Variable Speed Control Moment Gyroscopes Research Articles

Satellite Attitude Control Using Faulty Double Gimbal Variable Speed Control Moment Gyroscope

A rigid satellite attitude control requires stable finite-time attitude convergence in the presence of rotation unwinding, external disturbances, and actuator faults. To achieve this, a new nonsingular fast fixed-time sliding mode controller is proposed to ensure finite-time convergence independent of the initial conditions of the system. Rotation unwinding is addressed using the body and shadow pair of the Modified Rodrigues Parameters (MRPs). Convergence behavior of the states errors in the neighborhood of the MRPs switching surface is also addressed. Attitude control is achieved using a double-gimbal variable-speed control moment gyro (DGVSCMG). For the first time, a DGVSCMG having all possible electrical and mechanical faults is considered for control design. A novel nonsingular fast fixed-time anti-unwinding fault-tolerant sliding control using a new sliding surface is proposed. This eliminates switching of the sliding surfaces and minimizes control chattering. Four new propositions are proposed and proved to establish fast fixed-time global stability of the system for tracking maneuver in fault and fault-free conditions with anti-unwinding. Simulation results are presented and compared with existing fixed-time sliding control approaches. The results show superiority of the proposed anti-unwinding fault-tolerant fast fixed-time control for the tracking maneuver in terms of convergence time, energy efficiency, and fault tolerance.

Satellite Attitude Control Using Double-Gimbal Variable-Speed Control Moment Gyroscope: Single-Loop Control Formulation

A single-loop control architecture is proposed to achieve singularity-free attitude control of satellites actuated using a double-gimbal variable-speed control moment gyroscope (DGVSCMG). Satellite and DGVSCMG combined rotational dynamics is modeled in the framework of geometric mechanics. It is shown that the combined attitude dynamics is in control-affine form when the motor torques of the DGVSCMG are taken as control inputs. A single-loop hybrid robust nonsingular fast finite-time sliding mode control (NFFTSMC) is designed to ensure an unwinding-free attitude maneuver. In the proposed single-loop formulation, the respective motor torques of the DGVSCMG are computed directly using only one NFFTSMC without requiring the steering law, resulting in mathematical singularity-free attitude control. A novel sliding surface is also proposed to ensure that the rotor angular speed converges to its nominal value after the maneuver. This eliminates the need of repeated desaturation of the rotor spin rate, unlike all the steering-law-based control architecture. Unwinding-free global stability of the system using the proposed hybrid NFFTSMC is proved for the sliding and reaching phases. Simulation results are presented to substantiate the claim made, assuming the rigid satellite to be equipped with only one DGVSCMG.

Control Moment Gyro Actuator for a Guided Projectile

This paper investigates the suitability of using a gimbaled rotor actuator for trajectory control of a projectile. In this novel concept, a single-gimbal variable-speed control moment gyro is used as the sole control actuation system, allowing actuation in two orthogonal directions and two-dimensional control over the projectile’s flight path without any moving aerodynamic surfaces. A complete nonlinear model of the eight-degree-of-freedom rotational and translational flight mechanics is developed, as well as an accurate aerodynamic model for short-range trajectories. Linear models are derived for control design, and controllers are synthesized along with a steering logic to achieve control of the projectile’s roll and sideslip angles. Successful tracking of both angles is demonstrated, and a large course deviation is achieved, showing significant maneuverability and proving the viability of the concept.

Singularity avoidance controller design for spacecraft attitude control using double-gimbal variable-speed control moment gyro

A sub-optimal singularity avoidance large angle rest-to-rest attitude maneuver control of a rigid spacecraft actuated using a double-gimbal variable-speed control moment gyro (DGVSCMG) is proposed for avoiding the control torque saturation and the gimbal lock singularity. To achieve this objective, a modified model predictive static programming (MPSP) algorithm subject to control and state constraints is proposed and developed. A cuboid rigid spacecraft equipped with a single DGVSCMG device for the attitude control is considered to validate the proposed control algorithm. A new MPSP based control architecture for the attitude control of a spacecraft using a DGVSCMG is developed, wherein the desired gimbal angle rates and rotor spin acceleration are taken as the control input and computed directly using the MPSP algorithm without requiring the steering law. The control law ensures attitude stabilization of the spacecraft-DGVSCMG system while successfully avoiding the control input saturation and the gimbal lock singularity of the DGVSCMG, thereby enabling large angle attitude maneuvers. Multiple test cases of rest-to-rest attitude maneuvers are simulated to show the efficacy of the proposed control.

