Vehicle Control System Torque Transition Management
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Solution Overview
Problem
The transition from Vehicle Launch Assist (VLA) to Traction Control (TC) functions in powertrain systems often results in an undesirable high rate of torque increase, leading to wheel slip issues, especially at lower speeds and in terrain conditions like sand, where the TC function may not intervene promptly enough to prevent wheel spin.
Innovation Solution
A vehicle control system that calculates and compares two maximum torque values - one based on the driver's accelerator request and another as a filtered representation - to limit torque applied to the wheels, ensuring a smoother transition between VLA and TC functions by outputting a powertrain drive signal based on the lesser of these values, thereby controlling torque delivery effectively across different speed and terrain conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the VLA function is exited and the powertrain control system switches to TC function as vehicle speed increases, then the torque limit switches from the maximum allowed by VLA to a much larger value from TC, but this results in an high rate of torque increase that is undesirable and may exceed the TC function torque profile
Solution Approach 1:
The patent applies dynamics by making the torque limit adjustable and continuous rather than fixed. The torque limit is dynamically modified based on vehicle speed, transitioning smoothly from VLA-appropriate limits to TC-appropriate limits. This dynamic adjustment prevents abrupt changes and ensures the rate of torque increase remains within acceptable profiles throughout the transition.
Solution Approach 2:
The patent changes the parameter of torque limit continuously as vehicle speed increases. Instead of an abrupt switch between VLA and TC torque limits, the system modifies the torque limit parameter progressively, ensuring that the transition maintains a controlled rate of torque increase that does not exceed the TC function torque profile.
2Productivity
If the VLA function is exited at lower speeds, then the system switches to TC function, but where driver torque demand has gone away by the time of transition, this approach may result in an increasing torque occurring during this transition period even though the drive torque demand has ended
Solution Approach 1:
The patent uses feedback by continuously monitoring the driver's torque demand and comparing it with the current torque limit. During the transition from VLA to TC function, the system checks whether driver torque demand is still present before allowing torque to increase. This feedback mechanism prevents torque increase when the driver has released the accelerator, ensuring torque control accuracy and reliability.
Solution Approach 2:
The patent applies preliminary action by checking the driver's torque demand status before allowing the torque limit to increase during the VLA to TC transition. The system proactively prevents torque increase if the driver has already released the accelerator, avoiding unnecessary torque application and ensuring smooth, demand-appropriate transitions.
Data Source
AI summary
A system and method for use with a vehicle to provide a vehicle launch assist (VLA) function that reduces wheel slip at lower speeds and to provide a fraction control (TC) function that reduces wheel slip at higher speeds. Each function affects operation of one or more vehicle subsystems that control at least one powertrain parameter. The VLA and TC functions operate in response to a driver accelerator request to generate a drive signal that controls torque delivered to at least one driven vehicle wheel. The VLA function generates the drive signal at a first value that limits the torque to below a requested torque value representing the driver accelerator request. The TC function generates the drive signal at a second value that limits the torque to below the requested torque value. And the control system outputs a powertrain drive signal based on the lesser of first and second values.