Reaction Wheels Research Articles

General Lyapunov-based control design for a reaction wheel pendulum: A simulation study case

En este artículo se aborda el problema de control sobre un péndulo con rueda de reacción (RWP) a partir un diseño de control no lineal que se fundamenta en la teoría de estabilidad de Lyapunov. En primer lugar, se realiza el análisis de estabilidad de pequeña señal (método de linealización por series de Taylor) alrededor de los puntos de equilibrio del sistema en lazo abierto, lo que resulta para la posición vertical superior del RWP en un punto inestable de tipo silla, mientras que para la parte vertical inferior resulta en un foco estable. En segundo lugar, se diseña un controlador no lineal a partir de una función candidata de Lyapunov para diseñar el sistema de control en lazo cerrado, lo que genera una ley de control generalizada para el sistema con estructura no lineal que convierte el punto de equilibrio en la posición vertical superior en un foco estable. Validaciones numéricas demuestran que el diseño del controlador estabiliza el sistema en su punto de equilibrio entre los 400~ms y los 600~ms, lo que depende de las incertidumbres paramétricas del RWP y las variaciones de los parámetros de control. La principal contribución de este artículo corresponde a la generalización de la ley de control que, en función de los parámetros seleccionados puede resultar en una linealización exacta de las variables de estado o en un controlador no lineal generalizado para el RWP. Las validaciones computacionales se realizan en el software MATLAB, empleando el equivalente discreto del sistema con derivada hacia adelante.

Comparing Reaction Wheels and Magnetorquers Performance in the CubeSat Solar Observatory Stabilization

Comparing Reaction Wheels and Magnetorquers Performance in the CubeSat Solar Observatory Stabilization

LIWOM-GD: Enhanced LiDAR–Inertial–Wheel Odometry and Mapping by Fusion With Ground Constraint and Dynamic Points Elimination

LIWOM-GD: Enhanced LiDAR–Inertial–Wheel Odometry and Mapping by Fusion With Ground Constraint and Dynamic Points Elimination

Efficient machine learning based techniques for fault detection and identification in spacecraft reaction wheel

Efficient machine learning based techniques for fault detection and identification in spacecraft reaction wheel

Control of stance-leg motion and zero-moment point for achieving perfect upright stationary state of rimless wheel type walker with parallel linkage legs

Abstract The authors have studied models and control methods for legged robots without having active ankle joints that can not only walk efficiently but also stop and developed a method for generating a gait that starts from an upright stationary state and returns to the same state in one step for a simple walker with one control input. It was clarified, however, that achieving a perfect upright stationary state including zero dynamics is impossible. Based on the observation, in this paper we propose a novel robotic walker with parallel linkage legs that can return to a perfect stationary standing posture in one step while simultaneously controlling the stance-leg motion and zero-moment point (ZMP) using two control inputs. First, we introduce a model of a planar walker that consists of two eight-legged rimless wheels, a body frame, a reaction wheel, and massless rods and describe the system dynamics. Second, we consider two target control conditions; one is control of the stance-leg motion, and the other is control of the ZMP to stabilize zero dynamics. We then determine the control input based on the two conditions with the target control period derived from the linearized model and consider adding a sinusoidal control input with an offset to correct the resultant terminal state of the reaction wheel. The validity of the proposed method is investigated through numerical simulations.

Adaptive integral terminal sliding mode control of unmanned bicycle via ELM and barrier function

Abstract In this paper, an unmanned bicycle (UB) with a reaction wheel is designed, and a second-order mathematical model with uncertainty is established. In order to achieve excellent balancing performance of the UB system, an adaptive controller is designed, which is composed of nominal feedback control, compensating control using extreme learning machine observer and reaching control via integral terminal sliding mode (ITSM) and barrier function (BF)-based adaptive law. Owing to the features of BF-based ITSM (BFITSM), not only any uncertainty or disturbance upper bound is not needed any longer but also the finite-time convergence of the closed-loop system can be ensured with a predefined error bound. Moreover, the BF-based control gain can be adaptively adjusted according to the update of the lumped uncertainty such that the overestimation is removed. The stability analysis of the closed-loop system is given according to Lyapunov theory. Comparable experimental results on an actual UB are carried out to validate the superior balancing performance of the proposed controller.

