Axle Torque Distribution Control for Low-Speed Overrun Traction
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Solution Overview
Problem
On low friction or loose surfaces, the delivery of overrun torque to the drive wheels of a vehicle can cause undesirable slip and lead to the formation of a wedge of material in front of the wheels, which hinders vehicle restart and deceleration, especially at low speeds.
Innovation Solution
A control system that detects when a vehicle is in overrun and adjusts torque distribution between axles by reducing overrun torque on one axle and increasing it on the other, based on vehicle speed, deceleration rate, and surface conditions, using a combination of electric machines and braking systems to maintain consistent deceleration and prevent wedge formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If overrun torque is delivered to the drive wheels, then vehicle deceleration is achieved, but wheel slip and wedge formation occur on low friction surfaces
Solution Approach 1:
The patent segments the torque application by axle, distributing overrun torque differently between front and rear axles based on detected surface conditions. The control system divides the total deceleration torque into portions applied to each axle independently, preventing excessive torque on any single axle that would cause wheel slip and wedge formation on low friction surfaces.
Solution Approach 2:
The patent implements dynamic torque distribution that adjusts in real-time based on vehicle speed, surface conditions, and deceleration rate. The control system continuously monitors parameters and dynamically redistributes torque between axles during the deceleration process, optimizing traction stability while maintaining deceleration effectiveness throughout the speed range.
2Object-generated harmful factors
If overrun torque is reduced on the first axle to prevent wedge formation, then material buildup is reduced, but overall deceleration may be affected
Solution Approach 1:
The patent merges the torque application function across both axles to maintain overall deceleration. When overrun torque is reduced on the first axle to prevent wedge formation, the control system combines torque application on the second axle with the reduced torque from the first axle to achieve the required total deceleration force, ensuring that harmful wedge formation is prevented while maintaining effective speed reduction.
Solution Approach 2:
The control system acts as an intermediary that redistributes torque between axles. It receives the total deceleration requirement, mediates the distribution by reducing torque on the first axle to prevent wedge formation, and compensates by adjusting torque on the second axle, thereby maintaining overall deceleration performance while eliminating the harmful effect.
Data Source
AI summary
Aspects of the present invention relate to a control system for controlling torque distribution between a first axle (110) and a second axle (120) in a vehicle (100), the control system comprising one or more controllers. The control system is configured to detect that the vehicle is in overrun and detect the vehicle speed. When the vehicle is in overrun and the vehicle speed is below a first speed threshold then the torque distribution is controlled to reduce overrun torque to the first axle and to increase overrun torque to the second axle. The vehicle may be a hybrid vehicle comprising an internal combustion engine (ICE) (201), a belt integrated starter generator (B-ISG) (205) and an electric rear axle drive (ERAD) (204).