Suspension Geometry Tuning for Smooth Initial Turn-In Roll
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Solution Overview
Problem
Existing vehicle suspension systems experience mechanical roll during initial turning due to changes in suspension geometry, leading to a complex and unsmooth vehicle posture change, which hinders the driver's sensation of vehicle control.
Innovation Solution
A vehicle suspension system with front and rear suspensions designed to minimize kinematic roll by setting specific geometric parameters: a caster angle between +3° to +5°, caster trail between +20 to +30 mm, and anhedral angle of +2.8° to +7.2° for the front suspension, and a virtual kingpin axis extending near the rear tire contact patch at an angle between −2° to 0° for the rear suspension, using configurations such as double wishbone, strut-type, or multi-link types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional suspension geometry is used, then the suspension structure is simple and easy to manufacture, but kinematic roll occurs during initial turning due to suspension geometry change, causing complex and unsmooth vehicle posture change
Solution Approach 1:
The patent applies parameter changes by precisely defining specific geometric parameters of the suspension system: caster angle between +3° to +5°, caster trail between +20 to +30 mm, and anhedral angle of the lower arm between +2.8° to +7.2°. These parameter optimizations minimize kinematic roll during initial turning while maintaining straightforward suspension architecture, thereby achieving smooth vehicle posture change without increasing device complexity
2Stability of the object's composition
If the caster angle and caster trail are increased to improve straight ahead stability and steering reaction, then the vehicle becomes more stable, but the kinematic roll during initial turning increases, degrading steering response
Solution Approach 1:
The patent resolves this contradiction through optimized parameter changes: setting the caster angle within +3° to +5° and caster trail within +20 to +30 mm. These specific parameter ranges provide sufficient straight ahead stability and steering reaction force while minimizing kinematic roll during initial turning, thereby maintaining both stability and steering response without compromise
3Force
If the kingpin axis intersection point is positioned to improve steering reaction force, then the steering becomes more responsive, but the kinematic roll during initial turning increases, causing vehicle posture to change in a complicated manner
Solution Approach 1:
The patent positions the kingpin axis intersection point on the inner side in the vehicle width direction of the center of the tire contact patch in front view. This specific positional parameter provides adequate steering reaction force while minimizing kinematic roll during initial turning, ensuring that vehicle posture changes smoothly rather than in a complicated manner
4Stability of the object's composition
If the lower arm anhedral angle is increased to improve roll stability, then the vehicle body roll is suppressed, but the kinematic roll during initial turning increases, inhibiting driver sensation of vehicle control
Solution Approach 1:
The patent sets the lower arm anhedral angle within +2.8° to +7.2° in front view. This optimized parameter provides sufficient roll stability during steady-state cornering while minimizing kinematic roll during initial turning, allowing the driver to perceive smooth vehicle posture change and maintain good sensation of vehicle control
Data Source
AI summary
A vehicle suspension system smoothly changes a vehicle posture with respect to a steering force and a steering angle by minimizing a kinematic roll at an initial turning stage, thereby allowing a driver to obtain the sensation of maneuvering the vehicle well. The suspension system includes a front suspension having geometry satisfying that a caster angle is +3° to +5°, a caster trail is +20 to +30 mm, an intersection point between a kingpin axis and ground is located on an inner side in a vehicle width direction of a center of a tire contact patch, and an anhedral angle of a lower arm is +2.8° to +7.2°. A rear suspension includes five links and has geometry satisfying that a virtual kingpin axis extends near the center of a tire contact patch of a rear wheel assembly and extends vertically at −2° to 0°.