The structural characteristics of the surfaces of sharkskin have great infl uence on their aerodynamic performance. It has been 
proved that the sharkskin’s ribbed structure can improve the aerodynamic performance of the parts up to 10%. At present, the 
main processing methods for this structure are laser, rolling, etc., which have low effi ciency and poor surface integrity. Belt 
grinding is widely used in the surface grinding and polishing. It plays an important role in improving the surface integrity 
and can realize the micro-structure machining at the same time. To achieve drag reduction, based on the characteristics of 
drag reduction of Bionic-Ribbed Structures (BRS), diff erent BRS (V, trapezoid and wave) on a blade were processed and 
studied. First, this paper introduces the theory of drag reduction induced by BRS and processing methods of diff erent BRS 
on a blade by belt grinding, and carried out the verifi cation of the belt-grinding methods. Then, diff erent BRS models were 
established on the blade with diff erent tip angles, and the aerodynamic performance was analyzed through simulation. It 
was found that the low-velocity layer near the BRS decreased when tip angle increased. Its wall shear stress also increased 
and tip angle of 45o had the best performance regardless of which BRS was. Some suggestions were given for belt grinding. 
The velocity along height from valley of BRS and velocity streamline was demonstrated. Secondary vortex was observed. 
Velocity gradient and vortex were the main reasons for the diff erence of wall shear stress.

Soft robots have unique advantages over traditional rigid robots and have broad application prospects in many fi elds. To 
expand their bioinspired applications, we propose a novel Soft Pneumatic Actuator (SPA) associated with spiral confi guration inspired by the structure and unwinding motion of the seahorse tail. Diff erent from bending motion of common soft 
actuators, the spiral SPA can generate unwinding motion as input air pressure increases. First, to explore the eff ect of diff erent initial spiral types on unwinding performance, three typical spiral SPAs are designed and simulated while keeping the 
outside arc of actuator body constant. Second, a static model of the spiral SPA is established by combining the hyperelastic 
material model, geometric relationships, and virtual work principle. To improve model accuracy, two geometric correction 
parameters are employed and their physical signifi cance is analyzed by fi nite element simulations. Third, a prototype of the 
logarithmic spiral SPA (Log_spiral SPA) is fabricated and a Fiber Bragg Grating (FBG) sensor array is designed to detect and 
reconstruct unwinding shapes of the prototype. Finally, the unwinding performance, static model and output force capability 
of the prototype are tested and verifi ed. Furthermore, we discuss prospects for this novel spiral SPA and test its practical 
applications in inchworm-like motion, assisting fi nger rehabilitation and object capture.

Motivated by optimal combination of paired wings configuration and stroke-plane inclination in biological flapping flights that can achieve high aerodynamic performance, we propose a biomimetic rotor-configuration design to explore optimal aerodynamic performance in multirotor drones. While aerodynamic interactions among propellers in multirotor Unmanned Aerial Vehicles (UAVs) play a crucial role in lift force production and Figure of Merit (FM) efficiency, the rotor-configuration effect remains poorly understood. Here we address a Computational Fluid Dynamics (CFD)-based study on optimal aerodynamic performance of the rotor-configuration in hovering quadrotor drones with a specific focus on the aerodynamic effects of tip distance, height difference and tilt angle of propellers. Our results indicate that the tip distance-induced interactions can most alter lift force production and hence lead to remarked improvement in FM, and the height difference also plays a key role in improving aerodynamic performance, while the tilt angle effect is less important. Furthermore, we carried out an extensive analysis to explore the optimal aerodynamic performance of the rotor-configuration over a broad parameter space, by combining the CFD-based simulations and a novel surrogate model. We find that a rotor-configuration with a large tip distance and some height difference with zero tilt angle is capable of optimizing both lift force production and FM, which could offer a novel optimal design as well as maneuver strategy for multirotor UAVs.

Venus fl ytrap can sense the very small insects that touch its tactile receptors, known as trigger hairs, and thus capture prey 
to maintain its nutrient demand. However, there are few studies on the trigger hair and its morphological structure and 
material properties are not fully understood. In this study, the trigger hair is systematically characterized with the help of 
diff erent instruments. Results show that trigger hair is a special cantilever beam structure and it has a large longitudinal 
diameter ratio. Besides, it is composed of a hair lever and a basal podium, and there is a notch near the hair base. The crosssection of the trigger hair is approximately a honeycomb structure, which is composed of many holes. Methods to measure 
mechanical properties of trigger hair are introduced in this paper. Based on the mechanical tests, trigger hair proved to be 
a variable stiff ness structure and shows a high sensitivity to the external force. These features can provide supports for the 
understanding of the high-sensitivity sensing mechanism of trigger hairs from the perspective of structure and material, and 
off er inspirations for the development of high-performance tactile sensors.

The utilisation of oil palm fibre (OPF) and pineapple leaf fibres (PALF) as reinforcement materials for bio-phenolic composites is growing especially in automotive lightweight applications. The major aim of this current study is to investigate the influence of alkali (Ca(OH)2 treatment on pure and hybrid composites. The effects of enhancements in chemical interactions were evaluated by the Fourier-Transform Infrared Spectrometer (FTIR). Dynamic Mechanical Analysis (DMA) and Thermogravimetric Analysis (TGA) performance of untreated reinforcements (OPF and PALF) and treated (OPF/OPF) composites at varying temperature and noted sufficient interfacial bonding contributing towards the improvements in thermal stability. From DMA results, the storage modulus improved with treated composites while the damping factor was reduced. Furthermore, the treated hybrid composites exhibited significant improvements in thermal stability compared to untreated fibre composites. The results indicated that alkali calcium hydroxide (Ca(OH2(:T) incorporation in hybrid composites (OPF/PALF) results in increased tensile strength and modulus among all composites. Similarly, the alkali-treated (Ca (OH)2)-treated pure composite (T/50%PALF), and hybrid composites (T/1OPF.1PALF) exhibited better flexural strength as compared with other composites. In contrast, the T/50% PALF showed higher flexural stress of 78.2 MPa, while the flexural modulus was recorded at 6503 MPa. It can be proposed from the findings of this study that the alkali treatment (5%Ca(OH)2) can be utilised to improve the strength and efficiency of agriculture biomass to be used as reinforcements in composites. Additionally, the hybridisation of bio-fibre composites has the potential as a novel variety of biodegradable and sustainable composites appropriate for several industrial and engineering applications.

