Coilable masts are extensively utilized in aerospace systems owing to their structural simplicity, reliability, and high deployment ratios. However, their application is constrained by compression-twist coupling motion during deployment, which induces large structure deformations and displacements. To address this limitation, this study proposes a parallel chiral coilable mast with synergistic control strategies. This design transforms the conventional unidirectional compression-twist motion into a bidirectional synchronous pure sliding deployment. Three pretensioned modes were developed for a single-bay unit based on diagonal constraints, leveraging the critical role of diagonals in achieving structural bistability. A topology-optimized multi-bay configuration enables directional rotation while maintaining structural stability via pretension modes. By redesigning structural constraints on the top and bottom disks, a decoupling strategy achieves pure linear motion at the top batten frame, significantly expanding the operational envelope. The parallel-designed chiral configuration is developed based on the synergistic control strategies of these two structural constraints. Numerical simulations and experimental validation confirm the effectiveness and feasibility of the synergistic control strategies. The chiral configuration facilitates multifunctional deployment capabilities in geometrically unconstrained environments, demonstrating substantial improvements over conventional designs.

To address the challenges of imprecise control of shape memory alloy (SMA) material control processes due to nonlinearities, hysteresis, and time-varying parameters, a prescribed performance control method using integrated sliding mode backstepping control was proposed. First, a mechanism model was formulated on the basis of the architecture of the SMA actuator. To improve the system's dynamic tracking error performance, a novel performance function based on the prescribed performance control method was introduced. Concurrently, the convergence of the transformed error function is ensured by combining the integral sliding mode backstepping controller, guaranteeing that the tracking error converges to the predefined envelope range of the performance function. Moreover, an extended state observer (ESO) is utilized to observe and compensate for uncertainties and disturbances arising from system parameter fluctuations or modeling inaccuracies. For SMA material parameters that cannot be measured directly, an experimental setup was constructed to identify and validate these parameters. In conclusion, numerical simulations are conducted to compare the proposed control method with sliding mode controllers (SMCs) and proportional-integral (PI) controllers, assessing the dynamic behavior and response speed of the SMA actuator under various target angle inputs. The findings revealed that the proposed control strategy achieves the fastest convergence times and the lowest root mean square errors (RMSEs) across three different target angle tracking scenarios, with values of 1.003e-3 degrees, 5.244e-4 degrees, and 3.367e-5 degrees, respectively. These results represent improvements of 54.11% and 55.84% over those of the SMC and PI controllers, respectively. Consequently, the proposed control methodology demonstrates rapid responsiveness, high control precision, and robust performance.

This paper proposes a novel finite-time integrated guidance and control (IGC) design for skid-to-turn (STT) missiles, taking full state constraints into account. Firstly, the actuator saturation is converted into a state constraint. Secondly, to handle full state constraints effectively, the "non-constrained" IGC (NCIGC) model is constructed by combining the IGC model with a permissible set of states and applying a nonlinear transformed function. Thirdly, a finite-time full state constraints IGC scheme based on the NCIGC model is presented. According to Lyapunov stability theory, the proposed IGC method is verified to ensure that all states of the IGC model converge to a small neighborhood near zero within a finite time while satisfying the predefined state constraints. Finally, numerical simulations are performed to demonstrate the effectiveness and robustness of the proposed IGC scheme. © 2023 Elsevier Masson SAS

Coilable masts, as the appendages of large spacecraft, are widely used in complex space missions because of their remarkable folding performance and large folding ratio. However, the motion instabilities from compression-twist coupled deformations limit their application. A six-parameter bar-hinge theoretical modeling inspired by Kresling origami is established to analyze energy landscapes and mechanical behavior during complete folding. The analytical solution of the theoretical model determined the precise positions of the stable states. Numerical simulation based on the equilibrium and stability conditions derive various deformation mechanisms and motion behavior, verifying the correctness of the analytical solution, and demonstrating tunable bistability governed by initial height. On this basis, the influencing mechanism of parameter programming is explored to develop reverse design frameworks. Folding resistance modulated by material intrinsic and extrinsic properties. Varying longeron counts affect the position of the second stable state. Furthermore, three experiments confirm the correctness of tunable property and the effectiveness of parameter programming. Standardized design procedures accommodate diverse mission requirements, enhancing application prospects through precise mechanical performance control. © 2025 Elsevier Ltd

