Influence of flexible solar arrays on vibration isolation platform of control moment gyroscopes

A high-performance vibration isolation platform （VIP） has been developed for a cluster of control moment gyroscopes （CMGs）. CMGs have long been used for satellite attitude control. In this paper, the influence of flexible solar arrays on a passive multi-strut VIP of CMGs for a satellite is analyzed. The reasonable parameters design of flexi- ble solar arrays is discussed. Firstly, the dynamic model of the integrated satellite with flexible solar arrays, the VIP and CMGs is conducted by Newton-Euler method. Then based on reasonable assumptions, the transmissibility matrix of the VIP is derived. Secondly, the influences of the flexible solar arrays on both the performance of the VIP and the stability of closed-loop control systems are analyzed in detail. The parameter design limitation of these solar arrays is discussed. At last, by selecting reasonable parameters for both the VIP and flexible solar arrays, the attitude stabilization performance with vibration isolation system is predicted via simulation.

Model predictive control of rigid spacecraft with two variable speed control moment gyroscopes

In this paper, an attitude maneuver control problem is investigated for a rigid spacecraft using an array of two variable speed control moment gyroscopes （VSCMGs） with gimbal axes skewed to each other. A mathematical model is constructed by taking the spacecraft and the gyroscopes together as an integrated system, with the coupling interaction between them considered. To overcome the singular issues of the VSCMGs due to the conventional torque-based method, the first-order derivative of gimbal rates and the second-order derivative of the rotor spinning velocity, instead of the gyroscope torques, are taken as input variables. Moreover, taking external disturbances into account, a feedback control law is designed for the system based on a method of nonlinear model predictive control （NMPC）. The attitude maneuver can be realized fast and smoothly by using the proposed controller in this paper.

Cooperative game theory-based steering law design of a CMG system

Spacecraft require a large-angle manoeuvre when performing agile manoeuvring tasks, therefore a control moment gyroscope(CMG) is employed to provide a strong moment.However, the control of the CMG system easily falls into singularity, which renders the actuator unable to output the required moment. To solve the singularity problem of CMGs, the control law design of a CMG system based on a cooperative game is proposed. First, the cooperative game model is constructed according to the quadratic programming problem, and the cooperative strategy is constructed. When the strategy falls into singularity, the weighting coefficient is introduced to carry out the strategy game to achieve the optimal strategy. In theory, it is proven that the cooperative game manipulation law of the CMG system converges, the sum of the CMG frame angular velocities is minimized, the energy consumption is small, and there is no output torque error. Then, the CMG group system is simulated.When the CMG system is near the singular point, it can quickly escape the singularity. When the CMG system falls into the singularity, it can also escape the singularity. Considering the optimization of angular momentum and energy consumption, the feasibility of the CMG system steering law based on a cooperative game is proven.

Decentralized adaptive sliding mode control of a space robot actuated by control moment gyroscopes

An adaptive sliding mode control （ASMC） law is proposed in decentralized scheme for trajectory tracking control of a new concept space robot. Each joint of the system is a free ball joint capable of rotating with three degrees of freedom （DOF）. A cluster of control moment gyroscopes （CMGs） is mounted on each link and the base to actuate the system. The modified Rodrigues parameters （MRPs） are employed to describe the angular displacements, and the equations of motion are derived using Kane＇s equations. The controller for each link or the base is designed sep- arately in decentralized scheme. The unknown disturbances, inertia parameter uncertainties and nonlinear uncertainties are classified as a ＂lumped＂ matched uncertainty with unknown upper bound, and a continuous sliding mode control （SMC） law is proposed, in which the control gain is tuned by the improved adaptation laws for the upper bound on norm of the uncertainty. A gen- eral amplification function is designed and incorporated in the adaptation laws to reduce the control error without conspicuously increasing the magnitude of the control input. Uniformly ultimate boundedness of the closed loop system is proved by Lyapunov＇s method. Simulation results based on a three-link system verify the effectiveness of the proposed controller.

Fault diagnosis of control moment gyroscope based on a new CNN scheme using attention-enhanced convolutional block

Control moment gyroscope(CMG)is a typical attitude control system component for satellites and mobile robots,and the online fault diagnosis of CMG is crucial because it determines the stability and accuracy of the attitude control system.This paper develops a data-driven CMG fault diagnosis scheme based on a new CNN method.In this design,seven types of fault signals are converted into spectrum datasets through short-time Fourier transformation(STFT),and a new CNN network scheme called AECB-CNN is proposed based on attention-enhanced convolutional blocks(AECB).AECB-CNN can achieve high training accuracy for the CMG fault diagnosis datasets under different sliding window parameters.Finally,simulation results indicate that the proposed fault diagnosis method can achieve an accuracy of nearly 95%in 1.28 s and 100%in 2.56 s,respectively.

