| Low-DOF(degree of freedom) serial robot has found a wide application in the field of engineering. Compared with the 6-DOF serial robot, its advantages of simple structure, low cost in design and control and its feasibility have already been accepted. However, the design of low-DOF serial robot configuration depends on the designers' experience and intuition too much, without a reliable method and scientific procedures to follow.This paper focuses on structural synthesis of Low-DOF serial robot mechanism and aims to establish a universal and effective structural synthesis theory, and then analysis the singularity of acquired mechanisms. The main contributions are as follows:Firstly, based on the linear dependency of constraint screws under different geometrical conditions and the required DOF type of mechanism, a new classification of constraint screw system is proposed and the corresponding constrained motion is obtained by reciprocal relations between twists and wrenches. Further, the DOF type of anticipant mechanism is analyzed.Some practical constraint conditions are introduced into the structural synthesis theory out of the engineering consideration, in order to assure that each synthetical mechanism can be solved in closed-form.Then, based on the classification of constraint screw system, the universal and effective structural synthesis theory of low-DOF serial robot mechanism is established.The structural synthesis of 5-DOF, 4-DOF and 3-DOF serial robot is performed using structural synthesis theory. 108 kinds of 5-DOF, 84 kinds of 4-DOF and 25 kinds of 3-DOF serial robot mechanisms are obtained. And the structural characteristics of low-DOF serial robot mechanisms are revealed systematically.At last, the square Jacobian matrix of low-DOF serial robot is established using screw theory, and the condition of existing singularity is solved on this basis. Under such singularity, the linear dependency of joint screws is analyzed using Grassmann line geometry method. |
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