Lower-limb exoskeletons can provide paraplegics with the ability to restore gait function. In the community ambulation, the user would frequently meet different floors, doorsills, and other obstacles. Therefore, parametric gait generation is a significant issue for this kind of exoskeletons. In this paper, a parametric gait online generation approach is proposed, which combines a parametric gait control method with a torque compensation control strategy, based on the state machine. In the torque compensation control, the reference tra-jectories of joint positions are obtained through compensating gravity, inertia, and friction, which is intent on the natural and well-directed source data. Based on the reference trajectories, the parametric gait control method is established, in which the gait can be controlled via three parameters: velocity, step-length, and step-height. Two test cases are performed on three healthy subjects. The results demonstrate that the parametric gait can be online generated smoothly and correctly, meanwhile every variable step can be triggered as users expect. The effectiveness and practicability of the gait generation approach proposed in this paper are validated. In addition, this research is the foundation of autonomous gait planning.

The hydrodynamic characteristics and body shape of catfish, Hypostomus, are used to design and develop an Autonomous Under-water Vehicle (AUV) named ZRAUV for subsea pipeline and cable inspection. Among the hydrodynamic characteristics, stability of this bio-inspired AUV, which may be adversely affected by disturbances such as marine currents during inspection process, is taken into consideration and evaluated both numerically and experimentally. Concerning numerical investigation, computational fluid dynamics based on Reynolds Averaged Navier-Stokes equations are applied to compute the hydrodynamic damping derivatives needed for stability analysis. In order to verify the numerical predictions, computations are also performed for the well-known submarine body with a typical axisymmetric hull shape, SUBOFF. Experiments are also carried out for both proposed AUV and a conventional axisymmetric one using self-propulsion tests. Measurements of turning rate in turning circle maneuver are in reasonably good agreement with those of numerical estimations and indicate that the turning rate of conventional bodies like SUBOFF is approximately 3.8 times as great as that of bio-inspired AUV. In other words, the findings reveal that in comparison with common axisymmetric bodies, the proposed AUV with biological hull shape is more stable by about 99%, thus, it is highly suitable for subsea pipeline and cable inspection.

There are many design parameters to determine a performance of a robot. Especially, in the case of the mobile robots, they require complicated motion at various environments to get high performances. In this sense, the analysis of the design parameters is the most important work to design an efficient mobile robot. In this study, we analyze the design parameters for the water-running robot. From the parametric study, we find some solutions to improve the performances of the robot. We derive dynamic equations for the water-running motion, and do a sensitivity analysis to understand the relationships between the parameters (frequency of the leg, stiffness of torsional springs that connects multi frames and mass of frames) and the performance of the water-running motion such as running speed and pitching stability. We use an orthogonal array to make various combinations of the parameters, and to reduce the number of a simulation process. As results, we summarize some solutions to improve the water-running motion. We are expecting that this study is going to be used to design robots that are operated on the water.

This paper proposes a metamorphic quadruped robot with a moveable trunk, called Origaker I. From the angle view of bionics, the robot can imitate the natural quadrupeds to twist its trunk. As we all know, most natural quadrupeds twist their trunk when running. The twisting trunk must bring significant benefits to their locomotion. Nevertheless there are few researches focusing on running gaits with twisting trunk of quadruped robots. Therefore, this paper investigates the trot gait with twisting trunk. One gait cycle of a lizard with twisting trunk is observed. Apart from the observation, the gait is designed based on the Zero Moment Point (ZMP) method and by con-sidering three points related to the twisting trunk. A simulation and an experiment are carried out to verify the efficiency of the trot gait with twisting trunk. It is found that the twisting trunk helps the quadruped robot get larger stride length and further perform higher lo-comotion speed than that with rigid trunk.

