Controlling solar-cell drives in the Russian segment of the International Space Center by means of a magnetic-clutch torque sensor

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Controlling solar-cell drives in the Russian segment of the International Space Center by means of a magnetic-clutch torque sensor

Belenkii, A.D.

The dynamics of the drives in the solar-cell orientation system within the scientific and power platform of the International Space Station (ISS) is investigated. A method of drive control based on the torque sensor of the limiting magnetic clutch of the drive is proposed. The sensor must measure the magnetic-clutch torque over the whole range of torsional angles from 0 degree to 360 degree. Optimizing the drive mass entails adjusting the magnetic clutch within the kinematic chain of the gear system, which creates specific working conditions for the torque sensor. Operation conditions in combination with the requirements on the reliability and working life (no less than 15 years), entails the use of the Hall Effect in the torque sensor. The sensor consists of two identical modules, each with a rotor and stator. The stators are motionless relative to the gear housing, while the rotors are connected to the driving and driven shafts of the magnetic clutch. The stator consists of an annular magnetic system. Two Hall sensors separated by an angle of 45 degree are attached to its inner surface. The rotor forms a quadrupole magnetic system; permanent magnets are attached to its poles. The direction of magnetization of the magnets alternates. The number of poles is equal to that for the magnetic clutch. The parameters are selected so that, when the rotor turns relative to the stator, the electromagnetic force (emf) generated by the Hall sensors is proportional, respectively, to the sine and cosine of twice the angle of rotation. The angle of rotation is measured by means of a raster optical angular sensor with a scale division of 7.5 min, which controls the recording of the Hall-emf signal from the analog-digital converter in the computer memory. Variation of the amplification factor with respect to the sensor signal shows that there is an optimal value at which the drift of the solar cell is minimal. The optimum corresponds to drive operation at the limit of clutch slip. The amplification factor of the sensor feedback must be different when the system is tracking the sun and during dynamic operations at the ISS such as docking and installation work.