This paper proposes a down-stroke abrasive belt grinding under micro feeding for noise reduction surface. Firstly, a physical model of processing under micro feeding for noise reduction structure was established. Based on the flexible contact characteristics of abrasive belt grinding and Hertz contact theory, a mathematical model suitable for this method was established, considering vibration and abrasive belt wear. Secondly, a simulation analysis was carried out. Then, an experimental platform was built to analyze the influence of process parameters on surface roughness and surface microstructure, with the model verified. Finally, the propeller with pit structure was simulated, and the noise reduction performance of the propeller under this method and general abrasive belt grinding was compared and analyzed. The results show that the maximum error of the model based on proposed method does not exceed 10%, and the coincidence degree of the minimum error point can reach 90% at lower feed speed and higher linear velocity of the abrasive belt. The noise reduction effect of the propeller with pit-shaped surfaces can reach 35%. Through the above analysis, the proposed method can be used for the processing of noise reduction surfaces. 

As the basis of flight behavior, the initiation process of insect flight is accompanied by a transition from crawling mode to flight mode, and is clearly important and complex. Insects take flight from a vertical surface, which is more difficult than takeoff from a horizontal plane, but greatly expands the space of activity and provides us with an excellent bionic model. In this study, the entire process of a butterfly alighting from a vertical surface was captured by a high-speed camera system, and the movements of its body and wings were accurately measured for the first time. After analyzing the movement of the center of mass, it was found that before initiation, the acceleration perpendicular to the wall was much greater than the acceleration parallel to the wall, reflecting the positive effects of the legs during the initiation process. However, the angular velocity of the body showed that this process was unstable, and was further destabilized as the flight speed increased. Comparing the angles between the body and the vertical direction before and after leaving the wall, a significant change in body posture was found, evidencing the action of aerodynamic forces on the body. The movement of the wings was further analyzed to obtain the laws of the three Euler angles, thus revealing the locomotory mechanism of the butterfly taking off from the vertical surface. 

Numerical studies are conducted to explore the noise reduction effect of leading-edge tubercles inspired by humpback whale flippers. Large eddy simulations are performed to solve the flow field, while the acoustic analogy theory is used for noise prediction. In this paper, a baseline airfoil with a straight leading-edge and three bionic airfoils with tubercled leading-edges are simulated. The tubercles have sinusoidal profiles and the profiles are determined by the tubercle wavelength and amplitude. The tubercles used in this study have a fixed wavelength of 0.1c with three different amplitudes of 0.1c, 0.15c and 0.2c, where c is the mean chord of the airfoil. The freestream velocity is set to 40 m/s and the chord based Reynolds number is 400,000. The predicted flow field and acoustic field of the baseline airfoil are compared against the experiments and good agreements are found. A considerable noise reduction level is achieved by the leading-edge tubercles and the tubercle with larger amplitude can obtain better noise reduction. The underlying flow mechanisms responsible for the noise reduction are analyzed in detail.

As the essential technology of human-robotics interactive wearable devices, the robotic knee prosthesis can provide above-knee amputations with functional knee compensations to realize their physical and psychological social regression. With the development of mechanical and mechatronic science and technology, the fully active knee prosthesis that can provide subjects with actuating torques has demonstrated a better wearing performance in slope walking and stair ascent when compared with the passive and the semi-active ones. Additionally, with intelligent human-robotics control strategies and algorithms, the wearing effect of the knee prosthesis has been greatly enhanced in terms of stance stability and swing mobility. Therefore, to help readers to obtain an overview of recent progress in robotic knee prosthesis, this paper systematically categorized knee prostheses according to their integrated functions and introduced related research in the past ten years (2010?2020) regarding (1) mechanical design, including uniaxial, four-bar, and multi-bar knee structures, (2) actuating technology, including rigid and elastic actuation, and (3) control method, including mode identification, motion prediction, and automatic control. Quantitative and qualitative analysis and comparison of robotic knee prosthesis-related techniques are conducted. The development trends are concluded as follows: (1) bionic and lightweight structures with better mechanical performance, (2) bionic elastic actuation with energy-saving effect, (3) artificial intelligence-based bionic prosthetic control. Besides, challenges and innovative insights of customized lightweight bionic knee joint structure, highly efficient compact bionic actuation, and personalized daily multi-mode gait adaptation are also discussed in-depth to facilitate the future development of the robotic knee prosthesis.

