Reaction Flywheel Research Articles

Commutation Point Optimization Method for Sensorless BLdc Motor Control Using Vector Phase Difference of Back EMF and Current

Commutation error is a crucial factor that reduces the efficiency of brushless dc (BLdc) motors. This article presents a commutation point optimization method for a sensorless BLdc motor. First, the sources of commutation error under position sensorless control are analyzed, and a conclusion is drawn that the phase difference between the back electromotive force vector and phase current vector equals the total commutation error. Second, a fundamental waveform extractor is used to eliminate the influence of harmonics on the equivalent commutation error. Third, the phase difference of the fundamental waveforms is extracted by a combined phase-locked loop, and the real-time commutation error is obtained consequently. Finally, accurate commutation is achieved by compensating for the phase difference, and experimental results on a reaction flywheel prototype evaluate the presented method.

Dawn of clean energy: Enhanced heat transfer, radiative cooling, and firecracker-style controlled nuclear fusion power generation system

Global climate change has become a major environmental threat and development challenge facing humanity. Controllable nuclear fusion is a globally recognized ideal solution for clean energy, but its required high-energy triggering conditions and intense energy release prevent existing technologies from achieving safe, stable, and long-term continuous operation. Here, inspired by the traditional Chinese firecrackers, we propose a pulsed fusion reaction flywheel energy storage multi-reactor relay operation to drive the steam turbine to continuously and stably generate electricity for a long period of time; meanwhile, to install cleaning rotors in the cooling medium pipeline to enhance heat exchange, and to apply radiative cooling technology on the surface of the cooling tower to improve cooling efficiency and to reduce energy consumption, thereby improving system safety and overall energy efficiency. Proposing the combination of original technologies at both the hot end and the cold end of the system, we strive to open up a new way for controllable nuclear fusion power generation.

The Design of a Reaction Flywheel Speed Control System Based on ADRC

The reaction flywheel is a crucial operational component within a satellite’s attitude control system. Enhancing the performance of the reaction flywheel speed control system holds significant importance for satellite attitude control. In this paper, an active disturbance rejection control (ADRC) approach is introduced to mitigate the impact of uncertain disturbances on reaction flywheel speed control precision. The reaction flywheel speed control system is designed as an ADRC controller due to the current challenge of measuring unknown disturbances accurately in the reaction flywheel system. To derive the rotor’s speed observation value and the estimated total disturbances value, the sampled data of the reaction flywheel rotor position and torque control signal are fed into the extended state observer. The estimated total disturbances value is compensated on feedforward control, which could mitigate significantly the effects of various nonlinear disturbances. The paper initially establishes the rationale behind the reaction flywheel ADRC controller through theoretical analysis, followed by analysis of the differences of performance of reaction flywheel control by the ADRC controller and the PID controller in MATLAB/SIMULINK. Simulation results demonstrate the evident advantages of the ADRC controller over the PID controller in terms of speed command tracking capability and disturbances suppression ability. Subsequently, the ADRC controller program and the PID controller program are implemented on the reaction flywheel control circuit, and experiments are conducted to contrast speed command tracking and disturbance suppression. Importantly, the experimental outcomes align with the simulation results.

Loss Estimation and Thermal Analysis of a Magnetic Levitation Reaction Flywheel with PMB and AMB for Satellite Application

The magnetic levitation reaction flywheel (MLRW) is a novel actuator of spacecraft attitude control because of its significant advantages, including lack of friction and active suppression of vibration. However, in a vacuum environment, the poor heat dissipation conditions make it more sensitive to various losses and rises in temperature. Therefore, increasing temperature is the key issue for components used in space. In this study, the losses of the three kinds of heat-generating areas in the MLRW, namely, the passive magnetic bearing (PMB), the active magnetic bearing (AMB) and brushless DC motor (BLDCM), were analyzed and calculated. Based on the electromagnetic field theory, the loss model of PMB was proposed. Based on the finite element method (FEM) and Bertotti model, the loss power of the AMB and the BLDCM was obtained. The calculated loss values were brought into the FEM to calculate the temperature field distribution of the MLRW system. Then, the key factors affecting the heat dissipation of the flywheel were obtained by combining thermal network analysis with the temperature field distribution. Finally, a prototype was fabricated. The maximum estimated and experimental temperatures were 34.8 °C and 36.8 °C, respectively, both at the BLDCM stator. The maximum error was 5.4%, which validates the calculated model.

