GB2152473A

GB2152473A - Improvements in compliant devices

Info

Publication number: GB2152473A
Application number: GB08400767A
Authority: GB
Inventors: Duc Truong Pham
Original assignee: British Nuclear Fuels Ltd
Current assignee: British Nuclear Fuels Ltd
Priority date: 1984-01-12
Filing date: 1984-01-12
Publication date: 1985-08-07
Also published as: GB8400767D0; GB2152473B

Abstract

A compliant device for insertion between an end of a manipulator arm and a tool, the device comprising a plurality of pairs of helicoil assemblies 21,22 secured at their opposite ends in respective rigid coupling means 1,2 attachable to the end of the manipulator arm and the tool, adjacent assemblies of neighbouring pairs being inclined such that the axes of the adjacent assemblies meet at points on a circle with the centre of the circle defining the centre of compliance of the device. <IMAGE>

Description

SPECIFICATION Improvements in compliant devices The present invention concerns compliant devices, these being devices as used in robotics for the manipulation and positioning of workpieces.

The task of inserting pegs in holes is a common occurrence in the assembly of mechanical components. It occurs, for example, when fitting pistons into cylinders, inserting shafts into bearings and locating wheels on spindles. When performing such relatively straightforward operations automatically and by remote control difficulties and problems arise if the component parts are not in accurate alignment and orientation. A compliant device included between a robot arm and a robot hand for gripping the workpiece can cater and compensate for such misalignments. The compliant device is analogous to the wrist of a human operator. For further discussion of compliant devices attention is directed to an article entitled "A compliant device for inserting a peg in a hole" appearing in "The Industrial Robot" of June 1979.

According to the present invention there is provided a compliant device for insertion between the end of a manipulator arm and a tool at said end of the arm, the device comprising a plurality of pairs of resiliently flexible members secured at their opposite ends in respective rigid coupling means attachable to the end of the manipulator and the tool, adjacent members of neighbouring pairs being inclined such that the axes of said adjacent members meet at points on a circle with the centre of said circle defining the centre of compliance of the device.

Conveniently the device comprises three pairs of resiliently flexible members with the axes of the adjacent inclined members of neighbouring pairs meeting at three separate points forming the apices of an equilateral triange with the centre of gravity of the triangle coincident with the centre of compliance of the device.

Preferably the resiliently flexible members comprise helicoil assemblies, each assembly comprising two helicoils, being a hollow cylindrical body with a continuous spiral slot therein extending over a portion of the length of the body between its ends, interconnected at their adjacent ends.

Preferably, the centre of compliance is arranged to lie at the tip of a workpiece to be carried in the tool.

The invention will be described, by way of example, with reference to the accompanying drawings; in which: Figure 1 is a general view of an embodiment of a compliant device according to the invention Figure 2 is a side view of a portion of the device in Figure 1 and partly in section.

A compliant device as illustrated comprises plates 1 and 2 interconnected by helicoil assemblies 3. For convenience and to conform with the drawings the plate 1 is termed the upper plate and the plate 2 is termed thel lower plate. These terms do not imply or suggest the relative positions of the plates in operation of the device which is capa ble of functioning in any orientation or disposi tion.

Each helicoil assembly comprises two helicoils 4 and 5 which are interconnected at their adjacent ends by a stub 6. Each helicoil is in effect a hollow cylindrical body with a continuous spiral slot extending about and through the wall thickness of the body and extending over a portion of the length of the body intermediate its ends. Each helicoil so formed functions in the manner of a spring.

Further stubs 7 and 8 are secured in and extend from the opposite ends of the helicoils 4 and 5 respectively. The stub 7 is journalled in a deep groove bearing 10 which comprises first and second portions 11 and 12 respectively, which are respectively located, fitted and positioned in corresponding matching recesses in the opposite surfaces of the upper plate 1. The end of the stub 7 protruding beyond the bearing 10 is secured by a locknut 13. The stub 8 at the opposite end of the helicoil assembly 5 is secured in the lower plate 2 by a locknut 14.

A tool in the form of a gripper 15 is mounted on the upper plate 1. The tool can comprise a pneumatic or hydraulic cylinder 16 which is located in an opening or aperture in the plate 1 and carries a transverse beam on its end above the plate. Two gripper arms 17 are pivotally connected at their ends to the transverse beam. A piston (not shown) within the cylinder has a piston rod or plunger 18 which is pivotally connected by a transverse end piece 19 to positions substantially midway between the ends of the gripper arms. Reciprocating motion of the piston rod or plunger effects opening and closing of the jaws of the gripper. Fluid inlet and outlet connections 20 are provided at opposite ends of the oylinder.

The helicoil assemblies are arranged in symmetrical, equi-angularly spaced pairs. The illustrated embodiment comprises three pairs, only two of which indicated by reference numerals 21 and 22 are clearly visible in Figure 1. The ends of the helicoils in each pair are closer together at the lower plate 2 than at the upper plate I with the result that they diverge. Consequently, the adjacent helicoil assemblies of neighbouring pairs are inclined towards each other and when the device is in its natural undeformed state the axes of the inclined assemblies meet in pairs at three separate points forming the apices of an equilateral triangle the centre of gravity of which is the centre of compliance of the device.

The lower plate 2 is provided with means for securing it to the end of an arm of a robot, such as a manipulator as used behind shielding walls in the nuclear industry. The compliant device is analogous to a wrist between the end of the arm and the hand as represented by the gripper.