Investigating the interaction between fins can guide the design and enhance the performance of robotic fish. In this paper, we take boxfish as the bionic object and discuss the effect of coupling motion gaits among the two primary propulsors, pectoral and caudal fins, on the heading stability of the body. First, we propose the structure and control system of the bionic boxfish prototype. Second, using a one/two-way fluid–structure interaction numerical method, we analyse the key parameters of the prototype and discuss the influence of pectoral and caudal motion gaits on the hydrodynamic performance. Finally, effect of the pectoral and caudal interactions on heading stability of the prototype is systematically analyzed and verified in experiments. Results show that the course-deviating degree, oscillation amplitudes of yawing, rolling, and pitching exhibited by the prototype are smaller than that caused by single propulsor when the motion gaits of both pectoral and caudal fins are coordinated in a specific range. This paper reveals for the first time the effect of interactions between pectoral and caudal fins, on the stability of body's course by means of Computational Fluid Dynamics and prototype experiments, which provides an essential guidance for the design of robotic fish propelled by multi-fins.

Inspired by nature, a superhydrophobic and magnetic melamine sponge (BFSM-MF) was fabricated by a one-step dip-coating 
method. Aiming at replacing nano-Fe 3 O 4 particles with a complex preparation process and high cost, the commercial and 
cheap Fe 3 O 4 originated from magnetite was employed as a magnetic substance. To acquire superhydrophobicity, the hierarchical mirco/nano-sized structure with low surface energy was mainly contributed by bonding hydrophobic Fe 3 O 4 and 
graphene with silicone resin onto the surface of the melamine sponge. The results demonstrated that the water and oil static 
contact angle values of BFSM-MF were 160° and 0°, revealing that BFSM-MF was superhydrophobic and super-oleophilic. 
Moreover, the self-cleaning ability, magnetic-driven oil absorption ability and continuous oil–water separation performance 
of BFSM-MF have also been evaluated. As expected, BFSM-MF possessed magnetic-driven oil absorption ability and the 
oil–water separation effi ciency for light oil reaches 98% ± 1%. In addition, the adsorption capacity and recycling performance 
of diff erent organic solvents were systematically investigated. Therefore, the development of biomimetic, fl uorine-free and 
superhydrophobic foam with magnetic-driven eff ect has potential application value in marine oil spill treatment and separation of domestic oil pollution.

A subsystem impactor test for pedestrian lower limb injury evaluation has been brought in China New Car Assessment Protocol (CNCAP). Concerning large anthropometric differences of the people from different countries, the present study aims to establish and validate a finite element lower limb model representing 50th Chinese male size for pedestrian safety research, then compare its biomechanical responses with the general models currently in wide use in the world for pedestrian safety evaluation. Concerning the vehicle-pedestrian impact loading environment, the previously developed lower limb model with three-dimensional muscles was adjusted and validated through the related experiments. Then, the biomechanical responses of the validated model were compared with the Total Human Model for Safety (THUMS) and Advanced Pedestrian Legform Impactor (aPLI) models by combing with four typical vehicles. The results showed that both consistency and significant differences of biomechanical responses existed between the present model and the other two models. The injury measurements of the thigh region of the present model showed extremely large differences with the other two models, while the tibia and Medial Collateral Ligament (MCL) injury measurements show similar values. Thus, it can be concluded that directly using the aPLI or THUMS models for Chinese pedestrian safety evaluation is not robust concerning both kinematic responses and injury measurements.

The aim of this study is to systematically reveal the differences in the biomechanics of 16 hand regions related to bionic picking of tomatoes. The biomechanical properties (peak loading force, elastic coefficient, maximum percentage deformation and interaction contact mechanics between human hand and tomato fruit) of each hand region were experimentally measured and covariance analyzed. The results revealed that there were significant variations in the assessed biomechanical properties between the 16 hand regions (p?<?0.05). The maximum pain force threshold (peak loading force in I2 region) was 5.11 times higher than the minimum pain force threshold (in Th1 region). It was found that each hand region in its normal direction can elastically deform by at least 15.30%. The elastic coefficient of the 16 hand regions ranged from 0.22 to 2.29 N mm?1. The interaction contact force acting on the fruit surface was affected by the selected human factors and fruit features. The obtained covariance models can quantitatively predict all of the above biomechanical properties of 16 hand regions. The findings were closely related to hand grasping performance during tomato picking, such as soft contact, surface interaction, stable and dexterous grasping, provided a foundation for developing a high-performance tomato-picking bionic robotic hand.

Medical implant from different materials such as metals, ceramics, polymers and composites have gained a lot of research attraction due to wide applications in medical industry for treatment, surgical operations and preparing artificial body parts. In this work, we highlight a comprehensive review of medical implant mechanism, various types of implant materials, factors affecting the performance of implant and different characterization techniques. This review provides an overall summary of the state-of-the-art progress on various interesting and promising material-based medical implant. Finally, few new prospects are explained from the established theoretical and experimental results for real-life applications. This study is expected to promote extended interest of scientists and engineers in recent trend of modern biomaterials based medical implant.

Humans have long desired but never achieved the capacity to climb walls. The fundamental reason is that human hands and feet cannot climb vertical walls like geckos and bees. Animals lacking an adhesive structure can use the body’s dynamic effect to climb walls. Here we investigated the dynamic wall climbing behavior of individuals who cannot remain stationary on the vertical wall. Taking the domestic cat as the experimental object, we constructed an experimental platform as the obstacle for the cat to climb the wall. Our research indicated that domestic cats must meet the following physical conditions to do dynamic vertical wall climbing: vertical obstacles must have nonvertical surfaces, a horizontal run-up, and contact with nonvertical surfaces before the vertical speed reduces to zero. Here we proposed a dynamic vertical wall climbing model with three contact states based on an investigation of domestic cats’ dynamic wall climbing behavior and the LIP model. The motion range of the LIP model’s generalized angular coordinates varies depending on the contact state. The horizontal run-up action can improve the jumping height and obtain horizontal speed. When making contact with the vertical surface of the obstacle, the motion inertia in the horizontal direction can produce a reaction force on the contact surface, which can compensate for the influence of some gravity. This alternating contact strategy lets cats switch different initial and end contact angles. This investigation clarifies the essential process underlying animals’ dynamic vertical wall climbing and establishes the theoretical foundation for the legged robot to do dynamic vertical wall climbing.