Simulink-based simulation platform design and faults impact analysis of attitude control systems

AbstractThe satellite attitude control system (SACS) is a complicated system. In order to reflect the relationship among different components in SACS and analyse the impact of component faults on system performance, a complete simulation platform of the SACS based on Simulink is built in this paper. With the embedding of the specific reaction flywheel, gyroscope and earth sensor model, and the design of the controller based on the quaternion feedback, the simulation platform can not only simulate the real SACS at the component level, but it can also realise the injection of component faults for analysing the system performance. Simulations are conducted to verify the performance of the simulation platform. Simulation results show that this simulation platform has the ability to accurately reflect the control performance of the SACS, and the output accuracy of the component model is high. The research results reveal that this simulation platform can provide model support for verifying the algorithm of fault diagnosis, prediction and tolerant control of the SACS. This simulation platform is easy to use and can be expanded and improved.

A Data Fusion Fault Diagnosis Method Based on LSTM and DWT for Satellite Reaction Flywheel

This paper presents a novel fault diagnosis method based on data fusion for a reaction flywheel of the satellite attitude system. Different from most traditional fault diagnosis techniques, the proposed solution simultaneously accomplishes fault detection and identification within parallel fusion blocks. The core of this method is independent fusion block, which uses a generalized ordered weighted average (GOWA) operator to complement the characteristics of output data from long short-term memory (LSTM) neural network and discrete wavelet transform (DWT) so as to enhance the reliability and rapidity of decision-making. Moreover, minibatch normalization is selected to address the problem of covariate shift, realize the adaptive processing of the dynamic information in the original data, and improve the convergence speed of the network. With the high-fidelity model of the reaction flywheel, three common faults are, respectively, injected to collect experimental data. Extensive experiment results show the efficacy of the proposed method and the excellent performance achieved by LSTM and DWT.

Nano-Pico Satellite Actuator Fault Diagnosis Based on Adaptive Observer

This paper concerns with actuators fault diagnosis of nano-pico satellite, and a double adaptive estimation algorithm is proposed. Based on the non-linear mathematical model of reaction flywheel, a parameterized description method of flywheel fault type is established. Using the input and output information of the flywheel, a local adaptive observer is constructed and can identify the fault type of the flywheel. A global adaptive observer based on the satellite dynamics model uses the gyroscope sampling signal and the estimation of local observer as inputs, so failure moment of the other actuator can be identified. Combining two observers’ identification results, the fault diagnosis of flywheel and the other actuator can be completed. In this paper, a control system composed of reaction flywheel and magnetorquer is simulated. Results show the effectiveness of proposed method for nano-pico satellite actuator fault diagnosis.

Principle and experimental research on vibration reduction of flexible solar array using reaction flywheel

PurposeThe rest-to-rest movements for a spacecraft, such as attitude adjustment and orbital manoeuver, are likely to excite residual vibration of flexible appendages, which may affect the attitude accuracy and even result in severe structural damage. The purpose of this paper is to present an approach to attenuating the vibration of flexible solar array by using reaction flywheel.Design/methodology/approachThe reaction flywheel installed on solar array served as an actuator to provide reaction torque to a structure according to a designed feedback control law. This torque can be considered as an artificial damping. Experiment on a scale model of the solar array is first performed to verify the effectiveness of this method. Numerical simulation on finite element model of a full-scale solar array is subsequently carried out to confirm the validity of this method for practical engineering application.FindingsThe vibration suppression effect on the structure using a reaction flywheel is deduced by theoretical analysis. Results from both experiment and numerical simulation reveal that the efficiency of vibration attenuation is promoted.Research limitations/implicationsImprovements on control law are left for further study. Additionally, only the first-order bending vibration of the flexible solar array is attenuated, and further study is required for other types of vibration suppression.Practical implicationsAn effective method is proposed for spacecraft designers to actively suppress the vibration of the flexible solar array.Originality/valueA novel active vibration reduction scheme is proposed using a reaction flywheel to suppress vibration of the flexible solar array. This paper fulfils a source of theoretical analysis and experimental studies for vibration reduction measure design and provides practical help for the spacecraft designers.

Instantaneous Torque Control of Magnetically Suspended Reaction Flywheel

With the requirement of spacecraft attitude control accuracy, the reaction flywheel is demanded deliver higher precision torque. To improve the torque-output precision of the magnetically suspended reaction flywheel, a new torque control method is proposed. First, comprehensive analysis of torque ripple of brushless DC motor (BLDC) due to commutation and inactive phase diode freewheeling is presented. Second, in order to eliminate the diode freewheeling of the inactive phase, the modulation PWM_ON_PWM pattern is adopted. Third, compensation methods to attenuate the commutation torque ripple by modulating the switching-in phase during low-speed region and modulating switching-out phase during high-speed region are given. Upon this, calculation method of the commutation time is introduced. Finally, the experimental results show that the proposed methods can eliminate both commutation and non-commutation torque ripple efficiently.

