Magnetically Suspended Control Moment Gyro Research Articles

Synchronous Vibration Force Suppression of Magnetically Suspended CMG Based on Modified Double SOGI-FLL

The mass imbalance of the rotor will produce the synchronous vibration force that is transmitted to the magnetically suspended control moment gyroscope (MSCMG) through the magnetic levitation stator, which affects the imaging performance of the satellite. The suppression of the synchronous vibration force needs the speed signal. In order to solve the synchronous vibration force of the MSCMG when the speed measurement sensor fails, this paper proposed an modified double second-order generalized integral frequency-locked loop (SOGI-FLL) method, which uses the frequency of the disturbance signal generated through the mass imbalance of the rotor to adaptively estimate the rotor speed and suppress the synchronous vibration force generated by the active magnetic bearing system. The phase compensation is introduced to ensure the stability of the system in full frequency band. The electromagnetic force is directly used as the input signal of the control algorithm to achieve zero magnetic force control. Simulation and experimental are carried out, and the results are given to prove that the algorithm proposed in this paper can accurately estimate the rotation speed and achieve the vibration force suppression in the full rotation speed range. It is of great significance for the high-precision control of the active magnetic bearing rotor system.

High-Precision Suppression of Harmonic Vibration Force by Repetitive Controller With Triple-Loop Structure

The harmonic vibration force generated by multi-source disturbances through the magnetic bearing closed-loop control system seriously affects the improvement of the performance of the magnetically suspended control moment gyroscope (MSCMG). The harmonic noise introduced by the displacement sensor generates harmonic components through a closed-loop control system, and the compensation accuracy of synchronous displacement stiffness force is reduced by the low-pass characteristics of the power amplifier. In this paper, the rotor displacement signal and current signal are used as inputs to the repetitive controller and notch filter, and the power amplifier and repetitive controller are constructed into three closed-loop systems to achieve high-precision suppression of harmonic vibration forces. Finally, the effectiveness of the method is demonstrated by using a 200Nms MSCMG and a micro-vibration test system.

High-Dynamic and Low-Cost Sensorless Control Method of High-Speed Brushless DC Motor

Sensorless control is an effective measure to improve reliability and reduce cost for the brushless DC motor (BLDCM). However, the performance is generally related to the cost and complexity of the system, making it difficult for engineering applications. Therefore, this paper proposes a high-dynamic and low-cost sensorless control method for high-speed BLDCMs using the rich built-in resources of the digital signal processor (DSP). Firstly, a variable relating to the commutation moment is constructed and detected, which is not affected by modulation noise. Then, a detailed commutation process is presented based on the relationship between the back electromotive force (back-EMF) integral and the commutation point. Moreover, an integral prediction method is proposed by linearizing the back-EMF to cope with the effect of discrete sampling on commutation accuracy. Finally, experimental tests are performed on a magnetically suspended control moment gyroscope (MSCMG), which verifies the effectiveness of the proposed high-dynamic and low-cost sensorless control method.

Torque Ripple Minimization of Low-Speed Gimbal Servo System Using Parameter-Optimized ESO

Torque ripple of permanent magnet synchronous motor (PMSM) and load disturbances are the main influencing factors which restrict the application of PMSM in low speed tracking system. In order to improve the speed tracking precision of gimbal servo system in control moment gyro (CMG) with multi-source disturbances, this paper proposes a composite control method based on parameter-optimized extended state observers (ESOs) with sliding mode control in the speed loop and PI control with a feed-forward compensation in the current loop. Three ESOs are employed to estimate the disturbances on d-axis current, q-axis current and the load torque, so that the controller can have the corresponding parts to compensate for the disturbances. In particular, aiming at the contradiction between the estimation quality of the observer and the sensitivity to the measurement noise, an appropriate cost function is designed to take a compromise between the lumped disturbances and measurement noise and optimize the parameters of the ESOs. Finally, simulation and experimental results on the gimbal servo system of magnetically suspended control moment gyroscope (MSCMG) show the effectiveness of the proposed methods.

Design, optimization and test of RHMB considering dynamic characteristics

The coil inductance, stiffness and losses of the magnetic bearing (MB) have great influence on the dynamic performance for the magnetically suspended control moment gyro (MSCMG) application. Based on the equivalent magnetic circuits considering flux leakage effects, a design, optimization and test method is proposed to enhance the dynamic response ability for the radial hybrid MB (RHMB). The optimization design objectives including bearing force, stiffness, coil current, mass, inductance and loss estimation are discussed under the multiple constraints. Compared with the original design, the dynamic characteristics including frequency responses of current and rotor displacements for the RHMB-rotor system are significantly improved after optimization. A prototype of MSCMG is fabricated to verify the dynamic response characteristic of the RHMB.

