Dual Motor Drive Assembly for Gearbox Friction Estimation
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Solution Overview
Problem
Existing dual motor drive assemblies in steer-by-wire systems face challenges in accurately measuring and managing friction within the gearbox, which affects the system's performance and reliability, particularly due to varying load-dependent and constant friction components.
Innovation Solution
A dual motor drive assembly with a control circuit that allocates independent torque demands to each motor to apply a net torque, including equal and opposite offset components, allowing the processing circuit to estimate load-independent mechanical friction by varying torque differences and observing the lowest net torque required to maintain constant shaft velocity, thereby determining both constant and load-dependent friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual motor drive system is used to reduce gear rattle and provide redundancy, then system reliability is improved, but device complexity increases
Solution Approach 1:
The steering actuator is divided into two independent motor-gear units (first motor with first gear, second motor with second gear) that work together to drive the steering wheel. Each motor-gear combination can operate independently or in coordination, providing redundancy and reliability while maintaining manageable complexity through modular segmentation
Solution Approach 2:
The control system dynamically adjusts the torque parameters of individual motors based on operating conditions, friction levels, and load requirements. By changing motor torque parameters in real-time, the system optimizes performance and reliability while adapting to varying operational demands
2Measurement precision
If friction compensation is implemented to improve steering accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The control circuit continuously monitors the torque demands applied to each motor and the resulting shaft velocity, using this feedback information to calculate and compensate for friction effects. The system measures the actual friction by observing motor behavior under controlled torque conditions and uses this information to adjust control signals, improving measurement precision while managing complexity through intelligent feedback loops
Solution Approach 2:
The dual motor system uses its own operational characteristics to self-diagnose and self-compensate for friction. By analyzing the torque-velocity relationship of the motors during normal operation, the system automatically determines friction levels and adjusts its control strategy without requiring external measurement devices or complex additional hardware
3Measurement precision
If torque offset components are applied to estimate friction, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The system applies partial torque offset components only when friction measurement and compensation are required, rather than continuously. During normal steering operation, the motors operate with minimal additional torque to reduce energy consumption. The torque offset is activated selectively during specific phases (such as startup, idle periods, or when measurement accuracy is prioritized), balancing measurement precision needs with energy conservation
Data Source
AI summary
A dual motor drive assembly can include a housing, a shaft rotatably mounted with respect to the housing, a first gear connected to and configured to rotate with the shaft, first and second motors, each having an output driving a respective output gear, the output gears being engaged with the first gear. The dual motor drive assembly can also include a control circuit which is adapted to allocate independent torque demands to each of the first and second motors to cause a net torque to be applied to the shaft.