Sensors for autonomous small robotic platforms must be low mass, compact size and low power due to the
limited space. For such applications, as the dimensions of the structures shrink, standard machining
methods are not suitable because of low fabrication tolerances and high cost in assembly. Commonly, the
structures show a high degree of fabrication complexity due to error in alignment, air gaps between
conductive parts, poor metal contact, inaccuracy in patterning because of non-contact lithography, complex
assemblies of various parts, and high number of steps needed for construction. However, micromachining
offers high fabrication precision, provides easy fabrication and integration with active devices and hence is
suitable for manufacturing high MMW and submillimeter-wave frequency structures. A radar design
compatible with micromachining process is developed to fabricate a Y-band high resolution radar structure
with a slot-fed patch array antenna. A multi-step silicon DRIE process is developed for the fabrication of
the waveguide structure while the slots are suspended on a thin oxide/nitride/oxide membrane to form the
top cover of the waveguide trenches and the patch elements are suspended on a thin Parylene membrane.
Gold thermocompression bonding and Parylene bonding are used to assemble different parts of the antenna.
These processes result in a compact (4.5 cm × 3.5 cm × 1.5 mm) and light-weight (5 g) radar.
This paper presents the development of a static estimator for obtaining state information from optic flow and
radar measurements. It is shown that estimates of translational and rotational speed can be extracted using a
least squares inversion. The approach is demonstrated in a simulated three dimensional urban environment on an
autonomous quadrotor micro-air-vehicle (MAV). The resulting methodology has the advantages of computation
speed and simplicity, both of which are imperative for implementation on MAVs due to stringent size, weight,
and power requirements.
Autonomous small robotic platforms require a suite of sensor to navigate and function in complex environment. Due to
limited space, onboard power, and processing capability these sensors must be low mass, compact size, low power, and
run with minimal processing resources. We are in the process of developing a compact and low-power imaging mm-wave
radar system for small autonomous robotic platforms operating at Y-band to allow for navigation and obstacle
detection in conditions that make the use of passive optical sensors difficult or impossible. The radar system is being
fabricated and assembled using silicon micromachining technique with the overall mass of 5 grams, peak power of 200
mW, and operational power of 6.7 mW for one frame per second update rate, field of view of ± 25°, angular resolution
of 2°, range resolution of 37.5cm, and range of 400m. The beam steering is accomplished by frequency scanning and the
range resolution is obtained from the standard FMCW technique utilizing a chirped signal waveform with step
discontinuities. This paper will present the overall architecture of this radar system in addition to the phenomenological
investigation of scattering from obstacle in indoor environment. It is also shown how radar images taken from indoor
scenes can be interpreted and utilized to create the interior layout of a building.
Ad hoc communication among small robotic platforms in complex indoor environment is further challenged by three
limiting factors: 1) limited power, 2) small size antennas, and 3) near-ground operation. In complex environments such
as indoor scenarios often times the line-of-sight communication cannot be established and the wireless connectivity must
rely on multi-path propagation. As a result, the propagation path-loss is much higher than free-space, and more power
will be needed to obtain the need coverage. Near ground operation also leads to increased path-loss. To maintain the
network connectivity without increasing the required power a novel high gain miniaturized radio repeater is presented.
Unlike existing repeater systems, this system utilizes two closely spaced low profile miniaturized planar antennas
capable of producing omnidirectional and vertical radiation patterns as well as a channel isolator layer that serves to
decouple the adjacent antennas. The meta-material based channel isolator serves as an electromagnetic shield, thus
enabling it to be built in a sub-wavelength size of 0.07λ0
2 × λ0/70, the smallest repeater ever built. Also wave propagation
simulations have been conducted to determine the required gain of such repeaters so to ensure the signal from the
repeater is the dominant component. A prototype of the small radio repeater is fabricated to verify the design
performance through a standard free-space measurement setup.
The Army Research Laboratory established the Micro Autonomous Systems and Technology (MAST) Collaborative
Technology Alliance (CTA) program in 2008 to leapfrog technological barriers toward achieving the
autonomous operation of a collaborative ensemble of multifunctional, mobile microsystems. This goal will be realized
through fundamental advancements by the MAST alliance, composed of four centers with focused research
activities in Microsystems Mechanics, Processing for Autonomous Operation, Microelectronics, and Integration.
A team of researchers assembled by the University of Michigan was chosen to lead the microelectronics center.
This paper provides an overview of research activities in the MAST Microelectronics Center. Research activities
in this center are organized around five major research thrusts: 1) sensing, 2) low power processing, 3)
communications, 4) navigation, 5) efficient power generation.
Such activities are envisioned to enable micro-autonomous sensor platforms by developing novel electronic
sensors and devices having the following attributes: low power and power efficient characteristics, low mass
and volume, enhanced functionality/sensitivity, survivability, durability, extended operation capability, low cost,
and fault tolerance. Fundamental advances in microelectronics will be accomplished through implementation of
bio-mimetic and bio-inspired techniques and technologies, utilization of Nano/micro fabrication processes, and
incorporation of novel materials in fabrication of components and subsystems.
Calculation of the electromagnetic scattering form a buried object, such as a landmine, under acoustic vibration requires a scattering solution for an object beneath an interface with acoustically-induced surface roughness. An analytical solution is presented for the electromagnetic scattering from a dielectric circular cylinder embedded in a dielectric half-space with a slightly rough interface. The solution utilizes the spectral representation of the fields and accounts for all the multiple interactions between the rough interface and the buried cylinder. First order coefficients from the small perturbation method are used for computation of the scattered fields from the rough surface. The derivation includes both TM and TE polarizations and can be easily extended for other cylindrical buried objects. Scattering scenarios are examined utilizing the new solution for a dielectric cylinder beneath both flat and arbitrary surface profiles.
A new approach for implementing electronically tunable antennas is presented in this paper. The basic concept is to vary the effective electrical length of the antenna by controlling the bias conditions of solid state switches mounted on the slot. The implemented antennas is resonating at three different frequencies spanning the range of 550 to 700 MHz with no matching networks required.
The idea of using acoustically induced Doppler spectra as a means for target detection and identification is introduced. To demonstrate feasibility of such a technique, an analytical solution for the calculation of the bistatic scattered Doppler spectrum from an acoustically excite, vibrating dielectric circular cylinder is presented. In this paper, the incident plane wave is assumed to be polarized along the axis of the cylinder is presented. In this paper, the incident plane wave is assumed to be polarized along the axis of the cylinder. A perturbation method is developed to calculate the electromagnetic scattering from a slightly deformed and inhomogeneous dielectric cylinder. Then, assuming the vibration frequency is much smaller than the frequency of the incident electromagnetic wave, a closed form expression for the time-frequency response of the bistatic scattered field is obtained. The solution for acoustic scattering from a solid elastic cylinder is applied to give the displacement on the surface as well as the compression and dilation within the cylinder. Both the surface displacement and the variation in material density within the cylinder contribute to the Doppler component of the of the electromagnetic scattered field. Results indicate that the scattered Doppler frequencies correspond to the mechanical vibration frequencies of the cylinder, and the sidelobe Doppler spectrum level is, to the first order, linearly proportional to the degree of deformation and is a function of bistatic angle. Moreover, the deformation in the cylinder, and thus the Doppler sidelobe level, only becomes sizeable near frequencies of normal modes of free vibration in the cylinder. These resonant frequencies are found to depend only on the object properties and are independent of the surrounding medium. Utilizing the information in the scattered Doppler spectrum could provide an effective means of buried object identification, where acoustic waves are used to excite the mechanical resonances of a buried object.