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Mini
direct-drive robot
Abstract
The Minirobot
is a small-scale direct-drive robot designed for manipulating
small, delicate objects with high positioning precision and
accurate force control. Potential uses include biomedical applications
such as the probing of cells or the preparation of electrophoresis
gels in genetics research. Electronic testing applications such
as automated probing of microcircuits such as multi-chip modules
(MCM's) and high-density circuit boards is also being explored.
Finally, the small size & mass of the robot makes it attractive
for near-earth space applications such as experiment servicing
on the International Space Station.
Status
Description
Features
- 120 cm^3
work volume
- 6 micron
positioning repeatability
- 5 Degrees
of freedom
- 1 kHz
sampling rate
- 83 Hz
lowest mechanical resonance
- Direct
telemanipulation with force-feedback of objects smaller than
a grain of sand.
Mechanical
Design
Mark-I
Minirobot
The
Mark-I minirobot started its life in 1991 as a 3 degree-of-freedom
(DOF) mechanism designed by Pierre-Henry Marbot for his MSEE project.
A sketch of this design is shown on the right.
Mark-II Minirobot
The Mark-II minirobot was redesigned by Manuel Moreyra in 1993-94
as his MSME project. He added two orientation axes at the robot
end-effector, giving a total of 5 DOF to the Mark-II robot. The
picture at the top of this page shows this design.
Mark-III+ Minirobo
We are working on developing funding in conjunction with Boeing
Defense and Space as well as NASA to begin development of a Mark-III
minirobot during 1996. The primary goal is to increase the angular
range of the joints and thereby increase the robot's work volume.
A flight version of the robot for a Space-Shuttle or Space Station
experiment is also being considered.
Electronics
Design
Mark-I
Minirobot
The
Mark-I minirobot electronics was designed by Pierre-Henry Marbot
as part of his MSEE work and consisted of a breadboard with interface
circuitry for the robot position sensors, a linear power amplifier
for each joint, and an 8-bit microcontroller (68H11). The control
software was a basic joint-by-joint PID controller with trajectories
and commands originating from a remote PC/AT connected to the
serial port of the microcontroller.
Mark-II Minirobot
The Mark-II minirobot electronics was completely redesigned by
Steven Venema around a more powerful DSP-based controller board
based on the Texas Instruments TMS320C30 DSP chip. An interface
board handles all the analog signal conditioning for 4 analog
encoders, an LVDT sensor, and the power amplifiers; the power
amplifiers are mounted in a separate package. The DSP controller
is configured with 2 analog/digital I/O daughter cards for a total
of 8 analog inputs and 8 analog outputs as well as 32 digital
outputs and 16 digital inputs. The control software is written
in C and contains (at the lowest level) a per-joint PID control
loop running at 1kHz. Other software in the DSP handles trajectory
generation, kinematics, communications, etc.
Research
and Development Activities
Scaled
Teleoperation
The
minirobot has been used as the "slave" side of a bilateral teleoperation
system. In this system, the Pen-based
haptic display is used to control the robot's position. The
position error of the robot is feed back as a force to the operator
via the same haptic interface.
Telemanipulation
with Kinematic Redundancy
When only commanding 3 cartesian degrees of freedom (e.g., x-y-z
position), the minirobot's 5 DOF's affords 2 redundant degrees
of freedom. This configuration was used in research into optimizing
the use of redundancy for bilateral teleooperation tasks. Dal-Yeon
Hwang did the majority of this work.
Trajectory Optimization
The minirobot was used as a testbed for a trajectory optimization
routine developed by Frederik Boe in 1994 which optimizes the
speed of the robot for the different portions of a complex trajectory
using pre-specified error criteria and a multi-pass training session
for the given trajectory.
Online Sensor Calibration
The minirobot uses analog quadrature position encoders to sense
joint position. While this type of sensor allows extremely
fine position sensing, the encoder outputs must first be calibrated
for high-precision positioning. Steven Venema developed a technique
to calibrate these sensors online without requiring any external
position measurement references (e.g., laser interferometers).
Micro Manipulation
Pamela Bhatti developed a micro-tweezers gripper for the minirobot,
enabling it to manipulate objects about the size of a grain of
sand.
Circuit Probing
An electronic probe tip was developed for the minirobot and its
simple tests were made to evaluate this approach for testing high-density
printed circuit boards and multi-chip modules (MCM's).
Publications
(*)
(*)
Note: Most of the BRL
publications are available on-line in a PDF format.
