Acura NSX 1991 Manual page 412

Main Menu
System Description
Function and Operation
EPS Control Unit
The control unit receives input signals from the car's speed sensors, torque sensor and rotation sensor. It performs a mul-
titude of control functions, including a circuit which can detect troubles in each functional part of the system and the con-
trol unit itself. The control unit operates the system while the engine is in the process of starting, on receipt of voltage
generated by the alternator. The system remains operational if the engine stalls with the ignition switch in ON (II) position.
Basic Control
(1) Travelling speeds are compiled into data, receiving input signals from the car's speed sensors.
(2) The magnitude and direction of torque are compiled into data, receiving input signals from the torque sensor.
(3) The rotational speed and direction of steering are compiled into data, receiving input signals from the rotation sensor.
(4) Determination of motor torque data from the prescribed assisting force map, based on the car speed data, steering
rotational speed data and the steering torque data.
(5) Changeover of control modes based on data on car speed, direction of torque and rotational direction of steering.
Normal Control Mode:
The rotational direction of motor is determined after changing over to the left/right steering mode in accordance with
torque direction data. The mode is switched to the straight ahead mode when the output data is zero.
Return Control Mode:
According to torque direction data and steering rotational direction data, the mode is changed over to the return control
mode to improve the steering return characteristic.
Damper Control Mode:
According to car speed data, torque value data and steering rotational speed data, the mode is changed over to the
damper control mode to improve the convergence property of the steering.
Rotation sensor
Steering rotation duty
Output duty
Mode changeover
• Normal mode
• Return mode
• Damper mode
Table of Contents
Torque sensor
Unloader duty
(Reduces over-current flow
at full-lock position)
Torque duty
Motor control
signal output
Car speed sensors
Base duty