Hand neuro-rehabilitation system using Nitinol spring actuators
Introduction
Hand mobility may be reduced by various causes, a physical impairment due to a trauma or a neurophysiological problem due to a cerebrovascular accident (CVA), such as a stroke. In the case of a neurophysiological problem, when a person loses control over the movements of his hands, he must undergo a rehabilitation program in order to recover the mobility. This kind of rehabilitation usually consists in flexion and extension exercises of the fingers and wrist rotation exercises [1]. In cases where the injuries are too severe, the patient may not fully recover the mobility of his hands and/or fingers or take a long time to recover it. Therapy becomes a repetitive task where the amplitude of the movements and pressure on the patient’s muscles are increased during its evolution [2]. Typically, the first phase of recovery is the execution of passive exercises, which seeks to reduce spasticity, and once normalized the muscle tone the next step is to recover the grip and strength of the hand [3].
From this point of view, a robotic device to assist passive rehabilitation therapy would avoid the therapist performing these exercises, which consist in moving the joints of the hand to gradually expand the range of lost joint motion and gradually smooth muscle tension following a stroke. This would facilitate the work of the physiotherapist since they only have to adapt the rehabilitation device to the patient and then program and execute the therapy.
To be affordable for a large number of rehabilitation centers, hospitals, and individuals, it is necessary that the device has a moderate price, which is achieved by using low-cost materials and actuators and free software tools for system programming and therapy monitoring. In the case of the actuators, there are currently some commercial devices with this approach and others under investigation, such as HEXXOR [2], Hand Mentor [4], HandSOME [5], Amadeo Hand Rehabilitation [6] and the NESS H200 [7]. One of the problems with the robotic rehabilitation devices is the compliance behavior due to the use of electrical motors. Some other actuation schemes have been tested, like the pneumatic actuation [8]. For this reason in this research project Nitinol springs actuators are used as an alternative to motors and pneumatic systems as they require no maintenance and they weigh less and are smaller than other conventional actuation systems, considering that in the present application neither too much force on the system or a very fast response speed is required. The software application developed allows adjusting the main parameters considered in a rehabilitation therapy, permitting the physiotherapist to program the exercises used during the therapy, and once the therapy has started the patients’ recovery can be monitored using a simple and intuitive user interface that makes it pleasant and easy to use the robot.
This article is divided in 3 sections. Section 1 contains the introduction, Section 2, which comprise the device design process, is divided into 6 subsections; Section 2.1 is about the mechanical design to extend and flex the fingers, Sections 2.2 Shape memory alloys SMA, 2.3 Experimentation process with Nitinol are about shape memory alloys and the experiments performed with them, respectively, Section 2.4 presents the data acquisition card used and the conditioning card designed for the system, Section 2.5 is about the control system employed in the manipulation of the power given to the Nitinol springs, and Section 2.6 shows the design and components of the user interface for programming the therapies. In Section 3 are the experimental process with the finished device and later the observations of the design and construction process. In Section 4 are the conclusions. Finally, there are the acknowledgments and the references.
Section snippets
Device design process
As a starting point, it is relevant to mention that the design of the mechanical device and the software interface used to develop the therapies were based on suggestions given by two professors of the University of Cauca’s physical therapy program, who informed about the fundamental movements required to reduce the spasticity in a patient and the protocol involved in the treatment and monitoring of strokes.
Results
In order to check the performance of the designed device, some experiments were done.
First one is related with the demonstration that the 1 d.o.f. for each phalanx is enough for some neurorehabilitation therapies. Five () sane subjects were instructed to put their right arm over the device and to show none resistance to the motion of the device. All were healthy, with no major cognitive or physical deficits. They were aged between 24 and 41, mean age 31 years, median age 29 years, and
Conclusions
This article presented the design and construction of a hand rehabilitation system built with Nitinol springs actuators. The aspects taken into account in designing the mechanism for extending the joints of the fingers were described and a study of shape memory alloys (SMA), and in particular how the Nitinol can be used as an actuator, was presented. The design presented incorporated these actuators to perform hand rehabilitation therapy, recommended by physiotherapists.
