145 research outputs found
Design and Implementation of a Fault-Tolerant Magnetic Bearing System for MSCMG
The magnetically suspended control moment gyros (MSCMGs) are complex system with multivariable, nonlinear, and strongly gyroscopic coupling. Therefore, its reliability is a key factor to determine whether it can be widely used in spacecraft. Fault-tolerant magnetic bearing systems have been proposed so that the system can operate normally in spite of some faults in the system. However, the conventional magnetic bearing and fault-tolerant control strategies are not suitable for the MSCMGs because of the moving-gimbal effects and requirement of the maximum load capacity after failure. A novel fault-tolerant magnetic bearing system which has low power loss and good robust performances to reject the moving-gimbal effects is presented in this paper. Moreover, its maximum load capacity is unchanged before and after failure. In addition, the compensation filters are designed to improve the bandwidth of the amplifiers so that the nutation stability of the high-speed rotor cannot be affected by the increasing of the coil currents. The experimental results show the effectiveness and superiority of the proposed fault-tolerant system
Discrete Model Reference Adaptive Control for Gimbal Servosystem of Control Moment Gyro with Harmonic Drive
The double-gimbal control moment gyro (DGCMG) demands that the gimbal servosystem should have fast response and small overshoot. But due to the low and nonlinear torsional stiffness of harmonic drive, the gimbal servo-system has poor dynamic performance with large overshoot and low bandwidth. In order to improve the dynamic performance of gimbal servo-system, a model reference adaptive control (MRAC) law is introduced in this paper. The model of DGCMG gimbal servo-system with harmonic drive is established, and the adaptive control law based on POPOV super stable theory is designed. The MATLAB simulation results are provided to verify the effectiveness of the proposed control algorithm. The experimental results indicate that the MRAC could increase the bandwidth of gimbal servo-system to 3 Hz and improve the dynamic performance with small overshoot
Integrated Power and Attitude Control Design of Satellites Based on a Fuzzy Adaptive Disturbance Observer Using Variable-Speed Control Moment Gyros
To satisfy the requirements for small satellites that seek agile slewing with peak power, this paper investigates integrated power and attitude control using variable-speed control moment gyros (VSCMGs) that consider the mass and inertia of gimbals and wheels. The paper also details the process for developing the controller by considering various environments in which the controller may be implemented. A fuzzy adaptive disturbance observer (FADO) is proposed to estimate and compensate for the effects of equivalent disturbances. The algorithms can simultaneously track attitude and power. The simulation results illustrate the effectiveness of the control approach, which exhibits an improvement of 80 percent compared with alternate approaches that do not employ a FADO
Study on stability and rotating speed stable region of magnetically suspended rigid rotors using extended Nyquist criterion and gain-stable region theory
This paper presents a novel and simple method to analyze the absolute stability and the rotor speed stable region of a magnetically suspended rotor (MSR). At the beginning of the paper, a complex variable is introduced to describe the movement of the MSR and a complex coefficient transfer function is obtained accordingly. The equivalent stability relationship between this new variable and the two traditional deflection angles is also demonstrated in a simple way. The detailed characteristics of the open-loop MSR system with time delay are studied carefully based on the characteristics of its Nyquist curve. A sufficient and necessary condition of absolute stability is then deduced by using an extended complex Nyquist stability criterion for MSRs. Based on the relationship between the rotor speed and gain-stable region proposed in this paper, the rotor speed stable region can be solved simply and directly. The usefulness and effectiveness of the proposed approaches are validated by examples and simulations
MIMO active vibration control of magnetically suspended flywheels for satellite IPAC service
Theory and simulation results have demonstrated that four, variable speed flywheels
could potentially provide the energy storage and attitude control functions of existing
batteries and control moment gyros (CMGs) on a satellite. Past modeling and control
algorithms were based on the assumption of rigidity in the flywheel’s bearings and the
satellite structure.
This dissertation provides simulation results and theory which eliminates this
assumption utilizing control algorithms for active vibration control (AVC), flywheel
shaft levitation and integrated power transfer and attitude control (IPAC) that are
effective even with low stiffness active magnetic bearings (AMB), and flexible satellite
appendages.
The flywheel AVC and levitation tasks are provided by a multi input multi output
(MIMO) control law that enhances stability by reducing the dependence of the forward
and backward gyroscopic poles with changes in flywheel speed.
