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Prof. Dr. Zheng Hong Zhu
Department of Mechanical Engineering, York University, 435C Bergeron Centre for Engineering Excellence, 4700 Keele Street, Toronto, ON M3J 1P3, Canada

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Research Keywords & Expertise

0 Dynamics and control of tethered spacecraft system and space robotics
0 Electrodynamic tether propulsion and space debris removal
0 Multi- functional materials
0 Additive manufacturing in space
0 Solid mechanics and finite element method

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Dynamics and control of tethered spacecraft system and space robotics

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Journal article
Published: 25 August 2021 in Acta Astronautica
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Spacecraft formation maneuvering will inevitably induce flexible vibration from flexible appendages of spacecraft such as solar array appendages or antennae, which leads to complex disturbances with unknown fundamental frequencies. To achieve high performance of spacecraft formation flying, a novel adaptive iterative learning disturbance observer based on adaptive notch filter is designed to estimate and compensate unknown multi-frequency disturbances. Different from existing results on iterative learning disturbance observer, the newly proposed observer can estimate effectively both low-frequency disturbances and high-frequency periodic disturbances. Based on the proposed observer, an output feedback pose tracking law is derived by combining the proposed velocity observer and a feedback controller in dual quaternions description. The stability of the closed-loop system is approved based on the Lyapunov framework. Finally, the effectiveness and accuracy of the proposed observer and controller are demonstrated successfully by numerical simulations.

ACS Style

Xiaoyu Zhu; Zheng H. Zhu; Junli Chen. Dual quaternion-based adaptive iterative learning control for flexible spacecraft rendezvous. Acta Astronautica 2021, 189, 99 -118.

AMA Style

Xiaoyu Zhu, Zheng H. Zhu, Junli Chen. Dual quaternion-based adaptive iterative learning control for flexible spacecraft rendezvous. Acta Astronautica. 2021; 189 ():99-118.

Chicago/Turabian Style

Xiaoyu Zhu; Zheng H. Zhu; Junli Chen. 2021. "Dual quaternion-based adaptive iterative learning control for flexible spacecraft rendezvous." Acta Astronautica 189, no. : 99-118.

Journal article
Published: 08 August 2021 in Aerospace Science and Technology
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This paper studies the control of libration stability of an insulated electrodynamic tether system in orbital boost. The electrodynamic tether is assumed rigid and the tethered spacecraft are modeled as lumped masses, while a complete electric circuit model is established by the Parker-Murphy model and Kirchhoff's first law. The electric current regulation is realized by adjusting the resistance of a resistor in the circuit. The impact of periodic variations of electrodynamic force on the libration of electrodynamic tether is minimized by a simple fuzzy-based continuous electric current control. The proposed controller maintains the merits of continuous electric current control and simplicity of on-off current control. The effectiveness of the fuzzy-based controller has been demonstrated by analyzing the libration dynamics of electrodynamic tether with continuous and discrete on-off current profiles in orbital boost. Numerical results show that the proposed approach is much effective than the on-off current control in stabilizing both in-plane and out-of-plane libration of the electrodynamic tether system subjected to periodic and non-periodic perturbations.

ACS Style

Jinyu Liu; Zheng H. Zhu; Gangqiang Li; Xingqun Zhan. Fuzzy-based continuous current control of electrodynamic tethers for stable and efficient orbital boost. Aerospace Science and Technology 2021, 118, 106999 .

AMA Style

Jinyu Liu, Zheng H. Zhu, Gangqiang Li, Xingqun Zhan. Fuzzy-based continuous current control of electrodynamic tethers for stable and efficient orbital boost. Aerospace Science and Technology. 2021; 118 ():106999.

Chicago/Turabian Style

Jinyu Liu; Zheng H. Zhu; Gangqiang Li; Xingqun Zhan. 2021. "Fuzzy-based continuous current control of electrodynamic tethers for stable and efficient orbital boost." Aerospace Science and Technology 118, no. : 106999.

