Dual-Motor Gearbox Backlash Estimation Using Differential Torque
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Solution Overview
Problem
Conventional motor assemblies in steer-by-wire systems face issues with gearbox wear and backlash, leading to impaired vehicle steering and the need for frequent component replacement, as existing technologies lack effective methods for monitoring and managing backlash in dual motor drive systems.
Innovation Solution
A dual motor drive assembly with a housing, rotatable shaft, first and second motors, output gears, a motor controller, and a processing arrangement that applies differential torques to overcome friction and estimate backlash by measuring angular position signals, allowing for continuous monitoring and detection of gearbox wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual motor drive system is used to reduce gear rattle and provide redundancy, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines two motor drive systems into a single integrated assembly where both motors share common components including the housing, shaft, first gear, and processing arrangement. This merging approach provides redundancy and reliability through dual motors while reducing overall device complexity by sharing mechanical components rather than having completely separate drive systems.
Solution Approach 2:
The processing arrangement serves multiple functions: it determines angular position signals from both motors, allocates torque demands to minimize backlash, monitors gear engagement status, and detects when backlash exceeds thresholds. This multi-functionality reduces the need for separate monitoring and control systems, thereby reducing device complexity while maintaining high reliability.
2Manufacturing precision
If torque demands are allocated to minimize backlash, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The processing arrangement continuously receives angular position signals from both motors, calculates the actual backlash based on the difference between commanded and actual gear engagement, and uses this feedback to dynamically adjust torque demand allocation. This feedback mechanism achieves precise backlash control while using a relatively simple computational approach that does not require complex control hardware.
Solution Approach 2:
The system controls backlash by dynamically changing the torque parameter applied to each motor based on operating conditions. The processing arrangement adjusts the torque demand allocation between the two motors to minimize backlash, varying this parameter in real-time without requiring physical adjustments to the mechanical components, thereby achieving precision without mechanical complexity.
3Measurement precision
If angular position signals are monitored to estimate backlash, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The motors' existing angular position sensors (encoders or resolvers) are used to provide the data needed for backlash estimation. The processing arrangement self-services by using the same sensors that control motor position to also monitor gear engagement and estimate backlash, eliminating the need for separate measurement devices such as dial indicators or laser measurement systems.
Solution Approach 2:
The angular position signals serve dual purposes: controlling the position and speed of the motors during normal operation, and providing data for backlash estimation and gear engagement monitoring. This multi-functional use of the same sensors and processing capability achieves precise backlash measurement without adding dedicated monitoring hardware, thereby avoiding increased device complexity.
Data Source
AI summary
A dual-motor drive assembly, comprising a housing, a shaft rotatably mounted to the housing, a first gear connected to the shaft, first and second motors, each driving a respective output gear which are engaged with the first gear, a motor controller allocating torque demands to the first and second motors to apply a torque to the first gear, a determination unit for an angular position signal of the first and second motors, and a processing unit receiving the angular position signals when the motor controller allocates a torque demand that produces a differential torque at the shaft having a first sense; the differential torque taking up any free-play between the two output gears and the first gear, receiving the angular position signals—when the motor controller allocates a torque demand that produces a differential torque at the shaft having a second sense, the differential torque taking up any free-play between the two output gears and the first gear, and the processing arrangement estimates the level of backlash in the gearbox as a function of the values of the angular position signals at first and second times.