Single Gimbal Control Moment Gyros Research Articles

Path Planning for Rapid Large-Angle Maneuver of Satellites Based on the Gauss Pseudospectral Method

A Gauss pseudospectral method is proposed in this study to solve the optimal trajectory-planning problem for satellite rapid large-angle maneuvers. In order to meet the requirement of rapid maneuver capability of agile small satellites, Single Gimbal Control Moment Gyros (SGCMGs) are adopted as the actuators for the attitude control systems (ACS). Because the singularity problem always exists for SGCMGs during the large-angle maneuvering of the satellites, a trajectory optimization method for the gimbal rates is developed based on the Gauss pseudospectral method. This method satisfies the control requirement of satellite rapid maneuvers and evades the singularity problem of SGCMGs. The method treats the large-angle maneuver problem as an optimization problem, which meets the boundary condition and a series of the physical constraints including the gimbal angle constraint, the gimbal rates constraint, the singularity index constraint, and some other performance criteria. This optimization problem is discretized as a nonlinear programming problem by the Gauss pseudospectral method. The optimal nonsingularity gimbal angle trajectory is obtained by the sequence of quadratic programming (SQP). This approach avoids the difficulties in solving the boundary value problem. The simulations reveal that the Gauss pseudospectral method effectively plans an optimal trajectory and satisfies all the constraints within a short time.

Spacecraft maneuvers via singularity-avoidance of control moment gyros based on dual-mode model predictive control

Attitude control is investigated for a rigid spacecraft using single gimbal control moment gyros (SGCMGs) as actuators. By taking spacecraft and SGCMGs as an integrated system, the combined dynamics of SGCMGs and spacecraft are fully considered. The singularity problem of the SGCMGs is converted into the problem of state constraints and input constraints, and by so doing, the actuation capacity of the SGCMGs is fully utilized. To ensure accurate real-time computation, the Gauss pseudospectral and sequential quadratic programming methods are used to solve the attitude path planning of the system. Considering the uncertainties of the external disturbances and the estimation error of the inertia matrix, feedback control of the system is designed by using nonlinear model predictive control. Finally, dual-mode model predictive control is used to ensure the stability of the system, and the H8 controller and the estimated hyperellipsoid region of attraction of the linearized system are given. Simulation results show good tracking performance and robustness of the designed controller. The modeling method and the control method given in the paper provide a solution to the singularity problem of the SGCMGs.

Attitude tracking of a rigid spacecraft using two internal torques

The attitude-tracking control of a rigid spacecraft using only two internal torques is addressed. First, a given reference trajectory is classified as feasible or unfeasible according to the preservation or violation of the momentum conservation law. The dynamics of the attitude-tracking error is then formulated on the attitude manifold SO(3) with the angular momentum of the actuators as inputs. Given the Lie group structure of SO(3), the transverse function approach is utilized to design an attitude-tracking law ensuring asymptotically ultimately bounded tracking error for any reference trajectory. For feasible reference trajectories satisfying certain persistence conditions, asymptotic tracking is achieved by constructing an asymptotically stable zero dynamics for the closed-loop system. To deliver control torques to the actuator command signals, steering laws are designed for two reaction wheels, two single-gimbal control moment gyros mounted in parallel, and one variable-speed control moment gyro, respectively. The resulting control law can be applied to a spacecraft with different kinds of momentum actuators but underactuated for tasks ranging from bounded tracking of a generic trajectory, three-axis earth pointing to line-of-sight pointing, etc. Numerical examples are presented to verify the effectiveness of the proposed method.

