Abstract
This paper presents a novel parallel manipulator with one translational and two rotational (1T2R) degrees of freedom that can be employed to form a five-degree-of-freedom hybrid kinematic machine tool for large heterogeneous complex structural component machining in aerospace field. Compared with serial or parallel machine, hybrid machine has the merits of high stiffness, high speed, large workspace, and complicated surface processing ability. To increase stiffness, three-degree-of-freedom redundantly actuated and overconstrained 2PRU-PRPS parallel manipulator (P denotes the active prismatic joint) is proposed, which is utilized as the main body of hybrid machine. By resorting to the screw theory, the degree of freedom of the proposed mechanism is briefly addressed including the initial configuration and general configuration and validated by Grübler-Kutzbach (G-K) equation. Next, kinematic inverse solution and parasitic motion of the parallel manipulator are deduced and the transformational relations between the Euler angle and Tilt-Torsion (T-T) angle are identified. Thirdly, the performance evaluation index of orientation workspace is introduced, and the reachable workspace and joint workspace are formulated. Through specific examples, the reachable workspace, task workspace, and joint workspace of the redundant actuation parallel manipulator are depicted. Compared with overstrained 2PRU-PRS parallel manipulator, corresponding analyses illustrate that the proposed parallel manipulator owns much better orientation capability and is very meaningful to the development of the five-axis hybrid machine tool.
Highlights
Parallel kinematic manipulator tools were claimed to possess the inherent advantages such as high stiffness, high loading capability, high precision, low error accumulation, quick response speed, and high orientation capability
This paper presents a novel parallel manipulator with one translational and two rotational (1T2R) degrees of freedom that can be employed to form a five-degree-of-freedom hybrid kinematic machine tool for large heterogeneous complex structural component machining in aerospace field
There is a contradiction between workspace and precision and stiffness for free surface machining by using the traditional series or parallel machine tool, and they cannot be able to satisfy requirements of the high speed milling for large heterogeneous complex surface in aerospace
Summary
Parallel kinematic manipulator tools were claimed to possess the inherent advantages such as high stiffness, high loading capability, high precision, low error accumulation, quick response speed, and high orientation capability. The five-axis series CNC machine, adding two-degreeof-freedom rotating head attached to its mobile platform or two-degree-of-freedom rotary tables on the three-axis machine, can maintain the favourable orientation, but often scarified certain workspace, and may cause poor precision and stiffness by increasing the length of the actuator to enlarge the workspace [5, 6]. There is a contradiction between workspace and precision and stiffness for free surface machining by using the traditional series or parallel machine tool, and they cannot be able to satisfy requirements of the high speed milling for large heterogeneous complex surface in aerospace. It is of importance to explore a design approach for solving the required reachable workspace to envelope the task workspace, which will offer an ideal solution for machining [8]
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