Travis Deyle

Hambone: A Bio-Acoustic Gesture Interface

Mobile input technologies can be bulky, obtrusive, or difficult to use while performing other tasks. In this paper, we present Hambone, a lightweight, unobtrusive system that affords quick access, subtlety, and multitasking capabilities for gesture-based mobile device interaction. Hambone uses two small piezoelectric sensors placed on either the wrist or ankle. When a user moves his hands or feet, the sounds generated by the movement travel to Hambone via bone conduction. Hambone then transmits the signals digitally to a mobile device or computer. The signals are recognized using hidden Markov models (HMMs) and are mapped to a set of commands controlling an application. In this paper, we present the hardware and software implementation of Hambone, a preliminary evaluation, and a discussion of future opportunities in bio-acoustic gesture-based interfaces.

RF vision: RFID receive signal strength indicator (RSSI) images for sensor fusion and mobile manipulation

In this work we present a set of integrated methods that enable an RFID-enabled mobile manipulator to approach and grasp an object to which a self-adhesive passive (battery-free) UHF RFID tag has been affixed.

Probabilistic UHF RFID tag pose estimation with multiple antennas and a multipath RF propagation model

We present a novel particle filter implementation for estimating the pose of tags in the environment with respect to an RFID-equipped robot. This particle filter combines signals from a specially designed RFID antenna system with odometry and an RFID signal propagation model. Our model includes antenna characteristics, direct-path RF propagation, and multipath RF propagation. We first describe a novel 6-antenna RFID sensor system that provides the robot with a 360-degree view of the tags in its environment. We then present the results of real-world evaluation where RFID-inferred tag position is compared with ground truth data from a laser range-finder. In our experiments the system is shown to estimate the pose of UHF RFID tags in a real-world environment without requiring a priori training or map-building. The system exhibits 6.1 deg mean bearing error and 0.69 m mean range error over robot to tag distances of over 4 m in an environment with significant multipath. The RFID system provides the ability to uniquely identify specific tagged locations and objects, and to discriminate among multiple tagged objects in the field at the same time, which are important capabilities that a laser range-finder does not provide. We expect that this new type of multiple-antenna RFID system, including particle filters that incorporate RF signal propagation models, will prove to be a valuable sensor for mobile robots operating in semi-structured environments where RFID tags are present.

Surface based wireless power transmission and bidirectional communication for autonomous robot swarms

We introduce an inexpensive, low complexity power surface system capable of simultaneously providing wireless power and bidirectional communication from a surface to multiple mobile robots. This system enables continuous operation of a swarm-sized population of battery-less robots. Our first prototype consists of a 60 cm times 60 cm power surface that provides power and bidirectional communication to an initial evaluation group of five test robots, each one consuming 200 mW. Unlike typical non-resonant inductive (transformer) coupling, power transmission in this system is achieved through magnetic flux coupling between a high Q L-C resonator placed beneath the operating surface and a non-resonant pickup coil on each robot. We explore the design of the pickup coil and conditioning circuitry, and we characterize the position-dependent power density of a static load representative of a small autonomous robot operating on the surface. We demonstrate a continuous power density averaging 4.1 mW/cm2 for a static load, and develop much greater peak power for dynamic loads via capacitor storage and power conditioning circuitry. We also demonstrate simultaneous broadcast communication between the surface and all robots via amplitude modulation of the magnetic field, and communication between individual robots and the surface via load modulation.

A list of household objects for robotic retrieval prioritized by people with ALS

Studies have consistently shown that object retrieval would be a valuable task for assistive robots to perform, yet detailed information about the needs of patients with respect to this task has been lacking. In this paper, we present our efforts to better understand the needs of motor impaired patients with amyotrophic lateral sclerosis (ALS) with the goal of informing the design and evaluation of assistive mobile robots.

1000 Trials: An empirically validated end effector that robustly grasps objects from the floor

Unstructured, human environments present great challenges and opportunities for robotic manipulation and grasping. Robots that reliably grasp household objects with unknown or uncertain properties would be especially useful, since these robots could better generalize their capabilities across the wide variety of objects found within domestic environments.

