Novel Contactless Active Robotic Joint Using AMB: Design and Control

This paper investigates the design, modelling and control of a novel contactless active robotic joint using active magnetic bearing (AMB). A robot with such joint avoids dust generation, oil lubrication and friction. This makes such robot suitable for applications in clean environments such as clean and surgery rooms. Also, such joint can be used in space robots, self-reconfiguration robots and robots with selective compliance. In contrast to the passive joint with AMB that needs the control of 5 degree-of-freedom (DOF), the proposed joint here needs the control of 6-DOFs. The additional variable to be controlled is the robot joint angle. Frameless, brushless, direct drive, high torque DC motor (BLDC) is used to control the robot joint angle. A contactless sensor for robot joint angle measurement is proposed. The mutual interaction between the control of the BLDC motor and the AMB is studied. Although in this paper tracking control of the robot joint angle and stabilization of the other 5-DOFs to their null values are carried out, it is possible to carry out tracking control of all the 6-DOFs. This leads to enlarge the mobility of the joint from 1-DOF to 6-DOFs. Feedback linearization controller is used to track the robot joint angle desired trajectory. State feedback controller is used to stabilize the AMB. The proposed system is designed and simulated using CATIA and MATLAB/Simulink. The results prove the feasibility of the proposed robotic joint from design and control view points.