Preprint content
Published: 06 July 2021
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This paper studies the deployment control of a spinning hub-spoke tethered satellite formation, which is a challenging issue due to the strong nonlinear coupling between the hub and sub-satellites, and the underactuated nature of the system if no thrust is used for control. The mathematical model of the formation system is established based on the assumption of rigid body of the hub, inextensible tether, and lumped masses of the sub-satellites. Two novel formation deployment controllers are proposed based on tension control and hybrid tension-thrust control strategies, where underactuated sliding mode control and nonsingular terminal sliding mode control method are used, respectively. The adaptive control theory is adopted to estimate the unknown upper bound of the gravitational perturbation caused by the rotation of the system around the hub. It can be proven by the Lyapunov theory that the close-loop systems have bounded and asymptotic stability under these two deployment controllers, respectively. Finally, numerical simulations are conducted to validate the effectiveness and robustness of the proposed controllers.

ACS Style

Chenguang Liu; Wei Wang; Junjie Kang; Zheng H. Zhu. Deployment of Hub-Spoke Tethered Satellite Formation with Adaptive Sliding Mode Tension Control. 2021, 1 .

AMA Style

Chenguang Liu, Wei Wang, Junjie Kang, Zheng H. Zhu. Deployment of Hub-Spoke Tethered Satellite Formation with Adaptive Sliding Mode Tension Control. . 2021; ():1.

Chicago/Turabian Style

Chenguang Liu; Wei Wang; Junjie Kang; Zheng H. Zhu. 2021. "Deployment of Hub-Spoke Tethered Satellite Formation with Adaptive Sliding Mode Tension Control." , no. : 1.

Journal article
Published: 12 June 2021 in Advances in Space Research
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This work proposes a novel hybrid control scheme to stabilize a partial space elevator with unknown tether tensions in cargo transportation. The tether tensions are first estimated by a new observing method. The control scheme contains two controllers. With the estimated tensions, Controller I predicts the optimal reference climber speed implemented by the actuator on the climber. When the climber is moving at the reference speed, a novel observer-based super twisting sliding mode control law is proposed for Controller II to eliminates possible disturbances and further stabilises the system in real-time. Simulation results reveal that with the observed tensions, the proposed hybrid control scheme is very effective and accurate in stabilizing the partial space elevator actuated by multiple actuators in the cargo transfer period.

ACS Style

Gefei Shi; Zheng H. Zhu; Gangqiang Li. Stable cargo transportation of partial space elevator with multiple actuators. Advances in Space Research 2021, 1 .

AMA Style

Gefei Shi, Zheng H. Zhu, Gangqiang Li. Stable cargo transportation of partial space elevator with multiple actuators. Advances in Space Research. 2021; ():1.

Chicago/Turabian Style

Gefei Shi; Zheng H. Zhu; Gangqiang Li. 2021. "Stable cargo transportation of partial space elevator with multiple actuators." Advances in Space Research , no. : 1.

Journal article
Published: 13 May 2021 in Acta Astronautica
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This paper describes the experimental validation of a CubeSat tether deployment design by air-bearing ground test and microgravity parabolic flight test. The tethered CubeSat mission includes two 1U CubeSats with a tape-type tether of 100 m. The tether will be deployed by pull with two CubeSats separating at a desired velocity. Various ground tests were performed to validate the designed separation velocity, estimate the internal friction force, and measure the deployed tether length. Finally, the engineering model of tether deployment system is validated by microgravity parabolic flight testing. The parabolic flight demonstrated the tether deployment system works as expected. By measuring the separation velocity of CubeSats in the parabolic flight, it reveals the internal friction is much less in the microgravity environment than the value measured on the ground.

ACS Style

Zheng H. Zhu; Junjie Kang; Udai Bindra. Validation of CubeSat tether deployment system by ground and parabolic flight testing. Acta Astronautica 2021, 185, 299 -307.

AMA Style

Zheng H. Zhu, Junjie Kang, Udai Bindra. Validation of CubeSat tether deployment system by ground and parabolic flight testing. Acta Astronautica. 2021; 185 ():299-307.

Chicago/Turabian Style

Zheng H. Zhu; Junjie Kang; Udai Bindra. 2021. "Validation of CubeSat tether deployment system by ground and parabolic flight testing." Acta Astronautica 185, no. : 299-307.