Forced oscillation control with a wearable reaction wheel to assist human periodic arm swing

Rehabilitation for stroke patients includes periodic arm exercises, but these require assistance by caregivers at the start of the exercise, which is a burden for caregivers. In this study, we have developed a system with three reaction wheel mechanisms, which can generate not only moments in each direction but also a larger moment than the output of a single axis by interlocking the axes. In addition, by using forced oscillation control, it is possible to assist the movement of the wearer's periodic arm swing even if the weight and output moment of the reaction wheel is not large. Although a large torque of 2.65 Nm is required for the system to swing the arm, it was confirmed that the developed device can be used to increase the amplitude of arm oscillation and achieve an oscillation frequency equivalent to that of a human arm swing, even with a single reaction wheel exerting a torque of 0.4 Nm.

Rapid attitude stabilization of ultra-low orbit satellites using movable masses and reaction wheels

This paper proposes a combination of movable masses and reaction wheels for the attitude control of ultra-low-orbit satellites. During the attitude control of ultra-low-orbit satellites, the satellite’s attitude is significantly influenced by the aerodynamic torque. Therefore, this paper proposes a combined control method using movable masses and reaction wheels. By adjusting the position of the movable masses to modify the relative distance between the center of mass (CM) and the center of pressure (CP), the aerodynamic torque is effectively reduced. Additionally, a finite-time terminal sliding mode extended state observer (TSMESO) is incorporated to estimate the reduced aerodynamic torque. Then, a finite-time non-singular terminal sliding mode control (NTSMC) method is introduced to achieve rapid attitude stabilization. Simulations demonstrate that under the proposed control system, the aerodynamic torque acting on the ultra-low-orbit spacecraft can be significantly reduced in a short time, and the response and high precision attitude stability can be effectively achieved.

Detection and Analysis of Anomalous Behavior in On-Orbit Satellites Using AI Algorithms

The increasing deployment of satellites for essential applications necessitates robust anomaly detection to maintain their operational integrity. Traditional methods, which depend on manual monitoring and predefined thresholds, often prove inadequate in the complex space environment. This paper investigates the application of Artificial Intelligence (AI) algorithms to improve the detection and analysis of anomalous behavior in on-orbit satellites. AI, especially through machine learning (ML) and deep learning (DL), provides advanced capabilities for processing extensive telemetry data and identifying intricate patterns. By leveraging historical data, AI systems can establish normal operational parameters and detect deviations indicating potential anomalies. Techniques such as supervised and unsupervised learning are employed to develop models with high predictive accuracy. Furthermore, AI facilitates root cause analysis by correlating anomalies with operational conditions or external factors, enabling effective corrective measures. The integration of AI also promotes autonomous satellite operations, which are crucial for deep-space missions. This advancement enhances satellite reliability and safety, supporting sustainable and progressive space exploration. In this research, machine learning algorithms were employed to develop the proposed anomaly detection system. The system aims to detect subtle failures in the spacecraft’s attitude dynamics system, particularly in the reaction wheel subsystem, by learning solely from the spacecraft's nominal behavioral data. The system was developed from a small satellite's attitude dynamics control system, which may exhibit bearing failures in the reaction wheels. Two types of anomaly detection systems were introduced: a two-sided learning anomaly detection system and a one-sided learning anomaly detection system. For this study, a two-sided learning anomaly detection system was developed using the Logistic Regression (LR) method. This provided a foundation for the training process using a machine learning approach. By learning from both nominal and failure behaviors of the satellite, the system was designed to detect small reaction wheel friction failures effectively.

