Power electromechanical drive based on planetary roller-screw gear of improved accuracy

Аuthors

Nosov A. S.

Center for exploitation of space ground-based infrastructure - Design Bureau «Motor», 7, Sergey Makeev str., Moscow, 123100, Russia

e-mail: alekstambov@mail.ru

Abstract

The author chose power electromechanical actuator drives based on planetary roller-screw gear (PRSG) of improved accuracy and reliability of operation of the special equipment for integration installation of large-sized with and large mass products with a rocket carrier of a super-heavy class as the object of study.

The technique includes the preparation of the initial data and the basic requirements to the actuator, an electromechanical drive circuit design. It also considers selection of materials and heat treatment of the main parts of the mechanism, the selection of lubricant, the design of the actuator, a preliminary calculation of the transmission efficiency, as well as power and kinematic analysis of the transmission. It allows calculate power losses in the mechanism, and adjust the calculation (if necessary), creation of a model to determine the main characteristics, checking compliance of transmission with specifications, comparison of the options and selection of the optimal one, the creation of the final model, test strength calculations, preparation of design and technical documentation.

As long as power electromechanical drive is a vital unit with high requirements to accuracy of manufacturing of certain elements, the solid-state modeling with adjustment at each stage is necessary. The solution of such problems is made difficult without the use of through-design CAD / CAM / CAE systems.

To ensure the required speed and accuracy of the output displacement of the electromechanical actuator we use the actuator with high reduction and efficiency. This is planetary roller-screw with a number of advantages over conventional transmissions:

• increased load capacity due to power transfer by several streams with load distribution between rollers and increase of contact lines in helical links total length;

• allows improve reproduction accuracy of a given law of motion of the mechanizm;

• reduces weight and size of the mechanism and provides a high overall efficiency due to the large reduction of the stage;

• performs frame and supports load reduction, due to the distribution of forces in the planetary gear;

• allows complete elimination of the gap in the transmission;

• provides high smoothness of motion, allowing high accuracy to perform a given output displacement law depending on the input signal;

• provides high smoothness of movement when moving at micro speed;

• exhibits small friction losses and high durability;

• operation capability in a wide range of temperatures and in vacuum;

• operates at high speeds and acceleration;

• has no impact on the environment;

• compactness.

The basic elements of the transmission are as follows: screw nut, threaded rollers, toothed crowns, separator, locking rings. Both screw and nut can be the key element in this transmission. Screws and nuts have a thread of triangular shape with an apex angle of 90(. Rollers have a special thread which profile in axial section has the shape of convex arcs of a certain radius, due to which a point contact is provided in conjunction with the roller screw and nut. The design of such transmission allows for different angles of helix of screws and nuts.

Justification and development of scientific and methodological apparatus, and creation with its application of electromechanical drive with planetary roller-screw transmission for space nosecone tilters of a space-rocket carrier of super-heavy class allows improving the process of preparing a space-rocket carrier for launch. Improving the process of space-rocket carrier preparation for launch means increasing accuracy in reproduction of the ground tests program with regard to the laws of nosecone motion and allows reduce the possibility of emergency situations due to incorrect operation of the installed equipment and machinery of a space nosecone at the boost phase.

Keywords:

roller-screw transmission, power electromechanical actuator, comparative analysis of electromechanical drive, reliability

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