Strap-down seeker is rigidly fixed onto the missile body, which results in detection information being coupled to the missile's attitude and having a narrow field-of-view (FOV). During the terminal guidance flight, attitude adjustment of the missile may lose the target's lock and reduce interception accuracy. Therefore, this paper investigates three-dimensional integrated guidance and control (IGC) under the constraints of the FOV and roll angle for skid-to-turn (STT) missile with strap-down seeker. A new low-order IGC model is constructed by establishing a second-order model of body line-of-sight (BLOS) angle based on strap-down decoupling theory and combining it with the second-order roll angle equation. Furthermore, a low-order fixed-time IGC scheme is developed using the integral barrier Lyapunov function (iBLF) to limit BLOS and roll angles. Fixed-time filter, which avoids the "complexity explosion" caused by conventional back-stepping technique, is utilized for obtaining virtual control command and its derivative. A fixed-time disturbance observer is introduced to compensate for the lumped disturbance. According to Lyapunov stability theory, it is proven that the proposed IGC scheme can make the closed-loop system converge within a fixed time. Finally, the effectiveness and robustness of the IGC scheme are verified by various numerical simulations. © 2023 The Franklin Institute

Spacecraft control problems frequently require the latest model parameters to provide timely updates to the controller parameters. This study investigates the recursive identification problem in a the time-varying state-space model of an on-orbit rigid-flexible coupling spacecraft. An improved recursive predictor-based subspace identification (RPBSID) method is presented to increase on-orbit identification efficiency. Compared with the classical RPBSID and other subspace methods, the improved RPBSID applies the affine projection sign algorithm. Accordingly, the system state variables can be determined directly via recursive computation. Thus, the proposed algorithm does not require constructing the corresponding Hankel matrix or implementing singular value decomposition (SVD) at each time instant. Consequently, the amount of data used in the identification process is reduced, and the computational complexity of the original method is decreased. The time-varying state-space model of the spacecraft is estimated through numerical simulations using the classical RPBSID, improved RPBSID, and SVD-based approaches. The computational efficiency and accuracy of the three methods are compared for different system orders. Computed results of the test response demonstrate that the improved RPBSID algorithm not only achieves sufficient identification accuracy but also exhibits better computational efficiency than the classical methods in identifying the parameters of the spacecraft time-varying state-space model.
© 2018 IAA

The dual-arm space robot usually forms a closed-chain constraint system with a target through collaborative operations when performing tasks. Most previous related research has focused on the performance of open-chain robots themselves. Studying the manipulation performance of a closed-chain robot system is of great significance. This article proposes a reconfigurable space robot (RSR) system for on-orbit servicing. A graph theory based framework for the automatic generation of reconfigurable robot models is proposed to address the characteristics of variable topology structures. Meanwhile, a new index - the closed-chain inertia matching index is proposed to evaluate its configuration effectively. Compared with traditional dynamic manipulability ellipsoid (DME) and manipulating force ellipsoid (MFE), the effectiveness of the proposed closed-chain inertia matching ellipsoid (IME) is verified. Compared with the DME and MFE, the IME effectively considers the influence of load and can effectively express the dynamic torque force/torque transmission efficiency from the joint actuator to the load in a closed-chain system. The IME can not only be used to determine the optimal joint configuration under a specific closed-chain configuration, but also to determine the optimal nonisomorphic configuration of a reconfigurable robot. Finally, the results of configuration optimization of the closed-chain dual-arm reconfigurable space robot are given. Note to Practitioners-This paper aims to study the determination of the optimal configuration for the RSR during task execution. Due to its various configurations, the RSR has a complex modeling process. This article proposes a modeling framework for automatically generating RSR models that can effectively achieve automatic modeling of various configurations. In addition, most of the previous related research focused on the performance of open-chain robots themselves, ignoring the impact of load. This article proposes a new closed-chain system performance indicator to evaluate the robot configuration. The proposed evaluation indicator effectively considers the influence of load, which is of practical significance to improve the efficiency of task execution. The effectiveness of the proposed index in determining the optimal configuration is demonstrated by simulation verification. In the future, we will focus on multi-arm collaborative operations under a specific configuration.

