STEM AS 5P4937 - Caterpillar

Adjusting the Governor
The response of the throttle actuator can be adjusted with Cat ET. Use Cat ET to change these three parameters:
Proportional Gain
Integral Gain
Derivative GainFor details on these parameters, refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters". The default values should be sufficient for initial start-up. However, the values may not provide optimum performance.These adjustments are provided in order to obtain optimum responses to changes in the engine's load and in the engine's speed. The adjustments also provide stability during steady state operation.If you have a problem with instability, always investigate other causes before you adjust the governor. For example, diagnostic codes and unstable gas pressure can cause instability.When you adjust the primary governor, make sure that the "Grid Status" parameter is "Off". When you adjust the auxiliary governor, make sure that the "Grid Status" parameter is "On".To change the proportional gain, the integral gain, or the derivative gain, use the "Real Time Graphing" feature on the "Information" drop-down menu of Cat ET. The graph provides the best method for observing the effects of your adjustments.After you make adjustments, always test the stability by interrupting the engine speed and/or load. Operate the engine through the entire range of speeds and of loads in order to ensure stability.Note: Adjustment of the proportional gain directly affects the speed of the throttle actuator when there is a difference between the actual engine speed and the desired engine speed. An excessive increase of the proportional gain may amplify instability.To set the proportional gain, increase the proportional gain until the actuator becomes unstable. Slowly reduce the proportional gain in order to stabilize the actuator. Observe that the engine operates properly with little overshoot or undershoot.The adjustment of integral gain dampens the actuator's response to changes in load and in speed. Increasing the integral gain provides less damping. Decreasing the integral gain provides more damping. To reduce overshoot, decrease the integral gain. To reduce undershoot, increase the integral gain.Note: An increase of the integral gain may require a decrease of the proportional gain in order to maintain engine stability.Illustration 13 shows some typical curves for transient responses.
Illustration 13 g01017530
Typical curves for transient responses (Y) Engine speed (X) Time (1) The proportional gain is too high and the integral gain is too low. There is a large overshoot on start-up and there are secondary overshoots on transient loads. (2) The proportional gain is slightly high and the integral gain is slightly low. There is a slight overshoot on start-up but the response to transient loads is optimum. (3) The proportional gain is slightly low and the integral gain is slightly high. There is optimum performance on start-up but slow response for transient loads. (4) The proportional gain is too low and the integral gain is too high. The response for transient loads is too slow. (5) The response to transient loads is adjusted for optimum performance.Decrease the derivative gain until a slow, periodic instability is observed. Then, slightly increase the derivative gain. Repeat the