Preprint content
Published: 13 May 2021
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This paper studies the control of geometric profile of a librating electrodynamic tether by model predictive control using the induced electric current in tether only. First, a high-fidelity multiphysics model of an electrodynamic tether system is built based on the nodal position finite element method and the orbital-motion-limited theory. Second, a state estimator is proposed to estimate the geometric profile of a librating electrodynamic tether, where only the positions and velocities at the tether ends are measurable. The non-measurable geometric profile of tether between two ends is estimated by the high-fidelity multiphysics model with the input of the measurement at tether ends in the spatial domain. To avoid the singularity or ambiguity in the estimation, the geometric profile of tether is then propagated in the time domain by the extended Kalman filter. Third, the problem of controlling the geometric profile of a librating electrodynamic tether is converted into a trajectory tracking problem of the underactuated electrodynamic tether system, where the induced electric current in the tether is the only control input. The control input is optimized by the model predictive control method subject to the output and input control constraints. The numerical simulation results show that the proposed approach is capable of effectively controlling the shape of the liberating electrodynamic tether to the reference trajectory.

ACS Style

Gangqiang Li; Zheng H. Zhu. Model Predictive Control for Electrodynamic Tether Geometric Profile in Orbital Maneuvering with Finite Element State Estimator. 2021, 1 .

AMA Style

Gangqiang Li, Zheng H. Zhu. Model Predictive Control for Electrodynamic Tether Geometric Profile in Orbital Maneuvering with Finite Element State Estimator. . 2021; ():1.

Chicago/Turabian Style

Gangqiang Li; Zheng H. Zhu. 2021. "Model Predictive Control for Electrodynamic Tether Geometric Profile in Orbital Maneuvering with Finite Element State Estimator." , no. : 1.

Journal article
Published: 17 March 2021 in Acta Astronautica
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This paper explores a new control strategy to suppress the libration of a partial space elevator by applying torque control at the climber only. The control torque at the climber is generated by reaction wheels. A new dynamic model of the partial space elevator is developed by integrating the attitude dynamics of the climber into the classical two-piece dumbbell model. The influence of the climber attitude motion on the libration motion of the partial space elevator is analyzed with and without the control torque at the climber. Based on the characteristics of the system dynamics, a novel reaction wheel control strategy is proposed to suppress both the libration of the elevator and the climber attitude motion. Such a new control strategy is implemented by an optimal control scheme. The simulation results validate the effectiveness of the proposed control strategy, which provides a new alternative method to stabilize the libration of the partial space elevator for fast transfer of cargo with constant speeds. To avoid the adverse effect on the reaction wheel due to the frequent switch of rotation direction, a control strategy by two unidirectional reaction wheels is proposed to achieve the same control effect, where the reaction wheels rotate in only one direction.

ACS Style

Gefei Shi; Zheng H. Zhu; Gangqiang Li. Libration suppression of partial space elevator by controlling climber attitude using reaction wheel. Acta Astronautica 2021, 183, 126 -133.

AMA Style

Gefei Shi, Zheng H. Zhu, Gangqiang Li. Libration suppression of partial space elevator by controlling climber attitude using reaction wheel. Acta Astronautica. 2021; 183 ():126-133.

Chicago/Turabian Style

Gefei Shi; Zheng H. Zhu; Gangqiang Li. 2021. "Libration suppression of partial space elevator by controlling climber attitude using reaction wheel." Acta Astronautica 183, no. : 126-133.

Journal article
Published: 16 March 2021 in Acta Astronautica
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This paper investigates the tracking and control problem of a spacecraft rendezvous with a non-cooperative and tumbling space target subject to parametric uncertainty and unknown external disturbances. The kinematics and dynamics of spacecraft position and attitude are described by dual quaternions. A novel adaptive sliding mode disturbance observer is proposed to track the pose of non-cooperative tumbling target without need for upper bounds of first and second derivatives of lumped disturbance. Based on the proposed observer, a finite time sliding mode control is developed in term of dual quaternion. Different from existing sliding mode control schemes, the conditions on the controller parameters bounds are relaxed. The stability and robustness of the overall closed-loop control is proved by the Lyapunov framework. The robustness and effectiveness of the proposed control scheme are validated by numerical simulations in comparison with existing approaches.

ACS Style

Xiaoyu Zhu; Junli Chen; Zheng H. Zhu. Adaptive sliding mode disturbance observer-based control for rendezvous with non-cooperative spacecraft. Acta Astronautica 2021, 183, 59 -74.

AMA Style

Xiaoyu Zhu, Junli Chen, Zheng H. Zhu. Adaptive sliding mode disturbance observer-based control for rendezvous with non-cooperative spacecraft. Acta Astronautica. 2021; 183 ():59-74.

