Attitude Determination And Control Subsystem Research Articles

Characterization and verification of the optimal feedback gain of a satellite magnetorquer-based attitude control system

In spacecraft mission planning and operation, the attitude determination and control subsystem (ADCS) of a satellite provides information about the orientation of the satellite in the inertial reference frame. Furthermore, this subsystem produces the control actions required to adjust the orientation of the satellite, especially in the low-Earth orbit (LEO) regime. This paper focuses on the satellite’s three-axis attitude control problem within the context of active and passive control, which includes detumbling control, pointing control, magnetic control, and attitude stabilization after solar panel wing deployment using magnetorquers as the primary actuators. The objective is to stabilize and reduce the angular rate while orienting the satellite to the desired attitude. The proposed satellite attitude control system (ACS) strategies are designed, developed, characterized, and verified. These strategies encompass the B-dot control algorithm for detumbling control along with pointing control and attitude stabilization after solar panel wing deployment. hardware-in-the-loop simulation (HiLs) tests are conducted to assess the performance of the satellite magnetorquer-based ACS in the presence of noise. These tests involve a relative Earth’s magnetic field (EMF) generator in conjunction with SGP-4-based satellite orbital propagator high-level control software. Additionally, cascade proportional-integral-derivative (PID) and state-dependent Riccati equation (SDRE) controllers are implemented to generate sufficient torque using three-axis magnetorquers on a frictionless air-bearing platform. The platform is balanced to closely simulate the dynamic motion of a spacecraft in space. The testing includes a single initial condition and three inertia conditions for stabilization after solar panel wing deployment. Finally, the effectiveness of the cosimulation as a primary experiment through an integrated HiLs process is validated. This comprehensive approach confirms the control system’s performance and its ability to meet mission requirements.

Use of thermal data to estimate satellite rotation rate in the UPMSat-2

Attitude determination is a fundamental task of the Attitude Determination and Control Subsystem (ADCS). It involves determining the spacecraft’s orientation with respect to a reference system and calculating its angular velocity, which is essential for understanding where the payload is pointing and the spacecraft’s stability. The determination of the attitude is obtained using sensors such as Sun sensors, Nadir sensors, or Star trackers. Regarding the spacecraft angular velocity, gyroscopes or MEMs can be used to measure the angular velocity of the satellite, but in their absence the velocity can be derived from the attitude data of the other sensors. However, this method requires a sampling rate to be twice the frequency of the movement, otherwise the angular velocity cannot be calculated with traditional methods. To address this issue, this study proposes a thermal analysis of the external temperatures of a rotating satellite to obtain its rotation rate. This method is especially useful for satellites with low or limited data sample rates. The proposed methodology is used in the UPMSat-2 case to demonstrate the functionality of its experimental ADCS.

Spacecraft fault detection and identification techniques using artificial intelligence

The complexity of spacecraft systems and their missions is increasing, requiring higher levels of performance and innovative solutions. It is essential to have onboard autonomy with minimal faults to ensure reliability, availability, and safety. Fault Detection and Identification (FDI) is critical in identifying spacecraft faults before they cause major failures. However, FDI design and application are challenging due to the space environment and the reliance on system information. To improve accuracy, speed, and noise robustness, modern FDI methods based on Artificial Intelligence (AI) techniques have been developed. This paper investigates the latest FDI techniques in the spacecraft attitude determination and control subsystem (ADCS) and electrical power subsystem (EPS). The article discusses various FDI methodologies and frameworks, highlighting their advantages, drawbacks, and the significance of AI implementation. Additionally, the paper presents a thorough analysis and comparison of the different methods.

Modeling and analysis for reaction control thruster used for station-keeping maneuvers of a GEO satellite

This paper introduces a theoretical description, force, and torque analysis of a Reaction Control Thruster (RCT) used as an actuator in Attitude Determination and Control Subsystem (ADCS). Mathematical formalization, realization, and implementation are offered to implement the RCT model using Matlab-Simulink. Furthermore, this paper proposes an accurate RCT Simulink model to control the orientation and stabilizes the Geostationary Earth Orbit (GEO) satellite within its orbit. Finally, a comparative analysis is carried out with an existing satellite platform (Eurostar-3000) based on the Root Mean Square Error (RMSE) for the delta velocity (delta-𝒱) parameter. The outcomes of the model simulation validated the effectiveness of the proposed approach.

