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UDC 621.865.8
THE KINEMATIC STRUCTURE OF THE MECHANISM OF THE EXOSKELETON
Oleg Vladimirovich MALYUGA
OnyxCom LLC Krasnogorsk, Russia oleg@onyxrobot.com
Abstract
The urgency of the development of robotic exoskeletons is substantiated. The task of synthesis of the kinematic scheme of the Executive mechanism of the exoskeleton is set and possible approaches to its solution are defined. The results of kinematic scheme synthesis obtained in CATIA and SolidWorks software systems are presented. The expediency of kinematic synthesis in the SolidWorks software package using anthropometric data proposed by the CATIA software package is substantiated. The obtained ranges of changes in the generalized coordinates of the joints of the actuator, equipped with electrohydraulic servo drives, are compared with similar ranges for humans.
The rapid development of robotics is explained by the need to increase productivity and improve the efficiency of work performed in various fields of human activity, among which the leading place is occupied by work in extreme conditions. This includes the elimination of the consequences of man-made and natural disasters, as well as the solution of problems associated with the manipulation and transportation of specialpurpose cargo in the military field.
Keywords: robotics, tree kinematic structure, synthesis of kinematic scheme, ergonomic design, exoskeleton, degrees of mobility.
Introduction. In most cases, self-propelled wheeled or tracked vehicles with mounted manipulators, surveillance equipment and other equipment are used, but often it is necessary to perform work in buildings, cabins of various equipment, i.e. in conditions initially created for a person, taking into account his kinematics of the body and mass [Antonellis, 2018].
To date, there are many variants of exoskeletons built using different drives (electric drive, hydraulic drive, pneumatic drive), but their practical use is very limited due to the difficulties associated with the onBoard energy source capable of ensuring the autonomy of the exoskeleton. However, this fact serves only as a catalyst for progress and leads to the constant emergence of more and more new variants and versions of exoskeletons. As another reason for the growing popularity of these devices, we should mention the areas of their possible application:
1) the military sphere (possible integration of the armor suit into the exoskeleton, with the aim of removing the loads arising from the ingress of bullets);
2)use by people with physical disabilities (problems supporting-dvigatelnogo);
3) elimination of consequences of various emergency situations (blockages, collapses, landslides,
etc.).);
4) use in conditions of inapplicability of heavy machinery;
5) use in operations where it is possible to replace heavy equipment with human labor (for example, laying railway lines).
Based on the review given in, we can conclude that in Russia there is a significant backlog in this field of technology and the only relevant ongoing development, as far as we can judge, is the project Exoatlet, developed at the Institute of Mechanics of Moscow state University. M. V. Lomonosov [Chaichaowarat, 2018, 5]. Thus, the development of the Executive mechanism (S) of the exoskeleton and the study of its parameters and characteristics seem appropriate and relevant. At the same time, we will use electrohydraulic servo drives (EGS) as drives, since they have suitable dynamic properties and weight and size parameters.
Materials and methods. In the first section, the problem of synthesis of the kinematic scheme (CS) of the exoskeleton is formulated and possible approaches to its solution are determined. The second section
presents the results of synthesis of CS MI obtained in the software package CATIA, studied the mobility of the foot, lower leg and thigh [Chang, 2018, 3]. The third section offers a combination of analysis and development environments, presents the results of synthesis of CS IM obtained in the software package SolidWorks. On the basis of the modeling and anthropometric data the ranges of changes in the generalized coordinates are determined
Results and methods. One of the most important tasks arising in the process of creating an exoskeleton is to analyze the kinematics of THE exoskeleton. The task consists, first of all, in the need to synthesize the exoskeleton COP, fully providing the required degrees of mobility in the process of work, that is, in the process of movement to impose minimal restrictions on a person. This requirement is justified by the fact that in a static position, the force acting on the part of the exoskeleton per person should tend to zero [Chowdhury, 2018].
There are two approaches to solving the problem:
1) the ultimate simplification of the human model (the exclusion of secondary degrees of mobility, by which we mean such degrees of mobility, which do not directly affect the work of a person in a given environment, in other words, "unused" degrees of freedom). This approach has several significant drawbacks: first, IT will be workable only within the given conditions;second,it is not always possible to predict what degrees of freedom to consider secondary; third, it is likely that the design of IM,based on the CS synthesized in this way, will need further refinement in terms of creating additional degrees of mobility. On the other hand, the advantage of this method is the relative simplicity of kinematic analysis, and, as a consequence, the simplicity of COP [Gao, 2018].
