| The growing market for industrial and service robots requires the development of common and core technology for serial manipulators by taking insight into and addressing the related existing problems. As an important criterion for serial manipulators, motion accuracy is the key for perfect operation. Since application environments are becoming complex gradually, better motion accuracy of the manipulator is required. However, there is a big gap between the actual motion performance and the desired high accuracy robust motion performance of the manipulator, owing to the geometrical errors, ambient noise, vibration interferences of the manipulator. Therefore, improving motion accuracy of serial manipulator is of great significance in the development of robotic technology.With the goal of improving the motion accuracy of serial manipulator, the dissertation addresses the comprehensive study of a6-DOF serial manipulator, based on the integrated approach of theoretical analysis, numerical simulation and experimental validation. The research focuses on precision analysis, kinematics modeling, trajectory planning and optimization, real-time control system, parameter calibration, control variable compensation and active dynamic balancing of the serial manipulator.The innovative contents of the dissertation are summarized as follows:1. Research on trajectory optimization algorithm for serial manipulator is carried out. A fifth order polynomial is used for joint trajectory planning of the manipulator. Both theoretical analysis and simulation results illustrate that the execution time of the trajectory wields a lot of influence over the movements of the joints. In order to solve this problem, an optimizing method of execution time is proposed for generating smooth motion trajectories with smallest overshoot and lowest energy consumption. Numerical examples are presented in order to evaluate the performance of this optimizing method. Simulation results indicate that the high-performance of the optimized movements can produce effective enhancements of the productivity of the manipulator. On the basis of this optimization method, the execution time constraints of the multi-joint motion planning are established, and multi-joint motion planning for six-DOF manipulator are hence obtained. 2. In order to reduce or even eliminate kinematics error of the manipulator’s end-effector, a compensation method with high reliability, strong real-time capability is introduced in this dissertation. A real-coded and arithmetic recombination genetic algorithm is adopted in joints’ closed-loop servo motion control system, with the aim to optimize the control variables. Optimized parameters are used in the real-time predictive compensation control system with the purpose of reducing the manipulator’s motion errors. Numerical examples are presented in order to evaluate the performance of the compensation strategy, as well as the feasibility and effectiveness of improving positioning accuracy.3. In consideration of adverse impacts of the machine vibrations, an active dynamic balancing mechanism is designed to reduce the shaking forces and shaking moments of the manipulator. The dissertation presents the real-time active balancing techniques. A one-DOF force balancing,mechanism is firstly presented, and its dynamic modeling is built and analyzed. Moreover, the dissertation presents a study on a one-DOF moment balancing mechanism. Active vibration control for rotating machinery is explained in detail. Then the balancing machanism is mounted on an unbalanced serial manipulator, hence one-dimensional moment of the manipulator is dynamically balanced. Experiments are carried out with the aim to validate the dynamic performance of the balancing mechanism and the active vibration cancellation. Finally, a simple and compact three-DOF balancing unit is designed to balance both shaking-force and shaking-moment of the manipulator simultaneously.Due to the limited setting space, three independent links are used to constitute the balancing unit. By using the Lagrange equations, their dynamics model are established, and mathematical relations among the links’ motion parameters and balancing-force and balancing-moment are formulated as well. In addition, numerical simulations are presented with the aim to give insight in the possibilities and effectiveness of three-DOF active dynamic balancing. |
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