Research On The Coordinated Manipulation Methods For Redundant Dual-arm Robots

Redundant dual-arm robots have unique advantages such as wide applicable scope,strong cooperative ability and high reliability which single-arm robots don’t have. Theyhave a broad application foreground in industrial automation lines, social services andspace assignments. As the key technology for redundant dual-arm robots, coordinatedmanipulation methods have become a research hotspot in robot control fields. In thiswork, key issue such as end-effectors’ tracking errors and relative errors between armsduring coordinated manipulation, distribution of end-effectors’ loadings and simulationsabout typical coordinated tasks for redundant dual-arm robots are investigated.Firstly, basic theories of coordinated manipulation for redundant dual-arm robotsare studied. According to structure configuration and sizes of MOTOMAN-SDA20redundant dual-arm robot, the kinematic model of coordination system is built and itskinematics is analyzed. The characteristics of loose coordination and tight coordinationare analyzed and then their coordinated constraints are modeled respectively. Dynamicsof coordination system are analyzed. Arms and object dynamic models are establishedand the internal force is described.Secondly, a multiple-priority control method is designed for end-effectors’ trackingerrors, relative errors between arms and control of redundant joints during loosecoordination of redundant dual-arm robots. By introducing the model consisting ofspatial in-parallel spring and damping, the impedance relation about the end-effectors’tracking errors and relative errors is modeled and then a main task control law isdeveloped for loose coordination. The main task control law can restrict the size anddirection of the end-effectors’ errors namely the relative errors between two arms can becontrolled. The second priority task is planned and optimized in null space which cancontrol the impedance of redundant joints and avoid joint motion limits.Thirdly, a control method based on pose coordination and force coordination isdesigned for the control of the object’s tracking errors and distribution of end-effectors’loadings during tight coordination of redundant dual-arm robots. By introducing themodel consisting of spatial in-parallel spring and damping, the impedance relation aboutthe object’ errors and relative errors is built and a pose coordination method which candecrease the object’s errors is designed. Based on the analysis of grasping model, aforce coordination method is put forward to realize the optimal distribution of endloadings and limit the object’s internal force by introducing a variable weighted matrix.Finally, some simulation examples of typical coordinated tasks including shaft andhole mating and grasping an object with redundant dual-arm robots are studied. The results verify that the coordinated manipulation methods are well designed and reliablyoperated, and they can satisfy the requirements of coordinated tasks for redundantdual-arm robots.