A light cooperative manipulator with wireless communication and high payload

Traditional manipulator generally has heavy weight, large power consumption, small load capacity and a large number of electrical cables. In this paper, we developed a light-weight cooperative manipulator with wireless communication and high payload. It has seven highly integrated modular joints. Each joint consists of a permanent magnet DC brushless motor, a harmonic reducer, several sensors, a servo controller, and a wireless communication module. The joint position and velocity are measured by redundant sensors, including three Hall sensors, an incremental encoder and an absolute encoder. Information fusion can improve the accuracy and reliability. A current sensor is integrated internally and used to sense the joint current, which also reflects the driving torque through the calibrated current-torque curve. Each joint servo controller is composed of a FPGA and an ARM processor. Three typical control loops, i.e. position, speed and current control loops are realized in the servo controller. A central controller is used to plan and manage the trajectory of all the joints. To largely reduce the electrical cables, ZigBee module is also developed to supply the wireless communication between the central controller and all the joint servo controllers. Finally, the prototype is manufactured and experiments are performed, including simple motion, payload manipulation, current-torque calibration, et al. Experiment results show that the manipulator has high load to weight ratio and the joint torque can be approximately obtained by the current sensor.