Peter D. Washabaugh

• University of Michigan

The use of active illumination on CubeSats allows tracking of low Earth orbit (LEO) satellites during Earth eclipse with simple ground-based instruments. Position, attitude, and telemetry of spacecraft parameters can be determined using light emitting diodes (LEDs) on spacecraft. On the local night of May 10, 2018, the University of Michigan succes...

We report the development of fully integrated peristaltic multistage (18-, 4-, and 2-stage) electrostatic gas micropumps with integrated active microvalves. These micropumps uniquely combine a number of approaches to achieve highpressure, high flow rate, multimode, and low-power pumping of compressible gases: (1) multistage (up to 18-stage) configu...

*† ‡ § ** †† , The Flying Fish platform is an ocean, environmental monitoring buoy that repositions as an Unmanned Aerial System (UAS), maintaining a pre-set watch circle. To operate in the open ocean, the platform must be robust to moderate sea state conditions and must function unattended thus fully-autonomously. Our concept was conceived as an a...

Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/57830/1/AcousticDuctTCST1996.pdf

An explicit analytical solution is obtained for the stress field in an accreted triaxial ellipsoid under the influence of self-gravitation and rotation. Material is assumed to attach to the surface of the accreting body in a stress-free state, after which it behaves elastically. The results differ significantly from the classical elasticity solutio...

A dynamic crack propagating in a brittle material releases enough thermal energy to produce visible light. The dynamic fracture of even macroscopically amorphous materials becomes unsteady as the crack propagation velocity approaches the material wave-speeds. The heat generated at a crack-tip, especially as it jumps, may be a mechanism to initiate...

We report (1) the integration of the first functioning MEMS gas chromatography system ( muGC) featuring a micropump, a micro-column, and a micro-chemiresistor sensor array; and (2) experimental demonstration of the state-of-the-art multi-vapor gas separation and detection. In particular, we report the best GC analysis data from the first micropump-...

This paper describes theoretical analyses and experimental characterization of high frequency multi-stage micropumps. The MEMS-fabricated micropumps have been developed for use in a highly-integrated micro gas chromatograph system for chemical analysis. Tests are reported on a 20x, two-stage pump and MEMS-fabricated micropumps and the results used...

We report the design, fabrication, and test results of a fully integrated peristaltic 18-stage gas micropump consisting of 18 serially-connected pumping chambers and 19 microvalves. The peristaltic micropump achieves (1) high-pressure differentials by accumulating small pressure differentials that are evenly distributed across the individual stages...

This paper reports the development of a low-power electrostatic microthruster based-on Helmholtz resonance. This fluidic resonance phenomenon is utilized to create high-speed jets of air for thrust generation. The microthruster contains a curved-electrode (~8.8 mum deep) and provides high force to, and large deflection of a vibrating membrane thus...

This paper reports experimental characterization of directional gas pumping generated by MEMS-fabricated checkerboard-type electrostatic microvalves. It is found that the oscillatory motion of the checkerboard microvalve membrane provides both the pumping and valve functions of a pump, namely: 1) to cause the volume displacement and, thus, compress...

We predict that when Asteroid 2004 MN4 passes 5.6 +/- 1.4 Earth radii from Earth's center oil April 13, 2029, terrestrial torques during the flyby will alter its,pill State in a dramatic manner that will be observable using groundbased telescopes. Although the asteroid will most likely not undergo catastrophic disruption. it may be subject to local...

A propulsion system based on acoustic streaming generated by Helmholtz resonators is presented. High frequency (>60 kHz) electrostatically driven micromachined Helmholtz resonators constitute the basic unit of the system. Microjets produced at the exit of these resonators can be combined to form a distributed propulsion system. A high yield (>85%)...

Analytical expressions are obtained for the stress field in a sphere that has grown by accretion while rotating about an axis at a speed which may vary during the accretion process. It is assumed that accretion occurs by the adherence of infinitesimal particles that are stress free at the instant of attachment and that the material of the sphere be...

A novel propulsion method suitable for micromachining is presented that takes advantage of Helmholtz resonance, acoustic streaming, and eventually flow entrainment and thrust augmentation. In this method, an intense acoustic field is created inside the cavity of a Helmholtz resonator. Flow velocities at the resonator throat are amplified by the res...

This paper reports a bi-directional electrostatic microspeaker that has three main features: (1) a thin and flexible Parylene membrane for large deflection (>7.5 mum), thus, large acoustic pressure generation, (2) dual electrodes on both sides of the membrane to pull it in two opposite directions and overcome the weak restoration force of the polym...

