МАШИНОСТРОЕНИЕ И МАШИНОВЕДЕНИЕ STUDY OF THE DYNAMICS OF THE EXOSKELETON ACTUATING UNIT

. A person has more than 300 degrees of mobility, but it is practically impossible to recreate such a kinematic scheme. In this article, a kinematic scheme of the exoskeleton is proposed that is most necessary for human movement. A 3D model of the exoskeleton actuating unit with an electrohydraulic drive has been developed in the CAD system and the values of masses, coordinates of mass centers, inertia tensors of the links of the exoskeleton actuating unit have been calculated. A launch file has been developed in the MATLAB environment for modeling the dynamics of the exoskeleton actuating unit. The control laws in the degrees of mobility of the actuating unit of the exoskeleton are selected. As a result of the theoretical study, the ranges of changes in the generalized coordinates for the joints under study are determined. The dependences of the power and the moment in the joints 9, 10 on time are obtained. The conducted studies have shown that lifting the leg will require more energy and this makes it necessary to develop power plants, explore various types of drives and ways to control them energy-efficiently. The obtained data can serve in the development of a medical exoskeleton.

The proposed kinematic scheme can be represented by a directed reachability graph, where the vertices of the graph denote the links of the actuator, and the arcs-the joints connecting them [7]. The kinematic scheme of the exoskeleton and its 3D model are shown in Fig. 1 and 2 respectively.
In mathematical description of the kinematic structures of the AU of the robot is represented as a tree of directed graphs, we use the following definitions [7,8,9]: f(i) is the number of the link, is a link-father of link i; s(i,k) is the number of the link, which is the kth link-son for level i; dg+(i) -polysterene the outcome of the link i, determines the number of links-the sons of link i; ns(i) -determines how the account link in the son is the link i to link your father; σ_i={0,1} -the coefficient that determines the type of joint of the link i (1-rotational, 0-translational); σ_i=diag{σ_1, ... σ_N } is a diagonal matrix that defines the types of articulation of the links of the tree AU.
For a mathematical description of a tree structure, they need to determine the order of the links relative to each other. It is defined by the reachability matrix D -a square matrix, each element of which dij = 1 if the link i-th vertex of the directed graph describing the kinematic structure AU is reachable from the link j, and dij = 0 if the link i-th is not reachable from the link [9]. The values of the modified Denavit -Hartenberg parameters for the main and auxiliary coordinate systems of the exoskeleton actuating unit are presented in Tables 1 and 2.   Initial data for calculating the dynamics of the exoskeleton AU [8,9]:  parameters of AU links: mass, tensors of inertia, coordinates of the centers of mass of links, obtained from the results of 3D -modeling of the structure;  coordinates of points of application of external forces;  coordinates of points of overlapping of external connections.
1. Let us express the efforts developed by the drives in terms of generalized coordinates and their derivatives [11]. By grouping the factors at q  and q  , an equation for the dynamics of the robots AU with tree -like CS determined by the reachability matrix of D links, a block vector 0 z and a diagonal matrix  is obtained: In these expressions: In the process, the movement of the active exoskeleton of its foot interacts with the supporting surface. Then the equation of the dynamics of the exoskeleton AU, taking into account the influence of external forces and moments, as well as the imposed external kinematic connections, can be written in the following form: where q -the vector of generalized coordinates of the AU; τ -a column vector of moments developed by AU drives.
The values of the remaining block vectors and matrices of equation (2) are determined in accordance with [9,11].
Determine the following parameters of the links:  mass;  coordinates of the centers of mass of the links in the connected main CS of these links;  tensors of inertia of the links relative to the CS, the axes of which are parallel to the axes of the main connected CS of these links, and the origin of coordinates is in the AU of the links;  coordinates of the points of application of external forces to the links of the actuating unit in the connected main CS of these links;  coordinates of the points of application of reaction forces to the links of the mechanism in the connected main CS of these links.
The mass-inertial parameters of the exoskeleton AU were obtained from the results of 3D modeling in the SolidWorks system.
Mass-inertial parameters of the AU links of the exoskeleton: Table 3 Mass-inertial parameters of links 9, 10 In order to determine the laws of change of generalized coordinates in the degrees of mobility of the executive mechanism of the exoskeleton equipped with drives, the characteristic typical movements of the human operator performed by changing the generalized coordinate ( ( )) i  (angle) were considered in time in the corresponding joint in the previously defined range according to the harmonic law of the form [12,13]: Main part. The dependence of the power in the joint on time was built, taking into account the reaction of the support in the MATLAB bundled software. The desire to reduce power consumption forces designers to develop power units, explore various types of drives and ways of energy efficient control of them [3,9].
The proposed method for calculating the energy parameters of the exoskeleton, used in [14,15,16] by the method of CS synthesis of the exoskeleton AU, allows for the entire process of product development.

Conclusions.
One of the critical parameters of the exoskeleton is the power consumption, which, in turn, determines the degree of its autonomy. The desire to reduce power consumption leads developers to design compact power plants, explore different types of drives and ways to manage them energy-efficiently. There is an obvious need to use methods that allow us to quickly determine the energy parameters of the AU as a function of many factors. The proposed method of calculation of power parameters of the exoskeleton used in conjunction with described in [17,18] method of synthesis of the kinematic scheme AU exoskeleton allows for the entire process of product development, starting from the stage conceptual design, when possible operational changes to the decisions, with a minimum of effort to predict the energy characteristics of actuators, to track the impact of changes in AU, and to evaluate different design options. The results can be used in the development of medical exoskeletons for the rehabilitation of the lower extremities of patients.