Vissim For Control System Design & Simulation

VisSim for Control System Design & Simulation
VisSim is a Windows-based program for the modeling and simulation of complex dynamic systems. VisSim combines an intuitive drag-and-drop block diagram interface with a powerful mathematical engine. The visual block diagram interface offers a simple method for constructing, modifying and maintaining complex system models. The mathematical engineprovides fast and accurate solutions for linear, nonlinear, continuous time, discrete time, time varying and hybrid system designs. VisSim is a fully integrated control system design environment where all design and simulation tasks can be completed without writing a line of code. Furthermore, VisSim offers unprecedented ease-of-use and consequently a shorter learning curve than competitive systems.Less time training — more time engineering!

Control System Design Process
VisSim - Control System Design & Simulation
Setpoint

VisSim DSP
Process Variable

Controller

Controller Output

Plant Model

VisSim C Code VisSim Real-Time

Control System Design: The Plant Model

The first step in control system design involves the creation of a plant model. VisSim enables engineers toeasily build plant models, from a first principles perspective, by simply selecting and connecting predefined function blocks. Engineers can construct a wide range of models including linear, nonlinear, continuous, discrete, hybrid, SISO and MIMO systems. VisSim supports hierarchical design by allowing users to group blocks into compound blocks that represent components or sub-systems. Users canalso create custom blocks in C, Fortran or Pascal and add them to the VisSim block library. There is virtually no limit to model size or complexity as VisSim supports over 5 million blocks per diagram. Once designed, the plant model is simulated to compare the plant model outputs to desired behavior. In VisSim, this is immediately visualized with plots, strip charts and other visualization blocks.The plant model can then be refined until the model accurately reflects the desired behavior (conforms to the actual plant or to specifications of the plant model). Plant models can also be derived through system identification methods which “reverse engineer” the plant model from actual plant/equipment data. For more details, request the System Identification data sheet.

Control System Design:Linearization of the Plant Model
After the plant model is verified, the dynamics of a plant can be linearized with VisSim’s Analyze option. Analyze approximates the dynamics of a nonlinear system by linearizing the system about a specified operating point. Linearized systems can be represented in ABCD state space or transfer function form. With Analyze, an engineer can easily access transferfunction information, edit zeroes and poles, and compute Nyquist, Bode and root locus plots. Closed-loop control system where controller gains are tuned using parameter optimization; specified cost function provides parameter tuning flexibility

Bode magnitude and phase plots of the controller and plant subsystem

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Root locus and Nyquist plots of a model

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Modeling The FutureControl System Design: Controller Design
The next step is to design a controller for the plant model by interactively editing compensator zeroes and poles, and observing their combined behavior in Bode and root locus plots. Once the desired responses are obtained, the pole placement controller block is simply inserted into the VisSim diagram. The preliminary pole placement controller is thenconnected to the plant model creating a feedforward or a feedback control loop. A simulation is run and the results of the simulation can be viewed in the form of plots. The stability of the closed-loop system can then be determined using Nyquist plots. In addition to pole placement controllers, VisSim provides pre-configured PI, PD and PID controllers that can be easily customized or optimized for...