Abstract
This paper presents a nonlinear, universal, path-following controller for Wheeled Mobile Robots (WMRs). This approach, unlike previous algorithms, solves the path-following problem for all common categories of holonomic and nonholonomic WMRs, such as omnidirectional, unicycle, car-like, and all steerable wheels. This generality is the consequence of a two-stage solution that tackles separately the platform path-following and wheels’ kinematic constraints. In the first stage, for a mobile platform divested of the wheels’ constraints, we develop a general paradigm of a path-following controller that plans asymptotic paths from the WMR to the desired path and, accordingly, we derive a realization of the presented paradigm. The second stage accounts for the kinematic constraints imposed by the wheels. In this stage, we demonstrate that the designed controller simplifies the otherwise impenetrable wheels’ kinematic and nonholonomic constraints into explicit proportional functions between the velocity of the platform and that of the wheels. This result enables us to derive a closed-form trajectory generation scheme for the asymptotic path that constantly keeps the wheels’ steering and driving velocities within their corresponding, pre-specified bounds. Extensive experimental results on several types of WMRs, along with simulation results for the other types, are provided to demonstrate the performance and the efficacy of the method.
Highlights
Wheeled Mobile Robots (WMRs) form a significant subset of Unmanned Ground Vehicles (UGVs)
The multitude of motion controllers proposed for mobile robots, especially those with nonholonomic constraints, may be roughly categorized into three groups [1]: point stabilization [2], trajectory tracking [3], and path-following [4]
We presented a universal bounded-velocity path-following algorithm for Wheeled Mobile Robots (WMRs) operating under the condition of pure rolling without skidding
Summary
Wheeled Mobile Robots (WMRs) form a significant subset of Unmanned Ground Vehicles (UGVs). The path-following algorithms are classified into several branches, including, but not limited to, Optimal Control approaches [6,7], Feedback Linearizion methods [8], Line of Sight guidance laws [9], Pure Pursuit techniques [10], and Vector Fields methods [11] (see [12] for a thorough review). The majority of these algorithms incorporate a concept that goes by many names, including “Virtual Target Point”, “Carrot”, and “Rabbit”. The differences among and between those branches mainly occur in the design of the guidance controller, the method for selecting the virtual point, and the its motion strategy along the path
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