Research on rapid batch test technology of small satellite attitude and orbit control system

The attitude and orbit control sub-system of small satellites is an important sub-system to ensure the stable operation of satellites in orbit, and its testing in the satellite factory development stage runs through the whole testing process. Most of the traditional attitude and orbit control sub-system tests require the cooperation of many people to complete the performance tests of various components and sensitive devices, which also leads to the complicated and time-consuming testing process of the sub-system. At present, the mass production of small satellites is developing rapidly. In order to meet the urgent needs of small satellite mass production, the traditional attitude control subsystem test equipment and methods can’t meet the requirements of satellite mass production mode. In order to meet the needs of small satellite mass development, this paper studies the rapid batch test technology of small satellite attitude and orbit control systems. A fast pipeline test system which can support the performance and dynamics simulation of various components of a multi-satellite attitude and orbit control subsystem is studied. Based on the architecture of real-time communication between the upper computer and lower computer, the system can realize the integration and rapid testing of component performance and dynamic simulation. A continuous dynamic simulation test of 2140 seconds was carried out for the cruise mode and attitude maneuver mode of a certain type of satellite in orbit. During the test, various components and sensors of the attitude and orbit control subsystem operate correctly and can support the stable operation of the required attitude in various modes of the satellite, which can verify the correctness of the interface and performance of the satellite attitude and orbit control subsystem. The research results greatly reduce the input of manpower and material resources, and greatly improve the test efficiency. It lays a foundation for the rapid batch test of the small satellite attitude control subsystem.


Introduction
Compared with the traditional small satellite development mode, the small satellite mass production mode has the characteristics of short cycle, heavy task, and large quantity.In the past two years, a series of commercial satellite companies led by the united states spacex company have successfully launched several satellites for networking, and have proposed the construction of the starlink constellation project, pigeon cluster satellite constellation, etc., and the annual output of small satellites can reach thousands of magnitude [1] .With the rapid development of policy support and technology, commercial satellite companies, research institutes, and universities represented by chang-guang satellite, yin-he aerospace, etc., have successfully launched the "jilin-1" Series, "si-xiang" Series, "ling-que constellation experimental satellite" Series and other satellites [2][3][4][5] .In order to adapt to the improvement of various IOP Publishing doi:10.1088/1742-6596/2764/1/012063 2 needs, the production mode of domestic small satellites is urgent and inevitable to achieve mass production mode.
At present, auto parts, mobile phones, household appliances, and other manufacturing lines have realized automated rapid manufacturing assembly and testing [6][7][8][9] .According to the characteristics of small satellite production, a production line assembly model based on pulsation has been proposed at home and abroad, and based on this model, in-depth research has been conducted [10][11][12][13][14][15][16] .The satellite attitude and orbit control subsystem is a key subsystem of the satellite, and its testing is a complicated link.A lot of ground simulation tests are needed in the development and launch of the small satellite attitude and orbit control system.At present, the ground simulation test equipment of the attitude and orbit control system of small satellites is usually a distributed system based on cabinet and general test instruments, which makes it difficult to meet the development needs of the rapid batch test of small satellites because of its low integration, complex use, and poor universality.
To solve the above problems, this paper proposes a rapid batch test system of attitude and orbit control system with a high degree of modular integration, which can support the assembly line test of attitude and orbit control system, effectively improve the test efficiency, shorten the test cycle, adapt to the mass production capacity of satellites, and support the rapid completion of multiple satellite tests.In this paper, based on the completion of the overall scheme of the dynamic simulation based test system, the operation principle of the system, the dynamic simulation based test method and the whole system operation process are mainly studied.

The overall scheme of the test system
The rapid batch test system for satellite attitude and orbit control system mainly consists of two parts: A control computer and a real-time computer.The control upper computer is a general purpose computer, mainly composed of a processing unit, display unit, instruction input unit, and test result output unit.The upper computer runs the human-computer interaction software of the simulation system.The real-time lower computer is composed of a controller, pxi terminal board, digital signal acquisition and output card, analog signal acquisition and output card, rs-422 communication card, can bus communication card, power supply card, interface box, etc.In addition to the chassis and interface box, all functional module boards of the real-time lower computer are integrated based on the pxi bus.The real-time computer controller runs the relevant dynamic simulation calculation software according to the satellite type.The upper computer and the lower computer are connected through ethernet, and the communication is completed based on tcp/ip protocol to realize the interaction of control instructions, data collection, and simulation data.Figure 1 shows the schematic diagram of the overall system scheme.The upper computer receives the test task to be completed through the instruction input unit and drives the lower computer to perform the dynamic simulation test through the processing unit.The lower machine is connected to the satellite to be tested through the interface box, and the expandable interface box has the interface switching ability, which can adapt to multiple types of satellites according to requirements, and support the completion of the attitude and orbit control system test of multi-satellite and multi-model.The lower computer provides real-time dynamic simulation information to the satellite and completes real-time interaction, realizes the dynamic closed-loop control of the satellite, and broadcasts the real-time status information of each component and sensor to the upper computer through UDP and displays it in real time.Figure 2 below shows the prototype of the system.