Optimal Synthesis of a Satellite Attitude Control System under Constraints on Control Torques and Velocities of Reaction Wheels

The problem of optimal synthesis of a nonlinear system’s control law parameters of satellite attitude control under constraints is considered. The maximum stability degree of a system is considered as an optimality criterion. The reaction wheels’ control moments and angular velocities achievable within the drives’ physical characteristics are considered as constraints. A linear model of the system converted from the original nonlinear model was used to solve the problem. The decomposition method, based on the transition from real time to relative time, is used to separate the tasks of optimality criterion maximization and constraints consideration. A method of synthesizing the optimal form of system transient process according to the maximum stability degree criterion is developed. An analytical method for determining the optimal values of control law parameters is proposed, based on the structural features of the linear differential equations system. A method that takes into account constraints on control moments and angular velocities of reaction wheels, based on transition scale from relative time to real time and its calculation algorithm, ensuring that conditions of all constraints are met, is developed. An example of solving the problem of optimal system synthesis is considered. The results demonstrate the effectiveness and simplicity of the proposed methods and algorithm for targeted selection of a system’s technical characteristics, taking into account constraints on reaction wheels’ maximum angular velocities and control moments values.

Reliable attitude control integrating reaction wheels and embedded asymmetric magnetorquers for detumbling CubeSats

The advent of CubeSats, compact satellites with a standardized form factor, has disrupted traditional space research paradigms, fostering innovation and collaboration across academic institutions and industries. Following deployment, CubeSats typically employ magnetorquer rods to initiate the detumbling sequence, gradually reducing the angular velocity before transferring control to reaction wheels for complete spin neutralization. However, this conventional approach entails a substantial spacecraft space requirement, necessitating an alternative and disruptive methodology. Furthermore, considering that approximately 50% of Attitude Determination and Control Subsystems (ADCS) failures are attributed to faults related to the moving parts in reaction wheels, strategies are taken into consideration to address a worst-case scenario of reaction wheels failure. This paper introduces a disruptive approach that uses diverse geometries and a non-unity track width ratio in PCB-integrated magnetorquers with reaction wheels for comprehensive control. We demonstrate the effectiveness of various coil configurations through a series of extensive simulations and establish a systematic framework to select optimal hybrid designs tailored to specific mission requirements.

Novel scheme for uncertainty and disturbance estimation to control of spacecraft system with input constraint

In this paper, a novel scheme is presented to estimate the uncertainty and disturbance of the spacecraft system by a compensatory vector calculated online from the information of measured angular velocities. The compensatory vector is used in the constrained attitude control law to compensate for the perturbations of the spacecraft system. The attitude controller considering the input limitations of reaction wheels is developed by solving an optimization problem through the Karush-Kuhn-Tucker (KKT) theorem. By using noisy angular velocities in the observer design, the stochastic stability of the closed loop system under the constrained multivariable controller is demonstrated. In the results, at first, the open-loop performance of the uncertainty and disturbance observer is evaluated through computer simulations. Subsequently, the performance of the proposed controller in both constrained and unconstrained versions is evaluated. Finally, the proposed controller performance in compensating for uncertainties and disturbances is compared with the adaptive backstepping controller reported in the literature. The comparative results of two controllers show the superior performance for the proposed constrained controller in the presence of disturbances, uncertainties and input constraints. Furthermore, the proposed control system could attenuate the effect of measurement noises of angular velocities by weighting the compensatory vector in the observer design.

Adaptive second-order backstepping control for a class of 2DoF underactuated systems with input saturation and uncertain disturbances

An adaptive second-order backstepping control algorithm is proposed for a kind of two degrees of freedom (2DoF) underactuated systems. The system dynamics is transformed into a nonlinear feedback cascade system with an improved global change of coordinates. Fully taking the cascade structure into consideration and in order to simplify the design process, each step in the backstepping process is designed for a second-order subsystem. Two neural networks are applied to approximate system unknown functions and two adaptive laws are designed to estimate the upper bound of the sum of approximation error and external disturbances. To overcome the explosion problem of complexity, a second-order filter is applied to produce the virtual control and its second-order derivative that is needed in the next backstepping step. Two auxiliary dynamic systems are proposed and integrated into the backstepping process to eliminate the effects of filtering error and input saturation. The system stability is analyzed by the Lyapunov stability theory and verified by numerical simulations with two 2DoF benchmark underactuated systems: the translational oscillator with a rotational actuator (TORA) and the inertial wheel pendulum (IWP).

