Current Control and Force Control in the Drives of Robot Grippers

Currently, the task of improving the robot grippers and their force control algorithms is urgent, thanks to the development of such areas of robotics as medical and rehabilitation robotics, prosthetics, collaborative robotics and other areas where there is the task of limiting or minimizing the loads acting on the object of manipulation. The force control in the electrically driven dexterous gripper is ultimately provided by the current control. Therefore, the purpose of this article is to analyze the operation of various current regulators in the context of their application in dexterous gripper and manipulators with a force control. The article considers the following current controllers: proportional-integral, adaptive, hysteretic and hysteretic with adjusting loop. Among these controllers, the hysteresis controller with adjusting loop is promising for the force control gripper and manipulator, since it provides switching frequency stabilization and current ripples reduction in a motor driver while maintaining fast response and sufficient robustness. For the hysteresis current controller with adjusting loop, reduced and linearized mathematical models of the adjusting loop are proposed. Moreover, based on the linearized model, methodic is constructed for the adjusting loop synthesis, which assumes the using of the classical control theory. Based on the synthesized current controllers, the analysis of the two-fingered gripper control system carried out, taking into account such factors as the force control accuracy, switching frequency stability and current ripples in the motor driver. Comparison results of current controllers can be used for the rational choice of a current controller providing force control, and the proposed synthesis methodic of the current controller with adjusting loop can to provide the controller generation with given control quality parameters.

current control, current loop, force control, torque control, dexterous gripper, gripping, forces distribution

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