Clutch Actuation

Clutch actuator is a mechatronic system that is aimed to provide effective control of a variable that directly influences the clutch torque. The influencing variable is usually the clutch contact surface normal force, whereas in some specific cases of clutches without axial movement, this can be a nonmechanical variable such as the magnetic flux density. This chapter first presents design, principle of operation, and main components of various clutch actuation concepts, including traditional hydraulic and pneumatic systems, more recent electromechanical and electromagnetic systems, and emerging magnetorheological fluid and magnetic particle concepts. Next, the main static and transient features of the clutch actuation system behavior are described. Finally, the basic clutch torque control structures relying on open-loop force control or closed-loop position control are presented. This includes description of auxiliary estimation and control subsystems such as adaptive compensation of clutch clearance, actuator mechanism friction compensation, estimation of clutch friction interface temperature, and adaptation to clutch friction coefficient variation.