Attitude Control for a satellite with inertial wheels based on Attractive Ellipsoids Method

Abstract This article presents a robust control law based on the Attractive Ellipsoids Method applied to perform attitude control of a satellite that has inertial wheels and relatively small dimensions such as microsatellites or other similar architectures. The novelty lies in the fact that under certain characterized external and parametric perturbations it is possible to track the desired angular trajectory with an optimization method to determine the computed torque. Additionally, a demonstration of this methodology is carried out with a numerical example.

Spacecraft attitude testbed

Spacecraft attitude determination and control systems (ADCS) stand as a pivotal factor for ensuring the success of missions. As satellite sizes continue to decrease, the need for more intelligent and efficient control algorithms becomes increasingly pronounced. In response to this imperative, we propose the development of a scaled-down testbed specifically designed for evaluating satellites (ACDS). This testbed will demonstrate effective control of a CubeSat through the use of Helmholtz coils, magnetic torquer solenoids, reaction wheels and inexpensive student-made components and available components off the shelf (COTS) in the San Diego State University SPACE Lab. Referred to as the Spacecraft Attitude Testbed (SAT), this custom-designed 3-DoF experimental attitude platform replicates the conditions experienced by a weightless satellite in space. The objective of this research paper is to improve the understanding of how to manufacture a testbed and components like those within this paper, expose some of the issues encountered and improve the outcomes for future academic testbeds. Within this study, the testbed employs torque application to magnetic torquers and reaction wheels to regulate attitude. In summary, this research endeavors to establish a comprehensive and cost-effective testbed platform dedicated to the assessment of spacecraft attitude control and determination systems. It not only seeks to enhance our understanding of advanced control algorithms but also aims to contribute valuable insights into fault detection and adaptive control strategies, ultimately bolstering the efficiency and robustness of satellite operations.

Micro-vibration simulation of laser communication satellite subjected to the disturbance of momentum wheels

Micro-vibration simulation of laser communication satellite subjected to the disturbance of momentum wheels

Analytical method and experimental verification of coupled micro-vibration for spacecraft based on mechanical impedance theory

Micro-vibrations exert detrimental effects on spacecraft that requires extreme precision performance. Dynamic mass method (DMM) is a component-level grounded micro-vibration measurement method, which is widely used in the analysis of coupled interplay between micro-vibration sources and spacecraft. However, this study reveals that all existing research involving DMM contains a fundamental error during its theoretical derivation. In light of this, the root cause of the error is investigated based on the mechanical impedance theory. Building upon this, a modified dynamic mass method (MDMM) is further proposed, and corresponding solution steps are also given, with emphasis on the treatment of gyroscopic effects of reaction wheels (RWs). To validate this analytical method, a grounded micro-vibration measurement system for RWs is designed and established. Micro-vibrations of an RW are measured under both the rigid-mounted and isolated conditions, respectively. Leveraging the physical parameters of the isolator, MDMM is applied to process the micro-vibration data measured under a rigid-mounted condition, which predicts the transmitted data under an isolated condition. The analytical data produced by MDMM agrees well with the measured results, which partially validates the feasibility and effectiveness of the proposed MDMM. This analytical method proposed in this work can serve as a theoretical tool for both measurement and analysis of the coupled micro-vibrations of sources and spacecraft.

