Wheeled mobile bases are important components of heavy-duty working machines, as they extend the workspace of the manipulators they carry on-board, allowing them to perform more complex manipulation tasks. Hence, the mobile robot control problem is of great interest when heading into a future in which hydraulic working machines are becoming field-robotic systems with an increased level of (semi-)autonomy.While purely kinematic mobile robot control laws can achieve accurate path-following control of heavy-duty vehicles, for advanced mobile manipulation operations, both high-precision motion and force tracking are desirable qualities. For example, non-convervatively tuned kinematic controllers could become subject to considerable longitudinal slip and loss of traction in face of changing environments, especially on challenging road surfaces such as wet or icy asphalt, which could jeopardize controller stability. In the literature, nonlinear actuator dynamics are rarely considered in the control design.In this paper, a nonlinear-model-based controller for a hydraulic-motor-driven mobile platform is developed, using a subsystem-dynamics-based control design methodology that takes into account the nonlinear actuator dynamics of the in-wheel hydraulic motors. The studied system, a four-wheel heavy-duty mobile elevating platform, is actuated by four servovalve-controlled fixed-displacement hubmotors and two symmetric steering cylinders. Field experiments are conducted to demonstrate the effectiveness of the proposed controller.

Model-Based Control of a Mobile Platform With Independently Controlled In-Wheel Hydraulic Motors

Paper Proceedings: https://asmedigitalcollection.asme.org/FPST/FPMC2021/volume/85239

2021 ASME/BATH Symposium on Fluid Power and Motion Control (FPMC2021)

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