Maslov, V. E.

Trapp, S. A.

Electronic archive of Tomsk Polytechnic University

XII Международная научно-практическая конференция студентов, аспирантов и молодых учѐных «Молодѐжь и современные информационные технологии» ___________________________________________________________________________ 291  DEVELOPMENT OF AN ALGORITHM FOR CONTROLLING ANTENNA DRIVE GEARS OF SPACECRAFT USING PROGRAMMABLE LOGIC CONTROLLER SIEMENS S7-1200  V. E Maslov, S. A.Trapp  Scientific supervisor: S.V. Leonov   Language supervisor S.V. Rybushkina National Research Tomsk Polytechnic University wado93@mail.ru; Gedeon@sibmail.com  Rocket and space industry of Russia is one of the most developed in the world. According to [1], Russia has occupied 11% of the world market of space ser-vices and the Russian government has plans to occupy almost a quarter in the nearest future. There are more than 60 organizations and companies providing prod-ucts for the space industry in Russia. One of the most productive is JSC Information Satellite Systems - Reshetnev Company that provides more than 70% of all Russian satellites.   Nowadays, results of scientific, research and engi-neering activity in the aerospace industry have found wide application in all spheres of modern live. That is why it is impossible to overprice the importance of space developments. The GLONASS navigation sys-tem, different systems of geolocation, communica-tion, spying etc. are just the most popular examples. Wide spreading occurrence of these technological solutions in everyday life additionally stimulates fur-ther researches in the aerospace sector, since their use on earth is impossible without having presence in space. It is necessary to constantly produce and modi-fy new spacecrafts, because modern satellites have a short longevity (4-6 years, on average). New modifi-cations should be mainly aimed at increasing longevi-ty of spacecrafts and reducing launching rates.  JSC Information Satellite Systems - Reshetnev Company provided TPU with several systems that ensure functioning of a spacecraft – an antenna rota-tion system (SRA) and solar drives (SD). Within the current study we have analyzed SRA. SRA consists of several structural units: a mechanical block (MB), and an electronic block (EB). EB contains a control unit drive (CUD) and equipment for calibration and testing (CTE). The MB of SRA contains two drive gears that al-low antennas to rotate perpendicularly in a given range with a predetermined precision and transmitting UHF signals. The MB is also designed to rotate a ro-tor of a rotating transformer (RT) to obtain infor-mation about the angle of a current antenna position. [2]  The layout and axes of the MB are shown in fig. 1.   Fig. 1. The layout and axes of MB of SRA  1 –MB boarding plane; 2- antenna boarding plane ; 3 –lower drive (Н); 4 –top drive (В); ϕН –  rotating angle of the H-drive; ϕB –rotating angle of the B-drive; OBZB –axis of rotation of the B-drive; OHZH –axis of rotation of the H-drive; Xn, Yn, Zn - coordinate system associated with the boarding plane of MB of SRA; Xa, Ya, Za - coordinate system associated with the antenna boarding plane. A control unit of drive gears (CUDG) is a pro-grammable logic device that performs the following  functions:   receiving control commands;  positioning the angle of the drive gear de-pending on a numerical driving signal value;  management of the drive gears while work-ing in a manual control mode with a constant speed;  generating information about the RT turn an-gle in a form of a sequential code;  switching circuits of heaters that are installed on power supply lines;   generating telemetric and technological sig-nals. [3] CTE (calibration and testing equipment) of SRA is an imitation of an onboard computer of the spacecraft. The main goal of the CTE is to test SRA in special conditions. CTE is a large-sized and heavy device and that is the reason why it was not provided by JSC XII Международная научно-практическая конференция студентов, аспирантов и молодых учѐных «Молодѐжь и современные информационные технологии» ___________________________________________________________________________ 292  Information Satellite Systems - Reshetnev Company. However, it is a mandatory element of the whole sys-tem, thus it was necessary to create a different CTE with the same signals and parameters at TPU.  Selection of a logic device that could be used as CTE for the antenna rotation system and analysis of technical documentation of the investigated system are the primary goals of our study.  It was decided to choose a programmable logic controller (PLC) Siemens s7-1200 as a base of CTE. This PLC allows controlling a wide variety of devices and is commonly used in automation because of its functionality. It is not as big as the old CTE, it has small size (110x100x75) and weight (475 g), which is a real advantage because the price of in-orbit delivery depends on these parameters and is usually very high. Because of a wide range of possible applications this PLC may also be used in education as a workbench for different labs in different subjects.  The software STEP 7 Basic allows programming the PLC and is a very comfortable environment to control and edit logic. It supports two different pro-gramming languages. They are LAD and FBD.  Ladder logic has evolved into a programming lan-guage that represents a program by a graphical dia-gram based on the circuit diagrams of relay log-ic hardware  The Function Block Diagram is a graphical lan-guage for programmable logic controller design, that can describe the function between input variables and output variables. A function is described as a set of elementary blocks. Input and output variables are connected to blocks by connection lines [4]. The interface of STEP 7 Bаsiс and an example of a simple LAD program are shown in fig. 2.   Fig.  2. The interface of STEP 7 basic  PLC Siemens S7-1200 was selected because of the following parameters:   Availability of the necessary amount of in-puts and outputs;  suitable power supply level (Normally the PLC works at 24 V but it is able to work in the range from 20.4 V to 28.8 V. SRA drive gears require volt-age in the range from 23 to 31 V.);  JSC Information Satellite Systems - Resh-etnev Company uses Siemens‘ controllers for the pur-poses of controlling different technical processes;  versatility;  durability and reliability;  small weight and size without sacrifice of functionality; It is also necessary to program the PLC so that it could perform a vast variety of commands such as to switch on/off manual gear control, heater sections, or CUD. The selected controller has many abilities. Its broad functionality, as well as versatility of the re-searched system as a whole allows using it as a work-bench for many labs in different subjects  to study electric drive systems (studying of electric and me-chanical characteristics of drive gears), microproces-sor engineering (programming with STEP 7) and mathematical simulation (using real systems as an object of study). The developed workbench would be very useful and students would get experience of working with a real system. At the moment, the technical document of each structural unit of SRA has been analyzed and func-tioning of the system has been studied. Hardware im-plementation for CTE was selected and the main algo-rithms of processing input-output relations received from the CUD have been developed.  Literature 1. Electronic newspaper: [Electronic source]. Access mode: http://www.newizv.ru/lenta/2006-07-06/49718-k-2015-godu-rossija-zajmet-15-mirovogo-rynka-kosmicheskih-uslug.html. Free. 2. JSC ISS. The mechanical block of the system of rotating antennas. 17Ф18.3470-000. Specification 17Ф18.3470 TY  – 1986 y. –33 p. 3. JSC ISS. CUDG of SRA Technical descrip-tion and operating instructions. 17Ф18.2253-01 ТО. – 1986 y. – 9p. 4. Siemens S7. programmable controller S7-1200. System management. – 2009 y. – p 52.   

Development of an algorithm for controlling antenna drive gears of spacecraft using programmable logic controller Siemens S7-1200

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