Single Gimbal Control Moment Gyros Research Articles

Output torque modeling of control moment gyros considering rolling element bearing induced disturbances

Control moment gyros (CMG) have been widely used in spacecraft attitude control and large angle slewing maneuvers over the years. Understanding and suppressing high-frequency disturbances in CMG’s output torques is a crucial factor to achieving the desired level of payload performance. Output torque modeling of a single gimbal CMG (SGCMG) with nonlinear rolling bearing supports is conducted in this paper. Taking the installation errors and micro-vibrations of the flywheel into account, three axis output torques of a SGCMG are derived based on Newton-Euler approach and theorem of moment of momentum. Dynamic model is then constructed to obtain the micro-vibration responses of the rotary flywheel. Mass imbalances of the flywheel, flexibility of supporting structures and nonlinearity induced by one pair of angular contact ball bearings are considered in the dynamic model. Especially for the rolling bearing, an improved load distribution analysis is proposed to more accurately obtain the contact deformations and angles between the rolling balls and raceways. Various factors, including the preload condition, surface waviness, Hertz contact and elastohydrodynamic lubrication, are included in the analysis. The bearing restoring forces are then obtained through iteratively solving the load distribution equations at every time step. Dynamic tests on a typical SGCMG supported by angular contact ball bearings are conducted to verify the output torque model. The effects of flywheel dynamic/static eccentricities, inner/outer surface waviness amplitudes, bearing axial preload and installation skew angles on the dynamic output torques are discussed. The obtained results would be useful for the optimal design and vibration control of the SGCMG system.

Experimental Verification of Singularity-Robust Torque Control for a 1.2-Nm–5-Hz SGCMG

A single gimbal control moment gyro (SGCMG) has been designed and developed as a torque amplifier to generate 1.2-Nm–5-Hz gyroscopic torque for the angle deviation of 45°. Since the SGCMG is aimed to generate the torque accurately in the designated direction, the return of the gimbal from the disturbance should be guaranteed within a desired frequency. However, unexpected axial drift exists and leads to a null motion under the torque control scheme. Therefore, this paper identifies the cause of axial drift and proposes a new torque control technique with two phases of compensation. Compensator I is designed to eliminate the nonlinear axial drift modeled as a sigmoidal function through an empirical identification process. Compensator II reduces other uncertainties by integrating high-pass filtering, recursive least square, all pass filtering, and moving average filtering (MAF) process. Finally, the proposed control scheme has been verified through experimental studies.

Single Gimbal Control Moment Gyro를 장착한 크레인의 제어에 관한 연구

Single Gimbal Control Moment Gyro를 장착한 크레인의 제어에 관한 연구

Singularity analysis for single gimbal control moment gyroscope system using space expansion method

Control Moment Gyroscope (CMG) is an effective candidate for agile satellites and large spacecraft attitude control because of its powerful torque amplification capability. The most serious situation, however, in using CMG is the inherent geometric singularity problem, where there’s no torque output along a particular direction. Space expansion method has been proposed in this work for the singularity analysis. Based on inverse mapping transformation, an expanded Jacobian matrix which is a full rank square matrix is obtained. The singular angle sets of the 3-parallel cluster and pyramid cluster are distinguished using space expansion method. An effective hybrid steering strategy, able to deal with the elliptic singularity, is further proposed. Simulation results demonstrate the excellent performance of the proposed steering logic compared to the generalized singular robust logic and pseudo inverse logic in terms of energy consumption and torque error.

Agile Attitude Control and Singularity Avoidance/Escape by the SDRE Method Using a Biased State-Dependent Weighting Matrix

In recent years there has been an increasing need to improve satellite attitude control performance in terms of agility and attitude accuracy in large-angle attitude maneuvers. To achieve such control performance, single-gimbal control moment gyros (SGCMGs) should be mounted as modern-type actuators. Conventionally, based on the torque command calculated by the attitude control system of the satellite, SGCMGs were controlled by solving inverse kinematics through a pseudo inverse matrix steering law. However, in such a control system structure, it may be difficult to obtain the desired torque required by the attitude control system because of the singularity problem of SGCMGs. Furthermore, with respect to implementation, since the condition number of the Jacobian matrix of SGCMG becomes extremely large in the singularity, the numerical calculation error of the pseudo inverse matrix increases greatly. Therefore, we propose an overall control system that can solve above-described problems and the state-dependent Riccati equation (SDRE) control system that integrates the satellite and SGCMG system. The proposed optimal control system, which does not solve the pseudo inverse matrix, can realize gimbal angle guidance by gimbal angle feedback and singularity avoidance/escape using the biased weighting matrix. In the numerical simulation, the usefulness of proposed system is shown in comparison with the conventional system.

