Zhong-he Jin’s research while affiliated with Zhejiang University and other places

Concentrating on the high frequency aerospace demand of solid‐state power amplifier (SSPA), this paper presents the methodology and key technique of a W‐band 3‐W SSPA that achieves high efficiency while maintaining excellent reliability capability. An improved Magic‐T power combiner is utilized to achieve high output power, and eliminate the influence of the parallel end‐stage gallium‐nitride high‐electron‐mobility‐transistor (GaN HEMT) PAs by its good isolation performance. The SSPA's millimetre‐wave circuit is implemented by three stages of amplifier, to realized more than 30‐dB power gain. The power‐supply circuit based on the two‐transistor forward topology is proposed for voltage converting and output serious sequence controlling. The SSPA is fabricated and measured, achieving 33‐dBm to 34.1‐dBm output power within the frequency range of 92–96 GHz, with the power gain of 31–32 dB, and peak efficiency of 7.1%, respectively. The proposed SSPA shows competitive performance for space application.

An artificial intelligence enhanced star identification algorithm is proposed for star trackers in lost-in-space mode. A convolutional neural network model based on Vgg16 is used in the artificial intelligence algorithm to classify star images. The training dataset is constructed to achieve the networks’ optimal performance. Simulation results show that the proposed algorithm is highly robust to many kinds of noise, including position noise, magnitude noise, false stars, and the tracker’s angular velocity. With a deep convolutional neural network, the identification accuracy is maintained at 96% despite noise and interruptions, which is a significant improvement to traditional pyramid and grid algorithms.

Infrared Earth sensors are widely used in attitude-determination and control systems of satellites. The main deficiency of static infrared Earth sensors is the requirement of a small field of view (FOV). A typical FOV for a static infrared Earth sensor is about 20° to 30°, which may not be sufficient for low-Earth-orbiting micro-satellites. A novel compact infrared Earth sensor with an FOV of nearly 180° is developed here. The Earth sensor comprises a panoramic annular lens (PAL) and an off-the-shelf camera with an uncooled complementary-metal-oxide-semiconductor (CMOS) infrared sensor. PAL is used to augment FOV so as to obtain a complete infrared image of the Earth from low-Earth-orbit. An algorithm is developed to compensate for the distortion caused by PAL and to calculate the vector of the Earth. The new infrared Earth sensor is compact with low power consumption and high precision. Simulated images and on-orbit infrared images obtained via the micro-satellite ZDPS-2 are used to assess the performance of the new infrared Earth sensor. Experiments show that the accuracy of the Earth sensor is about 0.032°.

An ammonia self-managed vaporization propulsion (ASVP) system for micro-nano satellites is presented. Compared with a normal cold gas or liquefied gas propulsion system, a multiplex parallel sieve type vaporizer and related vaporization control methods are put forward to achieve self-managed vaporization of liquefied propellant. The problems of high vaporization latent heat and incomplete vaporization of liquefied ammonia are solved, so that the ASVP system takes great advantage of high theoretical specific impulse and high propellant storage density. Furthermore, the ASVP operation procedure and its physical chemistry theories and mathematical models are thoroughly analyzed. An optimal strategy of thrust control is proposed with consideration of thrust performance and energy efficiency. The ground tests indicate that the ASVP system weighs 1.8 kg (with 0.34-kg liquefied ammonia propellant) and reaches a specific impulse of more than 100 s, while the power consumption is less than 10 W. The ASVP system meets multiple requirements including high specific impulse, low power consumption, easy fabrication, and uniform adjustable thrust output, and thus is suitable for micro-nano satellites.

To overcome the shortcomings of the traditional measurement error calibration methods for spaceflight telemetry, tracking and command (TT&C) systems, an online error calibration method based on low Earth orbit satellite-to-ground doubledifferential GPS (LEO-ground DDGPS) is proposed in this study. A fixed-interval smoother combined with a pair of forward and backward adaptive robust Kalman filters (ARKFs) is adopted to solve the LEO-ground baseline, and the ant colony optimization (ACO) algorithm is used to deal with the ambiguity resolution problem. The precise baseline solution of DDGPS is then used as a comparative reference to calibrate the systematic errors in the TT&C measurements, in which the parameters of the range error model are solved by a batch least squares algorithm. To validate the performance of the new online error calibration method, a hardware-in-the-loop simulation platform is constructed with independently developed spaceborne dual-frequency GPS receivers and a Spirent GPS signal generator. The simulation results show that with the fixed-interval smoother, a baseline estimation accuracy (RMS, single axis) of better than 10 cm is achieved. Using this DDGPS solution as the reference, the systematic error of the TT&C ranging system is effectively calibrated, and the residual systematic error is less than 5 cm.