Disturbance rejection for biped robots during walking and running using control moment gyroscopes

Keeping balance in movement is an important premise for biped robots to complete various tasks.Now,the balance control of biped robots mainly depends on the cooperation of various joints of the robot's body.When robots move faster,the adjustment allowance of joints is reduced,and the robot's anti-disturbance ability will inevitably decline.To solve this problem,the control moment gyroscope(CMG)is creatively used as an auxiliary stabilisation device for fully actuated biped robots and the CMG assistance strategy,which can be integrated into the biped's balance control framework,is proposed.This strategy includes model predictive control module,distribution module,and CMG precession controller.Under the command of it,CMGs can effectively assist the robot in resisting impact and returning to initial positions in time.The results of anti-impact simulation on the walking and running biped robot prove that,with the help of CMGs,the robot's ability to resist disturbance and remain stable is significantly improved.The cover image is based on the Original Article Disturbance rejection for biped robots during walking and running using control moment gyroscopes by Haochen Xu et al.,https://doi.org/10.1049/csy2.12070.

Dynamic analysis and identification of unbalance and misalignment in a rigid rotor with two offset discs levitated by active magnetic bearings:a novel trial misalignment approach

Rotating machinery is an essential and crucial component of numerous mechanical systems in modern industries,transport vehicles,and in several other applications.Excessive vibrations on rotating equipment due to multiple faults may cause catastrophic failure in machines and lead to hazardous accidents.So,there is a need for perceiving the dynamic nature and identifying the faults for the safe,smooth and effective operation of machines.This paper proposes a novel trial misalignment approach to estimate the misalignment with a similar concept as the trial unbalance in the rotor balancing.Active magnetic bearing(AMB)misalignment with the rotor has been investigated with residual misalignment and additional trial misalignment cases.Additional trial misalignments are provided in addition to the unknown misalignments of the residual misalignment case.For the execution of this methodology,the dynamic model of a four-degree-of-freedom unbalanced and misaligned rigid rotor with two offset discs supported by two active magnetic bearings has been mathematically developed.The offset discs result in the gyroscopic effect at high rotor speeds.Equations of motion of the rotor-AMB system have been derived and solved to generate the time domain rotor displacement and controlling current responses at AMB positions.A fast Fourier transform technique has been utilized to convert the time domain responses into the frequency domain for estimation of unbalance eccentricities and phases together with force-displacement and forcecurrent stiffnesses of misaligned AMBs as well as AMB's constant forces using the developed identification algorithm.Identified values of AMB's parameters for both residual and additional trial misalignment cases are evaluated to estimate the four unknown misalignments.Testing of the algorithm has also been carried out at multiple spin speeds against measurement signal noise in rotor responses and bias errors in rotor system parameters to check its effectiveness and robustness.The algorithm is found to be exhibiting excellent.

Bending and vibration of a discontinuous beam with a curvic coupling under different axial forces

The transverse stiffness and vibration characteristics of discontinuous beams can significantly differ from those of continuous beams given that an abrupt change in stiffness may occur at the interface of the former.In this study,the equations for the deflection curve and vibration frequencies of a simply supported discontinuous beam under axial loads are derived analytically on the basis of boundary,continuity,and deformation compatibility conditions by using equivalent spring models.The equation for the deflection curve is solved using undetermined coefficient methods.The normal function of the transverse vibration equation is obtained by separating variables.The differential equations for the beam that consider moments of inertia,shearing effects,and gyroscopic moments are investigated using the transfer matrix method.The deflection and vibration frequencies of the discontinuous beam are studied under different axial loads and connection spring stiffness.Results show that deflection decreases and vibration frequencies increase exponentially with increasing connection spring stiffness.Moreover,both variables remain steady when connection spring stiffness reaches a considerable value.Lastly,an experimental study is conducted to investigate the vibration characteristics of a discontinuous beam with a curvic coupling,and the results exhibit a good match with the proposed model.

Singularity radius gradient-based rapid singularity-escape steering law for SGCMGs

In order to visualize singularity of SGCMGs in gimbal angle space,a novel continuous bounded singularity parameter--Singularity Radius,whose sign can distinctly determine singularity type,is proposed.Then a rapid singularity-escape steering law is proposed basing on gradient of Singularity Radius and residual base vector to drive the SGCMG system to neighboring singular boundary,and quickly escape elliptic singularities.Finally,simulation results on Pyramid-type and skew-type configuration demonstrate the effectiveness and rapidness of the proposed steering law.

A recursive formulation for open-loop gyroelastic multibody dynamics

In this paper,a general recursive formulation of equations of motion is presented for open-loop gyroelastic multibody systems.The gyroelastic multibody system is defined as a multibody system with gyroelastic bodies,whereas a gyroelastic body is composed of a flexible body with a cluster of double-gimbal variable-speed control moment gyroscopes(DGVs).First,the motion equations of a single gyroelastic body are derived using Kane’s method.The influence of DGVs on the static moments,modal momentum coefficients,moments of inertia,modal angular momentum coefficients,and modal mass matrix for a flexible body are considered.The interactions between the DGVs and the flexibilities of the structures are captured.The recursive kinematic relations for a multibody system with different connections are then obtained from a flexible-flexible connection using a transformation matrix.The different connections contain a flexible-flexible connection,which represents a flexible body connecting to another flexible body,flexible-rigid and rigid-rigid connections.The recursive gyroelastic multibody dynamics are obtained by analyzing the kinematics of a multibody system and the dynamics of a single gyroelastic body.Numerical simulations are presented to verify the accuracy and efficiency of the proposed approach by comparing it with a direct formulation based on Kane’s method.