Design and analysis of a novel 3T1R four-degree-of-freedom parallel mechanism with infinite rotation capability

Abstract

A 4-degree-of-freedom (DOF) parallel mechanism with 3 translations and 1 rotation (3T1R) has wide application potential in the industry. However, most of the existing 3T1R parallel mechanisms have limited rotation capacity of the moving platform, which is usually less than ±90°. In this paper, a new type of 3T1R parallel mechanism is designed by configuration deduction method based on the 3T1R parallel mechanism studied at present. The structure of the parallel mechanism is simple and symmetrical, and the motion pairs are all rotating pairs, which have Selective Compliance Assembly Robot Arm motion and complete rotation capability. Firstly, the branch motion spiral system is established by using the screw theory, and then the constraint spiral of each branch to the motion platform is solved, and the constraint spiral system is analyzed, so as to determine the number of DOFs and properties of the mechanism. Secondly, the position, velocity, and singularity of the mechanism are analyzed, and the workspace of the mechanism is analyzed by the positive position solution. Then, the trajectory planning of operation space is completed, and a mathematical model of portal grasping trajectory is established. Thirdly, the kinematic simulation analysis of the mechanism is carried out. Finally, an equal scale physical model was made by 3D printing technology to verify the rationality of the design and the correctness of the theoretical analysis.

Kinematics and singularity analysis of a novel hybrid industrial manipulator

“…It is to be noted that, for the reasons stated earlier 6 on Page 6, the limb lengths L 2 and L 3 are only taken to be positive. 11 This completes the inverse kinematics for the lower parallel mechanism since there are now the values for θ 1 , θ 2 , θ 3 , L 2 and L 3 . Further, the numeric T 1num matrix can be obtained by substituting all these values in the symbolic form of T 1 .…”

“…Also, now the values of θ 1 , θ 2 , and θ 3 can be substituted into Eqs. ( 10) and (11) to obtain the leg length vectors, and then L 2 and L 3 can be calculated using Eqs. ( 12) and ( 13), respectively, as:…”

“…However, they suffer from reduced as well as more complex overall workspace. A significant amount of research has been done on the design and kinematic analysis [1][2][3][4][5], as well as on the determination of workspace and singularities [1,3,[5][6][7][8][9][10][11][12][13] of parallel manipulators. Based on different applications, numerous lower mobility parallel manipulators have been designed [1-5, 12, 13], in which the moving platform either purely translates [1][2][3]12], or purely rotates [4,5,13], or else performs a combined translational and rotational motion [14].…”

“…Each of the θ 's can take any value from [−π , π ], and thus, the second solution as tan has a period of π 11. Moreover, L 2 and L 3 can only be negative together at the same time, that is, it cannot be that one of them is negative and the other is positive.…”