Study of the Work of the Length Correction System for a Crawling Robot Changing its Configuration

The article discusses the movement of a three-link crawling robot on a horizontal rough surface, while changing its configuration. The robot contacts the surface in four points where active bearings are in place. The active bearings are designed in such a way that their dry friction coefficient is a controlled quantity, which allows periodically fixing these bearings to the surface. The robot consists of modules, each of which is a translational pair, and the modules are interconnected by two-axis hinges. It is proposed to consider these modules as links of variable length. In the paper, the basic kinematic relationships for this robot were found, a vector of generalized coordinates was specified, and the constraints imposed during the movement were described. The studied here motion corresponds to a scenario where two outer bearings are fixed on the surface, while links execute planar movements from a given initial to the desired final position. The implementation of such a movement requires a change in the lengths of the links (in the simplest case, a change in the length of one link is enough, in the most difficult case, all three are required to change length), for the implementation of which a correction system is proposed. The method considered in the work consists in varying the length of one link, which is the robot body, the movements of the other two links are determined by the operation of the corresponding drives. As a result of numerical simulation, the range of allowable values for the elongation / shortening of the robot body is determined by varying the relative angle between the body and one of the side links in a given range. In addition, four intervals of changes in the relative angles were revealed, at each of which the nature of the variation in the length of the central link differs in the number of maxima and minima achieved. Also, the dependences of the change in the angle of rotation of the side link, at which the length of the body reaches its maximum and minimum lengths, from the previously specified relative angle and time of movement, are constructed. The temporal laws of changes in the rotation angles of the links are given and analyzed. 

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