instance, if the menu isinitially:

Figure 5

Pressing the right cursor key moves the editable digit cursor right to the next digit:

Figure 6

Figure 7

Conversely, pressing the left cursor key moves the editable digit cursor left to the previous digit:

Figure 8

Figure 9

If the editable digit cursor is under the Menu Item Number, pressing the increment or decrementkeys changes the Menu Item Number.

For example, if the menu and cursor position is initially:

Figure 10

Pressing the Increment key changes the Menu Item Number in the forward direction.

Figure 11

Conversely, the Decrement key changes the Menu Item Number in the reverse direction.

Figure 12

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Note that only valid menu items can be selected so the increment and decrement keys will notalways correspond to a normal numerical order. For example, the user will increment directlyfrom menu item 000 to 200 since no other menu item exists between these two items.

3.3.2 Changing the Menu Value

If the menu item refers to an editable field, the editable digit cursor can be extended beyond themenu entry using the right cursor key. For example, pressing the right cursor key for the menu:

Figure 13

extends the editable digit cursor into the value field.

Figure 14

In addition to the position of the editable digit cursor, the triangle to the left of the menu itemnumber indicates that the controller is in edit mode. Pressing the Increment or Decrement keysallows the user to change the menu value. Pressing the left cursor field allows the user to returnthe editable digit cursor to the menu item.

3.4 PC Interface Groupings

The PC interface provides a more optimal programming and monitoring interface. A toolbar menuloosely groups functions in the following manner:

File File, Print, and Communication CommandsGeneral Password and Communication Setup,

Program Selection and Digital IO Configuration(menu items 000 and 2xx)

Program Program Configuration (menu items 4xx)Pump Controller Pump Controller Configuration

(menu items 8xx)Diagnostics General Purpose Input Configuration, Configuration Fine-Adjustable Input Configuration (LVDT/DCDT),

Diagnostics(menu items 83x, 84x, 85x, 86x, 92x, and 93x)

Diagnostics Ramp Configuration and Advanced HP Limit Setup Advanced (menu items 87x and 810)Help User Help

Items are programmable either through Numeric Input boxes or Drop-Down List boxes.

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4 Module Configuration

4.1 General Configuration

General Configuration parameters include Password, Mode, and Communication Setup Parameters.

4.1.1 Password Protection (000)Menu Item Range Description000 0 to 255 Password

Table 1: Password Protection

The EPC has a simple lockout password that can be used to protect the program configurationfrom accidental changes. The password is entered through menu item 000 or by typing apassword from the General Configuration form of the PC interface.

If the password is set to 249, the user will be able to modify any editable entry. Any otherpassword will place the device in read-only mode. The user will not be able to modify any entryin this mode.

4.1.2 Operating Modes (200)Menu Item Range Description200 0 to 2 Operating Mode:

0: Dynamic Function Selection with Fault Monitor1: Dynamic Function Selection with Watchdog Monitor2: Static Function Selection with Watchdog Daisy Chain

Table 2: Operating Modes

The EPC has three (3) operating modes. Depending on the operating mode, the EPC reacts to thedigital input to make one of the two program blocks active.

4.1.2.1 Dynamic Function Selection with Fault Monitor

This operating mode is selected by setting menu item 200 to 0, or by choosing Mode 0:Dynamic Function Selection with Fault Monitor from the General Configuration form of thePC Interface.

In this operating mode, the digital input selects which program block is active. If the digitalinput is low ( 5VDC), Program Block 2 is made active and theprogram defined in menu 211 is used. Refer to Section 4.1.3 for discussion of ProgramBlock Configuration (21x).

The digital output provides standard condition status. If no faults are present, the digitaloutput will be high (Vsupply); If faults are present, the digital output will be low (0 VDC).Refer to Section 5.4 for information on module fault and message conditions.

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4.1.2.2 Dynamic Function Selection with Watchdog Monitor

This operating mode is selected by setting menu item 200 to 1, or by choosing Mode 1:Dynamic Function Selection with Watchdog Monitor from the General Configuration formof the PC Interface.

In this operating mode, the digital input selects which program block is active. If the digitalinput is low ( 5VDC), Program Block 2 is made active and theprogram defined in menu 211 is used. Refer to Section 4.1.3 for discussion of ProgramBlock Configuration (21x).

The digital output provides a watchdog signal of approximately 100 Hz.

4.1.2.3 Static Function Selection with Watchdog Daisy Chain

This operating mode is selected by setting menu item 200 to 2, or by choosing Mode 2: StaticFunction Selection with Watchdog Daisy Chain from the General Configuration form of thePC Interface.

In this operating mode, Program Block 1 is always active and the program defined in menu210 is used. Program Block 2 is always inactive and menu item 211 has no function. Referto Section 4.1.3 for discussion of Program Block Configuration (21x).

The digital input is passed through the module into the digital output. In this way, one singlewatchdog timer can be used for a number of EPC modules. One EPC module would need tobe configured for Mode 1: Dynamic Function Selection with Watchdog Monitor; theremaining EPCs would be configured for Mode 2. Any module failure would break the daisychain.

4.1.3 Program Block Configuration (21x)Menu Item Range Description210 0 to 10 Program Selection for Program Block 1

0: No Program used for Block 1(refer to Section 4.3.2.1)

1-10: Program 1 to 10 used for Block 1

211 0 to 10 Program Selection for Program Block 20: No Program used for Block 2

(refer to Section 4.3.2.1)1-10: Program 1 to 10 used for Block 2

Table 3: Program Block Configuration

The program block configuration parameters are used in conjunction with the module operatingmodes (refer to Section 4.1.2) to assign pre-defined programs to the two (2) program blocks.

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Modes 0 and 1: For operating modes 0 (Dynamic Function Selection with Fault Monitor) and 1(Dynamic Function Selection with Watchdog Monitor) the digital input is used to make one ofthe two function blocks active. Menu items 210 and 211, in turn, select which pre-definedfunction program is made active for the function block.

Example 1: Operating Mode (menu item 200) is set to 0 (Dynamic Function Selection with FaultMonitor). Program Selection for Program Block 1 (menu item 210) is set to 1 (Pressure Control)and Program Selection for Program Block 2 (menu item 211) is set to 3 (Flow with PressureLimit Control).

If the digital input is low ( 5VDC), Program Block 2 is madeactive and the active program is Program 3 (Flow with Pressure Limit Control).

Example 2: Again, operating Mode is set to 0. Program Selection for Program Block 1 (menuitem 210) is set to 1 (Pressure Control) and Program Selection for Program Block 2 (menu item211) is set to 0 (No Program).

If the digital input is low ( 5VDC), Program Block 2 is madeactive, but since no program is activated, the module uses a special zero function command tocommand the pump controller (refer to Section 4.3.2.1 for configuration of the Function ZeroStroke Command).

Mode 2: For operating mode 2 (Static Function Selection with Watchdog Daisy Chain) thedigital input is used as a watchdog input signal. Therefore, no dynamic function selection ispossible. In this mode, Program Block 1 is always active and menu 210 defines the activefunction program. Menu 211 has no function in operating mode 2.

The program blocks are selected from the General Configuration form of the PC Interface.

4.2 Program Configuration

4.2.1 Overview

The EPC offers 10 pre-defined programs. The programs range from simple flow control toadvanced functionality. Five different types of programs exist, and the module provides twodistinct copies of each program.

