Control Moment Gyros Research Articles

Simulation of satellite attitude control using Single Gimbal Control Moment Gyro (SGCMG) system

Control Moment Gyro (CMG) is a type Attitude Control System (ACS), a system used to change the attitude of satellite along its orbit. CMG generates required gyroscopic torque by spinning a number of rotors, and directs the torque by changing the orientation of those rotors using gimbals. CMG is capable of generating a large amount of torque with relatively low power which makes it suitable for high agility mission requiring 1-10 deg/s slew rate. A major problem encountered with the use of CMG in practice is the presence of singularity, a state in which, the CMG is unable to generate torque along certain direction. Various steering algorithms have been developed to overcome the singularity problems. In this paper, the attitude control performance of Single Gimbal Control Moment Gyro (SGCMG) system is investigated. Steering algorithm also implemented to overcome singularity problem that might be encountered. The results show that SGCMG capable of generating torque required for agile attitude maneuver in the presence of singularity.

Gain Scheduling Controller Synthesis for Control Moment Gyroscope Using Improved Approximation

This paper presents gain scheduling (GS) control of a variable speed control moment gyroscope (VSCMG) based on sum of squares (SOS). Nonlinear motion equations of the VSCMG are complicated because ...

MR Damper-Based Vibration Suppression Method for Control Moment Gyroscope

To restrain the interference of micro-vibration caused by Control Moment Gyroscope, a new control method based on Magnetorheological damper was proposed in this paper. A mechanical model based on the structure of the presented design was built, and the semi-active control algorithm of damping force was proposed for the designed Magnetorheological damper. The magnetic flux density and other magnetic field parameters were considered and analyzed in Maxwell, and also the related hardware circuit which implements the control algorithm was prepared to test the presented design and algorithm. The results of simulation and experiments show that the presented Magnetorheological damper model and semi-active control algorithm can complete the requirements, and the vibration suppression method is efficient for Control Moment Gyroscope.

Rapid SGCMGs Singularity-Escape Steering Law in Gimbal Angle Space

The singular surfaces of pyramid-type single-gimbal control moment gyroscope (SGCMG) configuration are classified and visualized in the angular momentum space. Continuous impassable and passable singular surfaces in the gimbal angle space is obtained by using the Binet–Cauchy theory, and the relationship between the two spaces is subsequently analyzed. Thereafter, a rapid singularity-escape steering law in the gimbal angle space is proposed to drive SGCMGs to escape from an impassable singular surface. Simulation results demonstrate the effectiveness of the proposed steering law.

Spacecraft attitude control and vibration suppression integration based on single gimbal magnetically suspended control moment gyroscope pyramid configuration

For the sake of improving the agility and super-static performance of spacecraft, this paper puts forward an idea for using single gimbal magnetically suspended control moment gyroscope pyramid configuration to realize dual control of attitude maneuver and micro-vibration suppression of spacecraft, in which gyro gimbal rotation is used to realize fast attitude maneuver and magnetic suspension rotor deflection is used to realize high-precision micro-vibration suppression of spacecraft; the switching design of spacecraft attitude/vibration controller realizes the coordinated operation of gyro gimbal and magnetic suspension motor, showing the control advantage of dual actuators. This strategy not only speeds up the attitude maneuver process of spacecraft, improving the dynamic response, but also reduces the attitude stabilization adjustment time as well as improves the stabilization precision, ensuring the fast vibration suppression after attitude maneuver. In addition, this method has strong robustness ensuring the smooth implementation of spacecraft attitude control and vibration suppression integration in the case of parameter change. The simulation results show the effectiveness and superiority of this strategy.

Attitude and vibration control with double-gimbal variable-speed control moment gyros

The attitude and vibration control of a flexible spacecraft with two parallel double-gimbal variable-speed control moment gyros (DGVSCMGs) is considered. The coupled nonlinear equations of motion create a complex challenge in a pointing control development. First a Gain-Scheduled (GS) controller for a 3-axis attitude control is designed by the post-guaranteed linear matrix inequalities (LMIs) method with H2/H∞ constraints. Next an H2/H∞ controller for vibration control is designed to attain both attitude and vibration control at the same time. The two controllers are combined using the dynamic inversion (DI) technique. Finally, the effectiveness of the proposed combined controller is demonstrated through a numerical example.

