Steering Wheel Actuator H-Bridge Sharing for Compact Steer-by-Wire
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Solution Overview
Problem
The existing steer-by-wire systems have a large steering wheel actuation unit due to separate H bridges for each motor, increasing the overall size and cost, which is a challenge in confined spaces like the steering column.
Innovation Solution
A shared hardware architecture with time-division multiplexing of power electronics is implemented, where brushed DC motors share a common arm of switches and the brushless DC motor operates with dual three-phase H bridges, reducing the number of components and drivers, thereby decreasing the size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate H bridges are used for each motor in the steering wheel actuator, then each motor can be controlled independently, but the overall size and cost of the steering wheel actuation unit increases
Solution Approach 1:
The patent combines multiple H bridge circuits into a shared power electronics module that serves multiple motors (radial motor, axial motor, and steering wheel motor). This merging of previously separate control circuits reduces the overall component count and physical size while maintaining the ability to independently control each motor through selective activation of specific H bridges within the shared module.
Solution Approach 2:
The shared power electronics module is designed to perform multiple functions by controlling different motors at different times. The same H bridge circuitry can be selectively activated to drive the radial motor for tilt adjustment, the axial motor for telescopic adjustment, or the steering wheel motor for steering control, making the power electronics universal rather than dedicated to a single motor.
2Ease of operation
If separate H bridges are used for each motor in the steering wheel actuator, then each motor can be controlled independently, but the cost of the steering wheel actuation unit increases
Solution Approach 1:
The patent combines multiple H bridge circuits into a shared power electronics module that serves multiple motors (radial motor, axial motor, and steering wheel motor). This merging of previously separate control circuits reduces the overall component count and physical size while maintaining the ability to independently control each motor through selective activation of specific H bridges within the shared module.
Solution Approach 2:
The shared power electronics module is designed to perform multiple functions by controlling different motors at different times. The same H bridge circuitry can be selectively activated to drive the radial motor for tilt adjustment, the axial motor for telescopic adjustment, or the steering wheel motor for steering control, making the power electronics universal rather than dedicated to a single motor.
3Adaptability or versatility
If the steering wheel actuator includes both steering wheel actuation and steering column adjustments, then functionality is enhanced, but the size of the actuation unit increases
Solution Approach 1:
The patent integrates multiple motor control functions (radial motor for tilt, axial motor for telescopic adjustment, and steering wheel motor for steering control) into a single shared power electronics module. This consolidation of previously separate control systems into one unified module reduces the overall physical size while maintaining all the required adjustment and control functionalities.
Solution Approach 2:
The shared power electronics module is designed to perform multiple functions by controlling different motors at different times. The same H bridge circuitry can be selectively activated to drive the radial motor for tilt adjustment, the axial motor for telescopic adjustment, or the steering wheel motor for steering control, making the power electronics universal rather than dedicated to a single motor.
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 approach effectively reduces the size and cost of the steering wheel actuation unit by multiplexing power electronics, addressing the space constraints and economic inefficiencies of conventional systems.
Implementation Method 1
The radial motor and axial motor are brushed DC motors
Implementation Method 2
The steering wheel actuator drives the steering wheel by way of a steering wheel motor, which is a six-phase brushless DC motor
Data Source
AI summary
A steer by wire system includes at least a steering wheel actuator for operating steering wheel and steering column. The steering wheel actuates the steering wheel actuator by way of a brushless DC motor. The steering wheel actuator adjusts the steering column in a tilt direction by way of a first brushed DC motor and in a telescopic direction by way of a second brushed DC motor. The first brushed DC motor and the second brushed DC motor are configured to operate via two separate H bridges having a shared arm of switches. The brushless DC motor is configured to operate with two three-phase H bridges of which one three-phase H bridge is the network of switches of the first brushed DC motor and the second brushed DC motor.