Research On Double PSDs Based Measurement System Of Trajectory Tracking Of A Moving Target

Nowadays, the need to measure the trajectory of the moving target is urgent. Non-contact measuring methods are widely used in the trajectory measuring in that it has no lines connecting, no process of preplanning the moving, rapid response speed, no other forces on the targets to be measured and a high efficiency of measuring. Based on these advantages, the non-contact measuring methods are suitable for trajectories measuring. The position of the target contacted by PSD is by the output current or the output voltage, the transmitting frequency of which is up to 10KHz and the accuracy of which is very high. Moreover, since the volume of PSD is small, it is suitable for measuring limited targets. Therefore, the technology of measuring the trajectory based on PSD is a very potential method of measuring the moving target.At present, the research of measuring the trajectory of the moving target based on PSD just started. Whatever the adjustment of measuring view based on the target, or the calibration algorithm and the error analysis are all at the developing stage. This paper presents a design of the measurement system of tracking the moving target based on the double PSDs. Firstly, coordinate systems are built based on the principle of linear pinhole model to analysis the mapping relation between the 3D coordinate values in the world coordinate system and 2D coordinate values in the PSD coordinate systems in one single PSD. Then the intrinsic parameters and the extrinsic parameters are calculated. Secondly, consider the impact of lens distortion. Because of the distortion, the true model would be non-lineal pinhole model. This paper studies how the distortion affect the errors of 2D coordinate values, then get the mathematical expression to optimize the parameters. Finally, based on the principle of 3D reconstruction, the mapping relation between the 3D coordinate values in the world coordinate system and the 2D values in both PSD coordinate systems are set, then the intrinsic and the extrinsic parameters of both PSDs are calculated. Based on the theoretical analysis, the hardware system design and the software system design are accomplished. In the hardware system design, light and driving circuit are finished to solve the problem of tracking the moving target. Finishing the option of PSDs, lens, DAQ cards and computer. Particularly a measuring support based on the binocular stereo vision which solve the problem of the connection between PSD and lens and the position between both PSDs. In the software part, the data collection program is written in lab VIEW. After the system building, two-step method to study the calibration of measuring moving trajectories based on double PSDs is used. Comparing the calculated 3D coordinates and the real 3D ones, then the system accuracy are calculated. Besides, this paper presents the error analysis in the system of measuring moving trajectories based on double PSDs. Finally, the system of measuring moving trajectories based on double PSDs is used in the actual industrial situation. The target is manipulator on the tool charger and ATC.The result of this paper would provide a new theoretical and technological foundation in terms of measuring the moving targets, trajectory planning, close-loop control and kinetic characteristic analysis, therefore it has a certain value of engineering application and theory reference significance.