Optimizing Designed Variable Speed Control Moment Gyroscopes with Variable Skew Angle

Optimizing Designed Variable Speed Control Moment Gyroscopes with Variable Skew Angle

Satellite Attitude Control Using Double-Gimbal Variable-Speed Control Moment Gyro with Unbalanced Rotor

Attitude dynamics of a rigid satellite actuated using a double-gimbal variable-speed control moment gyro (DGVSCMG) with an unbalanced rotor is derived in the framework of geometric mechanics. The proposed formulation accounts for dynamics of the gimbal motors and the rotor motor for finding the required motor torque to actuate the satellite along with the DGVSCMG for achieving high-precision attitude control. The satellite attitude control is accomplished using a proposed cascaded adaptive fixed-time sliding mode control to ensure bounded finite-time convergence. A sliding manifold is also designed to ensure convergence of gimbals angular rates to the desired values. Actuator saturation, system uncertainties such as intrinsic disturbance torques due to the gimbals and rotor bearing friction, extrinsic disturbances due to the environmental factors, and uncertainty in inertia of the satellite bus are accounted for designing the controller. Lyapunov stability analysis is carried out to prove bounded finite-time stability of the proposed system. Simulation results are presented to substantiate the claim made assuming the rigid satellite to be equipped with only one DGVSCMG.

Unwinding-Free Fast Finite-Time Sliding Mode Satellite Attitude Tracking Control

A double-gimbal variable-speed control moment gyro (DGVSCMG) is considered for attitude control of a rigid satellite for track-to-track maneuver. Satellite attitude tracking control involves precision and time limit. In addition, satellite attitude control also faces rotation kinematic singularity, rotation unwinding, and control singularity associated with DGVSCMG. The rotation singularity and unwinding problems are solved using the body and shadow sets of the modified Rodrigues parameters. A nonlinear unwinding and kinematic singularity-free fast finite-time sliding mode tracking attitude control is proposed and designed for the satellite attitude control using a single unit of DGVSCMG. The issue of control singularity is addressed using constrained optimization to avoid gimbal lock. It is proved through five new propositions that the system states errors converge first to the sliding surface and then to the origin in fast finite-time with unwinding-free dynamics showing global stability of the system for the track-to-track maneuver. As a special case, it is shown that the proposed control is also applicable to rest-to-rest maneuver. Simulation results are presented and compared with a finite-time sliding control showing superiority of the proposed fast finite-time control in terms of time of convergence and unwinding and singularity-free angular motion.

Multiple-input multiple-output robust vibration control for constrained gyroelastic solar panel considering parametric and un-modeled dynamic uncertainties

Gyroelastic solar panel is a kind of flexible solar panel structure with variable-speed control moment gyroscopes distributed inside. The torque generated by these variable-speed control moment gyroscopes can be used for active vibration suppression. This paper addresses the vibration suppression problem of gyroelastic solar panel in the presence of parametric uncertainties and un-modeled dynamic uncertainties. A novel μ-synthesis method based on analytical multiple-input multiple-output weights design is proposed, which relates 2-norm of the vector of regulated outputs, closed-loop modal damping, and relative control ability of actuators to each mode to the weights. Based on the idea of collocated control, the full order state-space model of the constrained gyroelastic plate with angle gyros as measuring devices is derived. After model reduction, modeling of un-modeled dynamic, and designing the multiple-input multiple-output weights, μ-controller is solved by the DK-iteration method. Furthermore, a comparative study of the μ-controller designed by the proposed procedure and the Positive Position Feedback (PPF) controller designed by the non-smooth H∞ synthesis method is also presented. The control methods are compared for their vibration attenuation, energy utilization, robustness performance characteristics, and robustness stability characteristics. Results for both time domain and frequency domain simulations are presented. Simulation results show that the designed μ-controller has better vibration attenuation effect and robustness performance characteristics than the PPF controller, and can achieve a better robust vibration suppression of the constrained gyroelastic solar panel in presence of parametric and un-modeled dynamic uncertainties.

Velocity-Free Trajectory Tracking and Active Vibration Control of Flexible Space Manipulator

This article studies the trajectory tracking and active vibration control of flexible space manipulator without velocity measurements. Variable-speed control moment gyros (VSCMGs) are adopted as actuators for vibration suppression. Based on the singular perturbation method, the dynamics model of the manipulator system considering the uncertainties and disturbances is decoupled into two reduced-order subsystems: the slow subsystem and the fast subsystem. For the slow subsystem, neural network (NN) is used to approximate the unknown nonlinear functions. An NN-based adaptive integral sliding-mode observer is designed to estimate some unknown velocity variables. An observer-based slow controller is proposed. Considering the uncertainties and the unmeasured modal information of the fast system, a modified extended state observer (ESO) is designed for the estimation of the uncertainties and unknown fast variables. On the basis of the modified ESO, an adaptive feedback controller is proposed for the flexible motion. Lyapunov theory is used to prove the stability of the proposed controllers. The weighted robust pseudoinverse steering laws are designed for VSCMGs. The effectiveness of the proposed observer-based hybrid controller is verified via numerical simulations.