Low power control for magnetically suspended control moment gyro based on current adaptive adjustment‐gimbal angular velocity feedforward method

Magnetically suspended control moment gyro (MSCMG) outputs gyro moment by changing the direction of the rotor angular momentum to adjust the spacecraft attitude. In the process of outputting moment, due to the moving-gimbal effect, the power consumption of magnetic bearing occupies a large proportion in MSCMG. The existing low power control methods have problems that adjustment time is long and the effect of reducing energy consumption depends on the model accuracy. To solve these problems, the method of current adaptive adjustment-gimbal angular velocity feedforward (CAA-GAVF) is proposed. The CAA-GAVF method controls rotor deflect actively so that the permanent magnet can generate moment to offset the coupling moment of moving-gimbal effect, thus reducing the power consumption of control current. In CAA-GAVF, the deflection angle of rotor is quickly adjusted by the feedforward of gimbal angular velocity. The current integral value is used to adjust the feedforward matrix adaptively and precisely. The experimental results show that the power consumption of CAA-GAVF method is reduced to 43.3% of the traditional control method.

A novel worm gear actuated repeatable locking/unlocking device for magnetically suspended control moment gyro

The locking/unlocking device (LUD) is crucial to protect the rotor in magnetically suspended control moment gyro (MSCMG) from vibration impacts during launch. Conventional LUDs have inevitable shortcomings in repeatability, compactness and reliability for aerospace applications. To overcome these disadvantages, this paper proposes a novel worm gear actuated repeatable locking/unlocking device (RLUD) consisting of an actuator, several transmission mechanism components and a locking nut. The configuration, working principle and design consideration are introduced in detail. Since the worm gear is a key component for torque transmission, the reliability analysis considering correlated failure modes of the tooth surface contact and tooth root bending is carried out by means of the fourth-order moment approach and copula function. The optimization design for the worm gear is subsequently implemented. The reliability analysis of the worm gear demonstrates that the assumption of independent failure modes without correlate consideration is likely to acquire conservative results, thus resulting in structural redundancy. Then, the optimization design is performed to achieve weight reduction under high reliability. The RLUDs based on optimization results are manufactured and then integrated into a prototype of MSCMG rotor system. Finally, a series of mechanics tests are conducted to evaluate the functional performance. The result of static load test shows that the strength and self-locking capacity of the RLUD are sufficient to support the compression load. The real-time response of the vibration signal indicates that the whole prototype is safe enough without any large shocks, thus satisfying the launch requirements. The relative displacements between the rotor and stator during vibrations are far less than the protective air gap, thus verifying the locking effect of the RLUD on the rotor.

Gimbal Angular Velocity Feedforward Method for Magnetically Suspended Control Moment Gyro with Hybrid Magnetic Bearing#

Control moment gyro(CMG) has the advantages of high precision and large output moment. It is the key actuator of agile spacecraft attitude control system. Magnetically suspended CMG(MSCMG) supports high-speed rotor through magnetic bearing, which has the advantages of no friction, no wear, high precision and long life. Hybrid magnetic bearing(HMB) generates bias magnetic field by replacing bias current with permanent magnet, which greatly reduces the power consumption. However, when MSCMG output moment, moving-gimbal effect makes the control current of HMB increase sharply, which result in the rapid increase of power consumption. To solve this problem, gimbal angular velocity feedforward(GAVF) method is proposed in this paper. Firstly, the model of HMB-rotor system containing moving-gimbal effect is established. Secondly, GAVF method is introduced to make the rotor deflect by designing a feedforward matrix with gimbal angular velocity and stiffness of HMB which is determined with rotor deflection angle and rotation speed. Thus, the gyroscopic moment is mainly offset by the bias magnetic field of HMB. Finally, an adaptive compensation method based on GAVF is proposed to maintain the system performance under parameter perturbation. By the above, the power consumption of control current during moment output process is reduced. Simulation and experiment results show the effectiveness of the proposed method.

