Wheel Slip Balanced Drive for Efficient Heavy-Duty EV Braking
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Solution Overview
Problem
Heavy-duty electric vehicles face challenges in energy efficiency and endurance braking, particularly due to high computational complexity of existing drive arrangements and the risk of brake fading during prolonged use, which limits their ability to maintain efficient operation and control temperature during regenerative braking.
Innovation Solution
A vehicle control unit that balances wheel slip between multiple electric machine arrangements based on their efficiency characteristics, allowing for optimized propulsion and braking by varying slip requests rather than torque requests, thereby maintaining efficiency and controlling temperature effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If advanced optimization methods are used to optimize joint propulsion system efficiency, then energy efficiency is improved, but computational complexity increases and robustness verification becomes difficult
Solution Approach 1:
The patent changes the control parameter from torque distribution to wheel slip distribution. This parameter transformation simplifies the optimization problem while maintaining energy efficiency benefits, as wheel slip directly relates to traction conditions and can be optimized using simpler control algorithms that are easier to verify for robustness
Solution Approach 2:
The patent applies different wheel slip targets to different axles based on their individual efficiency characteristics and local conditions. Each axle is controlled with specific wheel slip values tailored to its efficiency map, allowing localized optimization without requiring complex global optimization algorithms
2Force
If friction brakes are used for prolonged periods, then braking capability is maintained, but brake fading occurs and reliability decreases
Solution Approach 1:
The patent enables continuous regenerative braking by electric machines during downhill driving, replacing friction brakes as the primary braking mechanism. This continuous use of regenerative braking prevents friction brake fading while maintaining braking capability, as the electric machines can operate indefinitely without thermal degradation
Solution Approach 2:
The patent converts the normally wasteful energy dissipation during braking into useful energy recovery. By using electric machines to generate electricity during regenerative braking instead of dissipating energy as heat through friction brakes, the system turns energy loss into energy storage, preventing brake fading while extending vehicle range
3Use of energy by moving object
If regenerative braking is used to recover energy, then energy efficiency is improved, but energy storage systems reach full charge and brake resistors overheat
Solution Approach 1:
The patent dynamically adjusts the braking strategy by switching between regenerative braking and friction braking based on real-time conditions. When energy storage is full or brake resistors are hot, the system automatically transitions to friction braking supplementation, and when conditions favor regenerative braking, it maximizes energy recovery, creating a dynamic balance that prevents thermal issues while maintaining energy efficiency
Data Source
AI summary
A vehicle control unit arranged to control motion of a heavy-duty vehicle comprising first and second electric machine (EM) arrangements, wherein the vehicle control unit is arranged to control the first and second EM arrangement by transmitting wheel slip requests to respective EM control units, wherein the control unit is arranged to obtain a desired total longitudinal force to be jointly generated by the first and second EM arrangements, wherein the control unit is arranged to determine a desired first wheel slip corresponding to a first longitudinal force generated by the first EM arrangement, and a desired second wheel slip corresponding to a second longitudinal force generated by the second EM arrangement, wherein the control unit is arranged to balance a magnitude of the first wheel slip relative to a magnitude of the second wheel slip in dependence of the efficiency characteristics of the first and second EM arrangements.