3D model of two links of the supporting leg of the exoskeleton with variable length and adjustable stiffness

The article considers a model of the supporting leg of an exoskeleton containing two links of variable length in three-dimensional space. The novelty of this model lies in the use of magnetic rheological fluid in the link in a section of variable length in order to control and regulate the stiffness of the link. Such a model will make it possible to create more comfortable exoskeletons, in comparison with those currently available, whose movements are close to those of the human musculoskeletal system. Using local coordinate systems, a system of differential equations of motion is compiled in the form of Lagrange equations of the second kind. A control model is proposed based on specifying the synthesis of motion in the form of differentiable periodic functions and determining the control moments and longitudinal forces from the system of equations of motion. The dynamics of the link is analyzed. The obtained results of numerical simulation are presented graphically. The requirements for the loads that arise during the movement of the link and which the magnetic rheological fluid must satisfy are formed. It has been established that they are achieved when an external magnetic field is applied. Therefore, the proposed model of a link of variable length with adjustable stiffness can function in the exoskeleton of the supporting leg, to which the main load is applied at the moment of repulsion and in the single-support phase of movement.