Programs 1 and 2 provide Pressure Control programs. Programs 3 and 4 provide Flow withPressure Limit Control programs. Programs 5 and 6 provide Load Sense Control programs.Programs 7 and 8 provide Simple Flow Control programs. Finally, Programs 9 and 10 provideanother version of a Flow with Pressure Limit Control.

Under usual circumstances, the pre-defined programs are used as outer loop control. The outputof the pre-defined programs is normally passed through to the Pump Controller module (refer toSection 4.3.1 for an overview of the Pump Controller).

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4.2.2 PI Control Algorithms

Most programs use a PI (Proportional with Integral) control scheme. Although an advancedtutorial on digital control systems is beyond the scope of this technical document some level ofknowledge and experience is necessary to successfully implement the control programs.

The basis of a PI controller is that an output signal is produced due to a difference between acommand and feedback term (the difference is usually referred to as Error). The output signalfor a PI control is made of a proportional error signal combined with an integral error signal.

4.2.3 Pressure Control Programs (40x, 41x)Menu Item Range Description400 1 to 100 Program 1: Pressure Command Preset401 0 to 5 Program 1: Pressure Command Source402 1 to 5 Program 1: Pressure Feedback Source403 0 to 1 Program 1: Program Output Destination404 0 to 100 Program 1: KP405 0 to 100 Program 1: KI

410 1 to 100 Program 2: Pressure Command Preset411 0 to 5 Program 2: Pressure Command Source412 1 to 5 Program 2: Pressure Feedback Source413 0 to 1 Program 2: Program Output Destination414 0 to 100 Program 2: KP415 0 to 100 Program 2: KI

Table 4: Pressure Control Programs Configuration

Function Programs 1 and 2 provide for basic Pressure Control. Program 1 is configured in menuitems 400 through 405 or from the Program 1 form of the PC Interface. Program 2 is configuredin menu items 410 through 415 or from the Program 2 form of the PC Interface.

Pressure Command Preset: The Pressure Command Preset allows for direct numeric input forthe control program. The preset is configured as a percentage, with 0% being equivalent to a0VDC input signal and 100% being equivalent to a +10VDC signal.

Pressure Command Source: The Pressure Command Source selects the source of the pressurecommand for the program. Valid entries are (0) Preset Value, (1) Analog Input 1, (2) AnalogInput 2, (3) LVDT 1 (Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1. If the PresetValue is chosen, the Pressure Command Preset is used as the program command.

Pressure Feedback Source: The Pressure Feedback Source selects the source of the pressurefeedback for the program. Valid entries are (1) Analog Input 1, (2) Analog Input 2, (3) LVDT 1(Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1.

Program Output Destination: The Program Output Destination selects the output of theprogram. Valid entries are (0) Pump Controller or (1) Direct. If the Pump Controller is chosen,

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the output of the Program will be the input to the Pump Controller module. If Direct is chosen,the output of the Program will by-pass the Pump Controller module and is passed directly to theservo driver. Under most circumstances, the Pump Controller should be chosen as the outputdestination.

KP and KI : KP and KI provide the proportional and integral constants, respectively, for the PIcontrol algorithm. Both terms are expressed as 0 to 100% of a maximum value. The PI controlloop can be made a P-only control loop by setting the KI term to 0. Likewise, the PI control loopcan be made an I-only control loop by setting the KP term to 0.

Program Overview: The Pressure Control Program is a straightforward PI control algorithm.Comparing the command to the feedback value produces an error value. The error is multipliedby the KP and KI constants to produce the Yp and Yi contributions to the program output.

Figure 15: Pressure Control Program

Example: Figure 15 shows the Program 1 form of the PC Interface. The Pressure CommandSource is Analog Input 1 (menu 401=1) and the Pressure Feedback Source is Analog Input 2(menu 402=2). The Pressure Command Preset has a value of 50% (menu 400=50) although it isnot used for this particular example.

The error signal is produced by comparing the command to the feedback signals: 3068 - 3031 =37 (all display values are in DAC counts, refer to Section 5.1 for a discussion of the DiagnosticRepresentation of Numbers) The Yi and Yp signals are produced from the PI controller and theprogram output is roughly equal to their sum: 1280 + 27 = 1307. The Program Output is set to thePump Controller (menu 403=0).

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4.2.4 Flow with Pressure Limit Programs (42x, 43x)Menu Item Range Description420 0 to 100 Program 3: Flow Command Preset421 1 to 100 Program 3: Pressure Limit Preset422 0 to 5 Program 3: Flow Command Source423 0 to 5 Program 3: Pressure Limit Source424 1 to 5 Program 3: Pressure Feedback Source425 0 to 1 Program 3: Program Output Destination426 0 to 100 Program 3: KP427 0 to 100 Program 3: KI428 Program 3: Spare429 Program 3: Spare

430 0 to 100 Program 4: Flow Command Preset431 1 to 100 Program 4: Pressure Limit Preset432 0 to 5 Program 4: Flow Command Source433 0 to 5 Program 4: Pressure Limit Source434 1 to 5 Program 4: Pressure Feedback Source435 0 to 1 Program 4: Program Output Destination436 0 to 100 Program 4: KP437 0 to 100 Program 4: KI438 Program 4: Spare439 Program 4: Spare

Table 5: Flow with Pressure Limit Programs Configuration

Function Programs 3 and 4 provide for Flow with Pressure Limit Control. Program 3 isconfigured in menu items 420 through 429 or from the Program 3 form of the PC Interface.Program 4 is configured in menu items 430 through 439 or from the Program 4 form of the PCInterface.

Flow Command Preset: The Flow Command Preset allows for direct numeric input for thecontrol program. The preset is configured as a percentage, with 0% being equivalent to a 0VDCinput signal and 100% being equivalent to a +10VDC signal.

Pressure Limit Preset: The Pressure Limit Preset allows for direct numeric input for the controlprogram. The preset is configured as a percentage, with 0% being equivalent to a 0VDC inputsignal and 100% being equivalent to a +10VDC signal.

Flow Command Source: The Flow Command Source selects the source of the flow commandfor the program. Valid entries are (0) Preset Value, (1) Analog Input 1, (2) Analog Input 2, (3)LVDT 1 (Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1. If the Preset Value ischosen, the Flow Command Preset is used as the flow command.

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Pressure Limit Source: The Pressure Limit Source selects the source of the pressure limitcommand for the program. Valid entries are (0) Preset Value, (1) Analog Input 1, (2) AnalogInput 2, (3) LVDT 1 (Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1. If the PresetValue is chosen, the Pressure Limit Preset is used as the pressure limit command.

Pressure Feedback Source: The Pressure Feedback Source selects the source of the pressurefeedback for the program. Valid entries are (1) Analog Input 1, (2) Analog Input 2, (3) LVDT 1(Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1.

Program Output Destination: The Program Output Destination selects the output of theprogram. Valid entries are (0) Pump Controller or (1) Direct. If the Pump Controller is chosen,the output of the Program will be the input to the Pump Controller module. If Direct is chosen,the output of the Program will by-pass the Pump Controller module and is passed directly to theservo driver. Under most circumstances, the Pump Controller should be chosen as the outputdestination.


