EPS System Description - EPS Control
The base current is a basic current value to drive the motor and is calculated using the steering torque and the vehicle speed.
The torque of the EPS motor tends to be lower as the vehicle begins to move and higher as it decreases in speed due to the inertia of
the rotating body. To reduce the impact of the inertia, the inertia compensation increases the base current in acceleration and
decreases in deceleration. The current of the inertia compensation is calculated by using the steering torque, vehicle speed, and
The steering wheel receives vibration from the road surface during braking or cornering. The damping compensation reduces the
vibration of the steering wheel by applying a damping effect through the motor current control. The damping compensation current is
calculated by the steering torque, the vehicle speed, and the motor speed.
The target current is a value necessary to perform feedback control of the motor and is determined by applying inertia and damping
compensation to the base current and adding steering torque direction.
Current Feedback Control
Current feedback control monitors the motor current through sensors and reduces any deviation of motor current compared to the
target current, thus accurately running the motor.
The unloader control reduces motor current at the lock to lock (full right or left) of the steering wheel to protect the system. This value
is determined by using the target current and the motor speed.
Steering Speed Feedback Control
The steering speed feedback control improves stability in the high speed range by controlling the hysteresis of the steering torque.
The steering speed feedback control current is calculated by using the deviation between the target and actual steering angle speed
to adjust to the base current.
Straight Driving Steering Assist
Steering effort is detected and reduced by applying EPS motor assist when driving on a sloped road. This control will return to normal
when no longer driving on a sloped road. This function only operates when the cruise control is on and the speed is set
EPS Motor Control Circuit
The EPS motor control circuit is composed of a system control CPU, the FET (Field-Effect Transistor) drive circuit, the FET bridge, the
power relay, the fail-safe relays, the electric current detection circuit, relay drive circuit, and the EPS motor. With the signal from the
input sensor, the CPU calculates the appropriate current for the FET drive circuit. This operation is duty controlled.
EPS System Description - EPS Control 1526 http://techinfo.honda.com/rjanisis/pubs/sm/1/2/Contents/enu/61TBAD/...
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