22. Control

Practically all control systems that are implemented today are based on computer control.

A computer-controlled system can be described schematically as shown in Figure1.

  • Outputs from the GPlant are continuous-time signal and converted into digital signals by analog-to-digital (A-D) converter.

  • The conversion process is performed and controlled by selected sampling times.

  • The system computer:

    • Interprets the converted signals

    • Processes the measurements using a control algorithm

    • Gives new digital signals.

  • The generated signals from the control algorithm are also converted into analog signals for GPlant input by a digital-analog (D-A) converter.

  • The real time clock in the computer synchronizes the events.

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    Figure 22.1 Schematic diagram of a computer controlled system

In the simulation of a computer-controlled system, design algorithms of controller and mechanical systems (so-called GPlants) should be evaluated simultaneously.

  • The control algorithm is easily designed by control design application software such as MATLAB/Simulink

  • The GPlant is constructed by mechanical system simulation software such as RecurDyn.

  • An interface toolkit such as the RecurDyn/Control is required to communicate between the control system design and mechanical system design software. The schematic diagram of RecurDyn/Control is shown in Schematic diagram of RecurDyn/Control.

  • RecurDyn simulates the GPlant model and the control design software simulates the control algorithm in this co-simulation architecture.

  • During the co-simulation between RecurDyn and the control system design software, the result outputs from RecurDyn and the control system design tools are passed to each other at a constant sampling time.

  • Thus the outputs from RecurDyn are assumed to remain at the same value during the sampling period.

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    Figure 22.2 Schematic diagram of RecurDyn/Control