Weakly electric fish use the electric field to detect objects in the neighborhood or communicate with conspecifics. They generate electric field with their electric organ and the electroreceptors sense the distortion of electric field caused by nearby objects. They use a modulated frequency signal of the Electric Organ Discharge (EOD), and it can be disturbed by similar frequency signals that neighboring weakly electric fish emit. They have a particular behavior response to change their EOD frequencies to avoid signal jamming. It is called jamming avoidance response. Inspired by the behavior of wave-type weakly electric fish, we propose an engineering perspective of jamming avoidance response model with the amplitude-phase modulation graph. The time course of the amplitude-phase graph of the EOD signal provides a cue to detect the jamming signal. We argue that the temporal integration can determine the shift direction of the EOD as well as the amount of the frequency shift to be moved frequency for the jamming avoidance response. Alternatively, as a fast adapting measure, the cross product of point vectors in the amplitude-phase graph allows early decision for jamming avoidance. We demonstrate the methods with simulations and the real experiments in the underwater environment.

Honeybees are ectotherms that have the specific ability to control their body temperature to match environmental change. Honeybees, such as Apis mellifera L., can flex and extend their abdomen to transfer heat with the environment. Their folded intersegmental membranes, which are distributed in the segments of their abdomen, play key roles in heat transfer with abdominal movements. In this study, a temperature-controlled device was established to simulate varying ambient temperature and the abdominal behaviors of honeybee were investigated. Experimental results show that the folded intersegmental membranes make a considerable difference on the bees’ heat transfer ability. Bees can achieve temperature equilibrium by moving their abdomen, in this way bees increase convection to achieve temperature equilibrium. The higher the experimental temperature was, the faster the membrane moved and the shorter time required to reach heat balance. The function of folded intersegmental membranes on heat transfer was further elucidated by proposing a convective heat transfer model. The study on thermoregulation mechanism of honeybee abdomen helps explain its strong adaptability to the external environment as well as its defensive behavior against foreign invaders.

While sharkskin surface roughness in terms of denticle morphology has been hypothesized but remains yet controversial to be ca-pable of achieving turbulent flow control and drag reduction, sharkskin-inspired “riblets” have been reported to be an effective biomimetic design. Here we address an integrated study of biomimetic riblets inspired by sharkskin denticles by combining 3D digitizing and mod-eling of “fresh” denticles and computational fluid dynamic modeling of turbulent flows on a rough surface with staggered denticles and hound-tooth-patterned grooves. Realistic microstructures of denticles in five shark species of Galapagos, great white, whitetip reef, blacktip reef, and hammerhead sharks were first measured and digitized in three fold: (1) 2D imaging of lubricated sharkskin in a wet state by means of a “nano-suit” technique with a Field-Emission Scanning Electron Microscope (FE-SEM); (2) 3D structures of sharkskin denticles with a micro-focus X-ray CT; and (3) single denticles of the five shark species in a 3D manner with 3D-CAD. The denticles at mid-body location in the five species were observed to have a structure of five non-uniform-ridges (herein termed “non-uniform grooves”) with Angles Of Inclination (AOI) ranging over 20? – 32?. Hydrodynamics associated with the unique five-ridge denticles were then in-vestigated through modeling turbulent flow past a denticle-staggered skin surface. We further constructed a biomimetic riblet model inspired by the non-uniform grooves and investigated the hydrodynamic effects of height-to-spacing ratios of mid-ridge and side-ridges. Our results indicate that the morphological non-uniformity in sharkskin denticles likely plays a critical role in passively controlling local turbulent flow and point to the potential of denticle-inspired biomimetic riblets for turbulent-flow control in aquatic vehicles as well as other fluid machinery.

