mechanisms are breakdown and jamming, and the intermediate state, deformation and binding (partial jamming). These are the most frequently encountered (or reduced to them) types of failures in docking devices. Tn immobile elements only breakdown and deformation are possible. It is expedient to analyze possible failures of all basic elements of the docking device and the resultant consequences in the form, for example, of Table 2.5. It may be a summary of elements for which there is no redundancy, and whose failures lead to a failure to complete one of the main functions with a criticality category of I or IT, with the indication of possible defects leading to this. It is desirable to minimize this list in development. One of the rules which frequently governs the planning of electrical control circuits is the desire to insure the absence of category IT failures due to the failure of any one element, and to insure the absence of category I failures due to the failure of any two elements. To implement this rule in executing the second main function, that is, preservation of the docked state, blocking is introduced into the control channels of the main and back-up equipment to open the locks of the docking frame, and the elements in the electrical circuits are backed up. One effective means of redundancy is so-called functional redundancy, that is, the use of mechanisms which are capable of carrying out several operations (see section 2.7.5). Supplementing, simplifying and increasing the efficiency of analysis makes it possible to compare structural schemes of the development of failures (Figure 2.1). These schemes, called failure trees [38], should be compiled for the execution of all three basic functions in varying degrees of detail, for main and back-up types of work, considering the different types of element failures. These structural schemes, in the later stages of development after statistical data is obtained on the reliability of individual elements, facilitates the calculation of probability characteristics of the reliability of the docking device. These diagrams can be used to analyze how a change in the characteristics of construction or the external conditions of operation can affect the reliability of the docking device. The result of this analysis is an evaluation of the criticality of the effect of these factors on various elements in various stages of preparation for
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