Electric Axle Motor Torque Control for Cost-Accurate Drive Output
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Solution Overview
Problem
Commercial vehicles with electric axles equipped with high-priced high-performance motors face issues such as torque output errors, limited maximum torque usage time, and increased development and manufacturing costs due to the use of identical high-performance motors for both low and high-output requirements.
Innovation Solution
A motor control system and method that controls the torque of first and second motors in a rear-wheel electric axle, where the first motor approaches target torque in low-output sections and the second motor compensates for errors, and both motors operate at alternating fixed duty ratios in high-output sections, allowing for precise torque delivery and extended maximum-torque usage while differing in precision and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-performance motors are used for both low and high-output requirements, then torque output capability is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies local quality by assigning different motor specifications to different output requirements. The first motor is designed with high-performance characteristics for low-output requirements where precision is critical, while the second motor uses standard-performance characteristics for high-output requirements where maximum torque is needed. This differentiated approach optimizes cost by avoiding over-engineering motors for all applications.
Solution Approach 2:
The patent changes motor parameters based on operating conditions by switching between two different motors. The controller selects which motor to operate based on the current torque requirements, effectively changing the system's motor parameters dynamically. This allows the system to achieve both high precision and high power output without requiring both motors to be high-performance models.
2Measurement precision
If a single high-performance motor is used, then torque precision is improved, but maximum torque usage time is limited
Solution Approach 1:
The patent segments the torque delivery function into two separate motors with different specialization. The first motor handles precision torque delivery for normal operating conditions, while the second motor provides additional torque capacity for high-load situations. This segmentation allows each motor to operate within its optimal performance envelope, extending the overall system's maximum torque usage time.
Solution Approach 2:
The controller implements periodic switching between the two motors based on torque requirements. During low-output requirements, the first motor operates continuously for precise control. During high-output requirements, the controller switches to the second motor or operates both motors in coordination, enabling extended maximum torque usage through periodic alternation.
3Manufacturing precision
If identical high-performance motors are used for both motors, then torque delivery accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies asymmetry by using non-identical motors with different performance characteristics. The first motor is designed with higher precision specifications for accurate torque delivery during normal operation, while the second motor uses standard specifications for providing additional torque capacity. This asymmetric configuration reduces system complexity and cost while maintaining torque delivery accuracy when needed.
Solution Approach 2:
The patent achieves universality by designing a control system that can effectively manage two different motor types. The controller universally handles torque distribution, motor selection, and coordination between the two motors with different specifications. This multi-functional control approach allows the system to maintain torque delivery accuracy across various operating conditions without requiring both motors to be identical high-performance units.
Data Source
AI summary
A motor control system for a commercial vehicle having an electric axle includes: first and second motors disposed in a rear-wheel electric axle; an accelerator position sensor for detecting a degree to which an accelerator is depressed; a wheel speed sensor detecting a wheel speed change; and a controller determining a driver's required torque on the basis of detection signals of the accelerator position sensor and the wheel speed sensor and then controlling a torque of the first motor in such a manner as to approach target torque for satisfying the driver's required torque and at the same time either controlling either a torque of the second motor to a level that compensates for a torque error of the first motor or controlling the torque of the first motor and the torque of the second motor at alternating fixed duty ratios.