A novel two-stage extended Kalman filter algorithm for reaction flywheels fault estimation

This paper investigates the problem of two-stage extended Kalman filter (TSEKF)-based fault estimation for reaction flywheels in satellite attitude control systems (ACSs). Firstly, based on the separate-bias principle, a satellite ACSs with actuator fault is transformed into an augmented nonlinear discrete stochastic model; then, a novel TSEKF is suggested such that it can simultaneously estimate satellite attitude information and actuator faults no matter they are additive or multiplicative; finally, the proposed approach is respectively applied to estimating bias faults and loss of effectiveness for reaction flywheels in satellite ACSs, and simulation results demonstrate the effectiveness of the proposed fault estimation approach.

Robust Fault-Tolerant Control for Satellite Attitude Stabilization Based on Active Disturbance Rejection Approach with Artificial Bee Colony Algorithm

This paper proposed a robust fault-tolerant control algorithm for satellite stabilization based on active disturbance rejection approach with artificial bee colony algorithm. The actuating mechanism of attitude control system consists of three working reaction flywheels and one spare reaction flywheel. The speed measurement of reaction flywheel is adopted for fault detection. If any reaction flywheel fault is detected, the corresponding fault flywheel is isolated and the spare reaction flywheel is activated to counteract the fault effect and ensure that the satellite is working safely and reliably. The active disturbance rejection approach is employed to design the controller, which handles input information with tracking differentiator, estimates system uncertainties with extended state observer, and generates control variables by state feedback and compensation. The designed active disturbance rejection controller is robust to both internal dynamics and external disturbances. The bandwidth parameter of extended state observer is optimized by the artificial bee colony algorithm so as to improve the performance of attitude control system. A series of simulation experiment results demonstrate the performance superiorities of the proposed robust fault-tolerant control algorithm.

Dynamic Modeling and Control of Flexible Hexapod Platform for Micro-Vibration Isolation and Precision Tracking

Micro vibrations, produced by reaction flywheels, coolers, driving motors and other moving parts in spacecrafts, will result in jitters and performance degradation of sensitive optical payloads, such as laser communication platforms, space telescopes and staring cameras. In this paper, one hexapod platform with flexible ball joints is employed to suppress vibrations and steer the payload in 6-degree-of-freedom (DOF). At first, dynamic modeling of the flexible hexapod platform with two-stage hybrid isolation struts is derived. Then, a composite control strategy is proposed for vibration isolation and precision tracking. Finally, the simulation study is presented to validate the proposed control strategy.

小卫星用反作用飞轮系统设计

According to the requirement of reaction flywheels in small satellites for small sizes, the design method for an armature size was proposed when the electrical motor was at a minimal volume, and a stator coreless reaction flywheel system was designed based on the method. To avoid the magnetic saturation, the multidisciplinary design optimization method was applied to the design of flywheel rotor and magnetic field of the motor. A optimization strategy combined with Exterior Penalty(EP) function and Sequential Quadratic Programming(SQP) was proposed to optimize the system as well. With optimization, the minimum mass and maximum air-gap magnetic flux density of the rotor were chosen as the objects, respectively, and the maximum equivalent stress, resonance frequency, the polar moment of inertia and the magnetic saturation were taken as constrains. Then, the software iSIGHT with finite element analysis (ANSYS) were integrated to achieve the optimization. Finally, a flywheel prototype was designed based on the optimal results. The results indicate that the total mass of the flywheel rotor has been decreased from 0.73 kg to 0.67 kg (reduced by 8.22%) and the flux density has been increased from 0.376 T to 0.401 T (increased by 6.65%). The optimal design method can improve the rationality of flywheel design, and will promote the progress of the miniaturization investigation of flywheel systems.

Back-Stepping Adaptive Attitude Control of Over-Actuated Spacecraft

A novel robust adaptive back-stepping control scheme for attitude maneuver of over-actuated spacecraft system with redundant reaction fly-wheels (RWs) is proposed. The robust adaptive controller based on back-stepping may achieve the high accuracy and speed of the attitude control for the rigid spacecraft with uncertain inertia matrix and bounded external disturbs. The Lyapunov functions are employed to analyze and prove the systems stability, so the fine and accuracy performances are ensured. The numerical simulation results verify the effectiveness and feasibility of the control schemes derived here using the MATLAB/SIMULINK software.

Sliding mode control of reaction flywheel-based brushless DC motor with buck converter

Reaction flywheel is a significant actuator for satellites’ attitude control. To improve output torque and rotational speed accuracy for reaction flywheel, this paper reviews the modeling and control approaches of DC–DC converters and presents an application of the variable structure system theory with associated sliding regimes. Firstly, the topology of reaction flywheel is constructed. The small signal linearization process for a buck converter is illustrated. Then, based on the state averaging models and reaching qualification expressed by the Lee derivative, the general results of the sliding mode control (SMC) are analyzed. The analytical equivalent control laws for reaction flywheel are deduced detailedly by selecting various sliding surfaces at electromotion, energy consumption braking, reverse connection braking stages. Finally, numerical and experimental examples are presented for illustrative purposes. The results demonstrate that favorable agreement is established between the simulations and experiments. The proposed control strategy achieves preferable rotational speed regulation, strong rejection of modest disturbances, and high-precision output torque and rotational speed tracking abilities.

