What is the effect of excessive proportional gain in a PID controller?

Excessive proportional gain in a PID (Proportional-Integral-Derivative) controller can lead to increased oscillations and instability in the control system. The proportional gain determines how aggressively the controller responds to the error between the setpoint and the process variable. When the gain is set too high, the controller will react more strongly to even small deviations from the setpoint. This aggressive response can result in overshooting the desired value, causing the system to oscillate around the target rather than stabilize.

These oscillations occur because the controller is continually overreacting to the corrections needed, pushing the output beyond the desired state, then underreacting as it tries to compensate, leading to a cycle of continual adjustment. Ultimately, if the proportional gain exceeds a certain threshold, it can lead the system into instability where it diverges rather than converges on the setpoint.

In contrast, lower proportional gain would lead to smoother, more stabilizing control actions, generally resulting in less oscillation and a more predictable response. Understanding the implications of proportional gain is crucial for designing effective PID controllers and ensuring system stability.