The control law is shown to be effective even for (1) Large polar to transverse inertia ratios which increases the stored energy density while causing the poles to
become more speed dependent and, (2) Low bandwidth controllers shaped to suppress
high frequency noise. These two main tasks could be successfully achieved by MIMO
(Gyroscopic) control algorithm, which is unique approach.
The vibration control mass (VCM) is designed to reduce the vibrations of flexible
appendages of the satellite. During IPAC maneuver, the oscillation of flywheel spin
speeds, torque motions and satellite appendages are significantly reduced compared
without VCM. Several different properties are demonstrated to obtain optimal VCM.
Notch, band-pass and low-pass filters are implemented in the AMB system to
reduce and cancel high frequency, dynamic bearing forces and motor torques due to
flywheel mass imbalance. The transmitted forces and torques to satellite are
considerably decreased in the present of both notch and band-pass filter stages.
Successful IPAC simulation results are presented with a 12 [%] of initial attitude
error, large polar to transverse inertia ratio (IP / IT), structural flexibility and unbalance
mass disturbance.
Two variable speed control moment gyros (VSCMGs) are utilized to demonstrate
simultaneous attitude control and power transfer instead of using four standard pyramid
configurations. Launching weights including payload and costs can be significantly
reduced
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A Spherical Magnetic Dipole Actuator for Spacecraft Attitude Control
Spacecraft generally require multiple attitude control devices to achieve full attitude actuation because of the limited control authority a single, traditional device can provide. This work presents a new momentum-exchange device that has the potential to replace traditional attitude control systems with a single actuator, in turn providing mass, volume, and power savings. The proposed actuator consists of a spherical dipole magnet enclosed in an array of coils that are fixed to the spacecraft body. Excitation of the coils as prescribed by the control law accelerates the dipole magnet in such a manner as to produce a desired reaction torque for orienting the spacecraft. The coils also control the magnet's position inside the spacecraft body via a separate control law, which is necessary because of the non-contact nature of the device. Analytical force and torque models are developed and are used in an attitude regulation maneuver. Simulations conducted so far indicate that full attitude control is possible from a single device despite the axisymmetric field of the magnetic dipole rotor, which was anticipated to cause control issues. Finally, the single actuator system is compared to a cluster of three reaction wheels, illustrating how this device can provide mass, volume, and power savings
An Assessment of Integrated Flywheel System Technology
The current state of the technology in flywheel storage systems and ancillary components, the technology in light of future requirements, and technology development needs to rectify these shortfalls were identified. Technology efforts conducted in Europe and in the United States were reviewed. Results of developments in composite material rotors, magnetic suspension systems, motor/generators and electronics, and system dynamics and control were presented. The technology issues for the various disciplines and technology enhancement scenarios are discussed. A summary of the workshop, and conclusions and recommendations are presented
Complex-Coefficient Frequency Domain Stability Analysis Method for a Class of Cross-Coupled Antisymmetrical Systems and Its Extension in MSR Systems
This paper develops a complex-coefficient frequency domain stability analysis method for a class of cross-coupled two-dimensional antisymmetrical systems, which can greatly simplify the stability analysis of the multiple-input multiple-output (MIMO) system. Through variable reconstruction, the multiple-input multiple-output (MIMO) system is converted into a single-input single-output (SISO) system with complex coefficients. The pole locations law of the closed-loop system after the variable reconstruction has been revealed, and the controllability as well as observability of the controlled plants before and after the variable reconstruction has been studied too, and then the classical Nyquist stability criterion is extended to the complex-coefficient frequency domain. Combined with the rigid magnetically suspended rotor (MSR) system with heavy gyroscopic effects, corresponding stability criterion has been further developed. Compared with the existing methods, the developed criterion for the rigid MSR system not only accurately predicts the absolute stability of the different whirling modes, but also directly demonstrates their relative stability, which greatly simplifies the analysis, design, and debugging of the control system
Third International Symposium on Magnetic Suspension Technology
In order to examine the state of technology of all areas of magnetic suspension and to review recent developments in sensors, controls, superconducting magnet technology, and design/implementation practices, the Third International Symposium on Magnetic Suspension Technology was held at the Holiday Inn Capital Plaza in Tallahassee, Florida on 13-15 Dec. 1995. The symposium included 19 sessions in which a total of 55 papers were presented. The technical sessions covered the areas of bearings, superconductivity, vibration isolation, maglev, controls, space applications, general applications, bearing/actuator design, modeling, precision applications, electromagnetic launch and hypersonic maglev, applications of superconductivity, and sensors
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