Design and Validation of a Lightweight Parallel Manipulator for Ungrounded 3-DoF Translational Wrist Perturbation with Orientation Sensing
M.C. Weerheim (TU Delft - Mechanical Engineering)
J.P. Meijaard – Mentor (TU Delft - Mechatronic Systems Design)
W. Mugge – Mentor (TU Delft - Biomechatronics & Human-Machine Control)
J.L. Herder – Graduation committee member (TU Delft - Mechatronic Systems Design)
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Abstract
Wearable devices capable of perturbing and measuring wrist orientation during daily activities are essential, as traditional measurement systems are often restricted to controlled environments and limit natural movement. A compact and lightweight 4-RUU parallel manipulator mounted on the wrist can generate ungrounded forces in three translational degrees of freedom, while keeping the hand and arm unobstructed. The inverse kinematics of this mechanism is analytically derived, enabling control with an open-loop feedforward system for the four servo motors for precise perturbations.A simulation of the concept parallel manipulator is used to optimize the main dimensions of the device for the intended application. A prototype is then constructed and evaluated, both for its ability to generate forces using a force sensor and for its ability to measure real-time orientation using an inertial and magnetic measurement unit with an implemented Madgwick filter. The force measurements showed that along every axis and combination of axes, a certain repeatable force generation profile can be distinguished, where a minimal peak of 5.0N is generated. The lack of end-effector acceleration, due to limiting servo performance, resulted in a loss of forces in the mechanism lie between 14–50 %. The orientation estimation is fast and accurate in real time with a maximum total angle error of 5°.