2) as accurate as possible reproduction of the behavior of the human body. The disadvantages of this approach are associated with the repeatedly increasing complexity of the human body model, which entails an increase in the complexity of the kinematic structure of the MI, as well as its design. The main advantage of this method is that as a result we get a scheme that accurately corresponds to all human movements. Of course, it is impossible to completely exclude the possibility of the need to Refine the design of MI, but the risk of obtaining a COP, and then the design that does not fully meet the specified conditions, is significantly lower in comparison with the first approach [Harethardottir, 2019, 127].
Thus, the General problem can be formulated as follows: it is necessary to choose or create a model of a person as close to reality as possible, and on its basis to synthesize the CS of an exoskeleton. If necessary, simplification of CS occurs at the design stage [Jang, 2018, 4].
At the initial stage of the study, the model of the human body proposed in the submodule "Human Activity Analysis" of the module "Ergonomics Design & Analysis" of the software complex CATIA (Computer Aided Three-dimensionalInteractive Application) was chosen. This software package takes into account a sufficient number of degrees of human mobility, offers ranges of generalized coordinates of all joints, based on anthropometric studies, and also allows for ergonomic design and has a number of other useful functions [Johnson, 2018].
According to reports in the press, currently the problems with the mechanical part of exoskeletons and their software are solved, although of course there is no limit to the improvement that occurs constantly. A major obstacle to the mass introduction of exoskeletons is the lack of suitable Autonomous energy sources [Li, 2018]. The most modern batteries do not yet provide the exoskeleton with the operating time necessary for their practical application. However, progress in the development of energy sources is very rapid, which provides optimism to developers who still have time to improve their devices. Now two directions of practical use of exoskeletons are emerging: the military, where the us is the undisputed leader, and medical - to help people with disabilities, where great success has been achieved in Japan. There are suggestions that in the future, for expeditions to other planets, space suits with built-in exoskeletons will be developed as well. to work and carry on itself on the surface of Mars, together with the spacesuit, and even the life support system, astronauts will be quite difficult [Rodriguez-Ugarte, 2018]. If we talk about modern military developments, it is also worth mentioning the system HULC (Human Universal Load Carrier), which deals with the giant aerospace industry Lockheed Martin. It was also reported that the Russian military Department is interested in the development of this technology, financing the work on the equipment "Fighter-21" which will include elements of exoskeletal structures.
A Japanese company with an interesting name Cyberdyne offered a commercial sample of this exoskeleton. Yes, now these machines from the future, helping people in all sectors of life, is not fiction.
Necessary here to note that the exoskeletons of the modern is quite effective. They can significantly increase the load on the human body [Schweighofer, 2018]. Modern samples of the Hal exoskeleton can increase the weight lifted by a person by 100%. And this is only the beginning of the evolution of such devices. According to the company developer Cyberdyne, exoskeletons should significantly improve the lives of workers in factories that work every day with heavy and dangerous goods.
The main purpose will be military. And developments in this direction, of course, are underway. Only civilian models are on the market today, but who can guarantee that special military modifications will not be developed? Just imagine what the benefits would be to have such soldiers in real combat [Shen, 2018]. They will be able to carry an unaffordable for an ordinary person, the weight on themselves. A large quantity of ammunition, goods, or medications. I think that 6 people in such devices will be able to lift cars on the hands.
But we must understand that it would not be possible to create exoskeletons without related research. In areas such as neurology, robotics, IT, physiology, psychology, law and the entire field of social Sciences. Exoskeletons work on the following principle: it has built-in special sensors that track signals from the brain to the muscles. Thus, the system will know which areas need to be activated at the moment. Therefore, he acts synchronously with the person.
Results and discussion. The only thing that remains unclear is the Autonomous power supply. After all, surely such technologies consume electricity in large quantities. How long can an exoskeleton work without an external power source? That's the main question that Cyberdyne, the company has not given response [Wang, 2018].