 

The present work reports microstructure-based wettability and reflectance responses of three varieties of Indian Rosaceae (Rosa) cultivars, viz. white rose (Rosa chinensis var spontanea), light pink rose (Rosa chinensis var minima) and dark pink rose (Rosa chinensis var minima). As for wettability, static and advancing and receding Contact Angles (CA) have been measured, for each type of matured rose petals. The surface roughness factors (r?), which are largely dependent on the micro-papillae assembly within the rose petal, are estimated to be, 2.74, 2.27 and 2.94 in case of White (W), Light Pink (LP) and Dark Pink (DP) petals; respectively. Moreover, the respective Contact Angle Hysteresis (CAH) values are measured as 51?, 27? and 59?. In order to exploit structural colouration through the reflectance char-acteristics, the specimens were dipped in three different media of different Refractive Indices (RI), viz. ethanol (RI = 1.36), propanol (RI = 1.39) and glycerine (RI = 1.47) for about 24 h. Upon ethanol and propanol adsorption, the LP and DP rose petals showed unusually similar reflectance patterns over a wide range of wavelengths, thus indicating a common microstructural share and structural colour contribution. The wetting-dewetting and structural colouration in natural systems, to a great extent, are dictated by the surface structure and solid-liquid and liquid-air interfaces, not only offer fundamental interest but also give scope for mimicking in artificial designs of technological interest.

 

Two kinds of typical superhydrophobic surfaces, ZnO nanorods and porous nano-SiO2 coating were successfully prepared on nickel alloy plates using a wet chemical method for the ZnO nanorods and spraying for the nano-SiO2 coating. Thermal stability of each of the superhydrophobic surfaces was tested. Scanning Electron Microscopy (SEM) and energy dispersive spectrometry were used to analyze microstructures and compositions. Although both superhydrophobic surfaces show similar wettability with respect to water, the SiO2 Nanoparticles Superhydrophobic Coatings (SiO2-NSCs) has better thermal stability than the ZnO Nanorods Superhydrophobic Coatings (ZnO-NSCs). The micro/nano structures of the two superhydrophobic surfaces can be destroyed during icing-melting cycles. In addition, at high temperature, the superhydrophobic properties of the surface can be destroyed because of the decomposition of fluorinated silane. The results can provide guidance for the practical cryogenic application of superhydrophobic surfaces.'''

Coir Fibres (CF) and Pineapple Leaf Fibres (PALF) are valuable natural fibres which are abundantly available in Malaysia as agri-cultural wastes. The aim of this study is to investigate the effects of alkali (6%), silane (2%), and calcium hydroxide (6%) on tensile, morphological, thermal, and structural properties of CF and PALF to improve their interfacial bonding with Polylactic Acid (PLA) matrix. Scanning electron microscopy and Fourier transform infrared spectroscopy were used to observe the effectiveness of the chemical treat-ments in the removal of impurities. Alkali treated fibres yield the lowest fibre diameter and the highest Interfacial Stress Strength (IFSS). Thermogravimetric Analysis (TGA) shows improved thermal stability in silane treated CF and alkali treated PALF. It is assumed that fibre treatments can help to develop biodegradable CF and PALF reinforced PLA biocomposites for industrial applications.

The resistance of Ionic Polymer Metal Composite (IPMC) electrodes plays an important role in the actuation performance of IPMC actuators. Owing to crack formation on the surface of platinum electrode, the surface resistance of the electrode increases, which greatly limits its actuating performance. In this paper, we proposed a new method of dynamic self-repair electrodes by ex-changing Cu2+ into the IPMC basement membrane. IPMC actuators with Cu2+ were prepared and the actuation performance in the air was subsequently measured. Compared with conventional IPMC actuators containing Li+ counter ions, those containing Cu2+ counter ions exhibited 2 times – 3 times larger displacement and 2 times –3 times bigger blocking force. In the morphology observation, we found that many small copper particles scattered in the middle of cracks after several bending cycles, which leads to an obvious decrease in electrode resistance. In the Cyclic Voltammetry (CV) scan measurement, we observed that the oxidation reaction of copper alternates with reduction reaction of copper ions with the change of voltage polarity, which was a dynamic process. Based on these analyses, it is concluded that the presence of Cu2+ can repair the damaged electrodes and induce lower electrode resistance, thus leading to the performance improvement of actuation.

