docking with sufficient accuracy, it is necessary to test the drives with control signals with frequencies of up to 10-12 Hz without substantial dynamic distortions. Evaluations showed that at a control signal frequency of 10 Hz distortions of amplitude for an open drive circuit should not exceed 2 dB, and the phase delay should not be greater than 70*. The maximum force developed by the drive is 125 kN, and the velocity of the rod is up to 0.5 m/s. The total power of the six drives is about 150 kW. To provide these characteristics it is necessary to optimally construct the electrical and hydraulic control block and efficiently construct the executive cylinder. It is also necessary to have sufficient rigidity. The characteristics of the closed circuit of the drive are greatly affected by the frequency characteristics of the immobile heavy-duty base of the test unit. A heavy-duty scheme and base construction is needed with a fundamental frequency of elastic oscillations of no less than 30-40 Hz. A complex problem is the solution of the equations of motion of the modeled spacecraft in real time with a sufficient accuracy, considering the temporal delay, which affects the stability and quality of the operation of the closed circuit. Due to the large power of the test unit drives, to insure the preservation of the equipment and safety of the personnel, an emergency shut-down system is needed, and a system to stop the drives, which are adjusted for activation when the parameters of operation deviate from the calculated values. This system, which consists of sensors which measure the parameters of docking and the functioning of the test unit, as well as the automated processing of signals and the executive values in the drive control blocks, should provide a high speed (a delay of no greater than 0.2 s). More than one hundred parameters are recorded by the automatic measurement system. Control of the complex test unit is done from several control panels which insure the work of the drives, computers, recording equipment, system of thermal regulation, docking assemblies, and television and movie cameras. The work of the operators of all the control panels is coordinated by the testing director. Tuning, verification, and coordinated control of all systems of the test unit is done using a digital computer with an automatic recording device for initial data and basic parameters of tuning, including the inertial-mass characteristics of the
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