Structurally, this principle can be described as follows — a person wears an exoskeleton with bioelectric sensors, gravity sensors, power drives, a battery and a computer with wireless communication. And although all this weighs a lot, a person does not feel any load, because it is distributed only within the exoskeleton. The system can increase the muscular strength of the arms and legs, for example, will allow lifting weights above 40 kg, while for a person such a load will be invisible. One of the most important elements of such designs are bioelectric sensors that read the impulses supplied from the brain to the muscles. Data from these sensors is fed to the computer, where they are converted into commands for the power drives of the exoskeleton [Wu, 2018].
Fig. 4. Layout of the main elements of the system
It is worth looking at what is an exoskeleton that is about to appear on the battlefield. The basis of the device are two "legs", made of light, but very durable titanium alloy. The" muscles " of the exoskeleton are hydraulic systems, and lithium-ion batteries are used as a source of energy. The capabilities of the exoskeleton HULK is really impressive — the total raised with it, a person can weigh 140 lbs. the Only condition required to properly distribute the load on the apparatus. For example, on the rear frame of the exoskeleton can be hung a load weighing up to 100 kg, the additional load should be placed on the shoulders of the "Hulk".
An important parameter of the exoskeleton is its battery life. And here the Hulk is at a fairly high level-the battery charge will be enough to move at a speed of 4 kilometers per hour for five hours [Yue, 2018]. That is, the exoskeleton will allow you to make a March to a distance of twenty kilometers.
Fig. 5. Human Universal Carrier (HULC)
Game manipulator in the form of1' hands " exoskeleton. Kinect for Xbox 360-unattainable technological top among game controllers? This may be the case at the moment, but Novint is working on a device that could change that view. It is called the XlO and is a robotic "hand", similar to a part of a futuristic exoskeleton.
The device is put on your hand and functions as a game manipulator. XlO tracks hand movements, transforming them into actions controlled by the player character. And to increase the degree of immersion in the role, the gadget is equipped with a force feedback mechanism, the work of which is manifested in the form of vibrations.
Novint has not yet announced for which platforms, in addition to the PC, Xio is intended, and the price has not yet been determined. But the controller was originally conceived as a commercial product, so the prototype has all the chances to get to the buyers [Wu, 218, 9]. The company also expects that XIO will be used for purposes other than gaming. This includes medicine, robotics, scientific visualization, exercise, training simulations for the military.
Fig. 6. Novint XIO
Exoskeletons are created to increase the muscular strength of a person and are intended mainly for two categories of users: for those who need rehabilitation for diseases of the musculoskeletal system, as well as for workers of physical labor. In this case, the exoskeleton can not cover the whole body, but only a certain part of it. For example, the hand, as in the case with the mechanism of x-Ar from Equipois company.
Conclusion. The synthesis method makes it possible to successfully solve the problems of synthesis of CS robots with a tree kinematic structure, but the design of machines designed for humans, accompanied by a number of difficulties associated with the need to take into account such specific requirements as ergonomics, biological limitations of mobility in the joints, restrictions on the maximum speed of movement and acceleration of the links of the human body, greatly complicating the process of final refinement of the designed machine.
Proposed in the present work the method of synthesis of KS THEY exoskeleton allows the conceptual design phase to perform different variants of KS and for each of them to the ranges of the generalized coordinates of the joints, the comparison of which with the same ranges for the person allows the developer to evaluate one or another of the COP. Since at the stage of CS synthesis only its geometrical dimensions, as well as the type and position of the degrees of mobility are important, the developer can quickly and with minimal effort to analyze a particular CS, which allows to prepare the final version of the CS before the start of the detailed design process.
