Rigid-flexible Hybrid Research Articles

A Bionic Flapping Magnetic-Dipole Resonator for ELF Cross-Medium Communication.

Extremely low-frequency (ELF) electromagnetic (EM) waves adeptly propagate in harsh cross-medium environments, overcoming rapid decay that hinders high-frequency counterparts. Traditional antennas, however, encounter challenges concerning size, efficiency, and power. Here, drawing inspiration from nature, we present a groundbreaking piezo-actuated, bionic flapping-wing magnetic-dipole resonator (BFW-MDR), operating in the electro-mechano-magnetic coupling mechanism, designed for efficient ELF EM wave transmission. The unique rigid-flexible hybrid flapping-wing structure magnifies rotation angles of anti-phase magnetic dipoles by tenfold, leading to constructive superposition of emitted magnetic fields. Consequently, the BFW-MDR exhibits a remarkable quality factor of 288 and an enhanced magnetic field emission of 514 fT at 100 meters with only 6.9 mW power consumption, surpassing traditional coil antennas by three orders of magnitude. The communication rate is doubled by the ASK+PSK modulation method. Its robust performance in cross-medium communication, even amidst various interferences, underscores its potential as a highly efficient antenna for underwater and underground applications.

Reversibly stable and highly stretchable transparent polymer nanocomposite adhesives using hierarchical spring-like molecular nanobridges

For the development of stretchable optoelectronic devices, optically transparent composite adhesives should afford reversible stretchability and high optical transmittance as well as strong interfacial adhesion. However, simultaneous achievement of these essential prerequisites for advanced stretchable optical composite adhesives remains challenging. Herein, we offer an unprecedented approach for the fabrication of reversibly stretchable and optically transparent polymer nanocomposite adhesives based on the construction of hierarchical elastic molecular nanobridges between rigid-flexible hybrid nanoparticles and matrix resin. Photoreactive flexible poly(propylene glycol) (meth)acrylate chains were chemically combined with a rigid nano-silica core to form rigid and flexible hybrid nanoparticles. Subsequently, multiple elastic molecular nanobridges between the embedded hybrid nanoparticles and acrylate resin matrix were constructed inside the polymer composite through UV curing, which results in a stretchable interconnection that allows efficient repeated stretching and recovery of stretchable polymer nanocomposite adhesives. The newly fabricated nanocomposite adhesive film with a low content of rigid-flexible hybrid nanoparticles afforded an excellent reversible stretchability and outstanding cyclic elastic durability, and simultaneously maintained high optical transparency (95.1%) and interfacial adhesion strength (21.5 N/25 mm) of the film compared to those of conventional optical adhesive film.

Cerebellum-Inspired Model-Free Tracking Control and Visual Servoing of a Rigid-Flexible Hybrid Robotic Endoscope With RCM Constraints

This article designs a model-free control scheme based on a cerebellum-inspired network model for tracking control and visual servoing of a surgical rigid-flexible hybrid robotic endoscope. The hybrid robot is composed of a rigid robot manipulator and a flexible endoscope as the end-effector. Inspired by the cerebellum associated with human motion control, we proposed a cerebellum-inspired model-free control scheme for the visual servoing and tracking control of the robotic endoscope with RCM (remote center of motion) constraints, which does not need to know the kinematic model of the robot. This scheme combines liquid state machines (LSM) and zeroing neural network (ZNN), where the LSM is able to generate control signals and the ZNN is used as the training signal for the LSM. Simulations and physical experiments demonstrate that the proposed cerebellum-inspired control scheme is effective to handle the tracking task under RCM constraints as well as the visual servoing task.

