Delay handling for an adaptive control of a remotely operated robotic manipulator

This paper presents a time delay analysis of an adaptively controlled two link rigid Revolute-Revolute joint type manipulator when the device is remotely triggered or controlled. Such a manipulator could be connected to the internet and is controlled by a remote user through an internet server. However a delay is produced when the feedback signals reach the controller at the user's end. This delay is often found to severely pull down the accuracy of the manipulator in terms of its ability to execute a trajectory. The deviation from the desired to the drawn trajectory in this paper is calculated using the Hausdorff metric. Analysis with several values of delay clearly depicts an increase in inaccuracy of the output with increasing delay. The variation of the Hausdorff error with changes in control parameters of the system is also described. It is found that there exists a critical delay value above which the system practically fails to complete the objective. The dynamic equations of motion of the system have been formulated using the Lagrange-Euler method. A PD feedback controller is used for control. This analysis and determination of the critical delay is crucial for remotely triggered devices and will find application in the control of tele-robots.