Attitude estimation in a modular plug-and-play satellite

Spacecraft modularity is a powerful design methodology for shortening satellite development cycles and reducing costs. The exploitation of standardized and reusable modules, universal interfaces and protocols, generic design, and a set of defined conventions, allows for rapidly integrating a flexible and cost-effective platform with ease of component modifications. Anyhow, the implementation of modularity poses several issues at any level of mission and spacecraft design, including subsystem design. This paper deals with the Attitude Determination and Control Subsystem (ADCS), with a particular accent on making the estimation software independent of any specific requirements dictated by the application in question. In this respect, a generic and reusable Murrell's Multiplicative Extended Kalman Filter (MMEKF) that can operate on different satellites, with diverse estimation requirements, working with changeable integrated ADCS boxes and sensor suites, but without changes either in the equations or in the interface with the rest of the system, has been proposed. The algorithm has been designed to maximize flexibility and ease of applicability to different missions without a priori-knowledge of the actual configuration. The execution of the algorithm is based on a plug-and-play logic in which middleware software enables the automatic discovery of the available sensors and the transmission of required data to the estimation algorithms. An adaptable and modular 3D simulator has been built to test and validate the performance of the generic MMEKF over multiple test cases with assigned configurations. The results of the simulations confirm the capability of the algorithm to meet estimation requirements for each simulated case, without ad-hoc, case-by-case, optimization, or customization.

The UPMQube: An Academic/Educational PocketQube Proposal for the EU2Space Challenge

In the present paper, the UPMQube PocketQube proposal for the EU2Space challenge is described. This proposal has been developed by a group of master’s degree students led by Ph.D. students and professors from the Instituto Universitario de Microgravedad “Ignacio Da Riva” (IDR/UPM) at Universidad Politécnica de Madrid (UPM). PocketQube is a recent new picosatellite concept, which is currently under development. Its reduced size and mass require a significant effort to reduce the characteristic size of the elementary subsystems. One of the subsystems that offers the greatest capacity for improvement is the Attitude Determination and Control Subsystem (ADCS), since most PocketQubes do not usually have one due to lack of space. The most relevant technical aspect of this proposal is the development of a new ADCS which fits the high restrictive size and mass requirements, and it is based on Commercial Off-The-Shelf (COTS) components. This ADCS is composed by: (i) a purely Autonomous Magnetic Controller (AMC) based on magnetorquers and magnetometers on board the spacecraft (S/C platform; (ii) an Attitude Determination System (ADS) based on solar sensors and thermal sensors on board the S/C and an On Ground Attitude Determination Algorithm (for post processing the sensors flight data. The work carried out by Master s degree students is integrated within the academic program of the UPM’s Master in Space Systems as a Case of Study. It also provides an excellent training program for the Ph.D. Assistant Professors included in the proposals Team. The tasks assignments and responsibilities of all members of the Team are fully described in the paper. Additionally, it should be underlined that this proposal is quite well balanced in terms of gender, as 40% of the Team (including the Principal Investigator) are women. This figure is higher than the mean percentage of women present in STEAM Sciences, Technology, Engineering, and Mathematics careers (29% of the workforce, 19% of company board members, 3% industry CEOs). Keywords: UPMQube, PocketQube, MUSE, magnetic ADCS, space engineering challenge

Automatic Balancing for Satellite Simulators with Mixed Mechanical and Magnetic Actuation

Dynamic spacecraft simulators are becoming a widespread tool to enable effective on-ground verification of the attitude determination and control subsystem (ADCS). In such facilities, the on-orbit rotational dynamics shall be simulated, thereby requiring minimization of the external torques acting on the satellite mock-up. Gravity torque is often the largest among the disturbances, and an automatic procedure for balancing is usually foreseen in such facilities as it is significantly faster and more accurate than manual methods. In this note, we present an automatic balancing technique which combines mechanical and magnetic actuation by the joint use of sliding masses and magnetorquers. A feedback control is employed for in-plane balancing in which the proportional and integral actions are provided by moving the masses, while the derivative action is provided by the magnetorquers. Compared to an earlier implementation by the authors relying on shifting masses only, the novel approach is shown to reduce the in-plane unbalance by an additional 45% on average.