Harmonic Vibration Control of MSCMG Based on Multisynchronous Rotating Frame Transformation

Magnetically suspended control moment gyro (MSCMG) is used in high-performance satellite platforms such as ultraquiet and ultrastable satellite. However, due to the unbalanced mass and sensor runout, the harmonic vibrations of synchronous and multifrequency will be generated, which will affect satellite performance. Aiming at the problem of harmonic vibration suppression of MSCMG, this article proposes a control algorithm based on multisynchronous rotating frame transformation. The electromagnetic force of the active magnetic bearing in MSCMG is directly used as the input signal of the control algorithm to achieve zero magnetic force control. This algorithm uses the orthogonal characteristics of the output signals of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -direction and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> -direction displacement sensors. The vibration force in both directions can be suppressed by one controller simultaneously, saving the computing resources and having a faster response speed. The stability of the proposed method and the robustness to frequency fluctuations are analyzed. By changing the phase compensation angle in different frequency ranges, the stability of the system in the whole frequency band is ensured. Finally, experimental results are given to verify that the proposed method can achieve high precision and fast response suppression of harmonic vibration.

Unbalance Vibration Control for MSCMG Based on High-Precision Synchronous Signal Detection Method

The active magnetic bearing rotor in magnetically suspended control moment gyro (MSCMG) will produce unbalance vibration due to the mass unbalance, and the frequency equal to the rotation speed. In order to suppress the unbalance vibration of MSCMG, the working principle of the active magnetic bearing (AMB) is introduced and the unbalance vibration model is established. And then, a high-precision closed-loop detection method of the synchronous signal based on synchronous rotating frame transformation (SRFT) is proposed. This method can detected synchronous signals in two directions at the same time, with less calculations. The synchronous current is suppressed by detecting and compensating the synchronous component in the output signal of the displacement sensor, which can reduce most of unbalance vibration. The phase modulation angle is introduced to make the algorithm have a wider stable range. In order to simplify the analysis method, the orthogonal characteristic of the output signal of the displacement sensor is used to equalize the dual output system to a complex-coefficients single-input system, and the dual frequency Bode diagram is used to analyze and evaluate the stability of the system. Finally, experimental results are given to verify that this method can effectively suppress synchronous current.

Design and optimization of repeatable locking/unlocking device for magnetically suspended control moment gyro

Due to the air gap between stator and rotor, magnetically suspended control moment gyro (MSCMG) should be equipped with locking/unlocking device (LUD) to sustain launch vibration and impact. Current LUDs are not repeatable, reliable and compact enough for gyro applications. In this paper, a repeatable locking/unlocking device (RLUD) with several elastic brackets as clamping/releasing mechanism is proposed. Based on the equivalent beam model, static and dynamic analyses of the brackets are carried out, and the maximum stress, the locking/unlocking force and the resonance frequency are obtained. Subsequently, the optimization design using non-linear programming by quadratic Lagrangian (NLPQL) algorithm is implemented, and structural parameters of the optimized brackets are calculated. The maximum stress and first resonance frequency are simulated through finite element method (FEM), and the results are in good agreement with those of the elastic beam analyses. Finally, a MSCMG rotor system with the designed RLUD is fabricated. The environmental mechanics tests including sine sweep and random vibration are performed, which verifies the locking protection effect for MSCMG rotor.

Fast Commutation Error Compensation Method of Sensorless Control for MSCMG BLDC Motor With Nonideal Back EMF

As aerospace applications, high reliability and low power consumption operation of the brushless direct current (BLDC) motor for the magnetically suspended control moment gyro (MSCMG) is the primary consideration. To guarantee reliability, the sensorless control without position sensors is adopted. Due to the phase lag caused by hardware and software, the commutation error is inevitable. In order to reduce losses, this article proposes a fast commutation error compensation method to improve commutation accuracy. First, the control topology of the BLDC motor with a buck converter and the commutation point detection circuit are presented. Then, the conducting back electromotive force (EMF) contained in a novel derived dc-link voltage expression is estimated through an extended state observer (ESO). Finally, the commutation error is extracted from the conducting back EMF for compensation. Different from the conventional closed-loop correction method based on the back EMF symmetry, the proposed commutation error compensation method can obtain the commutation error within only one commutation cycle by a continuous estimation with the ESO. The effectiveness of the proposed fast commutation error compensation method was evaluated with an MSCMG system.