The process of system implementation
The test interface of the satellite attitude and orbit control system connects the satellite list cable to the real-time lower machine through the interface box.After the conversion through the interface box, the signals are connected to the corresponding module board respectively.The corresponding connection cable can be selected according to the actual test scenario and the type of attitude and orbit control system of the satellite under test.The real-time lower computer and the control upper computer are connected to the 220 v ac power supply, and the power supply sequence is according to the satellite attitude and orbit control subsystem.→ power on the lower part in real time → control the upper computer power→ the sequence of running control software on the upper computer is completed.After the software is started, the software test function is selected according to the specific test project and the corresponding test work is carried out.As shown in figure 3, during the test of the attitude and orbit control system, after system initialization and self-test, the initial simulation conditions and track information are set according to the tested object, and then the test is carried out.After the tests are done.The system power off sequence according to the control of the upper computer software → power off the real-time lower power module → the satellite attitude and orbit control system is powered off → the host computer generates the test report.According to the flight simulation test of the attitude and orbit control subsystem, the correctness of the functions and on-orbit running states of various sensitive devices and actuators can be verified.In order to adapt to the rapid batch test during the implementation of the whole process, when testing for multiple satellites at the same time, the problematic step process will be placed in the tank to be processed, and whether to continue the test will be judged according to the impact of the problem.If the current satellite is not suitable for continuing the test, it will be switched to another satellite through the interface box for testing, so as to ensure the smooth batch test.After the problem is solved, it will continue to be added to the list of tests in mass production mode.

Research on the principle of rapid test system based on closed loop control
In order to match the mass production time of the satellite, the system adopts the rapid test method based on dynamic simulation, which is mainly realized by the lower computer of the system.Figure 4 shows the schematic diagram for rapid testing based on dynamic simulation.Among them, the attitude and orbit control subsystem refers to the satellite-related equipment, which is mainly composed of three parts, such as the sensitive device such as the gyroscope, the actuator such as the momentum wheel and its controller.The real-time lower computer carries out data communication and various simulation signals interaction with the controller of the attitude and orbit control system through RS-422 and CAN interfaces.The output port of the digital signal acquisition and output card is connected to the digital sun sensor circuit on the satellite, the output port of the analog model acquisition and output card is connected to the analog sun circuit, and the output signal of the circuit power card is connected to the circuit of the gyro sensor.Based on the satellite's orbit information, the lower computer performs calculations to provide the required excitation signals for various sensors.After the device on the satellite receives the corresponding incentive signal, the controller of the attitude and orbit control subsystem starts to work, drives the actuator to start action, and feeds back the working information of the actuator to the lower computer.The acquisition end of the digital signal acquisition and output card and the acquisition end of the analog signal acquisition and output card are used to collect the information of the actuator of the attitude and orbit control system.The controller of the real-time lower computer can complete the data solution of the actuator, the dynamic simulation calculation, and the signal calculation of the sensor.Thus, the attitude and orbit control subsystem of the satellite is provided again, and the closed-loop control of the system can be realized finally.The test principle is to conduct a closed-loop simulation according to the status of the satellite in orbit, and the performance and function of various components can be verified by collecting and calculating various analog and digital quantities.

Method research based on dynamic simulation test
According to the operating principle of the system, the closed-loop control based on the dynamic simulation test method can verify whether the performance and function of sensors such as gyro, digital sun, and actuator such as momentum wheel are normal under the on-orbit operation state of the attitude and orbit control subsystem, and verify the correctness of internal and external electrical performance interfaces of the attitude and orbit control subsystem.
In order to support multi-type multi-satellite tests in mass production mode, dynamic link library functions are generated from different small satellite dynamic simulation models, and corresponding input and output interface functions are set up for simulation tests.Dynamic link library has good compatibility and versatility.It can be expanded according to actual needs.The designed dynamic link library input and output interface functions are shown in the following table 1 For the fast test process based on dynamic simulation, the dynamic link library needs to be loaded first.First, the DLL file name is set to "SatelliteDynamic.dll".The DLL file is imported into the realtime operating system of the lower computer through the lower computer software and stored in the specified folder for easy subsequent calls.After loading, dynamic simulation DLL is called by running dynamic simulation application software.The schematic diagram of the dynamic simulation test method of the single-model satellite attitude and orbit control system is shown in Figure 5

