Single Gimbal Control Moment Gyros Research Articles

ДОПОЛНИТЕЛЬНОЕ ВЫВЕДЕНИЕ И СБЛИЖЕНИЕ КОСМИЧЕСКОГО РОБОТА ДЛЯ ОБСЛУЖИВАНИЯ ГЕОСТАЦИОНАРНОГО СПУТНИКА

The problems of additional launching a space robot into a geostationary orbit and approaching a geostationary satellite for its maintenance are considered. The robot's attitude and orbit control system uses an electric propulsion unit, a propulsion system based on eight electric thermo-catalytic engines with pulse-width modulation of their thrust, and a gyro moment cluster based on four single-gimbal control moment gyroscopes (gyrodines). Numerical results are presented that demonstrate the effectiveness of the developed discrete guidance and control algorithms.

Motion control of a space robot at launching and approaching a geostationary satellite

The problems of putting a space robot into a geostationary orbit using a combined scheme and its approach to an information geostationary satellite are considered. When approaching, the robot’s attitude and orbit control system uses an electric propulsion unit, a propulsion system based on eight electro-catalytic reaction engines with pulse-width modulation of their thrust, and a gyroscopic moment cluster based on four single gimbal control moment gyroscopes (gyrodines). Numerical results are presented that demonstrate the effectiveness of the developed discrete guidance and control algorithms.

Manifold path selection steering law for pyramid-type single-gimbal control moment gyros

The properties of singularities for pyramid-type single-gimbal control moment gyro (SGCMG) configuration are investigated in this paper. Manifold theory is applied to the SGCMG system and singular surfaces are classified by passability and directionality. A terminal domain is introduced as a small angular momentum space wrapped by internal elliptic singular surfaces and intersected hyperbolic singular surfaces. The hyperbolic singular surfaces in a terminal domain can provide the SGCMG system with a chance to select a manifold path containing no internal elliptic singularity. Thereafter, a manifold path selection (MPS) steering law based on a modified gradient method is proposed, which can achieve internal elliptic singularity avoidance without introducing torque errors. Compared with the other two steering laws, the effectiveness of the proposed method is demonstrated using attitude maneuver examples.

Steering control law for double-gimbal scissored-pair CMG

Because control moment gyroscopes (CMGs) can generate a large torque compared to reaction wheels, they are used as actuators for attitude control of large spacecraft. However, when the number of Single-Gimbal CMG (SGCMG) units is five or less, there can be internal singularities that cannot generate torque around the desired direction. To construct a system that has no internal singularities, six or more SGCMGs are required, because an orthogonally arrayed, three scissored-pair CMG system has no internal singularities. Because CMG singularities are disruptive for attitude control, a great deal of effort has been devoted to overcoming the CMG singularity problem; the various designs include Variable-Speed CMGs (VSCMGs), Double-Gimbal CMGs (DGCMGs), and Double-Gimbal Variable-Speed CMGs (DGVSCMGs). However, these designs still have problems, such as a slow response to torque generation commands about the wheel axis in VSCMGs and DGVSCMGs, and difficulty in precise attitude tracking when perturbation torque is generated to avoid singularities. To overcome the problems of the traditional CMG configurations, this paper proposes a new CMG system configuration that we call the Double-Gimbal Scissored-pair CMG (DGSPCMG) system. Because the DGSPCMG system is a hybrid system combining a Scissored-Pair CMG and a DGCMG, the DGSPCMG system does not have internal singularities except at the origin and along the x-axis. Moreover, this system can recover from an internal singularity by null motion only, and from outer singularities (saturation singularities) by steering the scissored-pair gimbals only. Thus, generation of perturbation torque is unnecessary for recovering from singularities, and a precise attitude tracking maneuver can be more easily achieved. This paper presents a conceptual design of a DGSPCMG system and describes a steering control law for the proposed system. Furthermore, the validity of the proposed steering control law is demonstrated through numerical simulations and results of comparison experiments are shown to demonstrate the advantage of the DGSPCMG over a VSCMG.

Fault modeling of general momentum exchange devices in spacecraft attitude control systems

This paper investigates the mechanism of various faults in momentum exchange devices. These devices are modeled as a cascade electric motor (EM) - variable speed drive(VSD) system. Considering the mechanical part of the EM and the VSD system, potential faults are reviewed and summarized. Then, a general fault model in a cascade multiplicative structure is established for momentum exchange devices. Based on this general model, various fault scenarios can be simulated and tested, and the possible outputs affected by faults can be appropriately visualized. Specifically, six types of working condition are identified, and the corresponding fault models are constructed. Using these fault models, the control responses using reaction wheels and single gimbal control moment gyros under various fault conditions can be demonstrated. The simulation results show the severities of the faults and demonstrate that the additive fault is more serious than the multiplicative fault from the viewpoint of control accuracy. Finally, existing fault-tolerant control strategies are briefly summarized and potential approaches including both passive and active ones accommodating gimbal fault of single gimbal control moment gyro are demonstrated.

