Design and fabrication of a passive upper limb rehabilitation robot with adjustable automatic balance based on variable
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(2020) 42:629
TECHNICAL PAPER
Design and fabrication of a passive upper limb rehabilitation robot with adjustable automatic balance based on variable mass of end‑effector Majid Eslami1 · Ali Mokhtarian1 · Mostafa Pirmoradian1 · Alireza Seifzadeh2 · Masoud Rafiaei3 Received: 25 April 2020 / Accepted: 28 October 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract The purpose of this work is to design and fabricate a balanced passive robotic arm with the capability of applying variable mass to the end-effector in order to upper limb rehabilitation. To achieve this purpose, the first step is associated with establishing a robot structural design in the CAD environment. The next step is focused on developing the kinematic model based on the degrees of freedom and joint range of motion of the lower legs. Thereafter, the potential energy functions are determined for the springs and weight of components applied in the mechanism. The genetic algorithm is employed as a proper optimization program to extract the system design parameters, including the spring stiffness coefficients and their placement positions within the system. A prototype is fabricated for a balanced robot, and the end-effector mass variations are utilized to develop an adjustable balance capability. To create balance in the system, several items are designed, consisting of a control panel, two electric motors, and an electronic processor. This situation provides an equivalent force equal to the weight of selected mass from the end-effector to the user’s hand. (It is done by a reverse process.) The actual mass required for robot balance is compared to the mass defined in the simulation environment. The evaluation results indicate that it is possible to create an optimized balance by using the simulation outputs. Keywords Passive robot · Automatic balance · End-effector’s variable mass · Control panel · Rehabilitation robotics List of symbols a1 The first joint distance from spring junction a2 The second joint distance from spring junction b1 The distance of mass center of the first arm from its joint b2 The distance of mass center of the second arms from its joint C1 The mass center of the first link C2 The mass center of the second link Technical Editor: Adriano Almeida Gonçalves Siqueira. * Ali Mokhtarian [email protected]; [email protected] 1
Department of Mechanical Engineering, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr, Isfahan, Iran
2
Department of Biomedical Engineering, Khomeinishahr Branch, Islamic Azad University, Khomeinishahr, Isfahan, Iran
3
School of Rehabilitation, Isfahan University of Medical Sciences, Isfahan, Iran
d1 The adjustment parameter of the first spring d2 The adjustment parameter of the second spring e The error function of control g The gravity acceleration k1 The first spring stiffness coefficient k2 The second spring stiffness coefficient l1′ The first arm length l2′ The second arm length m1 The mass of the first arm m2 The mass
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