A Spacecraft Attitude Determination and Control Algorithm for Solar Arrays Pointing Leveraging Sun Angle and Angular Rates Measurements

The capability to orient the solar arrays of a spacecraft toward the Sun is an ultimate asset for any attitude determination and control subsystem (ADCS). This ability should be maintained in any operative circumstance, either nominal or off-nominal, to avoid the loss of the entire space-borne system. The safe mode implementation should guarantee a positive power generation from the solar arrays, regardless of the health status of the satellite platform. This paper presents a solar array pointing algorithm, to be executed on-board, with a minimal set of sensors and actuators. In fact, the sensors are limited to the solar arrays, exploiting the current/voltage sensing capacity of the electrical power subsystem to measure the Sun angle with respect to the arrays normal, and to the angular rates sensors. The actuators are required to provide a torque only along two axes and, thus, a reduced actuation capacity is still manageable by the proposed algorithm. The paper describes the algorithm, both in the Sun direction determination and in the Sun pointing control capacity. The achieved performance is outlined, considering either an ideal system or a realistic one, being the latter affected by sensors and actuators limitations. The actuation by means of momentum exchange devices or magnetic torquers is discussed, with the purpose to prove the wide applicability range of the presented algorithm, which is capable to guarantee solar array orientation with a minimal hardware set.

On the UPMSat-2 Attitude Determination and Control Subsystem’s magnetometers integration

In the present work, a method for magnetometer calibration through least squares fitting is presented. This method has been applied over the magnetometer’s data set obtained during the integration tests of the Attitude Determination and Control Subsystem (ADCS) of UPMSat-2. The UPMSat-2 mission is a 50-kg satellite designed and manufactured by the Technical University of Madrid (Universidad Politécnica de Madrid), and finally launched in September 2020. The satellite has three fluxgate magnetometers (one of them experimental) whose calibration is critical to obtain correct measurements to be used by the ADCS. Among several mathematical methods suitable to obtain the calibration parameters, an ordinary least squares fitting algorithm is selected as a first step of the calibration process. The surface estimated is an ellipsoid, surface represented by the magnetometer’s measures of the Earth magnetic field in a point of the space. The calibration elements of the magnetometers are related to the coefficients of the estimated ellipsoid.

Design and implementation of a star-tracker for LEO satellite

An important task of the attitude determination and control subsystem (ADCS) is the determination of attitude of the satellite in reference to the Earth or any other planetary and correct any deviation from the expected attitude. In order to determine the attitude of the satellite, sensors are needed to sense the orientation of the satellite. The star-tracker is able to determine the attitude from the view field of the star set without any prior knowledge of sensor information. In this paper, the design, simulation and implementation of a star-tracker is presented for LEO satellites. For capturing image data, the MT9P031 CMOS image sensor from Aptina Imaging was used. The star tracker uses a Texas Instrument OMAP3530 using an ARM Cortex A8. The processor supports powerful graphic interfaces resulting in reduction of the size and consumption power of the star-tracker. For storage and processing, the star tracker used NAND flash memory. The communication interface to the satellite is done through CAN Bus. One of the key features of this sensor is processing various algorithms for image processing, positioning, and tracking according to mission requirements. Quaternion estimator (QUEST) algorithm was utilized for positioning. The tracking algorithm utilizes information from the previous frame of the star-tracking. This algorithm is a high-speed, low cost, and low memory implementation. In the field tests, the identification success rate of this system was 96.81 %.

