Over a long period of time, arthropods evolve to have two excellent mechanical sensilla of slit sensilla and trichobothria sensilla, which construct a perfect perception system. The former mainly perceives the change of the in-the-plane force while the latter perceives that of the out-of-plane force. In recent years, these two sensilla have attracted researchers as the models for developing artificial mechanical sensors. This review mainly includes the biomechanics and biomimetic manufacturing techniques as well as their future application value. In order to better understand the advantages of biological strategies, this review describes the morphology, mechanical analysis, and information recognition of slit sensilla and trichobothria sensilla. Then this review highlights the recent development of Crack-based Sensors (CBSs) and Hair-like Sensors (HLSs) based on the analysis of biological mechanism. The manufacturing method and substrate of crack in CBS and those of hair rods in HLS are discussed respectively. Finally, the practical applications and potential value of two sensilla, such as flexible wearable electronic devices, robot sensing system, autopilot sensing and wind tunnel speed detection, are briefly discussed.

This study is aimed at exploring a technology that can use the human physiological information, such as Force Myography (FMG) signals to provide sensory feedback to prosthetic hand users. This is based on the principle that with the intent to move the prosthetic hand, the existing limbs in the arm recruit specific group of muscles. These muscles react with a change in the cross-sectional area; piezoelectric sensors placed on these muscles will generate a voltage (FMG signals), in response to the change in muscle volume. The correlation between the amplitude of the FMG signals and intensity of pressure on fingertips during grasping is then computed and a dynamic relation (model) is established through system identification in MATLAB. The estimated models generated a fitting accuracy of more than 80%. The model is then programmed into the Arduino microcontroller, so that a real-time and proportional force feedback is channeled to amputees through a micro actuator. Obtaining such percentages of accuracy in sensory feedback without relying on touch sensors on the prosthetic hand that could be affected by mechanical wear and other interaction factors is promising. Applying advanced signal processing and classification techniques may also refine the findings to better capture and correlate the force variations with the sensory feedback.

To perform flow-related behaviors in darkness, blind cavefish have evolved Lateral Line Systems (LLSs) with constriction canals to enhance hydrodynamic sensing capabilities. Mimicking the design principles, we developed a Canal-type Artificial Lateral Line (CALL) device featuring a biomimetic constriction canal. The hydrodynamic characterization results revealed that the sensitivity of the canal LLS increases with the decrease in the width (from 1 mm to 0.6 mm) and length (from 3 mm to 1 mm) of the constriction canal, which is in accordance with the modeling results of canal mechanics. The CALL device was characterized in Kármán vortex streets generated by a cylinder in a laminar flow. The CALL device was able to identify the diameter of the cylinder, with a mean identification error of approximately 2.5%. It also demonstrated the identification ability of wake width using the CALL device, indicating the potential for application in hydrodynamic perception.

To enable the capacity of climbing robots to work on steep surfaces, especially on inverted surfaces, is a fundamental but challenging task. This capacity can extend the reachable workspace and applications of climbing robots. A track-type inverted climbing robot called SpinyCrawler was developed in this paper. Using a spiny track with an opposed gripping mechanism, the robot was experimentally demonstrated to have the ability of generating considerable adhesion to achieve stable inverted climbing. First, to guarantee reliable attachment of the robot on rough ceilings, a spiny gripper inspired by the opposed gripping prolegs of caterpillars is designed, and a gripping model of the interaction between spines and the ceiling asperities is established and analyzed. Second, a spiny track is developed by assembling dozens of spiny grippers to enable continuous attachment. A cam mechanism is introduced in the robot design without extra actuators to achieve stable attachment and easy detachment during continuous climbing. Finally, climbing experiments are conducted on different surfaces, using a SpinyCrawler prototype. Experimental results demonstrated stable climbing ability on various rough inverted and vertical surfaces, including concrete walls, crushed stone walls, sandpaper walls, brick walls, and brick ceilings.

