3DOF Trajectory Linearization Controller for Autonomous Vehicle Guidance
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Solution Overview
Problem
Conventional self-driving car systems are limited by their design for path-following and lack maneuverability, with separate controllers for steering and throttle, which restricts their performance and stability, especially in trajectory-tracking scenarios that require simultaneous control of speed and steering.
Innovation Solution
An integrated three degrees-of-freedom (3DOF) trajectory linearization controller and a pure pursuit guidance controller are developed, enabling simultaneous steering and speed control for trajectory-tracking operations, using singular perturbation theory for exponential stability and incorporating a top-level cognitive mission planner for fully autonomous vehicle operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If separate controllers for steering and throttle are used, then the control system structure is simple, but the vehicle performance and maneuverability are limited
Solution Approach 1:
The patent combines separate steering and throttle controllers into a unified control system that simultaneously processes both control inputs. This integration allows the system to coordinate steering angle and longitudinal velocity commands together, enabling complex maneuvers like trajectory tracking that require coupled control actions, thereby improving vehicle adaptability without excessive complexity increase.
2Device complexity
If path-following algorithm is used, then the control implementation is simple, but the vehicle has limited maneuverability and cannot handle speed constraints
Solution Approach 1:
The patent transitions from static path-following to dynamic trajectory-tracking control that incorporates time-varying speed constraints. The controller dynamically adjusts both steering angle and longitudinal velocity based on real-time tracking errors and desired trajectory parameters, enabling the vehicle to handle speed-constrained maneuvers while maintaining reasonable implementation complexity through systematic control design.
3Adaptability or versatility
If Model Predictive Control (MPC) technique is used, then the controller can handle nonlinear and time-varying motion control, but the computation is extremely intensive with limited performance and stability
Solution Approach 1:
The patent segments the control problem into manageable components: a guidance layer that generates desired trajectories and a control layer that executes tracking. This segmentation avoids the need for full-state MPC by breaking down the complex nonlinear control into simpler sub-problems, reducing computational intensity while maintaining the ability to handle nonlinear and time-varying motion control requirements.
Data Source
AI summary
Systems, methods, and computer program products for autonomous car-like ground vehicle guidance and trajectory tracking control. A multi-loop 3DOF trajectory linearization controller provides guidance to a vehicle having nonlinear rigid-body dynamics with nonlinear tire traction force, nonlinear drag forces and actuator dynamics. The controller may be based on a closed-loop PD-eigenvalue assignment and a singular perturbation (time-scale separation) theory for exponential stability, and controls the longitudinal velocity and steering angle simultaneously to follow a feasible guidance trajectory. A line-of-sight based pure-pursuit guidance controller may generate a 3DOF spatial trajectory that is provided to the 3DOF controller to enable target pursuit and path-following/trajectory-tracking. The resulting combination may provide a 3DOF motion control system with integrated simultaneous steering and speed control for automobile and car-like mobile robot target pursuit and trajectory-tracking.