Chicago/Turabian Style

Xiaoyu Zhu; Junli Chen; Zheng H. Zhu. 2021. "Adaptive sliding mode disturbance observer-based control for rendezvous with non-cooperative spacecraft." Acta Astronautica 183, no. : 59-74.

Journal article
Published: 25 February 2021 in IEEE Transactions on Aerospace and Electronic Systems
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ACS Style

Junjie Kang; Zheng H. Zhu; Lucas F. Santaguida. Analytical and Experimental Investigation of Stabilizing Rotating Uncooperative Target by Tethered Space Tug. IEEE Transactions on Aerospace and Electronic Systems 2021, 57, 2426 -2437.

AMA Style

Junjie Kang, Zheng H. Zhu, Lucas F. Santaguida. Analytical and Experimental Investigation of Stabilizing Rotating Uncooperative Target by Tethered Space Tug. IEEE Transactions on Aerospace and Electronic Systems. 2021; 57 (4):2426-2437.

Chicago/Turabian Style

Junjie Kang; Zheng H. Zhu; Lucas F. Santaguida. 2021. "Analytical and Experimental Investigation of Stabilizing Rotating Uncooperative Target by Tethered Space Tug." IEEE Transactions on Aerospace and Electronic Systems 57, no. 4: 2426-2437.

Journal article
Published: 18 February 2021 in Advances in Space Research
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This paper proposes a novel finite element Kalman filter to estimate the unmeasurable state of space tether systems based on the measured state at its ends only. The finite element method calculates the unmeasurable internal state as the virtual measurement based on the dynamic model of the system by imposing the input of measured state at the boundary to the model using the Lagrange multiplier method in the spatial space. Combining the real and virtual measurement into a hybrid measurement model of the system, the full state is reconstructed and propagated in the temporal space by the extended Kalman filter. Two state-space system models, the dynamics-based and kinematics-based state models, in the Kalman filter are explored. The observability and stability of the newly proposed finite element Kalman filter are examined and proved. The advantages of the proposed state estimator are (i) the singularity in the virtual measurement of state caused by the number of internal state greater than the number of state measured at the boundary is eliminated in the statistic meaning by the Kalman filter, and (ii) the effects of noises of the observation data and the uncertainties of model discretization are considered and minimized. The correctness and effectiveness of the proposed state estimator is demonstrated by the numerical analysis of a space tether system orbiting around the Earth. The results show the proposed state estimator with only measured state at the ends of the tether successfully provides an accurate time history estimation of geometric configuration and motion of the entire tether. Moreover, the results also show the difference caused by the dynamics-based and kinematics-based system models in the state estimator is negligible. The kinematics-based system model should be used in the state estimator due to its significantly low computational load. Finally, the proposed method can be easily applied for the state estimation process for other space tethered spacecraft systems.

ACS Style

Gangqiang Li; Zheng H. Zhu. Estimation of flexible space tether state based on end measurement by finite element Kalman filter state estimator. Advances in Space Research 2021, 67, 3282 -3293.

AMA Style

Gangqiang Li, Zheng H. Zhu. Estimation of flexible space tether state based on end measurement by finite element Kalman filter state estimator. Advances in Space Research. 2021; 67 (10):3282-3293.

Chicago/Turabian Style

Gangqiang Li; Zheng H. Zhu. 2021. "Estimation of flexible space tether state based on end measurement by finite element Kalman filter state estimator." Advances in Space Research 67, no. 10: 3282-3293.

Journal article
Published: 06 February 2021 in Energy
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Self-powered electronic devices require energy harvesting systems to support their energy needs, but their energy harvesting efficiency seems still insufficient. In this paper, a flexoelectric energy harvester based on controllable wrinkling mechanism is theoretically proposed to enhance the energy harvesting efficiency. The dielectric film, partly bonded to a pre-stretched substrate, wrinkles after release to achieve controllable wavy shapes. A harmonic cyclic post-stretch is employed to stimulate the generation of electric charges. Meanwhile, an electrode-regrouping technique is resorted to optimize the energy harvesting efficiency. Formulation toward this problem includes both the flexoelectricity and piezoelectricity of dielectrics. Theoretical prediction indicates that electrode-regrouping technique can effectively act to relieve neutralization of the charges induced mainly by flexoelectricity and thus improve the energy harvesting efficiency of FEHs. A larger loading frequency and a lower resistance are preferred to optimize the effective power. The power density of the present FEHs is at least 1 orders of magnitude higher than that of vibrational FEHs under micro-scale. Meanwhile, with the scale shrinking below 100 nm, the energy density of the present FEHs may exceed 104W/m3 which is generally 2–4 orders of magnitude higher than that of most vibrational energy harvesters (including electrostatic, electromagnetic, piezoelectric types).

