Torque Sensor Failure Detection via Continuous Motor Vibration
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Solution Overview
Problem
Existing electric power steering systems face challenges in accurately determining the functionality of a single torque sensor when the other is faulty, which can lead to unreliable motor assistance and steering performance.
Innovation Solution
A failure detection device that uses a controller to generate continuous torque detectable by the remaining torque sensor, allowing for diagnosis of sensor failure based on vibration patterns, ensuring proper operation even when only one torque sensor is functioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two torque sensors are provided to accurately determine steering torque, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary failure detection by comparing output values from two torque sensors before using them for steering torque calculation. This preliminary check identifies faulty sensors in advance, allowing the system to switch to alternative detection methods (using motor current calculations) to maintain functionality without requiring both sensors to be operational simultaneously.
Solution Approach 2:
The controller acts as an intermediary that mediates between the two torque sensors and the final torque calculation. It processes sensor outputs, detects failures through comparison, and selects appropriate data sources (either sensor outputs or motor current-based calculations) to ensure accurate steering torque determination regardless of sensor status.
2Device complexity
If one torque sensor is assumed to be working properly when another fails, then device complexity is reduced, but reliability deteriorates
Solution Approach 1:
The system continuously monitors the output values from both torque sensors and uses feedback comparison to detect failures. When a discrepancy is detected between sensor outputs, the system triggers a feedback mechanism to verify sensor status and switch to alternative detection methods, ensuring reliable operation even when one sensor is faulty.
Solution Approach 2:
The torque detection system performs self-diagnosis by comparing its own sensor outputs to identify failures. The system serves itself by automatically detecting which sensor is malfunctioning and switching to backup detection methods without external intervention, maintaining reliability while simplifying the operational configuration.
3Reliability
If motor current is used to calculate torque when a sensor fails, then reliability is improved, but measurement precision deteriorates
Solution Approach 1:
The system changes the measurement parameter from direct sensor output to motor current calculation when sensor failure is detected. By switching between different parameter sources (sensor voltage outputs vs. motor current measurements), the system maintains reliable torque detection while accepting temporary precision trade-offs during sensor failure conditions.
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
Enables reliable determination of a working torque sensor's status, maintaining accurate motor assistance and steering performance even when one sensor fails, reducing driver burden and improving steering feel by ensuring continuous torque transmission.
Implementation Method 1
the controller causes the motor to output continuous torque continuously generating torque that is detectable by an other of the two torque sensors
Implementation Method 2
two magnetosensitive elements each composed of a hall element whose electric properties (resistance) vary under the effect of a magnetic field
Implementation Method 3
the failure detection unit diagnoses failure of the other of the two torque sensors on a basis of a pattern of vibrations detected by the other of the two torque sensors due to the continuous torque
Data Source
AI summary
The failure detection device includes: an output unit detecting failure of a torque detection device that detects torque applied to a pinion shaft with torque sensors, and a target current calculation unit controlling drive of the electric motor. In response to detection of failure of one of the torque sensors, the target current calculation unit causes the motor to output continuous torque continuously generating torque that is detectable by the other of the torque sensors and, in response to the motor outputting the continuous torque, the output unit diagnoses failure of the other of the torque sensors based on a pattern of vibrations detected by the other torque sensor due to the continuous torque and determines that the other torque sensor is having failure if amplitude of vibrations is less than a reference amplitude.