This article proposes a novel pneumatic soft actuator, which can perform bending in different directions under positive or negative air pressure. The actuators are composed of multiple airbags, and the design of the airbags is analyzed. A pneumatic soft robot based on these soft actuators is designed and fabricated by 3D printing technology. This robot consists of three soft multi-bladder actuators, one soft sensor, middle layer, bottom layer, front barb, front feet and rear feet. According to the different positive or negative pressure control of the three soft multi-bladder actuators, the robot can perform both linear, crossing and climbing movements. The soft robot has excellent environmental adaptability and can pass through complex environments by combining three modes of motion. Then, we establish the closed-loop automatic control system using soft sensor. The soft sensor can be stretched and compressed as the soft robot’s movement. Finally, the automatic control system is verified by linear, crossing and climbing movement experiments. Results indicate that the robot can pass through complex en-vironments under the closed-loop control system.

One of the major respects of the autonomous capability of underwater robots in unknown environment is to be capable of global path planning and obstacles avoiding when encountering abrupt events. For the Spherical Underwater Robot (SUR) to fulfill autonomous task execution, this paper proposed a novel fuzzy control method that incorporates multi-sensor technology to guide underwater robots in unknown environment. To attain the objective, a SUR we designed is used to design the controller. According to its kinematic model, the safety distance was calculated and sensors (US1000-21A) were arranged. The novel fuzzy control method was then explored for robot’s path planning in an unknown environment through simulation. The simulation results demonstrate the capability of the proposed method to guide the robot, and to generate a safe and smooth trajectory in an unknown environment. The effectiveness of the proposed method was further verified through experiments with a SUR in a real platform. The real environment experiments by using the novel fuzzy control method were compared with the basic control method. The experimental results show that in unknown environments, the proposed method improves the execution efficiency and flexibility of the SUR.

We proposed and developed a small bionic amphibious spherical robot system for tasks such as coastal environment monitoring and offshore autonomous search and rescue. Our third-generation bionic small amphibious spherical robots have many disadvantages, such as the lack of maneuverability and a small operating range. It is difficult to accomplish underwater autonomous motion control with these robots. Therefore, we proposed a fourth-generation amphibious spherical robot. However, the amphibious spherical robot developed in this project has a small and compact design, with limited sensors and external sensing options. This means that the robot has weak external information collection capabilities. We need to make the real time operation of the robot’s underwater motion control system more reliable. In this paper, we mainly used a fuzzy Proportional-Integral-Derivative (PID) control algorithm to design an underwater motion control system for a novel robot. Moreover, we compared PID with fuzzy PID control methods by carrying out experiments on heading and turning bow motions to verify that the fuzzy PID is more robust and exhibits good dynamic performance. We also carried out experiments on the three-dimensional (3D) motion control to validate the design of the underwater motion control system.

In this paper, we studied the acceleration behavior of a quadruped animal during a galloping motion. Because the development of many quadruped robotic systems has been focused on dynamic movements, it is obvious that guidance from the dynamic behavior of quadruped animals is needed for robotics engineers. To fulfill this demand, this paper deals with analysis of the galloping motions of a domestic cat, which is well known for its excellent acceleration performance among four-legged animals. Based on the planar motion capture environment, the movement data of a galloping feline was acquired and the dynamic motions were estimated using a spring-mass system. In particular, the effects of the position and angle of the center-of-mass of the cat, angular displacement of the spine, and angular velocity of the spine were analyzed and are discussed below. Through this process, it was possible to understand the dynamic movement characteristics of the cat, and to understand the relationships between, and the influences of, these parameters. From this analysis, we provide significant data applicable to the design of joint movements in quadruped robot systems.

