Joseph A. Paradiso

Energy scavenging for mobile and wireless electronics

Energy harvesting has grown from long-established concepts into devices for powering ubiquitously deployed sensor networks and mobile electronics. Systems can scavenge power from human activity or derive limited energy from ambient heat, light, radio, or vibrations. Ongoing power management developments enable battery-powered electronics to live longer. Such advances include dynamic optimization of voltage and clock rate, hybrid analog-digital designs, and clever wake-up procedures that keep the electronics mostly inactive. Exploiting renewable energy resources in the devices environment, however, offers a power source limited by the devices physical survival rather than an adjunct energy store. Energy harvestings true legacy dates to the water wheel and windmill, and credible approaches that scavenge energy from waste heat or vibration have been around for many decades. Nonetheless, the field has encountered renewed interest as low-power electronics, wireless standards, and miniaturization conspire to populate the world with sensor networks and mobile devices. This article presents a whirlwind survey through energy harvesting, spanning historic and current developments.

Energy scavenging with shoe-mounted piezoelectrics

Decreasing size and power requirements of wearable microelectronics make it possible to replace batteries with systems that capture energy from the users environment. Unobtrusive devices developed at the MIT Media Lab scavenge electricity from the forces exerted on a shoe during walking: a flexible piezoelectric foil stave to harness sole-bending energy and a reinforced PZT dimorph to capture heel-strike energy.

Applying electric field sensing to human-computer interfaces

A non-contact sensor based on the interaction of a person with electric fields for human-computer interface is investigated. Two sensing modes are explored: an external electric field shunted to ground through a human body, and an external electric field transmitted through a human body to stationary receivers. The sensors are low power (milliwatts), high resolution (millimeter) low cost (a few dollars per channel), have low latency (millisecond), high update rate (1 kHz), high immunity to noise (>72 dB), are not affected by clothing, surface texture or reflectivity, and can operate on length scales from microns to meters. Systems incorporating the sensors include a finger mouse, a room that knows the location of its occupant, and people-sensing furniture. Haptic feedback using passive materials is described. Also discussed are empirical and analytical approaches to transform sensor measurements into position information.

PingPongPlus: design of an athletic-tangible interface for computer-supported cooperative play

This paper introduces a novel interface for digitally-augmentedcooperative play. We present the concept of the athletic-tangibleinterface, a new class of interaction which uses tangible objectsand full-body motion in physical spaces with digital augmentation.We detail the implementation of PingPongPlus, a reactive ping-pongtable, which features a novel sound-based ball tracking technology.The game is augmented and transformed with dynamic graphics andsound, determined by the position of impact, and the rhythm andstyle of play. A variety of different modes of play and initialexperiences with PingPongPlus are also described.

Steering Law Design for Redundant Single-Gimbal Control Moment Gyroscopes

Two steering laws are presented for single-gimbal control moment gyroscopes. An approach using the Moore-Penrose pseudoinverse with a nondirectional null-motion algorithm is shown by example to avoid internal singularities for unidirectional torque commands, for which existing algorithms fail. Because this is still a tangent-based approach, however, singularity avoidance cannot be guaranteed. The singularity robust inverse is introduced as an alternative to the pseudoinverse for computing torque-producing gimbal rates near singular states. This approach, coupled with the nondirectional null algorithm, is shown by example to provide better steering law performance by allowing torque errors to be produced in the vicinity of singular states.

Shoe-integrated sensor system for wireless gait analysis and real-time feedback

We are developing a sensor system for use in clinical gait analysis. This research involves the development of an on-shoe device that can be used for continuous and real-time monitoring of gait. This paper presents the design of an instrumented insole and a removable instrumented shoe attachment. Transmission of the data is in real-time and wireless, providing information about the three-dimensional motion, position, and pressure distribution of the foot. Using pattern recognition and numerical analysis of the calibrated sensor outputs, algorithms will be developed to analyze the data in real-time. Results will be validated by comparison to results from a commercial optical gait analysis system at the Massachusetts General Hospital (MGH) Biomoti on Lab.

An Inertial Measurement Framework for Gesture Recognition and Applications

We describe an inertial gesture recognition framework composed of three parts. The first is a compact, wireless six-axis inertial measurement unit to fully capture three-dimensional motion. The second, a gesture recognition algorithm, analyzes the data and categorizes it on an axis-by-axis basis as simple motions (straight line, twist, etc.) with magnitude and duration. The third allows an application designer to combine recognized gestures both concurrently and consecutively to create specific composite gestures can then be set to trigger output routines. This framework was created to enable application designers to use inertial sensors with a minimum of knowledge and effort. Sample implementations and future directions are discussed.

Musical Applications of Electric Field Sensing

The Theremin was one of the first electronic musical instruments, yet it provides a degree of expressive real-time control that remains lacking in most modern electronic music interfaces. Underlying the deceptively simple capacitance measurement used by it and its descendants are a number of surprisingly interesting current transport mechanisms that can be used to inexpensively , unobtrusively, robustly, and remotely detect the position of people and objects. We review the relevant physics, describe appropriate measurement instrumentation, and discuss applications that began with capturing virtuosic performance gesture on traditional stringed instruments and evolved into the design of new musical interfaces.

The magic carpet: physical sensing for immersive environments

An interactive environment has been developed that uses a pair of Doppler radars to measure upper-body kinematics (velocity, direction of motion, amount of motion) and a grid of piezoelectric wires hidden under a 6 x 10 foot carpet to monitor dynamic foot position and pressure. This system has been used in an audio installation, where users launch and modify complex musical sounds and sequences as they wander about the carpet. This paper describes the floor and radar systems, quantifies their performance, and outlines the musical application.

Electronic money: toward a virtual wallet

Music synthesizers and computers can produce almost any sound imaginable, but for a long while only keyboardists could directly control their expressiveness. But now a new breed of digital controllers-some of which trace their roots to the turn of the century-lets you fiddle, drum, blow, or even dance your way into electronic soundscapes. The author discusses electronic keyboards, percussion interfaces, stringed instruments, interfaces for wind instruments, and noncontact interfaces. The the on-line version of IEEE Spectrum boasts over 20 video and sound files from around the world, displaying the controllers in use. It even includes a Web page where any number of people on the Internet can make music (of a sort) at the same time.