Electric Power Steering Speed Synchronization via Feedback Control
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Solution Overview
Problem
The existing electric power steering apparatuses face reduced responsiveness and stability due to rotational speed differences between the steering motor and the output shaft caused by mechanical gaps, which affect the steering performance.
Innovation Solution
An electric power steering apparatus that includes a steering motor, position sensors to measure rotational angles, an angle sensor for the output shaft, a compensation unit to calculate speed differences, and a steering control unit to adjust the current input to the motor, thereby compensating for these differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a reducer with damping coupler, worm, or worm wheel is used to transmit auxiliary power to the output shaft, then the steering motor can provide sufficient torque assistance, but a mechanical gap is generated between the motor shaft and output shaft causing rotational speed difference
Solution Approach 1:
The control unit continuously monitors the rotational speed of both the steering motor and output shaft, calculates their difference, and adjusts the motor current in real-time to compensate for the speed discrepancy caused by mechanical gaps in the reducer
Solution Approach 2:
The system dynamically adjusts the electrical parameter (motor current) to compensate for the mechanical parameter discrepancy (rotational speed difference) introduced by the reducer's mechanical gap
2Device complexity
If mechanical components with gaps are used in the power transmission path, then the steering motor can be decoupled from direct connection to output shaft, but rotational speed difference occurs between motor and output shaft
Solution Approach 1:
The patent replaces mechanical speed synchronization mechanisms with an electrical control system that uses sensors and feedback control to achieve rotational speed matching between the motor and output shaft
3Speed
If the steering motor directly drives the output shaft without a reducer, then rotational speed synchronization is maintained, but sufficient steering assistance torque cannot be provided
Solution Approach 1:
The control unit acts as an intermediary that coordinates between the steering motor and output shaft, using feedback control to ensure that despite the mechanical reducer in between, the rotational speeds remain synchronized
Data Source
AI summary
The present invention relates to an electric power steering apparatus and a method of controlling the same. The electric power steering apparatus includes an electric power steering apparatus including a steering motor that assists the steering force of the steering wheel; a position sensor that measures the rotational angle of the steering motor; an angle sensor that measures the rotational angle of an output end of an output shaft connected to the steering wheel; a compensation unit that calculates the difference between an angular speed of the steering motor and an angular speed of the output end of the output shaft by using the rotational angle measured by the position sensor and the rotational angle measured by the output end of the output shaft; and a steering control unit that controls a current input to the steering motor to compensate for the difference between the angular speed of the steering motor and the angular speed of the output end of the output shaft, according to the calculation result from the compensation unit. Accordingly, responsiveness and stability can be improved during a steering operation of a steering wheel by decreasing the difference between the rotational speeds of a steering motor and an output end of an output shaft that occurs due to a mechanical gap of the steering motor.