In order to study the influence of lightweight flexible appendages vibration (LFAV) and liquid fuel sloshing (LFS) on the micro- and nano-satellite, based on ZDPS-2 satellite of Zhejiang University, this paper develops a kind of attitude dynamics which considers flexible appendages vibration and liquid sloshing. An adaptive prediction backstepping controller (APBC) is designed under the consideration of estimation error of the moment of inertia, the flexible vibration, liquid fuel sloshing and disturbance torques. Also time delay problem is considered in this algorithm. The finite time convergence is performed using Lyapunov stability method. Numerical simulations are carried out to verify the validity of the proposed controller. The results show that compared with the traditional PD controller, under the same attitude measurement error, the APBC has good control performance on eliminating the effect of time delay and provides estimations of moment of inertia parameters online. It can also significantly decrease the magnitude of the flexible appendages vibration and liquid sloshing.

A spacecraft’s separation parameters directly affect its flying trace. If the parameters exceed their limits, it will be difficult to adjust the flying attitude of the spacecraft, and the spacescraft may go off-track or crash. In this paper, we present a composite optimization method, which combines angular velocities with external moments for separation parameters of large-eccentricity pico-satellites. By changing the positions of elastic launch devices, the method effectively controls the popping process under the condition of less change in the separation mechanism. Finally, the reasons for deviation of angular velocities and unreliable optimization results are presented and analyzed. This optimization method is proved through a ground test which offsets the gravity. Simulation and test results show that the optimization method can effectively optimize the separation parameters of large-eccentricity pico-satellites. The proposed method adapts particularly to the fixed and non-stable status elastic parameters, the distribution of all kinds of elastic devices, and large-eccentricity spacecrafts for which attitude corrections are difficult. It is generally applicable and easy to operate in practical applications. © 2018, Zhejiang University and Springer-Verlag GmbH Germany, part of Springer Nature.

Because of their volume and power limitation, it is difficult for CubeSats to configure a traditional propulsion system. Atmospheric drag is one of the space environmental forces that low-orbit satellites can use to realize orbit adjustment. This paper presents an integrated control strategy to achieve the desired in-track formation through the atmospheric drag difference, which will be used on ZJUCubeSat, the next pico-satellite of Zhejiang University and one of the participants of the international QB50 project. The primary mission of the QB50 project is to explore the near-Earth thermosphere and ionosphere at the orbital height of 90–300 km. Atmospheric drag cannot be ignored and has a major impact on both attitude and orbit of the satellite at this low orbital height. We conduct aerodynamics analysis and design a multidimensional nonlinear constraint programming (MNLP) strategy to calculate different desired area–mass ratios and corresponding hold times for orbit adjustment, taking both the semimajor axis and eccentricity into account. In addition, area–mass ratio adjustment is achieved by pitch attitude maneuver without any deployable mechanism or corresponding control. Numerical simulation based on ZJUCubeSat verifies the feasibility and advantage of this design.

The noise of closed loop micro-electromechanical systems (MEMS) capacitive accelerometer is treated as one of the significant performance specifications. Traditional optimization of noise performance often focuses on designing large capacitive sensitivity accelerometer and applying closed loop structure to shape total noise, but different noise sources in closed loop and their behaviors at low frequencies are seldom carefully studied, especially their behaviors with different electronic parameters. In this work, a thorough noise analysis is established focusing on the four noise sources transfer functions near 0 Hz with simplified electronic parameters in closed loop, and it is found that the total electronic noise equivalent acceleration varies differently at different frequency points, such that the noise spectrum shape at low frequencies can be altered from 1/f noise-like shape to flat spectrum shape. The bias instability changes as a consequence. With appropriate parameters settings, the 670 Hz resonant frequency accelerometer can reach resolution of $2.6 \mu g/\sqrt {Hz}$ at 2 Hz and 6 μg bias instability, and 1300 Hz accelerometer can achieve $5 \mu g/\sqrt {Hz}$ at 2 Hz and 31 μg bias instability. Both accelerometers have flat spectrum profile from 2 Hz to 15 Hz.