Synchronous Vibration Suppression of Magnetically Suspended Rotor System Using Improved Adaptive Frequency Estimation

The rotor system of magnetically suspended control moment gyro (MSCMG) inevitably has unbalanced amount due to errors in its materials and processing accuracy. The mass unbalance of the rotor will cause the system to generate synchronous vibration and then transmit it to the spacecraft platform through the base, which will seriously affect the imaging quality. The realization of synchronous vibration suppression depends seriously on the rotor speed signal. When the Hall speed sensor has a large measurement error or fails, it is necessary to adaptively estimate the rotor speed to suppress the unbalance vibration of the rotor system. This paper proposes an improved adaptive frequency estimation (IAFE) method. This algorithm uses the characteristics of the rotor radial displacement sensor signal to adaptively estimate the rotor speed, and then suppress the synchronous current generated by the control system. It maintains the stability of the system by changing the phase shift angle at different frequencies, and the residual displacement stiffness force is also compensated. The simulation results show that the proposed method is easy to be implemented, and it can achieve high-precision suppression of unbalanced vibration.

Integrated control of attitude maneuver and vibration suppression of flexible spacecraft based on magnetically suspended control moment gyros

This paper adopts magnetically suspended control moment gyro (MSCMG) to realize the integration of attitude control and wideband micro-vibration suppression of spacecraft without adding extra hardware resources. The coupling between central rigid body and flexible attachment has been effectively retained in the controller design. First, an open-loop modal observer is constructed in advantage of the inherent physical characteristics of flexible modes, and then an adaptive backstepping controller involving flexible modal estimation, spacecraft attitude quaternion, and angular velocity is designed. Next, the band-pass filters are employed to separate the low-frequency gimbal command angular rate signal and medium–high-frequency rotor command angular rate signal, respectively, so that MSCMG can accurately track the command signal output by the integrated controller. Taking advantage of MSCMG’s ability to output high bandwidth micro-gimbal moment, the proposed method can not only meet the requirement of spacecraft rapid maneuver but also effectively suppress the broadband micro-vibration, including low-frequency flexible vibration and medium–high-frequency micro-vibration caused by spacecraft rotating parts. Numerical simulations and frequency domain analysis demonstrate the correctness and effectiveness of the proposed method.

Stable control of the high-speeding magnetically suspended rotor based on extended state observer and two-degree freedom internal model control for control moment gyros with serious moving-gimbal effects

For a magnetically suspended control moment gyro (MSCMG), which is an ideal attitude actuator for its large outputting control moment and fast response, the moving-gimbal effects due to the coupling between the moving gimbal and high-speeding rotor will make the magnetically suspended rotor (MSR) unstable. To improve control precision, both the dynamic model of MSR and the feedback linearization control are done to decouple tilting motion, and poles of the system are reconfigured to reduce control error. To suppress the varying disturbance moments caused by moving-gimbal effects, an extended state observer (ESO) is originally designed to estimate and compensate them timely and accurately. To improve system robustness, a two-degree freedom internal model control (2-DOF IMC) is researched to suppress model error. Compared with existing proportional integral derivative (PID) control method, simulations done on a single gimbal MSCMG with 200 N.m.s angular momentum indicated that this presented control method with ESO and 2-DOF IMC can suppress the moving-gimbal effects more effectively and make the rotor suspension more stable.

Commutation error rapid compensation for brushless DC motor based on DC‐link current phase extraction method

In order to reduce the torque ripple and running loss caused by the commutation error in the brushless DC motor (BLDCM) of the magnetically suspended control moment gyroscope (MSCMG), this study proposes a novel method dealing with commutation error in sensorless controlled BLDCM by rapid phase extraction and compensation technique. First, a traditional virtual neutral point circuit consisted of three-phase resistance network and low-pass filter are used to obtain the zero-crossing points of the non-conducting phase back electromotive force without noise interference. Then, an improved phase extraction method is built after analysing the DC-link current. Commutation error is extracted from DC-link current with the improved phase extractor rapidly. Furthermore, the effect of speed offset caused by fluctuation during phase extraction is also analysed and an adaptive commutation error compensation method based on the DC-link current phase extraction is proposed. Finally, simulation and experimental results performed on the high-speed motor of MSCMG verify its effectiveness and rapidity. The main novelties of this study are the direct phase extraction algorithm with natural parameter insensitivity and robustness and the rapid iterative commutation error compensation method based on the extraction algorithm.

