| The type of traditional industrial robots mainly is series-robot. This type of robot has large workspace, but the cumulative error is also large, which restricts the development to the direction of higher precision. Besides, higher moment of inertia and lower dynamics performance will occur because of the driving device fixed on the joint. Compared with the serial mechanism, the parallel mechanism has a higher stiffness and compacter structure, while the workspace of it is decreased. In view of this situation, a kind of 6-DOF mobile manipulator is designed, which can slither along the lead rail. The work-scope will be expanded further by means of movable base. The new type of double parallelogram mechanism, driven by two ball-screws, is applied to improve the stiffness of the mobile manipulator’s structure. Driving devices on the joint generally have larger quality, but the application of the ball-screws will transfer the driving devices, which used to be on the shoulder joint and elbow joint, to somewhere near the rotating center. Then, the rotating-radius and height of the devices will be largely decreased, and dynamics performance will be ameliorated. Meanwhile, this kind of mobile manipulator not only processes all the good properties discussed above, but also has larger workspace, pretty property of workspace and excellent flexibility.Kinematics, trajectory planning, solution and performance of workspace, mechanism performance and dynamics will be discussed in this paper. Analysis of kinematics will be done by solving the forward and inverse kinematics equations in ways of D-H method, which is the foundation of the following research. Research of trajectory planning is mainly focused on task-space and joint-space. Firstly, one representative spiral trajectory is planned in task-space, based on which time-series of joint angle in joint-space are obtained by inverse kinematics equations. Then, trajectory planning can be done by high-order polynomial fitting. "Ergodic Method" and "Boundary Method" will be proposed during the procedure of workspace’s solution, and comparison is going to be done in the following steps. Lastly, performance of the workspace will be studied. In order to study the mechanism performance further, influence coefficient is going to be proposed to study the properties of velocity, accelerate and dexterity intensively. Finally, the analysis of mechanism dynamics and numerical simulation will be carried out, by which the rules of joints driving torque can be got. This also verifies the trajectory planning results the other way round. |
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