Assessment of an Average Tracking Controller that Considers all the Subsystems Involved in a WMR: Implementation via PWM or Sigma-Delta Modulation

This paper has two aims; the first, to present the design of a three-level average controller (that do not require electromechanical sensors) for the trajectory tracking task in a differential drive wheeled mobile robot (WMR). Such a controller considers, for the first time in literature, the dynamics of the three subsystems composing a WMR, i.e., mechanical structure, actuators, and power stage. The proposed controller is designed as follows: At the high level, a kinematic control for the mechanical structure is proposed. At the medium level, a control based on differential flatness for the actuators is presented. And at the low level, an average flatness control for the power is proposed. The second aim of this paper is to present an assessment, via numerical simulations using MATLAB-Simulink, of the three-level average controller performance when it is implemented using a PWM or a Σ-Δ-modulator. In these simulations the robustness of the controller is shown when multiple abrupt variations are considered in some parameters of the WMR.