The Speed Mode Synergetic Control Approach for Magnetic Suspended Reaction Flywheel

Random torque disturbances generated by magnetic bearings eccentric magnetic force have negative effects on the output torque precision of the magnetic suspended reaction flywheel(MSRFW). In order to eliminate the negative effects, dynamic models of flywheel system including motor and the buck DC-DC converter are established and a synergetic control approach for speed mode operation is presented. This approach uses PI controller for speed operation and uses synergetic control theory to control the winding current of motor and the input current and output voltage of power converter, improving the robustness of the basic synergetic method in overcoming the random torque disturbance. Sufficient condition for synergetic control subsystem is certified by Lyapunov stability theory. Simulation and experimental results show that the presented approach has great robustness in torque disturbance and the output moment precision of the reaction flywheel system reaches up to 3 ×10 −5 N ·m.

Design of the Reaction Flywheel System Based on Axial-flux Motor

To satisfy the requirements of miniaturization for attitude control unit in distributed small satellite system(DSSS),a reaction flywheel system based on axial-flux motor is presented.The three-dimensional distribution of air-gap magnetic field is analyzed by using the finite element method(FEM).A computational model for back-EMF of the motor is established based on the printed circuit board(PCB) winding.The multidisciplinary design optimization method is applied to optimize the main structure size of the flywheel rotor to minimize the weight of the flywheel system while meeting the requirements of strength,stiffness and the air-gap flux density under the premise of using sequential quadratic programming(NLPQL).The total mass of the flywheel rotor is decreased from 0.899 kg to 0.741 kg(namely reduced by 17.6%) after optimization.A flywheel prototype is designed based on the optimal results and the no-load performance is tested.The results show that the maximum error between the calculated and measured values of back-EMF is 9.7%,which verifies the correctness of the design method and provides an important reference in the miniaturization design of reaction flywheel system.

Study on Trajectory Planning of Dual-arm Space Robot Keeping the Base Stabilized

Aiming at the case that the base is required to be stabilized by a balance arm when a dual-arm space robotic system is performing on-orbit missions, we propose coordinated trajectory planning methods of two typical applications — keeping the base centroid fixed (approximately; the same below), and keeping the base attitude and centroid position fixed synchronously. Firstly, the concept of “system centroid equivalent manipulator” is presented, and its kinematic model is derived. Based on the resolution of the position-level kinematic equation, the trajectory of the balance arm for stabilizing the base centroid is planned. Secondly, by combining with the control of a reaction flywheel, the base attitude and centroid can be kept fixed at the same time. The desired angular speed of the flywheel is determined according to the angular momentum conservation law. Finally, a multi-body dynamic model of a dual-arm space robotic system is developed and simulation study is carried out. The proposed methods can overcome the singularity problem which is un-avoidable for previous approaches based on differential kinematics. Furthermore, there are not special requirements on the mass properties and installation position of the balance arm. Simulation results have verified the proposed methods.

微纳卫星姿态控制系统的精细抗干扰容错控制方法

It is difficult to diagnose and accommodate the faults if disturbances and faults exist simultaneously in the controlled plants. This paper concerns the time-varying fault diagnosis problem for the attitude control system of microsatellites. First of all, a fault diagnosis observer for abrupt fault of the reaction flywheel is designed. In order to reject the disturbance of vibration from the reaction flywheel, a disturbance observer should be designed. Then a subtle fault diagnosis and tolerant control method is presented for the attitude control system including the parameter uncertainties due to the moment-of-inertia variation of microsatellites, fault of the reaction flywheel and the disturbance of vibration from the reaction flywheel simultaneously. A composite fault tolerant controller is constructed by integrating a fault accommodation from diagnosis observer with additional disturbance rejection and attenuation performance for two different types of disturbances. Then the fault can be accommodated and the multiple disturbances can be rejected and attenuated simultaneously. As a result, the controller can be easily solved via convex optimization based on linear matrix inequality. Simulations for an attitude control system of microsatellites are given to demonstrate that the fault can be accommodated readily and the disturbances can be rejected and attenuated simultaneously.

Design and Research of a Microgravity Floating Target Satellite System

In order to study the control method of position and attitude of the satellite, a simulation platform is built. The quality characteristics of the target satellite system and the reaction flywheel system are analyzed. The dynamic model of target satellite is built to study its dynamic character. Based on the CAMSHIT algorithm, the attitude and position of the target satellite is measured, and the control method of position and attitude is established by use of jet device and the reaction flywheel. The effectiveness and accuracy of the position and attitude control method are verified by the experiments.