Positional Accuracy Analysis in Serial Chain and Four-Bar Closed Chain Manipulator

Serial chain robots are integral part of industrial automation. Better reach within workspace, higher Degree of Freedom (DoF), flexibility and positional accuracy are credit performance features behind its wide acceptance. The flexibility and higher DoF of this configuration is underutilized, when it is used for a repetitive task in hard automation. The present paper considers application of closed chain four-bar mechanism as substitute of a serial chain robot for repetitive task involving single trajectory generation. The manipulators are modelled for positional accuracy under the influence of joint clearances and drive backlash. The positional error in both manipulators for a coupler point on sample path is estimated. The manipulators are considered to operate with identical input constraints. The error is expressed in terms of dimensionless number-as Error Index to estimate the comparative behaviour of the manipulators. The paper presents method of analysing the performance of a closed chain manipulator over serial robot.