Integration planning of gimbal angle and attitude motion for zero propellant maneuver under attitude and control moment gyroscope constraints

Zero propellant maneuver is an advanced concept of large spacecraft attitude control that has recently been applied to International Space Station. The objective of this paper is the zero propellant maneuver path planning of space station under attitude and control moment gyroscope constraints. First, a multi-constraint model of zero propellant maneuver with single gimbal control moment gyroscopes is established. Then, an integrated planning algorithm of gimbal angle and attitude motion is proposed: Local Control Differential Evolution. The algorithm can simultaneously handle attitude constraints and control moment gyroscope constraints to obtain an attitude path that satisfies the attitude constraints and a gimbal angle path that is far from singularity and saturation. In addition, the algorithm combines the local control algorithm with the global differential evolution algorithm. The local control algorithm based on the potential function idea can better deal with local attitude obstacle constraints, and the global optimization algorithm based on the improved differential evolution algorithm can perform global gimbal angle optimization. Finally, simulation results show that the method is effective in dealing with both attitude and control moment gyroscope constraints.

Calibration, Compensation and Accuracy Analysis of Circular Grating Used in Single Gimbal Control Moment Gyroscope.

The accuracy of the circular grating is the key point for control precision of the single gimbal control moment gyroscope servo system used in civilian micro-agile satellites. Instead of using the multi reading heads to eliminate eccentricity errors, an algorithm compensation method based on a calibration experiment using a single reading head was proposed to realize a low-cost and high accuracy angular position measurement. Moreover, the traditional hardware compensation method using double reading heads was also developed for comparison. Firstly, the single gimbal control moment gyroscope system of satellites was introduced. Then, the errors caused by the installation of the reading head were studied and the mathematic models of these errors were developed. In order to construct the compensation function, a calibration experiment using the autocollimator and 24-sided prism was performed. Comparison of angle error compensation using the algorithm and hardware method was presented, and results showed that the algorithm compensation method proposed by this paper achieved the same accuracy level as the hardware method. Finally, the proposed method was further verified through a control system simulation.

Controlling a Satellite using Single-Gimbal Control Moment Gyroscope During Their Spinning and Braking

The capabilities of using single-gimbal control moment gyroscopes (CMGs) for the attitude control of Earth remote sensing (ERS) satellites are studied. The situation of the incomplete spinning of CMGs used for controlling the angular motion of the satellite when these gyros have a different angular momentum is considered. Control algorithms that can be applied in this situation are proposed, and it is shown that they can be used to stabilize the satellite. Using simulation, it is shown that a satellite’s angular motion can be controlled by CMGs having different angular momenta.

Fault Modeling, Estimation, and Fault-Tolerant Steering Logic Design for Single-Gimbal Control Moment Gyro

This brief addresses the single-gimbal control moment gyro (SGCMG) fault modeling, estimation, and tolerant-control steering logic design problem, aiming at enhancing the reliability and safety of spacecraft attitude control systems. The SGCMG is modeled as a two-loop system, including a wheel speed control loop and a gimbal rate control loop. Each loop contains an electrical motor (EM) and its corresponding variable speed drive (VSD), which may suffer from faults. By analyzing and modeling potential faults of the EM-VSD system, the SGCMG fault model is further developed. Then, a local adaptive fault estimator is proposed to reconstruct the total time-varying fault effects of each SGCMG. It is proven that the gimbal angle estimation error and fault estimation error converge to small compact sets containing zero. Moreover, leveraging estimated fault effects, a fault-tolerant steering logic is further developed to allocate the commanded attitude control torque properly such that the gimbal rate constraints are satisfied, and fault effects are compensated. To verify the proposed fault estimator and fault-tolerant steering logic, numerical simulations are carried out on an SGCMG-actuated spacecraft.

