Every day of your computing life, you reach out for the mouse whenever
you want to move the cursor or activate something. The mouse senses
your motion and your clicks and sends them to the computer so it can
respond appropriately. An ordinary mouse detects motion in the X and Y
plane and acts as a two dimensional controller. It is not well suited
for people to use in a 3D graphics environment. Space Mouse is a
professional 3D controller specifically designed for manipulating
objects in a 3D environment. It permits the simultaneous control of all
six degrees of freedom - translation rotation or a combination. . The
device serves as an intuitive man-machine interface
The predecessor of the spacemouse was the DLR
controller ball. Spacemouse has its origins in the late seventies when
the DLR (German Aerospace Research Establishment) started research in
its robotics and system dynamics division on devices with six degrees
of freedom (6 dof) for controlling robot grippers in Cartesian space.
The basic principle behind its construction is mechatronics engineering
and the multisensory concept. The spacemouse has different modes of
operation in which it can also be used as a two-dimensional mouse.
How does computer mouse work?
Mice first broke onto the public stage with the introduction of the
Apple Macintosh in 1984, and since then they have helped to completely
redefine the way we use computers. Every day of your computing life,
you reach out for your mouse whenever you want to move your cursor or
activate something. Your mouse senses your motion and your clicks and
sends them to the computer so it can respond appropriately
2.1 Inside a Mouse
The main goal of any mouse is to translate the motion of your hand into
signals that the computer can use. Almost all mice today do the
translation using five components:
Fig.1 The guts of a mouse
1. A ball inside the mouse touches the desktop and rolls when the
The underside of the mouse's logic board: The exposed portion of the
ball touches the desktop.
2. Two rollers inside the mouse touch the ball. One of the rollers
is oriented so that it detects motion in the X direction, and the other
is oriented 90 degrees to the first roller so it detects motion in the
Y direction. When the ball rotates, one or both of these rollers rotate
as well. The following image shows the two white rollers on this mouse:
Fig.3 The rollers that touch the ball and detect X and Y motion
3. The rollers each connect to a shaft, and the shaft spins a disk
with holes in it. When a roller rolls, its shaft and disk spin. The
following image shows the disk:
Fig.4 A typical optical encoding disk: This disk has 36 holes around
its outer edge.
4. On either side of the disk there is an infrared LED and an
infrared sensor. The holes in the disk break the beam of light coming
from the LED so that the infrared sensor sees pulses of light. The rate
of the pulsing is directly related to the speed of the mouse and the
distance it travels.
Fig.5 A close-up of one of the optical encoders that track mouse
motion: There is an infrared LED (clear) on one side of the disk and an
infrared sensor (red) on the other.
5. An on-board processor chip reads the pulses from the infrared
sensors and turns them into binary data that the computer can
understand. The chip sends the binary data to the computer through the
Fig 6 The logic section of a mouse is dominated by an encoder chip, a
small processor that reads the pulses coming from the infrared sensors
and turns them into bytes sent to the computer. You can also see the
two buttons that detect clicks (on either side of the wire connector).
In this optomechanical arrangement, the disk moves
mechanically, and an optical system counts pulses of light. On this
mouse, the ball is 21 mm in diameter. The roller is 7 mm in diameter.
The encoding disk has 36 holes. So if the mouse moves 25.4 mm (1 inch),
the encoder chip detects 41 pulses of light.
Each encoder disk has two infrared LEDs and two infrared
sensors, one on each side of the disk (so there are four LED/sensor
pairs inside a mouse). This arrangement allows the processor to detect
the disk's direction of rotation. There is a piece of plastic with a
small, precisely located hole that sits between the encoder disk and
each infrared sensor. This piece of plastic provides a window through
which the infrared sensor can "see." The window on one side of the disk
is located slightly higher than it is on the other -- one-half the
height of one of the holes in the encoder disk, to be exact. That
difference causes the two infrared sensors to see pulses of light at
slightly different times. There are times when one of the sensors will
see a pulse of light when the other does not, and vice versa.