Development of a hardware-in-loop attitude control simulator for a CubeSat satellite

Attitude control is an important part in satellite on-orbit operation. It greatly affects the performance of satellites. Testing of an attitude determination and control subsystem (ADCS) is very challenging since it might require attitude dynamics and space environment in the orbit. This paper develops a low-cost hardware-in-loop (HIL) simulator for testing an ADCS of a CubeSat satellite. The simulator consists of a numerical simulation part, a hardware part, and a HIL interface hardware unit. The numerical simulation part includes orbital dynamics, attitude dynamics and Earth’s magnetic field. The hardware part is the real ADCS board of the satellite. The simulation part outputs satellite’s angular velocity and geomagnetic field information to the HIL interface hardware. Then, based on this information, the HIL interface hardware generates I2C signals mimicking the signals of the on-board rate-gyros and magnetometers and consequently outputs the signals to the ADCS board. The ADCS board reads the rate-gyro and magnetometer signals, calculates control signals, and drives the attitude actuators which are three magnetic torquers (MTQs). The responses of the MTQs sensed by a separated magnetometer are feedback to the numerical simulation part completing the HIL simulation loop. Experimental studies are conducted to demonstrate the feasibility and effectiveness of the simulator.

Efficient anomaly classification for spacecraft reaction wheels

Attitude Determination and Control Subsystem (ADCS) in spacecraft is one of the vital systems for low-earth-orbit spacecraft in which the pointing accuracy is a highly recommended factor to satisfy its mission requirements. When any malfunction takes place at attitude actuator, the spacecraft will not satisfy the required mission objectives. It is required to identify specific faults for attitude actuators in a manner that helps to optimally recover this type of anomaly. An efficient anomaly detection and identification technique is a suitable way to identify such anomaly. This research introduces an accurate and high-performance methodology for fault detection and identification for spacecraft reaction wheels (RW) as (ADCS) actuator. Proposed approach is to differentiate among signatures of possible anomalies that may be occurred at RW like under-voltage, over-voltage, current losses, temperature decrease, and temperature increase. “Prony method,” as a feature extraction technique, is used to discriminate between normal system behavior and anomalies based on the three-axis spacecraft RW operation. A feed-forward neural network with back-propagation algorithm is used for anomaly identification. Prony order assessment is also carried out to obtain the proper order of poles and zeros to minimize the processing time required for identification. The results verify that the proposed anomaly identification is successfully accomplished with high degree of confidence and with minimal execution time. Research approach leads to generic methodology for anomaly identification process among all spacecraft subsystem anomalies.

An innovative test bed for verification of attitude control system

Experimental validation of the attitude determination and control subsystem performance is an essential requirement for new satellites. It can provide a very low cost and low risk environment for evaluating the proposed design before launch. One of the greatest difficulties in developing an Attitude Determination and Control Subsystem (ADCS) test bed is to perform the ground-based experiments in different environments to provide the orbital conditions experienced by a real spacecraft. Simulating the space environment is not an easy task and also testing of the attitude determination and control is very complicated. The essential requirements of functional tests in ADCS hardware are 1) rotational frictionless free motions, 2) simulating orbital environment for sensors and actuators, 3) software implementation of algorithms, and 4) finally integrating of these parts. Three degree of freedom (DOF) air bearing based simulators are the most common method for simulation of a frictionless media. Air bearing offers a nearly torque-free condition, perhaps as close as possible to that of space and hence it is a preferred technology for ground-based research in space attitude dynamics and control, although it certainly cannot provide the full experience of microgravity. There are several simulators around the world that are developed for many different education and research purposes. One of these simulators is developed for testing the bifocal relay mirror spacecraft system.