Program Overview: The Flow with Pressure Limit Control Program is a flow limit algorithm;the PI Control algorithm is only used if the pressure feedback is greater than the pressure limit.Comparing the command to the feedback value produces an error value. The error is multipliedby the KP and KI constants to produce tpe Yp and Yi contributions to the pressure limit signal.This signal, in turn, is used to limit the flow command to the program output. If the pressurelimit command is greater than the feedback signal, no pressure limit command will be added tothe Flow command; the flow command will be transposed directly through to the program output.

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Figure 16: Flow with Pressure Limit Program

Example: Figure 16 shows the Program 3 form of the PC Interface. The Flow Command Sourceis Analog Input 1 (menu 422=1). The Flow Command Preset is set to 10% (menu 420=10)although the Flow Command Preset is not used in this example.

The Pressure Limit Command Source is the Preset Value (menu 423=0), therefore the pressurelimit command is set at a 50% level (menu 421=50). The Pressure Feedback Source is AnalogInput 2 (menu 424=2).

The error signal is produced by comparing the Command to the Feedback signals: 3071 - 3087 =-16 (all displays values are in DAC counts, refer to Section 5.1 for a discussion of the DiagnosticRepresentation of Numbers). The Yi and Yp signals are produced from the PI controller and thePressure Limit value is roughly equal to their sum: -108 + -11 = -119.

The Pressure Limit Value is used to decrease the flow command: 2382 - 119 = 2263. Finally, theProgram Output is set to the Pump Controller (menu 425=0)

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4.2.5 Load Sense Control Programs (44x, 45x)Menu Item Range Description440 1 to 100 Program 5: Pressure Point 2 Preset441 1 to 100 Program 5: Delta Pressure Preset442 1 to 100 Program 5: Pressure Limit Preset443 0 to 5 Program 5: Pressure Point 2 Source444 0 to 5 Program 5: Delta Pressure Source445 0 to 5 Program 5: Pressure Limit Source446 1 to 5 Program 5: Pressure Point 1 Source447 0 to 1 Program 5: Program Output Destination448 0 to 100 Program 5: KP449 0 to 100 Program 5: KI

450 1 to 100 Program 6: Pressure Point 2 Preset451 1 to 100 Program 6: Delta Pressure Preset452 1 to 100 Program 6: Pressure Limit Preset453 0 to 5 Program 6: Pressure Point 2 Source454 0 to 5 Program 6: Delta Pressure Source455 0 to 5 Program 6: Pressure Limit Source456 1 to 5 Program 6: Pressure Point 1 Source457 0 to 1 Program 6: Program Output Destination458 0 to 100 Program 6: KP459 0 to 100 Program 6: KI

Table 6: Load Sense Programs Configuration

Function Programs 5 and 6 provide for Load Sense Control. Program 5 is configured in menuitems 440 through 449 or from the Program 5 form of the PC Interface. Program 6 is configuredin menu items 450 through 459 or from the Program 6 form of the PC Interface.

Pressure Point 2 Preset: The Pressure Point 2 Preset allows for direct numeric input for thecontrol program. The preset is configured as a percentage, with 0% being equivalent to a 0VDCinput signal and 100% being equivalent to a +10VDC signal.

Delta Pressure Preset: The Delta Pressure Preset allows for direct numeric input for the controlprogram. The preset is configured as a percentage, with 0% being equivalent to a 0VDC inputsignal and 100% being equivalent to a +10VDC signal.

Pressure Limit Preset: The Pressure Limit Preset allows for direct numeric input for the controlprogram. The preset is configured as a percentage, with 0% being equivalent to a 0VDC inputsignal and 100% being equivalent to a +10VDC signal.

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Pressure Point 2 Source: The Pressure Point 2 Source selects the source of the pressure point 2signal for the program. Valid entries are (0) Preset Value, (1) Analog Input 1, (2) Analog Input2, (3) LVDT 1 (Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1. If the PresetValue is chosen, the Pressure Point 2 Preset is used as the delta pressure point 2 command.

Delta Pressure Source: The Delta Pressure Source selects the source of the delta pressure signalfor the program. Valid entries are (0) Preset Value, (1) Analog Input 1, (2) Analog Input 2, (3)LVDT 1 (Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1. If the Preset Value ischosen, the Delta Pressure Preset is used as the delta pressure command.

Pressure Limit Source: The Pressure Limit Source selects the source of the pressure limitcommand for the program. Valid entries are (0) Preset Value, (1) Analog Input 1, (2) AnalogInput 2, (3) LVDT 1 (Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1. If the PresetValue is chosen, the Pressure Limit Preset is used as the pressure limit command.

Pressure Point 1 Source: The Pressure Point 1 Source selects the source of the pressurefeedback for the program. Valid entries are (1) Analog Input 1, (2) Analog Input 2, (3) LVDT 1(Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1.

Program Output Destination: The Program Output Destination selects the output of theprogram. Valid entries are (0) Pump Controller or (1) Direct. If the Pump Controller is chosen,the output of the Program will be the input to the Pump Controller module. If Direct is chosen,the output of the Program will by-pass the Pump Controller module and is passed directly to theservo driver. Under most circumstances, the Pump Controller should be chosen as the outputdestination.


EPC

P

U

P

U

Pressure P1 Pressure P2

Orifice

∆P = P1 - P2

Figure 17: Load Sense Circuit

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Program Overview: The Load Sense Control Program is one of the more complex controlalgorithms supplied with the EPC. The goal of the load sense control is to maintain a pressuredifference across an orifice (refer to Figure 17). Typically, two pressure transducers would beused to monitor two points in the hydraulic circuit. The pump flow would be controlled such that∆P = P1 - P2.

In addition to this basic control, a pressure limiter is added to ensure that the down-flow pressureat P2 does not reach a critical point. The controller command is the sum of the Point 2 Pressureand Delta Pressure signals, limited by the Pressure Limit Command. Comparing this commandwith the Point 1 Pressure signal results in an error value. The error is multiplied by the KP andKI constants to produce the Yp and Yi contributions to the program output signal.

Figure 18: Load Sense Program

Example: Figure 18 shows the Program 5 form of the PC Interface. The Delta Pressure Source isset to the Delta Pressure Preset Value of 10% (menu 444=0 and menu 441=10). The PressurePoint 2 Source is Analog Input 1 (menu 443=1), therefore the command is 2383 + 204 = 2587(all displays values are in DAC counts, refer to Section 5.1 for a discussion of the DiagnosticRepresentation of Numbers).

The Pressure Limit Source is set to the Pressure Limit Preset Value of 50% (menu 445=0 andmenu 442=50). In this case, the previous command value is not limited, since the command(2587) is less than the Pressure limit command (3071).

The error signal is produced by comparing the Command to the Pressure Point 1 signals: 2587 -2501 = 86. The Yi and Yp signals are produced from the PI controller and the Program Output isroughly equal to their sum: 2109 + 69 = 2178. The Program Output is set to the Pump Controller(menu 447=0)

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4.2.6 Simple Flow Control Programs (46x, 47x)Menu Item Range Description460 0 to 100 Program 7: Flow Command Preset461 0 to 5 Program 7: Flow Command Source464 0 to 1 Program 7: Program Output Destination

470 0 to 100 Program 8: Flow Command Preset471 0 to 5 Program 8: Flow Command Source474 0 to 1 Program 8: Program Output Destination

Table 7: Simple Flow Programs Configuration

Function Programs 7 and 8 provide for Simple Flow Control. Program 7 is configured in menuitems 460 through 464 or from the Program 7 form of the PC Interface. Program 8 is configuredin menu items 470 through 474 or from the Program 8 form of the PC Interface.