Brass is widely used in machinery, electronic appliances and emerging industries. The corrosion resistance of laser-induced 
superhydrophobic surface of brass needs to be improved. In recent years, bionic surface with slippery coating has attracted 
much attention because of its excellent corrosion inhibition performance. Here, we fi rst prepared the superhydrophobic 
surface of brass by nanosecond laser ablation combined with fl uoroalkyl silane modifi cation, and then injected silicone oil 
into the prepared superhydrophobic matrix to obtain a slippery coating surface. PDP and EIS tests in 3.5 wt.% NaCl solution showed that the corrosion resistance of the slippery surface was better than that of the superhydrophobic surface. This 
study can play a certain role in promoting the development of metal anticorrosive coating and is of great signifi cance in the 
preparation of slippery surface by laser induction, and provides a convenient and eff ective means for metal anticorrosion in 
the industrial fi eld.

Due to the unique locomotion, the head-shaking problem of biomimetic robotic fish inevitably occurs during rectilinear locomotion, which strongly hinders its practical applications. In this paper, we experimentally study this problem by proposing the method of coordination control between the caudal fin and anal fin. First, an untethered biomimetic robotic fish, equipped with an anal fin, a caudal fin and two pectoral fins, is developed as the experimental platform. Second, a Central Pattern Generator (CPG)-based controller is used to coordinate the motions of the anal fin and caudal fin. Third, extensive experiments are conducted to explore different combinations of the flapping frequencies, the flapping amplitudes, and the phase differences between the anal fin and caudal fin. Notably, through proper control of the anal fin, the amplitude of the yaw motion can be as small as 4.32°, which sees a 65% improvement compared to the scenario without anal fin, and a 57% improvement compared to that with a stationary anal fin. This paper provides a novel way to alleviate the head-shaking problem for biomimetic robotic fish, and first test this method on an untethered, freely swimming robotic platform, which can shed light on the development of underwater robotics.

Inspired by the morphology characteristics and the locomotion mechanisms of the earthworm, and the snakes’ morphology characteristics and motivated by the demands for multi-modal locomotion robots in variable working environments, this paper presents a novel bi-modal robot named as Snake-Worm Locomotion Robot (SWL-Robot). Two fundamentally different locomotion mechanisms, the earthworm’s peristaltic rectilinear locomotion and the snake’s lateral undulation, are synthesized in the SWL-Robot design. In detail, the SWL-Robot consists of six earthworm-like body segments interconnected by rotational joints and a head segment equipped with a couple of independently driven wheels. By actuating the segments following a peristaltic wave-like gait, the robot as a whole could perform earthworm-like rectilinear crawling. The robot could also perform snake-like undulatory locomotion driven by differential motions of the wheels at the head segment. To understand the relationship between the design parameters and the robotic locomotion performance, kinematic models of the SWL-Robot corresponding to the two locomotion modes are developed. Rich locomotion behaviors of the SWL-Robot are achieved, including the peristaltic locomotion inside a tube, multiple planar motions on a flat surface, and a hybrid motion that switches between the tube and the flat surface. It shows that the measured trajectories of the SWL-Robot agree well with the theoretical predictions. The SWL-Robot is promising to be implemented in tasks where both tubular and flat environments may be encountered.

In recent years, sEMG (surface electromyography) signals have been increasingly used to operate wearable devices. The development of mechanical lower limbs or exoskeletons controlled by the nervous system requires greater accuracy in recognizing lower limb activity. There is less research on devices to assist the human body in uphill movements. However, developing controllers that can accurately predict and control human upward movements in real-time requires the employment of appropriate signal pre-processing methods and prediction algorithms. For this purpose, this paper investigates the effects of various sEMG pre-processing methods and algorithms on the prediction results. This investigation involved ten subjects (five males and five females) with normal knee joints. The relevant data of the subjects were collected on a constructed ramp. To obtain feature values that reflect the gait characteristics, an improved PCA algorithm based on the kernel method is proposed for dimensionality reduction to remove redundant information. Then, a new model (CNN?+?LSTM) was proposed to predict the knee joint angle. Multiple approaches were utilized to validate the superiority of the improved PCA method and CNN-LSTM model. The feasibility of the method was verified by analyzing the gait prediction results of different subjects. Overall, the prediction time of the method was 25 ms, and the prediction error was 1.34?±?0.25 deg. By comparing with traditional machine learning methods such as BP (backpropagation) neural network, RF (random forest), and SVR (support vector machine), the improved PCA algorithm processed data performed the best in terms of convergence time and prediction accuracy in CNN-LSTM model. The experimental results demonstrate that the proposed method (improved PCA?+?CNN-LSTM) effectively recognizes lower limb activity from sEMG signals. For the same data input, the EMG signal processed using the improved PCA method performed better in terms of prediction results. This is the first step toward myoelectric control of aided exoskeleton robots using discrete decoding. The study results will lead to the future development of neuro-controlled mechanical exoskeletons that will allow troops or disabled individuals to engage in a greater variety of activities.

