[info] [Boston-announce] Reminder: meeting *tomorrow* night

[Eugen Leitl]

----- Forwarded message from Brian Peltonen <brianp at livingplaysets.com> -----

From: Brian Peltonen <brianp at livingplaysets.com>
Date: Mon, 02 Jun 2008 16:37:57 -0400
To: boston-announce at greythumb.org
Subject: [Boston-announce] Reminder: meeting *tomorrow* night
User-Agent: Thunderbird 1.5.0.14ubu (X11/20080505)

Next Meeting
Tuesday, June 3rd, 2008, 7:00 PM
Featuring a presentation on "Biomemetic Robots" by Dr. Joseph Ayers

*** Please note, Grey Thumb will be meeting this month on Tuesday night. ***

Location
The Asgard Irish Pub at 350 Massachusetts Avenue in Cambridge, MA.

Abstract

We are developing biomimetic robots based on neurobiological model
systems, the lobster and the lamprey. These robots feature:

 A biomorphic plant engineered to capture the biomechanical advantages of
the animal model
 A neuronal network based controller.
 Myomorphic actuators that feature graded control.
 Neuromorphic Sensors that employ a labeled line code and
 A behavioral library based on command sequences reverse engineered from
movies of the animal model.

Existing implementations of these robots are based on finite state machine
based controllers that instantiate a set of finite state machines based on
the organizational principles of the animal model nervous systems. These
state machines include leg or body axis central pattern generators (CPGs)
that generate leg movements or undulations, postural pattern generators
that control compensatory appendages and/or adaptive sensors and sensory
integration networks that process sensor information. A hierarchical
command and coordination level that sequences behavior makes choices and
establishes the intersegmental coordination pattern of the locomotory CPGs
modulates the state machines.

Although these systems are quite effective in laboratory conditions their
effectiveness in unpredictable field environments degrades. We are
exploring two types of electronic neuron models in our controllers.
Hindmarsh-Rose (HR) electronic neurons are analog computers that simulate
the Hindmarsh Rose equations in real time. Discrete Time Map-based (DTM)
neurons are computationally efficient models based on a simple iterative
map. Chemical-based synapse models are present for both types of models
and allow the generation of realistic neuronal circuits. The key feature
of these models is that because they are based on capturing of nonlinear
dynamical behavior of neurons rather than neuronal conductance models,
they are simpler, can operate in real time and are thus suitable for
robotic control applications.

The ENS systems can be interfaced directly to actuators by using the EN
action potentials to gate power transistors supplying current to SMA
actuators. We have implemented both HR and DTM CPGs for the Lobster robot.
The HR CPG has been used to control a SMA based walking leg to walk in
different directions. By directing proprioceptive sensor feedback to the
neuronal oscillator elements of the CPG, we have been able to instantiate
proprioceptive leg reflexes for load compensation as well as reversing
reflexes for stumbling and limb contact.

We have performed detailed modeling of the exteroceptive control of
rheotaxic behavior mediated by antennal sensors. Surge and flow is
detected by strain gauges embedded in the antenna that are bent by flow.
The sensory input is processed by two layers of interneurons that
distinguish lateral versus axial flow and activate walking command systems
to mediate rotational and yawing components of rheotaxis. A separate
optical flow layer can fuse with this hydrodynamic flow to provide more
robust modulation.

We are also developing an ENS for the control of swimming in the lamprey
robot. This controller uses concatenated segmental CPGs to generate
propagating axial flexions. A layered control system includes, CPGs,
recruiters, coordinating elements, command elements, modulatory
interneurons as well as an inclinometer-based “vestibular” system for the
control of pitch and roll.

Joseph Ayers is a professor of biology at Northeastern University.

Grey Thumb is inspired by the Homebrew Computer Club and by Make magazine,
but is geared mostly toward artificial life, agent based simulation, and
evolutionary computation. Our goal is to bring together people from
diverse backgrounds to help create a nucleus of interest in these subjects
in the Boston area. (http://www.greythumb.org)


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----- End forwarded message -----
-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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