Power take-off control system.

A control system (10) and method for detecting variable load types and controlling the operation of a PTO clutch (18) to effect engagement of the clutch (18) with variable loads, and especially to more optimally effect the engagement of a clutch (18) with a very light load or an associated over-running clutch (87) or a heavy load is disclosed. The control system (10) includes a controller (20) that receives input and output clutch shaft speed signals and generates control signals to control the pressure applied by the clutch (18). If no appreciable engine droop is detected at the time of initial movement of the output clutch shaft (32), the load is considered to be of a very light load type, and a set of control signals based upon such load type designation, which control signals define a control curve that is flatter and more gentle than would otherwise be considered desirable, is thereafter applied to the clutch (18) to effect engagement of the load. When heavier loads are applied to the PTO shaft, during the time when control signals are being generated before detection of initial movement of the output shaft (32), the controller (20) generates one or more shock signals of short duration to cause momentary applications of significantly greater pressure to the clutch (18) in order to break loose the applied load. Based upon the time of detection of initial movement by the output shaft (32), load categorization can be made, and control signals that are thereafter generated before lockup may be dependent, in part, upon the determined load categorization.