Two Parallel Single-Gimbal Control Moment Gyros Actuated Spacecraft Attitude Maneuver

This correspondence investigates the underactuated spacecraft attitude maneuver problem using two parallel single-gimbal control moment gyros (SGCMGs). According to the configuration of the SGCMGs, the principle axes of the spacecraft are divided into two parts, namely, the axes with and without direct control input. Based on this division, a two-level control strategy, a low-level tracking control part to track the desired angular velocity error about the axes with direct control input and a high-level sliding mode control part to stabilize the angular velocity error, is developed. Four numerical scenarios are conducted to verify the proposed control logic. Simulation results show that the target attitude is a global equilibrium and any attitude can be reached when the whole system is feasible. If the controllability is not satisfied, the spacecraft rotates in the adjacent region around the desired attitude.

A Singularity-free Steering Law of Roof Array of Control Moment Gyros for Agile Spacecraft Maneuver

In this paper, a singularity-free steering law for single gimbal control moment gyros (CMGs) is addressed for agile spacecraft. The geometrical array considered particularly in this work is a roof array due to the simplicity of singularity envelope. A feasible angular momentum chart which can provide a singularity-free bound is employed. The chart allows a guaranteed maximum torque output and angular momentum at any time without concerning the geometrical singularity of the array. Furthermore, a new deterministic allocation algorithm, called half-leading steering logic, of gimbal angular rates, is also suggested instead of the well-known pseudo-inverse technique to meet control torque commands required and to keep away from the singularity. It is noted that a momentum vector recovery to the initial direction is also an important task for the CMG array to overcome the singularity and for the reliable operation of CMGs. An optimization technique is addressed to restore the gimbal vectors back to their original angular position after the attitude reorientation mission. The techniques proposed are demonstrated using illustrative numerical simulations.

Coupled Dynamic Modeling and Analysis of the Single Gimbal Control Moment Gyroscope Driven by Ultrasonic Motor

A control moment gyroscope (CMG) is a key actuator for spacecraft's attitude and stability control. But there exist micro-vibrations from high-speed flywheel, which will affect the performance of the spacecraft greatly. Due to the unbalanced mass and the supporting structure, the high-speed rotating flywheel could generate disturbance torque, which will be passed to the gimbal to deteriorate the gimbal servo system. At the same time, the rotation of the gimbal will increase the disturbance torque for gyroscopic effect. According · to the bearing theory, the stiffness of the bearing is affected by the load that applied on it, which results the influence on the flywheel vibration and the generated disturbance torque. This means that there is a coupling effect in the CMG. In this article, we focused on this coupling relationship between the flywheel vibration and the gimbal rotation in a single gimbal control moment gyroscope (SGCMG) system. Firstly, a vibration model of the flywheel with variable stiffness supporting is established. And the rotation model of the gimbal is also developed. The flywheel model and the gimbal model are coupled with each other through the variable stiffness supporting and gyroscope effect. Based on the numerical simulations the interactions among the bearing stiffness, the flywheel vibration and the gimbal rotation are analyzed. Finally, experiments are carried out on the prototype. The experimental results have verified the theoretical analysis and the simulations, and which would support the design of high-performance control system.

Dynamic Near-Optimal Control Allocation for Spacecraft Attitude Control Using a Hybrid Configuration of Actuators

This paper proposes a novel dynamic near-optimal control allocation scheme with combination of a saturated baseline controller for spacecraft attitude control using single-gimbal control moment gyros (CMGs) and reaction wheels. First, a saturated controller is proposed to stabilize the nominal system in the presence of actuation mismatch. Aided by a state-dependent variable, a dynamic control allocator is then proposed that allows for smooth switching between two actuation sets. Unlike the previous static constraint optimization formulations, the control allocation augments its performance function with penalty terms in order to enforce individual input constraints and configuration singularity avoidance. Moreover, this dynamic control allocation is implemented with an online update law, which has a modest computational complexity compared to its numerical optimization counterpart. The closed-loop boundedness is guaranteed by a constructive Lyapunov-design method. Simulation results demonstrate that during the attitude maneuvers, the input saturation constraint and the active avoidance of CMG singularities are enforced with a relatively small computational cost.

Adaptive Spacecraft Attitude Control Using Single-Gimbal Control Moment Gyroscopes Without Singularity Avoidance

This paper applies retrospective cost adaptive control (RCAC) to spacecraft attitude control with a rotation-matrix attitude parameterization using constant-speed single-gimbal control moment gyroscopes. Unlike control laws that use torque-steering laws to synthesize torque requests while avoiding gimbal singularities, the adaptive control law requests the rate of each gimbal. Because no torque request is provided, there is no need to invert the mapping from the gimbal rates to the control torque, and thus no attempt is made to avoid gimbal singularities. The RCAC implementation is based on a target model involving a single Markov parameter corresponding to the initial gimbal configuration. The parameters and weights for RCAC are based on nominal-model tuning, which uses no explicit knowledge of the nonlinear equations of motion. This paper investigates the robustness of RCAC to off-nominal conditions of commands, noise, and unknown bus inertia; and it examines the performance of RCAC in the case where an approximately singular gimbal configuration occurs during attitude command, following as well as the case of an initial gimbal-lock singularity. The performance of the adaptive controller in the presence of sensor/actuator misalignment is also investigated.

