Open-Differential Wheel Slip Control for Split-Friction Traction
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Solution Overview
Problem
The existing wheel slip control systems for heavy-duty vehicles with electric machines via open differentials face performance limitations due to latency in communication between torque control and slip control, leading to challenges in coordinating slip limits across actuators during split friction scenarios, which can result in loss of traction and 'fighting' between actuators.
Innovation Solution
A system that sets a signed wheel slip limit and activates secondary actuators, such as service brakes, when the wheel slip exceeds this limit, to transfer torque from one wheel to another, thereby reducing the risk of actuators fighting each other and maintaining traction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If torque control is used at the actuator level for wheel slip control, then a certain tyre force can be requested, but significant performance limitations arise due to latency in communication between torque control and slip control controllers
Solution Approach 1:
The patent combines torque control and slip control into a single integrated controller rather than using separate controllers. This merging eliminates the communication latency between controllers and enables direct, real-time coordination of torque application and slip management, significantly improving slip control performance while reducing response time delays
2Ease of operation
If separate controllers are used for primary actuator control and slip control, then functional separation is achieved, but the latency in communication between them significantly limits slip control performance
Solution Approach 1:
The patent merges the primary actuator controller and slip control into a single integrated controller. This eliminates the communication interface between separate controllers, removing latency delays and enabling real-time coordinated control of both torque application and slip management functions simultaneously
3Reliability
If slip limits are coordinated across actuators during split friction scenarios, then traction can be maintained, but coordination challenges arise when left and right wheels are driven by an electric machine via an open differential
Solution Approach 1:
The patent integrates actuator control and slip limit coordination into a single controller, enabling real-time calculation and adjustment of slip limits for each wheel based on actual slip conditions. This unified approach simplifies the coordination complexity by eliminating communication delays between separate controllers and allows immediate torque redistribution when one wheel loses traction
Solution Approach 2:
The patent implements dynamic slip limit adjustment where the slip limit for each wheel is continuously updated based on real-time slip measurements. When one wheel exceeds its slip limit, the system dynamically redistributes torque to the other wheel by adjusting its slip limit, enabling adaptive traction maintenance without complex predetermined coordination rules
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
This approach effectively reduces the risk of loss of traction and actuator conflict by dynamically controlling wheel slips within predetermined limits, ensuring efficient slip control and stability during varying friction conditions.
Implementation Method 1
individual secondary actuators (such as service brakes) for providing additional force (such as friction force) to the individual wheels
Data Source
AI summary
A system and to a method executed in a vehicle control unit for controlling wheel slip of a vehicle, wherein the vehicle comprises at least two wheels driven by at least primary actuator via an open differential. The primary actuator is controlled to rotate at a speed resulting in a slip λem of the primary actuator. A signed wheel slip limit λlim is determined by adding a configurable value to the slip λem of the primary actuator, such that λlim>λem. The at least two wheels are controlled to rotate at wheel speeds resulting in respective wheel slips λl, λr below the signed wheel slip limit λlim, wherein each one of λl, λr and λem are signed numerical values.