Method for stress-free assembly of components

• US 6,378,190 B2
• Filed: 12/11/2000
• Issued: 04/30/2002
• Est. Priority Date: 03/11/1996
• Status: Expired due to Term

• Current Assignee: Fanuc Robotics America Incorporated (Fanuc Corporation)
• Original Assignee: Fanuc Robotics America Incorporated (Fanuc Corporation)
• Inventors: Akeel, Hadi A.
• Primary Examiner(s): Hughes, S. Thomas
• Assistant Examiner(s): Hong, John C.
• Application Number:
  US09/734,534
• Publication Number:
  US 20010000271A1
• Time in Patent Office: 505 Days
• Field of Search: 294/070.8, 294/071, 297/14, 294/070.1, 744/71.R, 744/71.XY, 744/790.1, 744/90, 744/900.5, 744/900.6, 744/900.7, 744/900.1, 738/620.44, 738/620.43
• US Class Current: 29/407.08
• CPC Class Codes: A61B 2034/304 including a freely orientable platform, e.g. so called 'Stewart platforms'
• CPC Class Codes: B23P 19/105 using sensing means
• CPC Class Codes: B25J 17/0216 comprising a stewart mechanism
• CPC Class Codes: Y10T 29/49776 Pressure, force, or weight determining
• CPC Class Codes: Y10T 29/4978 Assisting assembly or disassembly
• CPC Class Codes: Y10T 29/49895 Associating parts by use of aligning means [e.g., use of a drift pin or a "fixture"]
• CPC Class Codes: Y10T 29/53022 with means to test work or product
• CPC Class Codes: Y10T 29/53039 with control means energized in response to activator stimulated by condition sensor
• CPC Class Codes: Y10T 29/53061 Responsive to work or work-related machine element
• CPC Class Codes: Y10T 29/53065 with means to fasten by deformation
• CPC Class Codes: Y10T 29/53091 for work-holder for assembly or disassembly
• CPC Class Codes: Y10T 29/53709 Overedge assembling means
• CPC Class Codes: Y10T 74/20299 Antirattling elements
• CPC Class Codes: Y10T 74/20305 Robotic arm
• CPC Class Codes: Y10T 74/20329 Joint between elements
• CPC Class Codes: Y10T 74/20335 Wrist
• CPC Class Codes: Y10T 74/20341 Power elements as controlling elements

Abstract

An apparatus and a method for compliant positioning of an object during an assembly operation wherein the apparatus includes a base plate, a locator plate for mounting an object such as a clamp or a tool spaced from the base plate and a plurality of linear actuators connected between the base plate the locator plate by universal joints providing six degrees of freedom of movement. According to the apparatus and the method a control is connected to the actuators for selectively moving the locator plate to a predetermined position relative to the base plate for contacting a component to be assembled with an object mounted on the locator plate. Two or more of the actuators can be mechanically coupled to move the locator plate with less than six degrees of freedom. The control is responsive to a force applied to the locator plate through the object during assembly of the component for actuating the linear actuators to change the applied force.

Claims

1. A method for stress free assembly of sheet metal components on assembly fixtures including at least one programmable fixture having actuators responsvie to position control signals from a controller, clamping means for clamping the components to the assembly fixtures and tooling operable on and capable of displacing the components during assembly and generating forces supported by the fixtures, comprising the steps of:

a. generating control signals from a controller to move at least one actuator and position a fixture at a predetermined location;

b. placing at least two components on the fixture at the predetermined location;

c. clamping the components to the fixture;

d. actuating tooling to assemble the components, the tooling generating forces supported by the fixture and tending to displace the components from the predetermined position;

e. sensing the forces supported by the fixture during actuation of the tooling and generating force signals indicative of a magnitude and direction of the forces;

f. communicating the force signals to the controller; and

g. operating the controller to move the actuator in a direction to reduce the forces below a desirable limit to providing a stress free assembly of the components.

2. The method according to claim 1 wherein the step e. is performed by a force sensor measuring at least one of six generalized force components X,Y,Z,M_x,M_y AND M_z in a generalized cartisian coordinate system.

3. The method according to claim 1 wherein the step e. is performed by a position encoder coupled to the actuator for generating an output signal representing movement of the actuator in response to the forces.