This paper performs a design parameter study for development of a self-powering brain neurostimulation system by harvesting deformation energy generated from mandibular (lower jaw) movements. For decades, scientists recognized that electrical stimulation of the brain (deep brain stimulation, DBS) has the potential to treat a variety of refractory medical conditions including chronic pain, Parkinson’s disease, movement disorders, major depression and epilepsy. A commercial DBS device comprise a stimulation lead, neurostimulation unit with microcontroller, and a battery for power supply. The batteries in DBS need replacement every 3~5 years and thus problematic because additional surgery is required to replace them. This paper describes an innovative technology to power DBS by converting stresses/strains in the mandible caused by jaw movements into electrical energy using piezoelectricity. The proposed energy harvester has a multilayer layout composed of piezoelectric composite and biocompatible titanium layers, and will be secured in place on the body of the mandible using titanium screws. For optimal design of this harvester, we build an experimentally verified FEM model for the mandible and harvester assembly, and perform parameter study of the energy harvester. The parameter study on the size/location of the piezoelectric material as well as its cross sectional properties of piezoelectric harvester is performed and experimentally tested. Its practical use by integrating it with electrical circuit is also discussed.
A wireless structure health monitoring (SHM) system for wind turbine blades has been actively researched to realize its low cost and efficient maintenance. A sustainable power supply to the wireless SHM system installed in a rotating blade has been one of the most challenging issue. Vibration energy harvesting via piezoelectricity or electromagnetism can provide a solution, but varied blade rotation and the corresponding random natured vibration make it difficult to design a practical harvester. In this paper, an impact-driven piezoelectric energy harvester (PEH) is proposed to efficiently generate an electric power at PEH’s natural frequency for any rotation speed of blades. This harvester can be installed within the blade to power the wireless SHM system sustainably. The impact-driven PEH consists of a piezoelectric cantilever beam and a gravity-induced rotator. When the wind turbine blade rotates, the orientation of the cantilever changes but the orientation of the gravity-induced rotator remains fixed to a global coordinate system (defined on the earth). At every rotation cycle, the gravity-induced rotator strikes the cantilever tip, which causes vibration. Then, the piezoelectric cantilever beam generates electric power at PEH’s natural frequency. A testing setup for the proposed PEH is built, by installing the PEH prototype on the blades driven by a DC motor. Experimental result shows that the proposed PEH generates electric power at PEH’s natural frequency for any rotation speed, and average power generated from the proposed PEH is 1.56 mW at the typical blade’s rotation speed of 20 RPM.
In this paper a piezoelectric energy harvester for scavenging wasted vibration energy inside a vehicle tire is designed and its performance is experimentally verified. Piezoelectric type energy harvesters can be used to collect vibrational energy and power such systems, but they need to be carefully designed to address power generation and durability performances. In this study, we address a reliability based design optimization (RBDO) approach to design the harvester that considers the uncertainty in dimensional tolerances and material properties, to be compared to the traditional deterministic design optimization (DDO). Both designs are manufactured for the experimental evaluation to demonstrate the merits of RBDO design over DDO.
Implementation of energy harvesting technology can provide a sustainable, remote power source for soldiers by reducing the battery weight and allowing them to stay in the field for longer periods of time. Among multiple energy conversion principles, electromagnetic induction can scavenge energy from wasted kinematic and vibration energy found from human motion. Hip displacement during human gait acts as a base excitation for an energy harvesting backpack system. The placement of a permanent magnet in this vibration environment results in relative motion of the magnet to the coil of copper wire, which induces an electric current. This current can be saved to a battery or capacitor bank installed on the backpack to be used to power electronic devices. The purpose of this research is to construct a reliable simulation model for an electromagnetic vibration energy harvester and use it for a multi-variable optimization algorithm to identify an optimal coil and magnet layout for highest power output. Key components of the coupled equations of motion such as the magnetic flux density and coil inductance are obtained using ANSYS multi-physics software or by measuring them. These components are fed into a harvester simulation model (e.g. coupled field equations of motion for the backpack harvester) that generates the electrical power output. The developed simulation model is verified with a case study including an experimental test. Then the optimal design parameters in the simulation model (e.g., magnet layout, coil width, outer coil diameter, external load resistance) are identified for maximum power. Results from this study will pave the way for a more efficient energy harvesting backpack while providing better insight into the efficiency of magnet and coil layout for electromagnetic applications.
The paper proposes a fully mechanical air curtain system that will be powered solely by harvested energy from common hinged doors. The average person uses this type of door several times a day with an almost unconscious amount of applied force and effort. This leads to a high potential of energy to be harvested in doorways that see high traffic and frequent operation7 . Frequently opened door entry ways have always been regarded as a major element that causes significant energy loss and contaminated air conditions in buildings6 . Private companies, particularly those with warehouses, have introduced commercial electrical air curtains to block the open entrances from invading cold air11. This project intends to introduce an original design of air curtain which operates fans only when the door opens and closes, by directly converting door motion to fan rotation without any electronic motor or power cable. The air stream created by this device will prevent the transfer of outside air and contaminants. Research will be conducted to determine the most efficient method of harvesting energy from door use, and the prototyping process will be conducted to meet the required performance of current air curtain models.
