Steering System355Service Manual – CS7000The Steering Wheel Sensor also has an electromagnetic clutch called a “Torque Feedback Device” whichprovides steering feel to the operator. The clutch consists of multiple fiber discs and steel plates which arealternately stacked. The steel plates are splined to the steering shaft so they always rotate with the shaft.The fiber discs are splined to the clutch housing and are held stationary. When electrical current flowsthrough the clutch field coil winding, the magnetic field generated pulls the plates together creating frictionbetween the plates and discs that resists steering wheel movement. The resistance is proportional to thecurrent flow. The Steering Controller regulates the amount of current flow to provide the right steering“feel”.Steering ActuatorSteering ActuatorThe Steering Actuator consists of a motor, gear setand a position sensor. The motor operates on threephase AC (Alternating Current) and is a “brushless”design. It rotates a gear set that drives the outputshaft. The output shaft is keyed to a drive gear whichdrives a large “ring” gear to turn the rear drive wheelassembly. There is also a sensor inside the motorthat reports position and rotation information tothe Steering Controller. This information providesfeedback to the controller so that it can verify that themotor actually moved as it was commanded to.The Steering Actuator has an internal “encoder” thattranslates motor rotation information into digitalsignals. The end of the motor shaft has a special“diametrically polarized” magnet on it. The line ofseparation between the north and south magneticpoles rotates in close proximity to the encoder. Theencoder “reads” the movement of the magnetic fieldsand creates a two 5v square wave signals. As themotor rotates, one of the signals switches before theother so that the controller can tell which directionthe motor is rotating.Gear SetMotor - RotorMotor -StatorEncoderField Coil(Inside) SteeringShaftSplinesClutchHousingSteel Plates and Fiber DiscsClutch HousingSplines to holdFiber Discs
