Flexible Inorganic Piezoelectric Acoustic Nanosensors for Biomimetic Artificial Hair Cells

For patients who suffer from sensorineural hearing loss by damaged or loss of hair cells in the cochlea, biomimetic artificial cochleas to remedy the dis­advantages of existing implant systems have been intensively studied. Here, a new concept of an inorganic‐based piezoelectric acoustic nanosensor (iPANS) for the purpose of a biomimetic artificial hair cell to mimic the functions of the original human hair cells is introduced. A trapezoidal silicone‐based membrane (SM) mimics the function of the natural basilar membrane for frequency selectivity, and a flexible iPANS is fabricated on the SM utilizing a laser lift‐off technology to overcome the brittle characteristics of inorganic piezoelectric materials. The vibration amplitude vs piezoelectric sensing signals are theoretically examined based on the experimental conditions by finite element analysis. The SM is successful at separating the audible frequency range of incoming sound, vibrating distinctively according to varying locations of different sound frequencies, thus allowing iPANS to convert tiny vibration displacement of ≈15 nm into an electrical sensing output of ≈55 μV, which is close to the simulation results presented. This conceptual iPANS of flexible inorganic piezoelectric materials sheds light on the new fields of nature‐inspired biomimetic systems using inherently high piezoelectric charge constants.     

Detection of in-plane fiber waviness in cross-ply CFRP laminates using layer selectable eddy current method

This paper presents an eddy current testing method to detect in-plane fiber waviness in cross-ply carbon fiber reinforced plastic (CFRP) laminates. We propose a method which has high sensitivity to presence of in-plane waviness and can select layers to be inspected. The probe was used to detect artificially induced in-plane waviness in cross-ply CFRP laminates. It was observed that obtained signal has extreme value at the edges and vertex of the waviness, which implies the possibility of precise identification of waviness location. Detectability of subsurface waviness was investigated using 20 layer cross-ply laminate with in-plane waviness at different depths. Experimental results showed that in-plane waviness 18 layers away from the surface could be detected. The minimum misalignment angle of the detected waviness was 7.4°. The effectiveness of the probe and physical background of the obtained signals were verified by finite element method analyses.     

Strain gauge based sensing hydraulic fixtures

Clamping errors in workpiece positioning decrease the outcome of machine tools. To avoid rejects, which occur due to failures in the clamping, a sensory clamping system is being investigated at the Institute of Production Engineering and Machine Tools (IFW). The aim is to provide hydraulic clamping elements with sensory capabilities to enable condition and process monitoring of the clamping system inside the harsh environment of a machine tool.Firstly, this paper gives a general survey of the targeted application and the concept to achieve a sensory clamping system for the industrial use in series production. Then it focuses on the integration of strain gauges into the exemplary chosen hydraulic swing clamp. Hereby, it shows the qualification of strain gauges for the estimation of different objectives, like hydraulic pressure, piston position, and external loads. Therefore, methods for the identification of suitable positions for the strain gauge integration into the clamping element are being discussed on the basis of experimental results and simulations. Furthermore, a method to achieve higher sensor sensitivity by 71% to the detriment of the compliance by 1.3% is presented.     

Experimental study on tensile property of AZ31B magnesium alloy at different high strain rates and temperatures

As the lightest metal material, magnesium alloy is widely used in the automobile and aviation industries. Due to the crashing of the automobile is a process of complicated and highly nonlinear deformation. The material deformation behavior has changed significantly compared with quasi-static, so the deformation characteristic of magnesium alloy material under the high strain rate has great significance in the automobile industry. In this paper, the tensile deformation behavior of AZ31B magnesium alloy is studied over a large range of the strain rates, from 700 s⁻¹ to 3 × 10³ s⁻¹ and at different temperatures from 20 to 250 °C through a Split-Hopkinson Tensile Bar (SHTB) with heating equipment. Compared with the quasi-static tension, the tensile strength and fracture elongation under high strain rates is larger at room temperature, but when at the high strain rates, fracture elongation reduces with the increasing of the strain rate at room temperature, the adiabatic temperature rising can enhance the material plasticity. The morphology of fracture surfaces over wide range of strain rates and temperatures are observed by Scanning Electron Microscopy (SEM). The fracture appearance analysis indicates that the fracture pattern of AZ31B in the quasi-static tensile tests at room temperature is mainly quasi-cleavage pattern. However, the fracture morphology of AZ31B under high strain rates and high temperatures is mainly composed of the dimple pattern, which indicates ductile fracture pattern. The fracture mode is a transition from quasi-cleavage fracture to ductile fracture with the increasing of temperature, the reason for this phenomenon might be the softening effect under the high strain rates.     

