Powertrain Creep Torque Control via Floor Value Adjustment
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Solution Overview
Problem
Conventional vehicles with internal combustion engines experience unwanted creep forward motion when the accelerator pedal is released, leading to inefficient energy use as the powertrain generates torque, while alternatively powered vehicles attempt to replicate this feel but end up wasting energy by continuously generating torque under foot-off conditions.
Innovation Solution
A powertrain control system that delivers friction torque at a constant value when the vehicle is stationary, reducing powertrain torque commands to a floor value by adjusting the difference between requested and delivered torque, thereby minimizing energy waste and maintaining the feel of a conventionally powered vehicle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the powertrain generates torque under foot-off accelerator pedal conditions to maintain vehicle creep behavior, then the vehicle maintains conventional driving feel, but energy consumption increases unnecessarily
Solution Approach 1:
The system dynamically adjusts powertrain torque output based on vehicle speed conditions. At very low speeds (below threshold speed), the torque is reduced to a floor value even when accelerator pedal is released, while maintaining normal creep torque at higher speeds. This dynamic adaptation resolves the contradiction by providing creep behavior only when necessary for drivability.
Solution Approach 2:
The system changes the torque parameter based on operating conditions. A floor torque value is established that is lower than normal creep torque, and this parameter is applied selectively at low speeds to reduce energy consumption while preserving the perceived creep effect through friction torque management.
2Loss of energy
If friction torque is delivered at a constant value to reduce powertrain torque commands, then energy waste is minimized, but the vehicle may lose natural creep feel
Solution Approach 1:
The system applies different torque management strategies to different components based on local conditions. Friction torque is applied specifically at the wheel level to counteract powertrain torque, while the powertrain itself operates at reduced torque output. This localized application preserves the overall creep feel while reducing the energy burden on the powertrain.
Data Source
AI summary
A vehicle powertrain control system causes friction torque to be delivered to wheels at a generally constant value for a range of increasing requested friction torque values such that commanded powertrain torque values are reduced to a generally constant floor value. The range of increasing requested torque values is less than a requested powertrain torque value under foot off accelerator pedal and vehicle stop conditions.