Weld Visual Tracking System Based On DSP And CPLD Design

Based on the research background of “Double seam automatic welding robot”, thisarticle designs a seam tracking robot control system using DSP and CPLD as the controlcenter. This control system has many advantages, including small volume, low cost andconvenient maintenance.The system adopts TMS320DM642as the video processor, in which image processingtask is performed. In order to reduce the difficulty of system development, we sue DM642development board as the video processing platform. The development board has two videoinput ports to collect video signals and one of which displays images. Besides, thedevelopment board extends two serial communication ports to transmit data to otherprocessors by TL16C752B.The EPM1207is employed as the processor of the motion control system. The EPM1270uses RS232to communicate with DM642and controls the motor movement by regulating thepulse signal.The motion control system has a variety of control strategies, includingmulti-axis coordinated motion, linear interpolation movement, acceleration and deceleration,the speed control while starting or stopping, the key input processing and free adjustmovement.Aiming at the problem of welding torch delaying the camera, this paper puts forward twokinds of tracking strategy, one of which is to adjust deviation using the mathematical model.According to the geometric relationship, we transform the distance between the camera andthe weld to the distance between the weld torch and the weld, after that we do the rectificationmovement. The other is the lag tracking method. We don’t do the rectification movementuntil the weld torch has arrived at the start point of the camera. Comparing two presentedmethods, the first method is finally selected as the tracking method of this system. In thetracking process, the PID control method is used to control the movement. Critical radiomethod is used to chose the three parameters of the PID controller. We determine theapproximate range and then test the parameters through experiment.The experimental results show that the embedded motion control system can achieve thedesign specifications and feed the scheduled functions. What is more, it has many advantages,including low cost, low power and miniaturized, so it has a practical value in the weldingapplication.