New Sliding Mode Control Approach for Rapid Attitude Maneuver Using Control Moment Gyros

AbstractA single-gimbal control moment gyro (CMG) is considered to be an ideal torque-generating actuator for rapid attitude maneuvering due to its relatively large output torque. A new attitude control method that is based on the modified Rodrigues parameter (MRP) sliding mode control law for a pyramidal configuration using four CMGs is proposed. Robust inverse steering logic is used to avoid issues of the singularity of the CMGs. The proposed approach is expected to provide rapid and stable attitude maneuvering while avoiding the singularity of the CMGs. In addition, this method is demonstrated on a small satellite, named TSUBAME, designed by the Laboratory of Space Systems at the Tokyo Institute of Technology. The proposed control algorithm is verified through a Monte Carlo simulation and a software-in-the-loop attitude simulator for TSUBAME. The Monte Carlo simulation demonstrated that the new sliding mode control approach successfully tracks a time varying attitude for a nanosatellite model with a ra...

Magnetic Gimbal Angle Compensator of CMG-Based Controlled Small Satellite

The presence of external disturbance torques causes the gimbals angle of Control Moment Gyros (CMG) used to control satellite drift from their preferred initial value. This scenario will drive the CMG into singular states or result in attitude error thus reducing the chance to do slew maneuver. In this paper, a novel method to compensate drifted gimbals of CMG based controlled small satellite operated in low earth orbit is adopted. The satellite is equipped with four Single Gimbal CMG (SGCMG) pyramid-array configuration. Three magnetic torquers are used to generate the compensation control torque where the controlleris designed based on the gimbal angle converging time. Simulations are performed using Matlab®/Simulink® software for various value of gimbals angle converging time to optimize the compensator performance. Results from simulation show that the optimal performance of the system is when the converging time is set at100s.

Robust controller design of SGCMG driven by hollow USM

This work proposes a design for robust control system of a single-gimbal control moment gyro (SGCMG) driven by a hollow ultrasonic motor. Considering the nonlinear characteristic of the whole system, the fuzzy Takage-Sugeno control theory was introduced to achieve a robust control over wide range stability. Based on the proposed control theory, the parameters of feedback control of close loop were determined, and a whole system model has been build for system simulation and robust controller research. The simulation results have shown the effectiveness of the proposed control algorithm. The proposed controller was implemented on an embedded microcontroller unit through C language. On the actual system of SGCMG driven by ultrasonic motor, a sinusoidal signal speed tracking has shown that the speed error less 0.5°/s and the close loop system express a good stability over a referenced speed range of 0.2---72°/s. Step response experiments shown that the system fast response time without overshot. The experiments have verified the proposed robust control algorithm in speed, robustness and stability.

基于terminal滑模控制的小卫星机动方法

The attitude maneuver and stable task of a small satellite by using a Single Gimbal Control Moment Gyro(SGCMG)as an actuator was explored with the terminal sliding mode control method.Firstly,a small satellite mathematical model was established based on the Modified Rodrigues Parameters(MRP),and the torque planning was made in the terminal sliding mode control method.Then,command torque was given through diagonal singular robust tracking control law using the SGCMG as an actuator.The performance of the control method was studied by mathematical simulation,and the changing law and chosen rule of design parameters of the terminal sliding mode control were presented.Finally,a small satellite three-axis air flotation turntable was used to verify the adaptability of terminal sliding mode control.The experimental results show that the attitude angle and attitude an-gular velocity control precision and steady state error is less than 0.1°and 0.01(°)/s,which is within the scope of the best control precision from the parameter selection principle in the three-axis air flotation turntable for small satellite maneuver stability experiment.It concludes that the terminal sliding mode control method has high control precision and stability and is able to give a good function for small satellite maneuvers.

Design and Dynamic Analysis of Micro-vibration Isolator for Single Gimbal Control Moment Gyro

Control moment gyros (CMGs) are widely used for attitude control in spacecraft. However, micro-vibrations generated from these high speed spinning actuators has a significant impact on high-sensitivity space mission. Based on the energy dissipation mechanism of viscoelastic material, this research puts forward a passive isolator for Single Gimbal CMG (SGCMG). Dynamic model of this proposed isolator is developed and analyzed, and then isolation performance is improved through parameters optimization. Numerical simulations indicate that disturbances with frequency above 40Hz can be isolated in all six degrees of freedom. In addition, the resonant peak in transmissibility has been greatly suppressed due to the structural damping that provided by viscoelastic material.

