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With the rapid development of robot industrialization and intelligence, welding robots are widely used in construction, machinery and other fields, and the motion performance and trajectory planning capabilities of robots directly affect the quality of welding. Aiming at this kind of problem, combined with the characteristics of series mechanism and parallel mechanism, a new type of six-degree-of-freedom (6DOF)series-parallel hybrid welding robot mechanism is designed. The standard D-H model is used to describe the relationship between the adjacent links of the robot, the kinematic model of the robot is established using the Matlab Robotics toolbox, the correctness of the parameters of the robot connecting rod is verified, and the working space of the robot is further calculated. At the same time, a trapezoidal function with parabolic transition is used to plan the end effector of the hybrid welding robot, and the multi-objective trajectory optimization scheme is proposed. The particle swarm optimization algorithm is used to optimize the time parameters, and the optimal time parameters that meet the positioning accuracy of the end of the welding machine manipulator are solved. The simulation results show that the optimized trajectory improves the stability and positioning accuracy of the hybrid welding robot, and lays a theoretical foundation for further vibration analysis and control of the robot.

The research on the excavation resistance function of excavator is the key step to realize automatic excavation. Based on the classical soil-bucket model, a digging resistance model of automatic excavator is proposed. The expression of the excavation resistance function for the whole automatic excavation process of three stages of penetration, cutting and loading and the detailed calculation process of its coefficients are given. The existing bucket shape model is modified to make it more in line with the actual shape. Taking a certain excavation track and silty clay as examples, the theoretical excavation resistance curve under this working condition is calculated and compared with the results obtained by Ls-Prepost software simulation. The shape of the two curves is similar, and the maximum error is less than 10.2%, the results show that the resistance model can be used as the excitation function of excavator dynamic performance analysis. It has a good reference value to the dynamic performance research of automatic excavator.

The study object is the new controllable machinery loader,the design variable is the key parameters of boom lift branched,and the optimization goal is the least of maximum torque of the first during active-member lifting,and the constraints are overall layout,transmission angle and singularity,then the dimension optimization model of boom lift branched is built. What’s more,by using complex method,the numerical solving on optimization model is carried out and the best dimension parameters of each member of boom lift branched are obtained and the maximum drive torque of first active-member is lowered by 11%. Finally,the virtual prototype simulation based on ADAMS is conducted. The simulation result shows that the dynamics performance of optimized controllable loading mechanism is significantly improved. When boom is at the top position the first active-member is close to the inverse kinematics singular position and the power is reduced by80%. This study will provide a basis for performance promoting of controllable machinery loader.

Because the motor and reducer of the conventional tandem welding robot are installed at the revolute joint, the robot has large rotational inertia and long residual vibration time. However, due to the limitation of workspace and other reasons, the current parallel robot is not suitable for all series welding robots. Therefore, based on the concept of "multi-degree-of-freedom controllable mechanism", a new controllable mechanism welding robot is proposed in this paper. The driving motor and reducer, which have great influence on the main and branch chain of the welding robot, are installed on the frame. The advantage of this design is that the inertia of the robot mechanism is significantly reduced, and its dynamic performance is improved. The position errors of the end members of the welding robot moving along the circle, as well as the angle errors of each joints under the circle movements are analysed.

A kind of parallel series robot is designed,the characteristic are as following: shoulder and elbow joints are transferred out by parallelogram linkages and driven by ballscrew,which makes it own larger rigidity and better dynamic performance. It keeps the good characteristics of larger workspace series robot. The kinematics analysis of this robot is carried out,the workspace is solved by means of an improved way of printing points,and then,the boundary analysis method is proposed to calculate the workspace. The results show that the computation of the boundary analysis method is smaller and the result is clear. The volume and performance index are calculated based on the solved workspace. And it proves that this kind of robot has better workspace property.