This example shows a concept development phase version of a fan speed control loop. It uses a PID-based (Proportional, Integral and Derivative) control strategy, with continuous block-diagram representation for both the controller and the voltage drive for the DC motor.
The motor, which is characterized to represent an FRC (First Robotics Competition) CIM Motor, and the attached mechanical fan load, use a conservation-based modeling approach. Both the static and dynamic interaction characteristics “emerge” naturally from the model, simply because they are “connected” on the schematic. This approach to system modeling is much like assembling a hardware prototype, and does not require the user to develop an analytical model of the “plant” being controlled. Additional external electrical circuit components, mechanical loads and other “physical” elements can easily be added by simply placing them on the schematic and “wiring” them together. In fact, a more detailed implementation of the motor drive is shown in the companion example, “PID Speed Control Loop – Switching”. In that example, a design for the logic and power electronics needed to implement a PWM-based, switched MOSFET H-bridge drive is included.
Because this version simulates very quickly compared to the switching version, it is well suited for early concept validation of the control strategy and PID tuning, loop stability and frequency response analysis, etc.