The aim of this study was to analyze cartilage creep and creep recovery after static and cyclic loading. Up to now technical limitations have hindered the measurement of creep recovery. For this reason, we developed a closed loop micro creep and creep-recovery indentation test system with active force control. Bovine osteochondral explants were tested under static (110 kPa) and cyclic (100 cycles,
350 kPa/35 kPa, 1 Hz) loading conditions and subsequently creep recovery was measured. The cartilage thickness was determined using needle indentation. For static loading, the creep and creep-recovery rates were significantly different during the first 60 seconds (p < 0.05). Cyclic loading was assessed for the medial and lateral patella and resulted in a physiological patellar cartilage strain of 7.7% ± 2.6% and 8.2% ± 2.7%, respectively. We recorded a creep recovery of 97.8% ± 2.1% for the medial and 98.3% ± 2.4% for the lateral patella. The advantage of this study over earlier in vitro studies is that we recorded creep-recovery profiles with an actively controlled setup. This allowed us to analyze creep recovery immediately after removing the creep load, in contrast to MRI-based in vivo studies. In future, the presented method will enable us to quantify spatial variations within articular joints.

In this study, in order to prevent the failure of hemipelvic arthroplasty using a patient-specific Computer-Aided Design (CAD) and Additive Manufacturing (AM) approach, a new design for modular hemipelvic prosthesis was developed. Moreover, the biomechanical properties of the new design were determined. The 3D printed pelvic prosthesis with a sacrum portion that completely matches the back surface of the patient’s sacrum offers more potential for bone ingrowth between the host bone and prosthesis. The new approach integrated the capabilities of digital medical imaging techniques, CAD and metal AM to realize a modular hemipelvic prosthesis. The patient’s pelvic Digital Imaging and Communication in Medicine (DICOM) data were imported into Mimics software to construct a digital representative patient model for design of the prosthesis. A physical model was obtained using a Stereolithography (SLA) 3D printer for preoperative planning. The final customized implant was designed by using UG NX 10.0 software. Then a surgically modular hemipelvic prosthesis was fabricated from the Ti6Al4V titanium alloy by electron beam melting technology. The operation was performed according to the preoperative planning. The outcome of the operation was good at the 6-month follow-up. Also, the stress distribution and the relative micromotion revealed positive results based on a finite element model built to detect prosthesis stability. The 3D printed modular hemipelvic prosthesis provided good resolution for the failure of hemipelvic arthroplasty. Personal customization will be important in future surgeries aiming at improving the anatomy and function of the implant.

A new kind of renewable biocomposite was prepared by compounding bio-based poly(butylene succinate) (PBS) with teakwood sawdust which sieved sawdust were used as received or treated with 3-aminopropyltriethoxy silane (APS). The PBS/teakwood composites were compounded in the weight ratio of 90/10 wt%, 80/20 wt%, 70/30 wt% and 60/40 wt%. Thermal properties and morphology of the composites were investigated. The accelerated weathering testing was carried out for 60 h under water spraying and cycle of UV ex-posure at 60 ?C. Tensile and flexural properties before and after the accelerated weathering condition were analyzed. It was found that teakwood sawdust did not effect on the melting temperatures of PBS but reduced the degree of crystallinity. The composites showed lower thermal stability due to the degradation of hemicellulose and silane. Interfacial adhesion between PBS and APS-treated teakwood sawdust was achieved showing less pull-out of sawdust. Tensile and flexural modulus of composites increased with respect to sawdust content, in which the APS-treated composites had higher modulus. After passing the accelerated weathering condition, tensile modulus of the composites slightly increased while flexural properties decreased in the composites added sawdust content higher than 20 wt%. Loss of flexural properties was more pronounced than tensile properties due to the hydrolytic degradation introduced by hydrophilicity of lignocellulosic fillers.