Finding and Navigating to Household Objects with UHF RFID Tags by Optimizing RF Signal Strength

We address the challenge of finding and navigating to an object with an attached ultra-high frequency radio-frequency identification (UHF RFID) tag. With current off-the-shelf technology, one can affix inexpensive self-adhesive UHF RFID tags to hundreds of objects, thereby enabling a robot to sense the RF signal strength it receives from each uniquely identified object. The received signal strength indicator (RSSI) associated with a tagged object varies widely and depends on many factors, including the objects pose, material properties and surroundings. This complexity creates challenges for methods that attempt to explicitly estimate the objects pose. We present an alternative approach that formulates finding and navigating to a tagged object as an optimization problem where the robot must find a pose of a directional antenna that maximizes the RSSI associated with the target tag. We then present three autonomous robot behaviors that together perform this optimization by combining global and local search. The first behavior uses sparse sampling of RSSI across the entire environment to move the robot to a location near the tag; the second samples RSSI over orientation to point the robot toward the tag; and the third samples RSSI from two antennas pointing in different directions to enable the robot to approach the tag. We justify our formulation using the radar equation and associated literature. We also demonstrate that it has good performance in practice via tests with a PR2 robot from Willow Garage in a house with a variety of tagged household objects.

Rich-Media Tags: Battery-free wireless multichannel digital audio and image transmission with UHF RFID techniques

In this paper we present the first fully passive (battery-free) wireless transmission of multiple digital audio channels and images via modulated backscatter. We leverage a previously reported single chip, passive transponder that can digitize and uplink up to 10 analog input channels sampled at a rate of 26.1 kHz. Given a base station transceiver operating at a frequency of 915 MHz and a transmit power of +36 dBm EIRP, the transponder has a demonstrated operating range of ≈1.4 m. The transponder data uplink uses binary phase-shift key (BPSK) modulated backscatter operating at a total link throughput rate of 5 Mbps, with an uplink energy consumption of only 3.7 pJ/bit. The transponder was initially designed for biomedical telemetry of neural and EMG signals. We present a new application of this tag for multichannel, high fidelity digital audio recording, as well as color image transfer using a slow-scan television (SSTV) modulation (PD290) with a resolution of 640 by 493 pixels. Additionally, we demonstrate fully-passive digital recording of ambient sound using a microphone powered by the chips harvested energy at an operating range of 0.72 m. The passive, digital microphone is sensitive enough to record human speech within approximately 5 m of the device. We believe these results will serve as a first step toward media-rich battery-free (wirelessly powered) devices that take advantage of the high speed, low power nature of modulated backscatter communication links.

Visual odometry and control for an omnidirectional mobile robot with a downward-facing camera

An omnidirectional Mecanum base allows for more flexible mobile manipulation. However, slipping of the Mecanum wheels results in poor dead-reckoning estimates from wheel encoders, limiting the accuracy and overall utility of this type of base. We present a system with a downward-facing camera and light ring to provide robust visual odometry estimates. We mounted the system under the robot which allows it to operate in conditions such as large crowds or low ambient lighting. We demonstrate that the visual odometry estimates are sufficient to generate closed-loop PID (Proportional Integral Derivative) and LQR (Linear Quadratic Regulator) controllers for motion control in three different scenarios: waypoint tracking, small disturbance rejection, and sideways motion. We report quantitative measurements that demonstrate superior control performance when using visual odometry compared to wheel encoders. Finally, we show that this system provides high-fidelity odometry estimates and is able to compensate for wheel slip on a four-wheeled omnidirectional mobile robot base.

Battery-free multichannel digital ECG biotelemetry using UHF RFID techniques

We propose to leverage UHF RFID techniques to yield a continuously wearable, battery-free wireless multichannel ECG telemetry device that is potentially disposable, low-cost and suitable for integration with multiple electrodes in a flexible circuit assembly. Such a device could have broad applicability, ranging from initial patient assessment by first responders, to continuous monitoring in various clinical settings. We employ a recently described single-chip data acquisition system including RF power harvesting to eliminate the need for a battery. The single-chip system includes 14 channels of integrated biopotential amplification, an 11-bit ADC, and a 5 Mbps digital backscatter telemetry link. We present an initial characterization of the telemetry chip in this application including battery-free, wireless 3 and 5 channel ECG recordings made from an ambulatory human subject at a range of ≈ 1 meter.