ROBOTIC ASSEMBLY OPERATION STRATEGY INVESTIGATION WITHOUT FORCE SENSORS THROUGH THE RESEARCH ON CONTACT POINT LOCATION AND RANGE OF PEG MOVEMENT

The assembly operation plays an important role in manufacturing indust ry. The robotic peg-hole insertion operation, the most widely used ass embly model, has been heavily studied due to its widespread applicatio n. The purpose of the research in this area is to design techniques th at enable the robot to perform assembly operations with high speed, hi gh accuracy and low cost. The key problems of strategy investigation r esearch include: (a) designing a series of sub-goals through which the peg-hole system can achieve she insertion operation from any point in the initial area, (b) calculating the allowable range for the initial area, (c) determining the values and duration of the control inputs a nd (d) analysing the robustness of the strategy. There are many strate gies given to perform the assembly operation with the assistance of sp ecially designed force sensors or flexible wrists. In this paper:1. Th e map from the position of the peg in the coordinate frame attached to the hole and the location of the contact point in the frame attached to the peg was analysed. This provided the basis for the identificatio n of the position relationship between the peg and the hole using a fo rce sensor signal. 2. The range of peg movement was analysed and found to be useful in the selection of the sub-goals for the insertion oper ation. 3. A deficient and yet precise hardware strategy, characterized by not requiring force sensors or flexible wrists, was analysed. 4. T he validity of the deficient hardware strategy was demonstrated throug h experiments with the UMI-RTX robot. The results were further confirm ed through simulation. The allowed initial area, the control input des ign and the robustness of the strategy were analysed in detail. A cons tant cycle time of 2.5 s was achieved during the ten trials in which t he diameters of the pegs were selected from a choice of 29.99, 31.98 o r 31.99 mm with a clearance between the hole remaining at 0.02 mm and a common peg legnth of 41 mm.