Fuzzy attitude control for a nanosatellite in low Earth orbit

In order to develop and introduce intelligent systems in the space field, an adaptive fuzzy logic controller is designed for a nanosatellite. Attitude determination and control subsystem (ADCS) and its performance and efficiency are compared with a traditional proportional integrative derivative (PID) controller. Fuzzy controllers have already been studied for satellite attitude control; however their performance has not been compared with the classical PID controllers typically being implemented on board spacecrafts currently. Both controllers have been designed and implemented in order to be tested on board a nanosatellite (QBITO) in a nearby mission (QB50), a constellation of 50 nanosatellites. Due to the requirements imposed by the mission, the orbit, and the significant limitations in the power available in these small spacecrafts, an efficient ADCS is required in order to fulfill the mission objectives. The comparison between the classical PID and the fuzzy controllers shows that the fuzzy controller is much more efficient in single maneuver (up to 65% less power required), achieving better precision in general than the PID. This shows that the use of this type of intelligent control systems is a great advantage over conventional control systems currently being used in satellite attitude control, and open new possibilities of application of intelligent controllers in the field of space technologies.

In-orbit results of Delfi-n3Xt: Lessons learned and move forward

This paper provides an update of the Delfi nanosatellite programme of the Delft University of Technology (TU Delft), with a focus on the recent in-orbit results of the second TU Delft satellite Delfi-n3Xt. In addition to the educational objective that has been reached with more than 80 students involved in the project, most of the technological objectives of Delfi-n3Xt have also been fulfilled with successful in-orbit demonstrations of payloads and platform. Among these demonstrations, four are highlighted in this paper, including a solid cool gas micropropulsion system, a new type of solar cell, a more robust Command and Data Handling Subsystem (CDHS), and a highly integrated Attitude Determination and Control Subsystem (ADCS) that performs three-axis active control using reaction wheels. Through the development of Delfi-n3Xt, significant experiences and lessons have been learned, which motivated a further step towards DelFFi, the third Delfi CubeSat mission, to demonstrate autonomous formation flying using two CubeSats named Delta and Phi. A brief update of the DelFFi mission is also provided.

Space Operations Monitoring Based on a New Statistical Principle Component Analysis Algorithm

The crucial concern of satellite operations is to ensure the health and safety of satellites. The worst case in this perspective is probably the loss of a mission but the more common interruption of satellite functionality can result in compromised mission objectives. All the data acquiring from the spacecraft are known as telemetry (TM), which contains the wealth information related to the health of all its subsystems. Each single item of information is contained in a telemetry parameter, which represents a time-variant property (i.e. a status or a measurement) to be checked. As a consequence, there is a continuous improvement of TM monitoring systems in order to reduce the time required to respond to changes in a satellite's state of health. A fast conception of the current state of the satellite is thus very important in order to respond to occurring failures. Statistical multivariate latent techniques are one of the vital statistical learning tools that are used to tackle the aforementioned problem coherently. Information extraction from such rich data sources using advanced statistical methodologies is a challenging task due to the massive volume of data. To solve this problem, in this paper, we present a new unsupervised statistical algorithm based on principle component analysis (PCA) latent technique. The algorithm is particularly applied to an actual remote sensing spacecraft. Data from the attitude determination and control subsystem (ADCS) was acquired under two operation conditions: normal and faulty states. The models were built and validated under these conditions and the results shows that the algorithm could successfully differentiate between these operations conditions. Furthermore, the algorithm provides competent information in prediction as well as adding more insight and physical interpretation to the ADCS operation.

Microsatellite Attitude Determination and Control Subsystem Design and Implementation: Software-in-the-Loop Approach

The paper describes the development of a microsatellite attitude determination and control subsystem (ADCS) and verification of its functionality by software-in-the-loop (SIL) method. The role of ADCS is to provide attitude control functions, including the de-tumbling and stabilizing the satellite angular velocity, and as well as estimating the orbit and attitude information during the satellite operation. In Taiwan, Air Force Institute of Technology (AFIT), dedicating for students to design experimental low earth orbit micro-satellite, called AFITsat. For AFITsat, the operation of the ADCS consists of three modes which are initialization mode, detumbling mode, and normal mode, respectively. During the initialization mode, ADCS collects the early orbit measurement data from various sensors so that the data can be downlinked to the ground station for further analysis. As particularly emphasized in this paper, during the detumbling mode, ADCS implements the thrusters in plus-wide modulation control method to decrease the satellite angular velocity. ADCS provides the attitude determination function for the estimation of the satellite state, during normal mode. The three modes of microsatellite adopted Kalman filter algorithm estimate microsatellite attitude. This paper will discuss using the SIL validation ADCS function and verify its feasibility.

