Design of Nonlinear Control Systems for Autorobots

Abstract

Currently, various types of robots are increasingly being used to solve different tasks. Most often, these are mobile robots that move on the earth’s surface performing the assigned tasks, in particular, they are four-wheeled robots similar to a car — autorobots. As control objects, the robots are essentially nonlinear, which requires the use of nonlinear methods for the control system design. At the same time, it is difficult to apply traditional methods for designing nonlinear control systems due to a complex type of nonlinearities in the equations of mobile robots and, in particular, autorobots. In this paper, the design problem is solved using a discrete-continuous quasilinear model, which is created on the basis of the nonlinear differential equations in the Cauchy form. Due to the great complexity of the nonlinearities of the autorobot equations, the corresponding quasilinear model is created by the numerical method. The quasilinear model obtained by this method is discrete-continuous and controllable, moreover, its state variables are measurable. The discrete autorobot control system includes two practically independent control subsystems: longitudinal speed and turns. A discrete PI control law is used to control the speed, and the discrete turn control subsystem is designed by the method of desired dynamics. The resulting autorobot control system provides a stable movement along the trajectory, which can be set as a function of time or as a function of the coordinates of the moving autorobot’s position.
The suggested approach can be used to design control systems for nonlinear objects of various purposes with complex differentiated nonlinearities. However, the design problem has a solution if the corresponding discrete-continuous quasilinear model of the object is controllable, and the state variables are measurable.