Directional Singularity Escape and Avoidance for Single-Gimbal Control Moment Gyroscopes

Despite the long history of studies on the singularity problem inherent to single-gimbal control moment gyroscopes, few existing gimbal steering laws can both accurately track moments and escape or avoid every type of singularity. The most-referenced steering laws perturb the system suboptimally at every singularity to enforce escape, which creates a tradeoff between minimizing escape time and minimizing transient tracking errors and gimbal rates. It is shown that no such tradeoff is necessary by proposing new singularity measures to quantify the current and future reference moment tracking capabilities and defining explicitly how an anticipated singularity can be avoided or escaped. Using these measures to separate and prioritize the tasks of moment tracking, gimbal damping, and singularity escape and avoidance, a gimbal steering law is designed that accurately tracks moments and avoids singularities when possible while escaping them with a minimal error moment otherwise. The steering law has smaller overall tracking errors and lower peak gimbal rates, and it achieves singularity escape faster than existing methods, as demonstrated analytically and using simulations.

LMI-Based Sliding Mode Control of an Underactuated Control Moment Gyroscope System

This paper introduces and evaluates a robust control algorithm based on sliding mode control theory, in which together with the use of the LMI methods the stabilization of an underactuated nonlinear system can be guaranteed. The obtained results are applied to a mechanical system which consists of two single gimbal control moment gyroscopes for triaxial attitude control of a gravity-gradient stabilized tethered satellite system. These objectives are investigated first using analytical methods and then verified by numerical simulations.

Integrated Gimbal Dynamics model for Precise Gimbal Rate Control in Single Gimbal-CMG to achieve High Accuracy Pointing

Modern Earth observation spacecrafts require high agility to maneuver with larger torque which eventually needs CMGs, as Reaction Wheels cannot meet the demand of such large torques. In order to obtain high-accuracy pointing control with CMG, extremely precise gimbal control is necessary. The current paper brings to light the degree of control precision achieved by gimbal control system with the high fidelity models of inaccuracies like Gimbal Friction, CMG Motor Ripple, structural compliance which hinder the level of accuracy obtainable from CMG attitude control. Proper compensation schemes based on the models help in facilitating an improved level of precision control with CMG. Simulations are carried out with periodic sinusoids as reference gimbal rate to 4 Single Gimbal Control Moment Gyros with roof-top configuration in MATLAB/SIMULINK.

Performance evaluation of robust attitude control system using control moment gyros for rapid multi-target observation

Since observation tasks of micro-satellite require rapid multi-target acquisition and high pointing accuracy, the single-gimbal control moment gyro (CMG) is considered as an ideal torque-generating actuator due to its practical performance for the satellite. This paper compares two useful robust attitude control algorithms (sliding mode control method and high order sliding mode control method). These control methods have improved the system's robustness and accuracy. The pseudo-inverse steering logic based on mixed two-norm and least-squares minimisation is chosen in this paper which can deal with both the internal singularity problem and momentum saturation singularities. This attitude control system is verified through numerical simulation. The results demonstrate the validity and feasibility of the proposed approach.

Attitude control of reentry vehicles in roll channel using single-gimbal control moment gyros and a reaction control system

A novel roll-channel attitude control scheme using a combination of single-gimbal control moment gyros and a reaction control system is proposed, providing sufficient control torque during the whol...

Rapid Singularity-Escape Steering Strategy for Single-Gimbal Control Moment Gyroscopes

To enable the quickest possible escape from an impassable singular surface, a rapid singularity-escape steering strategy is proposed. This steering strategy works when encountering an impassable singular surface. This strategy consists of three main steps. The first step is to determine the nearest escapable point, which is always on the edge of the impassable singular surface. The second step is to calculate the torque direction that is required to ensure that the angular momentum rapidly moves toward the nearest escapable point. The third step is to apply a steering law designed to function even on a singular surface. In addition, the gimbal rates calculated using this steering law can produce a torque along the required torque direction with the maximum capability of the single-gimbal control moment gyroscope system to ensure rapid escape from the singular surface. For the proposed steering strategy, only a small amount of data must be stored in advance. Finally, two sets of simulations are presented to verify that this steering strategy can drive the angular momentum to rapidly escape from a singular surface.

