Open Differential Wheel Slip Control Under Split Friction
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Solution Overview
Problem
Existing wheel slip control systems in vehicles with open differentials face performance limitations due to latency in communication between actuators, leading to potential loss of traction and actuators 'fighting' each other during split friction scenarios.
Innovation Solution
A system that sets a signed wheel slip limit and activates secondary actuators like service brakes when the wheel slip exceeds this limit, transferring torque to the other wheel to maintain balanced slip across the differential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque control at the actuator level is used to request a certain tyre force, then the braking system can limit vehicle velocity and maintain stability, but significant performance limitations arise due to latencies in communication between different controllers when safety functions request torque override
Solution Approach 1:
The patent merges the primary actuator control and slip control into a single integrated controller. This eliminates the communication latency between separate controllers by consolidating the torque management and slip control functions, allowing real-time response to slip conditions without inter-controller communication delays.
Solution Approach 2:
The integrated controller performs multiple functions including primary torque control, slip detection, and corrective torque application. This multi-functional approach replaces the need for separate specialized controllers, reducing system complexity and communication overhead while maintaining comprehensive slip control capability.
2Speed
If a tyre model is used to convert torque request into wheel slip request for faster control response, then slip control speed improves, but coordination of slip limits across actuators becomes challenging during split friction scenarios leading to loss of traction and actuators fighting each other
Solution Approach 1:
The system applies different slip limits to different wheels based on their individual friction conditions. During split friction scenarios, each wheel receives a customized slip limit appropriate to its local friction coefficient, preventing the actuators from fighting each other while maintaining optimal traction on each wheel.
Solution Approach 2:
The slip limits are dynamically adjusted based on real-time detection of split friction conditions. The controller continuously monitors wheel slip and friction conditions, adapting the slip limits for each actuator to match current road conditions, thereby maintaining reliable traction control during changing scenarios.
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 reduces the risk of actuators fighting each other and maintains effective traction control by dynamically adjusting slip limits based on vehicle conditions.
Implementation Method 1
individual secondary actuators (such as service brakes) for providing additional force (such as friction force) to the individual wheels, respectively
Data Source
Figure 1
Figure 2
Figure 3a~4b
AI summary
The invention relates to a system (104) and to a method executed in a vehicle control unit (110), VCU, for controlling wheel slip of a vehicle, wherein the vehicle comprises at least two wheels (102a, 102b) driven by at least primary actuator (106) via an open differential (108). The primary actuator (106) is controlled to rotate at a speed resulting in a slip λem of the primary actuator (106). 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. Said at least two wheels (102a, 102b) 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.