Flow Command Preset: The Flow Command Preset allows for direct numeric input for thecontrol program. The preset is configured as a percentage, with 0% being equivalent to a 0VDCinput signal and 100% being equivalent to a +10VDC signal.

Flow Command Source: The Flow Command Source selects the source of the flow commandfor the program. Valid entries are (0) Preset Value, (1) Analog Input 1, (2) Analog Input 2, (3)LVDT 1 (Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1. If the Preset Value ischosen, the Flow Command Preset is used as the flow command.

Program Output Destination: The Program Output Destination selects the output of theprogram. Valid entries are (0) Pump Controller or (1) Direct. If the Pump Controller is chosen,the output of the Program will be the input to the Pump Controller module. If Direct is chosen,the output of the Program will by-pass the Pump Controller module and passed directly to theservo driver. Under most circumstances, the Pump Controller should be chosen as the outputdestination.

Program Overview: The Simple Flow Control Program is by far the least complex controlalgorithm. In fact in does little more than transfer an analog or fixed input directly to the PumpController.

Figure 19: Simple Flow Program

Example: Figure 19 shows the Program 7 form of the PC Interface. The Flow Command Sourceis Analog Input 1 (menu 461=1). The Flow Command Preset is set to 12% (menu 460=12)although the preset is not used in this example. The Program Output is set to the PumpController (menu 464=0).

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4.2.7 Advanced Flow with Pressure Limit Programs (48x, 49x)

Currently, the Advanced Flow with Pressure Limit Programs are identical to the previouslymentioned Flow with Pressure Limit Programs (refer to Section 4.2.4).

4.3 Pump Controller Configuration

4.3.1 Overview

The Pump Controller provides the basic functionality of the module: to provide closed loopstroke feedback control for the servo valve. In addition to stroke feedback, the Pump Controllermodule can be configured for horsepower limitation.

Under usual circumstances, the pre-defined programs are used as outer loop control while thePump Controller provides inner loop control. The output of the pre-defined programs is verynearly always passed through to the Pump Controller module (refer to Section 4.2.1 for anoverview of the pre-defined Program modules).

4.3.2 ConfigurationMenu Item Range Description800 0 to 5 Pump Controller and HP Limiter:

Stroke Feedback Source801 0 to 100 Pump Controller:

Function Zero Stroke Command802 0 to 1 Pump Controller: Output Polarity803 15 to 100 Pump Controller: Output Current Limit804 0 to 100 Pump Controller: KP805 0 to 100 Pump Controller: KI

810 0 to 100 HP Limiter: Reference811 0 to 5 HP Limiter: Pressure Feedback Source812 HP Limiter: Spare813 0 to 100 HP Limiter: KP814 0 to 100 HP Limiter: KI

Table 8: Pump Controller Configuration

4.3.2.1 Function Zero Stroke Command

Normally, the Active Program Block provides the command to the Pump Controller. Forcertain applications, it might be desirable to have the ability to switch between two functionprograms, and the EPC provides that feature by allowing two program blocks selectable bythe digital input.

In some circumstances, a second program is not needed but some type of state is desired. Aprime example would be a stand-by mode in which a fixed stroke would be commanded. In

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this circumstance, the user could place a pre-defined program in block 1 and select program 0for block 2 (please refer to Section 4.1.3 regarding Program Block Configuration (21x)).

The Function Zero Stroke Command is configured by menu item 801 or from the PumpController form of the PC interface. It is expressed as a value from 0 to 100%, where 0equals full negative current, 100 equals full positive current, and 50 represents neutral or nocurrent. A Function Zero Stroke Command of 75, for instance, would provide a 50% strokecommand to the valve.

4.3.2.2 Stroke Controller

The Stroke Controller portion of the Pump Controller is configured by selecting a StrokeFeedback Source (menu item 800) and setting values for KP (menu 804) and KI (menu 805)for the Stroke PI Controller. These values can be optimal adjusted from the Pump Controllerform of the PC Interface.

Stroke Feedback Device: The Stroke Feedback Device determines which signal thecommand to the Stroke Controller is compared to. Valid entries are (0) Open Loop, (1)Analog Input 1, (2) Analog Input 2, (3) LVDT 1 (Analog Input 3), (4) LVDT 2 (Analog Input4), or (5) Ramp 1. If Open Loop is chosen, the stroke controller is disabled and the commandis passed directly through to the output.

KP and KI : KP and KI provide the proportional and integral constants, respectively, for thePI control algorithm. Both terms are expressed as 0 to 100% of a maximum value. The PIcontrol loop can be made a P-only control loop by setting the KI term to 0. Likewise, the PIcontrol loop can be made an I-only control loop by setting the KP term to 0.

The command to the stroke controller is from either the Active Program or the Function ZeroStroke Command (or by the HP-limited adjustment of this command, please refer to Section4.3.2.3). An error signal is produced by comparison of this command to the stroke feedbacksignal. The PI loop produces Yp and Yi, determined by the error signal and the KP and KIconstants, respectively. The stroke controller output is made by the summation of Yp and Yi.The Stroke Controller is disabled if the Stroke Feedback Source (menu item 800) is selectedas 0 (Open Loop).

The Pump controller relies on the stroke feedback device being configured correctly. Pleaserefer to Section 4.6.1 regarding the LVDT Adjustment Algorithm.

4.3.2.3 HP Limiter

The HP Limiter can be configured to limit the command to the stroke controller (refer toSection 4.3.2.2). This portion of the Pump Controller is configured by selecting a StrokeFeedback Source (menu item 800), Pressure Feedback Device (menu item 811) and settingvalues for KP (menu 813) and KI (menu 814) for the HP Limiter PI Controller. Additionally,a HP Limit Factor (menu item 810) must be entered (please refer to Section 4.6.2 regardingthe HP Limit Factor Calculation). These values can be optimal adjusted from the PumpController form of the PC Interface.

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Stroke Feedback Source: The Stroke Feedback Source determines which stroke signal isused in the HP calculation (this is the same stroke feedback used in the Stroke Controller,refer to Section 4.3.2.2). Valid entries are (0) Open Loop, (1) Analog Input 1, (2) AnalogInput 2, (3) LVDT 1 (Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp 1. If OpenLoop is chosen, the stroke controller is inactive, but the HP Limiter can be active, as long asa Pressure Feedback Source is configured. In this case, the module uses the pump controllercommand as the stroke feedback.

Pressure Feedback Source: The Pressure Feedback Source determines which pressuresignal is used in the HP calculation. Valid entries are (0) No HP Limit, (1) Analog Input 1,(2) Analog Input 2, (3) LVDT 1 (Analog Input 3), (4) LVDT 2 (Analog Input 4), or (5) Ramp1. If No HP Limit is chosen, the HP Limiter is inactive and the pump controller commandwill be passed directly to the stroke controller.

KP and KI : KP and KI provide the proportional and integral constants, respectively, for thePI control algorithm. Both terms are expressed as 0 to 100% of a maximum value. The PIcontrol loop can be made a P-only control loop by setting the KI term to 0. Likewise, the PIcontrol loop can be made an I-only control loop by setting the KP term to 0.

The product of Pressure and Stroke signals is compared to the HP Limit Factor (menu item810). If the product is greater than the factor, the feedback HP is greater than the allowedHP, and the pump controller command is adjusted through the Yp and Yi contributions of theHP Limiter PI controller. The HP Limiter works only as a limiter; the pump controllercommand is not manipulated if the HP Limit Factor is greater than the calculated HP.

