Vehicle Slip Angle Control with Dynamic Second Derivative Adjustment
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Solution Overview
Problem
Existing vehicle stability control systems face delays in responding to destabilizing turning state quantities, leading to potential vehicle spinning, as they rely solely on first and second derivatives of the vehicle body slip angle without adjusting for abrupt steering conditions.
Innovation Solution
A vehicle behavior control apparatus that calculates a control amount based on the vehicle body slip angle, its derivative, and second derivative, with the contribution of the second derivative being reduced or ignored during abrupt steering to prevent early weakening of spin restraint control, using a formula like K1·β+K2·dβ/dt+K3·d2β/dt2, where K3's value is adjusted to reflect valid contributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the second derivative of the vehicle body slip angle is always included in the control amount calculation, then the response speed to abrupt steering is improved, but the control operation is weakened or nullified during abrupt steering maneuvers
Solution Approach 1:
The patent applies dynamics by making the contribution of the second derivative dynamic rather than static. The control amount calculation changes based on the vehicle's steering state: during abrupt steering (when |d2β/dt2| > threshold), the second derivative's contribution is reduced or excluded; during normal steering, the second derivative is fully included. This dynamic adjustment resolves the contradiction by adapting the control strategy to the current operating condition.
Solution Approach 2:
The patent changes the parameter weights in the control amount calculation based on the steering condition. Specifically, the weight coefficient of the second derivative term (K3) is adjusted: set to 0 or a small value during abrupt steering, and set to a normal value during stable steering. This parameter change allows the system to optimize performance for different steering scenarios, improving response speed when needed while maintaining control effectiveness when the vehicle is stable.
2Stability of the object's composition
If the second derivative contribution is reduced during abrupt steering, then the control operation stability is improved, but the response to destabilizing conditions is delayed
Solution Approach 1:
The patent applies preliminary action by detecting abrupt steering conditions in advance through monitoring the second derivative threshold. When abrupt steering is detected, the system proactively adjusts the control strategy by reducing or excluding the second derivative contribution before instability can develop. This preventive approach maintains control stability while still responding timely to the steering input through the first derivative term.
3Device complexity
If only first derivative is used for control, then the control simplicity is improved, but the swift convergence of slip angle and yaw rate is not achieved
Solution Approach 1:
The patent applies partial action by selectively using the second derivative term only when necessary (during normal steering conditions). The control amount includes the second derivative contribution during stable steering to achieve swift convergence, but excludes it during abrupt steering to maintain stability. This partial use of the more complex term optimizes the balance between convergence speed and control stability without always incurring the full complexity cost.
Data Source
AI summary
A vehicle behavior control apparatus is equipped with a slip angle detector that detects a slip angle of a vehicle, a control amount calculation portion that calculates a control amount from the slip angle detected by the slip angle detector, a derivative of the slip angle, and a second order derivative of the slip angle, and a control portion that executes a behavior control for the vehicle based on the calculated control amount.