I designed an IC engine controll unit for Hybrid Electric Vechile(HEV). The engine speed controlled by engine throttle valve.The throttle valve of engine is controlled by stepper motor with calculated PID value.In my test condition , I choose 1 second time interval for PID calculation, it also fine.When I used lesser time such as 100 ms, 250ms etc there is a large scale oscillation when there is a small deflection. My engine rpm is nominal 2000 ,and maximum 2500 rpm.
In this application , there may be a sudden change in voltage drop via torque change. So we can't choose a much long time for PID calculation.
Then how can I solve these situation?