One-Pedal Drive Torque Rate Limiting for EV Rollback Prevention
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Solution Overview
Problem
In one-pedal driving mode of electric vehicles, the standard filters and rate limits used in two-pedal mode do not provide acceptable performance at low speeds, leading to delayed torque blending from negative stopping torque to zero, potential rollback, and powertrain bumps or slow responses when transitioning into or out of friction braking.
Innovation Solution
A vehicle controller is programmed to selectively brake using an electric machine based on the accelerator pedal position, applying unique sets of filter constants and rate limits for one-pedal drive mode, including different limits when the brake pedal is applied or released, to enhance responsiveness and prevent rollback or powertrain bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If standard filters and rate limits are used in one-pedal drive mode, then the system maintains simplicity and consistency with two-pedal mode, but the vehicle exhibits delayed torque blending, potential rollback, and slow response at low speeds
Solution Approach 1:
The patent applies dynamics by making the filter constants and rate limits adjustable based on vehicle operating conditions. Specifically, the system switches between different filter constants (first filter constant for high speed, second filter constant for low speed) and different rate limits (first rate limit for high speed, second rate limit for low speed) depending on whether the vehicle speed exceeds a threshold. This dynamic adaptation enables responsive acceleration and deceleration at low speeds while maintaining stable operation at high speeds, resolving the contradiction between responsiveness and complexity.
2Speed
If a single rate limit is applied regardless of speed, then the control logic remains simple, but the vehicle experiences slow torque response and delayed blending at low speeds
Solution Approach 1:
The patent implements parameter changes by modifying the rate limit parameter based on vehicle speed. When the vehicle speed is greater than a threshold, the system applies a first rate limit; when the speed is less than the threshold, it applies a second rate limit that is higher than the first. This parameter adaptation allows faster torque response and quicker blending at low speeds while maintaining appropriate control at high speeds, effectively resolving the contradiction between torque response speed and control complexity.
3Reliability
If high filter constants are used for fast response, then torque blending becomes rapid, but the system becomes unstable and produces powertrain bumps at high speeds
Solution Approach 1:
The patent applies local quality by using different filter constants for different speed regions. When the vehicle speed is greater than a threshold, the system uses a first filter constant that provides stable, conservative torque blending. When the speed is less than the threshold, it switches to a second filter constant that is lower than the first, enabling faster torque blending without causing instability or powertrain bumps. This localized parameter adaptation resolves the contradiction between stability and blending speed by optimizing the filter constant for each operating condition.
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 allows for faster and more responsive acceleration and deceleration, preventing rollback and powertrain bumps, and ensuring smooth transitions during one-pedal driving by adjusting torque modification filters and rate limits based on vehicle speed and brake pedal input.
Implementation Method 1
an electric machine configured to power driven wheels
Implementation Method 2
capable of regenerative braking to recharge the battery by converting mechanical power into electrical power
Data Source
AI summary
A vehicle includes a powertrain having an electric machine configured to power driven wheels, an accelerator pedal, and a brake pedal. A controller is programmed to, in response to driver-demanded torque corresponding to a position of the accelerator pedal, selectively brake the vehicle via operation of the electric machine, in further response to a speed of the vehicle being greater than a threshold, limit a rate of change of the driver-demanded torque commanded to the powertrain based on a first rate limit, and, in further response to the speed being less than another threshold, limit a rate of change of the driver-demanded torque commanded to the powertrain based on a second rate limit that is higher than the first rate limit such that, for a given driver-demanded torque, acceleration and deceleration of the vehicle is more responsive than when the first rate limit is applied.