FIELD AND SPACE ROBOTICS LABORATORY

DEPARTMENT OF MECHANICAL ENGINEERING

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

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Fundamentals of Digital Mechatronics

Principal Investigator

Steven Dubowsky

Group Members

Lauren DeVita, MS student
Cristina Paul, visiting student
Jean-Sebastien Plante, PhD student

Collaborators

Prof. Sergio Pellegrino, Matthew Santer, and Tyge Schioler, Deployable Structures Lab, Cambridge University
Prof. Ferenc Jolesz, Harvard Medical School
Dan Kacher, Harvard Medical School

Overview

Digital Mechatronics and Binary Robotics is a motion control concept for robots and machines that consists of using numerous binary actuators in a structure.  Our goal is the development of both the fundamental design schemes for digital systems and the potential actuation mechanisms for such systems.  One important focus of this research is the field of dielectric elastomer actuation.

Objectives

  • Fundamental development of control strategy for binary systems
  • Design of binary systems for applications
  • Development of actuation technology appropriate for use in binary systems

Project Description

Digital systems use binary actuation to perform necessary tasks.  Each element has two potential states, and by choosing which state each element is in, desired positions and trajectories can be achieved.  Such digital machines could use hundreds or even thousands of binary actuators.  As the number of actuators is increased, the performance of the system approaches that of a continuous system.  The simulation below shows locomotion achieved with binary actuation.

Simulation of six legged walking rover traversing rough terrain
(Matt Lichter).  Each leg comprises 21 binary degrees-of-freedom.
Quicktime movie (5 MB)
High-quality AVI (13.7 MB)

wired_jan_2005.jpg (169143 bytes)

This research was highlighted in Wired Magazine
in January 2005 (click image to enlarge).

Currently we are investigating methods for achieving desired range and precision in the discrete work spaces of binary systems, such as in the figure below.

A 12-degree-of-freedom binary mechanism, with its
discrete workspace illustrated as a cloud of red points.

Current actuators like DC motors and pneumatic cylinders are too heavy, expensive, or complex for binary robotics, and therefore new actuator technologies are being developed.  An important focus of this research is Electrostrictive Polymer Artificial Muscles (EPAMs).  One such embodiment of the actuator is a flexible frame actuator shown below.  The actuator shown has expanded from 14 mm to 22 mm.  In other actuators, even larger strain rates (>200%) have been achieved.

A prototype EPAM, demonstrating its two binary configurations.

  

Recent prototypes (click to view movies: 1.9 and 2.6 MB AVI format).

These actuators have already shown promising results as binary actuators.  The video below shows 6 degree-of-freedom binary manipulator actuated by dielectric elastomer actuators.

 

(9.4 MB AVI)

Currently we are developing models for explaining the behavior of these actuators and optimizing their performance.  Various analytical and experimental studies are being done to evaluate their effectiveness as conventional actuators for use in digital systems or other scientific and commercial applications.  An example is the development of a hopping robot for micro-gravity environments.  Early prototypes have shown jumps of 10 cm under earth's gravity (see below).

(1.5 MB MPG)

Sponsors

  NASA Institute for Advanced Concepts (NIAC)

  The Cambridge-MIT Institute

  Center for Integration of Medicine & Innovative Technology (CIMIT)

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