Analysis

LabVIEW add-on: System Simulation and Design

Overview
National Instruments System Simulation and Design Toolkit is LabVIEW add-on software for simulating, designing, analyzing, and optimizing linear and nonlinear control systems. Accelerate your system design by using VIs modeled after symbols and blocks used in control engineering - H(s) for transfer function, 1/s for integration, z for delay, and so on. These control and simulation VIs are easy to use and specifically built to meet the requirements of control engineers who are under pressure to reduce cost and time to market. Logically named VIs and predefined control elements such as PID, relays, and filters make your development easier. Plus, immediately integrate National Instruments DAQ hardware into your control system after you have designed and simulated your system. All System Simulation and Design Toolkit VIs are built to intuitively work together so you can develop faster and use only a few Vis.

Designing a Control System
To aid in advanced control design and optimization, you can transform between different representations for your system such as state-space and transfer function representation. Create a plant model of your actual system using these different representations and then design a control strategy using the functions provided or your own control algorithm VIs. Compute the poles and zeros of the transfer function H(s) of your system, damping ratio, natural frequencies, DC gain, and transmission zeros, and determine the stability of your system. If your system is unstable or if you wish to change the characteristics of your system, you can graphically move poles and zeros of your system to desired locations and then compute the feedback gain for the new closed loop system. In addition, you can view the dynamic response of the system to standard inputs such as step, ramp, or your own customized input signal.

Real-Time Control Features
The System Simulation and Design Toolkit includes utility VIs for managing, synchronizing, and monitoring real-time behavior. For your control system, select from several continuous integrators (Euler, Adams, Runge-Kutta); and for your discrete designs, you can select from several discrete integrators (Euler backward, Euler forward, trapezoidal).

Analyze and Optimize Your Control Design
Once you have designed your system, you can then analyze your design. Calculate the Bode, Nyquist, and Root Locus plots for the control system that you have designed. The Root Locus VI not only plots the Root Locus but also creates a text file that contains valuable information such as break-away points and angles of asymptotes. Plus, calculate the overall transfer function of two systems connected in series or parallel, or in a feedback loop.

System Simulation and Design VIs Designed to Work with Hardware
The VIs in this toolkit are designed to work with National Instruments data acquisition, instrument control, and serial hardware. Begin your design by simulating your system or plant model using the control VIs. After you are satisfied with your simulation design, add your source (such as analog input) and control output (such as analog output) and immediately control your system. The following table summarizes some benchmark testing of loop speeds using various DAQ hardware with LabVIEW. For these tests, the control loop is hardware timed by using a continuous analog input operation. The values represent maximum loop rates when no movement of the mouse occurs.

Table 1. Hardware-Timed Control Loop (Continuous AI/AO Write)

Control Applications in Industry
Use the System Simulation and Design Toolkit in diverse fields such as mechanical, electrical, aeronautical, and biomedical engineering. The software includes several examples to help you in simulating and prototyping your customer control system. These examples include the inverted pendulum example, proportional-integral-derivative (PID), cascaded water tanks, chemical reactors, heating with relays, conventional design of an angular control system for a robot-joint, full-order estimators for a space satellite's attitude-control system and so on. Overall, you can simulate, design, and control from the same development environment. The System Simulation and Design Toolkit covers all the phases involved in a design process, from simulation to control.

VI List

• System Simulation and Design Tools for LabVIEW