Dynamics and Control of Spacecraft Manipulators with Thrusters and Momentum Exchange Devices

The space sector is currently undergoing a push from the industry, several governments, and academia to enable routine satellite servicing in orbit. Among the many challenges, the complex dynamic interactions between the satellite base and the robotic arm are of primary concern. Although some missions may rely on the grappling of the host satellite, which would simplify servicing by virtue of fixing the relative kinematics between the two satellites, future space missions may also require a single point of contact between two satellites. Thus, precise end-effector control of the maneuvering satellite and its base is required. Although effective control tools exist in the fields of spacecraft pose control and robotics, simple methods to combine them are lacking in the space robotic servicing literature, which often requires complex derivations and can be subject to constraints, as is the case with a fixed center of mass or a zero angular momentum system. In this paper, the well-known recursive Newton–Euler approach is combined with appropriate spacecraft control algorithms to perform coordinated control of a spacecraft manipulator system. The interface between the two models is discussed (the base and the manipulator), and several realistic actuation models are incorporated, including thrusters and momentum exchange devices. In addition, a novel actuation approach through a cluster of four variable-speed control moment gyroscopes is proposed. The system is simulated and the proposed controllers implemented and tested according to the different actuation modes of the spacecraft. The simulation results are discussed, and the performance during each scenario is analyzed.

Comparing fluid ring and CMG servomechanisms for active control of rigid satellites

Purpose This paper aims to describe a novel type of attitude control system (ACS) in different configurations. This servomechanism is compared with control moment gyro (CMG) in significant parameters of performance for ACS of rigid satellite. Design/methodology/approach This new actuator is the fluid containing one or more rings and fluid flow is supplied by pump. The required torque control is obtained by managing fluid angular velocity. The cube-shaped satellite with three rings of fluid in the principle axes is considered for modeling. The satellite is considered rigid and nonlinear dynamics equation is used for it. In addition, the failure of the pyramid-shaped satellite with an additional ring fluid is discussed. Findings The controller model for four fluid rings has more complexity than for three fluid rings. The simulation results illustrated that four fluid rings need less energy for stabilization than three fluid rings. The performance of this type of actuator is compared with CMG. At last, it is demonstrated that performance parameters are improved with fluid ring actuator. Research limitations/implications Fluid ring actuator can be affected by environmental pressure and temperature. Therefore, freezing and boiling temperature of the fluid should be considered in system designation. Practical implications Fluid ring servomechanism can be used as ACS in rigid satellites. This actuator is compared by CMG, the prevalent actuator. It has less displacement attitude maneuver. Originality/value The results provide the feasibility and advantages of using fluid rings as satellite ACS. The quaternion error controller is used for this model to enhance its performance.

Development of a Magnetorheological Damper of the Micro-vibration Using Fuzzy PID Algorithm

Control moment gyroscope (CMG) is an ideal device for satellite attitude transformation, which inevitably has micro-vibration in that process, and it will seriously affect the high precision imaging of the satellite. To restrain the interference with micro-vibration caused by CMG, a magnetorheological (MR) damper and its control method are designed in this study. Besides, the structure, the dynamic model, and the fuzzy PID algorithm of the MR damper are proposed. The magnetic circuit structure is designed according to the requirements of MR dampers for magnetic field, the finite element analysis of magnetic force line and magnetic induction intensity is completed in Maxwell, and the simulation shows that the designed magnetic circuit meets the requirements. The simulation test is carried out by Simulink under the stimulation of vibration source. The vibration suppression effect of the MR damper is tested on the vibration test platform, from which we know the designed MR damper can effectively control the micro-vibration suppression.

Robust Attitude Control Using a Double-Gimbal Variable-Speed Control Moment Gyroscope

This paper derives a linear parameter-varying (LPV) model for three-axis attitude control of a spacecraft with a single double-gimbal variable-speed control moment gyroscope (DGVSCMG) and magnetic torquers (MTQs) and develops a singularity avoidance steering law. The LPV control theory provides an optimal gain-scheduled (GS) controller while considering both control performance and robustness. However, in the spacecraft attitude control problem, it is impossible to design a GS controller due to excesses of the number of parameters in most mission scenarios. To avoid this difficulty, this paper designs two types of easy-to-use LPV models for adapting an LPV control theory. The first model is developed by linearization of the kinematics around the equilibrium point of the target attitude. The second one is developed by introducing a virtual state variable together with a parameter-dependent coordinate transformation. Next, a GS controller is designed by using linear matrix inequalities with regional pole placement constraints. Besides, the singularity avoidance steering law of a DGVSCMG by using MTQs is proposed. The applicability is demonstrated through numerical simulations of the proposed methods.

