Pulse Width Modulated (PWM) Control Signal
Snapshot of the front panel of the simulator:
A control system with a pulse width modulated (PWM) control signal is simulated. The process being controlled is given by a transfer function model representing two time constants in series with a time delay. A process disturbance acts on the process (at the same place as the control signal).
The purpose of PWM is to obtain an approximately continuous or smooth control signal using a binary or on/off actuator or PWM elementet which typically is an SSR element (solid state relay). The principle of PWM is to keep the element in the on state (and in off state) so that the resulting average control signal is as specified. PWM elements operates with a given fixed period, Tp, e.g. 1 sec. The part of the period where the PWM element is in on-state is denoted the duty cycle (D), which is measured in percent. See Figure 1.
In general, the less PWM period Tp, the smoother control signal. PWM is not proper for mechanical actuators as valves because of excessive wear.
The aims of this simulator is to give an understanding of how pulse width modulation works, and to show how the control action works in a control system where the control signal is pulse width modulated.
PWM is an important control technique. It is frequently used for controlling transistor based switches, as SSR elements (solid state relays) for controlling heaters and motors.
The normal operating point is defined as ym = 75 and v = 0.