EV Drivetrain Pre-Loading to Reduce Rollback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electric vehicle drivetrains experience delays and increased rollback due to inherent mechanical slack, particularly noticeable in Hill Hold control scenarios, leading to less responsive vehicle performance.
Innovation Solution
A system that pre-loads the drivetrain by applying a small amount of torque when the vehicle is stationary, eliminating slack and allowing for immediate torque application, thereby reducing rollback and enhancing responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the drivetrain components are coupled with inherent slack to allow mechanical flexibility, then the drivetrain can accommodate mechanical tolerances and misalignments, but torque application to the wheels is delayed during vehicle launch and hill hold scenarios
Solution Approach 1:
The controller applies a pre-load torque to the drivetrain before the vehicle needs to move or before hill hold control is activated. This preliminary action takes up the mechanical slack in the drivetrain components in advance, so that when torque is subsequently applied for vehicle launch or hill hold, there is no delay caused by slack needing to be taken up. The pre-load torque is applied when the vehicle is stationary and the driver is holding the vehicle with service brakes.
2Speed
If pre-load torque is applied to eliminate drivetrain slack, then vehicle rollback is reduced and drive responsiveness is improved, but additional energy is consumed during stationary periods
Solution Approach 1:
Instead of applying full torque continuously, the controller applies only a small pre-load torque sufficient to take up the mechanical slack in the drivetrain. This partial action is adequate to eliminate the slack and improve responsiveness without consuming excessive energy during stationary periods. The pre-load torque is significantly less than the full torque required for vehicle acceleration.
Solution Approach 2:
The pre-load torque is applied periodically or conditionally based on vehicle operating states (when the vehicle is stationary and service brakes are engaged), rather than continuously. The controller monitors vehicle conditions and applies pre-load torque only when needed, thereby reducing overall energy consumption while maintaining responsiveness when required.
3Measurement precision
If the motor transitions between different operating modes to manage drivetrain loading, then vehicle control precision is improved, but control system complexity increases
Solution Approach 1:
The controller divides motor operation into distinct modes (first mode for normal accelerator-responsive operation, second mode for pre-loading the drivetrain, and third mode for maintaining stationary position). By segmenting the control into discrete modes with specific entry and exit conditions, the system achieves precise control over drivetrain loading while managing complexity through clear mode transition logic based on easily detectable vehicle states.
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
The pre-loading system minimizes vehicle rollback and improves drive responsiveness by reducing mechanical lag and abrupt load changes, resulting in faster and smoother vehicle responses.
Implementation Method 1
the motor is controlled to output torque sufficient to preload the electric vehicle
Implementation Method 2
applying a small amount of pre-loading torque to the drivetrain in-order to eliminate slack in the components
Implementation Method 3
a brake is engaged
Data Source
AI summary
Pre-loading drivetrain to minimize electric vehicle rollback and increase drive responsiveness. In an exemplary embodiment, a method includes (a) detecting that an electric vehicle is stationary, a brake is engaged, and an accelerator is not engaged, and (b) controlling a vehicle motor to transition from a first mode to a second mode in response to (a). In the first mode, the motor is controlled to output torque in response to the accelerator position, and in the second mode, the motor is controlled to output torque sufficient to preload the electric vehicle. The method also includes (c) detecting the brake is transitioning away from being engaged and the accelerator is not engaged, and (d) controlling the motor to operate in a third mode in response to (c). In the third mode the motor is controlled to output torque sufficient to maintain the electric vehicle stationary.