Optimization, guidance, and control of low-thrust transfers from the Lunar Gateway to low lunar orbit

The Lunar Gateway will represent a primary space system useful for the Artemis program, Earth–Moon transportation, and deep space exploration. It is expected to serve as a staging location and logistic outpost on the way to the lunar surface. This study focuses on low-thrust transfer dynamics, from the Near-Rectilinear Halo Orbit traveled by Gateway to a specified Low-altitude Lunar Orbit (LLO). More specifically, this research addresses two closely-related problems: (i) determination of the minimum-time low-thrust trajectory and (ii) design, implementation, and testing of a guidance and control architecture, for a space vehicle that travels from Gateway to LLO. Orbit dynamics is described in terms of modified equinoctial elements, with the inclusion of all the relevant perturbations, in the context of a high-fidelity multibody ephemeris model. The minimum-time trajectory from Gateway to a specified lunar orbit is detected through an indirect heuristic approach, which uses the analytical conditions arising in optimal control theory in conjunction with a heuristic technique. However, future missions will pursue a growing level of autonomy, and this circumstance implies the mandatory design and implementation of an efficient feedback guidance scheme, capable of compensating for nonnominal flight conditions. This research proposes nonlinear orbit control as a viable and effective option for autonomous explicit guidance of low-thrust transfers from Gateway to LLO. This approach allows defining a feedback law that enjoys quasi-global stability properties without requiring any offline reference trajectory. The overall spacecraft dynamics is modeled and simulated, including attitude control and actuation. The latter is demanded to an array of reaction wheels, arranged in a pyramidal configuration. Guidance, attitude control, and actuation are implemented in an iterative scheme. Monte Carlo simulations demonstrate that the guidance and control architecture at hand is effective in nonnominal flight conditions, i.e. with random starting point from Gateway as well as in case of temporary unavailability of the propulsion system. The numerical results also point out that only a modest propellant penalty is associated with the use of feedback guidance and control in comparison to the minimum-time optimal trajectory.

Integrated attitude—orbit control of solar sail with single-axis gimbal mechanism

A new attitude control method for solar sails is proposed using a single-axis gimbal mechanism and three-axis reaction wheels. The gimbal angle is varied to change the geometrical relationship between the force due to solar radiation pressure (SRP) and the center of mass of the spacecraft, such that the disturbance torque is minimized during attitude maintenance for orbit control. Attitude maneuver and maintenance are performed by the reaction wheels based on the quaternion feedback control method. Even if angular momentum accumulates on the reaction wheels due to modelling error, it can also be unloaded by using the gimbal to produce suitable torque due to SRP. In this study, we analyzed the attitude motion under the reaction wheel control by linearizing the equations of motion around the equilibrium point. Further, we newly derived the propellent-free unloading method based on the analytical formulation. Finally, we constructed the integrated attitude-orbit control method, and its validity was verified in integrated attitude-orbit control simulations.

Design and Development of Self Balancing Two Wheeler

The Self-balancing robots represent a fascinating intersection of technology and practical application. This project aims to design and develop a self-balancing two- wheeler robot capable of maintaining stability and balance autonomously. Drawing inspiration from principles observed in human balance and locomotion, the robot employs a combination of sensors, actuators, and control algorithms to achieve its objective. The project begins with an in-depth literature survey, exploring existing research and methodologies in the field of self-balancing robotics. Leveraging insights from key publications, the project outlines fundamental principles, sensor fusion techniques, advanced control methodologies, and challenges inherent in self-balancing robot design. Key components including an Arduino Uno board, accelerometers, gyroscopes, DC motors, batteries, and optional reaction wheels are carefully selected and integrated into the robot's hardware architecture. A systematic approach to hardware selection, assembly, sensor integration, microcontroller programming, and motor control ensures a coherent and functional design. Throughout the development process, emphasis is placed on rigorous testing, calibration, and iterative improvement. The robot is subjected to various environmental conditions and scenarios to validate its stability and performance. Calibration procedures refine sensor accuracy and control algorithms, enhancing the robot's ability to maintain balance under dynamic conditions. The project culminates in the creation of a comprehensive documentation package, detailing schematics, code explanations, assembly instructions, and testing methodologies. Additionally, a presentation showcases the robot's functionality, design rationale, and potential applications. By meticulously following the outlined steps and leveraging insights from existing research, this project aims to contribute to the advancement of self-balancing robotics and serve as a foundation for future exploration and innovation in this exciting field