Biorobotics projects at the University of Moratuwa
View(s):Robots, Robotics, Robotic Technology are well known terms to the modern society, but what is Biorobotics? In short it is the development of biologically inspired robots. In the world-wide context it has become a hot topic over the last decade among reseachers and engineers. As a country where do we stand in this technological saga? This column discusses about biorobotic related projects currently being conducted at University of Moratuwa, Sri Lanka.
Biorobotics deals with emulating or simulating living biological organisms or systems electro-mechanically. It involves a biological creature and in most applications a human being. Therefore, the safety of these systems is paramount. Biorobotics is one of emerging trends in mechanical engineering as well as an emerging area of biomedical engineering. It is a combination of several other sub-disciplines such as mechanics, control engineering, artificial intelligence (AI), etc.
Biorobots can be classified into several categories. In the context of this article three main categories can be identified: robotic prostheses, robotic orthoses and other types. Prosthesis is a device which replaces missing (amputated) body part and orthosis is a wearable device which assists or supports and/or strengthens the existing body part.
Limb amputation or removal of limb parts from the upper or lower extremity is a consequence of trauma, diseases or congenital disorders. A robotic prosthesis is an active device that provides the amputee an opportunity to achieve previously performed functional tasks. Limb impairment due to incomplete spinal cord injury (SCI), brain injury, strokes, multiple sclerosis, muscular dystrophy, etc is also a common form of disability. On the other hand, the world population is also growing old and the elderly being physically weak find it difficult to perform their normal daily activities. In such circumstances, active orthoses can help to ameliorate the impact of impairment or weakness by assistive or supportive means. Moreover, they also serve as devices that help to perform clinical rehabilitation. Simply, robotic prostheses or robotic orthoses (biorobots) can be used to improve the quality of life of amputees or physically impaired/weak individuals as well as make their life more productive to the society.
In the Sri Lankan context, people in every corner of the country have suffered from 30 years of war. Subsequently many lives were lost, both military and civilians alike. Similarly, a considerable number of amputees or physically weak individuals are also present as war causalities. Therefore, post war rehabilitation has become one of the most important duties of the contemporary society. Rehabilitation centres are tirelessly working to provide the required rehabilitation for disabled or amputee population in Sri Lanka. However, there is no evidence of using globally available state-of-the-art technologies by those organizations for rehabilitation. Therefore, a technical gap can be identified in using the available global technology in Sri Lankan context. The biorobotics research projects at University of Moratuwa are intended to propel the required drive to fulfill this gap, with the intention of offering the benefits not only to the locals but also to the regional and global society.
Specific research projects
At the University of Moratuwa’s Faculty of Engineering several departments are carrying out robotics-related research and projects mainly to serve the industry. Considering it a timely need of the country, the Department of Mechanical Engineering has taken pioneering steps towards helping the differently-abled people such as the physically weak individuals as well as the amputees to improve their quality of life. In 2011, a research project on ‘Development of assistive robotic arms’ was initiated with the financial support of the National Research Council (NRC), Sri Lanka. The project is planned to be carried out in several stages and currently in the second stage of development with financial support from both the NRC and Senate Research Council (SRC) of the university.
Generally, robotic hand-prosthesis should be light-weight while providing required dexterity and functionality. In order to arrive at a suitable compromise, researchers are trying to reduce the number of actuators while trying to achieve maximum functionality of the robot. In view of that, under-actuated (lesser number of actuators than the required number of motions or degrees of freedom) mechanisms have being developed and tested. We have developed prototypes of three robotic hand-prostheses for hand amputees, each one using different novel mechanisms. A patent is pending for one of these mechanisms as of present. A methodology has also been proposed to evaluate under-actuated mechanisms. Furthermore, a prototype of trans-humeral prosthesis is also developed for above elbow amputees.
Lower-limb amputation is the most frequently occurring human limb amputation around the world. Explosion of anti-person land mines has annually caused thousands of people to become amputees during different stages of civil war. Most of the effected nations are from developing countries, either in Asian or African region, who has limited access to state-of-the-art technology available in developed countries. In view of this situation, two basic prototypes of lower-limb robotic prostheses have been developed: trans-tibial (below knee) prosthesis and trans-femoral (above knee) prosthesis. These researches have given the required background for further development of the technology. Currently research is undergoing to develop an advanced trans-femoral prosthesis for lower-limb amputees.
Developing upper-limb and lower-limb Exoskeleton Robots for physically weak individuals
External structural mechanism with joints and links corresponding to the human joints and limbs respectively are called exoskeletons. An exoskeleton robot is an active orthosis which can be used for human motion assistance, human power augmentation and clinical rehabilitation. In 2011, a basic prototype of lower-limb exoskeleton robot was developed to assist locomotion of a physically weak person. Currently, research is being carried out to develop an advanced lower-limb exoskeleton robot and its control method. Furthermore, several designs of shoulder exoskeleton robots as well as forearm exoskeleton robots have been proposed and fabricated. At present a research is being carried out to develop a complete upper-limb exoskeleton robot and its control method for the motion assistance.
Biological signal-based robot control
Robotic prosthesis and orthosis will function more effectively if robot controlling is based on the motion intension of their users. In order to extract motion intension accurately, biological signals have been effectively used by researchers across the globe. In simple terms, biological signals are electrical signals generated and transmitted in a biological system. Electromyography signal (EMG) of muscles and Electroencephalogram signals (EEG) are the commonly used biological signals to control robotic prostheses and orthoses. We, at the Department of Mechanical Engineering, are also currently developing controlling methods to manipulate robotic prostheses and orthoses based on human motion intension by capturing biological signals.
(The writer is a Senior Lecturer at the Department of Mechanical Engineering, University of Moratuwa, Sri Lanka. He can be contacted via gopura@mech.mrt.ac.lk or gopura@gmail.com. )