Individuals with cerebral palsy and muscular dystrophy often lack fi ne motor control of their fi ngers which makes it diffi cult 
to control traditional powered wheelchairs using a joystick. Studies have shown the use of surface electromyography to steer 
powered wheelchairs or automobiles either through simulations or gaming controllers. However, these studies signifi cantly 
lack issues with real world scenarios such as user’s safety, real-time control, and effi ciency of the controller mechanism. 
The purpose of this study was to design, evaluate, and implement a hybrid human–machine interface system for a powered 
wheelchair that can detect human intent based on artifi cial neural network trained hand gesture recognition and navigate 
a powered wheelchair without colliding with objects around the path. Scaled Conjugate Gradient (SCG), Bayesian Regularization (BR), and Levenberg Marquart (LM) supervised artifi cial neural networks were trained in offl ine testing on eight 
participants without disability followed by online testing using the classifi er with highest accuracy. Bayesian Regularization 
architecture showed highest accuracy at 98.4% across all participants and hidden layers. All participants successfully completed the path in an average of 5 min and 50 s, touching an average of 22.1% of the obstacles. The proposed hybrid system 
can be implemented to assist people with neuromuscular disabilities in near future.

Wall climbing robots can be used to undertake missions in many unstructured environments. However, current wall climbing robots have mobility difficulties such as in the turning or accelarating. One of the main reasons for the limitations is the poor flexibility of the spines. Soft robotic technology can actively enable structure deformation and stiffness varations, which provides a solution for the design of active flexible spines. This research utilizes pneumatic soft actuators to design a flexible spine with the abilities of actively bending and twisting by each joint. Using bending and torsion moment equilibriums, respectively, from air pressure to material deformations, the bending and twisting models for a single actuator with respect to different pressure are obtained. The theoretical models are verified by finite-element method simulations and experimental tests. In addition, the bending and twisiting motions of single joint and whole spine are analytically modeled. The results show that the bionic spine can perform desired deformations in accordance with the applied pressure on specified chambers. The variations of the stiffness are also numerically assessed. Finally, the effectiveness of the bionic flexible spine for actively producing sequenced motions as biological spine is experimentally validated. This work demonstrated that the peneumatic spine is potential to improve the spine flexibility of wall climbing robot.

Hydrogel has been widely used in the research of bionic articular cartilage due to their similarity in structure and functional 
properties to natural articular cartilage. In this research, polyvinyl alcohol and betaine monomer were used as raw materials to prepare a high-strength double-network hydrogel by a combination of ultraviolet (UV) irradiation and freeze–thaw 
methods. The structure of samples was characterized by Fourier transform infrared spectroscopy and X-ray diff raction, 
and the morphology of the samples was characterized by scanning electron microscope and three-dimensional white light 
interferometer. In addition, we also studied the swelling ratio, water content, mechanical properties and tribological properties of the samples. We found that the addition of betaine monomer and the UV irradiation time had a positive eff ect on the 
mechanical properties and tribological properties of the samples.

Ladder climbing is a relatively new but practical locomotion style for robots. Unfortunately, due to their size and weight, ladder climbing by human-sized robots developed so far is struggling with the speedup of ladder climbing motion itself. Therefore, in this paper, a new ladder climbing gait for the robot WAREC-1R is proposed by the authors, which is both faster than the former ones and stable. However, to realize such a gait, a point that has to be taken into consideration is the deformation caused by the self-weight of the robot. To deal with this issue, extra hardware (sensor) and software (position and force control) systems and extra time for sensing and calculation were required. For a complete solution without any complicated systems and time only for deformation compensation, limb stiffness improvement plan by the minimal design change of mechanical parts of the robot is also proposed by the authors, with a thorough study about deformation distribution in the robot. With redesigned parts, ladder climbing experiments by WAREC-1R proved that both the new ladder climbing gait and the limb stiffness improvement are successful, and the reduced deformation is very close to the estimated value as well.

Lower extremity robotic exoskeletons (LEEX) can not only improve the ability of the human body but also provide healing treatment for people with lower extremity dysfunction. There are a wide range of application needs and development prospects in the military, industry, medical treatment, consumption and other fields, which has aroused widespread concern in society. This paper attempts to review LEEX technical development. First, the history of LEEX is briefly traced. Second, based on existing research, LEEX is classified according to auxiliary body parts, structural forms, functions and fields, and typical LEEX prototypes and products are introduced. Then, the latest key technologies are analyzed and summarized, and the research contents, such as bionic structure and driving characteristics, human–robot interaction (HRI) and intent-awareness, intelligent control strategy, and evaluation method of power-assisted walking efficiency, are described in detail. Finally, existing LEEX problems and challenges are analyzed, a future development trend is proposed, and a multidisciplinary development direction of the key technology is provided.

The intelligent knee prosthesis is capable of human-like bionic lower limb control through advanced control systems and artificial intelligence algorithms that will potentially minimize gait limitations for above-knee amputees and facilitate their reintegration into society. In this paper, we sum up the control strategies corresponding to the prevailing control objectives (position and impedance) of the current intelligent knee prosthesis. Although these control strategies have been successfully implemented and validated in relevant experiments, the existing deficiencies still fail to achieve optimal performance of the controllers, which complicates the definition of a standard control method. Before a mature control system can be developed, it is more important to realize the full potential for the control strategy, which requires upgrading and refining the relevant key technologies based on the existing control methods. For this reason, we discuss potential areas for improvement of the prosthetic control system based on the summarized control strategies, including intent recognition, sensor system, prosthetic evaluation, and parameter optimization algorithms, providing future directions toward optimizing control strategies for the next generation of intelligent knee prostheses.

