Stability (learning theory)

Physics

Nonlinear system

Invariant (physics)

Inverted pendulum

Mathematics

Mathematical physics

Mathematical optimization

Quadratic equation

Machine learning

Actuator

Artificial intelligence

Exponential stability

Control (management)

Geometry

Constraint (computer-aided design)

Computer science

Quantum mechanics

Quadratic programming

Control theory (sociology)

Artificial neural network

Lyapunov function

IEEE Transactions on Automatic Control

A method is presented to analyze the stability of feedback systems with neural network controllers. Two stability theorems are given to prove asymptotic stability and to compute an ellipsoidal innerapproximation to the region of attraction (ROA). The first theorem addresses linear time-invariant systems, and merges Lyapunov theory with local (sector) quadratic constraints to bound the nonlinear activation functions in the neural network. The second theorem allows the system to include perturbations such as unmodeled dynamics, slope-restricted nonlinearities, and time delay, using integral quadratic constraint (IQCs) to capture their input/output behavior. This in turn allows for off-by-one IQCs to refine the description of activation functions by capturing their slope restrictions. Both results rely on semidefinite programming to approximate the ROA. The method is illustrated on systems with neural networks trained to stabilize a nonlinear inverted pendulum as well as vehicle lateral dynamics with actuator uncertainty.

Stability Analysis Using Quadratic Constraints for Systems With Neural Network Controllers