Abstract
By using the hierarchical controller approach, a new solution for the control problem related to trajectory tracking in a differential drive wheeled mobile robot (DDWMR) is presented in this paper. For this aim, the dynamics of the three subsystems composing a DDWMR, i.e., the mechanical structure (differential drive type), the actuators (DC motors), and the power stage (DC/DC Buck power converters), are taken into account. The proposed hierarchical switched controller has three levels: the high level corresponds to a kinematic control for the mechanical structure; the medium level includes two controls based on differential flatness for the actuators; and the low level is linked to two cascade switched controls based on sliding modes and PI control for the power stage. The hierarchical switched controller was experimentally implemented on a DDWMR prototype via MATLAB-Simulink along with a DS1104 board. With the intention of assessing the performance of the switched controller, experimental results associated with a hierarchical average controller recently reported in literature are also presented here. The experimental results show the robustness of both controllers when parametric uncertainties are applied. However, the performance achieved with the switched controller introduced in the present paper is better than, or at least similar to, performance achieved with the average controller reported in literature.
Highlights
Over the past few years, the trajectory tracking problem in differential drive wheeled mobile robots (DDWMRs) has been one of the most challenging topics in robot control
Such a controller has three levels: the control at the high level for the mechanical structure is a kinematic control; at the medium level for the actuators (DC motors), two controls based on differential flatness are proposed; at the low level for the power stage (DC/DC Buck power converters), two cascade switched control schemes based on sliding mode control (SMC) and PI control were designed
In the low hierarchy level, via two cascade switched controls based on SMC and PI control, vr and vl, it is assured that the output voltages of the DC/DC Buck power converters will track the desired voltage profiles imposed by the medium level, i.e., →
Summary
Over the past few years, the trajectory tracking problem in differential drive wheeled mobile robots (DDWMRs) has been one of the most challenging topics in robot control. This is mainly because DDWMRs are underactuated and non-holonomic systems [1,2,3]. DDWMRs are composed, in general, of three subsystems: the mechanical structure, actuators, and power stage In this direction, the design of tracking controls has been generally based on considering the Sensors 2018, 18, 4316; doi:10.3390/s18124316 www.mdpi.com/journal/sensors. Examples demonstrating this include the studies presented in [8,9,10,11], where the dynamics of the actuators, power stage, and electric power supply were taken into account in control design for mechatronic systems
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