Innovative power management, attitude determination and control tile for CubeSat standard NanoSatellites

Electric power supply (EPS) and attitude determination and control subsystem (ADCS) are the most essential elements of any aerospace mission. Efficient EPS and precise ADCS are the core of any spacecraft mission. So keeping in mind their importance, they have been integrated and developed on a single tile called CubePMT module. Modular power management tiles (PMTs) are already available in the market but they are less efficient, heavier in weight, consume more power and contain less number of subsystems. Commercial of the shelf (COTS) components have been used for CubePMT implementation which are low cost and easily available from the market. CubePMT is developed on the design approach of AraMiS architecture: a project developed at Politecnico di Torino that provides low cost and higher performance space missions with dimensions larger than CubeSats. The feature of AraMiS design approach is its modularity. These modules can be reused for multiple missions which helps in significant reduction of the overall budget, development and testing time. One has just to reassemble the required subsystems to achieve the targeted specific mission. • The designed electric power supply generates, distributes and converts power to different voltage levels. • CubePMT has three types of attitude sensors which are a sun directional sensor, a two-axis magnetometer and a gyroscope. • Reconfigurable magnetorquer system has been designed for attitude control. • Commercial ultra-low power MSP430F5438A has been used as an on-board processor. • For housekeeping and monitoring purposes different sensors e.g. voltage, current and temperature have been used.

Impact of the orbital eccentricity on the attitude performance before and after the deorbiting phase for Alsat-1

Due to the presence of periodic forcing terms in the gravity gradient torque, orbit eccentricity may produce large response for the roll, yaw and pitch angles. This paper investigates the influence of the orbit eccentricity on the performance of the attitude determination and control subsystem (ADCS) pointing of passive Low Earth Orbit (LEO) satellites stabilized by a gravity gradient boom or having long appendages before and after the deorbiting operation. The contribution of this work is twofold. First, the satellite attitude dynamics and kinematics are modeled by introducing the orbit eccentricity in the equations of motion of a LEO satellite in order to provide the best scenario in which satellite operators can keep the nominal functionality of LEO satellites with a gravity gradient boom after the deorbiting operation. Second, a Quaternion-based Extended Kalman Filter (EKF) is analyzed when the orbit eccentricity is considered in order to determine the influence of this disturbance on the convergence and stability of the filter. The simulations in this work are based on the true parameters of Alsat-1 which is a typical LEO satellite stabilized by a gravity gradient boom. The results show that the orbit eccentricity has a big influence on the pointing system accuracy causing micro-vibrations that affect the geocentric pointing particularly after the deorbiting phase. In this case, satellites have no orbital correction option. The Quaternion-based Extended Kalman Filter analyzed in this paper, achieved satisfactory results for eccentricity values less than 0.4 with respect to pointing system accuracy. However, singularities were observed for eccentricity values greater than 0.4.

Design and Simulation of Attitude Determination and Control Subsystem of CubeSat Using Extended Kalman Filtering and Linear Quadratic Gain Controller

This paper describes an integral scheme of the design and simulation of the Attitude Determination and Control Subsystem (ADCS) of CubeSat. CubeSat is an educational low-cost, cube-shaped Pico spacecraft. Attitude Determination (AD) is the problem of expressing the orientation of a spacecraft with respect to a given coordinate system. Three axis magneto-resistive digital magnetometer is selected as an attitude sensor. The International Geomagnetic Reference Field (IGRF) is used as reference for magnetometer to obtain attitude information. An enhanced orbit estimate/propagator is implemented to provide position information to IGRF model. Satellite environmental torque is modeled along with satellite kinematics and dynamics. Attitude estimation is done using Extended Kalman Filter (EKF) while the magnetic coils are used as actuators. Attitude Control is applied using Linear Quadratic Regulation (LQR) Controller. The designed ADCS is implemented in Matlab/Simulink.