In diverse engineering disciplines, vibration isolation technology is indispensable for ensuring stability, accuracy, and safety. Traditional vibration isolation methods often compromise structural rigidity, particularly at ultra-low frequencies, presenting a significant challenge. To solve this issue, this study introduces cuttlebone-inspired lattice structures (CILS), which are fabricated using selective laser sintering (SLS) 3D printing and have an excellent energy absorption capacity as well as enhanced vibration isolation. This innovation enables effective low-frequency, full-band vibration isolation while preserving structural stiffness. CILS have an excellent energy absorption capacity of 1.411 J/mm3, which is due to the maintenance of a zero Poisson's ratio even under significant deformation (a strain of 0.5). Vibration isolation tests revealed that CILS provide comprehensive isolation across the frequency spectrum of 5-36.77 Hz. Furthermore, CILS effectively extends full-band vibration isolation to medium and high-frequency bands encompassing 56.01 Hz to 2000 Hz. The proposed design strategy offers a novel approach by integrating high energy absorption with extensive isolation capabilities, effectively overcoming traditional limitations to enhance engineering stability and safety.

Perching allows small Unmanned Aerial Vehicles (UAVs) to maintain their altitude while significantly extending their flight duration and reducing noise. However, current research on flying habitats is poorly adapted to unstructured environments, and lacks autonomous capabilities, requiring ideal experimental environments and remote control by personnel. To solve these problems, in this paper, we propose a bat-like UAV perching mechanism by investigating the bat upside-down perching method, which realizes double self-locking in the perching state using the ratchet and four-link dead point mechanisms. Based on this perching mechanism, this study proposes a control strategy for UAVs to track targets and accomplish flight perching autonomously by combining a binocular camera, single-point LiDAR, and pressure sensors. Autonomous perching experiments were conducted for crossbar-type objects outdoors. The experimental results show that a multirotor UAV equipped with the perching mechanism and sensors can reliably achieve autonomous flight perching and re-flying off the target outdoors. The power consumption is reduced to 2.9% of the hovering state when perched on the target object.

X-ray/CT image registration plays a pivotal role in enhancing surgical navigation success rates. However, challenges stemming from sparse and noisy X-ray image features, coupled with the complexities of multiparameter optimization, impose limitations on existing methods in terms of registration accuracy and efficiency. In response, this paper presents an innovative approach-a fast X-ray/CT image registration method based on perspective projection triangular features(F-PPTF). By leveraging the conformal nature of perspective projection, the proposed method constructs perspective projection triangular features with rotation, translation, and scale invariance using point feature descriptors. Diverging from multi -parameter iterative optimization techniques, this approach achieves the decoupling of the six transformation parameters. This decoupling simplifies computational intricacies, thereby facilitating swift registration. Experimental evaluations conducted on synthetic and real X-ray images reveal an average rotational absolute error of 0.41, an average translational absolute error of 1.16 mm, and an average registration time of 14.89 s. In comparison to conventional registration methodologies, the method presented in this paper demonstrates pronounced superiority in terms of both registration accuracy and efficiency, thereby exhibiting heightened potential for broader applicability.

Lattice structure, especially by integrating gradient design and composite/structural design, have already become functional structures. However, they are still not "smart" enough to interact with the environment. Currently, some studies about smart structures are usually complex and do not have load-bearing capacities. Inspired by the human skeletal-muscle-skin system, we propose to interpenetrate low-stiffness and high-stiffness material structures in a gradient manner and design media transfer channels in a soft-phase material for touch perception. The proposed intelligent structure can achieve accurate and large-coverage collision detection and features excellent load-bearing capacity. The gradient design improves the damage pattern and enhances the mechanical properties, and the compression modulus increased by 59.9%. The soft-and hard-composite design further increases the energy absorption capacity by more than 100% and effectively limits catastrophic damage. It shows great potential in applications such as intelligent interactive robots that require both load-bearing and collision-detection capabilities.