An advanced rigid-flexible hybrid assembly deviation analysis method for aerostructures

Aerostructures are important components of an aircraft's aerodynamic shape, and their assembly requires high precision. To ensure optimal external shape performance, a significant number of assembly deviation calculations must be performed during the design process of an aerostructure. However, accurately describing shape deviation necessitates high-fidelity surface deformation data. Therefore, an assembly deviation analysis method that balances rapid response and accurate calculation under conditions of large data volume and high cost plays a vital role in promoting the external performance of aerostructures. While some progress has been made in this field, the existing methods are still unable to fill this research gap completely. This paper proposes an advanced rigid-flexible hybrid assembly deviation analysis (RFHA) method for aerostructural shape deviation. It decomposes assembly deviation into rigid deviation transmission and flexible deformation, unifying them in one framework. This method predicts the flexible deformation of aerostructures using discrete cosine transform (DCT) and surrogate model (SM). It also develops a rigid-flexible hybrid assembly deviation analysis method in combination with the Jacobian-Torsor model (J-T). To further reduce computational resources and improve the performance of the surrogate model, the mega-trend diffusion (MTD) is utilized to generate virtual samples to expand the sample set. Relevant parameters of the proposed method are determined using experimental methods. The proposed method is validated and compared with an existing RFHA and a commercial software package. The results show that the proposed method can guarantee prediction performance under small sample conditions and reduce computational burden, while maintaining a certain advantage in rapid response and accurate calculation.

Cellulose-Br-initiated imidazolium cation and ether linkage regulation of all-solid-state polymer electrolyte for advanced lithium transfer and battery performance

The all-solid-state polymer electrolyte (SPE) with superior electrochemical performance and stability is the most significant part for the development of high safety and reliable batteries. In this work, the ether linkage and imidazolium ionic liquid are incorporated into the modified macromolecular cellulose network via atom transfer radical polymerization for the construction of brush-like cellulose bromide-poly(ethylene glycol) methyl ether methacrylate@1-vinylimidazole ionic liquid (CB-PEGMA@IL) and cellulose bromide-1-vinylimidazole ionic liquid@poly(ethylene glycol) methyl ether methacrylate (CB-IL@PEGMA) composite polymers. The crystallinity of pristine CB is largely decreased on account of the synergistic effect of ionic liquids and ether linkage. In particular, CB-PEGMA@IL presents a lower crystallinity and superior electrochemical performances than that of the CB-IL@PEGMA. With a wide electrochemical stability window (5.3 V vs Li/Li+), the CB-PEGMA@IL based SPE presents a high ionic conductivity (1.2 × 10−4 S cm−1) and record Li+ transference number (0.32). LiFePO4/Li battery assembled with CB-PEGMA@IL-SPE shows excellent cycling performance (beyond 150 cycles at 0.2 C) and good rate capacity. Moreover, the overpotential of CB-PEGMA@IL-SPE based symmetric battery can keep ∼0.03 V even after 200 h cycling (100 μA cm−2). The soft-packed battery based on CB-PEGMA@IL-SPE can withstand bending and present stable voltage output upon folding at various angles. This rigid-flexible hybrid SPE provides a unique candidate for the fabrication of wearable high-tech electronic devices.

Inside Back Cover: Rigid‐Flexible Hybrid Porous Molecular Crystals with Guest‐Induced Reversible Crystallinity (Angew. Chem. Int. Ed. 13/2023)

A rigid-flexible hybrid hydrogen-bonded organic framework (HOF) with guest-induced reversible crystallinity was designed by Yingjie Zhao and Danbo Wang in their Research Article (e202217903). A specific compound, such as hexane, acts as a “key” to control the crystallinity, while the triangle macrocycle as the building module is the “lock”. The introduction and removal of the “key” molecule affects the local flexibility of the whole framework and leads to switchable crystallinity.

Innenrücktitelbild: Rigid‐Flexible Hybrid Porous Molecular Crystals with Guest‐Induced Reversible Crystallinity (Angew. Chem. 13/2023)

A rigid-flexible hybrid hydrogen-bonded organic framework (HOF) with guest-induced reversible crystallinity was designed by Yingjie Zhao and Danbo Wang in their Research Article (e202217903). A specific compound, such as hexane, acts as a “key” to control the crystallinity, while the triangle macrocycle as the building module is the “lock”. The introduction and removal of the “key” molecule affects the local flexibility of the whole framework and leads to switchable crystallinity.

