A method to calculate the required work time is proposed for parts alignment robots that consist of two robots to perform bin-picking multiple types of general-shaped parts and aligning them on a pallet via a belt conveyor. The proposed method calculates the total work time required for parts to be aligned at all locations on the pallet, in which the state transition with success probability, the resource assigning coefficients to represent the work time ratios of the robots, and the state transition velocity diagram are introduced, and the part staying time on the conveyor belt is assumed to be infinite. With these treatments, the total work time is expressed as a function of the resource assigning coefficients, so that the expected value of the shortest total work time can be obtained as the optimum solution using the minimax method. Then, the implementation algorithm of parts alignment work is embodied for the case where the part staying time on the belt conveyor is finite. By comparing the average and the expected values of the total work time, the proposed method has been confirmed to be appropriate.
