Sensor nodes are innovative devices that can perform measurements on a large scale and communicate over a network. One of the most significant problems regarding the sensor nodes is how to supply power to a large number of devices. For this reason, they greatly benefit from energy harvesting techniques which can provide energy recovered directly from the environment. A study of the design and the modeling of an autonomous sensor node, powered by a vibrational piezoelectric harvester, is reported here. Subject of the first part of the analysis is a piezoelectric bimorph: an analytical model is proposed in order to estimate the performance, giving particular attention to the optimal mechanical and electrical parameters. The model is then validated through experimental tests, assuming different kinds of real scenarios. Then the results are used to design a device that can benefit from this harvester. In particular a wireless sensor node is developed, for which the energy scavenging ensures energy autonomy and long-term operability. Thanks to a particular harvesting circuit and opportune algorithms for energy management, this system is able to extract energy from vibrations and store it into capacitors. The embedded accelerometer and a wireless module make this device ideal for Structure Health Monitoring purposes.

A complex system is composed of many interacting components, but the behavior of the system as a whole can be quite different from that of the individual components. An automobile is an example of a common mechanical system composed of a large number of individual components that are mechanically connected in some way and hence transmit vibrations to each other. This paper proposes a variety of inter-related analytical tools for the study of experimental data from such systems. In this work, experimental results of accelerometer data acquired at two locations in the automobile for two different kinds of tests are analyzed. One test is the response to impact on a stationary vehicle, and the other is the road-response to the vehicle being driven on a flat road at different speeds. Signals were processed via Fourier and wavelet transforms, cross-correlation coefficients were computed, and Hilbert transforms and Kuramoto order parameters were determined. A new parameter representing synchronization deficit is introduced. There is indeed some degree of synchronization that can be quantified between the accelerations measured at these two locations in the vehicle.

Flexible-link robots are an important class of manipulators which uses lightweight arms for assembly, civil infrastructure, bridge/vehicle systems and large-scale space structures. The wide spread of these systems in various application areas has ensured that the modeling of flexible elements and the control of vibration have received a great deal of attention in recent years. In this work it is analyzed a two DOF parallel robot with two flexible links used for pick and place operations, developing a control strategy based on piezoelectric actuators and strain gauges or accelerometers embedded in the links. The analysis of the robot behaviour and the development of the controller, have been carried out on an electromechanical model built in Matlab ® and co-simulated with the multibody flexible model built in Adams ® . Results show positive confirmation of the study and encourage future tests on the real manipulator to validate the multibody model and the control strategy.

This paper presents the method estimating the contribution of vibration sources in gasoline engine with a multiple input system. Multi Dimensional Spectral Analysis (MDSA) has used to identify the cause of a linear dependence indicated by an ordinary coherence function. In order to apply the MDSA to the vibration source identification in gasoline engine, the virtual model of two inputs and single output system is simulated. For the validation of this model, the vibration of alternator was measured by using tri-axial accelerometers attached on the selected vibration source. After calculating the coherence analysis between each source based on the virtual model, the vibration contribution of alternator is calculated.

Electronic gloves are one of the most common methods used as human hand input devices. They proved to be useful in various applications such virtual reality, sign language interpretation and robotic systems. However, many of these electronic gloves tend to be either economically or computationally expensive. In contrast, this article discusses the development of a data glove that is practical and cost efficient with wireless control capabilities. It is based on placing tri-axial tilt accelerometers on the glove to map the movement of human fingers. All data acquired from the glove is transmitted wirelessly via Bluetooth connection to a computer where it can be used for various applications. The glove was used to control a five-motor tendon driven robotic hand. Tests were carried out to correlate tilt angles acquired from the glove with the appropriate motor values that will move the robotic fingers to the same position as that of the glove fingers. As a result, the robotic hand was able to mimic each human hand finger and thereby perform sign and grasp movements.

In this paper, a nonlinear complementary filter is presented to estimate the attitude of a Vertical Take Off and Landing Unmanned Aerial Vehicle (VTOL UAV). The measurements are taken from a low-cost IMU (Inertial Measurement Unit) which consists of 3-axis accelerometers, 3-axis gyroscopes and 3-axis magnetometers. From the proposed estimators, the full orientation matrix R will be retrieved. The proposed observers will estimate the instantaneous quaternions as well as the gyroscope bias. This representation of orientation by the rotation matrix and quaternions allows overcoming the problem of singularities that appear in local parametrization such as Euler angles. Therefore, both estimators may be used to describe any kind of 3-D motion. Convergence of the two observers is theoretically proved and simulations are conducted taking data from a real platform in hovering flight conditions.

