In the actual control process of VP Card 1C31194G03, due to delays in the actuator and measuring device, the system may exhibit a pure lag process. For instance, in temperature control, the delay time can be as long as over 10 minutes. This lag characteristic often causes the controlled object to overshoot or oscillate, making it difficult for the system to reach a stable process. Therefore, a compensation link can be connected in parallel during the control process to compensate for the lag part in the controlled object, enabling the system to quickly achieve a stable process.

A pure lag control system uses the result of lag compensation as the input compensation value (ICV) for the PID controller and serves as a subtractive compensation for input compensation. This forms a pure lag SMITH predictive control loop.