Force sensorless control with 3D workspace analysis for haptic devices based on delta robot

Recently, the human-robot interaction systems are extending their capability to work in many applications. Appropriate haptic devices or robot systems have an important role to support the collaboration task which require close interaction between human and robot. This paper proposes a novel 3D parallel mechanism delta robot based on Kalman filter based state observer for the haptic devices. In the mechanical design, a 3D parallel mechanism delta robot contains three identical and symmetrical upper-arm and fore-arm of parallel links that are connected to the base plate with motor at lower end and to the end-effector with a ball joint at top end. The delta robot are designed and analyzed in order to realize a 3D motion in the workspace of the robot's end-effector. In the controller design, Kalman filter based state observer, (KFSO) can be applied to estimate an external torque of motor. With such a force sensorless control scheme based on the feedforward disturbance torque compensation loop, significant high bandwidth haptic sensing in a delta robot system can be achieved. The proposed method has been successfully applied in a real delta robot system in order to show its applicability. The experimental results of the rehabilitation robot are provided to illustrate the performance of the proposed algorithms. In the experimental results, the system was able to estimate a 3D motion and external force in the workspace of the robot's end-effector.