During marine missions, AUVs are susceptible to external disturbances, such as obstacles, ocean currents, etc., which can easily cause mission failure or disconnection. In this paper, considering the strong nonlinearities, external disturbances and obstacles, the kinematic and dynamic model of bioinspired Spherical Underwater Robot (SUR) was described. Subsequently, the waypoints-based trajectory tracking with obstacles and uncertainties was proposed for SUR to guarantee its safety and stability. Next, the Lyapunov theory was adopted to verify the stability and the Slide Mode Control (SMC) method is used to verify the robustness of the control system. In addition, a series of simulations were conducted to evaluate the effectiveness of proposed control strategy. Some tests, including path-following, static and moving obstacle avoidance were performed which verified the feasibility, robustness and effectiveness of the designed control scheme. Finally, a series of experiments in real environment were performed to verify the performance of the control strategy. The simulation and experimental results of the study supplied clues to the improvement of the path following capability and multi-obstacle avoidance of AUVs.

In recent years, more and more creatures in nature have become the source of inspiration for people to study bionic soft robots. Many such robots appear in the public’s vision. In this paper, a Venus flytrap robot similar to the biological Venus flytrap in appearance was designed and prepared. It was mainly cast by Polydimethylsiloxane (PDMs) and driven by the flexible material of Ionic Polymer Metal Composites (IPMCs). Combining with ANSYS and related experiments, the appropriate voltage and the size of IPMC were determined. The results showed that the performance of the Venus flytrap robot was the closest to the biological Venus flytrap when the size of IPMC length, width and driving voltage reach to 3 cm, 1 cm and 5.5 V, respectively. Moreover, the closing speed and angle reached 8.22°/s and 37°, respectively. Finally, the fly traps also could be opened and closed repeatedly and captured a small ball with a mass of 0.3 g firmly in its middle and tip.

The aim of this study was to reconstruct surface porous structure with hundreds of micrometers and then bio-mineralize Sr-doped Calcium Phosphate (Sr-doped CaP) on Polyetheretherketone (PEEK) profile to enhance its bioactivity. A surface porous structure was prepared on PEEK profile by embedding and acid-etching of SiO2 particles as porogen (SP-PEEK). Then the Sr-doped CaP was further decorated on the porous surface after sulfonation, introduction of Sr-doped CaP crystal seeds and bio-mineralization in 1.5 times simulated body fluid (BSSP-PEEK-CaP/Sr). It was feasible to reconstruct the surface porous structure with hundreds of micrometers on PEEK profile by the present method without damaging its mechanical properties. The Sr-doped CaP crystal seeds effectively promoted the bio-mineralization of bio-inertness PEEK. All as-prepared PEEK did not inhibit the proliferation of cells. ALP of bio-mineralized groups was significantly increased than that of the other groups. The BSSP-PEEK-CaP/Sr obviously affected the morphology and promoted the adhesion and spreading of cells. As a result, the cyto-biocompatibity and bioactivity of PEEK were improved after bio-mineralization. Sr-doped CaP on PEEK most likely was beneficial for cells, which was associated with the increasing of the hydrophilicity on PEEK. This study provided a candidate method to improve the osteogenesis of PEEK implants. 

High harvesting success rate is part of the key technologies for robotic cherry tomato harvesting, which is closely related to the structural design of the end-effector. To obtain a high success rate of fruit harvesting, this paper presents a compliant end-effector with bio-inspired tarsus compliant gripper inspired by the structure and mechanics of the tarsal chain in the Serica orientalis Motschulsky. Response Surface Methodology (RSM) based on Box Behnken Design (BBD) technique has been used to optimize the key structural parameters of the bionic compliant end-effector for achieving the expected results in pulling pattern for robotic cherry tomato harvesting. Experiments were designed by maintaining three levels of four process parameters—Length of the Offset Segment Tarsomere (OSTL), Angle of the Inclined Segment Tarsomere (ISTA), Thickness of the Extended Segment Tarsomere (ESTT) and Length of the Extended Segment Tarsomere (ESTL). According to the optimization analysis results, the best parameter combination is OSTL 23 mm, ISTA 14°, ESTT 5.0 mm, ESTL 23 mm. Besides, the harvesting performance of the optimized bionic compliant end-effector was verified by experiments. The results indicated the harvesting success rate of fruits with different equatorial diameters was not less than 76%.

Variable Stiffness Actuator (VSA) is the core mechanism to achieve physical human–robot interaction, which is an inevitable development trend in robotic. The existing variable stiffness actuators are basically single degree-of-freedom (DOF) rotating joints, which are achieving multi-DOF motion by cascades and resulting in complex robot body structures. In this paper, an integrated 2-DOF actuator with variable stiffness is proposed, which could be used for bionic wrist joints or shoulder joints. The 2-DOF motion is coupling in one universal joint, which is different from the way of single DOF actuators cascade. Based on the 2-DOF orthogonal motion generated by the spherical wrist parallel mechanism, the stiffness could be adjusted by varying the effective length of the springs, which is uniformly distributed in the variable stiffness unit. The variable stiffness principle, the model design, and theoretical analysis of the VSA are discussed in this work. The independence of adjusting the equilibrium position and stiffness of the actuator is validated by experiments. The results show that the measured actuator characteristics are sufficiently matched the theoretical values. In the future, VSA could be used in biped robot or robotic arm, ensuring the safety of human–robot interaction.

