H-infinity Formulation
Frank L. Lewis
Abstract: Practical
industrial systems have actuator constraints and restricted
availability of measurements. Unfortunately, most results on
robust H-infinity control are presented for full state feedback and
unconstrained control inputs. Neural networks can be used with
H-infinity control techniques to overcome these
limitations. In this paper we consider H-infinity nonlinear
output feedback control for constrained input systems. The
constraints on the input to the system are encoded via a quasi-norm
that allows non-quadratic supply rates along with dissipativity theory
to formulate the robust output feedback control problem using
Hamilton-Jacobi-Isaac (HJI) equations. A rigorous approach is
presented that allows for formal mathematical proofs of convergence and
closed-loop stability. An iterative solution technique based on a
game theoretic interpretation is presented. To provide a
computationally tractable controller design method, the solution is
approximated at each iteration
with a neural network. The result is a closed-loop control based
on
a neural net that has been tuned a priori off-line. This
neural network controller only depends on the available output
measurements and also
guarantees bounded control inputs.