The terrestrial planets, asteroids, and comets all formed by the accretion of solid planetesimals. The maximum spin of these objects is determined from their stress fields and failure criterion. The typical elasticity analysis cannot be used to determine the stress fields of accreted bodies because it does not account for the manner in which the bo...

This paper presents a large-deflection electrostatic actuator with a curved fixed drive electrode and a flat moveable polymer electrode. Two new concepts are reported: fabrication of curved electrodes by buckling the electrode out of plane using compressive stress, and formation of large deflection parallel-plate electrostatic actuators using the c...

This paper reports for the first time the design, development and initial results from a micro power generator based on thermionic (TI) emission using combustion. Several major results are achieved. Thin-films of BaO are integrated with Si to form the emitter and collector of a TI converter. Field emission and TI emission currents are successfully...

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This paper reports the mechanical and thermal design of a MEMS-fabricated micro power generator based on thermionic emission and catalytic combustion. Thermionic power generation results from electron emission from a hot emitter to a cold collector. Scaling analysis reveals that the miniaturization of a thermionic generator is favorable to output p...

A dynamic model of MEMS-fabricated multistage micro vacuum pumps for use in a highly-integrated chemical monitoring system is described. A thermodynamic analysis shows that in order to meet the performance requirements of the system, the micro pump must be operated at very high frequency of approximately 50 kHz. At these frequencies, dynamic effect...

A closed form solution for a uniform, isotropic, homogenous, rotating, and self-gravitating solid ellipsoid is analyzed as a function of its material properties and angular momentum. This solution recovers the classical results for an incompressible material, namely that Maclaurin and Jacobi ellipsoids minimize the total strain energy of an ellipso...

Various configurations and geometric scales of solar sails are compared with alternate advanced propulsion technologies. The study illuminates certain critical parameters such as the specific stiffness of the structure, a minimum area density, a minimum 'smoothing stress', and a need for long duration missions (e.g. > 100 days). As the thrust requi...

This paper presents the performance characterization and optimization of micromachined acoustic ejectors (MACE) and their application in micro propulsion and gas pumping. The MACE array utilizes forced Helmholtz resonators coupled with an acoustic ejector to produce high-speed micro-jets at resonance. A micro-jet with "near-field" velocity of ~0.8...

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Experimental analysis is presented of the flow structure and performance of axisymmetric synthetic jets. We report direct thrust and Particle Image Velocimetry (PIV) measurements at varying amplitude and frequency for Reynolds numbers in the range 200-2200. It is shown that the jet performance is determined by the flow length, L, defined as the len...

The performance of synthetic jets produced by an electrostatically driven acoustic resonator is discussed. A reduced order model of the coupled membrane motion and acoustic field in the resonator is used to determine thrust and power consumption. The coupled system presents unique features depending on the pressure coupling parameter defined as the...

The thrust produced by synthetic jets designed for micro jet propulsion is discussed. The proposed propulsion system consists of synthetic wall jets located at the throat of an ejector shroud that are powered by Helmholtz-type acoustic resonators. The theory of acoustic resonators is described and the thrust produced by the resonators calculated. T...

This paper reports a micromachined combustor and its application to micro thermoelectric power generation. The combustor chamber is covered by a ∼1.3μm thick dielectric diaphragm which is supported by a silicon support rim bonded to a glass substrate. The diaphragm is coated with Pt-catalyst and incorporates a heater for ignition. Scaling effects o...

Theory, manufacturing and experimental results of acoustically generated micromachined jet arrays for micropropulsion applications are presented. A reduced order theoretical analysis is found to be an accurate performance predictor. Scaling laws derived from the theory suggest the performance benefits derived by reducing the geometric size of the r...

A micromachined acoustic ejector (MACE) chip contains electrostaticatly-driven Heimholtz resonators that generate small air jets. A 1.6×1.6 cm² prototype contains 25 e-jets with 1m/s measured velocity. Results show that a 15-jet device located ∼1cm above a 100°6 surface dissipates >6W/m²K. Future generations are being designed with higher jet veloc...

An experimental study of axisymmetric synthetic jets is presented examining the relation between propulsion efficiency and vortical flow structure. The flow field is periodic: individual vortex rings are created at the operating frequency of the synthetic jet, each possibly with trailing vorticity. The relevant operational parameters are the nozzle...

