EP-4741113-A2 - DESIGN METHOD FOR DESIGNING PARALLEL LINK MECHANISM

Abstract

In a parallel link mechanism (9), a distal end side link hub (13) is coupled to a proximal end side link hub (12) via three link mechanisms (14) such that a posture of the distal end side link hub (13) can be changed. Each link mechanism (14) includes a proximal side end link member (15), a distal side end link member (16), and a center link member (17), and forms a quadric chain link mechanism (14) composed of four revolute pairs. A singular point occurs when a central axis (QA, QB) of the proximal or distal end side link hub (12, 13) and a central axis (O2, O3) which is a rotation axis of a revolute pair section of the proximal or distal side end link member (15, 16) and the center link member (17) coincide with each other. An axis angle (γ) of the center link member (17) is specified such that a posture in which the singular point occurs is avoided.

Inventors

• ISOBE, HIROSHI

Assignees

• NTN Corporation

Dates

Publication Date

20260513

Application Date

20220920

Claims (3)

1. A design method for designing a parallel link mechanism comprising, the parallel link mechanism comprising; a proximal end side link hub; a distal end side link hub; and three or more link mechanisms couples the distal end side link hub to the proximal end side link hub such that a posture of the distal end side link hub can be changed relative to the proximal end side link hub, wherein each of the link mechanisms includes: a proximal side end link member rotatably coupled at one end thereof to the proximal end side link hub; a distal side end link member rotatably coupled at one end thereof to the distal end side link hub; and a center link member rotatably coupled at both ends thereof to other ends of the proximal and distal side end link members, when at least a central axis of a revolute pair section of the proximal side end link member and the center link member and a central axis of the proximal end side link hub or a central axis of a revolute pair section of the distal side end link member and the center link member and a central axis of the distal end side link hub coincide with each other, a singular point occurs, an angle formed by the central axis of the revolute pair section of the center link member and the proximal side end link member and the central axis of the revolute pair section of the center link member and the distal side end link member is an axis angle γ of the center link member, the axis angle γ of the center link member is set such that a posture in which the singular point occurs is avoided, and when a maximum bending angle which is a maximum value of a bending angle between the central axis of the proximal end side link hub and the central axis of the distal end side link hub is denoted by θmax, a relational expression of (y/2 + θmax/2) < 90 is satisfied.
2. The design method for designing the parallel link mechanism as claimed in claim 1, wherein the maximum bending angle θmax which is the maximum value of the bending angle between the central axis of the proximal end side link hub and the central axis of the distal end side link hub is 90° or larger.
3. The design method for designing the parallel link mechanism as claimed in claim 1 or 2, wherein the axis angle γ is 90° or smaller.

Description

CROSS REFERENCE TO THE RELATED APPLICATION This application is based on and claims Convention priority to Japanese patent application No. 2021-158340, filed September 28, 2021, the entire disclosure of which is herein incorporated by reference as a part of this application. BACKGROUND OF THE INVENTION (Field of the Invention) The present invention relates to a parallel link mechanism and a link actuating device to be used, for example, in equipment that requires high speed, high precision, and a wide operating range such as medical equipment and industrial equipment such as automatic deburring machines. (Description of Related Art) Patent Document 1 discloses a work device that performs predetermined work by a parallel link mechanism that includes a base plate and a traveling plate, couples these plates by a plurality of links, and moves the traveling plate by coordinated operation of these links. Patent Document 2 discloses a link actuating device that is compact but capable of operating at high speed and high precision over a wide operating range. [Related Document] [Patent Document] [Patent Document 1] JP Laid-open Patent Publication No. 2000-094245[Patent Document 2] US Patent No. 5893296 In the parallel link mechanism of Patent Document 1, the operating angle of each link is small. Therefore, it is necessary to increase the link length in order to set the operating range of the travelling plate to be large. Accordingly, the dimensions of the entire mechanism are increased, and the size of the device is increased. In addition, when the link length is increased, the rigidity of the entire mechanism may be reduced. Therefore, the weight of a tool to be mounted on the travelling plate, that is, the weight capacity of the travelling plate, is also limited to a small value. In the configuration of the parallel link mechanism and link actuating device shown in Patent Document 2, the singular point of the parallel link mechanism is not clear, and without analysis using a 3D model or confirmation using an actual machine, it is not known whether a singular point exists in the operation range of the parallel link mechanism and the link actuating device. Therefore, a movement range that is equivalent to a maximum bending angle of 90° or larger and that is wider than the movement range established by experience cannot be achieved. SUMMARY OF THE INVENTION An object of the present invention is to provide a parallel link mechanism and a link actuating device that have a wide operating range while achieving downsizing. A parallel link mechanism of the present invention comprising: a proximal end side link hub;a distal end side link hub; andthree or more link mechanisms which couples the distal end side link hub to the proximal end side link hub such that a posture of the distal end side link hub can be changed relative to the proximal end side link hub, whereineach of the link mechanisms includes: a proximal side end link member rotatably coupled at one end thereof to the proximal end side link hub; a distal side end link member rotatably coupled at one end thereof to the distal end side link hub; and a center link member rotatably coupled at both ends thereof to other ends of the proximal and distal side end link members,when at least a central axis of a revolute pair section of the proximal side end link member and the center link member and a central axis of the proximal end side link hub ora central axis of a revolute pair section of the distal side end link member and the center link member and a central axis of the distal end side link hubcoincide with each other, a singular point occurs,an angle formed by the central axis of the revolute pair section of the center link member and the proximal side end link member and the central axis of the revolute pair section of the center link member and the distal side end link member is an axis angle γ of the center link member, andthe axis angle γ of the center link member is set such that a posture in which the singular point occurs is avoided. Here, the "singular point" refers to a structurally uncontrollable posture. A singular point in a general vertical articulated robot refers to a posture in which multiple arms are aligned in a straight line. With this configuration, the proximal end side link hub, the distal end side link hub, and the three or more link mechanisms form a two-degrees-of-freedom mechanism in which the distal end side link hub is rotatable about two mutually orthogonal axes, relative to the proximal end side link hub. In other words, the proximal end side link hub, the distal end side link hub, and the three or more link mechanisms form a mechanism that allows the distal end side link hub to rotate with two degrees of freedom to change its posture, relative to the proximal end side link hub. This two-degrees-of-freedom mechanism is compact in size, and also, can achieve a wide range of movement for the distal end side link hub relative to the proxim