Performance study on a novel variable area robotic fin

Fish fin possesses large deformations in its motion cycle assisting fish's swimming, in which its geometric parameters such as surface area, aspect ratio change greatly, and the complex deformations and motions result in complicated hydrodynamic response. In this paper, the dynamic change of surface area is concentrated to improve the propulsion performance of underwater propeller. A novel variable area robotic fin is developed and the effect of surface area change on the hydrodynamic forces is investigated quantitatively. The robotic fin composes two parts: a base fin with hand shaped holes and a cover fin that fits the shape of the holes. The change of the surface area of the robotic fin is realized by rotating the cover fin to shield the holes in the base fin. A crank-rocker-cam composite mechanism is designed to realize the fin pitching motion and surface change motion synchronously with one driving motor. Four control modes of surface area change in a motion circle are investigated, namely, complete traditional invariable fin, traditional invariable fin with smaller surface, fin with larger surface during in-strokes and fin with larger surface during out-strokes. The thrust force and efficiency of the four control modes with various swimming speeds are detailed experimented and discussed. It is found that the variable area fin achieves a remarkable different hydrodynamic response and the corresponding control modes affect much. For the variable surface area fin, they generate average thrust force between the complete invariable fin and invariable fin with smaller surface, in which the fin with larger surface area during in-strokes follows closely the complete traditional invariable fin, while the fin with larger surface area during out-strokes performs more like the traditional invariable fin with smaller surface. It is interesting that fin with larger surface during in-strokes can generate much larger average thrust force than the fin with large surface during out-strokes. For the efficiency, the fin with larger surface during in-strokes behaves the best. And the effect of the surface area change ratio and time is closely connected with the control modes. Besides, the influences of pitching frequency and amplitude are also studied. The results demonstrate that the propulsive performance can be indeed improved by proper surface area change in a motion cycle, which will be an inspiration to the design of novel underwater robot propulsive system.     

A single visual-servo controller of mobile robots with super-twisting control

This paper presents a novel approach for image-based visual servoing, extending the existing works that use the trifocal tensor (TT) as source for image measurements. In the proposed approach, singularities typically encountered in this kind of methods are avoided. A formulation of the TT-based control problem with a virtual target resulting from the vertical translation of the real target allows us to design a single controller, able to regulate the robot pose towards the desired configuration, without local minima. In this context, we introduce a super-twisting control scheme guaranteeing continuous control inputs, while exhibiting strong robustness properties. Our approach is valid for perspective cameras as well as catadioptric systems obeying the central camera model. All these contributions are supported by convincing numerical simulations and experiments under a popular dynamic robot simulator.     

Transient response of a driver-pickup coil probe in transient eddy current testing

Novel solutions that correctly incorporate all electromagnetic interactions arising in inductively coupled circuits are presented for the case of a coaxial driver and pickup coil probe encircling a long ferromagnetic conducting rod. The differential circuit equations are formulated in terms of the rod׳s impulse response using convolution theory, and solved by Fourier transform. The solutions presented here are the first to account for feedback between a ferromagnetic conductor and the driver and pickup coils, providing correct voltage response of the coils. Experimental results, obtained for the case of square wave excitation, are in excellent agreement with the analytical equations.     

Design of direct solar PV driven air conditioner

Solar air conditioning system directly driven by stand-alone solar PV is studied. The air conditioning system will suffer from loss of power if the solar PV power generation is not high enough. It requires a proper system design to match the power consumption of air conditioning system with a proper PV size. Six solar air conditioners with different sizes of PV panel and air conditioners were built and tested outdoors to experimentally investigate the running probabilities of air conditioning at various solar irradiations. It is shown that the instantaneous operation probability (OPB) and the runtime fraction (R_F) of the air conditioner are mainly affected by the design parameter r_pL (ratio of maximum PV power to load power). The measured OPB is found to be greater than 0.98 at instantaneous solar irradiation I_T > 600 W m⁻² if r_pL > 1.71. R_F approaches 1.0 (the air conditioner is run in 100% with solar power) at daily-total solar radiation higher than 13 MJ m⁻² day⁻¹, if r_pL > 3.     

Studies on the impact of energy quality on human development index

Bio-mass is one of the most dependable energy resources in the rural areas of the developing world. The energy quality and emission intensity of bio-mass is varying from species to species and also on the processing techniques. As the effective energy output and emission intensity have direct influences on health, education and income generation, these become the major input for human development index (HDI). Long term field studies were conducted in a couple of rural areas of different geographical locations to quantify the impact of the energy quality on the HDI value. Results of such studies indicated that geographical locations and the available infrastructure therein have distinct role in providing access to superior resources. Further studies indicated that switching over from kerosene lamp to solar photovoltaic (PV) lighting systems and plugging into charcoal fuel from raw bio-mass have opened up multiple avenues of opportunities and development for the villagers. Adaptability of these resources made significant positive contributions on ecology, economy, and empowerment. It was further found that the use of locally available good quality energy resources enhanced the HDI value by more than 16–18% from its initial figure.     

Three-dimensional experiment and numerical simulation of the discharge performance of sluice passageway for tidal power plant

In this study, the discharge performance of the sluice passageway of tidal power plants was investigated based on the experiments conducted in a planar open channel and three-dimensional numerical simulations. By conducting the experiments in a planar channel, it was possible to reproduce the three-dimensional flow field around the sluice passageways similar to the field condition. The discharge capability of the passageway was estimated under various flow conditions with five different channel bathymetries. The estimates of the discharge coefficient generally ranged from 1.3 to 1.45, which are significantly smaller than the values obtained from the previous study based on the two-dimensional experiment. In addition, the experimental results showed a considerable difference in the discharge coefficient among the test cases, demonstrating an apparent influence of channel bed topography on the discharge performance. Based on an intensive parametric study carried out using the numerical simulations, an optimal configuration of the width, slope, and bottom length of the apron section was suggested for maximizing the discharge capability of the sluice passageway.