Torque Distribution Control for Vehicle Posture Stability
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Solution Overview
Problem
Motor vehicles experience a forward tilt posture during transitions from an accelerator ON state to an accelerator OFF and brake OFF state due to inadequate adjustment of rear wheel torque distribution ratios, leading to instability and potential braking force control issues.
Innovation Solution
A control unit dynamically adjusts the rear wheel torque distribution ratio from a smaller value during accelerator ON state to a larger value during the transition, and then to a value determined by the vehicle's gravity center position for stable parking, thereby stabilizing the vehicle's posture and ensuring proper braking force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the rear wheel demand distribution ratio is directly changed from a value during accelerator ON state to a value during accelerator OFF and brake OFF state, then the vehicle posture control is simplified, but the vehicle becoming the forward tilt posture cannot be sufficiently suppressed
Solution Approach 1:
The patent applies dynamics by making the rear wheel demand distribution ratio changeable over time rather than fixed. The control unit dynamically adjusts the distribution ratio in three stages: maintaining the initial ratio during accelerator ON state, switching to a first prescribed ratio (larger than initial) during transition to suppress forward tilt, and finally switching to a second prescribed ratio (smaller than first) during accelerator OFF and brake OFF state. This dynamic adjustment resolves the contradiction by adapting the control strategy to different operating phases.
Solution Approach 2:
The patent applies preliminary action by introducing an intermediate state (first prescribed distribution ratio) before reaching the final state (second prescribed distribution ratio). During the transition period, the control unit first increases the rear wheel demand distribution ratio to a larger first prescribed ratio to proactively suppress the forward tilt posture that is likely to occur, before subsequently reducing it to the final smaller ratio. This preliminary protective action prevents the instability issue while maintaining control flexibility.
2Stability of the object's composition
If the rear wheel demand distribution ratio is set to a larger value during transition, then the forward tilt posture is suppressed, but the braking force control precision may be reduced
Solution Approach 1:
The patent resolves this contradiction through dynamic adjustment of the rear wheel demand distribution ratio based on the operational phase. During the transition period when forward tilt is likely, the ratio is increased to a first prescribed value (larger than initial) to ensure posture stability. However, during the final accelerator OFF and brake OFF state, the ratio is reduced to a second prescribed value (smaller than first) to restore precise braking force control. This time-varying strategy ensures both posture suppression and control precision are maintained at appropriate times.
Solution Approach 2:
The patent applies periodic action by dividing the operational transition into distinct phases with different distribution ratio settings. The control unit periodically switches between three states: (1) initial ratio during accelerator ON, (2) first prescribed ratio during transition phase to suppress forward tilt, and (3) second prescribed ratio during accelerator OFF and brake OFF state for precise braking control. This phased approach ensures that the larger ratio is applied only when necessary for posture stability, while precision control is restored when the transition is complete.
Data Source
AI summary
A motor vehicle is controlled: during a prescribed transition from an accelerator ON state to an accelerator OFF and brake OFF state, the control unit makes a rear wheel distribution ratio that is a ratio of a torque of the rear wheel to a sum of a torque of the front wheel and the torque of the rear wheel, change to a first prescribed distribution ratio after changing from a value during the accelerator ON state to a second prescribed distribution ratio that is larger than the first prescribed distribution ratio.