Autonomous Vehicle Trajectory Planning with Clothoid Curves
Solution Overview
Problem
Autonomous vehicle control systems face challenges in managing vehicle trajectories to minimize discomfort and motion sickness for human occupants, particularly during abrupt directional changes like U-turns, lane changes, and intersections, as existing approaches do not adequately consider dynamic limits and occupant comfort.
Innovation Solution
A method and system for determining an optimized vehicle trajectory by processors that obtain current and goal states, applying numerical minimization to minimize trajectory length and lateral acceleration values, using a velocity profile to control steering and throttle systems, thereby generating control inputs for smoother maneuvers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the vehicle follows a direct geometric path from current location to destination, then the trajectory length is minimized, but the lateral acceleration increases causing occupant discomfort and motion sickness
Solution Approach 1:
The system dynamically adjusts the trajectory by introducing a clothoid curve with variable curvature instead of a fixed geometric path. The curvature changes continuously along the trajectory, allowing the vehicle to transition smoothly between straight sections and turns, thereby reducing lateral acceleration while maintaining reasonable trajectory length.
Solution Approach 2:
The invention changes the curvature parameter along the trajectory by using a clothoid curve where curvature is a function of arc length. This parameter change allows the trajectory to start with zero curvature at the beginning and end points, and reach maximum curvature at the midpoint, optimizing both trajectory length and lateral acceleration characteristics.
2Productivity
If the vehicle makes abrupt directional changes to follow the route, then the productivity is improved, but the occupant comfort deteriorates due to motion sickness
Solution Approach 1:
The system replaces static, abrupt directional changes with dynamic, continuous curvature transitions. The clothoid curve enables the vehicle to gradually change direction rather than making sudden turns, maintaining maneuver efficiency while significantly reducing occupant discomfort and motion sickness.
Solution Approach 2:
The invention applies curved transitions instead of sharp angular changes. By using a clothoid curve with continuously varying curvature, the system creates smooth transitional paths that reduce lateral acceleration impulses, thereby improving occupant comfort during maneuvers while maintaining operational efficiency.
3Object-affected harmful factors
If the trajectory is optimized to reduce lateral acceleration, then the occupant comfort is improved, but the trajectory length increases
Solution Approach 1:
The system optimizes the curvature parameter distribution along the trajectory using a clothoid curve. By carefully controlling how curvature varies with arc length, the invention achieves a balance that keeps lateral acceleration low while minimizing the increase in trajectory length, rather than simply reducing speed or taking much wider turns.
Data Source
AI summary
A method for controlling an autonomous vehicle includes obtaining, by one or more processors, information describing a current state of the autonomous vehicle and a goal state of the autonomous vehicle; determining, by the one or more processors, an initial vehicle trajectory from the current state of the autonomous vehicle to the goal state of the autonomous vehicle; determining, by the one or more processors, an optimized vehicle trajectory based the initial trajectory and a velocity profile by applying numerical minimization to minimize a trajectory length value and a lateral acceleration value; and controlling the autonomous vehicle to traverse the optimized vehicle trajectory.