Stepper Motor Drive for High Speed Control

International Journal of Advanced Engineering Research and Studies E-ISSN2249–8974

IJAERS/Vol. I/ Issue III/April-June, 2012/178-180

Research Paper

STEPPER MOTOR DRIVE FOR HIGH SPEED CONTROL BY

HIGH VOLTAGE & CONSTANT CURRENT 1J G Gajipara,

2Prof K A Sonagara,

Address for Correspondence 1ME Electrical,

2Asst. Professor, Govt. Engg College, Bhuj, Gujarat, India

ABSTRACT In Today’s era with growing demand towards motion control applications which consist of stepper motor, where some of

application required the high speed and holding torque control to increase the production. Generally stepper motor dive are

not to design for high speed application. Here one topology is given how to achieve high speed as well as holding torque

control in hybrid stepper motor.

KEYWORDS HPM Drive, HPM High Speed, HPM holding torque

1. INTRODUCTION

IN this paper one topology is given to control high

speed and holding torque control Hybrid Stepper

Motor (HPM).Whenever we are using HPM as

motion control solution in the industry where

sequential process is going on, for such application if

we are going with high speed than we can increase

production by keeping that in mind this method is

given.

2. HIGH VOLTAGE SUPPLY FOR HPM HIGH

SPEED

It has been found that when the HPM start to rotate it

will develop the back emf stator winding. Fig. 1

shows the equivalent circuit for the HPM Drive. At

starting there is no back emf (Eb) so Current in the

winding flow SA1 and SA2 will Close which is given

by Eq. (1) for any random Sequence.

It= Im (1-e-t/τ) (1)

Where, Im= (Vdc/RA),

τ = LA/RA,

RA=Winding resistance of any one phase,

LA=Winding inductance of any one phase,

Vdc=supply voltage,

Im=Ir =Rated Current for rated torque.

Fig.1

Now HPM is on speed N1, so it has its back emf

say it Eb1,

Im= ((Vdc-Eb1)/R),

It = ((Vdc-Eb1)/R) X (1-e-t/τ) (2)

When HPM is at low speed value of back emf Eb is

not so much high, HPM do its work faith Fully but at

a high speed due to back emf, Im is Decrease and so

motor can take its rated load. Second thing at high

acceleration we face the slip of the rotor. In this way

if we want to go for higher speed or high

acceleration, we have to decrease load on motor. As

given in the fig.2 whenever we are applying DC

voltage to the winding current is rise exponentially

and gets stabilized. Now if we are working with low

voltage at 5V than charging current will like curve 1.

If winding insulation is capable to bare voltage stress

of 80 V to 100 V than by applying this higher voltage

gives fast rise in the current but problem is high

current at saturation. (Curve-2)

Fig.2

To limit the current we are using the fixed frequency

chopping. Now we are sensing the Current inside the

winding as it reached to its rated value we are just

disconnecting the supply and allowed current to free

wheeling. After fixed interval (fixed frequency) we

further switch on the supply. Current will start to rise

and wait up to when current will reached to its rated

value, at this point disconnect the supply. This

procedure will continue and we are main-tenting the

rated current in the winding. Thus higher voltage will

help to eliminate the problem of the back emf at high

speed and we can go for the higher speed. [1]

2.1 HOLDING TORQUE CONTROL

In some of the applications are present where control

of holding torque is required. HPM holding torque is

personal to the current in side the winding, so change

in current will cause the change in holding torque. To

sense the current inside the winding required fast

manipulations. If we are applying the fixed frequency

chopping for each winding having 20 KHz frequency

we have time span of 50µs. Now considering

microcontroller P18F452 we can convert DC voltage

drop in digital in 10 µs, so effectively we have only 3

chances 10-20, 20-30 and 30-40 µs in one cycle.