The object of the present study is to design a micro switch witch activates the airbag of a car when the amplitude of the acceleration of the accident exceeds the critical one. The response time of the micro switch is supposed to be 5 ms. Micro switch consist of a proof mass connected to a clamped-clamped micro beam. The nonlinear partial integro-differential equation of the motion is solved using FEM. According to the results it is recommended to use micro switches instead of accelerometers as airbag activators in car’s safety systems.

Rotating machines are one of the most wide spread items of equimpnet in the industrial plants; hence the reliable operation is of great practical importance. Analyses show that when a run-to-failure philosophy is adopted in rotating machinery maintenance, their downtime is usually three to four times longer comparing to a periodic or proactive maintenance approach. A successful proactive maintenance program requires an integration of several diagnostic procedures into an intelligent data processing system. Such a system allows detection of a broad range of faults in an early stage. The main aim of this paper is to present current results of our development of an intelligent rotating machinery diagnostics program for detecting a broad range of faults from signals which can be measured non-destructively and on-line. The main motivation is to develop computationally efficient algorithm that can be implemented on a standard (low-cost) platform. In that respect we have developed a test rotating machine equipped with accelerometers, temperature sensors and sensors for lubricating oil characterization. In this paper we focus on gear-box faults and a feature extraction procedure based on non-parametric statistical concepts as suggested and demonstrated on experimental data.

In this study, a novel thermal-bubble-based micromachined accelerometer with advantages of no proof mass, preferable frequency response, and high sensitivity is presented. Unlike the other techniques, the only moving element in the proposed device is a small thermal-bubble created by using a high flux heater to vaporize the liquid contained in the micro chamber. In order to improve the performance of the accelerometer, the basic physical characteristics of this sensor have been analyzed. Numerical simulations are conducted to study the heat transfer and fluid flow behavior of the device and to demonstrate the feasibility of our design. The temperature profile and the velocity field distribution under different applied acceleration have been acquired. Moreover, a method for manufacturing the accelerometer by using the techniques of micromachining is provided and the performance of the presented design has been examined. The results concluded that the proposed design has better response and sensitivity comparing to its counterparts.

The experimental and practical evaluation methods and results for vibration sensor are described in this paper. Because the vibration sensor accelerometer has the feature of low-noise electronics, the testing is performed in the basement of National Measurement Laboratory (NML), in which environmental vibration amplitude is less than 3μm/sec. First we put the sensor on a spring isolator plate with 3 Hz natural frequency and a big concrete mass with 29 Hz peak value to get the high and low frequency noise level separately. Next we mount two same-type sensors back-to-back horizontally. The output signals of the two sensors are out of phase, so we can calculate their noise level easily. Finally we use an air-bearing shaker to generate a low frequency and low amplitude vibration to verify the sensor measurement ability. The noise level of the sensor can be determined by using the practical method and an out of phase technique.

A large number of people are exposed to whole body vibration in their occupational life. Measuring vibration is an important tool in rehabilitation and biomechanical fields of research. We have proposed image processing as a new method to record and determine the frequency response of human body. The arranged set up for forced vibration consisted of an AC motor, a variable speed drive unit and a shaking table for producing one directional sinusoidal vibration. Volunteers were asked to stand on the shaking table at a relaxed posture. Two digital camcorders were used to capture the motion of colored pencil-dot markers on the skin of human body (forehead) and on the edge of the shaking table. After color spotting each frame, the binary image results were processed using new circle factor criteria proposed in this work, for fast finding circles based on second order statistics. The extracted points were calibrated using our own extended version of the direct linear transformation (DLT) method. Subsequently Vibration measuring software has been completely developed in Borland Delphi 5.0 . Finally obtained displacement function of the body and the shaking table has been used in conjunction with Matlab 6.5 to prepare a proper algorithm for analyzing human body vibration. We discussed mechanical characteristics of the body by obtaining mechanical impedance and transmissibility from the shaking table to the head as example applications of the conducted software . The important point is the fact that all devices used in our developed measurement system are usually available in a biomechanics laboratory where a Gait system is functioning. This gives the opportunity for such laboratory to add vibration measurement to its capabilities without much excessive costs. The system has the advantage of lower noise sensitivity in comparison to accelerometer. The main advantage of this method is working with a simple user-familiar hardware with no external device attached to the subject and also a user-friendly-software.

