Design And Study On Motion Controller Of FSW Robot

In this paper, hybrid robot based on 2UPR/RPS parallel mechanism was chosen as the control object, and a new motion controller based on STM32F4 & FPGA was developed according to its application in friction stir welding. Besides this paper studied the motion control algorithm of robot, the position closed loop control algorithm of AC servo system and torque / position control strategy of FSW robot. More details are as follows:Firstly, According to the control object, it designed the overall scheme of the motion controller. STM32 & FPGA dual-core structure was used for the motion controller, and tasks were assigned respectively according to the characteristics of each processor. Then specific circuits of each module were designed for AC servo drive, including the encoder signal input, analog voltage output, pulse output and switch signal input & output.Secondly, the motion control algorithm of the hybrid robot was studied and the interpolation strategy and the speed control strategy were analyzed. Specifically, interpolation algorithm of space line and arc was constructed in Cartesian space on the basis of data sampling interpolating theory and interpolation algorithm of DDA and PVT was conducted in joint space by taking two level interpolation of STM32 & FPGA. Next, linear acceleration & deceleration control algorithm and velocity look-ahead control algorithm under discrete time were deduced. The accuracy of the above algorithms were verified in MATLAB.Thirdly, the mathematical model of AC servo system has established. Sliding mode control and manifold deformation control were adopted to design the position closed loop of the AC servo system according to servo drive’s working in speed control mode. And the accuracy was also verified in AC servo system and FSW robot. Afterwards, the torque / position control strategy for FSW equipment was proposed focus on the application of hybrid robot based on 2UPR/RPS parallel mechanism in FSW and the welding process of FSW using motor spindle current as the feedback signal for the indirect-measurement of torque.Lastly, a corresponding experiment platform was set up to test the motion controller’s performance. AC servo system was used as the control object in this test, and the precision of pulse output, encoder counting and analog voltage output was measured. The precision of linear acceleration & deceleration control algorithm, the controller of PID position loop and the controller of manifold deformation loop was verified.