References
1. Antonellis, P., Galle, S., De Clercq, D., & Malcolm, P. (2018). Altering gait variability with an ankle exoskeleton. PLoS One, 13(10), e0205088. doi:10.1371/journal.pone.0205088
2. Chaichaowarat, R., Kinugawa, J., & Kosuge, K. (2018). Cycling-enhanced Knee Exoskeleton Using Planar Spiral Spring. Conf Proc IEEE Eng Med Biol Soc, 2018, 1-6. doi:10.1109/EMBC.2018.8512862
3. Chang, S. H., Zhu, F., Patel, N., Afzal, T., Kern, M., & Francisco, G. E. (2018). Combining robotic exoskeleton and body weight unweighing technology to promote walking activity in tetraplegia following SCI: A case study. J Spinal Cord Med, 1-4. doi:10.1080/10790268.2018.1527078
4. Chowdhury, A., Nishad, S. S., Meena, Y. K., Dutta, A., & Prasad, G. (2018). Hand-Exoskeleton Assisted Progressive Neurorehabilitation using Impedance Adaptation based Challenge Level Adjustment Method. IEEE Trans Haptics. doi:10.1109/TOH.2018.2878232
5. Gao, B., Wei, C., Ma, H., Yang, S., Ma, X., & Zhang, S. (2018). Real-Time Evaluation of the Signal Processing of sEMG Used in Limb Exoskeleton Rehabilitation System. Appl Bionics Biomech, 2018, 1391032. doi:10.1155/2018/1391032
6. Harethardottir, H. M., Male, R., Nilsen, F., Eichner, C., Dondrup, M., & Dalvin, S. (2019). Chitin synthesis and degradation in Lepeophtheirus salmonis: Molecular characterization and gene expression profile
during synthesis of a new exoskeleton. Comp Biochem Physiol A Mol Integr Physiol, 227, 123-133. doi:10.1016/j.cbpa.2018.10.008
7. Jang, J., Lee, J., Lim, B., & Shim, Y. (2018). Natural gait event-based level walking assistance with a robotic hip exoskeleton. Conf Proc IEEE Eng Med Biol Soc, 2018, 1-5. doi:10.1109/EMBC.2018.8513066
8. Johnson, A. P., Gorsic, M., Regmi, Y., Davidson, B. S., Dai, B., & Novak, D. (2018). Design and Pilot Evaluation of a Reconfigurable Spinal Exoskeleton. Conf Proc IEEE Eng Med Biol Soc, 2018, 17311734. doi:10.1109/EMBC.2018.8512642
9. Li, Z., Li, J., Zhao, S., Yuan, Y., Kang, Y., & Chen, C. L. P. (2018). Adaptive Neural Control of a Kinematically Redundant Exoskeleton Robot Using Brain-Machine Interfaces. IEEE Trans Neural Netw Learn Syst. doi:10.1109/TNNLS.2018.2872595
10. Rodriguez-Ugarte, M., Ianez, E., Ortiz, M., & Azorin, J. M. (2018). Improving Real-Time Lower Limb Motor Imagery Detection Using tDCS and an Exoskeleton. Front Neurosci, 12, 757. doi:10.3389/fnins.2018.00757
11. Schweighofer, N., Wang, C., Mottet, D., Laffont, I., Bakhti, K., Reinkensmeyer, D. J., & Remy-Neris, O. (2018). Dissociating motor learning from recovery in exoskeleton training post-stroke. J Neuroeng Rehabil, 15(1), 89. doi:10.1186/s12984-018-0428-1
12. Shen, Y., Ma, J., Dobkin, B., & Rosen, J. (2018). Asymmetric Dual Arm Approach For Post Stroke Recovery Of Motor Functions Utilizing The EXO-UL8 Exoskeleton System: A Pilot Study. Conf Proc IEEE Eng Med Biol Soc, 2018, 1701-1707. doi:10.1109/EMBC.2018.8512665
13. Wang, D., Meng, Q., Meng, Q., Li, X., & Yu, H. (2018). Design and Development of a Portable Exoskeleton for Hand Rehabilitation. IEEE Trans Neural Syst Rehabil Eng, 26(12), 2376-2386. doi:10.1109/TNSRE.2018.2878778
14. Wu, Q., & Wu, H. (2018). Development, Dynamic Modeling, and Multi-Modal Control of a Therapeutic Exoskeleton for Upper Limb Rehabilitation Training. Sensors (Basel), 18(11). doi:10.3390/s18113611
15. Wu, Q., Wang, X., Chen, B., & Wu, H. (2018). Patient-Active Control of a Powered Exoskeleton Targeting Upper Limb Rehabilitation Training. Front Neurol, 9, 817. doi:10.3389/fneur.2018.00817
16. Yue, C., Lin, X., Zhang, X., Qiu, J., & Cheng, H. (2018). Design and Performance Evaluation of a Wearable Sensing System for Lower-Limb Exoskeleton. Appl Bionics Biomech, 2018, 8610458. doi:10.1155/2018/8610458