On the attitude stabilization of a rigid spacecraft using two skew control moment gyros

The attitude control of a rigid spacecraft with two skew single-gimbal control moment gyros (CMGs), which is subject to an underactuated nonholonomic constraint, is investigated. Nonlinear control theory is used to show that the combined dynamics of the spacecraft-CMG system are small-time locally controllable (STLC) from and feedback stabilizable to any equilibrium where two CMGs never encounter certain special configurations. Specially, the attitude stabilization issue is approached under the restriction that the total angular momentum of the spacecraft-CMG system is zero, which not only guarantees that the feasible equilibrium attitude can be any orientation but also renders STLC for these attitudes. In order to overcome the troublesome singular problem of two skew CMGs, a nonlinear approximation of the full attitude equations is derived for control law design by assuming that the spacecraft angular velocity is small. A novel singular quaternion stabilization law is then proposed to stabilize the spacecraft attitude with bounded angular velocities, which in turn ensures the satisfaction of the small angular velocity assumption during the entire control process. Numerical examples and experimental results validate the effectiveness of the proposed control method in stabilizing the full spacecraft-CMG system.

Three-Axis Attitude Control Performance of a Small Satellite Using Control Moment Gyroscope

In this paper, a three-axis attitude control of a small satellite employing control moment gyroscope (CMG) is presented. A four single gimbal control moment gyroscopes (4-SGCMG) cluster has been employed as the actuator and a proportional-derivative (PD) based attitude control approach has been utilized. The singularity robust (SR) steering law has been employed to investigate its capability in avoiding the singularity state of the CMG system with respect to the mission operation by setting the initial gimbal angle further from the singularity state. The presented control law was simulated in the MATLAB® SIMULINK® software. Results obtained from the simulation show the effectiveness of the control algorithm.

Technical Note: Space Station Zero Propellant Maneuver Path Planning Considering SGCMG Saturation and Singularity

The zero-propellant maneuver is an advanced concept of the spacecraft attitude control. The problem of zero-propellant maneuver using single gimbal control moment gyroscopes is researched in this paper. The saturation and singularity problems of single gimbal control moment gyroscopes are analyzed, and the performance indexes to measure saturation and singularity are proposed. The path planning model considering the gimbal steering law is established using modified rodrigues parameter. Then, a hybrid approach combining the pseudospectral method and direct shooting method is proposed to solve the nonlinear path planning problem with complicated constraints. Finally, the numerical simulation is executed to validate the effectiveness of the proposed method. It is shown that an optimized attitude maneuver path satisfying the saturation and singularity constraints can be obtained and the zero-propellant maneuver using single gimbal control moment gyroscopes can be successfully achieved.

Maneuver planning of a rigid spacecraft with two skew control moment gyros

The attitude maneuver planning of a rigid spacecraft using two skew single-gimbal control moment gyros (CMGs) is investigated. First, two types of restrictions are enforced on the gimbal motions of two skew CMGs, with each restriction yielding continuous control torque along a principal axis of the spacecraft. Then, it is proved that any axis fixed to the spacecraft can be pointed along an arbitrary inertial direction by at most two sequent rotations around the two actuated axes. Given this fact, a two-step eigenaxis rotation strategy, executing by the two single-axis torques respectively, is designed to point a given body-fixed axis along a desired direction. Furthermore, a three-step eigenaxis rotation strategy is constructed to achieve an arbitrary rest-to-rest attitude maneuver. The rotation angles required for the single-axis pointing and arbitrary attitude maneuver schemes are all analytically solved. Numerical examples are presented to demonstrate the effectiveness of the proposed algorithms.