Accurate Control for Gimbal System of Single Gimbal Control Moment Gyro Based on Nonlinear Cascade Extended State Observer

The nonlinear friction, unmodeled disturbance and coupling torque caused by the movement of satellite are the main factors limiting the angular speed accuracy in gimbal system of the single gimbal control moment gyro (SGCMG). Consequently, a high-precision servo control system based on the nonlinear cascade extended state observer (NCESO) is established in this paper in order to reduce the influence of those disturbances and improve the output angular velocity accuracy of the gimbal system. The simulation results confirmed the feasibility and effectiveness of the proposed method.

A novel single-gimbal control moment gyroscope driven by an ultrasonic motor

This article presents a structure-compacted single-gimbal control moment gyroscope, which is directly driven by an ultrasonic motor. The momentum wheel and the ultrasonic motor are designed and opt...

Attitude Stabilization Using Two Parallel Single-Gimbal Control Moment Gyroscopes

This paper investigates the underactuated attitude stabilization problem using two parallel single-gimbal control moment gyroscopes (SGCMGs). Different from most existing underactuated control techniques requiring the zero total angular momentum assumption, only the controllability of the whole control moment gyroscope (CMG)–spacecraft system, which means the total angular momentum of the spacecraft with CMG array within the momentum envelope of the CMG array, is required in this paper. To achieve the underactuated attitude stabilization, a new controller consisting of two parts, that is, a higher level sliding mode control part to stabilize the angular velocity about the underactuated axis in finite time and a tracking control part to track desired angular velocities that are used to stabilize the remaining states, is developed. This proposed novel control logic achieves attitude stabilization when the initial total angular momentum of the CMG-spacecraft is not zero. Simulations show that the attitude of a microsatellite can be stabilized precisely within acceptable time using the proposed control law and steering law when the controllability constraint is satisfied. When the initial total momentum of the spacecraft base and the CMG array exceeds the momentum envelope of the CMG array, simulation results demonstrate that the attitude is controlled to be a periodic oscillation in the vicinity of the equilibrium, at the same angular momentum level determined by the initial condition.

Calculation of Program Control Not Generating Singularities in Gyrosystems

A new approach to calculating the program controls of the spacecraft (SC) attitude by single-gimbal control moment gyros (gyroscopes in English terminology or gyrodynes in Russian terminology) is described in details. The novelty of the proposed method of calculating program controls is the virtual kinematic configuration of the actuator gyrosystem and the use of the angular momentum of the SC as a state variable when describing its dynamics. The formulation of the problem of calculating the control laws, based on these innovations, made it possible to directly use the total angular momentum of all the rotors of the gyrosystem in their motion relative to the main body of the SC, rather than its derivative, as a working tool for controlling the SC, and to accept the laws of the precessions of the gyro units, rather than the velocities of these precessions. A new approach to solving the problem of reorientation enables us to obtain control laws without such special (singular) positions of the gyro units in which the execution of the calculated laws is interrupted. This feature solves the well-known singularity problem of an actuator gyrosystem consisting of gyrodynes, and suggests that the presence of a singularity problem in the process of executing the calculated laws should be due only to their calculation method rather than due to certain specific features of the gyrosystem itself. The new method of calculating the control presented in this paper uses the structure of the space trajectory given a priori and the law of the motion along this trajectory is calculated in the process of forming the control. All the calculations are carried out on the standard onboard digital computer.

Vector Control-Based Singularity Avoidance/Escape Steering Law for Single Gimbal Control Moment Gyros

The single-gimbal control moment gyros (SGCMGs) steering law has been a standing topic in the field of spacecraft attitude control for several decades. A practical steering law should meet the following requirements simultaneously: powerful singularity avoidance ability, high precision torque output ability and fast singularity escape ability. Moreover, the angular velocity commands generated by the steering law should not jitter sharply. In this paper, a vector control-based singularity avoidance and escape steering law for SGCMGs is proposed to satisfy these goals. In addition, a system angular momentum state evaluation function for command torque is defined for the first time, which can be used to effectively evaluate the remaining angular momentum resources for the command torque. We demonstrate the effectiveness and superiority of the proposed steering law with detailed comparisons to existing efforts.

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.