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Screw rams position polar mount antenna precisely

Enabling the movement of heavy objects with complete precision is one of the core areas of expertise of Pfaff-Silberblau's Actuator Division. In a recent project for a well-known scientific research institute, Pfaff-Silberblau's engineers have once again demonstrated their proficiency in developing tailored designs. Using electromechanical screw rams from the company's own ALS 'building-block' modular system, they have developed polar-mount positioning capabilities for the precise adjustment of a satellite receiver antenna that weighs in at 8 tonnes and has a diameter of about 5 metres. The antenna, which tracks geo-polar satellites travelling in an elliptical orbit around the earth about 37,000km above the equator, requires ultra-precise positioning capabilities that enable it to perform both tilting and swivel movements. Pfaff-Silberblau achieved this combination of elevation and azimuth movements through a polar-mount configuration based on three completely encapsulated ALSR 100 electromechanical screw rams with highly robust axial and radial bearings. One electromechanical screw ram ensures the highly accurate positioning of the vertical angle of elevation, while the second system, which consists of two ALSR 100s, sets the horizontal azimuth angle. Integral reinforced journals enable the antenna to swivel to the prescribed angle position in both the elevation and azimuth directions. Despite the heavy load, the equipment travels a maximum stroke of 450mm at a speed of around 130 millimetres per minute. The travel limits are monitored via two built-on inductive proximity switches. The electromechanical screw rams are driven via a motor reduction unit with a built-in absolute value transmitter, and are actuated by a frequency converter. Pfaff-Silberblau's drive concept includes a comparison of the target data with the actual data, the motor's rotational speed, and a master/slave synchronisation of the two individual actuators for the azimuth movements. In this way, the drive motor's rotational speed can be measured via the built-in sensor, and the resulting value can then be fed back to the speed controlling device, which minimises load-dependent deviation. Simultaneously, the master actuator supplies the encoder signals to the slave actuator as the target value. The slave then compares this data with the signals from its own actuator, and readjusts as necessary.

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