An Efficient Insertion Control Method for Precision Assembly of Cylindrical Components

In this paper, an efficient insertion control strategy is presented for precision assembly of cylindrical components with interference fit. It has two inherent advantages compared with existing insertion methods in the domain of precision assembly. First, it does not need preparatory actions dedicated for horizontal forces before insertion actions, which is realized by integrating the preparations into the insertion step. Second, instead of inserting with fixed incremental depth, it estimates the insertion depth for every action to be as large as possible with a probabilistic approach. Specifically, the insertion of components is modeled as a stochastic state transition process with the uncertainty described by Gaussian distribution. The state transition function is well defined based on analysis of the historical assembly data and the universal mechanical properties of the components. An assessment function is also elaborately designed to evaluate the performance of the state transition function in order to stimulate the control strategy to behave progressively or conservatively. Finally, the action to be taken for the current state is decided by iterative calculations in N steps estimation manner. An automatic assembly system is developed to verify the effectiveness of the proposed control method. Experimental results show that the assembly process with the proposed insertion control strategy can finish within 30 steps, which is at least four times more efficient than the process with the traditional method.