Improved direct gradient descent control of general nonlinear systems

This paper is concerned with Direct Gradient Descent Control (DGDC) of general nonlinear systems. DGDC manipulates the control inputs directly so as to decrease the performance function like the squared error, based on the gradients of the performance function and the steepest descent method. Stability of DGDC is proved by use of the comparison function method. We improve the convergence speed and the stability of DGDC by introducing a new artificial manipulating variable and by considering time derivative of the performance function. Namely, to improve the convergence, we extend the DGDC by decreasing both the performance function and its time derivative.