A description of the
Acknowledgments
The authors acknowledge the suggestions and recommendations for the user interface and programming exercises to the Physical Therapy Department, University of Cauca, Colombia. This work has been supported by the CYTED action 509AC0372—Opensurg.
Jose M. Sabater-Navarro is an Associate Professor at the Department of Systems Engineering and Automation, and a researcher of the Neuroengineering biomedical Group (Nbio). He graduated in Industrial Engineering (with intensification in Energy Technology) in 1998 at the Polytechnical University of Valencia, where he received a grant for Young researchers at the Chemical Institute (ITQ) CSIC-UPV, and he obtained his Ph.D. at Miguel Hernandez University in 2003, with a doctoral thesis about
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Jose M. Sabater-Navarro is an Associate Professor at the Department of Systems Engineering and Automation, and a researcher of the Neuroengineering biomedical Group (Nbio). He graduated in Industrial Engineering (with intensification in Energy Technology) in 1998 at the Polytechnical University of Valencia, where he received a grant for Young researchers at the Chemical Institute (ITQ) CSIC-UPV, and he obtained his Ph.D. at Miguel Hernandez University in 2003, with a doctoral thesis about haptics devices and man–machine interfaces.
His research focuses within the subjects of medical robotics and medical images. His main interest is about surgical robotics, rehabilitation robotics and medical computer applications for health. His contributions about the interaction between the patient and the robot have received several prizes and have been published in several journals. Some of these contributions have been developed as invention patents and are being commercialized by health companies. He is author of more than 30 original contributions in international journals with impacts, and he has been principal investigator on several international and national projects.
Since 2009 he is the Vice-Director of the Polytechnic School of Elche and, since 2012 he is the Director of the Máster on Industrial Engineering. He has been a guest editor on several journal, like Computer Methods and Programs in Biomedicine and Medical and Biological Engineering and Computing. He has been a main coordinator of several International Research Networks on Bioengineering, mainly with Latin America.
Nicolas García Aracil is an Associate Professor of Control and Systems Engineering at Miguel Hernandez University (Spain). He holds an M.Sc. in Control Engineering by the University of Murcia (1996, Spain), Master in Design, Robotics and Industrial Automation from University of Murcia (Spain) 1996–1997 and a Ph.D. in Control Engineering by the Miguel Hernandez University of Elche (Spain). He has been appointed as a Visiting Scientist at INRIA (Institut National de Recherche en Informatique et en Automatique), Sophia Antipolis, FRANCE, in 2003 and at Institute of Robotics and Mechatronics, DLR, Oberpfaffenhofen-Wessling, Germany, in 2006. His current research interests are medical and surgical robotics, rehabilitation robotics, medical image, computer vision, human–robot interaction and design and control of new robotic devices. Dr. Nicolas Garcia was a 2004 recipient of the Best Thesis in Robotics, National Research Prize, from the Spanish Federation of Automatic control. He is author or co-author of a broad range of research publications. He served as the Program Chair of the 2012 IEEE International Conference on Biomedical Robotics and Biomechatronics (BIOROB, Roma, Italy) and the General Chair of EURON Winter School on Rehabilitation Robotics (Elche, Spain).
Daniel Ramos Tovar is an M.Sc. student of the Universidad del Cauca, Popayán, Colombia. He studied electronics and automation, and his interests are on robotics applied to rehabilitation and medical applications. He is currently funding an SME in Colombia for developing medical applications.
Luis Eduardo Camayo Gómez is an M.Sc. student of the Universidad del Cauca, Popayán, Colombia. He studied electronics and automation, and his interests are on robotics applied to rehabilitation and medical applications. He is currently funding an SME in Colombia for developing medical applications.
Oscar Andrés Vivas Alban is Electronic and Telecommunication Engineering, University of Cauca, Popayán, Colombia, 1989. M.S. in Automatics, Ecole Centrale de Nantes, Nantes, France, 2001. Ph.D. in Automatic Systems and Microelectronics, Laboratoire d´Informatique, Robotique et Microélectronique de Montpellier, Montpellier, France, 2004. He is the leader of group of industrial automatics of the Universidad del Cauca.