Steer-by-Wire Passive Mode for Idle Power and Heat Reduction
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Solution Overview
Problem
Steer-by-wire systems in motor vehicles experience high power consumption and thermal load on electrical components due to continuous operation of the position controller even when the vehicle is stationary and no steering input is provided.
Innovation Solution
Implementing a passive mode detection system that sets the motor torque request to zero when the vehicle is stationary and no steering input is detected, using a torque limiter or modifying the requested rack position to reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the position controller remains active continuously to maintain steering rack position, then steering precision and control reliability are improved, but power consumption and thermal load on electrical components increase
Solution Approach 1:
The controller dynamically adjusts its operation mode based on real-time detection of vehicle state and steering input. When the vehicle is stationary and no steering input is detected, the controller transitions to a passive mode with reduced power consumption. When steering input is detected or the vehicle is moving, the controller automatically switches to active mode with full control functionality, ensuring steering precision is maintained when needed.
Solution Approach 2:
The controller changes its operational parameters based on the detected state. In passive mode, the motor torque request is set to zero and the position controller is deactivated. Upon detecting steering input or vehicle movement, the controller transitions to active mode with full torque and control parameters restored, thereby adapting power consumption to actual operational requirements.
2Measurement precision
If the position controller operates continuously to maintain rack position, then steering accuracy is improved, but thermal load on motor and ECU increases reducing component lifespan
Solution Approach 1:
Instead of continuous operation, the position controller operates periodically based on detected needs. The passive mode detector continuously monitors for steering input and vehicle state, triggering active controller operation only when steering input is detected or the vehicle begins moving. This periodic activation maintains steering accuracy when required while significantly reducing thermal accumulation during idle periods.
3Use of energy by moving object
If the motor torque request is set to zero in passive mode, then power consumption is reduced, but steering response time may be increased when activation is required
Solution Approach 1:
The passive mode detector continuously monitors for steering input and vehicle state in advance, detecting the need for active control before full steering operation is required. This preliminary detection allows the controller to transition from passive to active mode proactively, minimizing any potential delay in steering response while still maintaining power savings during extended idle periods.
Data Source
AI summary
A method for power saving in a steering system of a motor vehicle including a road wheel actuator acting on a rack to turn steerable road wheels and a controller configured or programmed to generate an operation signal for the road wheel actuator, wherein the controller includes a position controller to generate a motor torque request based on an actual and/or a measured position of the rack and a requested rack position, includes detecting a passive mode of the steering system by a passive mode detector of the controller if the motor vehicle is stopped and no steering input is provided, and if a passive mode is detected by the passive mode detector, setting the motor torque request to zero in order to save power.