Virtual Steering Pivot Suspension for In-Wheel Drive Packaging
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Solution Overview
Problem
Electric vehicles face challenges in optimizing wheel steering geometry to minimize the vehicle body envelope, which affects interior space and handling dynamics, especially when using in-wheel electric drive units, leading to poor handling characteristics and increased vehicle size.
Innovation Solution
A suspension and drive mechanism with a five-link configuration that adjusts the virtual steering pivot axis within the wheel width, allowing the electric drive unit to be integrated while minimizing the wheel's steering envelope, using angled control arms and a steering arm to optimize wheel positioning and reduce self-centering effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pivot point is located adjacent to the inside edge of the wheel to maintain steering and handling dynamics, then vehicle handling characteristics are improved, but the envelope required for wheel steering is increased
Solution Approach 1:
The patent implements a variable virtual pivot point that dynamically changes position based on steering angle. At low steering angles, the pivot point is positioned to optimize handling characteristics, while at high steering angles, it shifts to minimize the wheel envelope. This dynamic adjustment resolves the contradiction by allowing the system to have optimal handling at normal steering while reducing envelope at extreme steering positions.
Solution Approach 2:
The patent changes the parameter of pivot point location from fixed to variable. By using a multi-link suspension mechanism with specifically designed arm lengths and pivot positions, the virtual pivot point's location changes as a function of steering angle. This parameter change allows the system to optimize handling at low angles while minimizing envelope at high angles.
2Area of stationary object
If the pivot point is located through the centre of the tyre to minimise the envelope, then the wheel envelope is reduced, but vehicle handling characteristics deteriorate with no self-centering and limited driver feedback
Solution Approach 1:
The patent creates a dynamic pivot point that moves from the wheel center at high steering angles (minimizing envelope) to a position adjacent to the inside edge at low steering angles (providing proper handling characteristics). This dynamic behavior allows the system to achieve both minimal envelope and proper handling, as the pivot point adapts its position based on the steering condition.
3Reliability
If castor angle is increased to promote self-centering action, then directional stability is improved, but hysteresis effect increases in electronically actuated steering configurations
Solution Approach 1:
The patent replaces the traditional mechanical castor angle mechanism with an electronically controlled steering system. The variable virtual pivot point mechanism, controlled by electronic actuators, provides self-centering action without the hysteresis problems of mechanical castor adjustments. This substitution allows for precise electronic control of steering behavior, eliminating the trade-off between self-centering and hysteresis.
Data Source
AI summary
A suspension and drive mechanism for a steerable wheel of a vehicle, comprising a wheel support assembly supporting the wheel having a rolling axis and a wheel width defined by inner and outer wheel edges. Front and rear upper control arms coupled between a chassis and the wheel support assembly, and front and rear lower control arms between the chassis and the wheel support assembly. The front and rear upper control arms being coupled to the wheel support assembly above the rolling axis and inboard of the wheel inner edge, and front and rear lower control arms being coupled to the wheel support assembly below the rolling axis and inboard of the wheel inner edge. The control arms are angled so as to establish a virtual steering pivot axis for the wheel support assembly, the virtual steering pivot axis extending transverse of the rolling axis and located within the width of the wheel. The virtual steering pivot axis location varies according to a steering angle of the wheel support assembly as controlled by the steering arm. An electric drive unit arranged within the wheel for driving thereof, and at least one of the virtual pivots that lie on said virtual steering pivot axis lies within the volume occupied by the electric drive unit during at least one point in the steering travel of said wheel.