Directional passability and quadratic steering logic for pyramid-type single gimbal control moment gyros

Singularity analysis and the steering logic of pyramid-type single gimbal control moment gyros are studied. First, a new concept of directional passability in a specified direction is introduced to investigate the structure of an elliptic singular surface. The differences between passability and directional passability are discussed in detail and are visualized for 0H, 2H, and 4H singular surfaces. Second, quadratic steering logic (QSL), a new steering logic for passing the singular surface, is investigated. The algorithm is based on the quadratic constrained quadratic optimization problem and is reduced to the Newton method by using Gröbner bases. The proposed steering logic is demonstrated through numerical simulations for both constant torque maneuvering examples and attitude control examples.

Tip-over stability enhancement for omnidirectional mobile robot

Purpose – The purpose of this paper is to analyze the stability behavior of the omnidirectional mobile robot with active dual-wheel caster (ADWC) assemblies and provide a stable trajectory without any tip-over incident. The omnidirectional mobile robot to be developed is for transporting cuboid-shaped objects. Design/methodology/approach – The omnidirectional transport mobile robot is designed using an ADWC assemblies structure, the tip-over occurrence is estimated based on the support forces of an active footprint, the tip-over direction is predicted, the tip-over stability is enhanced to prevent the tip-over occurrence and a fast traveling motion is provided. Findings – The omnidirectional mobile robot tends to tip-over more on the sides with small ranges of tip-over angle. The proposed method for estimating the tip-over occurrence and enhancing the stability using the gyroscopic torque device was feasible as the tip-over prevention system of the omnidirectional mobile robot with ADWC assemblies. Originality/value – The research addresses the study of the tip-over stability for the omnidirectional mobile robot that possesses an active footprint. It also addresses the prediction of the tip-over occurrence using the derived dynamical model together with force-angle stability measure and the tip-over stability enhancement method using a single-gimbal control moment gyro device.

Evaluation of Steering Algorithm Optimality for Single-Gimbal Control Moment Gyroscopes

Analytic optimization methods typically used to derive optimal steering algorithms for single-gimbal control moment gyros do not consider the structure of the Jacobian matrix mapping the gimbal rates onto the desired torque within their cost function. Many of the steering algorithms resulting from these optimization methods systematically take first and second derivatives, forming the Jacobian and Hessian matrices to obtain a solution. However, the optimality is usually a local result and cannot be mapped back to its resulting performance. It is shown that the majority of steering algorithms are optimal with respect to one specific cost function previously published and that the design of the weighting matrices within the cost is what distinguishes steering algorithms. The author analytically shows how the blended inverse, Moore-Penrose pseudoinverse, generalized inverse steering law, singularity robust inverse, generalized singularity robust inverse, singular direction avoidance, local-gradient methods, and the hybrid steering logic are derived from the same optimizations but their sense of optimality is lost because the structure of singularities is not considered in the optimization process. In addition, the author also points out that the design of the quadratic costs weighting matrix used for optimization and desired gimbal rate is of the highest importance in differentiation between steering law performance.

Design of SGCMG and long life rotor bearing system technology in Tiangong-1

Single-gimbal control moment gyroscope (SGCMG) is a key attitude control actuator of Tiaqngong-1 target spacecraft. Since the successful launch of Tiangong-1 in September, 2011, the SGCMGs in it have been working smoothly in-orbit with excellent performance, which have accomplished the mission of attitude control of Tiangong-1 as well as the rendezvous docking. Now, the SGCMGs are working in the extension mission phase. In this paper, the mission requirement, design proposal, and the key technology-design of long life rotor bearing system and its test result are introduced. The SGCMGs in Tiangong-1 are developed independently by our country and utilized in-orbit for the first time. The design of long life rotor bearing system provides an important reference for SGCMGs in other spacecraft.

Fault Tolerant Attitude Control for Small Satellites Using Single Gimbal Control Moment Gyros and Magnetic Torquers

AbstractA fault tolerant control scheme is proposed for the attitude stabilization of a small satellite using single gimbal control moment gyros (SGCMGs) and magnetic torquers (MTQs). The dynamic model of a rigid spacecraft using SGCMGs and MTQs is established, and the faults of SGCMGs are modeled as additive and multiplicative unknown dynamics. By designing a well-tuned linear extended state observer (LESO), the dynamic uncertainties, external disturbances, and the unknown faults of SGCMGs are estimated accurately and compensated actively in real time without knowing the exact spacecraft model. Then, based on the singular value decomposition (SVD) theory, the command torque is decomposed and distributed to SGCMGs and MTQs, respectively; therefore SGCMGs only need to output the torque component orthogonal to the singular direction when encountering singularity, ensuring the controllability of SGCMGs. Through comparison with a conventional proportional-derivative (PD) control method, the numerical simulati...

