A Simple Method to Increase Resolution of Trajectory Parameters for 2-DOF Systems Operating in Cyclic Synchronous Position Mode

In EtherCAT networks operating in Cyclic Syn-chronous Position (CSP) mode, drive systems typically receive only position reference from the master. In cost-sensitive applications, where controlled motors are equipped with low-resolution position sensors, using simple differentiation to obtain velocity and acceleration commands from position reference leads to signals of poor resolution. Subsequently, these signals cannot be reliably used in the feedforward part of a two degrees of freedom (2-DOF) control scheme. This paper presents a simple method to improve the resolution of the velocity and acceleration command signals when computed only from position reference. The proposed solution leads to control performances similar to cases where the velocity and acceleration commands are com-puted accurately using a drive's built-in trajectory generator. Two additional filtering options are detailed. Practical experiments demonstrate the viability of the proposed approach.