Vehicle Avoidance Trajectory Refinement With Clothoid Optimization
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Solution Overview
Problem
Existing vehicle trajectory control systems for automatic avoidance systems impose strict constraints on clothoid trajectories, leading to instability and uncomfortable maneuvers due to neglecting non-zero initial conditions, which can cause pilot-induced oscillations and destabilization.
Innovation Solution
A method for refining clothoid trajectories by optimizing steering wheel angle and vehicle heading using a quadratic optimization problem with controllability constraints, ensuring smooth and stable avoidance maneuvers by considering initial conditions and driver expectations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strict constraints are imposed on clothoid trajectories (final steering wheel angle equals 0, integral of steering wheel angle profile equals 0), then trajectory planning robustness is improved, but system stability and driver comfort deteriorate due to neglecting non-zero initial conditions
Solution Approach 1:
The patent modifies the trajectory parameters by introducing a refined clothoid trajectory that incorporates non-zero initial conditions for steering wheel angle and vehicle heading. Instead of forcing final steering wheel angle to zero, the optimization allows flexible final states while satisfying controllability constraints, thereby maintaining system stability and driver comfort without sacrificing planning robustness
Solution Approach 2:
The patent implements a dynamic optimization approach where the trajectory is continuously refined based on current system state (initial steering wheel angle, vehicle heading, speed). This dynamic adaptation allows the system to handle non-zero initial conditions properly, preventing instability and pilot-induced oscillations while maintaining robust avoidance performance
2Manufacturing precision
If the controller forces the heading to zero to avoid deviation from the clothoid reference trajectory, then trajectory tracking accuracy is improved, but driver comfort and understanding deteriorate due to steering wheel turning against the natural direction of avoidance
Solution Approach 1:
The patent inverts the traditional approach by not forcing the heading to zero, but rather allowing the trajectory to naturally accommodate the initial heading condition. The optimization problem is reformulated to seek a trajectory that respects the natural avoidance direction while achieving collision avoidance, thereby aligning system behavior with driver expectations and maintaining comfort
3Adaptability or versatility
If saturation constraints are applied when the driver acts against the maneuver, then system control limits are respected, but system stability deteriorates due to pilot-induced oscillations
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the driver's steering input and the generated trajectory. When the driver acts against the avoidance maneuver, the system detects this conflict and adjusts the trajectory refinement to accommodate driver input within controllability limits, preventing saturation-induced oscillations while maintaining overall system stability
Data Source
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AI summary
Method for controlling a motor vehicle to avoid a target, the motor vehicle being equipped with at least two perception sensors, the control method comprising the following steps: - a step of determining data of the at least two sensors, - a step of fusing the data of the at least two sensors so as to determine at least the angle of the steering wheel, the speed of the vehicle and the heading of the vehicle, - a step of planning an avoidance path to avoid the target, taking the form of a Euler spiral, - a step of refining the avoidance path used to avoid the target depending on the angle of the steering wheel, on the speed of the vehicle and on the heading of the vehicle and based on the solution of an optimisation problem, - a step of controlling the vehicle so as to follow the refined path, the step of refining the path comprising a first series of sub-steps for honing the avoidance path depending on the length of the path, on the direction of rotation of the steering wheel and on the final heading and a second series of sub-steps for refining the honed trajectory depending on the initial heading and on the direction of rotation of the steering wheel.