In the original Moth-Flame Optimization (MFO), the search behavior of the moth depends on the corresponding flame and the interaction between the moth and its corresponding flame, so it will get stuck in the local optimum easily when facing the multi-dimensional and high-dimensional optimization problems. Therefore, in this work, a generalized oppositional MFO with crossover strategy, named GCMFO, is presented to overcome the mentioned defects. In the proposed GCMFO, GOBL is employed to increase the population diversity and expand the search range in the initialization and iteration jump phase based on the jump rate; crisscross search (CC) is adopted to promote the exploitation and/or exploration ability of MFO. The proposed algorithm’s performance is estimated by organizing a series of experiments; firstly, the CEC2017 benchmark set is adopted to evaluate the performance of GCMFO in tackling high-dimensional and multimodal problems. Secondly, GCMFO is applied to handle multilevel thresholding image segmentation problems. At last, GCMFO is integrated into kernel extreme learning machine classifier to deal with three medical diagnosis cases, including the appendicitis diagnosis, overweight statuses diagnosis, and thyroid cancer diagnosis. Experimental results and discussions show that the proposed approach outperforms the original MFO and other state-of-the-art algorithms on both convergence speed and accuracy. It also indicates that the presented GCMFO has a promising potential for application.

To adapt to a complex and variable environment, self-adaptive camoufl age technology is becoming more and more important in all kinds of military applications by overcoming the weakness of the static camoufl age. In nature, the chameleon can 
achieve self-adaptive camoufl age by changing its skin color in real time with the change of the background color. To imitate 
the chameleon skin, a camoufl aged fi lm controlled by a color-changing microfl uidic system is proposed in this paper. The 
fi lm with microfl uidic channels fabricated by soft materials can achieve dynamic cloaking and camoufl age by circulating 
color liquids through channels inside the fi lm. By sensing and collecting environmental color change information, the control signal of the microfl uidic system can be adjusted in real time to imitate chameleon skin. The microstructure of the fi lm 
and the working principle of the microfl uidic color-changing system are introduced. The mechanism to generate the control 
signal by information processing of background colors is illustrated. “Canny” double-threshold edge detection algorithm 
and color similarity are used to analyze and evaluate the camoufl age. The tested results show that camoufl aged images have 
a relatively high compatibility with environmental backgrounds and the dynamic cloaking eff ect can be achieved.

Unexpected ice accumulation tends to cause many problems or even disasters in our daily life. Based on the superior electrothermal and photothermal function of the carbon nanotubes, we introduced a superhydrophobic/electrothermal/photothermal synergistically anti-icing strategy. When a voltage of 15 V was applied to the superhydrophobic sample, the surface 
could rapidly melt the ice layer (~ 3 mm thickness) within 530 s at the environmental temperature of ? 25 °C. When the 
near-infrared light (808 nm) irradiates on the superhydrophobic sample, the ice could be rapidly removed after 460 s. It was 
found that the superhydrophobicity helps the melted water to roll off immediately, and then solves the re-freeze problem the 
traditional surfaces facing. Moreover, the ice can be completely melted with 120 s when the superhydrophobic/electrothermal/
photothermal synergistically anti-icing strategy was utilized. To improve the mechanical robustness for practical application, 
both nanoscale carbon nanotubes and microscale carbon powders were utilized to construct hierarchical structure. Then 
these dual-scale fi llers were sprinkled onto the semi-cured elastomer substrate to prepare partially embedded structure. Both 
hierarchical structure and partially embedded structure were obtained after completely curing the substrate, which imparts 
excellent abrasion resistance (12.50 kPa, 16.00 m) to the prepared sample. Moreover, self-healable poly(urea–urethane) 
elastomer was introduced as the substrate. Thus, the cutted superhydrophobic sample can be mended by simply contacting 
at room temperature.

In nature, bees with damaged tongues are adapted to have a feat in collecting nectariferous sources in a large spectrum of 
concentrations (19%–69%) or viscosities (10 –3 Pa·s to 10 –1  Pa·s); however, eff ects of nectar property on compensated dipping behavior remain elusive. Combining the bee tongue anatomy, high-speed videography, and mathematical models, we 
investigate responses of honey bees with damaged tongues to fl uidic sources in various properties. We fi nd that, bees with 
80% damaged tongues are deprived of feeding capability and remarkably, the dipping frequency increases from 4.24 Hz to 
5.08 Hz while ingesting 25% sugar water when the tongue loses 0–30% in length, while declines from 5.08 to 3.86 Hz in case 
of 30% damaged tongue when sucrose concentration increases from 25% to 45%. We employ the energetic compensation 
rate and energetic utilization rate to evaluate eff ectiveness of the compensation from the perspective of energetic regulation. 
The mathematical model indicates that the energetic compensation rate turns higher in bees with less damaged tongues 
for ingesting dilute sugar water, demonstrating its capability of functional compensation for combined factors. Also, the 
tongue-damaged bees achieve the highest energetic utilization rate when ingesting ~ 30% sugar water. Beyond biology, the 
fi ndings may shed lights on biomimetic materials and technologies that aim to compensate for geometrical degradations 
without regeneration.

Inspired by the cockroach’s use of a pitch-roll mode traverses through narrow obstacles, we improve the RHex-style robot by adding two sprawl joints to adjust the body posture, and propose a novel pitch-roll approach that enables an RHex-style robot to traverse through two cylindrical obstacles with a spacing of 90 mm, about 54% body width. First, the robot can pitch up against the obstacle on the one side by the cooperation of its rear and middle legs. Then, the robot rotates one side rear leg to kick the ground fast, meanwhile the sprawl joint on the other side rotates inward to make the robot roll and fall forward. Finally, the robot can rotate the legs on the ground to move the body forward until it crosses the obstacles. In this article, both cylinder and rectangular columns are considered as the narrow obstacles for traversing. The experiments are demonstrated by using the proposed approach, and the results show that the robot can smoothly traverse through different narrow spaces.