Impulse-momentum methods of analysis developed for rigid body impacts are applied in this paper to predict forces acting in a simplified spacecraft model during a touchdown impact. This paper presents both analytic and experimental effort for a complex, multi-body impacting system that include friction and deformable elements. Specifically, we analyze a vertically moving guided mass representing a landing spacecraft to which is attached a telescopic, energy-absorbing leg. The landing gear, which is used in our study, employs crushable material in the leg, strut, and foot plus surface friction to absorb the landing shock. The experimental setup consists of simplified landing system, and accelerometers for the dynamic measurement. Acceleration data collected via data acquisition system is converted to the crushing, normal and tangential velocities. The results showed good agreement between the analysis and experiment for the first phase of motion. The derivation of limiting condition equations for all possible alternatives for the second phase is incomplete. We conclude that the challenges of deriving and testing for all motion phase ending events make the impulse-momentum method inferior to straight-forward dynamic simulation as a design tool.

Colossal magnetoresistance (CMR), as the name implies, is the phenomenon of dramatic changes in resistance attendant upon application of a magnetic field. The typical CMR material is derived from perovskite manganites with the chemical formula Ln 1−x A x MnO 3 , where Ln is the rare earth (Ln = La, Pr, Nd, Sm) and A is the divalent metal (A = Ca, Ba, Sr). The objective of this paper is to study the effects of the doping Nd and Pr at La site on La-Ba-Mn-O ceramics using solid state reaction. The characteristics and magnetotransport properties of CMR materials are investigated. Polycrystalline (La 1−x Pr x ) 0.67 Ba 0.33 MnO 3 (x = 0, 1/6, 1/3, 1/2, 2/3, 5/6, 1) and (La 1−x Pr x ) 0.67 Ba 0.33 MnO 3 (x = 0, 1/6, 1/3, 1/2, 2/3, 5/6, 1), are doped with Pr and Nd site based manganites, calcined at 900°C for 12 hours, pelletized and sintered at 1300°C for 24 hours have been synthesized and investigated. The magnetoresistance (MR) effects are measured using the four point probe technique. The magnetoresistance defined as MR% = (R o −R H )/R H × 100 was measured at a magnetic field of H ≤ 1T at room temperature. The MR values were increased from 7.9–12.7% and from 7.9–12.3% for doping with Nd (x = 0.17) and Pr (x = 0.33) respectively. The electrical property, T p was determined by using standard four-point probe resistivity measurement in a temperature range of 20 K to 300 K. The result shows that Pr and Nd dopants shift the value of T P to a lower temperature. In this paper the structural pattern and microstructure property of bulk samples have been investigated via XRD, AFM and SEM. XRD patterns show that these systems are in single-phase with orthorhombic distorted perovskite structures. The rms roughness for the AFM images has obtained for undoped and doped samples. SEM micrographs have shown that undoped samples are observed to be more compact than the doped samples doped due to the existence of pores. The potential of this research is to produce magnetoresistive read head such as read/write heads in computer disc-drives, position sensor, magnetoresistive random access memory (MRAM), biomagnetic sensor and magnetic accelerometers.

A novel design of high isotropy single mass six-degree-of-freedom (6-DOF) accelerometer has been developed and investigated. In the accelerometer, six spatial coordinates (three linear and three angular) of the inertial mass and their derivatives are observed by simple measurement of linear displacements of six optimally chosen points of the inertial mass. Calculation of the six acceleration components is then possible according to a specially developed mathematical algorithm. To provide the isotropy of the device’s sensitivity and to achieve the accuracy in the measurement of the linear and angular accelerations, three subsystems of the device — inertial, suspension, and measurement subsystems — have a spatially symmetrical structure. To provide the symmetrical structure of the inertial subsystem, the proof mass is manufactured from uniform material and has a cubic shape. All structural cavities in this cube (light guides and a light source cavity) are symmetrical relative to three coordinate axes. To provide the symmetry of suspension subsystem 24 elastic supports (springs) are mounted by three in all vertexes of the cube in the directions of X-, Y- and Z-axes. The springs have the same dimensions and stiffness. The damping elements (the rubber insets) are inserted into the springs. They are made of the same material and have the identical dimension. The measurement subsystem consists of six differential optical displacement sensors and the light source which is mounted in the center of the cube. Each optical sensor is based on three-component position-sensitive detectors (PSD) of a segmented type. This design ensures output signals that are independent of fluctuations in light source brightness and of optical and electromagnetic interferences. Optical sensors are mounted on the frame of the accelerometer and situated symmetrically opposite to the centers of the square faces of the cube. Six orts of measurement directions form three orthogonal pairs. The experimental model of isotropic 6-DOF accelerometer with differential optical measurement subsystem is manufactured, adjusted and tested. For this purpose the experimental apparatus consisting of the stand with standard accelerometers and computer-controlled data gathering and analysis system (multi-channel amplifier, analog-digital converter and LabView software system) is developed. The preliminary experiment results show that proposed device has high level of signal isotropy and it is hoped to have a good perspective for industrial application were it can replace the complex gyroscopic and combined multi-axis devices.