Uni-drive modular robots: theory, design, and experiments

A modular serial robot consists of a chain of links and joints such that its configuration can be changed by the order and number of links and joints. Although theoretically a modular robot can take any configuration, the weight of the modules is usually the limiting factor in the number of modules that can be chained together. Since the actuator often contributes a significant portion of the module weight, this is reduced in the proposed design by replacing the actuator with a pair of clutches. Drive torque for the module is tapped from a central rotating shaft using these clutches, the central shaft being continuously driven by a single base-mounted motor. The position and velocity of the modules are regulated by controlling the engagement time of the clutches using the pulse width modulation technique. An experimental 2-axis gantry robot based on the modular uni-drive concept has been designed and fabricated. The mathematical model of the gantry robot is developed and experimental and simulation results are compared.