The HP Limiter relies on the HP Limit Factor being configured correctly. Please refer toSection 4.6.2 regarding the HP Limit Factor Calculation.

4.3.2.4 Output Polarity

Module Polarity is selected from menu item 802 or from the Pump Controller form of the PCInterface. Polarity is either Normal (menu 802=0) or Inverted (menu 802=1).

4.3.2.5 Output Current Limit

The Module can be current limited to protect the valve or limit stroke. The current limit isselected from menu item 803 or from the Pump Controller form of the PC Interface and isexpressed as 0 to 100% of the maximum current of the module (200 or 250mA, depending onthe part number).

Current is limited in each direction, so a Current Limit of 50% will limit the current to -50%to +50% of the maximum.

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4.3.3 Configuration Example

Figure 20: Pump Controller Configuration

Figure 20 shows the PC Interface Diagnostic Screen for the Pump Controller Module. TheDiagnostic screen shows that Program 3 is active and passes the command of 3071 to the PumpController (all display values are in DAC counts, refer to Section 5.1 for a discussion of theDiagnostic Representation of Numbers). The Function Zero Stroke is set to 50% (menu 801=50),so if no program was active a neutral stroke would be the Pump Controller command signal.

The Pressure Feedback Source is Analog Input 1 (menu 811=1) and the Stroke Feedback Sourceis LVDT 1 (menu 800=3). The internal HP calculation based on these pressure and stroke signalsresults in a value of 671. The HP Limit Factor of 28% results in a value of 574 DAC counts, sothe actual HP is greater than the allowed HP. The error signal is the difference of thesecalculated numbers (574 - 671 = -97) and the HP Limit is made up of the Yi and Yp contributionscomputed from the HP Limiter PI controller.

The resulting Command with HP Limit is 3071 - 100 = 2971 DAC counts. This command, alongwith the Stroke Feedback signal is passed to the Stroke Controller, where the error signal is 2971- 3013 = -42. This error signal is used for the Stroke Controller PI calculations, and the output isequal to the Yi and Yp contributions (1843 - 667 = 1176).

Menu 802 is set to Invert the module output (menu 202=1) so the 1176 signal becomes 2918.Finally, the current is limited to 15% of maximum, so the 2918 signal becomes 2367.

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4.4 Analog IO Configuration

The EPC module provides four analog inputs: Analog Inputs 1 and 2 are referred to as GeneralPurpose Analog Inputs and have a maximum input range of -10VDC to +10VDC.

Analog Inputs 3 and 4 are usually referred to as LVDT Input 1 and 2, respectively. These inputs areintended for sinusoidal LVDT input.

4.4.1 General Purpose Analog Input ConfigurationMenu Item Range Description850 0 to 200 Analog Input 1: Offset851 1 to 32 Analog Input 1: Gain852 0 to 1 Analog Input 1: Polarity853 0 to 1 Analog Input 1: Current Fault Enable

860 0 to 200 Analog Input 2: Offset861 1 to 32 Analog Input 2: Gain862 0 to 1 Analog Input 2: Polarity863 0 to 1 Analog Input 2: Current Fault Enable

Table 9: General Purpose Analog Input Configuration

Menu items 850 through 853 are used to configure Analog Input 1 while menu items 860 through863 are used to configure Analog Input 2. Optimally, the Analog Inputs can be configured fromthe Analog Input Configuration Form (select menu Diagnostics and then Configuration) of thePC Interface.

Offset: A voltage offset can be applied to the Analog Input. The voltage offset can be in therange of -10VDC to +10VDC at 0.1VDC increments. The PC interface allows for the directentry of a voltage offset, while valid menu entries are from 0 to 200 using the following equation:

1.0

] (Volts)Offset Voltage [100] ENTRY MENU [ +=

Reversing the equation, the offset voltage can be determined from the menu item by the equation:

( ) 1.0100- ] ENTRY MENU [ (Volts)Offset Voltage ×=The resulting offset voltage is limited to the -10VDC to +10VDC range.

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Gain: A limited gain factor can be applied to the Analog Input. Values in the range of a 0.125attenuation to a ×4 gain at 0.125 increments are available. The PC interface allows for the directentry of a gain, while the following table may be used to configure the module directly throughthe display menu.

Menu Menu Menu MenuEntry Gain Entry Gain Entry Gain Entry Gain1 0.125 9 1.125 17 2.125 25 3.1252 0.250 10 1.250 18 2.250 26 3.2503 0.375 11 1.375 19 2.375 27 3.3754 0.500 12 1.500 20 2.500 28 3.5005 0.625 13 1.625 21 2.625 29 3.6256 0.750 14 1.750 22 2.750 30 3.7507 0.875 15 1.875 23 2.875 31 3.8758 1.000 16 2.000 24 3.000 32 4.000

Table 10: Analog Input Gain Settings

The resulting voltage is limited to the -10VDC to +10VDC range.

Polarity : The Polarity setting is set to either Normal (0) or Inverted (1). Inverting the input inthis way would be equivalent to reversing wire leads to the module. In fact, a better long termsolution to using the invert setting would be to reverse the wire leads to the module.

Current Fault Enable: The Current Fault is set to either Disabled (0) or Enabled (1) and isdesigned for use when a 4-to-20mA input device is used. The EPC module has DIP switches thatcan be set to place a 500Ω resistor in parallel to the analog input terminal pins (refer to Section6.2 regarding Test Point, DIP-Switch, and Pot Settings). If used, a 4-to-20mA input device willresult in a voltage from +2VDC (4mA) to +10VDC (20mA) to the module. If the Current Faultis enabled, the module will set a System Message if this voltage falls below +1.5VDC(approximately 3mA).

The four configuration settings are used together to configure the general purpose analog inputs.The order of monitoring/configuration is:

(1) A Fault is reported if the Current Mode Fault is enabled and the current supplied to themodule falls below 3mA.

(2) Offset Voltage by Offset Setting.(3) Multiply Voltage by Gain Setting.(4) Invert Analog Input (if Polarity Invert set).

Example 1: A user wants a 4-20mA signal at Analog Input 1 to control a bi-directional pump(command range of +/- 10VDC).

First the user would enable the current fault for Analog Input 1 (menu 853=1) and place theADC1 I/U DIP switch to the I (Current) setting (refer to Section 6.2). This will create a +2VDCto +10VDC voltage at the terminals and generate a fault if the voltage drops below 1.5VDC (3mA).

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Second, the user would set the Analog Input Offset to generate a –6VDC offset. This creates a –4VDC to +4VDC voltage from the original +2VDC to +10VDC voltage. The user would set thisdirectly if using the PC interface. If entered through the on-board keypad and display, the userwould convert the offset voltage to the menu entry value:

40

-601001.0

6.0-100

1.0

] (Volts)Offset Voltage [100] 850 [

=+=

+=

+=

Next, the user would set the gain to 2.5. This creates a –10VDC to +10VDC voltage from theoffset voltage of –4VDC to +4VDC. If using the PC interface, the user selects 2.500 from thelist. If entered from the menu, the user sets menu 851 to the setting from Table 10. In this case,a menu entry of 20 corresponds to a 2.500 gain.

Finally, the user would set the input polarity to normal (menu 852=0), so the input is notinverted.