The University of Michigan has developed a fixed-wing model aircraft (Solus) with an embedded control system to develop and demonstrate UAV technology. The analytical objective of this project is the development of intelligent flightcontrol and trajectory planning techniques, focusing on automated fault detection and recovery. Our experimental obje...

High speed micro-jets produced by acoustic streaming can be used for micro propulsion in miniature airborne vehicles. A wafer-level technology was developed to fabricate hundreds of resonators to form these jets on a 4-inch silicon wafer. In this paper, modeling and full characterization of these jets is presented. The performance of electrostatic...

A control scheme for electrostatically shaping a membrane is developed. The scheme achieves stabilization of the first mode of the membrane at a desired equilibrium, that may be open loop unstable, without violating specified state and control constraints. The ideas on the use of an "equilibrium-parametrized" family of Lyapunov functions to enforce...

This paper reports a micromachined thermoelectric (TE) power generator based on catalytic combustion in a micromachined combustion chamber. The 2mm×8mm×0.5mm combustion chamber is covered by a dielectric diaphragm supported on a silicon substrate that is bonded to a glass substrate. The generator integrates polysilicon-Pt thermopiles on the diaphra...

This paper reports a high-density (23 units/cm2) all-silicon micromachined acoustic ejector array utilizing Helmholtz resonators coupled with an acoustic ejector for the generation of high-speed micro-jets needed in applications such as micro propulsion, jet cooling, and pumping. The ejector array has been fabricated by using a novel 3D MEMS techno...

Presents a Lyapunov function approach to the control of nonlinear systems that are subject to pointwise-in-time constraints on state and control. This approach is applied to an electromechanical system that serves as a prototype for the first mode of an electrostatically shaped membrane. Electrostatically shaped membranes have been proposed as mirr...

A distributed micromachined ultrasound source is presented. Electrostatic actuators operating at frequencies exceeding 100 kHz are coupled to a Helmholtz resonator in order to achieve high output velocities. They consist of a 1200 μm×1200 μm×1.36 μm composite diaphragm, a perforated P++ backplate and a 3 μm air gap. The actuators cover the entire s...

An acoustic resonator coupled with an ejector shroud is being studied as a suitable propulsion system for Micro Airborne Vehicles (MAV's). The acoustic resonator uses an electrostatically actuated vibrating diaphragm to create an acoustic wave that is amplified in a resonator cavity and focused in an adjoining nozzle to produce acoustic streaming....

The simultaneous optimization of material properties and structural layout for an elastic continuum is formulated and analyzed. The objective is to obtain the maximum structural stiffness for prescribed surface loads and displacements, taking into account a body force that depends on the structural layout. Optimization with an account of self-weigh...

Inflatable, ultra-lightweight antennas using metallized membranes for reflectors are being investigated for use in orbital telescopes and solar energy applications. Simulation results for the control of a simplified model of a membrane using an electric field are reported. The non-linear mapping from position and acceleration of the center of the m...

We discuss a stabilization problem that arises from the problem of forming an optical aperture by deforming a flexible membrane. The basic idea is that a planar circular membrane with uniform radial in-plane tension subjected to a uniform normal stress assumes a paraboloidal shape, which is very close to the ideal shape for a primary mirror. We can...

A control scheme for electrostatically shaping a membrane is developed. The scheme achieves stabilization of the first mode of the membrane at a desired equilibrium, that may be open loop unstable, without violating specified state and control constraints. The ideas on the use of an “equilibrium-parametrized” family of Lyapunov functions to enforce...

The purpose of this project was to develop a rigorous theoretical foundation of the design of structures incorporating general "smart" materials, and to explore, extend and develop the use of sensors and actuators that employ "finite length" paths. It is anticipated that this project will fundamentally impact the practice of designing passive and a...

A formulation is presented for optimal design in the setting of linear elastostatics for continuum structures, where the modulus tensor field is expressed as a decomposition into a set of independent tensors. For the linear case at hand, net material properties simply equal the sum of the constituent tensor fields. The design variables are comprise...

In order to examine the problem of deforming a membrane into a paraboloid shape by means of electrostatic forces, we consider a system involving a mass, a spring, and an electromagnet. We show that if the equilibrium gap is less than two-thirds of the relaxed gap, then the equilibrium is unstable. We then demonstrate controllers that stabilize thes...

BRIEF NOTES particular, the result will depend on the order in which the impulsive forces are applied. Example 1. Examine the collision without friction of a rigid body with two other bodies. The impulsive forces are collinear with normal vectors hi.2 to the body surface at contact points A~.2. The condition (12) has form (n~, n2) + M(J ~(r2 × n2),...