A Gimballed Control Moment Gyroscope Cluster Design for Spacecraft Attitude Control

This paper addresses the problem of singularity avoidance in a cluster of four Single-Gimbal Control Moment Gyroscopes (SGCMGs) in a pyramid configuration when used for the attitude control of a satellite by introducing a new gimballed control moment gyroscope (GCMG) cluster scheme. Four SGCMGs were used in a pyramid configuration, along with an additional small and simple stepper motor that was used to gimbal the full cluster around its vertical (z) axis. Contrary to the use of four variable-speed control moment gyroscopes (VSCMGs), where eight degrees of freedom are available for singularity avoidance, the proposed GCMG design uses only five degrees of freedom (DoFs), and a modified steering law was designed for the new setup. The proposed design offers the advantages of SGCMGs, such as a low weight, size, and reduced complexity, with the additional benefit of overcoming the internal elliptic singularities, which create a minor attitude error. A comparison with the four-VSCMG cluster was conducted through numerical simulations, and the results indicated that the GCMG design was considerably more efficient in terms of power while achieving a better gimbal configuration at the end of the simulation, which is essential when it is desired for different manoeuvres to be consecutively executed. Additionally, for a nano-satellite of a few kilograms, the results prove that it is feasible to manufacture the GCMG concept by using affordable and lightweight commercial off-the-shelf (COTS) stepper motors.

Robust spacecraft rendezvous using a variable speed control moment gyro and thruster

Robust, co-ordinate free, thrust-vector tracking controls are designed for a single Variable Speed Control Moment Gyro (VSCMG). The proposed controls, based on an adaptive active disturbance rejection control and higher-order sliding mode control are presented and compared. These controls guarantee the closed-loop pointing error converges to and remain within a bounded region of the zero error even in the presence of the variable inertia induced by the VSCMG, thruster off-set and uncertain disturbance torques. Secondly, the pointing control law is developed to address the problem of spacecraft rendezvous using only a single thruster and a single VSCMG. Here a pointing guidance law is developed that weights the desired thrust of the rendezvous using a scaling function of the pointing error. This guidance law is shown to significantly improve the performance of the rendezvous maneuver with respect to a guidance law that does not utilize the scaling function. Simulations of a rendezvous maneuver with a 12 U CubeSat are undertaken to demonstrate the applicability of the developed control laws.

Unexpected Collision Detection, Estimation, and Reaction for a Free-Flying Orbital Robot

This paper addresses the unexpected contact handling problem for a free-flying orbital robot. A nonlinear observer is developed to detect, isolate, and estimate a collision. Then, a reaction control strategy is proposed, which aims at avoiding the buildup of the contact force and possible instabilities. It is proved that the controlled system is input-to-state stable. The performance of the observer and the controller is assessed through a numerical example featuring a 7-degree-of-freedom arm mounted on a spacecraft and a realistic measurement model. The spacecraft is equipped with thrusters and variable-speed control moment gyros.

Flexible Structure Vibration Control Using Double-Gimbal Variable-Speed Control Moment Gyros

This paper studies the dynamics and control of a flexible space structure using double-gimbal variable-speed control moment gyros (DGVSCMGs). The DGVSCMGs are mounted on the flexible structure as actuators for attitude and vibration control. A flexible structure with a cluster of angular momentum devices is considered to be a gyroelastic body. The detailed dynamics of a single gyroelastic body under the influence of the actuators is derived using Kane’s method. A simple controller capable of vibration suppression is proposed for the attitude maneuver. A novel steering law is designed for the DGVSCMGs. Null motion of the gimbal angles and rotor rates is considered to compensate for the undesirable modal force in the vibration equation. Numerical simulations are performed to verify the effectiveness of the proposed controller and steering law.

Control of a Thrust-Vectoring CubeSat Using a Single Variable-Speed Control Moment Gyroscope

A minimal actuator design is proposed for orbit-attitude control of a spacecraft. The actuator design includes a single thruster, fixed in the body frame, and a variable-speed control moment gyroscope (VSCMG) used for thrust vectoring. It is known that the full attitude cannot be controlled using a single VSCMG, but that a single axis is controllable. This paper develops a nonlinear control that is able to vector the thruster at discrete intervals or continuously. The closed-loop stability of the system is proved using Lyapunov stability theory for each control law. These control laws could enable high maneuverability of CubeSats, using either a single chemical (impulsive) or electric thruster (continuous). The controls are demonstrated, in simulation, with an application to a 12U CubeSat rendezvous using a single throttable electric thruster.

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.