The selective laser melting (SLM) 3D printing method was applied to design and to manufacture tungsten materials with lattice structures. The changes in the mechanical properties of tungsten materials with different lattice structures were investigated through finite element analysis, scanning electron microscopy, and quasi-static uniaxial compression tests. The influence of microstructure on mechanical properties was analyzed. The results indicate that the arc lattice structure can effectively reduce stress concentration at the nodes, while maintaining the lightweight and low porosity characteristics of the lattice structure, as well as the high-strength mechanical properties of tungsten materials. The average compressive strength reaches 535 MPa, while the average mass is only 1.25 g. After laser printing, the arc lattice has an average compressive strength increase of 93% compared to the cubic lattice, and the body-centered arc lattice (BCA) shows superior compressive performance, reaching a maximum compressive strength of 721 MPa, with a theoretical structural density of 12.8%. The mechanical performance of 3D printed W is close to that of plastic processed sample. Compared with the cubic lattice, the arc lattice has good ability absorption characteristics, and the total energy absorption value of the latter is increased by 223% compared with the former, and the average energy absorption of the arc lattice reaches 1664 J/mm(3). In addition, the SEM image shows that the arc lattice reduces the hanging distance of the oblique pillar in the printing due to its arc characteristics, and the forming effect is better than that of the cubic lattice.

The advent of additive manufacturing has facilitated the design and fabrication of hybrid lattice structures with multiple morphologies. These structures combine multiple distinct architectures into a single structure with an exceptional performance that far exceeds that of each constituting architecture. However, combining strut-based lattices poses serious challenges in establishing effective connections, primarily due to complications in formulating mathematical expressions. Here, we introduce a novel approach, inspired by the connections observed in the grain boundaries of polycrystalline materials, to design the interconnections of hybrid structures. This strategy involves shrinking the unit cell linkage, thereby addressing the difficulty of forming efficient connections at arbitrary spatial interfaces within strut-based lattice structures. We then use the relevant design theories to tune the performance of these connections and simplify the design process for hybrid structures – even for inexperienced designers. Our experimental observations confirm the efficacy of the proposed strategy, bridging the knowledge gap in the design of connected strut-based multi-lattice structures. Furthermore, this approach enhances the design of tailored hybrid structures and fosters the development of metamaterials with advanced, unique functionalities. The proposed approach has important implications for the development of designer materials, with applications in medical devices, (soft) robotics, and implants.

Sound-absorbing materials with high load-bearing capacities are particularly important in many engineering applications. However, the low load-bearing capacity of conventional sound-absorbing materials limits their engineering applications. In this study, a multisheet parallel design concept is employed to design multisheet sound-absorbing and load-bearing lattice structures. Results show that the multisheet structure outperform the single-sheet lattice structure. The former exhibits a maximum absorption coefficient of 1, a 1x increase in the maximum average absorption coefficient, and a 127x increase in the maximum frequency compared with the latter. Under compression, the multisheet structure exhibits elastic modulus and yield strength values that are 0.43 and 0.52 times those of the single-sheet structure, respectively. Compared with different sound-absorbing structures, the multisheet structure exhibits remarkably high peak absorption coefficients and significant sound-absorbing performance advantages in specific frequency bands. This study presents a new design approach for creating multifunctional structures with sound-absorbing and load-bearing capabilities.

The dependence of structural performance on relative density limits the compliance of lattice structures with specified quality conditions and increases the time and cost required for selecting their configuration and part design. This work proposes a method for designing triply periodic minimal surface (TPMS) lattice structures that achieves precise and large-scale control of their mechanical properties by varying their frequency, and unifies the design of solid and shell structures based on the double surface creation strategy. To verify the proposed method, a series of lattice structures with different frequencies in the bearing direction (ɷz) and offset values were designed and fabricated, and the effects of ɷz on the failure mode, mechanical properties, and energy absorption capacity of the structures were studied. The results show that, by varying ɷz, the performance and failure mode of the structures can be adjusted, and a rapid design of structures with a wide range of mechanical properties can be realized, reaching elastic moduli of 546.15–4264.56 MPa, and compressive strengths of 42.75–143.23 MPa. As a result, the proposed design method can be considered a reference for designing lattice structures with a wide range of control under various requirements, which provides new ideas in the research on TPMS lattice structures.