Although active noise control has been a subject of interest for over 50 years, it has become feasible only with recent technological advances. This paper formulates the problem of noise control in a one-dimensional acoustic duct in a form that lends itself to the application of feedback control theory. In contrast to most of the literature on the...

It is theoretically possible to place long fiber-optic displacement sensors on structures that are generally loaded and still maintain the ability to exactly discriminate signals of interest. The chief advantage of finite-length fiber-optic sensors is that the sensitivity of the measurement scales not only with the maximum strain along the path but...

Following earlier observations of multiple micro-crack formation accompanying crack propagation under dynamic conditions, the question regarding the discrepancy between the “theoretically anticipated” maximal crack (Rayleigh wave) speed and those observed typically in amorphous, isotropic solids is examined experimentally. It is shown that if the p...

Frequently, when designing a structure to incorporate integrated sensors, one sacrifices the stiffness of the system to improve sensitivity. However, the use of interferometric displacement sensors that tessellate throughout the volume of a structure has the potential to allow the precision and range of the component measurement to scale with the g...

We consider a single-input, single-output plant involving one control actuator (speaker) and one control sensor (microphone). Additional speakers and microphones are used to provide disturbances and to assess closed-loop performance. To simplify matters, we confine our consideration in this paper to the case of a collocated sensor and actuator, tha...

Recently it has been observed that it is theoretically possible to place long fiber optic displacement sensors on structures that are generally loaded while still maintaining the ability to exactly discriminate signals of interest. The chief advantage of such finite-length fiber optic sensors is that the sensitivity of the measurement scales not on...

A general method to monitor the structural integrity of prismatic structures composed of simple isotropic linear elastic materials is described and justified by a detailed mathematical model. This technique is distinct from usual approaches in that a small number of distributed sensors is shown to be sensitive to the presence of damage throughout t...

The application of a Twyman—Green interferometer to measurements in static and dynamic fracture mechanics is described. Twyman—Green interferometry shows the absence of a dominant singular field in the out-of-plane deformation in the vicinity of a crack. For relatively brittle fracture and except near the crack flanks, the spatial gradient of the o...

An extremum problem formulation for the equilibrium analysis of general structures made of stiffening material is applied to the analysis of trussed structures. The nonlinear material is modelled in a way to simulate an arbitrary, polygonal stress-strain relation; material properties may vary over the truss. The form of this convex nonlinear progra...

Frequently in designing a structure to incorporate integrated sensors the stiffness of the system is sacrificed to improve sensitivity. By incorporating finite length measurement paths that tessellate throughout the volume of a structure, a measurement's sensitivity can be optimized while retaining structural rigidity. Thus the transducer element c...

Following earlier observations of multiple micro-crack formation accompanying crack propagation under dynamic conditions, the question regarding the discrepancy between the ‘theoretically anticipated’ maximal crack (Rayleigh wave) speed and those observed typically in amorphous, isotropic solids is examined experimentally. It is shown that if the p...

The design of an instrument is described that measures three resultant force components and three resultant moment components acting on a surface. Within the framework of linear elastostatics of an isotropic homogeneous material the device separates to a given precision the six resultant load components. Sensor paths of finite length are employed....

A crack moving dynamically through a sheet of Polymethylmethacrylate at high average velocity is found in reality to propagate in a non-steady, periodic, and perhaps discontinuous fashion. The spatial period of the fracture process in the direction of travel, or banding morphology, is of millimeter size and is consistent both in magnitude and disco...

The out-of-plane displacement of amorphous polymethylmethacrylate plates rupturing at slow (0.1 mm/s), and fast (0.5 to 0.9 mm/µs) rates are measured using a Twymann-Green interferometer. The measured surface shapes within one plate thickness of the crack-tip do not compare well with the two-dimensional planar asymptotic approximation, but compare...

Techniques to examine dynamically propagating cracks in brittle media have progressed sufficiently to allow investigators to examine material behavior near the crack tip in regions where two dimensional assumptions are no longer valid. Boundary conditions can be prescribed to allow ample viewing time of near tip deformation. Refinements in high spe...

A laboratory arrangement was designed and built to burn coal dust under controlled conditions in order to investigate the formation of submicron particles. Measurements made using a transmission electron microscope showed results consistent with the evaporation/condensation analytical computer model developed. The trends observed are not considered...