Efficient Insertion of Multiple Objects Parallel Connected by Passive Compliant Mechanisms in Precision Assembly

This paper proposes an efficient strategy to simultaneously insert multiple objects, which are parallel connected by passive compliant mechanisms, in precision assembly. The distinctions of this task include: each object is held compliantly; multiple objects are parallel connected to a manipulator; not all the peg-in-hole has the same insertion condition; and high accuracy is required for each insertion. This configuration can provide sufficient compliance and improve insertion efficiency for massive precision assembly. We model the relationship between the state and force of a single compliant mechanism, and analyze the horizontal compliance of parallel mechanisms. Based on the model, with a fitting and optimization method the states of all but one compliant mechanisms are acquired from microscopic views and the remaining states are optimized with resultant forces provided by a force sensor. To efficiently plan the parallel insertion, we propose a strategy to horizontally compensate according to the resultant force and the horizontal compliance, and to vertically insert based on the insertion ratio expectation, the horizontal offsets of each individual insertion, and the horizontal force. Experiments are carried out to demonstrate the validation of the proposed method.