In-Wheel EV Lateral-Vertical Control Under Nonlinear Tire Loads
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing in-wheel motor drive systems for electric vehicles face issues with unbalanced magnetic forces affecting ride comfort, tire-road contact, and handling stability due to unconsidered nonlinear tire characteristics and linear tire models, leading to poor control performance under extreme conditions.
Innovation Solution
A 14-DOF full-vehicle model is constructed, combined with a three-dimensional piecewise-affine tire model and hybrid model predictive control for active front-wheel steering, and a multi-constraint active suspension system to integrate lateral and vertical control, addressing unbalanced magnetic forces and nonlinear tire behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a linear tire model is used for lateral dynamics control, then the controller design is simplified, but the control accuracy deteriorates under nonlinear or saturated tire conditions
Solution Approach 1:
The tire model is segmented into multiple linear regions based on operating conditions (normal, saturated, extreme). Each region has its own linear parameters, allowing the controller to switch between different linear models depending on the current tire state, thus maintaining simplicity while improving accuracy across different operating conditions.
Solution Approach 2:
The tire model parameters are made dynamic rather than static. The controller continuously identifies the current operating region and adjusts the tire model parameters in real-time based on measured vehicle states and tire conditions, enabling the system to adapt to changing nonlinear characteristics without requiring a completely complex nonlinear model.
2Device complexity
If in-wheel motors are used to simplify vehicle structure and improve transmission efficiency, then the drive system complexity is reduced, but the lateral-vertical dynamic performance deteriorates due to increased unsprung mass and unbalanced magnetic forces
Solution Approach 1:
The control systems for lateral dynamics and vertical dynamics are merged into a single integrated control framework. The controller simultaneously considers both lateral stability (handling) and vertical performance (ride comfort, unbalanced magnetic force mitigation) by coordinating the control actions of the suspension system and steering system, thereby improving overall dynamic performance without adding physical complexity to the drive system.
Solution Approach 2:
The system implements feedback control by continuously monitoring vehicle states (acceleration, orientation, tire forces) and adjusting the suspension and steering commands in real-time. This feedback mechanism compensates for the adverse effects of increased unsprung mass and unbalanced magnetic forces, maintaining stable lateral-vertical dynamics despite the simplified in-wheel motor drive structure.
3Ease of operation
If body roll is allowed under turning conditions, then the vehicle maintains natural handling characteristics, but the stator-rotor eccentricity increases, intensifying unbalanced magnetic forces and deteriorating lateral dynamic performance
Solution Approach 1:
The controller applies preliminary anti-action by proactively counteracting the body roll that would naturally occur during turning. Before the roll becomes excessive and causes significant stator-rotor eccentricity, the active suspension system pre-adjusts the wheel positions and the steering system makes compensatory adjustments to maintain optimal motor alignment, thereby preventing the intensification of unbalanced magnetic forces while preserving natural handling.
Data Source
AI summary
A method for lateral-vertical integrated control of a distributed in-wheel motor drive electric vehicle is provided, in which a fourteen-degree-of-freedom full-vehicle model is constructed based on an unbalanced magnetic force model of an in-wheel motor; a lateral force-tire slip angle-vertical load-based three-dimensional piecewise-affine tire model is constructed based on the fourteen-degree-of-freedom vehicle model in combination with a corrected Magic Formula tire model; an active front-wheel steering controller is established based on hybrid model predictive control using the three-dimensional piecewise-affine tire model; an active suspension system controller is established based on multi-constraint input and multi-constraint output; and an integrated control strategy for the active front-wheel steering controller and the active suspension system controller is established based on a front-wheel steering angle, a β-{dot over (β)} phase plane and a lateral load transfer rate. Related devices for implementing such method are also provided.