1. A compliant device for insertion between the end of a manipulator arm and a tool at the end of the arm, the device comprising a plurality of pairs

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in compliant devices The present invention concerns compliant devices, these being devices as used in robotics for the manipulation and positioning of workpieces. The task of inserting pegs in holes is a common occurrence in the assembly of mechanical components. It occurs, for example, when fitting pistons into cylinders, inserting shafts into bearings and locating wheels on spindles. When performing such relatively straightforward operations automatically and by remote control difficulties and problems arise if the component parts are not in accurate alignment and orientation. A compliant device included between a robot arm and a robot hand for gripping the workpiece can cater and compensate for such misalignments. The compliant device is analogous to the wrist of a human operator. For further discussion of compliant devices attention is directed to an article entitled "A compliant device for inserting a peg in a hole" appearing in "The Industrial Robot" of June 1979. According to the present invention there is provided a compliant device for insertion between the end of a manipulator arm and a tool at said end of the arm, the device comprising a plurality of pairs of resiliently flexible members secured at their opposite ends in respective rigid coupling means attachable to the end of the manipulator and the tool, adjacent members of neighbouring pairs being inclined such that the axes of said adjacent members meet at points on a circle with the centre of said circle defining the centre of compliance of the device. Conveniently the device comprises three pairs of resiliently flexible members with the axes of the adjacent inclined members of neighbouring pairs meeting at three separate points forming the apices of an equilateral triange with the centre of gravity of the triangle coincident with the centre of compliance of the device. Preferably the resiliently flexible members comprise helicoil assemblies, each assembly comprising two helicoils, being a hollow cylindrical body with a continuous spiral slot therein extending over a portion of the length of the body between its ends, interconnected at their adjacent ends. Preferably, the centre of compliance is arranged to lie at the tip of a workpiece to be carried in the tool. The invention will be described, by way of example, with reference to the accompanying drawings; in which: Figure 1 is a general view of an embodiment of a compliant device according to the invention Figure 2 is a side view of a portion of the device in Figure 1 and partly in section. A compliant device as illustrated comprises plates 1 and 2 interconnected by helicoil assemblies 3. For convenience and to conform with the drawings the plate 1 is termed the upper plate and the plate 2 is termed thel lower plate. These terms do not imply or suggest the relative positions of the plates in operation of the device which is capa ble of functioning in any orientation or disposi tion. Each helicoil assembly comprises two helicoils 4 and 5 which are interconnected at their adjacent ends by a stub 6. Each helicoil is in effect a hollow cylindrical body with a continuous spiral slot extending about and through the wall thickness of the body and extending over a portion of the length of the body intermediate its ends. Each helicoil so formed functions in the manner of a spring. Further stubs 7 and 8 are secured in and extend from the opposite ends of the helicoils 4 and 5 respectively. The stub 7 is journalled in a deep groove bearing 10 which comprises first and second portions 11 and 12 respectively, which are respectively located, fitted and positioned in corresponding matching recesses in the opposite surfaces of the upper plate 1. The end of the stub 7 protruding beyond the bearing 10 is secured by a locknut 13. The stub 8 at the opposite end of the helicoil assembly 5 is secured in the lower plate 2 by a locknut 14. A tool in the form of a gripper 15 is mounted on the upper plate 1. The tool can comprise a pneumatic or hydraulic cylinder 16 which is located in an opening or aperture in the plate 1 and carries a transverse beam on its end above the plate. Two gripper arms 17 are pivotally connected at their ends to the transverse beam. A piston (not shown) within the cylinder has a piston rod or plunger 18 which is pivotally connected by a transverse end piece 19 to positions substantially midway between the ends of the gripper arms. Reciprocating motion of the piston rod or plunger effects opening and closing of the jaws of the gripper. Fluid inlet and outlet connections 20 are provided at opposite ends of the oylinder. The helicoil assemblies are arranged in symmetrical, equi-angularly spaced pairs. The illustrated embodiment comprises three pairs, only two of which indicated by reference numerals 21 and 22 are clearly visible in Figure 1. The ends of the helicoils in each pair are closer together at the lower plate 2 than at the upper plate I with the result that they diverge. Consequently, the adjacent helicoil assemblies of neighbouring pairs are inclined towards each other and when the device is in its natural undeformed state the axes of the inclined assemblies meet in pairs at three separate points forming the apices of an equilateral triangle the centre of gravity of which is the centre of compliance of the device. The lower plate 2 is provided with means for securing it to the end of an arm of a robot, such as a manipulator as used behind shielding walls in the nuclear industry. The compliant device is analogous to a wrist between the end of the arm and the hand as represented by the gripper. CLAIMS

1. A compliant device for insertion between the end of a manipulator arm and a tool at the end of the arm, the device comprising a plurality of pairs of resiliently flexible members secured at their opposite ends in respective rigid coupling means attachable to the end of the manipulator and the tool, adjacent members of neighbouring pairs being inclined such that the axes of said adjacent members meet at points on a circle with the centre of said circle defining the centre of compliance of the device.

2. A compliant device as claimed in claim 1 comprising three pairs of resiliently flexible members with the axes of inclined members of neighbouring pairs meeting at three separate points forming the apices of an equilateral triangle with the centre of gravity of the triangle coincident with the centre of compliance of the device.

3. A compliant device as claimed in claim 1 or 2 in which the resiliently flexible members comprise helicoil assemblies, each assembly comprising two helicoils, being a hollow cylindrical body with a continuous spiral slot therein extending over a portion of the length of the body between its ends, interconnected at their adjacent ends.

4. A compliant device substantiall,y as herein described with reference to and as illustrated in the accompanying drawings.