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Pneumatic Touch Sensor

IP.com Disclosure Number: IPCOM000080323D
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 4 page(s) / 84K

Publishing Venue

IBM

Related People

Garrison, RL: AUTHOR [+2]

Abstract

A computer controlled gripper 10 in Fig. 1 includes more than 100 pneumatic snap action sensors 11 on fingers 12, 13. Sensors 11 are 0.1 x 0.1 inch in area. Work 14 is inserted in hole 15 in block 16 resting on surface 17. The fingers 12, 13 follow a sequential search motion under computer control via gimbal and arm mechanisms 18, connected via strain gauges 19 to fingers 12, 13. When work 14 contacts hole 15, the computer employs force distributions on sensors 11 to calculate the approximate position of hole 15, and work 14. Accordingly, the path of fingers 12, 13 is adjusted to insert the work 14 in hole 15. Sensing, calculation and searching are repeated until the workpiece 14 enters the hole 15.

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Pneumatic Touch Sensor

A computer controlled gripper 10 in Fig. 1 includes more than 100 pneumatic snap action sensors 11 on fingers 12, 13. Sensors 11 are 0.1 x 0.1 inch in area. Work 14 is inserted in hole 15 in block 16 resting on surface 17. The fingers 12, 13 follow a sequential search motion under computer control via gimbal and arm mechanisms 18, connected via strain gauges 19 to fingers 12, 13. When work 14 contacts hole 15, the computer employs force distributions on sensors 11 to calculate the approximate position of hole 15, and work 14. Accordingly, the path of fingers 12, 13 is adjusted to insert the work 14 in hole 15. Sensing, calculation and searching are repeated until the workpiece 14 enters the hole 15.

Finger 13 has grasp surface 20, a section 21 of which is shown in enlarged form in Fig. 2A, which is a top view. Fig. 2B shows the sensors 11 of Fig. 2A in a partially sectional schematic side view. Sensors 11 are covered with flexible sheets of insulating skin 31 of rubber, polyurethane, etc., providing a high frictional force between fingers 12, 13 and work 14. Bonded to skin 31 is a thin metal sheet 22 connected to a source of electrical potential. Sheet 22 is bonded to reinforcement members 23 forming plural pneumatic cells 24a, 24b interconnected by holes 25. Air or liquid pressure from source 26 maintains pressure in cells 24a, 24b, adjusted by valve 27 under control of computer 28.

Fig. 3 shows an enlarged section of the switches of Fig. 2 illustrating the application of the principle of elastic stability of a shallow spherical dome.

When a finger contacts work then contact pressure F1, is generated. The skin 31 serves as a soft spring and transmits contact pressure to tributed load pressure, P(L). The thickness, (t), of sheet 22 is very small compared with its radius, (r). Distance, (a), must be greater than eight times distance, h. Geometric parameters, (lambda), and load parameter, (R), are defined as equations (1) and (2), respectively. lambda/2/ = a/2/ over tr square root R(1- upsilon/2/) R = P(L) over E (a over t)/4/ (1-upsilon/2/) (2) where upsilon and E are the Poisson's ratio and the Young's modulos of sheet 22, respectively.

Note that there exist three cases which depend on the value of the geometric parameter lambda; (Ref. 2).

For lambda < 2.08: the metal will deform continuously...