제어 모멘트 자이로스코프를 이용한 외바퀴 이동로봇의 균형 자세 제어

외바퀴 로봇 제어에 있어 필수적인 균형 안정화 제어를 위해 제어 모멘트 자이로스코프(CMG)를 이용할 수 있다. 단일 짐벌 CMG는 단순한 구조를 가지면서 외란에 대해 강력한 복원 토크를 로봇에게 전달할 수 있다. 그러나 CMG는 복원 토크 외에 원치 않는 방향의 토크도 발생시킨다. 원치 않는 방향 토크는 회전 자유도가 높은 외바퀴 로봇 시스템에서 불안정성 문제를 야기한다. 본 논문에서는 원치 않는 방향 토크를 제거하기 위해 CMG 가위쌍을 이용한 외바퀴 이동 로봇 제어 시스템을 제시한다. 외바퀴 로봇 동역학식에 있어서의 모델 오차에 강인한 특성을 갖는 LQR 제어 알고리즘을 설계하였다. 3D 비선형 동역학 컴퓨터 시뮬레이션을 통해 CMG 가위쌍과 LQR 제어 알고리즘을 갖는 외바퀴 로봇 제어 시스템을 검증하였다. The control moment gyroscope(CMG) can be used for essential balancing control of a one-wheeled mobile robot. A single-gimbal CMG has a simple structure and can supply strong restoring torque against external disturbances. However, the CMG generates unwanted directional torque also besides the restoring torque; the unwanted directional torque causes instability in the one-wheeled robot control system that has high rotational degrees of freedom. This study proposes a control system for a one-wheeled mobile robot by using a CMG scissored pair to eliminate the unwanted directional torque. The well-known LQR control algorithm is designed for robustness against modeling error in the dynamic motion equations of a one-wheeled robot. Computer simulations for 3D nonlinear dynamic equations are carried out to verify the proposed control system with the CMG scissored pair and the LQR control algorithms.

LQR/LQG attitude stabilization of an agile microsatellite with CMG

PurposeThe purpose of the paper is to design a new attitude stabilization system for a microsatellite based on single gimbal control moment gyro (SGCMG) in which the gimbal rates are selected as controller parameters.Design/methodology/approachIn the stability mode, linear quadratic regulator (LQR) and linear quadratic Gaussian (LQG) control strategies are presented with the gimbal rates as a controller parameters. Instead of developing a control torque to solve the attitude problem, the attitude controller is developed in terms of the control moment gyroscope gimbal angular velocities. Attitude control torques are generated by means of a four SGCMG pyramid cluster.FindingsNumerical simulation results are provided to show the efficiency of the proposed controllers. Simulation results show that this method could stabilize satellite from initial condition with large angles and with more accuracy in comparison with feedback quaternion and proportional-integral-derivative controllers. These results show the effect of filtering the noisy signal in the LQG controller. LQG in comparison to LQR is more realistic.Practical implicationsThe LQR method is more appropriate for the systems that have project models reasonably exact and ideal sensors/actuators. LQG is more realistic, and it can be used when not all of the states are available or when the system presents noises. LQR/LQG controller can be used in the stabilization mode of satellite attitude control.Originality/valueThe originality of this paper is designing a new attitude stabilization system for an agile microsatellite using LQR and LQG controllers.

Robust spacecraft attitude tracking control using hybrid actuators with uncertainties

The problem of spacecraft attitude tracking using hybrid actuators with uncertainties is addressed in this paper. A hybrid actuators configuration that combines reaction wheels for fine pointing and single gimbal control moment gyros for rapid maneuvering is employed for agile spacecraft. A robust control algorithm for the spacecraft attitude tracking problem when the torque axis direction and/or input scaling of the actuators are uncertain is developed. Furthermore, a torque allocation method is proposed for the hybrid actuator configuration to allow a smooth switch between single gimbal control moment gyros and reaction wheels. With this method, single gimbal control moment gyros are used for the phase of rapid maneuvering, while reaction wheels are used for the phase of fine pointing. Simulation results demonstrate the effectiveness of the proposed control scheme.

