End-effector Design And Contact Force Control In Robotic Grinding Process Of Controllable Pitch Propeller

Controllable pitch propeller is a key equipment of dynamic positioning system. The quality of blade surface has a great influence on system performance and service life. Because of big labor intensity, baneful operating environment and unconformity surface quality, it's not very apposite for workers to grind and polish. Some of the mainstream robotic grinding systems are suitable for small or medium-sized work pieces. However, the surface of controllable pitch propeller in high power dynamic positioning is very large and complex, which makes it difficult for the manipulator to keep contacts with the blade steadily in the whole workspace. So it has important significance for improving the machining efficiency and surface integrity to design a befitting robotic grinding system for controllable pitch propeller.Stability of the robotic grinding process is analyzed in this paper, and the simulation results show that the weak stiffness of the Multi-joint manipulator can generate modal coupling vibration more easily. An end-effector with force feedback and position feedback meanwhile is designed and can be driven by servo motor. Robot kinematics model is established and workspace is enough for the grinding process of the blade after analysis and compare. Simulation model of robotic grinding system for controllable pitch propeller is established in RobotStudio software. The change of joint angle is analyzed when robot moves along the selected three typical trajectories, and the feasibility of the scheme is verified.As an example, dynamics model of two degrees of freedom planar manipulator is established, and impedance control is simulated in Matlab/Simulink. The regulation of impedance parameters under the constraint conditions and the influence of changeable environmental stiffness on contact force control precision are analyzed. For active compliance end-effector, NPD controller with gains modulated based on phase is designed, adjusting the damping coefficient according to the variation of deviation and the deviation rate. The results of simulation show that this method can effectively reduce the overshoot and oscillation frequency for collision and interference, at the same time guarantee the fast rise time.Force control test bed is designed and constructed, including structural design and selection. With stm32 microcontroller as the control core, some experiments are completed, for example the drive control of servo motor, signal acquisition and serial communication function, and the contact force control experiment was carried out in the end, and the results show that stability is better than PD control when using NPD control.