Dynamic Simulation Analysis of the Antiswing Device for Ship-Mounted Batch Transfer Hanging Basket

When the rescue vessels use the hanging basket to transfer the wounded at sea, under the action of waves, the ship causes the hanging basket to swing significantly. To prevent the second injury to the wounded caused by the large swing of hanging basket, a rope-driven rigid-flexible hybrid hanging basket antiswing control system is designed, the control principle of the system is introduced, and an accurate dynamics model of the system is established based on the D’Alembert principle, the rigid-flexible hybrid model is used to the antiswing control and simulation of the ship-mounted batch transfer hanging basket for the first time. Analyzed its control principle and simulate the variations in length, velocity, acceleration, and force changes of the control ropes. By installing rigid bal-hinge telescopic sleeve, the simulation results indicate that the indicators of the driving ropes are smooth and continuous and the value changes are also within a suitable range. The force on the four control ropes has been reduced by ∼24.1%, 23%, 26.4%, and 25.1%, resulting in the force that is more reasonable and enhancing the safety of hanging basket system. The hanging basket antiswing device is capable of compensating for rolling and pitching motions at sea and has a strong impact on swinging.

Mechanical Design and Workspace Analysis of a Rigid-flexible Hybrid Driven Parallel Spray-painting Robot

Mechanical Design and Workspace Analysis of a Rigid-flexible Hybrid Driven Parallel Spray-painting Robot

Kinematic, Workspace and Force Analysis of A Five-DOF Hybrid Manipulator R(2RPR)R/SP+RR

In the present study, the over-constrained hybrid manipulator R(2RPR)R/SP+RR is considered as the research objective. In this paper, kinematics of the hybrid manipulator, including the forward and inverse position, are analyzed. Then, the workspace is checked based on the inverse position solution to evaluate whether the workspace of the hybrid manipulator meets the requirements, and the actual workspace of the hybrid robot is analyzed. After that, the force analysis of the over-constrained parallel mechanism is carried out, and an ADAMS-ANSYS rigid-flexible hybrid body model is established to verify the simulation. Based on the obtained results from the force analysis, the manipulator structure is designed. Then, the structure optimization is carried out to improve the robot stiffness. Finally, calibration and workspace verification experiments are performed on the prototype, cutting experiment of an S-shaped aluminum alloy workpiece is completed, and the experiment verifies the machining ability of the prototype. This work conducts kinematics, workspace, force analyses, structural optimization design and experiments on the over-constrained hybrid manipulator R(2RPR)R/SP+RR, providing design basis and technical support for the development of the novel hybrid manipulator in practical engineering.

Miniature Amphibious Robot Actuated by Rigid-Flexible Hybrid Vibration Modules.

Amphibious robots can undertake various tasks in terrestrial and aquatic environments for their superior environmental compatibility. However, the existing amphibious robots usually utilize multi‐locomotion systems with transmission mechanisms, leading to complex and bulky structures. Here, a miniature amphibious robot based on vibration‐driven locomotion mechanism is developed. The robot has two unique rigid‐flexible hybrid modules (RFH‐modules), in which a soft foot and a flexible fin are arranged on a rigid leg to conduct vibrations from an eccentric motor to the environment. Then, it can run on ground with the soft foot adopting the friction locomotion mechanism and swim on water with the flexible fin utilizing the vibration‐induced flow mechanism. The robot is untethered with a compact size of 75 × 95 × 21 mm3 and a small weight of 35 g owing to no transmission mechanism or joints. It realizes the maximum speed of 815 mm s–1 on ground and 171 mm s–1 on water. The robot, actuated by the RFH‐modules based on vibration‐driven locomotion mechanism, exhibits the merits of miniature structure and fast movements, indicating its great potential for applications in narrow amphibious environments.

Rigid—flexible hybrid surfaces for water-repelling and abrasion-resisting

Droplets impacting solid superhydrophobic surfaces is appealing not only because of scientific interests but also for technological applications such as water-repelling. Recent studies have designed artificial surfaces in a rigid—flexible hybrid mode to combine asymmetric redistribution and structural oscillation water-repelling principles, resolving strict impacting positioning; however, this is limited by weak mechanical durability. Here we propose a rigid—flexible hybrid surface (RFS) design as a matrix of concave flexible trampolines barred by convex rigid stripes. Such a surface exhibits a 20.1% contact time reduction via the structural oscillation of flexible trampolines, and even to break through the theoretical inertial-capillary limit via the asymmetric redistribution induced by rigid stripes. Moreover, the surface is shown to retain the above water-repelling after 1,000 abrasion cycles against oilstones under a normal load as high as 0.2 N·mm−1. This is the first demonstration of RFSs for synchronous waterproof and wearproof, approaching real-world applications of liquid-repelling.

