Recently, the control moment gyroscopes have been widely used in spacecraft attitude control. In order to reduce the influence of the vibration caused by the highspeed momentum wheel, a vibration isolation device is introduced. However, vibration isolating device has an effect on the dynamic characteristics of the internal mechanism of the control torque gyroscope. This paper establishes a dynamic model of the control moment gyroscope with the influence of the flexible vibration isolation mechanism. The kinematic relationship is established by Euler angle transformation, and the dynamic characteristics are established by using the energy method. Numerical simulation and analysis are carried out in Matlab. It is found that the vibration isolation structure has an influence on the output torque of the gyroscope. The gyro moment under the flexible support has obvious fluctuation, and the fluctuation range increases with the increase of the rotational speed of the momentum wheel. At the same time, the flexible vibration isolation mechanism also generates the disturbance torque, which has a great influence on the control of the frame motor.

The smallscale agile satellite using single gimbal control moment gyroscope(SGCMG) as the actuator has singular state that obstructs continuous changes of the total angular momentum vector during the attitude maneuver. This paper transforms the singular problem into a dynamic control problem with state constraints in the view of overall attitude control system. The implementation of singular circumvention is based on control variable parameterization(CVP) method to obtain an optimal trajectory. This algorithm divides gimbal angular speed programming into piecewise linear in the largeangle attitude maneuver task. There is no complicated requirement for the algorithm design of the gimbal servo system. It results in benefit of resources saving that simple acceleration and deceleration control is implemented on gimbal system. In the process of trajectory planning, the constraints in engineering are taken into consideration. An optimal trajectory that comprehensively considers energy resources and target accuracy can be planned according to the requirements of the attitude maneuver task. The simulation results show that the algorithm achieves a gentle change of the attitude parameters and the satellite angular velocity trajectory. The maneuvering error is in the order of 1×10-3. The satellite runs stably and SGCMG does not have singularity during the maneuvering process.

 For a kind of flexible hinge with adjustable spring stiffness, which is used to connect small spacecraft and solar panels, the influence of damping on the vibration response of flexible hinge plate system in hinge structure is studied, including hinge stiffness and friction of hinge rotating pair. Firstly, a piezoelectric flexible hinged flexible plate experimental platform is established. The piezoelectric sensor and laser displacement sensor are used to detect vibrations, and a piezoelectric actuator is used for persistently exciting vibration. Then, experiments are carried out on vibration modal analyses under external excitation and driven via the piezoelectric actuator, under the conditions of different torsional stiffness of the flexible hinge. The experimental results show that the stiffness and the friction damping factor of the rotating pair of the flexible hinge will affect the natural frequency and damping ratio of the fundamental frequency vibration of the flexible hinged plate system. The experimental results provide a reference for analyzing the hinge influence characteristics of flexible hinged plates.

Bearings are the core components of space inertial actuators such as flywheel and Control Moment Gyros (CMG), and their operating status directly affect the performance and service life of the whole machine. At present, since that lightload bearings may produce a phenomenon like weak fault characteristics during normal operation, it is difficult to identify the normal and weak fault states for a single fault characteristic parameter. Aiming at this problem, this paper proposes a vibration fault clustering fusion method for bearing weak fault identification. First, the data are obtained through the bearing vibration experiment. Then, the characteristic parameters of the vibration signal are extracted based on the characteristic frequency ratio. On this basis, the KMedoids algorithm is used to cluster normal samples, and the safe boundary of normal operation is constructed according to the 3σ rule. Finally, the overrun probability of different bearing fault data are calculated, and the fault state is identified according to the probability. The results show that this method is feasible and effective for the identification of normal and weak faults of bearings.

In the present paper, the measured signal of vibration system is denoised based on Wavelet Packet analysis, which has the properties of both time and frequency analysis. In the denoising process, the compromised threshold wavelet denoising method is adopted, which has the advantage of both the soft threshold and the hard threshold of the wavelet denoising method. Due to the compromised factor, flexible handling in analyzing the signals is permitted. By using timeenergy Wavelet Spectrum analysis to the denoised signal, the principal component is clearly shown. Based on the calculated energy distribution on the frequency domain, the characters of the signal are displayed clearly, which provides a theoretical method for fault diagnosis and fault identification of mechanical vibration system. Thus, the developed analytical method in the present paper has broad application in the fault diagnosis and fault identification of mechanical vibration system and its components.

 Hardwareintheloop simulation system of aerospace operation is one of the common methods for simulating an aerospace environment to verify the availability of aerospace technology on the ground. However, it is inevitable that the time delay in the system results in distortion and energy divergence. In order to solve this problem, a dynamic model of aerospace collision and a force compensation model based on stiffness identification are established from two aspects: hysteresis of force measurement system and dynamic response delay of control system. Compensation algorithm based on directional projection of measuring force that identify the collision direction and contact stiffness is proposed, and then the result of force compensation is added to the position control compensation of the serial hardwareintheloop simulation mechanism. The feasibility of the force compensation method is verified and the reproduction accuracy of the system is improved by the digital simulation of singledegreeoffreedom collision of the serial hardwareintheloop simulation mechanism. Compensation model is established from the cause of force generation, which provides a new solution about the distortion problem of the hardwareintheloop aerospace operation simulation system.

Space robotic arms are important actuators in onorbit serving (OOS) missions and the performance of joint servo systems largely affect overall performance of robotic arm motion control systems. Current loop is the innermost part in the nested loop structure of joint servo system and highperformance motion control systems demand current loop that has fast dynamic response, low overshoot and parameter robustness. In this paper, a highorder deadbeat current predictive control method is proposed. Simulation results show that, compared with conventional PI controllers, this method can increase the system bandwidth and push the dynamic response time to its theoretical limit; when compared with conventional deadbeat control method, this method is more robust under resistance and magnetic flux variation and shows satisfactory dynamic and steadystate performance under parameter mismatch.