ACS Style

Shengkai Su; Huaiwei Huang; Zheng H. Zhu. Flexoelectric energy harvesters utilizing controllably wrinkled micro-dielectric film. Energy 2021, 224, 120056 .

AMA Style

Shengkai Su, Huaiwei Huang, Zheng H. Zhu. Flexoelectric energy harvesters utilizing controllably wrinkled micro-dielectric film. Energy. 2021; 224 ():120056.

Chicago/Turabian Style

Shengkai Su; Huaiwei Huang; Zheng H. Zhu. 2021. "Flexoelectric energy harvesters utilizing controllably wrinkled micro-dielectric film." Energy 224, no. : 120056.

Original paper
Published: 05 January 2021 in Nonlinear Dynamics
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The paper studies the stability and control of radial deployment of an electric solar wind sail with the consideration of high-order modes of elastic tethers. The electric solar wind sail is modeled by combining the flexible tether dynamics, the rigid-body dynamics of central spacecraft, and the flexible-rigid kinematic coupling. The tether deployment process is modeled by the nodal position finite element method in the arbitrary Lagrangian–Eulerian framework. A symplectic-type implicit Runge–Kutta integration is proposed to solve the resulting differential–algebraic equation. A proportional–derivative control strategy is applied to stabilize the central spacecraft’s attitudes to ensure tethers’ stable deployment with a constant spinning rate. The results show the electric solar wind sail requires thrust at remote units in the tangential direction to counterbalance the Coriolis forces acting on the tethers and remote units to deploy tethers radially successfully. The parametric analysis shows the tether deployment speed and the thrust magnitude significantly impacts deployment stability and tether libration, which opens the possibility of successful deployment of tethers by using optimal control. Finally, the analysis results show that radial deployment is advantageous due to the isolated deployment mechanism, and a jammed tether can be isolated from affecting the deployment of rest tethers.

ACS Style

Gangqiang Li; Zheng H. Zhu; Chonggang Du. Stability and control of radial deployment of electric solar wind sail. Nonlinear Dynamics 2021, 103, 481 -501.

AMA Style

Gangqiang Li, Zheng H. Zhu, Chonggang Du. Stability and control of radial deployment of electric solar wind sail. Nonlinear Dynamics. 2021; 103 (1):481-501.

Chicago/Turabian Style

Gangqiang Li; Zheng H. Zhu; Chonggang Du. 2021. "Stability and control of radial deployment of electric solar wind sail." Nonlinear Dynamics 103, no. 1: 481-501.

Journal article
Published: 13 December 2020 in Communications in Nonlinear Science and Numerical Simulation
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This paper investigates the modelling of rigid-flexible coupling effect on the attitude dynamics and spin control of an electric solar wind sail (E-sail) by developing a rigid-flexible coupling dynamic model. The model considers the attitude dynamics of the central spacecraft, the elastic deformation of the tethers and the rigid-flexible coupling between the spacecraft and the tether. The attitude and translation dynamics of the central spacecraft is described by the natural coordinate formulation, while the tether deformation is described by the high-fidelity nodal position finite element method. The latter enables a natural coupling between the motion of the flexible tethers and the rigid-body dynamics of the central spacecraft at the anchor points where the tethers connected to the spacecraft by Lagrange multipliers. Based on the model, the influence of the rigid-flexible coupling, E-sail orientation and geometrical configuration on the dynamic characteristics of the E-sail is investigated by a parametric analysis. It is found that the deformation motion of flexible tethers will cause the offset of centres of mass and thrust of E-sail, which generates disturbance torques on the central spacecraft. Through the nonlinear rigid-flexible coupling, the disturbance causes the tension fluctuations and the undesired fluctuations of the E-sail's attitude and spin rate. The parametric analysis indicates that the E-sail is more stable if the spin plane passes the centre of mass of the central spacecraft. Finally, the controllability of E-sail spin rate is investigated by applying simple feedback torque controls at the central spacecraft or at the central spacecraft and the remote units simultaneously. The analysis demonstrates the spin rate cannot be controlled by the central spacecraft along due to the rigid-flexible coupling and must be controlled at the remote units with finite control input.