This paper proposes a new efficient motion conversion system which can be used in an energy harvesting system that converts wasted kinematic energy into electrical energy. In the proposed system, a reciprocating translational motion will be converted into one-directional rotational motion that spins a generator. The system will be devised with a two overlapping chambers (chamber 1 and 2) which move relatively through the sliding joint, and a pair of flexible strings (belt, steel wire, or chain) run around the rotor of the generator. Each end of the string fixed to chamber 1 is designed not to interfere with chamber 2 where the generator is mounted. When the two chambers move relatively, either top or bottom string is tensioned to spin the rotor while the other string is being rewound. One-directional clutch with a coil spring is engaged in a rewinding system – as found in a rowing machine, for example – so each string actuates the rotor only when it is in tension. This device can be applied to any mechanism where reciprocating translational motion exists, such as linear suspension system in a vehicle, a bicycle, and an energy generating marine buoy. The experimental study result will be reported as well as its battery-charging capacity will be demonstrated.
In this paper, we perform design parameter study and design optimization for a piezoelectric energy harvester considering vehicle speed variation. Initially, a FEM model using ANSYS is developed to appraise the performance of a piezoelectric harvester in a rotating tire. The energy harvester proposed here uses the vertical deformation at contact patch area from the car weight and centrifugal acceleration. This harvester is composed of a beam which is clamped at both ends and a piezoelectric material is attached on the top of that. The piezoelectric material possesses the 31 mode of transduction in which the direction of applied field is perpendicular to that of the electric field. To optimize the harvester performance, we would change the geometrical parameters of the harvester to obtain the maximum power. One of the main challenges in the design process is obtaining the required power while considering the constraints for harvester weight and volume. These two concerns are addressed in this paper. Since the final goal of this study is the development of an energy harvester with a wireless sensor system installed in a real car, the real time data for varied velocity of a vehicle are taken into account for power measurements. This study concludes that the proposed design is applicable to wireless tire sensor systems.
The power output of a vibration energy harvesting device is highly sensitive to uncertainties in materials, manufacturing,
and operating conditions. Although the use of a nonlinear spring (e.g., snap-through mechanism) in energy harvesting
device has been reported to reduce the sensitivity of power output with respect to the excitation frequency, the nonlinear
spring characteristic remains significantly sensitive and it causes unreliable power generation. In this paper, we present a
reliability-based design optimization (RBDO) study of vibration energy harvesters. For a nonlinear harvester, a purely
mechanical nonlinear spring design implemented in the middle of cantilever beam harvester is considered in the study.
This design has the curved section in the center of beam that causes bi-stable configuration. When vibrating, the inertia
of the tip mass activates the curved shell to cause snap-through buckling and make the nature of vibration nonlinear. In
this paper, deterministic optimization (DO) is performed to obtain deterministic optimum of linear and nonlinear energy
harvester configuration. As a result of the deterministic optimization, an optimum bi-stable vibration configuration of
nonlinear harvester can be obtained for reliable power generation despite uncertainty on input vibration condition. For
the linear harvester, RBDO is additionally performed to find the optimum design that satisfies a target reliability on
power generation, while accounting for uncertainty in material properties and geometric parameters.
The increasing interest in engineering systems with excellent mitigation of vibration and shock has required novel design approaches which provide systems with passive adaptive performance across the different fields of engineering. In this paper we present a novel modular design concept to synthesize passive adaptive structures upon a varied loading condition. This concept interconnects linear and nonlinear structural elements depending on the scale and performance requested to the final structural system. To realize this concept we developed a structural synthesis tool integrated with the genetic algorithm. The design optimization problem is formulated considering the prescribed design requirement on stiffness and damping performance. This tool optimally synthesizes the structural network by assembling the available constitutive elements in the set and successfully obtains passive adaptive assembly upon a varied loading condition in terms of vibration amplitude and frequency.
This paper proposes design optimization of a mechanically decoupled six-axis F/T sensor. In order to indicate the
biggest cross coupling error of a Maltese cross type F/T six-axis sensor, principal error is proposed in this paper.
Locations of twenty-four strain gages are determined and four design variables are selected to solve optimization
problem. The average of principal couplings and output strain levels are chosen as the objective function and the
constraints respectively. An effective optimization framework is suggested, which utilizes interaction between FEM
software ANSYS and MATLAB by using morphing technique. As a result of optimization, the biggest coupling error is
reduced from about 35% to 2.5%, which is satisfactory for use of mechanically decoupled six-axis F/T sensors.
Experimental verification is conducted and it is shown that there is maximum 5.1 % difference in strain outputs of
numerical and experimental results, which verifies the validity of suggested FE model. The design formulation and
framework proposed in this study are expected to promote researches on multi-axis F/T sensors and their
commercialization in various industries.
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