Synchronous Force Elimination in the Magnetically Suspended Rotor System With an Adaptation to Parameter Variations in the Amplifier Model

For a magnetically suspended control moment gyro (MSCMG), the mass imbalance of the high-speed magnetically suspended rotor (MSR) will induce a synchronous force, which is the main disturbance for the attitude control of satellites. In this work, an elimination method with an adaption to parameter variations in an amplifier model is presented. First, the MSR system with a hybrid magnetic bearing is modeled. Next, a generalized notch filter is utilized to identify the synchronous displacement, according to which a feedforward controller is designed to generate synchronous current so that the electromagnetic force can counteract the permanent magnetic force precisely. To keep the feedforward controller unaffected by the power amplifiers whose parameters vary with the temperature, another notch filter is adopted to obtain the synchronous coil current, and then two types of adaptive controllers, which can tune the synchronous feedforward controller adaptively, are proposed and compared. Finally, simulations and experiments are carried out to demonstrate the validness of the adaptive control methods in an MSCMG test rig. The proposed control strategy does not need an accurate MSR model, and the methods of adaption to parameter variations in the amplifier model are suitable for various applications according to the elimination precision and computational effort.

High-Precision Speed Control Based on Multiple Phase-Shift Resonant Controllers for Gimbal System in MSCMG

The high precision speed control of gimbal servo system in magnetically suspended control moment gyro (MSCMG) suffers from periodic torque disturbances, which lead to periodic fluctuations in speed control. This paper proposes a novel multiple phase-shift resonant controller (MPRC) for a gimbal servo system to suppress the periodic torque ripples whose frequencies vary with the operational speed of the gimbal servo motor and high-speed motor. First, the periodic torque ripples caused by cogging torque, flux harmonics and the dynamic unbalance of the high speed rotor are analyzed. Second, the principle and structure of MPRC parallel with proportional integral (PI) controllers are discussed. The design and stability analysis of the proposed MPRC plus PI control scheme are given both for the current loop and speed loop. The closed-loop stability is ensured by adjusting the phase in the entire operational speed range. Finally, the effectiveness of the proposed control method is verified through simulation and experimental results.

Weight-Reduction Design Based on Integrated Radial-Axial Magnetic Bearing of a Large-Scale MSCMG for Space Station Application

For space application, weight and power consumption are the key parameters of an actuator for attitude control of spacecraft. In this paper, weight-reduction design based on a novel combined radial-axial magnetic bearing (CRAMB) in a large-scale magnetically suspended control moment gyro (MSCMG) for space station application is proposed. The CRAMB consists of a radial magnetic bearing (RMB) unit and an axial magnetic bearing (AMB) unit. Two CRAMBs can control the 5-degrees of freedom of the high-speed magnetically suspended rotor. According to the requirement of a large MSCMG for a space station, the CRAMB with permanent magnet bias is modeled (based on an equivalent magnetic circuit method), designed, and tested. Compared with the original magnetic bearings in MSCMG fabricated, the number of magnetic pole is reduced from eight to four for RMB unit based on the CRAMB, the weight of magnetic bearings can be reduced from 35.4 to 30.8 kg (reduced by 4.6 kg), and the volume is reduced from $\text{0.00456}$ to $\text{0.00394}\; \text{m}^{3}$ (reduced by 16.3%), when the MSCMG outputs the same angular momentum of 1200 N · m · s and the same torque of 209 N·m. The maximum power consumption of the proposed CRAMB system is decreased by 15.6%.

Feedback Linearization and Extended State Observer-Based Control for Rotor-AMBs System With Mismatched Uncertainties

To effectively reject the influence of moving gimbal effect and parameter variation on the control performance of the rotor-active magnetic bearings (AMBs) system in a double gimbal magnetically suspended control moment gyro (MSCMG), this paper proposes a feedback linearization and extended state observer (ESO) based control (FLESOBC) strategy, which can attenuate the matched and mismatched system uncertainties simultaneously. First, considering the voltage-type power amplifier used in the MSCMG for space applications, the rotor dynamics is modeled completely and then rearranged into translation and tilt motion subsystems according to modal separation control, where the lumped system uncertainties are adopted to represent the external disturbances and the parameter variations. Then, feedback linearization based on differential geometry theory is performed to transform the original system into the integral chain pseudo-linear system, making the mismatched uncertainties in the same channel as the new virtual input. Afterwards, the ESO is designed to estimate the lumped uncertainties. To combine the merits of compensation control and robust control, a PIDD controller (PID with second order differential) is designed to guarantee the closed loop stability and avoid the power amplifier saturation. Finally, simulations and experiments are carried out to demonstrate the effectiveness of the proposed method.