It is easy to realize that most robots do not move to the desired endpoint (Tool Center Point (TCP)) using high-resolution noncontact instrumentation because of manufacturing and assembly errors, transmission system errors, and mechanical wear. This paper presents a robot calibration solution by changing the endpoint trajectories while maintaining the robot’s control system and device usages. Two independent systems to measure the endpoint positions, the robot encoder and a noncontact measuring system with a high-resolution camera, are used to determine the endpoint errors. A new trajectory based on the measured errors will be built to replace the original trajectory. The results show that the proposed method can significantly reduce errors; moreover, this is a low-cost solution and easy to apply in practice and calibration can be done cyclically. The only requirement for this method is a noncontact measuring device with high-resolution and located independently with the robot in calibration.

This paper proposed a new method to downgrade the kinematic mathematical model of parallel robots. A technique of complement mathematical models uses constraints to change the form of objective functions. An equivalent structure is used to replace the original structure of investigated robots. The difficulties encountered in solving problems having the transcendental form can be avoided by downgrading formula of the new mathematical model. The original formula which is usually in quaternary order can be downgraded to quadratic form. The main advantages of this method are understandable mathematical basis, high accuracy, and quick convergence. Carrying out solutions for pracitical kinematic problems of parallel robots becomes very promissable.

Testing or digitizing the machined surface in inverse manufacturing always requires the use of modern, interconnected measuring devices, and these devices share tool control programs with probe trajectory to check 3D surfaces through CAM software. Coordinate measuring machines with a large workspace need very rigid mechanical structures and parallel structures used instead are one of the solutions to this problem. Despite the extremely high stiffness, the characteristics of the parallel structure are of compound design and kinematics. One of the typical difficulties is that the forward and inverse kinematic problems have many solutions. When used as a measuring machine, solving the kinematic problem is often required. If there are not enough bases to unique identify the endpoint coordinates, the application of robots such as hexapods to make CMM machines will fail. This paper introduces a technical solution to achieve a unique solution when solving a forward kinematic problem using a hexapod device. The sensors are mounted on the device to recognize the generalized coordinates and the auxiliary parameters at the same time, then the unique solution of the problem will be determined. The illustrative application on the parallel structure of the SRS and SPS hexapod configuration shows the correctness of the research idea.

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