Vehicle Motion Control for Longitudinal Force Saturation
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Solution Overview
Problem
Existing vehicle motion control systems face challenges in managing longitudinal forces within controllable ranges, leading to potential excessive increases or decreases in control amounts when requests exceed these ranges, resulting in prolonged convergence times for actual acceleration to match target acceleration.
Innovation Solution
A vehicle motion controller that includes a feedback controlling unit to calculate a control amount based on the difference between target and actual acceleration, a request outputting unit to determine a request longitudinal force, and an obtaining unit to assess the actuator's availability, prohibiting control amount adjustments when requests fall outside the controllable range or when certain vehicle stability controls are active.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control is continued when the requested longitudinal force exceeds the controllable range, then the control system attempts to eliminate the acceleration difference, but the control amount excessively increases or decreases without achieving the target acceleration
Solution Approach 1:
The system performs preliminary checks to determine whether the requested longitudinal force is within the controllable range before executing feedback control. By anticipating the feasibility of control actions and preventing invalid control amounts from being applied, the system avoids excessive accumulation of control errors and ensures timely convergence to target acceleration.
2Speed
If the feedback control amount is allowed to change freely to eliminate acceleration difference, then the control response is aggressive, but the control amount may excessively increase or decrease when the request exceeds controllable range
Solution Approach 1:
The system incorporates a feedback mechanism that monitors whether the requested longitudinal force is within the controllable range. When the request exceeds the range, the feedback loop prevents excessive changes in control amount while maintaining stable and reliable control behavior, avoiding oscillations or runaway control values.
3Stability of the object's composition
If the system prohibits control amount changes when request exceeds controllable range, then excessive changes are prevented, but the actual acceleration cannot converge to target acceleration rapidly
Solution Approach 1:
The system dynamically adjusts the controllability determination based on current vehicle conditions and actuator capabilities. By continuously updating the controllable range assessment, the system can permit control amount changes when conditions allow rapid convergence while prohibiting changes only when necessary to prevent excessive deviations, thus adapting control behavior to real-time requirements.
Data Source
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Figure 3(a)~4(c)
AI summary
A vehicle motion controller includes a feedback controlling unit that executes feedback control in which a difference between a target acceleration corresponding to a request value from a driver assistance device and an actual acceleration of a vehicle is an input, thereby calculating a control amount used to reduce the difference, a request outputting unit that calculates a request longitudinal force based on the control amount, the request longitudinal force controlling an actuator, and an obtaining unit that obtains, as availability, a range of a longitudinal force capable of being generated by the actuator, the availability being a controllable range of the longitudinal force. The feedback controlling unit prohibits the control amount from decreasing when the request longitudinal force is less than a minimum value in the availability.