In regenerative medicine, a scaffold is needed to provide physical support for the growth of cells at the injury site. Carbon composites are also widely used in biomedicine. This research aimed to see if (MoWCu)S/rGO could be used in peripheral and central neural regeneration as a carbon-based nanomaterial. This material was created using a one-step hydrothermal process. We used Scanning Electron Microscopy with Energy Dispersive X-ray analysis (SEM–EDX), X-ray diffraction, and Field-Emission Scanning Electron Microscopy (FE-SEM) to describe it. The researchers used animal models of spinal cord injury and sciatic nerve injury to assess its effect as a scaffold of anti-inflammatory and electrical conductivity. The Basso Beattie Bresnahan locomotor rating scale and von Frey Filament were used to assess neuronal function after (MoWCu)S/rGO transplantation. In addition, the expression of p75 NTR and neurotrophic factors (BDNF, NT3, and NGF) mRNA in the experimental rats nerve was compared to the normal ones using Real-Time RT-qPCR. In the experimental groups, the use of (MoWCu)S/rGO resulted in a significant increase in neurotrophic factor gene expression, while p75 NTR was inversely decreased. In conclusion, we found that the nerve regeneration activity of the (MoWCu)S/rGO scaffold in rat models significantly increased motor function recovery in the treated groups. Furthermore, the current study explained the response of this composite to inflammatory neurodegenerative diseases. (MoWCu)S incorporation in graphene is thought to have excellent properties and may be used in regenerative medicine.

Portability is an important performance to the design of exoskeleton for rehabilitation and assistance. However, the structure of traditional exoskeletons will decrease the portability because of their heavy weight and large volume. This paper proposes a novel bionic portable elbow exoskeleton based on a human-exoskeleton gravity-balancing coupled model. The variable stiffness characteristics of the coupled model is analyzed based on the static analysis. In addition, the optimization of human-exoskeleton joint points is analysis to improve the bionic motor characteristics of the exoskeleton. Theoretical prototype is designed and its driving power and dynamic performance are analyzed. Then, a prototype is designed and manufactured with a total weight of 375 g. The merits of driving power reducing is verified by simulation and the isokinetic experiments. The simulation and isokinetic results show that the driving torque and the driving power of the subject were significantly decreased with wearing the proposed exoskeleton. The driving torques are reduced 79.28% and 57.38% from the simulation results and isokinetic experiment results, respectively. The driving work of experiment was reduced by 56.5%. The development of the novel elbow exoskeleton with gravity-balancing mechanism can expand the application of exoskeleton in home-based rehabilitation.

The underactuated fingers used in prosthetic hands account for a large part of design consideration in anthropomorphic prosthetic hand design. There are considerable numbers of designs available for underactuated prosthetic fingers in literature but, emulating the anthropomorphic flexion movement is still a challenge due to the complex nature of the motion. To address this challenge, a hybrid mechanism using both linkage-based mechanism and tendon-driven actuation has been proposed in this paper. The presented mechanism includes a novel offset slider-crank-based finger that has been designed using a combination of different lengths of cranks and connecting rods. The prototypes of both the new mechanism and the conventional tendon-driven mechanism are constructed and compared experimentally based on interphalangeal joint angle trajectory during flexion. The angles achieved through the new hybrid mechanism are compared with the conventional tendon-driven mechanism and the Root Mean Square Error (RMSE) values have been calculated by comparing to the anthropomorphic flexion angles of the published literature. The RMSE values calculated for three interphalangeal joints of the hybrid mechanism are found to be less than their counter-parts of the conventional tendon-driven mechanism. In addition to achieving resemblance to anthropomorphic flexion angles, the mechanism is designed within the anthropometric human finger dimensions.

This paper presents an upper limb exoskeleton that allows cognitive (through electromyography signals) and physical user interaction (through load cells sensors) for passive and active exercises that can activate neuroplasticity in the rehabilitation process of people who suffer from a neurological injury. For the exoskeleton to be easily accepted by patients who suffer from a neurological injury, we used the ISO9241-210:2010 as a methodology design process. As the first steps of the design process, design requirements were collected from previous usability tests and literature. Then, as a second step, a technological solution is proposed, and as a third step, the system was evaluated through performance and user testing. As part of the technological solution and to allow patient participation during the rehabilitation process, we have proposed a hybrid admittance control whose input is load cell or electromyography signals. The hybrid admittance control is intended for active therapy exercises, is easily implemented, and does not need musculoskeletal modeling to work. Furthermore, electromyography signals classification models and features were evaluated to identify the best settings for the cognitive human–robot interaction.

The Moth Flame Optimization (MFO) algorithm shows decent performance results compared to other meta-heuristic algorithms for tackling non-linear constrained global optimization problems. However, it still suffers from obtaining quality solution and slow convergence speed. On the other hand, the Butterfly Optimization Algorithm (BOA) is a comparatively new algorithm which is gaining its popularity due to its simplicity, but it also suffers from poor exploitation ability. In this study, a novel hybrid algorithm, h-MFOBOA, is introduced, which integrates BOA with the MFO algorithm to overcome the shortcomings of both the algorithms and at the same time inherit their advantages. For performance evaluation, the proposed h-MFOBOA algorithm is applied on 23 classical benchmark functions with varied complexity. The tested results of the proposed algorithm are compared with some well-known traditional meta-heuristic algorithms as well as MFO variants. Friedman rank test and Wilcoxon signed rank test are employed to measure the performance of the newly introduced algorithm statistically. The computational complexity has been measured. Moreover, the proposed algorithm has been applied to solve one constrained and one unconstrained real-life problems to examine its problem-solving capability of both type of problems. The comparison results of benchmark functions, statistical analysis, real-world problems confirm that the proposed h-MFOBOA algorithm provides superior results compared to the other conventional optimization algorithms.