S. D. Zemlyakov

Some questions of control of the robotized in-orbit assembly of large space structures

Presented was an analytical review of the foreign and domestic scientific literature published over more than two decades on the dynamics and theory of motion control of large space structures and free-flying space robots meant for assisting the astronauts or replacing them at execution of diverse maintenance operations in open space. Although many results on the design of control systems for each of the aforementioned kinds of objects are very significant taken separately, nevertheless the most important problem of using the flying robots for in-orbit assembly of the large space structures remains still unsolved. Formulated was the concept of complex approach to the problem of robot-assisted in-orbit assembly of space structures which lies in combining the algorithms of all subsystems involved in the assembly of the objects with regard for the requirements on safe interaction of the participants, high resultant precision and reliability of operation, and minimal use of the consumable fuel.

Technical Controllability of the Free-flying Automated Space Module

Consideration was given to the free-flying automated space module, a facility intended for servicing the orbiting space station and its accompanying objects. The notion of technical controllability of the free-flyer was introduced. A theorem about the necessary and sufficient conditions for technical controllability was proved. Methods for establishing the domains of technical controllability in the space of the generalized coordinates of object motion were proposed. By means of an illustrative example, the results of applying the notion of technical controllability were demonstrated, the domains of the given degree of technical controllability were established, and the minimal necessary vector of constraints on control of the object was determined.

Operation algorithm of reference model-based adaptive system ensuring given dynamic precision of control of nonstationary dynamic object under uncertainty

A new adaptation algorithm was proposed for reference model-based systems operating independently of the intensity and spectral composition of the input actions. This fact enables one to make predictable the dynamic precision of the reference model-based adaptive system which, by the authors’ opinion, is the stumbling block to wide practicalization of the systems of the class under consideration.

Computer-aided on-line development and derivation of the motion equation of space module

Consideration was given to derivation of the motion equations of a space robotic module with a mathematical model having many degrees of freedom whose number can vary in the course of operation. This problem was solved in a computing environment such as the Maple program package. It was anticipated that the on-line mathematical model would be used to establish a rational in a sense motion control law of such a complicated object. For this purpose the paper solved some problems of decomposition of the resulting mathematical model. The results of computer-aided derivation of the motion equations of several particular schemes of the of the space robotic module were presented to illustrate constructiveness of the proposed mathematical support of problem solution.

On Technical Controllability and Decomposition of the Lagrangian Systems with Bounded Controls

Consideration was given to control of the plant obeying the second-order Lagrange equations. Stringent requirements on the dynamic characteristics of motion under bounded control actions were placed on the control system of this plant. The notions of technical controllability of the closed-loop system and autonomous technical controllability of the plant were defined. The conditions for autonomous technical controllability of the plant were established and used to prove that the mathematical model of plant motion can be decomposed into individual subsystems. The decomposable mathematical model underlies a control algorithm providing technical controllability of the closed-loop system in terms of the given set of technical requirements.

Application of the Principle of Design of Adaptive Systems with a Reference Model to Problems of Monitoring of a Current State of Transmission Shafts

A possibility of monitoring a current state of transmission shafts on the basis of an adaptive system with a reference model is considered. Using a gas-turbine engine as an example, a problem is solved for the estimation of a torsion angle of the shaft that transmits the torque of a free turbine through the reduction gear to the propeller in the condition of a finite value of the torsion stiffness of the shaft. The torsion angle specifies the current state of the shaft and can be used for the advanced disengagement of the engine in the event of the breakup of the transmission. It is shown that the suggested adaptive system of estimating the torsion angle of the shaft ensures a high dynamic accuracy in the stationary and nonstationary modes of operation of the engine. The mathematical modeling confirmed the serviceability of the system under conditions that are close to actual ones, in particular, under the action of random noise of the measurement.

Some Results of the Theory of Nonsearching Adaptive Systems and Their Application

Some problems of flight vehicle control that date back to the 1950s and gave rise to the theory of adaptive control and, in the 1960s and 1970s, self-adjusting automatic pilots were discussed.

Computer-aided solution of some problems relating to control of the complicated mechanical systems

Consideration was given to control of a complex object whose motion obeys a multivariable nonlinear nonstationary mathematical model. Rigid constraints were imposed on the object’s dynamic precision. The paper considered computer-aided generation of the current equations of object motion with regard for the actuators which differ from subsystem to subsystem. The object is controlled adaptively with regard for the computer-based realization. The algorithms of control system operation that maintain the guaranteed precision of object motion were constructed. Conditions for problem solvability were formulated. The freeflying space robot was discussed by way of example.

Control of Angular Motion of the Robotic Space Module Transporting a Flexible Load

Consideration was given to designing the optimal control of a free-flying robotic space module equipped with relay actuators which carries a bulky flexible load. The procedure of designing a spatial modal-physical model of the robotic space module with a flexible load was described. For this construction, numerical analysis of the dynamic “portrait” which accompanies the model enables one to establish the profile of its elastic oscillations which has the form of a multiextremal function in the space of possible values of the coordinate of the point where the load is gripped by the manipulator. The global extremum (minimum) of this dependence, which was accepted as the goal function, was used as a criterion for designing the algorithm optimizing the gripper position on the load axis upon stabilizing the angular motion of the module. The calculated extremum is used in the loop of adaptive adjustment of the gripper parameter, which prevents resonance swinging of the flexible load transported to the place of installation.

A design algorithm for self-improving nonstationary dynamic systems using adaptive coordinate-parametric control

The article considers the class of self-improving dynamic systems that, functioning under conditions of nonstationary with failures and element aging, are capable of assessing the external operating conditions and the degree of functional readiness, while at the same time raising the degree of readiness to the maximum attainable on the current time interval. Concurrently, the system estimates the reachability of the goals that can be accomplished at the current instant and activates the control strategy to achieve the highest-priority goal among the reachable goals. The principle of adaptive coordinate-parametric control is applied to design self-improving dynamic systems.