Optimization design steering law for VSCMGs with the function of attitude control and energy storage

Control Momentum Gyros (CMGs) have many advantages over other actuators for attitude control of a spacecraft. Compared with Single Gimbal Control Moment Gyroscopes (SGCMGs), the Variable Speed Control Moment Gyros (VSCMGs) can be easily implemented. The VSCMGs have great advantages in performing complex mission of attitude control and easing power shortage of the entire spacecraft. In this paper, the singularity avoidance characteristic of the steering law of Weighted Pseudo-inverse with Null Motion (WPINM) is firstly analyzed by the method of the inner product. A new steering law is designed based on optimization theory, which can satisfy the requirement of attitude control and energy storage. At last, the singular point can be avoided by the new design steering law based on the simulation result.

ピラミッド配置型CMGをもつ宇宙機の擬似スペクトル法による最適姿勢変更計画

A Control Moment Gyro (CMG) is an actuator suitable for agile spacecraft because it has large torque capability. However, CMG systems can fall into singular states where commanded torque can not be exactly generated and the spacecraft attitude control law becomes complicated. A control method which uses gimbal angle trajectories is effective for the singularity avoidance and the time optimization of the attitude change. In this study, focusing on the spacecraft equipped with four Single-Gimbal CMGs in a pyramid configuration, the procedure of time optimization using the Chebyshev-Pseudospectral method and a nonlinear optimization program is described. In addition, the tracking control method is investigated and the steering logic is demonstrated by conducting hardware experiments as well as numerical simulations.

Fault Tolerant Attitude Control for spacecraft with SGCMGs under actuator partial failure and actuator saturation

A Fault Tolerant Attitude Control algorithm for the spacecraft using Single Gimbal Control Moment Gyros (SGCMGs) as actuator is proposed. The controller is designed using the sliding mode control theory to control the gimbal rate directly and there is no singular point in the control algorithm, which means that we don't need to design the steering laws again and the singularity problems can be avoided. Also the gimbal rate saturation is considered when designing the control method. The adaptive control algorithm is used to estimate the disturbance and the boundary of the fault and saturation, which means that no prior information of the fault is needed. Although the controller is designed based on the SGCMGs, it can also be employed when reaction wheels work as the actuator of the spacecraft. Also the complete failure of several SGCMGs is allowed. It is proved based on the Lyapunov stability theorem that the designed control algorithm can achieve the attitude asymptotic stability both on the fault or fault-free condition. The simulation results show that the proposed method has a strong robustness.

The parameters optimisation design for variable speed control momentum gyroscopes

ABSTRACTControl momentum gyroscopes (CMGs) have many advantages over other actuators for the attitude control of a spacecraft. Compared with the single-gimbal control moment gyroscopes (SGCMGs), the mass and power of the flywheel of variable-speed control moment gyroscopes (VSCMGs) are greatly increased. In this paper, a new solving strategy of singularity problem is proposed, which concludes the exchangeable momentum and steering law, and the parameters of VSCMGs are designed based on the constraint of singular problem. The configuration characteristics of VSCMGs with the constraint of upper and lower bounds of the flywheel regulation speed are revealed. The steering characteristics of weighted pseudo-inverse with null motion (WPINM) are analysed, then the flywheel torque requirement of WPINM is evaluated based on the geometry theory. At last, the parameter design problem of VSCMGs is cast as multi-objectives and bi-level programming problem. The bi-level programming is transformed into a single-level programming problem by using of the Karush–Kuhn–Tucker condition. Finally, the intelligent algorithm of particle swarm optimisation is presented to solve the nonlinear multi-objective problem.

Composite Adaptive Control of Single Gimbal Control Moment Gyroscope Supported by Active Magnetic Bearings

AbstractIn this work, a control moment gyroscope (CMG) supported by active magnetic bearing (AMB) is considered with a gimbal angular movement. Gimbal angular movement in a CMG imposes extra load on magnetic bearings. A complete model of the CMG system with flywheel, AMBs, and gimbal dynamics is derived for control design. Lyapunov based composite adaptive output feedback control is proposed for fast uncertainty compensation in the CMG system, and some simulation results are presented. For a gimbal angular velocity input, a flywheel rotor magnetic bearing system is simulated at constant rotational speed of the flywheel rotor.

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.