The chapter approaches the issues of modeling the process of load lifting by a person while wearing an exoskeleton. The classification of existing gravitational compensation systems for industrial exoskeletons is shown, as well as examples of its use. A mathematical model of lifting a person's load in the exoskeleton is presented, as well as numerical parameters are calculated. It is shown that the introduction of an elastic element reduces the level of energy consumption during work, and can also facilitate the level of the worker. Industrial exoskeleton prototype design is presented. A particular focus is given to studying the influence of the gravity compensator on the magnitude of the moments generated by the electric drives of the hip and knee joints. It is shown that the use of gravity compensators enables to reduce significantly the load on electric drives.
Top1. Introduction
A person’s manual labor can be considered as a workload performed by a person in this type of operation, and the functional stress of the body as an integral response of the body to the load. The workload is a combination of factors of the workflow, performed under certain conditions of the production environment (Pons, 2008; Anam & Al-Jumaily, 2012; RViteckova et al., 2013; Arisumi et al., 2008). The labor severity is understood as a degree of cumulative impact of working conditions on the functional state of the human body, his health and performance, on the process of reproduction of labor power and safety. The severity of work is determined by the degree of stress on the human muscular system. Since a person experiences particular stress during loading and unloading (lifting) operations, so the working conditions can be attributed to extreme ones, which lead to a decrease in a person’s working capacity, causing functional changes that exceed the limits of the norm, but do not produce pathological changes. In some cases, there are super-extreme working conditions, causing pathological changes in a human body that makes impossible to complete the workload.
It is necessary to create comfortable working conditions, ensuring optimal working efficiency and maintaining a person’s health, or at least such conditions, which provide a given performance and maintain the health, and at the same time do not cause inner discomfort and abnormal functional changes. One of the ways to solve this problem is the use of an exoskeleton - external skeleton that supports and protects a body. Particularly effective are industrial exoskeletons allowing to carry out complex movements of both lower and upper extremities (Gou et al., 2014; Kajita et al., 2001), so they are able to expand significantly human capabilities, including loading and unloading operations.
Currently, industrial exoskeletons Fortis (by Lockheed Martin), HAL (Cyberdyne), Atoun (Panasonic) and others are becoming more and more common in the market. They find practical application (Sellaouti & Stasse, et al., 2006), significantly enhancing human capabilities in terms of facilitating movement, weight transfer and various types of activities that require considerable effort, as is shown in Figure 1. Particularly effective are the exoskeletons that allow performing complex types of movement of both lower and upper extremities, which significantly expands the human capabilities when performing cargo handling operations.
Figure 1. Industrial active exoskeletons Atoun model Y and Cyberdyne HAL-LB03
The carbon fiber frame gives Atoun Model Y exoskeleton longevity and lightness, it can be worn outdoors and in rainy weather due to its waterproof and dustproof.
Recently, the development of exoskeletons with passive elements of gravity compensation has been embarked on. The term «gravity compensation» is used to designate the properties of individual links of the mechanism to have a statically stable position, independent of the vertical traverse of the links. For an external observer, the movement of these links of the mechanism looks as if the gravitational field did not act on them. Issues related to the design of mechanisms similar to those presented in this section, especially the optimal choice of parameters and the location of elastic elements, are the subject of research conducted by a number of scientists (Bosch et al., 2016; Mooney & Luke et al., 2014; Anam & A-Jumaily, 2012; Jatsun & Savin et al., 2016).