The problems of designing a hexapod control system - a mechanism with parallel kinematics, designed for guidance and positioning of instruments and antennas of orbiting satellite platforms are considered. Based on the solution of the extended kinematics problem, the algorithm for controlling linear drives with a kinematic pair of screw-nut and two two-axis hinges is specified. The hexapod control scheme with the spatial load position sensor is given, the feasibility of positional control algorithms is estimated on the basis of the modern domestic element base. The estimation is made by the method of mathematical modeling. An algorithm for adaptive neural network control of a hexapod is proposed. An artificial neural network has been developed, which together with a nonlinear controller regulates the force acting on linear actuators by control error. To assess the quality of hexapod control, a dynamic model of the hexapod control system was created in the simulation package SimMechanics of the MATLAB Simulink system. A description is given of the hardware part of the digital control system-the hexapod control unit).

This research is a part of the work implemented by BSTU “VOENMEH” under the financial support of the Ministry of Education and Science of the Russian Federation for design and development of a precision mechanism with the parallel kinematics called “Hexapod”. The object of research is the mechanism, in which the control of leg lengths is implemented by linear drives with ball-screw gears. The article proposes the solution of the extended inverse kinematics of the hexapod. The neural networks solution of the forward kinematics of hexapod is presented, i.e. the calculation of the position and orientation of the moving platform for given rotation angles of the ball-screw drives. The results of the synthesis of neural networks to achieve a given accuracy of solving the forward kinematics are presented. An estimate of the implementation of kinematic problems in the hexapod control system based on an ARM microprocessor is obtained.

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The article considers the control system of a parallel structure mechatronic device for space application such as a hexapod (Stewart platform). The solution of the inverse problem of kinematics is described and the necessity of solving the direct problem of kinematics by numerical methods is substantiated. During the research, it was revealed that the main source of positioning errors of the hexapod without the main feedback is its linear drives, which have systematic errors in the mechanical part of the linear transmission, gearbox, in the location of the motor windings; temperature errors due to changes in the dimensions of parts due to heating or cooling; errors caused by elastic deformations under load. To improve the static accuracy of the hexapod, a number of both design and software solutions are proposed: mechanical transmission preload, individual calibration of each drive, compensation for thermal expansion, etc. To improve the dynamic accuracy, it is proposed to use the method of controlling linear drives in the servo mode along with ensuring the trajectory of the platform with the limitation of the speed of its movement and derivatives of the speed. The use of these methods makes it possible to significantly improve the accuracy of the operation of the mechanisms of a parallel structure and, thereby, to approach the achievement of the limiting qualitative properties of onboard optical-electronic and information systems of spacecraft and stations.

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