LabVIEW Simulation Module

National Instruments Confidential

LabVIEW Simulation Module

National Instruments Confidential 2

LabVIEW Simulation Module• Simulate dynamic systems including controllers & plants• Real-time implementation for rapid control prototyping or hardware-in-the-loop

simulation


LabVIEW Simulation Module Benefits• Complete simulation and real-time implementation capability -

stay in one environment from design to test to implementation• LabVIEW user interface to change and observe parameters as

simulation or control system is running• Use any LabVIEW VI or programming structure inside or outside of

simulation loops:– Integrated design and simulation, batch simulation– DAQ, RIO, Vision, or CAN for I/O and feedback

• Easily create parallel and multirate simulation or control loops


LabVIEW Simulation Module Overview

• Linear systems – continuous and discrete time

• Nonlinear systems blocks and lookup tables

• Signal generation and graphing• Fixed-step, variable step, and stiff

solvers• Trimming and linearization• Model hierarchy• Integration with Formula node and

MathScript node (through subVI)• Integration with 3D picture control for

system visualization


Hardware Options for LV Sim

• Offline simulation – desktop computers• Real-time simulation and control:

– PXI– Desktop computers– CompactRIO– Compact FieldPoint– Single board computers (SBC)– 32 bit processors w/ LV Embedded (pioneer stage)


Little or No Learning Curve for The Mathworks, Inc. Simulink® Software Users

• LabVIEW Simulation Module

• The Simulink® software environment

Simulink® is a registered trademark of The MathWorks, Inc.


LabVIEW is the original …Little or No Learning Curve for The MathWorks, Inc. Simulink® Software Users

The Simulink® software environment

LabVIEW Simulation Module


LabVIEW Loop Structures

• LabVIEW While Loop• LabVIEW Timed Loop

– precise timing• LabVIEW Simulation Loop

– precise timing + ODE solver


Simulation Parameter Configuration

• Interactive configuration• Programmatic

configuration


LabVIEW Simulation Module Demo


Debugging and Errors

• Create indicator for error output of Simulation Loop

• Utilities>>Get Simulation Parameters, create indicator

• Execution highlighting• Breakpoints• Probes• Custom probes• Single-stepping


Software Tip for LV Sim

• The parameters for each block can be set to be set to:– Configuration Dialog Box– Terminal

• Allows for parameters to be set through data flow programming and mixing of toolkits and modules in one VI


Simulation Icon Styles

• Can change icon style of blocks within simulation loop or subsystem– Static– Dynamic– Text Only– Express

• Right-click on block and choose “icon style”


Simulation Timing Capability

• Can slow down time to study fast dynamics in detail (collision between two cars)

• Can speed up time to study slow dynamics efficiently (temperature control of large water tank)

• Can tie simulation time to wall clock (choose auto period)

• Finish time can be infinite to allow user to adjust dynamics or control gains as simulation is running


Simulation Exercise I – sw timing


Simulation Exercise II – hw timing


Simulation Exercise III - hw timing w delay


Ordinary Differential Equation (ODE) Solvers• ODE solvers approximate solution to

continuous time systems described by differential equations

• Considerations in choosing solver:– Accuracy vs computational speed

• High-order ODE solvers more accurate• Low-order ODE solvers are faster

– Fixed time step vs. variable time step• Variable time step are faster• Fixed time step recommended for real-time

implementation– Stiff systems (transients vary more quickly than

problem solution)• dt is step size of ODE solver

00 )(

),(

yty

ytfdt

dy


Solver Types:

• Fixed step size:– Runge-Kutta 1 (Euler)– Runge-Kutta 2– Runge-Kutta 3– Runge-Kutta 4

• Variable step size:– Runge-Kutta 23– Runge-Kutta 45– BDF (moderately stiff systems)– Adams-Moulton– Rosenbrock (some stiff systems)

• Discrete States Only (fixed time steps for discrete-time systems)


Simulation Discontinuities

• ODE solvers assume that signals and derivatives of signals are continuous

• Discontinuities in nonlinear and discrete systems are accounted for by LV Sim

• For other discontinuities, use Detect Zero Crossing function or configure Integrator function to reset when signal crosses zero


Continuous Linear Systems

• Following models supported:– State space– Transfer function– Zero pole gain

• Integrator• Derivative• Transport Delay


Discrete Linear Systems

• Following discrete models supported:– State space– Transfer function– Zero pole gain

• Discrete Integrator• Discrete Derivative• Discrete Zero Order Hold• Discrete First Order Hold• Discrete Filter


Nonlinear Systems and Lookup Tables

• Backlash• Dead Zone• Friction• Quantizer• Rate Limiter• Relay• Saturation• Switch• Detect Zero Crossing

• Lookup Tables (1,2, & 3D)


Signal Arithmetic

• Gain– Reverse direction

• Summation– Change signs– Add or null inputs– Change shape

• Multiplication– Can add inputs– Change shape


Exercise: Formula Node & Prog Structures for Phase Plane Analysis


LabVIEW for Design, Prototype and Deploy

LabVIEW conditional compiling technology provides for:

– Model reuse – Test reuse

RCP Target

HIL Target

Embedded Target


Demonstration: CompactRIO demo with LabVIEW Simulation Module and RIO I/O

FPGA

Real-Time


Implementation Choices

• LabVIEW Control Design Toolkit Implementation VIs running in Timed Loop

• LabVIEW Simulation Module

Documents

LabVIEW Simulation Module