EV Drive Control with Selectable Creep and Brake Torque Blending
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Solution Overview
Problem
Existing drive control systems in electric vehicles do not effectively address the comfort issues related to brake squeaking during creep and do not provide a consistent 'one-pedal feeling' across different driving modes, particularly in hybrid and electric vehicles.
Innovation Solution
A drive control system with an electronic control unit that adjusts creep torque based on driver braking intent and vehicle velocity, deactivating creep in certain gears and reducing torque to minimize brake squeaking, while allowing drivers to select between different driving modes through a gear selector with an automatically restoring toggle switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If creep function is activated in electric vehicle to provide smooth low-speed motion, then driving comfort is improved, but brake squeaking occurs due to conflict between drive torque and friction brake
Solution Approach 1:
The system dynamically adjusts the creep torque based on detected braking intent. When braking is detected, the creep torque is reduced or deactivated, allowing the friction brake to operate without conflict. This dynamic adaptation eliminates brake squeaking while preserving creep functionality during normal operation.
Solution Approach 2:
The control unit continuously monitors brake pedal position and braking signals to detect driver braking intent. This feedback mechanism allows the system to recognize when the driver intends to brake and automatically adjusts the creep torque accordingly, preventing the torque conflict that causes squeaking.
2Loss of energy
If high recuperation torque is applied during deceleration in 'B' gear, then energy recovery is improved, but brake squeaking increases due to higher friction brake engagement
Solution Approach 1:
The system dynamically balances recuperation torque and friction brake torque based on braking intensity. For mild braking, high recuperation is maintained for maximum energy recovery. For stronger braking, the system progressively reduces recuperation torque and increases friction brake contribution, preventing squeaking while maintaining energy efficiency.
Solution Approach 2:
The control system changes the distribution parameter between recuperation torque and friction brake torque based on braking intent. By adjusting this parameter dynamically, the system optimizes energy recovery during light braking while preventing squeaking during stronger braking maneuvers.
3Speed
If creep torque is maintained at high level during driver braking intent, then deceleration control is improved, but braking comfort deteriorates due to unsteady deceleration
Solution Approach 1:
The system dynamically reduces creep torque in proportion to detected braking intent, creating a smooth transition from creep mode to braking mode. This dynamic adjustment ensures steady deceleration without abrupt changes, maintaining both deceleration control and braking comfort.
Solution Approach 2:
The system anticipates the need to reduce creep torque by detecting braking intent early through brake pedal monitoring. By proactively reducing creep torque before full brake application, the system prevents unsteady deceleration and ensures smooth braking comfort from the outset.
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 vehicle comfort by reducing brake squeaking and providing a consistent 'one-pedal feeling' by adjusting creep torque based on driver input, improving the driving experience in electric vehicles.
Implementation Method 1
motor vehicle operable by electric motor
Implementation Method 2
friction brake system
Implementation Method 3
maximum possible recuperation torque
Data Source
AI summary
A drive control system for a motor vehicle able to be operated by an electric motor and having a drive stage selector, an electronic accelerator pedal, a brake pedal, and an electronic control unit that is configured such that a creep function is deactivated when a first alternative automatic drive stage is selected, and that a creep function is activated when a second alternative automatic drive stage is selected. The control unit furthermore contains an appropriately programmed function module by way of which, when the creep function is activated and based on creep pilot control, the creep moment predefined thereby, in the form of a drive moment, is reduced based on a braking request from the driver, wherein a frictional braking moment is activated by the conventional wheel brake system only when the minimum possible creep moment is reached.