Jinzhao Yang

Purpose: This study aims to investigate an adaptive notch filtering approach to suppress the effects of elastic vibration on the attitude control of flexible launch vehicles. Design/methodology/approach: First, the dynamics model of the flexible launch vehicle and baseline PID controller are presented. Furthermore, the frequency identification algorithm based on a second-order notch filter is developed to identify the elastic vibration frequency. Finally, a frequency holder is developed to update the notch frequency of the adaptive notch filter. Findings: The proposed adaptive notch filter with a frequency holder can identify the vibration frequency accurately, update the notch frequency appropriately and suppress the effects of the elastic vibration on the attitude control of flexible launch vehicles effectively. Originality/value: A novel adaptive notch filter with a frequency holder is proposed to address the adaptive filtering problem of elastic vibrations under nonelastic interference and elastic frequency uncertainty. Compared with the conventional filter for attitude control of flexible launch vehicles, an adaptive filter with a proposed frequency holder is developed to solve the problem of the frequency real-time update during the vibration suppression and frequency keeping after the vibration suppression.

Rigidity and softness are contradictive but critical to empowering soft robots with the versatility needed to cope with diverse complex scenarios. However, current soft robots consistently encounter a limitation, being confined to either soft or rigid states, thereby lacking the capability to incorporate both properties within a unified paradigm. Herein, we developed a simple yet versatile building block constructed by tensegrity structures, showing anisotropic deformation characteristics analogous to seahorse tails. Due to the disparity in bending stiffness between the ventral and lateral directions, the tensegrity building block presents notable advantages in the creation of robotic paradigms with anisotropic behavior, which enables soft robots created by it to show customizable responses. Then, we implemented the construction of two distinct soft robots based on the building block, i.e., continuum robots and robotic grippers. These typical applications serve to exemplify how the anisotropic properties bestow upon soft robots the capability for programmable mechanical responses and versatile capabilities. This interdisciplinary investigation represents a noteworthy progression in the development of readily adjustable building blocks for soft robots.

Bistable structures, which leverage mechanical instability, have emerged as a promising paradigm in the development of robotic grippers, providing advantages including rapid response and low energy consumption. A critical limitation of existing bistable grippers, however, lies in their invariable energy barriers, which hinder the balance between compliant triggering and powerful grasping. In this study, we propose a bistable robotic gripper capable of in situ energy barrier modulation, inspired by the adaptive seed dispersal behavior of Impatiens pods. This robotic gripper features an elastic curved beam-based architecture integrated with a motor-driven mechanism, enabling dynamic regulation of its energy landscape. This approach allows the energy barrier to be tuned over an order of magnitude during manipulation. In the low-barrier state, the robotic gripper initiates object interaction with a triggering force as low as 0.66 N, allowing for delicate manipulation. Upon state transition, instant energy barrier modulation (~300 ms) enhances grasping stability, achieving failure forces up to 12.08 N. This adaptive modulation strategy enables our robotic gripper to implement rapid, compliant, and powerful interaction. When incorporated into an unmanned aerial vehicle, the robotic gripper showcases reliable perching across diverse scenarios, highlighting the potential of energy barrier modulation to advance the adaptability and functionality of robotic systems.

Grasping and manipulating objects represents crucial functionalities for modern robotic grippers. Nonetheless, an enduring challenge persists in engineering a gripper capable of achieving adaptive, rapid, and stable grasping behavior simultaneously. Here, we proposed a bistable mechanism derived from compliant tensegrity structures that performs a rapid shape change within 200 ms, based on which a Trident robotic gripper is developed without the need for additional actuation sources. This universal and unactuated paradigm showcases robust grasping abilities with adaptability and rapidity analogous to natural flytrap leaves. The tunable bistable properties, achieved by varying geometrical parameters, endow the gripper with extensive design flexibility. The morphing configuration of the gripper retains residual energy after transitioning between stable states, ensuring stable grasping without requiring a continuous energy supply. The benefits of the gripper empower the creation of a robotic system capable of handling objects with diverse profiles across various fields and an unactuated mechanism proficient in gently grasping and swiftly moving insects.

The large-scale space structure during on-orbit assembly is a time-varying system. The dynamic modeling problem of such incrementally increasing space structure is investigated, and a modular dynamic modeling approach is proposed in this paper. The dynamic model of each substructure is first established, and then, a database is designed to store substructure models, which is used for subsequent dynamic modeling in the assembly process. The fixed connection relationship between adjacent substructures is described by constraint conditions, which lead to the coefficient matrices of adjacent substructures being decoupled. The substructures are assembled in a given sequence, and then, the dynamic modeling, to describe the large-scale space structure on-orbit assembly, is gradually completed via using the proposed modeling approach. The numerical simulation is finally presented. The results demonstrate that the extra calculation resulting from the coefficient matrices coupling of adjacent substructures is avoided. Moreover, the proposed dynamic model can accurately describe the dynamic characteristics of the large-scale space structure during on-orbit assembly.