Position and speed control of a low-cost two-wheeled, self-balancing inverted pendulum vehicle

In this paper we present a low-cost prototype of a two-wheeled, self-balancing inverted pendulum realized at the mechatronics laboratory of the University of Trento. This vehicle lends itself to represent a class of control problems that arise in many educational robotic devices custom built and assembled with low-end market components. We provide a detailed description of the equipment and describe the strategies adopted to suitably address backlash of the low-cost DC motors and disturbances arising from the voltage controlled hardware. Then we propose a nested control paradigm where an inner loop provides regulation of a virtual control requested by an outer loop that uses the pitch angle to regulate the longitudinal displacement and speed. Three saturation-based control laws are proposed for the outer loop, all of them allowing the designer to adjust the maximum pitch angle. Experimental results illustrate the effectiveness of the proposed control laws and the operation of the developed prototype.