Research on Dynamics of Flexible Multibody System with Deployable Antenna Based on Static Lagrangian Function

Abstract Deployable antennas, as the core content of national defense technology research at this stage, have the advantages of large flexibility and light weight in practical applications, so this type of antenna can also be called a rigid-flexible hybrid structure. According to the theoretical analysis of the dynamics of flexible multi-body systems, it can be seen that effective control of unfolding antennas is a basic requirement for practical applications. Due to the instability of the specific numerical solution of the static Lagrangian function, it is difficult to completely meet the constraint equation, which is also the main factor affecting the steady development of flexible multibody dynamics. Therefore, in-depth discussion of the numerical calculation method of the static Lagrangian function, obtaining efficient and stable numerical methods from it, and providing effective information for the process control of the deployment of the antenna, is the focus of scientific research scholars at this stage. Based on the understanding of the flexible multi-body dynamics modeling method, this paper systematically analyzes the calculation method of the differential equations, and combines the direct modification method of the constraint violation of the augmentation method to propose the simulation calculation of the model. The final results prove that the dynamics of flexible multi-body systems have a positive effect on the application analysis of deployable antennas.

Rigid-flexible hybrid modeling and dynamic simulation of three-coordinate heavy-load transfer vehicle

Rigid-flexible hybrid modeling and dynamic simulation of three-coordinate heavy-load transfer vehicle

Theoretical Studies on the Longitudinal Inhomogeneity of Track Stiffness and a Track Status Estimation Method

Due to material multiplicity, rigid‐flexible hybrid and environmental variations, and so forth, the properties of the tracks will be inevitably changed due to the cyclic loads temporally and spatially. In this paper, a theoretical study is conducted to clarify the influence of the longitudinal inhomogeneity of track stiffness on system responses and then a general state estimation method is proposed to inversely predict the parametric distribution of the tracks. To achieve these purposes, a 3D nonlinear vehicle‐track coupled model is firstly constructed, where track systems are established by the finite element method with random parameters. Based on this dynamic model, the distribution characteristics of system responses due to random parametric excitations are properly revealed. The numerical studies show that the longitudinal inhomogeneity of track supporting stiffness has significant effects on system responses; besides, the response distributions are varied against different parametric distributions. Finally, a representative example is demonstrated to show the effectiveness of the proposed track state estimation method.

Dynamic model of four degree of freedom rope-driven rigid-flexible hybrid wave compensation device

In the process of replenishment at sea, in order to ensure the safety of workers and cargo on the deck, collisions between the cargo and the deck or cargo should be at least reduced if not avoided. Considering the actual situation of the marine environment, a fourdegree- of-freedom rope-driven rigid-flexible hybrid wave compensation mechanism for offshore hoisting equipment is proposed. First, based on the screw theory, the feasibility of a wave compensation mechanism was verified, and the experimental device of the wave compensation mechanism was designed. Then, a positional forward/reverse solution model of the wave compensation mechanism was established based on the algebraic method. Then, the kinematics model of the wave compensation mechanism was derived and the system dynamics model of the wave compensation mechanism was established based on Newton-Eulerian method. The simulation software was used to verify the derived mathematical model. It was found that the positional positive/negative solution error of the wave compensation mechanism was of the order of 10-5 mm; the MATLAB numerical simulation results and the Adams virtual prototype results of the kinematics and dynamics models were basically consistent. The maximum error was 2.4 % of the theoretical value, which is an acceptable range. The correctness of the derived kinematics and dynamics model was verified. The research results provide a theoretical basis for further performance analysis and motion control of the wave compensation mechanism.

Research on an Ankle Joint Auxiliary Rehabilitation Robot with a Rigid-Flexible Hybrid Drive Based on a 2-S'PS' Mechanism.