The aerodynamic characteristics of a normal hovering foil with Synthetic Jet (SJ) actuation are numerically studied in this work. An elliptic foil with ratio of 4 undergoes the imposed translation and rotation synchronously. A pair of SJs with the same frequency and strength is placed on the upper and lower surfaces of the foil. Thus, the local flow field around the foil would be influenced. At the Reynolds number of 100 and the rotating axis position of half chord, the effects of the inclined angle between the jet direction and the chord line, the phase angle between the SJs and the translation as well as the SJ location on the aerodynamic characteristics are systematically examined. Compared with the oscillating foil without SJ actuation, it is illustrated that the enhancement of mean lift force and hovering efficiency can be obtained by using the SJs with suitable working parameters. Based on the numerical analysis, it is found that the jet flow on the foil surfaces, which changes the local pressure distribution, can benefit the aerodynamic performance of the hovering foil.

Similarities and differences of a large-scale flapping-wing robot with fixed-wing UAVs in equations of motion, trim curves, and aerodynamic forces in forward flight are discussed in this paper and a simplified model for flapping flight is presented. Due to the high Wing to Total Weight (WTW) ratio of large-scale ornithopters, simple rigid body dynamics is not accurate enough for flight dynamics modeling. On the other hand, the multi-body dynamics associated with flapping gives little insight into the behavior of the resulting model due to complexity of equations. It is also difficult to design proper controllers for such complicated models. In this paper, the effects of different terms of multi-body equations of ornithopter on the estimated aerodynamic forces are studied via experimental flight data. A simpler but yet accurate set of equations is obtained by removing less effective terms from original relations. The presented model is in the form of normal aircraft equations plus some additional terms which can be used in different control and estimation processes. In addition, trim conditions of forward flight are extracted using several flight tests, and corresponding periodic behavior of states and forces are studied. These studies are applicable for identifying time-periodic models.

Gradient wettability is important for some living organisms. Herein, the dynamic responses of water droplets impacting on the surfaces of four regions along the wing vein of cicada Cryptotympana atrata fabricius are investigated. It is revealed that a gradient wetting behavior from hydrophilicity (the Wenzel state) to hydrophobicity and further to superhydrophobicity (the Cassie-Baxter state) appears from the foot to apex of the wing. Water droplets impacting on the hydrophilic region of the wing cannot rebound, whereas those impacting on the hydrophobic region can retract and completely rebound. The hydrophobic region exhibits robust water-repelling performance during the dynamic droplet impact. Moreover, a droplet sitting on the hydrophobic region can recover its spherical shape after squeezed to a water film as thin as 0.45 mm, and lossless droplet transportation can be achieved at the region. Based on the geometric parameters of the nanopillars at the hydrophilic and hydrophobic regions on the cicada wing, two wetting models are developed for elucidating the mechanism for the gradient wetting behavior. This work directs the design and fabrication of surfaces with gradient wetting behavior by mimicking the nanopillars on cicada wing surface.

In this paper, we fabricate a biomimetic superhydrophobic coating on an X90 pipeline steel substrate by electrodeposition of copper, hydrothermal treatment to form a copper oxide layer, and subsequent surface modification with Stearic Acid (SA). The coating exhibits static contact angles of water of 160? ± 3.1? in the air and 170.7? ± 2.5? in cyclopentane, indicating the strongly water-repelling nature of the coating. The morphologies of the cyclopentane hydrate formed on steel substrates with and without the superhydrophobic coating are investigated. The results show that the hydrate particle on the coating exhibits spherical morphology and herein the interfacial contact area and adhesion force to the solid surface can be essentially reduced. The adhesion force reduction may be resulted by the decrease in the contact area between the hydrate and the solid surface.

