| Because of its high rigidity, high precision, fast response and large load, the parallel mechanism and the hybrid mechanism are widely used. In this paper, according to the characteristics of material sorting occasions, a motion platform(end effector is placed) with 3D transformational and a rotation is put forward based on the screw theory, namely 1Rz3 T type mechanism, again, planar mechanism, namely 1Rz2 Txy type mechanism. In addition, a full DOF hybrid mechanism is proposed based on the two mechanisms mentioned above, the advantages of parallel mechanism and serial mechanism are combined. According to the working condition of the hybrid mechanism, the non-contact measurement method based on vision is used for nondestructive and non-contact pressure measurement, and the measurement system has good portability.First, the screw theory and less DOF parallel mechanisms are summarized, according to applications such as: express sorting, the design scheme of less DOF parallel mechanism and full DOF hybrid mechanism is determined; on the basis of the review of based on domestic and foreign camera calibration, the camera calibration method is determined, the camera calibration is convenient, accurate and reliable;, the CCD measurement system is analyzed based on the survey of machine vision measurement technology. According to the existing situation, the non-contact measurement and the motion platform of mechanism are combined, the overall design scheme of less DOF motion platform based on vision non-contact measurement is proposed, the foundation of the future engineering application is provided for subsequent hybrid mechanism.Secondly,the parallel mechanism of 1Rz3 T four-DOF is analyzed based on the theory of spiral base system, a new parallel mechanism of motion decoupling of 1Rz3 T four-DOF is proposed, through the analysis of parallel mechanism of 1Rz2 Txysymmetric plane, a parallel mechanism of 3RRR 1Rz2 Txy symmetric plane is proposed, a serial parallel mechanism with six-DOF is formed by combining these two structures.Then, the imaging model of camera and technology of camera calibration are studied, the intrinsic parameters and external parameters of camera are analyzed, and the calibration toolbox of Matlab is used for calibrating the image of checkerboard, the basis of the vision based non-contact measurement is provided for the subsequent motion platform of parallel mechanism of the 3RRR1Rz2 Txy symmetrical plane.Finally, the test system is established, the parallel mechanism of 3RRR 1Rz2 Txy symmetrical plane and the parallel mechanism of 1Rz3 T four-DOF motion decoupling are established. The control system of motion platform for the 3RRR parallel mechanism is compiled and the pose of motion platform is collected. |
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