Power Steering Control Unit Current Limit Compensation
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Solution Overview
Problem
Existing electrical power steering systems fail to maintain coordinated control with other vehicle systems when the driving current to the electric motor is limited, leading to deviations in target steering angles and assist torques, which prevents the desired vehicle movement.
Innovation Solution
The electrical power steering system includes a power steering control unit that calculates a feasible torque for the steering assist electric motor when current is limited, operates the motor at this torque, and communicates with other control units to compensate for differences in target and feasible torques, ensuring optimal vehicle control by adjusting based on factors like power voltage, temperature, and vehicle speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driving current to the electric motor is limited to prevent overheating or power voltage decrease, then the electric motor and control unit are protected from damage, but the target steering assist torque cannot be achieved and coordinated control with other vehicle systems deteriorates
Solution Approach 1:
The power steering control unit continuously monitors the actual steering assist torque and compares it with the target torque. When current limitation occurs, the system detects the deviation and communicates this information to the vehicle movement total control unit, enabling real-time feedback-based coordination to maintain overall vehicle control accuracy.
Solution Approach 2:
The power steering control unit acts as an intermediary between the electric motor and the vehicle movement total control unit. It receives target torque commands, adjusts them based on current limitation status, and communicates operational information to other control units, thereby mediating the torque discrepancy caused by current limitation.
2Temperature
If the driving current to the electric motor is limited, then the overheating of electric motor is prevented, but the desired vehicle movement cannot be realized due to deviation from command signal
Solution Approach 1:
The system implements feedback by monitoring the actual steering assist torque and comparing it with the target torque. When current limitation causes torque deviation, this information is fed back to the vehicle movement total control unit, enabling real-time adjustment of control commands to maintain accurate vehicle movement despite thermal constraints.
Solution Approach 2:
The power steering control unit dynamically adjusts the steering assist torque based on real-time motor temperature and current limitation status. This dynamic adjustment allows the system to operate within thermal safety limits while maintaining coordinated control with other vehicle systems through continuous adaptation of control parameters.
3Reliability
If other control units stop transmitting command signals when receiving current limit information, then the power steering system is protected, but the coordinated control for vehicle movement is disrupted
Solution Approach 1:
Other control units dynamically adapt their command signals based on the operational status information received from the power steering control unit. Instead of stopping signal transmission, they adjust their commands in real-time to account for current limitation conditions, maintaining coordinated control while respecting the power steering system's operational constraints.
Solution Approach 2:
The power steering control unit provides continuous feedback about its operational status (including current limitation conditions) to other vehicle control units. This feedback mechanism enables other control units to adjust their command signals appropriately, maintaining coordinated vehicle control without disrupting the power steering system's protection measures.
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 allows the electrical power steering system to maintain coordinated control with other vehicle systems even during current limitations, ensuring optimal vehicle control and minimizing driver discomfort by compensating for torque differences with other control systems.
Implementation Method 1
In the electrical power steering system, in which a steering assist torque is applied to a steering device by an electric motor
Data Source
AI summary
An electrically driven power steering system for a vehicle comprises a steering sensor for detecting a steering operation of a steering wheel and a power steering control unit, which receives a command signal from a vehicle movement total control unit, calculates a target steering assist torque from a steering signal from the steering sensor and the command signal and drives a steering assist electric motor in accordance with the above calculated target steering assist torque. The power steering control unit further calculates a feasible torque to be generated at the steering assist electric motor, and drives the steering assist electric motor at the feasible torque, when the feasible torque is lower than the target steering assist torque, namely when a driving current to the electric motor should be limited due to an increased temperature of the electric motor and so on.