In this work, a biomimetic coating of hydroxyapatite (HA)-and titania (TiO2) was deposited on low elastic β-phase Ti-35Nb-7Ta-5Zr (β-TNTZ) alloy by plasma spray deposition technique for orthopedic applications. The effect of TiO2 reinforcement on microstructure, mechanical properties, and bioactivity was investigated. The morphology, coating thickness, elemental composition, and phase composition of the developed coatings were characterized. The biomechanical behavior of the deposited coatings was investigated in terms of surface hardness, elastic modulus, and adhesion strength. It was found from the morphological investigation that the TiO2 reinforcement improves the microstructure and prevents the formation of defects in the coating. The biomimetic HA-TiO2 coated surface possessed pores, size ranging from 200 nm – 600 nm that benefits the apatite growth and osseointegration. The EDS spectrum, mapping, and XRD analysis show that the deposited layer β-TCP, CaO, TTCP, TiO2 phases. The HA-TiO2 coating exhibits a very dense and thick layer of 100 μm – 125 μm that exhibits excellent adhesion strength to offer mechanical interlocking to prevent delamination. The alloying of TiO2 improves the hardness from 1.67 GPa to 2.95 GPa that enhances the wear resistance. It was found that HA-TiO2 coating exhibits better hydrophilic and biocompatible surface as compared to HA-coating.

Risky gait activities lead to severe wear in orthopaedic implants during postoperative periods. The aim of the present study is to predict the linear and volumetric wear of zirconia (ZrO2) vs alumina (Al2O3) hip implants subject to risky and normal gait activities. Initially, the gait loads pertaining to risky gait activities were converted to equivalent normal loads. Then using the computed normal loads, friction and wear coefficients of ZrO2 ball against Al2O3 disc were calculated from Pin-on-Disc (POD) tribometer under dry and lubricating conditions. Saline solution, a bio-lubricant was utilized for lubrication purpose to mimic synovial fluid properties. Nineteen gait activities stair ascending or descending, carrying load, lifting load and ladder up or down etc., grouped as A, B, C and D were used  to determine friction and wear coefficients. Finite Element Method (FEM) was employed to predict the wear of the bearing couple. The developed contact pressure for these gait activities was then utilized to compute linear and volumetric wear for 2 million cycles. Our findings suggests that, patients regularly involved in group C and D type gait activities were likely to cause more wear which may accelerate early implant failure.

This paper describes the bioinspiration process to derive design concepts for new deep foundation systems that have greater axial capacity per unit volume of pile material compared to conventional deep foundations. The study led to bioinspired ideas that provide greater load capacity by increasing the pile shaft resistance. The bioinspiration approach used problem-solving strategies to define the problem and transfer strategies from biology to geotechnical engineering. The bioinspiration considered the load transfer mechanism of hydroskeletons and the anchorage of the earthworm, razor clam, kelp, and lateral roots of plants. The biostrategies that were transferred to the engineering domain included a flexible but incompressible core, passive behaviour against external loading, a longitudinally split shell that allows expansion for anchorage, and lateral root-type or setae-type anchoring elements. The concepts of three bioinspired deep foundation systems were proposed and described. The advantage of this approach was illustrated with two examples of the new laterally expansive pile in drained sand under axial compression. The finite element analysis of these examples showed that the new laterally expansive pile can provide considerably greater load capacity compared to a conventional cylindrical pile due to the increased lateral confining pressure developed along the expanded pile core. 

This paper simulates the cuckoo incubation process and flight path to optimize the Wavelet Neural Network (WNN) model, and proposes a parking prediction algorithm based on WNN and improved Cuckoo Search (CS) algorithm. First, the initialization parameters are provided to optimize the WNN using the improved CS. The traditional CS algorithm adopts the strategy of overall update and evaluation, but does not consider its own information, so the convergence speed is very slow. The proposed algorithm employs the evaluation strategy of group update, which not only retains the advantage of fast convergence of the dimension-by-dimension update evaluation strategy, but also increases the mutual relationship between the nests and reduces the overall running time. Then, we use the WNN model to predict parking information. The proposed algorithm is compared with six different heuristic algorithms in five experiments. The experimental results show that the proposed algorithm is superior to other algorithms in terms of running time and accuracy.