Attitude control for spacecraft using pyramid-type variable-speed control moment gyros

In this paper, the attitude control of spacecraft using a pyramid-type variable-speed control moment gyro (VSCMG) system is considered. For successive attitude maneuvers, it is desirable that the wheel angular momentums are regulated to nominal values after an attitude maneuver. In addition, avoidance of reference aligned singularity (RAS) is also important. RAS is a singularity point where the singular direction of the constant-speed control moment gyro (CSCMG) system is aligned to a reference torque. Regarding the motivations, this paper proposes a steering law which achieves attitude control and regulates the wheel angular momentums while successfully avoiding RAS. Both numerical simulations and experimental verification are performed to demonstrate not only the validity of the proposed method, but also a certain robustness against unmodeled dynamics and the gravity torque.

Integrated power and vibration control of gyroelastic body with variable-speed control moment gyros

The gyroelastic body refers to a flexible structure with distributed angular momentum exchange devices (AMEDs), such as the momentum wheels (MWs) or the control moment gyros (CMGs). The amplitude or the direction of the angular momentum of the rotors in the AMEDs can be changed to produce torques for vibration suppression of the flexible structure. In order to take full advantage of the AMEDs on the flexible structure, the AMEDs are also used for energy storage in this study, thus, an integrated power and vibration control system (IPVCS) is obtained. In this paper, the single-gimbal variable speeds control momentum gyros (VSCMGs) are chosen as the distributed AMEDs mounting on a constrained flexible structure. It can work in a “CMG & MW” mode and a “VSCMG” mode for simultaneous vibration suppression and energy storage. First, the dynamics of a constrained gyroelastic body is established, whereas the power equation of the rotors is deduced. Second, the feedback control laws are designed when the VSCMGs work in the CMG & MW mode and the VSCMG mode, respectively. Finally, numerical examples are presented for a flexible truss with distributed VSCMGs to verify the effectiveness of the proposed feedback control strategies.

Variable Speed Control Moment Gyroscope in an Inverted Pendulum

AbstractThe use of variable speed control moment gyroscope (VSCMG) is an effective way for attitude stabilization of aerospace devices. It is possible to control the oscillation and direction rate of change in rigid bodies in space due to the controlled change of angular momentum rate. Thus, this paper proposes an atypical pendulum configuration controlled by a VSCMG actuator. The idea of the VSCMG pendulum (VSCMGP) is to use both the angular momentum variation in amplitude and direction to implement the control. The controller is designed using Lyapunov theory to stabilize the pendulum in the inverted position. The results illustrate the control using a VSCMG in an inverted pendulum showing how the stabilization of an inverted pendulum is performed using two control actions. Also, the comparison of the proposed pendulum with a classical configuration is presented.

Vibration control of gyroelastic spacecraft using input shaping and angular momentum devices

This paper studies the vibration control of gyroelastic spacecraft. The dynamics of gyroelastic spacecraft considering the angular momentum devices are derived using Kane's method. A novel control strategy combining input shaping (IS) and variable-speed control moment gyros (VSCMGs) is proposed to suppress the flexible vibration of gyroelastic spacecraft. Input shaping technique is used to suppress the flexible vibration due to attitude motion. An adaptive controller is designed to further reduce the residual vibration using VSCMGs. Considering that the modal variable cannot be measured in practice, a novel modal observer is designed to estimate the modal variables for vibration control. Simulations are conducted to verify the effectiveness of the proposed control strategy.

The optimization design with minimum power for variable speed control moment gyroscopes with integrated power and attitude control

The task of Integrated Power and Attitude Control (IPAC) of a spacecraft can be implemented by Variable Speed Control Moment Gyros (VSCMGs). The Integrated Power and Attitude Control System (IPACS) singularity problem is the key factor for the spacecraft to successfully perform IPAC task, which can be overcome by rational designing steering law. The singularity characteristic and the steering law should be considered during the process of design parameters for the VSCMG cluster with IPACS task. There is no research report in this area at present. The steering results of weighted pseudo-inverse and null motion of Weighted Pseudo-Inverse with Null Motion (WPINM) can be canceled by each other under some certain condition. So the flywheel torque requirement of the WPINM steering law can be greatly increased, which is contradictory to the original design intention of the weighted matrix. A steering law with minimum requirement of flywheel power and torque is introduced from existing research result. Then, the constraint of the IPACS singularity problem and the SGCMGs singularity problem cannot be encountered during the whole process of IPAC task is given. At last, the parameters design problem of VSCMGs for the IPAC task is cast as a multi-objective optimization problem with minimum whole system power and maximum utilization ratio of flywheel momentum under the condition of consideration of the steering. The intelligent algorithm of Non-dominated Sorting Genetic Algorithm (NSGA) is used to solve the nonlinear multi-objective problem. The flywheel power can be greatly reduced by the new parameters design method.