EPS Wake-Up Control Using Back-EMF to Restrain Steering Wheel Rotation
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Solution Overview
Problem
In steer-by-wire (SBW) electric power steering (EPS) systems, there is a need for a simple and low-power device to restrain the rotation of the steering wheel when the vehicle's ignition is off, as existing locking circuits consume power and complicate the control device.
Innovation Solution
A control device and method that utilize back electromotive force generated by forced motor rotation to wake up the electronic control unit (ECU) and apply a reaction torque to the motor, thereby restricting the rotation of the steering wheel in the vehicle ignition-off state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking circuit is used to prevent motor rotation in ignition-off state, then the steering wheel rotation is restrained, but power consumption occurs and control device becomes complicated
Solution Approach 1:
The patent extracts the locking function from a separate locking circuit and integrates it into the existing EPS control unit. The control unit utilizes its existing motor control capabilities to implement locking by adjusting motor phase winding connections, eliminating the need for a dedicated locking circuit while maintaining steering wheel restraint functionality.
Solution Approach 2:
The EPS control unit is made multi-functional by enabling it to perform both normal steering assistance and locking functions. The control unit uses its existing motor control circuitry to implement locking through specific winding connections, allowing one device to serve multiple purposes and reducing overall system complexity.
2Reliability
If a locking circuit is used to prevent motor rotation in ignition-off state, then the steering wheel rotation is restrained, but power consumption occurs
Solution Approach 1:
The locking function is implemented using the EPS motor control unit's existing resources and capabilities. The control unit utilizes its own motor control circuitry and power management systems to execute locking, eliminating the need for a separate powered locking circuit and reducing overall power consumption while maintaining steering restraint.
3Use of energy by moving object
If the reaction force motor is turned off in ignition-off state, then power consumption is reduced, but the steering wheel may rotate arbitrarily
Solution Approach 1:
The control unit executes locking actions before the ignition completely shuts down. By implementing locking through motor control during the transition period, the system ensures steering wheel restraint is established prior to power cutoff, maintaining security while minimizing power consumption in the off state.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively prevents the arbitrary rotation of the steering wheel, enhancing vehicle stability and security against theft, while reducing power consumption and simplifying the control device.
Implementation Method 1
A control device and method capable of waking up an electronic control unit (ECU) by motor rotation
Data Source
AI summary
The present embodiments relate to a control device and method for an electric power steering (EPS) system, and an EPS system including the same. A control device according to an embodiment may include a steering controller configured to control a rotation of a motor linked to a steering wheel, and a wake-up circuit configured to, in an ignition-off state of a vehicle, wake up the steering controller using back electromotive force generated in the case of a forced rotation of the motor by an external force, wherein the steering controller may apply a reaction torque to the motor to suppress the forced rotation of the motor after waking up.