Research On Peg-in-hole Assembly Strategy Of Force Control Robot Based On Spiral Search

Assembly is the follow-up process of product production and an important link in industrial production.With the aging of society and the increase of labor cost,it is urgent to develop robot compliant automatic assembly technology.Aiming at the problem that direct assembly may lead to failure or even damage parts due to the position deviation of peg and hole in robot automatic peg-in-hole assembly.Based on the feedback of the six-dimensional force sensor installed at the end of the robot,this paper proposes a force feedback peg-in-hole compliant assembly strategy based on Archimedes spiral search.This strategy is not only suitable for round shaft hole assembly,but also for square hole assembly.In this paper,the assembly process is divided into four stages: positioning of the peg-hole,searching outside the hole,adjusting in the hole,and inserting.It focuses on the research of the assembly strategy of precision peg-hole parts without chamfering and with small tolerances under large position errors.The main difficulty lies in the two stages of searching outside the hole and adjusting inside the hole.Then,the commonly used hole search strategy of robot is analyzed theoretically,and its advantages and disadvantages are summarized.An improved out of hole search strategy of robot under admittance control,namely tilted-Archimedes spiral search,is proposed.Secondly,the control strategy of the force-controlled robot in the hole adjustment stage is discussed.The contact state in this phase is modeled and analyzed,which simplifies the identification algorithm and adjustment strategy of the contact state in the traditional force feedback assembly.Then the core adjustment strategy is applied to the more complex square peg-in-hole assembly.The identification algorithm and adjustment strategy of contact state in the adjustment stage of square peg-in-hole assembly are proposed.Finally,an experimental platform was built to apply the assembly strategy on the Daming robot,and experiments were carried out for the peg-in-hole assembly tasks of round and square.Experiments show that this strategy can well adapt to the position error and direction error that occur in the assembly process,and the force data collected during the assembly process is analyzed to verify the effectiveness of the strategy.Then,the round peg-in-hole assembly strategy is compared with the traditional direct the spiral search assembly strategy is used for non-parametric comparative statistical experiments.The results show that the assembly strategy has strong adaptability to errors,high assembly success rate and stable performance.