ACS Style

Chonggang Du; Zheng H. Zhu; Gangqiang Li. Rigid-flexible coupling effect on attitude dynamics of electric solar wind sail. Communications in Nonlinear Science and Numerical Simulation 2020, 95, 105663 .

AMA Style

Chonggang Du, Zheng H. Zhu, Gangqiang Li. Rigid-flexible coupling effect on attitude dynamics of electric solar wind sail. Communications in Nonlinear Science and Numerical Simulation. 2020; 95 ():105663.

Chicago/Turabian Style

Chonggang Du; Zheng H. Zhu; Gangqiang Li. 2020. "Rigid-flexible coupling effect on attitude dynamics of electric solar wind sail." Communications in Nonlinear Science and Numerical Simulation 95, no. : 105663.

Journal article
Published: 07 December 2020 in Aerospace Science and Technology
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This paper studies an observer-based adaptive learning control for spacecraft attitude stabilization subject to actuator fault, parameter uncertainty and external disturbance. Specifically, a new Barrier Function-based Iterative Learning Observer is proposed to estimate the lumped disturbance. Unlike existing iterative learning observer scheme, the newly proposed observer allows the gain matrix to fluctuate in accordance with exact values of the estimation errors, which leads to the estimation errors converges to a predefined neighborhood of zero independent of the adaptive gain matrix in finite time. Then, a composite control law is developed for spacecraft attitude stabilization by combining the newly proposed observer with a robust feedback controller. The stability of the overall closed-loop control system is proved in the Lyapunov framework. Finally, the robustness and effectiveness of the proposed strategy is demonstrated by numerical simulation.

ACS Style

Xiaoyu Zhu; Junli Chen; Zheng H. Zhu. Adaptive learning observer for spacecraft attitude control with actuator fault. Aerospace Science and Technology 2020, 108, 106389 .

AMA Style

Xiaoyu Zhu, Junli Chen, Zheng H. Zhu. Adaptive learning observer for spacecraft attitude control with actuator fault. Aerospace Science and Technology. 2020; 108 ():106389.

Chicago/Turabian Style

Xiaoyu Zhu; Junli Chen; Zheng H. Zhu. 2020. "Adaptive learning observer for spacecraft attitude control with actuator fault." Aerospace Science and Technology 108, no. : 106389.

Journal article
Published: 10 November 2020 in Acta Astronautica
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This paper proposes a novel concept of looped tether transportation system with multiple climbers for highly efficient transportation of payloads. It is formed by connecting two parallel tether transportation systems or partial space elevators with multiple climbers per tether at upper and lower ends. A high-fidelity and accurate model for the system is built up to capture the high order flexural modes of tethers based on the nodal position finite element method in the arbitrary Lagrangian-Eulerian description. Numerical analysis is conducted to understand the dynamic characteristics of the looped tether transportation system compared to the tether transportation system with a single tether. The results show that the high-order flexural modes of tethers must be considered in the system's engineering analysis. The analysis also shows the interaction between two tethers caused by climbers on different tethers moving in different directions could be beneficial. It will reduce the overall libration of the system while keeping the magnitude of tether tension comparable to the tether transportation system with a single tether. In addition, the analysis of high order flexural modes of tether indicates that there exists a risk of tether collision in the payload transportation, which indicates again the necessity to include the high order flexural modes of tether in the analysis. Finally, the study shows the risk of tether collision could be avoided by optimizing the number of climbers per tether, the climber's moving profiles, and the distance between climbers using the optimal control methodology.

ACS Style

Gangqiang Li; Zheng H. Zhu; Gefei Shi. A novel looped space tether transportation system with multiple climbers for high efficiency. Acta Astronautica 2020, 179, 253 -265.

AMA Style

Gangqiang Li, Zheng H. Zhu, Gefei Shi. A novel looped space tether transportation system with multiple climbers for high efficiency. Acta Astronautica. 2020; 179 ():253-265.