Robust attitude control of nano-satellite using control moment gyros based on higher order sliding modes

Rapid attitude orientation and stable pointing accuracy are critical characteristics for observation missions of nano-satellite nowadays. This paper focuses on analysis of attitude control law for nano-satellite TSUBAME which is developed by Laboratory of Space System at Tokyo Institute of Technology. In recent years, the higher order sliding mode control (HOSMC) is considered, which is more useful in handling the chattering effect against external disturbance and unknown friction effects. Furthermore, HOSMC can remove the chattering effect if appropriate relative degree was chosen. To overcome the singularity problem inherent in the control moment gyros, a modified steering law for single gimbal control moment gyros (SGCMG), which aims at precisely exporting commanded torque is discussed based on the optimal output torque capability principle. This paper includes a comparison between two different control algorithms in the attitude controlling system which used control moment gyro (CMG) as the actuator for TSUBAME. The numerical simulation results demonstrate the efficiency and feasibility of the proposed HOSMC algorithm.

Small-Time Local Controllability and Stabilizability of Spacecraft Attitude Dynamics under CMG Actuation

The purpose of this paper is to examine whether the presence of singular configurations poses an obstruction to the small-time local controllability (STLC) and stabilizability of the attitude dynamics of a spacecraft actuated by single-gimbal control moment gyroscopes (CMGs). We identify a class of singular CMG configurations called critically singular configurations, at which the linearized dynamics fail to be controllable. Linear controllability, and hence STLC and stabilizability, hold at equilibria in which the CMG array is in a nonsingular or singular, but not critically singular, configuration. We give sufficient conditions and necessary conditions on critically singular configurations for STLC to hold. In particular, we show that STLC and stabilizability fail to hold at an equilibrium if the magnitude of the total spin angular momentum of the CMG array has a local maximum at the equilibrium.

Coupled dynamic analysis of a single gimbal control moment gyro cluster integrated with an isolation system

Control moment gyros (CMGs) are widely used as actuators for attitude control in spacecraft. However, micro-vibrations produced by CMGs will degrade the pointing performance of high-sensitivity instruments on-board the spacecraft. This paper addresses dynamic modelling and performs an analysis on the micro-vibration isolation for a single gimbal CMG (SGCMG) cluster. First, an analytical model was developed to describe both the coupled SGCMG cluster and the multi-axis isolation system that can express the dynamic outputs. This analytical model accurately reflects the mass and inertia properties, the gyroscopic effects and flexible modes of the coupled system, which can be generalized for isolation applications of SGCMG clusters. Second, the analytical model was validated using MSC.NASTRAN software based on the finite element technique. The dynamic characteristics of the coupled system are affected by the mass distribution and the gyroscopic effects of the SGCMGs. The gyroscopic effects produced by the rotary flywheel will stiffen or soften several of the structural modes of the coupled system. In addition, the gyroscopic effect of each SGCMG can interact with or counteract that of others, which induce vibration modes coupled together. Finally, the performance of the passive isolation was analysed. It was demonstrated that the gyroscopic effects should be considered in isolation studies on SGCMG clusters; otherwise, the isolation performance will be underestimated if they are ignored. • We developed an analytical model for vibration isolation of SGCMG cluster. • The model describes the coupled dynamics of the SGCMG cluster and isolation system. • The model is universal for SGCMG cluster for some kind of mounting configuration. • Dynamic characteristics and isolation performance of the isolation system are influenced by the gyroscopic effects. • The passive isolation filters much of the disturbance and will not affect attitude control.