Example 2: A user wants a 0-5VDC signal at Analog Input 1 to control a unidirectional pump(command range of 0 to +10VDC).

First the user would disable the current fault for Analog Input 1 (menu 853=0) and place theADC1 I/U DIP switch to the U (Voltage) setting (refer to Section 6.2).

Second, the user would configure the input for 0VDC voltage offset since the input voltage needsno offset for this particular example. The offset is entered directly through the PC interface, orthe menu entry is determined from the equation:

100

01001.0

0100

1.0

] (Volts)Offset Voltage [100] 850 [

=+=

+=

+=

Next, the user would set the gain to 2 to create a 0 to +10VDC voltage from the offset voltage of0 to +5VDC. If using the PC interface, the user selects 2.000 from the list. If entered from themenu, the user sets menu 851 to the setting from Table 10. In this case, a menu entry of 16corresponds to a 2.000 gain.

Finally, the user would set the input polarity to normal (menu 852=0), so the input is notinverted.

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4.4.2 LVDT/DCDT Fine-Adjustable Analog Input ConfigurationMenu Item Range Description830 0 to 63 LVDT 1: Course Gain831 0 to 63 LVDT 1: Fine Gain832 0 to 1023 LVDT 1: Offset833 0 to 3 LVDT 1: Offset (High Byte) For PC Interface

Menu Entry should not be Changed directly834 0 to 255 LVDT 1: Offset (Low Byte) For PC Interface

Menu Entry should not be Changed directly835 0 to 1 LVDT 1: Polarity

839 0 to 1 Pump Controller Adjustment Mode

840 0 to 63 LVDT 2: Course Gain841 0 to 63 LVDT 2: Fine Gain842 0 to 1023 LVDT 2: Offset843 0 to 3 LVDT 2: Offset (High Byte) For PC Interface

Menu Entry should not be Changed directly844 0 to 255 LVDT 2: Offset (Low Byte) For PC Interface

Menu Entry should not be Changed directly845 0 to 1 LVDT 2: Polarity

849 SpareTable 11: LVDT/DCDT Input Configuration

Menu items 830 through 835 are used to configure LVDT 1 while menu items 840 through 845are used to configure LVDT 2. Optimally, the LVDT Inputs can be configured from the AnalogInput Configuration Form (select menu Diagnostics and then Configuration) of the PC Interface.

Menu item 839 allows the module to be placed in Pump Controller Adjust Mode . This is aspecial operating mode designed for adjustment of the LVDT inputs. Please refer to Section4.6.1 for a thorough discussion of this adjustment mode.

Course and Fine Gains: Since greater resolution is needed to scale and offset the input of thesinusoidal LVDT input signals, the gain and offset are not done directly in the microcontroller,but performed through electrical circuitry. Typically the Course Gain increases over the range of0 to 63 and the Fine Gain decreases over the range of 0 to 63. The LVDT or DCDT should beconfigured using the algorithm discussed in Section 4.6.1.

Offset: The LVDT offset, like the course and fine gains, manipulates hardware circuitry. Anoffset signal ranges from 0 to 1023. Note that the menu contains entries that are only used inconjunction with the PC interface and should not be manipulated directly by the user. Pleaserefer to Section 4.6.1 for a discussion of the LVDT Adjustment Algorithm.

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Polarity : The Polarity setting is set to either Normal (0) or Inverted (1). Inverting the input inthis way would be equivalent to reversing wire leads to the module. In fact, a better long termsolution to using the invert setting would be to reverse the wire leads to the module.

4.5 Ramp ConfigurationMenu Item Range Description870 0 to 4 Ramp 1: Source871 1 to 255 Ramp 1: Acceleration Rate872 1 to 255 Ramp 1: Acceleration Step873 1 to 255 Ramp 1: Deceleration Rate874 1 to 255 Ramp 1: Deceleration Step

Table 12: Ramp Configuration

The EPC module provides one ramp module and is configured by menu items 870 through 874.Optimally, the ramp can be configured from the Advanced Configuration form (select Diagnosticsand then Advanced) of the PC Interface.

Source: The Source selects the Analog Input used as the ramp input. Valid entries are No Ramp (0),(1) Analog Input 1, (2) Analog Input 2, (3) LVDT 1 (Analog Input 3), or (4) LVDT 2 (Analog Input4). If No Ramp is selected, the ramp module will be disabled and the ramp function will be equal to2048 DAC counts.

Rate and Step: The Ramp module provides different ramping rates for acceleration and deceleration.Acceleration is defined as increasing stroke, while Deceleration is defined as decreasing stroke.Ramping from +5V to +10V is acceleration, while ramping from +10V to +5V is deceleration.Ramping from -5V to -10V is also acceleration, since -10V provides greater stroke than -5V.Conversely, ramping from -10V to -5V is deceleration.

Since the EPC is a digital controller, the ramp is actually a staircase-like signal. The Rate describesthe time length of each step and is expressed in whole number multiples of the closed loop updaterate. The Step describes the potential step at each interval and is expressed as DAC counts.

Depending on the module, the closed loop response is either 1600 Hz or 1200 Hz. The Ramp Ratecan be expressed in Volts/second with the equation

Rate

Step××= 004884.0] Response Loop Closed [(Volts/s) Rate Ramp

The larger the ramp rate or step is, the more course the ramp stair casing will be. The time length ofeach step can be computed from the Rate setting:

] Response Loop Closed [(seconds)Length Time

Rate=

The Potential Step can be computed from the Step setting:

004884.0(Volts) Step Potential ×= Step

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Example 1: A Rate of 255 and a Step of 1 is used for a 1600 Hz module. The Ramp Rate in Volts/second is

Ramp Rate = 1600 × 0.004884 × (1 / 255) = 0.03064 Volts/secondso a 10 Volt step would ramp over a period of 326 seconds (5 minutes:26 seconds).

The same rate and step for a 1200 Hz module results in a rampRamp Rate = 1200 × 0.004884 × (1 / 255 = 0.02298 Volts/secondso a 10 Volt step would ramp over a period of 435 seconds (7 minutes:15 seconds).

The setting of Rate = 255 and Step = 1 results in the slowest ramping rate.

Example 2: A Rate of 1 and a Step of 255 is used for a 1600 Hz module. The Ramp Rate in Volts/second is

Ramp Rate = 1600 × 0.004884 × (255 / 1) = 1993 Volts/secondso a 10 Volt step would ramp in only 5 milliseconds.

The same rate and step for a 1200 Hz module results in a rampRamp Rate = 1200 × 0.004884 × (255 / 1) = 1495 Volts/secondso a 10 Volt step would ramp in only 7 milliseconds.

The setting of Rate = 1 and Step = 255 results in the quickest ramping rate.

A user should select a ramp rate that is close to a desired value, while not producing an undesirablestep. Generally, the lower the values for rate and step, the smaller the step.

Example 3: Which of the following are the optimal settings for a 0.5 Volt/second ramp?(a) Rate = 15, Step = 1(b) Rate = 31, Step = 2(c) Rate = 47, Step = 3(d) Rate = 125, Step = 8

Assuming a 1600 Hz closed loop response, the settings for (a) result in:Ramp Rate = 1600 × 0.004884 × (1 / 15) = 0.5210 Volts/secondor a 1 × 0.004884 = 5mV step every 15/1600 = 9 milliseconds.