A novel involute-arc-leg (IAL) which could be applied to multi-legged robots has been presented in this paper. The IAL is composed of the involute-segment and arc-segment. Compared with the common curved leg, the IAL has two advantages: Firstly, the centroid fluctuation and body capsizing can be reduced to improve motion stability; secondly, the torque can be decreased to reduce the energy consumption. With these characteristics, the robot can achieve more efficient and stable motion. Multi-legged robots which are useful for carrying curved legs have been developed, and the stability and energy consumption of the robot with different curved legs have been compared. As verified by experiments, the centroid fluctuation and attitude angle of Quadruped Robot can be reduced to zero with IAL, comparing to arc-legs, in which the energy consumption in standing and walking phase is decreased by 14.1% and 28.71%, respectively. The results prove that the motion stability and energy efficiency of robot can be improved with the curved leg design method based on splicing involute and arc, which provides a useful reference for the design of other robots.

The advantages of “printing the right material in the right position” and “printing the unique structure for unique function” in additive manufacturing make the design of biomimetic graded scaffold of bone tissue engineering possible. Here, under different porosities, we propose a biomimetic graded TPMS scaffold design with adjustable graded pore size, providing guidance for designing porous bone implants without the characteristics of stress concentration, stress shielding and barrier mass transport. Specifically, the structural characteristics of TPMS can be achieved without stress concentration. By adjusting the porosity, the elastic modulus of Ti6Al4V samples can be adjusted in the range of 1158–4567 MPa, which can match the individual selection of mechanical properties of the biological bone. Since the TPMS scaffold is designed by layer-by-layer splicing, through adjusting the height parameters of the single-layer structure, the selective pore size variation can be realized to further match mass transport of biological bone. Then, the in vitro culture experiments have been conducted and the maximum cell survival rate of the scaffold with an offset constant 0.4 is 85.44%, which can meet the mass transport of bone implants. As such, the proposed graded scaffold design in this paper shows excellent potential for orthopedic implants.

Porosity is considered to be one of the key factors affecting the structural properties of porous lattices, but in fact, pore size also plays an important role, and it has great potential to adjust pore size and porosity independently to improve structural properties. In this work, by adjusting the sheet thickness of the triply periodic minimal surface (TPMS) lattice structures and adjusting the height of the single row structure according to linear and constant laws, the TPMS lattice structures with given porosity and adjustable pore size are designed, and the mechanical response is investigated. Based on preparing samples by Ti6Al4V laser powder bed fusion, the results of the tests show that the elastic modulus ranges of linear change TPMS (LC-TPMS) and constant TPMS (C-TPMS) lattice structures are 3625.6 MPa–4575.1 MPa and 3820.0 MPa–4509.1 MPa, respectively. In the plateau stage, the LC-TPMS lattice structures have a longer and more stable plateau stage, higher yield stress and better energy absorption capacity than the C-TPMS lattice structures. The maximum energy absorption difference is 62.7 MJ/mm3 and the maximum energy absorption efficiency difference is 0.12. The LC-TPMS lattice structures can also obtain a larger damping ratio under larger compressive strain.

As a typical application of the human-computer interaction device, the lower limb exoskeleton has attracted many researchers' attention in recent years in an attempt to improve its functionality in human body assistance, augmentation, treatment, and protection. Essentially, the interaction between the lower limb exoskeleton and the subject is mainly realized through its sensing and control system. The sensing and control of lower limb exoskeletons will significantly affect the subject's actual wearing effect in lower extremity assistance or enhancement. However, due to the limitations of sensing and control techniques, the lower limb exoskeleton is still challenging to achieve a large-scale popularization and application. Therefore, this paper investigated the literature regarding the sensing and control of lower limb exoskeletons in recent years and studied the influences of different sensor signals and controller modeling on the exoskeleton performance. In addition, the current research challenges of insufficient stability and comfort in lower limb exoskeleton control are discussed, and possible innovative insights of functional material-based actuation, invasive and epidermal electronic sensing, and data-driven deep learning are analyzed in-depth. Some future research directions of the exoskeleton control are also provided to facilitate the further development of the exoskeleton control.