You may used the publication's reference number as a link to the
individual manuscript.
[061]
P.H. Marbot, B. Hannaford,
'Mini Direct Drive Arm for Biomedical Applications,' Proceedings
of ICAR 91, pp. 859-864, Pisa Italy, June 1991.
[066]
P. Bhatti, P.H. Marbot, B. Hannaford,
'Microscopic Pick and Place with the Mini-Direct Drive Arm,'
SPIE Telemanipulation Symposium, Boston, November, 1992.
[084]
B. Hannaford, P.H. Marbot, M. Moreyra, S. Venema,
'A 5-Axis Mini Direct Drive Robot for Time Delayed Teleoperation,'
Proc. Intelligent Robots and Systems (IROS 94), vol. 1, pp.
555-562, Munich, Sept. 1994.
[090]
M. Moreyra, P.H. Marbot, S. Venema, B. Hannaford,
'A 5-Axis Mini Direct Drive Robot for Time Delayed Teleoperation
,' In "Intelligent Robots and Systems 1994", pp. 445-462,
V. Graefe, Ed., Elsevier Science, 1995.
[093]
B. Hannaford, P.H. Marbot, P. Buttolo, M. Moreyra, S. Venema,
'Scaling Properties of Direct Drive Serial Arms,' International
Journal of Robotics Research, vol. 15, pp. 459-472, 1996.
[097]
B. Hannaford, A.K. Bejczy, P. Buttolo, M. Moreyra, S. Venema,
'Mini-Teleoperation Technology for Space Research,' Procedings
International Symposium on Microsystems Intelligent Materials
and Robots (MIMR-95), pp. 524-527, Sendai, Japan, September, 1995.
[099]
S. Venema, B. Hannaford,
'Miniature Telerobots in Space Applications,' Proc. Int.
Conf. on Integrated Micro-Nanotechnology for Space Applications,
Houston Tx., October, 1995.
[103]
B. Hannaford, M.R. Moreyra, P.H. Marbot,
'Five axis direct-drive mini-robot having fifth actuator located
at a non-adjacent joint,' U.S. Patent #5,528,955, June 25,
1996 (issued).
[105]
D.Y. Hwang, B. Hannaford,
'Teleoperation Performance with a Kinematically Redundant Slave
Robot,' International Journal of Robotics Research, vol.
17, pp. 579-597, June, 1998.
[107]
B. Hannaford, J. Hewitt, T. Maneewarn, S. Venema, M. Appleby,
R. Ehresman,
'Telerobotic Remote Handling of Protein Crystals,' IEEE International
Conference on Robotics and Automation, Albuquerque, NM, April
1997.
[108]
B. Hannaford, J. Hewitt, T. Maneewarn, S. Venema, M. Appleby,
R. Ehresman,
'Telerobotic Macros for Remote Handling of Protein Crystals,'
Proceedings Intl. Conf. on Advanced Robotics, (ICAR97), Monterrey,
CA, July 1997.
[109]
F. Boe, B. Hannaford,
'On-line Improvement of Speed and Tracking Performance on Repetetive
Paths,' IEEE Transactions on Control Systems Technology,
vol. 6, pp. 350-358, May 1998.
[139]
S.C. Venema, B. Hannaford,
'Telerobotic Remote Handling of Protein Crystals via an Internet
Link ,' In "Beyond Webcams, An Introduction to Online Robots",
Roland Siegwart, Ed., MIT Press, Cambridge, MA, 2002.
[Th001]
P.H. Marbot,
'Mini Direct Drive Robot for Biomedical Applications,' MSEE
Thesis, University of Washington, Department of Electrical Engineering,
August, 1991.
[Th009]
M.R. Moreyra,
'Design of a Five Degree of Freedom Direct Drive Mini-Robot Using
Disk Drive Actuators,' MSME Thesis, University of Washington,
Department of Mechanical Engineering, June 1994.
[Th010]
S.C. Venema,
'A Kalman Filter Calibration Method for Analog Quadrature Position
Encoders,' MSEE Thesis, University of Washington, Department
of Electrical Engineering, June 1994.
[Th011]
F. Boe,
'An Iterative Trajectory Shaping Algorithm based on Run-Time Results,'
MSEE Thesis, University of Washington, Department of Electrical
Engineering, June 1994.
[Th015]
D.Y. Hwang,
'Teleoperation Performance with a Kinematically Redundant Slave
Robot,' Ph.D. Dissertation, University of Washington, Department
of Electrical Engineering, December 1995.
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