Chicago/Turabian Style

Gangqiang Li; Zheng H. Zhu; Gefei Shi. 2020. "A novel looped space tether transportation system with multiple climbers for high efficiency." Acta Astronautica 179, no. : 253-265.

Journal article
Published: 13 October 2020 in Chinese Journal of Aeronautics
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This paper studies the libration and stabilization of a parallel partial space elevator system in circular orbits. The system is made up of two paralleled partial space elevators, each of which consists of one main satellite, one end body and a climber moving along the tether between them. The libration characteristics of the elevator are studied through numerical analysis by a new dynamic model, and a novel control strategy is proposed to stabilize the swing of the end body by projecting the climber speeds only. Optimal control method is used to implement the new control strategy in the case where the climbers move in opposite direction. The simulation results validate the effectiveness of the proposed control strategy whose application will neither sacrifice the transport efficiency nor exacerbate libration significantly.

ACS Style

Gefei Shi; Gangqiang Li; Zheng H. Zhu. Libration and end body swing stabilization of a parallel partial space elevator system. Chinese Journal of Aeronautics 2020, 34, 187 -199.

AMA Style

Gefei Shi, Gangqiang Li, Zheng H. Zhu. Libration and end body swing stabilization of a parallel partial space elevator system. Chinese Journal of Aeronautics. 2020; 34 (3):187-199.

Chicago/Turabian Style

Gefei Shi; Gangqiang Li; Zheng H. Zhu. 2020. "Libration and end body swing stabilization of a parallel partial space elevator system." Chinese Journal of Aeronautics 34, no. 3: 187-199.

Journal article
Published: 06 September 2020 in Acta Astronautica
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This paper investigates the dynamic characteristics of thrust-induced sail plane coning and attitude motion of an electric solar wind sail (E-sail) by considering high-order modes of flexible elastic tethers. The tethers of the E-sail are assumed elastic and discretized into inter-connected 2-noded tensile elements using the nodal position finite element method, while the central spacecraft and the remote units are simplified as lumped masses. The E-sail is assumed in the heliocentric ecliptic orbital plane at a distance of 1 au from the Sun. The influences of the propulsive force models and the initial E-sail orientation on the dynamic characteristics of the sail plane coning and attitude motion of E-sail are analyzed. The current work derives an analytic expression of the coning motion frequency under the assumption of small coning angle. Through parametric analyses, the current work shows that the magnitude of the propulsive force significantly influences the increment magnitude of the E-sail's orbital radius while has little effect on the angles of sail and thrust angles and the E-sail spin rate. The parametric analyses also show that the initial E-sail orientation significantly influences the thrust vector and the variation of sail angle. Finally, the relationships of the sail and thrust angles, as well as the dimensionless acceleration of the E-sail, are given in polynomial expressions by curve-fitting of simulation results of E-sails with the consideration of coning motion. The relationships are compared with the previous results of E-sails without including coning motion. It shows the coning motion has negligible effect on the macro dynamic behaviors of E-sail.

ACS Style

Chonggang Du; Zheng H. Zhu; Gangqiang Li. Analysis of thrust-induced sail plane coning and attitude motion of electric sail. Acta Astronautica 2020, 178, 129 -142.

AMA Style

Chonggang Du, Zheng H. Zhu, Gangqiang Li. Analysis of thrust-induced sail plane coning and attitude motion of electric sail. Acta Astronautica. 2020; 178 ():129-142.

Chicago/Turabian Style

Chonggang Du; Zheng H. Zhu; Gangqiang Li. 2020. "Analysis of thrust-induced sail plane coning and attitude motion of electric sail." Acta Astronautica 178, no. : 129-142.

Journal article
Published: 18 July 2020 in Acta Astronautica
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This paper studies the libration suppression of a moon-based partial space elevator in the Earth-Moon three-body system. The elevator is connected to the Moon surface by a tether and a space station is connected to the free end of tether as the end body. One or multiple climber(s) can move along the tether to transfer cargos between the Moon and the end body. A high-fidelity dynamic model is derived to describe the motion of the climber(s), the end body and the flexible tether by the combination of rigid body dynamics and nodal position finite element method. The validity of the proposed model and the effect of element discretization along the tether on the dynamic behaviour of the elevator are investigated through numerical simulations. To ensure the stability and satisfy the mission constraints in the cargo transfer period, an optimal control based on the high-fidelity model is employed to regulate the control input with limited magnitude. Case studies show that by adjusting the thrusts on the end body reasonably, the libration of the Moon-based partial space elevator can be suppressed with limited control input effectively.

