Encoderless position control of a two-link robot manipulator

Encoders have been an inseparable part of robots since the very beginning of modern robotics in the 1950s. As a result, the foundations of robot control are built on the concepts of kinematics and dynamics of articulated rigid bodies, which rely on explicitly measuring the robot configuration in terms of joint angles - done by encoders. In this paper, we propose a radically new concept for controlling robots called Encoderless Robot Control (EnRoCo). The concept is based on our hypothesis that it is possible to control a robot without explicitly measuring its joint angles, by measuring instead the effects of the actuation on its end-effector. To prove the feasibility of this unconventional control approach, we propose a proof-of-concept control algorithm for encoderless position control of a robot's end-effector in task space. We demonstrate a prototype implementation of this controller in a dynamics simulation of a two-link robot manipulator. The prototype controller is able to successfully control the robot's end-effector to reach a reference position, as well as to track continuously a desired trajectory. Notably, we demonstrate how this novel controller can cope with something that traditional control approaches fail to do: adapt on-the-fly to changes in the kinematics of the robot, such as changing the lengths of the links.