In order to further improve the positioning accuracy of the ultrasonic motor and meet the urgent needs of the aerospace drive mechanism for high positioning accuracy, the flexible shaft is used to improve the operating stability of the ultrasonic motor. Based on the transient response characteristics of the motor, the highprecision positioning of the ultrasonic motor is realized. The ultrasonic motor has the characteristics of fast response and the possibility of achieving high positioning accuracy. However, due to the unclear stepping characteristics and large fluctuations in operation, its potential has not yet been fully utilized. To solve this problem, first explore the stepping characteristics of the ultrasonic motor to obtain the stepping law of the motor under different load torques, and then use a continuous mode and stepping mode combined control strategy to achieve the highprecision positioning characteristics of the ultrasonic motor. The results of the study show that after the flexible shaft is adopted, the stepping fluctuation of the motor is greatly reduced, the positioning accuracy of the motor can reach 0.48 ″, and the costed time is less than 1.34 s.

 A new cholesterol based phosphate ionic liquid (［Col］［DBP］) is firstly synthesized. This ionic liquid is characterized by structural and physicochemical property analyses. The results indicate that ［Col］［DBP］ possesses high thermal stability and can be soluble in synthetic hydrocarbon oil (MAC). By comparison ［Col］［DBP］ with two oil soluble ionic liquids ［P88816］［DOSS］ and ［P8888］［DEHP］, the tribological properties of three ionic liquids as additives in MAC on two tribopairs (steel/PI and steel/PA) are investigated on vacuum ballondisc friction tester. The results indicate that three oil soluble ionic liquids exhibit excellent antiwear performances on steel/PI contact. What’s more, ［Col］［DBP］ shows the best antiwear property and ［P8888］［DEHP］ shows the best frictionreducing performance in this contact. For steel/PA contact, three ionic liquids as additives in MAC can not effectively reduce the friction and wear of MAC base oil. The worn surfaces are characterized by OM and three ionic liquids in MAC base oil and further the smoother worn surfaces are generated.

The research aims to investigate the tribological properties of composite bonded solid lubricating coatings under different curing methods. Composite epoxy solid lubricant coating is prepared by using epoxy resin as binder, molybdenum disulfide, graphite, alumina, and cerium fluoride as solid fillers. The curing tests of the composite bonded solid lubricating coating are conducted under microwave curing and thermal curing, by using white light interferometer to analyze the surface wear scar after the coating surface is worn. Scanning electron microscope (SEM) is used to analyze the worn scar and the unworn area. Energy dispersive Xray spectrometer (EDS) is used to analyze the surface of worn scar. The coefficient of friction (COF) of microwave curing in 10 minutes is 0.17, which is lower than 0.24 of thermal curing in 10 minutes. When the heat curing time increases to 30 minutes, the COF is close to that of microwave curing for 10 minutes. The fillers on the surface of heatcured coating agglomerate and the surface are rough and flake off after grinding. The surface of microwavecured coating is flake distribution and the surface are smooth after wear. SEM analysis shows that the wear pattern of heat cured coating is mainly abrasive wear, while the wear of microwave cured coating is slight, and the transfer film forms during the process of wear. EDS element analysis shows that the curing method had no effect on the dispersion of the coating.

The main goal of the bearing lubrication replenishment system is to achieve longterm, stable, and minimal lubricant supply to the flywheel bearing. The complex structure of the microporous medium may be effective to achieve this goal, but the current seepage mechanism and law are not yet clear. The main problems are that the porous media structure is difficult to control, the relationship between the porous structure and permeability is complex, and the permeability is affected by assembly pressure. The valve is generally made in two steps: first cold pressing the particulate matter, and then sintering the structure obtained by cold pressing to obtain the finished product. The current production process is mainly based on experience. The mechanism is unclear, and it is difficult to accurately control. In this paper, the Discrete Element Method and Lattice Boltzmann Method are combined numerically to study the permeability change of the particle packing structure during the cold pressing process. The Discrete Element Method is used to simulate the cold pressing process of the particle accumulation structure, and then the Lattice Boltzmann Method is used to simulate the seepage flow. The permeability change of the cold pressed structure under different friction angles is obtained. This study lays the foundation for a comprehensive disclosure of the relationship between the cold pressed structure of porous media and permeability and its microscopic mechanism.

The functional relationship between Clens structure parameters and point accuracy is given using the transfer matrix method. Based on this formula, the influence of structural parameters, including the distance d between the point of the incident fiber and the inclined surface, the refractive index of the Clens lens nl, the inclination angle θ between the optical end surface and the Clens end surface, the spherical curvature radius R and the length L, on the point accuracy are discussed. The calculation results show that when d is fixed, the adjustment ranges of R and L are both small. For example, when d is 0.2 mm, the changes of point accuracy caused by R and L are 0.019° and 0.03° respectively. This is because the focal length f is related to nl, R, and L and restricts each other, so that the point accuracy changes less. It is calculated that when the f is 0mm, 0.1mm, and 0.2mm respectively, the point accuracy corresponding to the maximum working distance is -0.493°, -0.257°, -0.03°.The reason is that among the parameters of R, L, and d, point accuracy can be changed effectively when at least any two of the parameters be changed at the same time. According to the point accuracy formula, the point accuracy of different types of Clens can be analyzed and a suitable optimization method can be obtained.