In-Wheel Motor Kingpin Offset Control for Vehicle Stability
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Solution Overview
Problem
In-wheel motor vehicles face instability due to the change in weight distribution during braking and driving, as both driving and braking forces are applied at the same point on the tire, making it difficult to determine the kingpin offset effectively, unlike conventional rear-wheel-drive vehicles where forces are applied at different points.
Innovation Solution
The four-wheel in-wheel motor vehicle determines the kingpin offset based on the distribution of braking and driving forces between the front and rear wheels, adjusting the ratio of kingpin offset to wheel stroke to stabilize vehicle behavior during braking and driving, with different approaches for varying roll center heights and force distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the kingpin offset is set to zero as in conventional in-wheel motor vehicles, then the structure is simplified, but the vehicle becomes unstable during braking and driving due to weight shift
Solution Approach 1:
The patent applies the dynamics principle by making the kingpin offset variable rather than fixed. The kingpin offset is adjusted dynamically based on vehicle operating conditions (braking, driving, straight traveling, cornering) to maintain optimal stability. This is achieved through a control system that calculates the appropriate kingpin offset from sensor data and actuates the suspension system accordingly, transforming a static parameter into a dynamic one that adapts to changing vehicle states.
Solution Approach 2:
The patent implements parameter changes by varying the kingpin offset parameter according to different vehicle operating conditions. The control system modifies the kingpin offset value based on detected vehicle state (braking force, driving force, cornering angle, etc.), thereby changing this critical geometric parameter to optimize vehicle behavior. This allows the same vehicle to exhibit different stability characteristics suitable for each operating mode.
2Stability of the object's composition
If the kingpin offset is increased to improve stability, then vehicle stability improves, but steering effort increases and handling becomes heavy
Solution Approach 1:
The patent resolves this contradiction by making the kingpin offset dynamic. During steady-state conditions (straight traveling), a larger kingpin offset can be used to enhance stability without excessive steering effort. During cornering or maneuvering, the kingpin offset is reduced to facilitate easier steering and better handling responsiveness. This dynamic adjustment allows the system to optimize both stability and ease of operation depending on the immediate driving context.
Solution Approach 2:
The patent changes the kingpin offset parameter based on operating conditions to balance stability and steering ease. When stability is prioritized (straight-line driving), the parameter is set to a larger value. When maneuverability is prioritized (cornering, parking), the parameter is reduced. This conditional parameter adjustment resolves the trade-off by allowing both large and small kingpin offset benefits in different situations.
3Ease of operation
If the ball joint is positioned inward to reduce kingpin offset, then steering effort is reduced, but the suspension geometry becomes complex and difficult to design
Solution Approach 1:
The patent avoids complex fixed suspension geometry by introducing dynamic adjustment capability. Rather than designing a complex fixed ball joint position that achieves optimal kingpin offset, the system uses actuators to dynamically position the ball joint or adjust the kingpin offset. This transforms a complex geometric design problem into a controllable dynamic system, simplifying the overall design while achieving the desired steering characteristics.
Solution Approach 2:
The patent introduces an intermediary control system between the suspension components and the wheel assembly. This control system (including sensors, controllers, and actuators) mediates the relationship between the ball joint position and the effective kingpin offset, allowing independent optimization of steering ease and suspension geometry. The intermediary system calculates and adjusts the kingpin offset based on operating conditions without requiring complex fixed geometric arrangements.
Data Source
AI summary
A four-wheel vehicle is provided with an in-wheel motor in each of a front wheel and a rear wheel and has approximately the same roll center heights of the front wheel and the rear wheel. The relation between a change in a kingpin offset and a change in a wheel stroke for at least any one of the front wheel and the rear wheel of the four-wheel vehicle is determined based on at least any one of braking force distribution and driving force distribution between the front wheel and the rear wheel.