Experimental Design and Analysis of a Gyroelastic Beam

Abstract Gyroscopic systems and their properties have been extensively studied as Angular Momentum Devices (AMD), Control Moment Gyros (CMG) or Gyroscopes for various applications such as structure control, stability or energy storage. However, most of the works that have been done are theoretical and do not present experimental implementation. In this work we performed an experimental study of a gyroscope beam system (gyroelastic beam) focused systems on the deflection of cantilever beams or the control of flexural stresses. We first used a simple two-degree of freedom model to better understand the terms governing the design, construction and experimental evaluation of gyroelastic beam systems. We then performed experimental tests at different velocities of the gyroscopic actuator and measured the deflection of the system. The results showed that it is possible to have control of the deflection and the bending forces for this type of configurations which can be exported to helicopter blades or wind turbine blades.

Adaptive Singularity-Free Control Moment Gyroscopes

Design considerations of agile, precise, and reliable attitude control for a class of small spacecraft and satellites using adaptive singularity-free control moment gyroscopes (ASCMG) are presented. An ASCMG differs from that of a conventional control moment gyroscopes (CMG) because it is intrinsically free from kinematic singularities and so does not require a separate singularity avoidance control scheme. Furthermore, ASCMGs are adaptive to the asymmetries in the structural members (gimbal and rotor) as well as misalignments between the center of mass of the gimbal and rotors. Moreover, ASCMG clusters are highly redundant to failure and can function as variable and constant-speed CMGs without encountering singularities. A generalized multibody dynamics model of the spacecraft–ASCMG system is derived using the variational principles of mechanics, relaxing the standard set of simplifying assumptions made in prior literature on CMG. The dynamics model so obtained shows the complex nonlinear coupling between the internal degrees of freedom associated with an ASCMG and the spacecraft attitude motion. The general dynamics model is then extended to include the effects of multiple ASCMG, called the ASCMG cluster, and the sufficient conditions for nonsingular cluster configurations are obtained. The adverse effects of the simplifying assumptions that lead to the intricate design of the conventional CMG, and how they lead to singularities, become apparent in this development. A bare-minimum hardware prototype of an ASCMG using low-cost commercial off-the-shelf components is developed to show the design simplicity and scalability. A geometric variational integration scheme is obtained for this multibody spacecraft–ASCMG system for numerical and embedded implementation. Attitude pointing control of a CubeSat with three ASCMGs in the absence of external torques is numerically simulated to demonstrate the singularity-free characteristics and redundancy of the ASCMG cluster.

Envelope oriented singularity robust steering law of control moment gyros for spacecraft attitude maneuver

The problem of steering pyramid control moment gyro (CMG) cluster for fast spacecraft attitude maneuver along eigenaxis is investigated. A novel steering law is proposed to continuously attempt to reduce the difference between the current gimbal angle and the desired one corresponding to the angular momentum envelop of the CMG cluster. The proposed steering law can be decomposed into two parts: the first one is a singularity robust term to keep maneuverability and produce control torque, and the other is a null motion term to rearrange the gimbal angles toward momentum envelope. By involving this steering law, it is expected to possess both rapid angular momentum exchange and singularity avoidance ability. In addition, by introducing a new limit vector on attitude error, classical cascade-saturation control algorithm is revised to guarantee spacecraft eigenaxis rotation. Both open-loop steering law test and closed-loop attitude maneuver simulations are performed to evaluate the efficacy of the proposed methods.

Thermal Vacuum and Swivel Table Tests of a CMG and Fault Mechanism Analysis

AbstractThermal vacuum and swivel table tests of a control moment gyroscope (CMG) are designed and the start-up hesitation and rotation break of the CMG are analyzed. In order to study the fault me...