Functionally graded lattice structures are gaining increasing attention due to their potential to enable the customization of the structural response and development of multi-functional applications. However, some grading methods may lead to weak layers or discontinuous unit cells. These problems can be overcome by varying the morphology, but the mechanical performance is only slightly improved, limiting the application of lattice structures. This work proposes a bidirectionally graded lattice structure, wherein the gradient design is simultaneously implemented in parallel and perpendicularly to the load direction. Experimental samples fabricated through laser powder bed fusion (L-PBF) and using PA2200 as the matrix material, were subjected to quasi-static compression tests. The results showed that the bidirectionally graded lattice structure attains a significantly higher compressive modulus, yield stress, and plateau stress (59.8%, 43.0%, and 33.9% higher, respectively) compared with a unidirectionally graded lattice structure. Moreover, a proposed stiffness prediction method was appropriate for effectively estimating the modulus of graded body-centered cubic lattice structures, which combined with the understanding of the influence of gradient parameters, allows the realization of a tailored structural performance. In conclusion, the proposed bidirectionally graded strategy and experimental findings provide an effective reference for the design of multi-functional lightweight additive manufactured parts.

Lattice structures’ performance is directly determined by the topological structure and arrangement of cells. Here, we propose a lattice structure design approach that generates predictable mechanical properties by adjusting the three-dimensional posture and mirror arrays of cells. Specifically, the Euler angle (α β γ) is introduced to accurately control the three rotational degrees of freedom of the orthogonal unit cell. Then, a new unit cell with symmetric characteristics composed of multiple primitive rotation units is constructed by mirror operation, which is called super variable pose Octahedral Structures (SVPOS). The mathematical model of SVPOS topological structure is established, the mapping relationship between Euler Angle and relative density is deduced, and the mechanical response of structures with different Euler angles is studied. The results show that Structure of α = β = γ = 30˚ obtained the best performance, and the elastic modulus, compressive strength, and energy absorption at 50% strain of it are 553.1%, 471.9% and 529% of that of the octahedral, respectively. The new lattice structure can be obtained by adjusting the Euler Angle, its relative density and performance can be better predicted, which can provide experimental and theoretical basis for the design of lattice structures that meet different requirements.

Path planning is particularly important for Autonomous Underwater Vehicles (AUVs) in the marine environments. Due to the existence of flow fields, many conventional path planning methods are not effective. As the flow distributions vary slowly in large spatial scales, this paper considers the influence of static non-uniform vector field and studies the time-optimal path planning of AUV. The method proposed in this paper is called GK-OPM (Graph and K-means based Optimization Method). GK-OPM generates initial paths for minimum-time path optimization using digraph and K-means method, which benefit optimality and efficiency, respectively. To discuss the parameters in GK-OPM and compare the performance with genetic algorithm (GA) and particle swarm optimization (PSO), Monte Carlo simulation is carried out under the ocean currents simulated by the Lamb-vertex function. The feasibility is verified on discrete ocean data and three-dimensional environments, too. The results show that GK-OPM has about 6–8 times better efficiency than GA and PSO and maintains optimality at the same time.

It is vital to develop lattice structures with excellent performance in structural lightweight and multi-functional applications. However, the inherent single mechanical response of the lattice structure limits its application to different physical scenarios. In this study, to achieve the tailored mechanical properties adjustment, we propose a method for creating lattice structures with varying morphology and relative density by adjusting the geometric parameters of the lattice unit cell. A theoretical model for the preliminary prediction of mechanical properties was established, and a uniaxial quasi-static compression experiment was performed on Ti-6Al-4V lattice samples fabricated by laser powder bed fusion. Additionally, the compressive response of these lattice structures was analyzed by numerical simulation. The results show that the adjusting geometric parameters can achieve various heterogeneous mechanical responses, including shear band failure and uniform compression buckling failure. Furthermore, the mechanical properties can be realized in a larger range of compressive modulus from 77.04 MPa to 1073.5 MPa, and compressive strength from 3.96 MPa to 89.23 MPa. Therefore, the customized requirements of structural load-bearing capacity (large modulus and high strength) and energy absorption (stable platform stage) can be met.

