Nullspace Adaptive Velocity Controller for Ground Vehicles: Theory and Experimental Evaluation
Allan Elsberry, Jeremy Dawkins, Louis Whitcomb
AI summary
Problem
Traditional model-based controllers for ground vehicles lose stability and performance when vehicle parameters are unknown or change during operation, and existing estimation methods often require complex acceleration measurements or lack formal stability guarantees.
Approach
The authors design a model-based adaptive controller that integrates a nullspace adaptive identification algorithm with a Lyapunov-stable feedback law to estimate unknown parameters online and adjust control inputs using only body-frame velocities and control signals.
Key results
- Proven asymptotic stability of velocity tracking error and boundedness of all closed-loop signals
- Real-time online estimation of seven unknown plant and actuator parameters using only velocity and control inputs
- Numerical and experimental validation on a 1/10th scale vehicle confirming tracking accuracy and parameter convergence
- Demonstrated robust fault-tolerance and superior performance over non-adaptive and alternative controllers
Why it matters
Provides a mathematically guaranteed, sensor-efficient control framework for autonomous ground vehicles operating in dynamic or uncertain environments.
Abstract
We report a novel stable Model-Based Adaptive Velocity Tracking Controller (AVTC) for ground vehicles capable of asymptotically exactly tracking longitudinal and yaw reference velocities and simultaneously adaptively identifying unknown plant parameters and actuator parameters. The reported AVTC is developed for velocity control of the commonly accepted three degree-of-freedom second-order dynamic “bicycle” model for ground vehicles. A Lyapunov analysis shows asymptotic stability of the velocity tracking error in longitudinal and yaw velocities, boundedness of all signals, and convergence of the adaptive parameter estimates. A performance evaluation of the proposed AVTC is reported including numerical simulation evaluation and experimental evaluation that corroborates the analytical predictions of stability and tracking, and compares its performance to its non-adaptive counterpart and two alternative controllers. AVTC only requires body-frame velocities and control in- put signals, and robustly detects, quantitatively identifies, and compensates dynamically in real-time for faults arising from changes to plant, actuator, and environmental parameters during operations.