Similarly, the settings for (b), (c), and (d) result in(b) Ramp Rate = 0.5042 Volts/second (10mV step every 19 milliseconds)(c) Ramp Rate = 0.4988 Volts/second (15mV step every 29 milliseconds)(d) Ramp Rate = 0.5001 Volts/second (39mV step every 78 milliseconds)

The optimal setting depends on the ramp requirements and system dynamics. If time is not critical,the settings for (a) which have the smallest step size would be optimal. If time is critical and thesystem dynamics allow for a larger step size, the settings in (d) should be used since the ramping iscloser to the desired value (0.5001 V/s rather than 0.5210 V/s).

Deductive reasoning can be used to find the rate and step values for a desired ramp.

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Example 4: What settings would be used to produce a 5-second ramp for a 0 to 10 Volt stepcommand?

A 10 Volt / 5 second = 2 Volt/second ramp is desired. Since both the Rate and Step have values from1 to 255, an arbitrary value of 10 is chosen for the Step and the Rate value is calculated:

Ramp Rate = [ Closed Loop Response ] × 0.004884 × Step / RateRate = [ Closed Loop Response ] × 0.004884 × Step / [Ramp Rate]

= 1600 × 0.004884 × ( 10 / 2 ) = 39

A step of 10 and rate of 39 make a 2.0037 Volt/second ramp (48 mV step every 24 milliseconds).Because 10/39 is approximately 1/4, we would expect a step of 1 and a rate of 4 to be close to theramp rate, yet provide a smaller staircase. Accordingly, a step of 1 and a rate of 4 create a 1.95 Volt/second ramp, this time with a 5 mV step every 0.6 milliseconds.

PC Interface: The PC interface contains a worksheet for ramp values (Advanced Diagnostics form).The user selects a desired ramp rate and one of five resolution factors. The worksheet calculationfunction will display the results of the most optimal settings.

4.6 Advanced Configuration

4.6.1 LVDT Adjustment Algorithm

Both the HP Limiter and Stroke Controller portions of the Pump Controller module rely on theLVDT being configured correctly. Typically, there are three (4) configuration parameters foreach LVDT (Refer to Section 4.4.2 for a complete overview):n Polarityn Offsetn Course Gainn Fine Gain

The general sequence of operations for LVDT scaling is ton Set LVDT polarity to normal. The LVDT polarity toggle is intended for short-term

diagnostics. The long-term solution to the LVDT inversion is to swap wire leads into thecontroller (refer to Section 4.4.2).

n Place the EPC in Adjust mode.n Alternately Adjust the LVDT Offset and Gains until configured.n Return EPC to normal operation mode.

4.6.1.1 Adjustment Mode

The Pump Controller Adjustment Mode is a special operation mode in which a Togglecommand controls the servo driver output rather than the Pump Controller or Active functionblock.

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The Adjustment mode works optimally with Main pumps off and Pilot Pumps pressurized.Adjustment mode is set by setting menu item 839 to 1, or by pressing the Adjust Modecommand button from the Analog Input Configuration form of the PC interface.

Adjust mode is indicated by the PC interface noting a system message and by the LCDDisplay on the front panel of the module turning red.

The Adjust Mode Command Toggle is a special function available in Adjustment mode thatwill alternately command full negative, neutral, and full positive current to the driver. If inAdjustment mode, the menu items for LVDT adjustment (refer to Section 4.4.2) will show agraphic representation of the current toggle in the upper right corner of the menu display.

The menu and graphic will appear as in Figure 21 when the toggle is at maximum positivecurrent:

Figure 21

The menu and graphic will appear as in Figure 22 when the toggle is at neutral (zero) current:

Figure 22

Finally, the menu and graphic will appear as in Figure 23 when the toggle is at maximumnegative current:

Figure 23

Initially, the output toggle is at the neutral (zero) current position. The toggle can be changedthrough the front keypad and display by pressing the right cursor arrow key while in therightmost position of the menu value for one of the LVDT adjustment items. For example,pressing the right cursor key for the display:

Figure 24

will toggle the Adjustment command from neutral to full positive current:

Figure 25

If the user presses the right cursor key again, the Adjustment command will change from fullpositive to full negative current:

Figure 26

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The Adjustment toggle command can be monitored from the PC interface as well. TheConfiguration form of the PC interface has a toggle command button. The display and bargraph indicator will show the value of the toggle.

The PC interface admittedly makes the LVDT configuration easier to work with thanworking directly with the front keypad and display

4.6.1.2 Determining LVDT Configuration Range

The LVDT input should be scaled to match the range of stroke command. The range ofstroke command is a factor of whether the pump is designed for uni- or bi-directional flow.

Servo valves are commanded with current: a positive current command will move the valvein one direction while a negative current command will move the valve in the oppositedirection. A neutral (zero) current command will remove command to the valve: the valvemight stay in its current state, or it may move in either direction.

For a uni-directional pump, only one port is available and the stroke can supply 0 to 100%of the rated flow. The LVDT should be configured so that the maximum positive togglecommand will produce the equivalent of a +10VDC command for the LVDT input. Themaximum negative toggle command should produce the equivalent of a 0 VDC command atthe LVDT input. The range of 0 to +10VDC corresponds to DAC values of 2048 to 4095, ora percentage of 0 to +100% (refer to Section 5.1 for a discussion of the DiagnosticRepresentation of Numbers).

For a uni-directional pump, the midpoint command is +5VDC (DAC value of 3072 or +50%stroke).

For a bi-directional pump, two ports are available and the stroke can supply 0 to 100% ofrated flow in each direction. Like the uni-directional valve, the LVDT should be configuredso that the maximum positive toggle command will produce the equivalent of a +10VDCcommand for the LVDT input. The maximum negative toggle command, however, shouldproduce the equivalent of a -10VDC command for the LVDT input. The range of -10VDC to+10VDC corresponds to DAC values of 0 to 4095, or a percentage of -100% to +100% (referto Section 5.1 for a discussion of the Diagnostic Representation of Numbers).

For a bi-directional pump, the midpoint command is 0VDC (DAC value of 2048 or 0%stroke).

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4.6.1.3 Adjustment Algorithm

The following algorithm may be used to optimally configure the unit. The PC Interfaceincludes a Microsoft Excel ™ template (EPCConfig.xlt) that can be used to optimize thesetup. The Excel template is also available through e-mail by request [email protected].

1. Place the module in Adjustment mode (refer to Section 4.6.1.1).2. Use an Initial setting of Offset = 512, Course Gain = 0, and Fine Gain = 63.3. Toggle the Pump Command and note the LVDT readings at the maximum positive

and negative toggle commands (refer to Section 4.6.1.1 regarding toggle command).4. Determine the midpoint of these two LVDT readings and compare with the desired

midpoint reading (see previous Section).5. Adjust the LVDT offset so that the two LVDT readings have the desired midpoint

reading.6. Adjust the LVDT course gain upwards from the initial setting such that the positive

and negative toggle commands produce LVDT signals as large as possible withouteither toggle command producing an LVDT signal out of the LVDT configurationrange..

7. Repeat steps 3 through 6 until a one-digit course gain change is unable to produceLVDT signals within the configuration range. For a uni-directional pump, a positivetoggle command should produce an LVDT signal slightly less than +10VDC and anegative toggle command should produce an LVDT signal slightly greater than0VDC. For a bi-directional pump, a positive toggle command should produce anLVDT signal slightly less than +10VDC and a negative toggle command shouldproduce an LVDT signal slightly greater than -10VDC.

