ELCT 402 Project Description
ROBOFISH
Author: Roger Dougal
Date: 17 August 2011
Project Advisor/Sponsor: Dr. Dougal
Advisor/Sponsor Contact info: (email, phone)
OBJECTIVE
Develop electromagnetic-mechanical actuators and controls that permit a
segmented artificial fish skeleton to execute realistic swiming motions.
OVERVIEW
Researchers at the University of Glasgow (Scotland) have developed a robotic
fish that is propelled by servomotor actuators that pull on wire tendons to develop
swimming motions in a segmented fishlike underwater vehicle. The purpose of this
project is to improve the actuator design by using (gear-free?) permanent magnet
actuators that, ideally, have few or no other moving parts.
Fig 1. Robosalmon from Univ of Glasgow
[http://i.livescience.com/images/i/1123/original/061201_robo_salmon_01.jpg?1296070076]
REQUIREMENTS
The team shall develop a full set of technical requirements for a new product that
is an electronically actuated fish skeleton suitable as a platform for underwater sensors.
The requirements shall address at least: size, torque or force, range of motion, speed of
motion, control architecture, weight, and power demand.
Competing actuator concepts shall be developed and evaluated, based on merits,
to select a winning concept. At least one prototype of the winning configuration shall be
developed, tested, and characterized.
Electronic drive circuits shall produce controllable force/position trajectories at
each joint as specified by a central control process. System performance shall be
demonstrated, measured, and documented.
Measured performance shall include at least the following:

Maximum force or torque capability of each actuator exceeds
requirements

Accuracy and reproducibility of individual joint articulation in response to
command is within 10%.
ELCT 402 Project Description

Stretch goal: demonstrate actual swimming motions in a water bath
MID-PROJECT MILESTONE(S)
Mid-project milestones are independent and can be met individually.
1) One prototype joint/actuator that produces controllable forces of the right
general magnitude when driven by a bench power supply.
2) One power converter and controller that produces a controllable current so
that if it were connected to the actuator, it would produce a controllable
torque. Tracking current reference with bandwidth of at least 1 Hz.
3) Joint coordinator and communication system that issues motion commands to
each individual joint controller so as to synthesize a realistic swimming
motion. Demonstrate results of commands using some computing/graphics
tool.
4) One prototype robofish body mechanism (segmented) suitable for later
insertion of the actuator mechanisms.
PROJECT POINTERS
Several actuator types are possible. Immediately obvious ones fall into categories
of the “voice coil” and “d’arsenvol movement” . In a fixed magnetic field, force exerted
on a bundle of current carrying conductors is proportional to the magnitude of B, the
magnitude of the current, and the number of conductors.
Using conventional rotory motors, other possibilities include screw and nut
rotary-to-linear force converters, screw and sector gear, etc.
Consider use of standard serial communication bus such as I2C
See information on the Univ of Glasgow web site at:
http://www.realscience.org.uk/science-news-robosalmon.html
http://www.livescience.com/1179-robosalmon-spy-fish.html