In-situ intelligent manufacturing for large-volume equipment requires industrial robots with absolute high-accuracy positioning and orientation steering control. Conventional robots mainly employ an offline calibration technology to identify and compensate key robotic parameters. However, the dynamic and static parameters of a robot change nonlinearly. It is not possible to acquire a robot’s actual parameters and control the absolute pose of the robot with a high accuracy within a large workspace by offline calibration in real-time. This study proposes a real-time online absolute pose steering control method for an industrial robot based on six degrees of freedom laser tracking measurement, which adopts comprehensive compensation and correction of differential movement variables. First, the pose steering control system and robot kinematics error model are constructed, and then the pose error compensation mechanism and algorithm are introduced in detail. By accurately achieving the position and orientation of the robot end-tool, mapping the computed Jacobian matrix of the joint variable and correcting the joint variable, the real-time online absolute pose compensation for an industrial robot is accurately implemented in simulations and experimental tests. The average positioning error is 0.048 mm and orientation accuracy is better than 0.01 deg. The results demonstrate that the proposed method is feasible, and the online absolute accuracy of a robot is sufficiently enhanced.
A new type femtosecond laser tracker is one high precision measurement instrument with urgent need in science research region and industrial manufacture field. This paper focuses on the operational principle and the structure development of the femtosecond laser tracer, and the method of error compensation as well. The system modules were studied and constructed. The femtosecond frequency comb module was firstly analyzed and developed. The femtosecond laser frequency comb performed perfectly high precise distance measurement for laser tracker. The experimental result showed that the stability of repetition rate reached 3.0×10-12@1s and the stability of carrier envelop offset reached 1.0×10-10@1s. The initial experiment showed that measurement error was less than 1ppm. Later the error compensation module was introduced, and the optoelectronic aiming and tracking control module was built. The actual test result showed that the stability of miss distance was better than 2.0 μm, the tracking speed could reach 2m/s.