8. Once the Course gain is found, adjust the fine gain downward from the initial setup.Do not adjust the course gain and fine gain concurrently since the two do notfunction together in a straightforward linear fashion. Also note that while increasingthe value of the course gain increases the overall LVDT signal gain, the fine gainworks in the reverse direction.

9. Determine the midpoint of these two LVDT readings and compare with the desiredmidpoint reading (see previous Section).

10. Adjust the LVDT offset so that the two LVDT readings have the desired midpointreading.

11. Adjust the LVDT fine gain downward from the initial setting until one of the twopump toggle commands is just under the pump range.

12. Repeat steps 9 through 11 until a one digit fine gain change produces LVDT signalsspanning the entire configuration range. For a uni-directional pump, a positivetoggle command should produce an LVDT signal of +10VDC and a negative togglecommand should produce an LVDT signal of 0VDC. For a bi-directional pump, apositive toggle command should produce an LVDT signal of +10VDC and a negativetoggle command should produce an LVDT signal of -10VDC.

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Example 1: Balance an LVDT for a bi-directional pump (The example can be followed fromthe Example 1 sheet of the Excel template.)

Toggling with the initial values produces a low reading of -92.50% and a high reading of -40.60%. These readings should be offset to produce a low reading of -25.95% and a highreading of +25.95%. This is calculated by finding the midpoint of the current readings (-90.50 + -40.60)/2 = -66.55 and comparing that to the desired midpoint (a bi-directional pumpshould have a midpoint at 0). Adding 65.55 to each value results in -90.50 + 65.55 = -25.92and -40.60 + 66.55 = 25.95. This setting is reached when the Balance is set to 411 (low andhigh readings of 25.90 and 26.20, respectively). Notice that at this point approximate valuesare good enough.

The user then attempts to adjust the gain to near saturation. At a Course gain = 30 the lowreading is -91.60% while the high reading is -9.20%. The next gain (31) actually saturatesthe low reading to -100%, so 30 is used.

The user then attempts to offset the readings to low=-41.20% and high=+41.20%. The userfinds this at Offset=334.

In a similar fashion, the user continues alternately selecting offset and course gain values. Atstep 6, a change in course gain saturates the low reading, so the user has successfully foundthe optimal setting for course gain. The user continues as before, but this time uses the finegain to set the near saturation gains.

At step seven the user finds that a fine gain change from 45 to 46 saturates both readings.LVDT configuration is complete.

Example 2: Balance an LVDT for a unit-directional pump. The only difference between this andthe previous example would be that the midpoint would be +50% rather than 0%. The user isinvited to view the Example 2 sheet of the Excel template for this example.

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4.6.2 HP Limit Factor Calculation

Figure 27: PQ (HP) Limit Curve

The horsepower limit factor can be used to limit the power consumed by the hydraulic pump. Tolimit horsepower, the user first enters a value for the HP factor: this factor produces a PQ(pressure-flow) curve that defines a certain horsepower region (Figure 27). The user then sets thePump Controller module with the proper settings for stroke and pressure feedback (see Section4.3.2.3).

The horsepower limit factor can be determined in two ways: experimentally or theoretically.

4.6.2.1 Experimental HP Limit Factor

For the Experimental HP Limit Factor, the user builds up pressure and increases stroke untilthe motor supplies the maximum rated current. This procedure requires a program thatallows for direct stroke command, so a good function program to use would be the SimpleFlow Program (refer to Section 4.2.6).

To determine the HP Limit Factor, the user must first configure the EPC for stroke feedback(Section 4.4.2) and connect a pressure transducer to an available analog input. An additionalanalog input can be used for stroke command.

The user then sets the HP factor to an initial setting of 100% and rigs the hydraulic circuit tobuild maximum pressure. Once this achieved, the user uses a current transducer and

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multimeter to measure motor current. Stroke to the pump is slowly increased, and themultimeter is monitored until the current to the motor is at the maximum rated current. Atthis point, the user notes the DAC reading for pressure and stroke.

The HP factor is determined by the formula:

( )( )( )( ) %10020462048

20482048 ×−−= DACDACfactorPQ

HP

The PC interface allows a one-touch solution from the Advanced Configuration form. Theuser simply presses the HP Experiment pushbutton once the maximum current is reached.

4.6.2.2 Theoretical HP Limit Factor

The HP limit factor can also be determined by the theoretical formulas. For metric units thehorsepower factor is determined by the equation:

η×××=NPD

PowerHP

XDCRMAXfactor

7100.6

wherePower is the motor rating in kWD

MAX is the maximum displacement of the Pump in ml/rev

PXDCR

is the maximum measured pressure in Bars(i.e., the pressure corresponding to a 10VDC or 20mA reading)

N is the speed in rpmand η is the pump efficiency

The user may also use conventional English units:

η×××=NPD

PowerHP

XDCRMAXfactor

7100.4

wherePower is the motor rating in horsepowerD

MAX is the maximum displacement of the Pump in in3/rev

PXDCR

is the maximum measured pressure in PSI(i.e., the pressure corresponding to a 10VDC or 20mA reading)

N is the speed in rpmand η is the pump efficiency

Example 1: What HP factor would be used for a PVG075 powered by a 25 HP motorrotating at 1500 rpm. The EPC uses a 5000 PSI pressure transducer to measure pressure.

From Oilgear Bulletin 47019, a PVG075 has a maximum displacement of 4.60 in3/rev and anoverall efficiency of 80% at maximum pressure. These values are used in the formula:

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( )( )( )23

80.01500500060.4

25100.4

100.4

7

7

=

×××=

×××= ηNPD

PowerHP

XDCRMAXfactor

Example 2: What HP factor would be used for a PVG100 powered by a 50 kW motorrotating at 1500 rpm. The EPC uses a 400 Bar pressure transducer to measure pressure.

From Oilgear Bulletin 47019, a PVG100 has a maximum displacement of 98.3 ml/rev and anoverall efficiency of 85% at maximum pressure. These values are used in the formula:

( )( )( )43

85.015004003.98

50100.6

100.6

7

7

=

×××=

×××= ηNPD

PowerHP

XDCRMAXfactor

Once again the PC interface provides an easier method. From the Advanced Configurationform, the user enters each of the variables in the desired system of units. Once this is done,the use presses the HP Theory command button to create a new value for the HP factor.

5 Module Diagnostics

The EPC has diagnostics available through both the On-Board display/keypad and PC interface. Due tothe extensive features of the controller, however, the PC interface is the recommended setup anddiagnostic tool.

5.1 Diagnostic Representation of Numbers

Throughout this manual, reference has been made to DAC counts, percentages, and voltages. DACcount representation is the basis for all other diagnostic representation, since all internal numbers arerepresented within the controller as DAC (Digital-to-Analog Converter) counts.

5.1.1 DAC Counts

Most Diagnostic numbers are stored as a 12-Bit number from 0 to 4095. For an input or outputvariable, 0 DAC counts is equivalent to -10VDC while 4095 DAC counts is equivalent to+10VDC. 2048 DAC counts represents the midpoint of -10VDC

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ELECTRONIC 1 EPC - Oilgear · The EPC is a microcontroller-operated motion controller and amplifier for servo controlled pumps and valves. The unit can be configured for several