ACS Style

Gefei Shi; Gangqiang Li; Zheng H. Zhu. Libration suppression of moon-based partial space elevator in cargo transportation. Acta Astronautica 2020, 177, 96 -102.

AMA Style

Gefei Shi, Gangqiang Li, Zheng H. Zhu. Libration suppression of moon-based partial space elevator in cargo transportation. Acta Astronautica. 2020; 177 ():96-102.

Chicago/Turabian Style

Gefei Shi; Gangqiang Li; Zheng H. Zhu. 2020. "Libration suppression of moon-based partial space elevator in cargo transportation." Acta Astronautica 177, no. : 96-102.

Journal article
Published: 04 March 2020 in Acta Astronautica
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This paper investigates spacecraft orbital boost maneuver by a fully insulated electrodynamic tether using a coupled multiphysics dynamic model that considers electric-magnetic-dynamic energy coupling. The current-potential characteristics of the electrodynamic tether is described by a simplified analytical model, where revised Parker-Murphy model is employed to evaluate electric current generation at plasma contactors together with libration dynamics of tether. The 13th-order Earth's magnetic field model is used to account influence of inhomogeneity of Earth's magnetic field on orbital parameters of electrodynamic tether system, especially in inclined orbits. Parametric analysis has been conducted for orbital boost maneuver from 400 km to 1,200 km at four different orbital inclinations. The results show that (i) the orbit of electrodynamic tether system will change from circular to elliptical orbits, especially in inclined orbits, (ii) the voltage of onboard power supply at the anode affect electric current generation, (iii) the coupled multiphysics model is necessary to characterize the interaction of electrodynamic tether with the surrounding space environment and the controllability of electric current in electrodynamic tether, (iv) the motion of orbital boost maneuver by electrodynamic tether is stable, which is different from the deorbit by electrodynamic tether.

ACS Style

Jinyu Liu; Gangqiang Li; Zheng H. Zhu; Xingqun Zhan. Orbital boost characteristics of spacecraft by electrodynamic tethers with consideration of electric-magnetic-dynamic energy coupling. Acta Astronautica 2020, 171, 196 -207.

AMA Style

Jinyu Liu, Gangqiang Li, Zheng H. Zhu, Xingqun Zhan. Orbital boost characteristics of spacecraft by electrodynamic tethers with consideration of electric-magnetic-dynamic energy coupling. Acta Astronautica. 2020; 171 ():196-207.

Chicago/Turabian Style

Jinyu Liu; Gangqiang Li; Zheng H. Zhu; Xingqun Zhan. 2020. "Orbital boost characteristics of spacecraft by electrodynamic tethers with consideration of electric-magnetic-dynamic energy coupling." Acta Astronautica 171, no. : 196-207.

Conference paper
Published: 01 March 2020 in Lecture Notes in Electrical Engineering
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This paper proposes a novel concept of partial space elevator with parallel tethers and multiple climbers. The parallel tethers impacting on the dynamic response of partial space elevator is investigated based on a high-fidelity and accurate model of PSE. The model is developed based on the nodal position finite element method in the arbitrary Lagrangian–Eulerian description. The results show that the tethers collide when the transient motion of climbers is not the same, such as the movement direction of climbers is opposite and the time delay between climbers. It also found that the multiple climbers of each other may aggravate the libration motion of PSE without predesigned time shift. The results show the trajectories of climber are very important and should be well designed to avoid the collision of tethers and assure the safety operation of load transfer.

ACS Style

Gangqiang Li; Zheng H. Zhu. Dynamics of Partial Space Elevator with Parallel Tethers and Multiple Climbers. Lecture Notes in Electrical Engineering 2020, 231 -252.

AMA Style

Gangqiang Li, Zheng H. Zhu. Dynamics of Partial Space Elevator with Parallel Tethers and Multiple Climbers. Lecture Notes in Electrical Engineering. 2020; ():231-252.

Chicago/Turabian Style

Gangqiang Li; Zheng H. Zhu. 2020. "Dynamics of Partial Space Elevator with Parallel Tethers and Multiple Climbers." Lecture Notes in Electrical Engineering , no. : 231-252.