Simulation of factors for testing algorithms of object angular motion control on laboratory bench

Зимаков Алексей Алексеевич – аспирант Сибирского государственного университета науки и технологий имени академика М.Ф. Решетнева.

Аннотация: Анализ влияния источников возмущений неотъемлемая часть построения системы управления космическим аппаратом, так как влияют не только на процессы ориентации и стабилизации в пространстве, но и служат источниками ошибок. Для того что бы имитировать большинство физических процессов в лабораторных условиях, а также визуализировать процессы управления объектом, необходимо создавать специальные условия, и иметь возможность фиксировать изменения которые происходят с объектом и уметь их пересчитывать в нужные для работы алгоритмов величины.

Abstract: Analysis of the influence of sources of disturbances is an integral part of building a control system for a spacecraft, since they affect not only the processes of orientation and stabilization in space, but also serve as sources of errors. In order to simulate most of the physical processes in laboratory conditions, as well as to visualize the control processes of the object, it is necessary to create special conditions, and be able to record the changes that occur with the object and be able to recalculate them into the values necessary for the algorithms to work.

Ключевые слова: возмущающий момент, модель движения, факторы космического пространства, стенд, макет.

Keywords: disturbing moment, motion model, factors of outer space, bench, layout.

The complexity of the problem of calculating and modeling the process of rotational motion around the center of mass of spacecraft in near-earth space is due to many factors, such as the arbitrariness of the initial data, the distribution of masses and the arbitrariness of shapes.

In the process of functioning in orbit, the spacecraft is subject to the influence of gravitational moments, aerodynamic and electromagnetic moments, dissipative effects associated with the friction of the spacecraft shell against the atmosphere and the interaction of metallic elements with the Earth's magnetic field, forces of light pressure on the spacecraft.

Analysis of the influence of sources of disturbances is an integral part of building a control system for a spacecraft, since they affect not only the processes of orientation and stabilization in space, but also serve as sources of errors. One of these sources is the deformation of structural elements when heated from sunlight. In addition to deformations caused by temperature factors, there are elastic deformations under the influence of external moments acting on the apparatus.

In the process of synthesizing control algorithms and calculating the dynamic processes of orientation and stabilization of the spacecraft, the disturbing moments and sources of errors are modeled using scientifically based approaches, a capacious theoretical and empirical knowledge base from various branches of physics.

In order to simulate physical processes in laboratory conditions, as well as to visualize the control processes of an object, it is necessary to create special conditions, and be able to record the changes that occur with the object and be able to recalculate them into the values necessary for the operation of algorithms. For example, let us analyze the deformations caused by temperature effects, theoretically this is a type of mechanical stress that occurs in any medium due to a change in temperature or an uneven distribution. In the calculations, the source causing this stress does not really matter; due to this assumption, deformations caused by solar radiation in orbit can be simulated in laboratory conditions by any directional heat source. The magnitude and nature of temperature deformations can be recorded and interpreted by means of a strain gauge. Not all disturbing moments and sources of errors can be imitated and integrated into the processes of motion control around the center of mass, for example, moments caused by gravitational and aerodynamic forces cannot be simulated within the framework of this stand, in view of the design features of the stand itself.

The bench is a gimbal with a spacecraft model placed in it (Fig. 1). The spacecraft model has a set of sensors for testing control algorithms, and servos for turning the solar panels.

Figure 1. Bench scheme.

The gimbal enables the spacecraft model attached to it to rotate in three planes. The gimbal mechanism consists of arched-shaped internal and an external guides 2 and 1, a step motor located at the center of the gimbal external guide to provide for rotation around the Y axis, a step motor attached at the end of the external guide to provide for the internal frame rotation around the Z axis, and a step motor at the center of the internal guide to provide for the spacecraft model 3 rotation around the X axis. [2]

Elastic deformations can be created by means of a vibration motor, which is essentially a motor with an eccentric attached to the shaft, the vibration frequency of which can be changed by adjusting the weight of the load attached to the shaft, the distance from the start of the shaft to the load, and the speed of the motor. It is best to place the vibration motor inside the spacecraft model. The value of elastic deformations can be recorded and interpreted by means of a vibration sensor.

Thus, the need to create special laboratory conditions for modeling certain external disturbances in order to visualize the object control processes should be guided by the tasks of the research being carried out, the assumptions made, and the list of sources of disturbances and errors necessary for the control mode.

References

1. Белецкий В. В. Движение искусственного спутника относительно центра масс. Москва: Наука, 1965. 416 с.
2. Зимакова И.А. Laboratory bench for testing algorithms of object angular motion control // Сolloquium-journal – 2019г. – № 37. — С. 49.
3. Landis Markley, John L. Crassidis. Fundamentals of Spacecraft Attitude Determination and Control // Springer, New York, 2014. 486 с.