Vehicle Dynamics Control Handling Assurance Acceleration Limit
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Solution Overview
Problem
Existing vehicle dynamics control systems face challenges in maintaining optimal vehicle stability and drivability, particularly when encountering low road friction coefficients, as they often result in excessive wheel skidding and poor handling during automatic deceleration, especially in electric vehicles.
Innovation Solution
A vehicle dynamics control device that executes braking or driving torque control based on environmental and vehicle information, including driver input, to set a handling assurance acceleration limit, ensuring optimal longitudinal and lateral force distribution without excessive skidding, by using a control unit that considers lateral motion operations and friction force limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If automatic deceleration control is executed to achieve optimal speed for avoiding collision or negotiating curves, then the vehicle can maintain safe operating speed, but the wheels may skid to an excessive extent particularly on low friction surfaces
Solution Approach 1:
The control device dynamically adjusts the deceleration command value by multiplying it with a correction factor that is determined based on the estimated road surface friction coefficient. When friction is low, the correction factor reduces the deceleration magnitude to prevent wheel skidding, while maintaining collision avoidance capability. This parameter adjustment resolves the contradiction between achieving reliable collision avoidance and preventing excessive wheel skidding on low-friction surfaces.
2Use of energy by moving object
If regenerative braking control applies greater braking force to rear wheels to maximize energy regeneration, then energy recovery is improved, but the rear wheels may skid to an excessive extent compromising vehicle stability
Solution Approach 1:
The control device adjusts the braking force distribution between front and rear wheels based on the estimated road surface friction coefficient. On low-friction surfaces, it reduces the magnitude of braking force applied to rear wheels during regenerative braking, preventing excessive skidding and maintaining vehicle stability. This dynamic parameter adjustment allows the system to maintain energy recovery capability while adapting to friction conditions to preserve vehicle dynamics stability.
3Productivity
If the handling assurance acceleration limit is set high to achieve rapid deceleration, then collision avoidance effectiveness is improved, but vehicle responsiveness to steering operations deteriorates
Solution Approach 1:
The control device dynamically adjusts the handling assurance acceleration limit based on the estimated road surface friction coefficient and current vehicle operating conditions. When friction is low or during steering operations, it reduces the acceleration limit to maintain steering responsiveness and vehicle controllability. When friction is high and no steering input is detected, it increases the limit to achieve rapid deceleration for collision avoidance. This dynamic parameter adjustment resolves the contradiction between deceleration effectiveness and steering responsiveness.
Data Source
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AI summary
A vehicle dynamics control device includes: a control unit that executes braking/driving torque control for controlling at least either a braking torque or a driving torque at each wheel based upon at least either external information pertaining to an environment of a vehicle or vehicle information that includes operation input information indicating an operation input by a driver and a vehicle dynamics information. And the operation input information includes a lateral motion operation index pertaining to a lateral motion operation executed to generate a lateral motion in the vehicle; the vehicle dynamics information includes a longitudinal acceleration generated in the vehicle and a lateral motion index indicating a lateral motion occurring in the vehicle; and the control unit determines a handling assurance acceleration limit with a maximum longitudinal acceleration value that assumes a substantially linear proportional relationship with the lateral motion operation index and the lateral motion index over a range in which the lateral motion operation index assumes a value equal to or less than a predetermined value or the lateral motion index assumes a value equal to or less than a predetermined value, and executes the braking/driving torque control by setting the handling assurance acceleration limit as an upper limit to a longitudinal acceleration to be generated in the vehicle under the braking/driving torque control.