Study On Joint Design And Servo Drive Of Collaborative Robot

Based on the development of robot technology,human-robot collaboration has become reality.The appearance of collaborative robots not only threw light upon industrial production,but brought new power to education,medical industry,service and so on.Collaborative robot has become one of the hot research topic in the robot domain.Study on joint module design and servo drive has been treated as significant infrastructure of collaborative robot design.Lightweight design and joint force feedback are two main characteristics of collaborative robots.In this paper,a new modular joint design scheme has been proposed to improve lightweight design with the goal of building 7-DOF collaborative robots.In order to realize electrical connection with internal cabling,hollow structure has been used in joint module design.Main parts of a joint module include PMSM,harmonic reducer,optical encoder,magnet encoder,servo driver and brake.Based on mechanical structure,the PCB of servo driver with STM32F405 has been designed.In the circuit design,RS485 bus is used to communicate with upper controller.Three-phase bridge type PWM converter is applied to drive PMSM.Different from other servo drivers,the driver designed in this paper is more integrated,which contains many sensors,such as current sensors,optical encoder chips,magnet encoder chips,IMUs and so on.The information of joints' orientation can be obtained through IMUs.Joint force feedback can be realized by detecting the current change of PMSM.Last,the d-q axis mathematic model of joint PMSM was built.Based on hardware,a joint servo drive program using id=0 vector control has been designed.In servo performance test,independent joint modules responded fast and the collaborative robot which contains 7 joint modules could run smoothly at low speed.