Steering Rack Position Detection via Rotor Kinematics
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Solution Overview
Problem
In steering systems with electric servomotors, malfunctions in the transmission path between the servomotor and the rack, such as angular offsets or slip, lead to inaccurate detection of the rack-and-pinion position, which affects the accuracy of automatic driving.
Innovation Solution
A method that analyzes kinematic and dynamic rotor sizes to detect threshold value exceedances, generating an event signal to prevent activation of automatic driving and ensuring accurate rack-and-pinion position determination by monitoring phase currents and sensor signals, allowing for continuous operation and transition to driver-based driving if malfunctions occur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the rack-and-pinion position is determined based on rotor position in a steering system with electric servomotor, then automatic driving functionality can be implemented, but malfunctions in the transmission path (angular offsets, slip) lead to inaccurate position detection
Solution Approach 1:
The system performs preliminary initialization to establish an absolute rack-and-pinion position reference before automatic driving operation. This preliminary action stores the relationship between rotor position and rack position, enabling accurate position determination during automatic driving while providing a baseline for detecting transmission path malfunctions.
Solution Approach 2:
The system continuously monitors the transmission path between servomotor and rack, comparing expected rotor position with actual rack position. When deviations exceed thresholds indicating angular offsets or slip, the system generates event signals and switches to driver-based operation, providing feedback that maintains position detection accuracy despite transmission malfunctions.
2Reliability
If continuous monitoring of rotor position is performed to detect transmission malfunctions, then system safety is improved, but complexity of the detection system increases
Solution Approach 1:
The system uses the existing rotor position sensor and control unit to perform self-monitoring of transmission path malfunctions. No separate detection hardware is added; instead, the control unit analyzes existing sensor signals and motor current data to detect angular offsets and slip, maintaining system safety while avoiding increased hardware complexity.
Solution Approach 2:
The system monitors changes in kinematic and dynamic rotor parameters (position, speed, acceleration, current) to detect transmission malfunctions. By analyzing parameter deviations and comparing them against thresholds, the system identifies angular offsets and slip conditions using existing sensors, achieving reliable detection without adding complex measurement equipment.
Data Source
AI summary
A method for determining a rack-and-pinion position in a steering system having an electric servomotor and a rack includes determining kinematic changes in a transmission path between the servomotor and the rack. The method further includes generating an event signal when a kinematic or dynamic rotor size of the servomotor exceeds an assigned threshold value.