The whole system operation process research
In the mass production mode, the satellite ait test phase of each sub-system should be carried out according to the corresponding rhythm, and in most cases, multiple sub-systems should cooperate to complete.In order to make the attitude and orbit control subsystem match the mass production mode based on the dynamic simulation test method, this paper carried out the optimization of the automatic test process of the attitude and orbit control subsystem combined with the whole process test stage of the satellite factory.As shown in figure 6 below, the schematic diagram of a single-satellite one-time full process test based on dynamic simulation is formed.
The whole test process is mainly divided into test preparation, system power-on and state setting, dynamic simulation test, system recovery, result output, etc.Among them, the test preparation mainly completes the status confirmation of the rapid test system and the status setting of the satellite and attitude and orbit control system.The system power-on and status setting are mainly based on the equipment status of the attitude and orbit control system of the satellite to be tested to complete the upper and lower configuration of the rapid test system; The satellite-ground closed-loop simulation test is completed based on the dynamic simulation test.The test process can verify the basic performance of each sensitive device and actuator and whether the attitude and orbit control system meets the requirements of the satellite in orbit operation, and can achieve the purpose of the whole system verification of attitude and orbit control.System recovery and result output mainly cooperate with the completion of the power failure of the satellite attitude and orbit control system to ensure the safety of the on-board equipment at all times.At the same time, the rapid test system can output the basic performance of the attitude and orbit control components and whether the in-orbit flight status meets the requirements according to the dynamic simulation process.All test projects are time-consuming and require a lot of manpower and material resources.The optimized system-wide test process greatly saves time and improves efficiency.It can support the attitude and trajectory control subsystem to meet the mass production mode, and there will be no test waiting or suspension caused by the ground test system.

System application and verification
The rapid batch test system of the attitude and orbit control system of small satellites has been preliminarily applied to the batch test of a certain satellite.The dynamic simulation test can realize the verification of the function and performance verification of the attitude and orbit control system.The test system has good real-time performance and can realize the real-time simulation calculation cycle at the millisecond level.It can cooperate with the test of satellite attitude and orbit control system.Figure 7 below shows the scene when the system is used to test the attitude and orbit control subsystem of a certain production model satellite.In the process of dynamic simulation test, the variation range and working state of the three directions meet the requirements of the two working modes, and the operating state of the components and sensors of the attitude and trajectory control subsystem is correct.The system can support the satellite to complete the simulation of bias flight, attitude to the ground, and other scenarios, and the test method based on dynamic simulation can verify the correctness of various components and electrical performance interfaces at the system level.The test time is greatly reduced, and the test efficiency can meet the batch test requirements of the satellite.

Conclusion
Aiming at the urgent need for mass production of small satellites, this paper studies the rapid batch testing technology of the attitude and orbit control system of small satellites.A set of rapid test systems of satellite attitude and orbit control system based on dynamic simulation is designed, and related technologies such as system scheme, principle and method are studied in detail.Combined with practical application scenarios, a rapid process study of satellite attitude and orbit control system based on dynamic simulation is completed in batch mode.So that it can meet the satellite attitude and orbit control system mass, fast and efficient test.The rapid test system has been applied in the relevant satellites, which can support the satellite to quickly complete the component performance and flight simulation test of the attitude and orbit control system.At the same time, it can give the test results of various components under various on-orbit operation scenarios, and assist in the performance and function judgment.The system greatly reduces the time spent on attitude and trajectory control system testing, and the designed process based on dynamic simulation can support the smooth operation of mass production mode.It lays a foundation for the rapid test of satellite attitude and orbit control system under mass production mode.

Figure 1 .
Figure 1.Schematic diagram of the overall system scheme.

Figure 4 .
Figure 4. Schematic diagram of test principle based on dynamic simulation. below.

Figure 5 .
Figure 5. Method diagram based on dynamic simulation test.
power-on and status setting Dynamic simulation test System recovery and result output

Figure 6 .
Figure 6.The whole process test diagram based on the dynamic simulation test.In the traditional test mode, most of the distributed test flow is used, which mainly includes internal and external interface tests, component performance, and polarity tests, and system control ability tests.All test projects are time-consuming and require a lot of manpower and material resources.The optimized system-wide test process greatly saves time and improves efficiency.It can support the attitude and trajectory control subsystem to meet the mass production mode, and there will be no test waiting or suspension caused by the ground test system.

Figure 7 .
Figure 7. Schematic diagram of test scenario of satellite attitude and orbit control subsystem.The system conducted 2140 seconds of continuous dynamic simulation test for the rolling, pitch, and yaw Angle changes in the commonly used solar cruise mode and attitude maneuver mode of the satellite in orbit.The operation process is shown in Figure 8 below.The rolling Angle varies from -80.504° to 10.132°, the pitch Angle varies from -56.139° to 59.999°, and the yaw angle varies from -0.011° to 15.296°.

Figure 8 .
Figure 8.The working state curve of the satellite dynamics simulation test.In the process of dynamic simulation test, the variation range and working state of the three directions meet the requirements of the two working modes, and the operating state of the components and sensors of the attitude and trajectory control subsystem is correct.The system can support the satellite to complete the simulation of bias flight, attitude to the ground, and other scenarios, and the test method based on dynamic simulation can verify the correctness of various components and electrical performance interfaces at the system level.The test time is greatly reduced, and the test efficiency can meet the batch test requirements of the satellite.

Table 1 .
. dynamic link library function definition table.