Now doing arrangement as given in Fig.3, we do

instantaneous current sensing. First we amplifying

the voltage drop cross the shunt resistor by help of

instrumentation amplifier than this voltage are being

compared with the reference voltage of the

comparator. Output of comparator is directly given to

the microcontroller. Here microcontroller will sense

the 0 & 1. If it sense ‘0’ than current inside the



winding is less than the required, for this condition

we allowed to raise the current. If it sense ‘1’ than

current inside the winding is grater than the required,

for this condition we just take out the supply and

allowed to fall in current by freewheeling. We are

energizing the winding only after completion of one

cycle (50 µs). Thus by changing the reference we can

change the holding torque. [2]

2.2GENERATION OF CONTROL SIGNALS

As given in to the fig.3 we can’t switch on two

switches of one lag at a same time because it will

create dead short-circuit on available DC link level.

Drivers are available in market which take one input

and generate two outputs have one inverted facility.

So we have to generate control signal A, B, C and D

which is going to control the SA1-SA4, SA3-SA2,

SB1-SB4 and SB3-SB2. Fig.4 shows the control

signal required to drivers A, B, C and D. They all are

work on fixed frequency. Table -1 shows the tabular

formte of the control signals.

Fig.3

Fig.4

2.3 Algorithm For Generation Of Control Signals

Main flow chart:

• Link the library files to MPLAB software.

• Declaring variables and arrays for the

program, declaring names of the I/O pins.

• Deciding which I/O pin work as input and

which pin work as output.

• Checking the status of the inputs and store

it.

• Set the mode of operation and direction by

status of inputs.

• Blink all LEDs indication for the 1s to check

the LEDs are working and drive is

configured.

• Wait for ENABLE pulse.

• After getting ENABLE first enable all

interrupts than start to continuously

monitoring the STOP input as an when

STOP come drive is reset the all variables.

Fig.5 (Main Flow Chart)

2.4 Interrupt flow chart:

1) We are using four interrupts INT0, INT1, INT2

and TIMER2 which are assign for work CLOCK

monitoring, winding 1 current is higher than the

rated, winding 2 current is higher than the rated and

to generate fixed frequency chopping. 2) Here this

microcontroller (P16F452) has two types of interrupt

service retinue address high priority and low priority.

3) We are keeping INT0, INT1, INT2 in high priority

and TIMER2 in low priority. 4) When a CLOCK

come, INT0 is generate program counter will move to

high priority address and next sequence of A, B, C

and D are generated. 5) When current inside the

winding 1 will goes higher than rated INT1 is

generated, first it will check output A is on (i.e.

A==1) if yes than A will switch off (i.e. A=0), if not

than will check output B is on (i.e. B==1) if yes than

B will switch off (i.e. B=0). 6) When current inside

the winding 2 will goes higher than rated INT2 is

generated, first it will check output C is on (i.e.

C==1) if yes than C will switch off (i.e. C=0), if not

than will check output D is on (i.e. D==1) if yes than

D will switch off (i.e. D=0). 7) When TIMER2 value

becomes 0000H, TIMER2 interrupt will generate, it

will load original value of outputs A, B, C and D.



Fig.6 (Interrupt routine)

3. CONCLUSION:

It has been found that fixed frequency chopping

method can used to control the high speed as well as

at high acceleration. Here drive can easily ableto

control the holding torque. This method is required to

sense the only o/p comparator so no need to go for A

to D conversion and so, this drive can easily develop

by the microcontroller (P16F452) only.

REFRENCES 1. V.V.Athani, “Stepper Motors

Fundamentals,Application and Design”, ch. 4, pp. 31-

65, NewAge International (P) Limited, New Delhi,

2000. 2. V.V.Athani, and J.C. Mundha, “High Performance

Controller for High Torque PM Stepping Motor”, IEEE

Trans. on Industrial Electronic. Vol. IECI-25, No. 4, pp.343-346, 1978.

3. Reston Condit, Dr. Douglas W. Jones, “Stepping

Motors Fundamentals” (AN907), pp. 10-14, Microchip, 2004

4. Crnosija, P.; Kuzmanovic, B.; Ajdukovic, S. ,

“Microcomputer implementation of optimal algorithms for closed-loop control of hybrid stepper motor drive”,

IEEE Transactions on Industrial Electronics, Volume

47, Issue 6, pp. 1319 – 132, Dec 2000. 5. M.H. Rasid, “Power Electronics, Circuits, Devices and

Applications”, ch. 9, pp. 406-430, Prentice-Hall, India,

2007

Documents

Stepper Motor Drive for High Speed Control