An ankle joint auxiliary rehabilitation robot has been developed, which consists of an upper platform, a lower platform, a dorsiflexion/plantar flexion drive system, a varus/valgus drive system, and some connecting parts. The upper platform connects to the lower platform through a ball pin pair and two driving branch chains based on the S′PS′ mechanism. Although the robot has two degrees of freedom (DOF), the upper platform can realize three kinds of motion. To achieve ankle joint auxiliary rehabilitation, the ankle joint of patients on the upper platform makes a bionic motion. The robot uses a centre ball pin pair as the main support to simulate the motion of the ankle joint; the upper platform and the centre ball pin pair construct a mirror image of a patient's foot and ankle joint, which satisfies the human body physiological characteristics; the driving systems adopt a rigid-flexible hybrid structure; and the dorsiflexion/plantar flexion motion and the varus/valgus motion are decoupled. These structural features can avoid secondary damage to the patient. The rehabilitation process is considered, and energy consumption of the robot is studied. An experimental prototype demonstrates that the robot can simulate the motion of the human foot.

Simulation Research of Rotor Misalignment Fault Based on Adams

Misalignment is a common failure of rotating machinery, it can cause many problems such as vibration and bearing loss. The research on misalignment usually uses rotor failure test platform, it is a common equipment in various mechanics laboratories that has a mature development. But it still has some defects such as cumbersome operation and high cost. This paper had analyzed the existing rotor failure test platform in the laboratory, according to its actual size and materials, a rigid-flexible hybrid model was established. Based on the method of Adams vibration analysis, the model is simulated and analyzed in parallel misalignment and angle misalignment. According to the results, it was proved that simulation and study of rotor faults based on ADAMS simulation method had a certain feasibility and extensive applicability, and the theoretical basis for virtual prototype was provided.

Misfire Fault Diagnosis of Range Extender Based on Harmonic Analysis

For an Extended-Range Electric Vehicle (E-REV), the misfire failure of the range extender can result in working condition deterioration, mileage decrease, vibration and noise increase, and other adverse consequences. The relationship of the shaft instantaneous angular speed (IAS) signal and the misfire fault of the range extender was studied by harmonic analysis. Based on the theory of shafting torsional vibration, the range extender dynamics model was developed to analyze the changing trend of the shaft IAS theoretically. Then, the shaft IAS signal under different working conditions was simulated using a developed range extender rigid-flexible hybrid multi-body dynamics model. It is found that the 0.5-order harmonic phase and the amplitude of range extender IAS can be used as the characteristic parameters in misfire fault diagnosis, which has been verified by experiments on an engine bench.

Assembly variation analysis of complicated products based on rigid–flexible hybrid vector loop

The performance of mechanical products is closely related to their key feature errors. It is essential to predict the final assembly variation by assembly variation analysis to ensure product performance. Rigid–flexible hybrid construction is a common type of mechanical product. Existing methods of variation analysis in which rigid and flexible parts are calculated separately are difficult to meet the requirements of these complicated mechanical products. Another methodology is a result of linear superposition with rigid and flexible errors, which cannot reveal the quantitative relationship between product assembly variation and part manufacturing error. Therefore, a kind of complicated products’ assembly variation analysis method based on rigid–flexible vector loop is proposed in this article. First, shapes of part surfaces and sidelines are estimated according to different tolerance types. Probability density distributions of discrete feature points on the surface are calculated based on the tolerance field size with statistical methods. Second, flexible parts surface is discretized into a set of multi-segment vectors to build vector-loop model. Each vector can be orthogonally decomposed into the components representing position information and error size. Combining the multi-segment vector set of flexible part with traditional rigid part vector, a uniform vector-loop model is constructed to represent rigid and flexible complicated products. Probability density distributions of discrete feature points on part surface are regarded as inputs to calculate assembly variation values of products’ key features. Compared with the existing methods, this method applies to the assembly variation prediction of complicated products that consist of both rigid and flexible parts. Impact of each rigid and flexible part’s manufacturing error on product assembly variation can be determined, and it provides the foundation of parts tolerance optimization design. Finally, an assembly example of phased array antenna verifies effectiveness of the proposed method in this article.