In order to improve the performance of the pressure control system in the combustion chamber of the pintle adjustment engine and realize accurate closed-loop control， the mathematical model of the system was established， and a Fuzzy-PID compound controller based on the Particle Swarm Optimization（PSO） algorithm was proposed. The traditional PID controller could not be accurately controlled because the model has substantial time variability， perturbation and is nonlinear. Therefore， PSO-Fuzzy-PID composite controller was designed and used. The fuzzy controller and PID controller worked at the same time. PSO algorithm was used to optimize and update the output scale factor of the two controllers in real-time. The PSO-Fuzzy-PID composite controller， Fuzzy-PID dual-mode controller and traditional PID controller were compared by simulation in the step tracking and the time variability test near the operating point of the system（6 MPa），and the anti-interference test and the long time full pressure range adjustment test in the nonlinear model to verify the dynamic performance of the controller. The results indicate that the PSO-Fuzzy-PID composite controller exhibits significant advantages in different experiments. The overshoot can be controlled within 10%. The adjustment time can be controlled within 1.5 s， and the pressure adjustment speed can be increased to 3.45~6.73 times that of the Fuzzy-PID dual-mode controller and 4.51~7.1 times that of the traditional PID controller. Therefore， the PSO-Fuzzy-PID composite controller has more advantages in response speed， overshoot， and strong robustness and significantly improves the dynamic performance of the pressure control system in the combustion chamber of the pintle adjustment engine. © 2024 China Aerospace Science and Industry Corp. All rights reserved.

Aromatic hydrocarbons generally refer to compounds containing benzene rings. Many types of isomers can be formed by replacing hydrogen atoms on the benzene ring. In this paper, an aromatic-hydrocarbon-inspired modular robot (AHIMR) is proposed. The robot can be reassembled into different configurations suitable for various task requirements. A vision-based docking system is designed for the AHIMR. The system primarily consists of two stages: a remote guidance stage and a precise docking stage. During the remote guidance stage, an object module is identified using an illumination adaptive target recognition algorithm, and then the active module moves to the docking area through communication with ZigBee. In the precise docking stage, the active module calculates the relative pose with the object module using a perspective-n-point method and dynamically adjusts its posture to dock. In this process, a Kalman filter is used to reduce target occlusion and jitter interference. In addition, the docking system feasibility is verified via several simulation experiments. The module docking accuracy is controlled within 0.01 m, which meets the reconfiguration task requirements of the AHIMR. In the AHIMR submodule docking experiment, the active module accurately moves to the expected position with a docking success rate of 95%.

The low-velocity penetrator (LVP) is a planetary penetration device that can drive itself to a target depth through its internal periodic impacts. When LVP generates impact energy, it inevitably produces a recoil that can only be counteracted by friction with the soil, if there is no other auxiliary device. Unfortunately, LVP is extraordinarily sensitive to the recoil during the initial stage since the small contact area with the soil results in minor friction between them. Significantly, once the recoil exceeds the friction, LVP cannot work properly and may even retreat, inducing mission failure. In this paper, we develop an optimized LVP with an auxiliary device for lower recoil and higher performance. Specifically, we establish a dynamic model to analyze the single-cycle motion of LVP and provide essential support for its optimization and design. Meanwhile, an integration method is proposed to calculate the friction between LVP and the soil reasonably and accurately. On the basis of these, we obtain the optimal mass and stiffness parameters of LVP that meet both high penetration efficiency and low recoil. Furthermore, only relying on the parameter optimization is insufficient to eliminate the recoil, and an auxiliary penetration scheme is proposed to provide an external force counteracting the recoil until LVP arrives at a certain depth. Through multiple comparative penetration experiments, we validate the effectiveness of our approaches in promoting penetration ability, stability, and restraining the recoil of LVP. This work provides two novel approaches for solving the contradiction of efficient penetration while reducing the recoil for LVP.