The application of Middle-sized Car-like Robots (MCRs) in indoor and outdoor road scenarios is becoming broader and broader. To achieve the goal of stable and efficient movement of the MCRs on the road, a motion planning algorithm based on the Hybrid Potential Field Model (HPFM) is proposed in this paper. Firstly, the artificial potential field model improved with the eye model is used to generate a safe and smooth initial path that meets the road constraints. Then, the path constraints such as curvatures and obstacle avoidance are converted into an unconstrained weighted objective function. The efficient least-squares & quasi-Newton fusion algorithm is used to optimize the initial path to obtain a smooth path curve suitable for the MCR. Finally, the speed constraints are converted into a weighted objective function based on the path curve to get the best speed profile. Numerical simulation and practical prototype experiments are carried out on different road scenes to verify the performance of the proposed algorithm. The results show that re-planned trajectories can satisfy the path constraints and speed constraints. The real-time re-planning period is 184 ms, which demonstrates the proposed approach’s effectiveness and feasibility.

Graded lattice structures have been paid wide attention in the engineering and biological fields due to their excellent energy absorption capacity and variable porosity characteristics. Based on the size-graded lattice structure, laser powder bed fusion is utilized to manufacture the corresponding Ti-6Al-4 V lattice samples. Then, the quasi-static compression experiment is conducted and a predictive model for its mechanical properties is established accordingly. Also, its dynamic fatigue behavior is studied, and the influence of sandblasting and gradient direction on its mechanical response is evaluated. The results show that excellent mechanical properties and energy absorption capacity is exhibited in the vertical graded (VG) structure. Compared to the uniform structure, its elastic modulus and energy absorption are increased by 17.53% and 59.43%, respectively. The compression response of the radial graded (RG) structure is similar to that of the uniform structure, with minor changes on the mechanical properties and energy absorption capacity. However, the fatigue performance of the RG structure is better than that of the VG structure. With appropriate mechanical properties and changes in pores, this graded structure can simulate the changing physical and chemical properties of natural bone. Therefore, it has great potentiality in the application of bone implants.

The variable stiffness actuator (VSA) can absorb and reuse positive–negative power between the load and the motor, which can enhance the actuating efficiency of robotic joints and improve their impact resistance. Typical VSAs mainly adopted a motor-mechanism system into the elastomer in addition to the main actuating motor to adjust elastomer stiffness, which might limit practical effects due to large mass and inertial of the variable stiffness elastomer. This article proposes a new type of a pneumatic variable stiffness actuator (PVSA), which uses a rotating cylinder and compressed gas to form a lightweight pneumatic elastomer, the stiffness of which could be adjusted via a remote pressure controlling system, thus improving the mass distribution of the VSA in lightweight space-constrained actuation. In addition, the PVSA could also be integrated with metal springs to increase its stiffness range and torque bandwidth, further improving its practical application prospect. The influence of the friction, the backlash, and the temperature on PVSA performance are theoretically and experimentally analyzed, and its position, torque, and stiffness control performance under variable situations are tested and verified through multiple simulations and experiments. The results indicate that the PVSA can provide expected actuation performance with effective remote stiffness adjustment capability.

Energy consumption and acoustic noise can be significantly reduced through perching in the sustained flights of small Unmanned Aerial Vehicles (UAVs). However, the existing flying perching robots lack good adaptability or loading capacity in unstructured environments. Aiming at solving these problems, a deformable UAV perching mechanism with strong adaptability and high loading capacity, which is inspired by the structure and movements of birds' feet, is presented in this paper. Three elastic toes, an inverted crank slider mechanism used to realize the opening and closing movements, and a gear mechanism used to deform between two configurations are included in this mechanism. With experiments on its performance towards different objects, Results show that it can perch on various objects reliably, and its payload is more than 15 times its weight. By integrating it with a quadcopter, it can perch on different types of targets in outdoor environments, such as tree branches, cables, eaves, and spherical lamps. In addition, the energy consumption of the UAV perching system when perching on objects can be reduced to 0.015 times that of hovering.