The work of the longitudinal shock absorber, as shown in section 5.3, can be examined independently, since its analysis studies a central impact. The energy capacity of the longitudinal shock absorber, defined by the equivalent mass of the central impact is usually largest. To obtain the minimum course in the second stage of deformation, the force on central impact should be increased to values limited by the durability of the docking mechanism. For electromechanical docking mechanisms the applied mass of the accelerated parts is relatively large (for example, for the Soyuz docking device, for the Soyuz-Salyut device), thus the direct impact should be studied with (5.17). For the longitudinal shock absorber of the Soyuz-Salyut docking mechanism the maximum force is the sum of the resistance created by the friction brake, the “viscous” component and the inertial force with components, that is, where is the acceptable force. The inertial component may be determined by solving an equation like (5.15). For the same two-stage shock absorber, the basic inertial elements (nut of the ball-screw converter, rotors of the electromagnetic brake) are accelerated at the beginning of the process. The applied mass of moving parts of the friction brake is small and is, for the Soyuz-Salyut docking mechanism, 0.7 kg. Figure 5.15 shows the dependences of force on time as determined from (5.17). It is obvious that the dynamic component in the second part of the work of the friction brake is insignificant. The force on “recoil” for the two-stage shock absorber with a friction brake does not exceed the maximum force on the forward course without using additional energy absorbing elements. When a spring shock absorber is used in the Soyuz docking mechanism retraction of the screw is provided, as well as an additional spring for shock absorption of the recoil (see Figure 5.9). It should be noted that when a combined shock absorption-drive system is used with a friction self-regulating brake, the longitudinal shock absorber may have a substantially larger energy capacity. The energy of the central impact may be
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