Spacecraft angular velocity trajectory planning for SGCMG singularity avoidance

A trajectory planning method for angular velocity of spacecraft is developed to avoid the impassable singular states for singular gimbal control moment gyroscope (SGCMG) systems in this paper. A new set of attitude parameters, named σ-parameters, is first developed. Based on the properties of σ-parameters, two approximate decoupled rotations are presented. To achieve a rapid attitude maneuver, both of the decoupled motions are designed as simple bang-off-bang type maneuvers. Then, a type of SGCMG singularity-free angular velocity trajectory on the conic surface is developed. Thereafter, an attitude controller based on σ-parameters is developed to track the reference trajectory. To avoid the impassable singular state, suitable axes of the approximate decoupled two rotations are chosen to achieve the fastest maneuver under the condition that the minimum distance from the angular momentum trajectory to the impassable surface is greater than a safety distance. Finally, simulations are performed to verify the effectiveness of the proposed SGCMG singularity avoidance method.

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.

Dynamics of flexible multibody systems with variable-speed control moment gyroscopes

This paper presents a generic global matrix formulation for the dynamics of flexible multibody systems with variable-speed control moment gyroscopes (VSCMGs). The flexible bodies are assumed to exhibit only small deformation, and they are connected in a tree topology by hinges permitting large rotation and translation. A cluster of VSCMGs is mounted on each body for actuation; it is assumed that the VSCMGs are statically and dynamically balanced, and their rotors are axisymmetric. A minimum set of dynamic equations are derived systematically via a mixed use of Kane's method and Newton–Euler equations. The parameters of each flexible body are augmented to take into account the inertias of the attached VSCMGs. Moreover, a skew-symmetric gyroscopic matrix and three control-input-mapping matrices are defined to represent the passive and the active gyroscopic torques of the VSCMGs in a global matrix manner. Three examples are given to show the usefulness, versatility, and correctness of the proposed formulation. As an additional contribution, also presented are linear dynamic equations for a spacecraft with flexible appendages and embedded VSCMGs.

Indirect Measurement of Rotor Dynamic Imbalance for Control Moment Gyroscopes via Gimbal Disturbance Observer.

The high-precision speed control of gimbal servo systems is the key to generating high-precision torque for control moment gyroscopes (CMGs) in spacecrafts. However, the control performance of gimbal servo systems may be degraded significantly by disturbances, especially a dynamic imbalance disturbance with the same frequency as the high-speed rotor. For assembled CMGs, it is very difficult to measure the rotor imbalance directly by using a dynamic balancing machine. In this paper, a gimbal disturbance observer is proposed to estimate the dynamic imbalance of the rotor assembled in the CMG. First, a third-order dynamical system is established to describe the disturbance dynamics of the gimbal servo system, in which the rotor dynamic imbalance torque along the gimbal axis and the other disturbances are modeled to be periodic and bounded, respectively. Then, the gimbal disturbance observer is designed for the third-order dynamical system by using the total disturbance as a virtual measurement. Since the virtual measurement is derived from the inverse dynamics of the gimbal servo system, the information of the rotor dynamic imbalance can be obtained indirectly only using the measurements of gimbal speed and three-phase currents. Semi-physical experimental results demonstrate the effectiveness of the observer by using a CMG simulator.

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.

Steering law of control moment gyros using artificial potential function approach

A Control Moment Gyro (CMG) cluster for an agile spacecraft usually suffers from a singularity problem where it does not meet a desired torque. To solve the problem, a proposed steering law consists of SR (singularity robustness) inverse and SR null motion to compensate each other. The SR null motion solves the singularity problem that the SR inversestays in the singularities. Especially, an APF (artificial potential function) is included in the SR null motion to avoid internal singularities and to reach external singularity simultaneously. The APF newly considers the distance between the current gimbal angle and the gimbal angle corresponding to all singularities. All the combinations of singular gimbal angles are regarded as a target and obstacles of the potential function. After a spacecraft maneuver, an initial gimbal angle is regarded as the target to secure the repeatability of next maneuver. When avoiding or escaping the obstacles corresponding to the unwanted singular gimbal angles, the proposed steering law rapidly changes the gimbal angle by taking torque error. To overcome the local minima problem which is generally a serious drawback in using the potential function, an algorithm for changing parameters of the potential function are proposed in the steering law. To avoid the internal singularity, moreover, the present study introduces a configuration change of the CMG cluster. The proposed steering law is mathematicallyanalyzed and verified through numerical simulations. It shows that the CMG cluster can avoid an internal singularity rapidly, resulting in faster maneuver time of the spacecraft.