Drive Unit Torque Control via Brake Pedal Actuation
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Solution Overview
Problem
Modern brake energy recuperation systems in vehicles with automatic or automated transmissions terminate energy recovery too early, leading to reduced energy efficiency and unpleasant driver experience due to uncontrolled transition from drag to creep torque.
Innovation Solution
A method to control drive unit torque in overrun mode by actuating the brake pedal, allowing for reduced drag or creep torque application, using either recuperation torque from an electric motor or reduced drive motor torque, with adjustable torque levels based on brake pedal actuation and speed, enabling energy recovery up to vehicle stop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If brake energy recuperation is terminated before the transition into creep mode to avoid driver irritation, then driver comfort is improved, but energy recovery efficiency is reduced
Solution Approach 1:
The patent applies dynamics by making the brake pedal characteristic curve speed-dependent and torque-dependent. The system dynamically adjusts the relationship between brake pedal actuation and braking torque based on current vehicle speed and drive torque conditions. This allows the recuperation to continue into the creep mode range by adapting the brake pedal sensation to match driver expectations at different operating conditions, thereby improving energy recovery efficiency while maintaining driver comfort.
Solution Approach 2:
The patent changes parameters by modifying the brake pedal characteristic curve based on speed and torque conditions. The control system adjusts the effective brake pedal curve to account for the speed-dependent and torque-dependent characteristics of the drive unit. This parameter adaptation enables the system to extend recuperation into the creep mode range while preserving pleasant brake sensation for the driver.
2Loss of energy
If the drive torque is made speed-dependent and torque-dependent to improve energy recovery, then energy efficiency is improved, but control complexity increases
Solution Approach 1:
The patent applies universality by using a single brake pedal control interface to achieve multiple functions: traditional braking, creep mode control, and extended energy recuperation. The brake pedal serves as a universal control element that, through dynamic characteristic curve adjustment, manages different operating modes (deceleration, creep, and energy recovery) without requiring separate control mechanisms, thereby managing complexity while improving energy efficiency.
Solution Approach 2:
The patent uses feedback by continuously monitoring vehicle speed and drive torque conditions to dynamically adjust the brake pedal characteristic curve. The control system receives feedback about the current operating state and adapts the brake pedal response accordingly, enabling the drive torque to be speed-dependent and torque-dependent while maintaining manageable control complexity through closed-loop adaptation.
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
Enhances energy recovery efficiency and driver comfort by expanding the range of brake pedal actuation for torque control, allowing for smooth transition to stop mode while maintaining energy efficiency and pleasant brake sensation.
Implementation Method 1
an electric motor converts the kinetic energy in overrun mode and/or on application of the brake into electric energy
Implementation Method 2
electric energy that can then be stored in an energy accumulator (energy storage device)
Data Source
AI summary
A method is provided for controlling a drive unit of a motor vehicle with an automatic or automated transmission. The drive unit includes at least one drive motor, which generates a drive torque in an overrun mode. The drive torque acts as a drag torque or as a creep torque on the drive wheels as a function of the current speed. The level of the drive torque in the overrun mode can be at least partially controlled by actuating a brake pedal. The drag torque applied to the drive wheels in the overrun mode can be controlled by actuating the brake pedal in such a way that a reduced drag torque dependent on the actuation of the brake pedal is applied to the drive wheels.