Independent Wheel Torque Control for Tight Vehicle Cornering
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Solution Overview
Problem
Conventional motor vehicles with multiple drive wheels and electric machines struggle to achieve optimal cornering behavior, particularly at maximum steering angles, as they are limited by the geometric constraints of the steering geometry, leading to potential slipping and reduced maneuverability.
Innovation Solution
The method involves determining wheel-specific target speeds and torque distribution based on current vehicle speed, steering angle, chassis geometry, and wheel loads, allowing for a tighter curve radius than geometrically possible, with individual drive wheel control to manage slip and traction, and adaptive speed adjustments according to driving conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional steering geometry is used to determine target curve path, then the vehicle follows the geometrically predetermined path, but the vehicle cannot achieve tighter curve radii and experiences slipping at maximum steering angles
Solution Approach 1:
The patent replaces the mechanical constraint of steering geometry with an electronic control system that independently determines target speeds for each drive wheel. Instead of relying on the physical steering mechanism to define the curve path, the control device calculates optimal wheel speeds based on desired curve radius, enabling the vehicle to achieve tighter turns without being limited by steering angle geometry.
Solution Approach 2:
The patent changes the operating parameters of the drive wheels by independently controlling their speeds rather than maintaining equal speeds. By allowing different rotational speeds between left and right drive wheels during cornering, the system achieves tighter curve radii and prevents slipping, transforming the vehicle's cornering behavior from geometry-constrained to control-parameter-driven.
2Device complexity
If all drive wheels are controlled to maintain equal speeds, then the vehicle structure is simpler, but the vehicle cannot achieve optimal cornering behavior and experiences wheel slip
Solution Approach 1:
The patent segments the control of each drive wheel independently, assigning a specific target speed to each wheel based on its position and the desired curve path. This segmentation allows the inner wheels to rotate slower and outer wheels to rotate faster during cornering, optimizing traction and preventing slip while maintaining manageable control system complexity through modular speed assignment.
3Speed
If the vehicle operates at low speeds with high maneuverability, then the vehicle can navigate tight spaces, but directional stability at higher speeds may be compromised
Solution Approach 1:
The patent implements dynamic speed control that adapts to the vehicle's operating conditions. The control device continuously adjusts target speeds for each drive wheel based on current vehicle speed, steering angle, and desired curve radius, enabling the system to optimize both maneuverability at low speeds and directional stability at higher speeds through real-time parameter adaptation.
Data Source
Figure 1~2
AI summary
The invention relates to a method for operating a motor vehicle (1) which has multiple drive wheels (4-7) and multiple drive machines (8-11), wherein each drive wheel (4-7) is paired with a respective drive machine (8-11), in particular an electric machine. The method has the following steps: - detecting a total target drive torque, - detecting a current vehicle speed, a current steering angle, and optionally the wheel loads of all of the drive wheels (4- 7), - determining wheel-individual movement speeds of the drive wheels (4- 7) over the roadway depending on the current vehicle speed, the current steering angle, a known body geometry of the motor vehicle (1), and optionally the wheel loads, - determining a target rotational speed for each drive wheel (4-7) depending on the determined movement speeds and distributing the total target drive torque to all of the drive wheels (4- 7) such that an actual curved path deviates from a target curved path specified by the steering angle, and - actuating each drive machine (8-11) in order to adjust a target rotational speed of each drive wheel (4-7).