Design Of Heavy-load Manipulator Joints For Nursing Task And Research On Its Impedance Control Method

Nowadays,nursing robots are in great demand with the aging of the population.The key technical difficulty of nursing robots is the load capability of its joint,and it usually should have enough security during carrying out the nursing task.In this paper,two joints with the largest load are designed for the nursing robot which is used to move patients in the ward,and the security of the nursing process is realized by the method of impedance control.First of all,the movement process of the robot to carry out the nursing task is analyzed,and its dynamic simulation model is established in ADAMS.Then,the design parameters of torque and motion range of the two large load joints are obtained.Then the finite element analysis of each key component is carried out to verify the reliability of its strength.Finally,two large load joints that can meet the design requirements of load capacity are obtained through processing and assembly;Secondly,based on the communication protocol of CANOPEN,a hardware control system is designed for two large load joints,and sensors such as central controller,servo driver,high-precision encoder are selected for the two joints respectively.The designed hardware control system can carry out precise position control and force control for the two joints;Then,in view of the problems that the traditional commercial torque sensor will inevitably bring about,such as increasing joint flexibility and joint installation space,two joint output torque estimation methods of harmonic reducer based on deformation calibration are innovatively proposed.The two methods have enough measurement accuracy,and can be applied to different scenes according to their specific characteristics;Finally,in view of the special application scenario of nursing,the impedance controller based on position is designed for the two joints respectively,and a simplified simulation model of nursing scenario is established.Different impedance control parameters are used for simulation experiments,and finally the selection rules of impedance control parameters are obtained.The final experimental test shows that the designed joint can fulfill the functional requirements of large load,and has reasonable position control accuracy and response speed.The designed impedance controller can make the two joints show reasonable flexibility,and effectively improve the safety of nursing tasks.