3.1 What is Mechatronics engineering?
Mechatronics is concerned with the design automation and operational
performance of electromechanical systems. Mechatronics engineering is
nothing new; it is simply the applications of latest techniques in
precision mechanical engineering, electronic and computer control,
computing systems and sensor and actuator technology to design improved
products and processes.
The basic idea of Mechatronics engineering is to apply innovative
controls to extract new level of performance from a mechanical device.
It means using modem cost effective technology to improve product and
process performance, adaptability and flexibility.
Mechatronics covers a wide range of application areas including
consumer product design, instrumentation, manufacturing methods,
computer integration and process and device control. A typical
Mechatronic system picks up signals processes them and generates forces
and motion as an output. In effect mechanical systems are extended and
integrated with sensors (to know where things are), microprocessors (to
work out what to do), and controllers (to perform the required
The word Mechatronics came up describing this fact of having technical
systems operating mechanically with respect to some kernel functions
but with more or less electronics supporting the mechanical parts
decisively. Thus we can say that Mechatronics is a blending of
Electronics engineering and Computing
These three disciplines are linked together with knowledge of
management, manufacturing and marketing.
3.2 What do Mechatronics engineers do?
Mechatronics design covers a wide variety of applications from the
physical integration and miniaturization of electronic controllers with
mechanical systems to the control of hydraulically powered robots in
manufacturing and assembling factories.
Computer disk drives are one example of the successful application of
Mechatronics engineering as they are required to provide very fast
access precise positioning and robustness against various disturbances.
An intelligent window shade that opens and closes according to the
amount of sun exposure is another example of a Mechatronics
Mechatronics engineering may be involved in the design of equipments
and robots for under water or mining exploration as an alternative to
using human beings where this may be dangerous. In fact Mechatronics
engineers can be found working in a range of industries and project
Â¢ Design of data collection, instrumentation and computerized
Â¢ Intelligent product design for example smart cars and
automation for household transportation and industrial application.
Â¢ Design of self-diagnostic machines, which fix problems on their
Â¢ Medical devices such as life supporting systems, scanners and
DNA sequencing automation.
Â¢ Robotics and space exploration equipments.
Â¢ Smart domestic consumer goods
Â¢ Computer peripherals.
Â¢ Security systems.
3.3 Mechatronic goals
3.3.1 The multisensory concept
The aim was to design a new generation of multi sensory lightweight
robots. The new sensor and actuator generation does not only show up a
high degree of electronic and processor integration but also fully
modular hardware and software structures. Analog conditioning, power
supply and digital pre-processing are typical subsystems modules of
this kind. The 20khz lines connecting all sensor and actuator systems
in a galvanically decoupled way and high speed optical serial data bus
(SERCOS) are the typical examples of multi sensory and multi actuator
concept for the new generation robot envisioned.
The main sensory developments finished with these criteria have been in
the last years: optically measuring force-torque-sensor for assembly
operations. In a more compact form these sensory systems were
integrated inside plastic hollow balls, thus generating 6-degree of
freedom hand controllers (the DLR control balls). The SPACE-MOUSE is
the most recent product based on these ideas.
Â¢ stiff strain-gauge based 6 component force-torque-sensor
Â¢ miniaturized triangulation based laser range finders.
Â¢ integrated inductive joint-torque-sensor for light-weight-
In order to demonstrate the multi sensory design concept, these types
of sensors have been integrated into the multi sensory DLR-gripper,
which contains 15 sensory components and to our knowledge it is the
most complex robot gripper built so far (more than 1000 miniaturized
electronic and about 400 mechanical components). It has become a
central element of the ROTEX space robot experiment.
Spacemouse is developed by the DLR institute of robotics and
DLR- Deutsches Zenturum far Luft-und Raumfahrt
4.1 Why 3D motion?
In every area of technology, one can find automata and systems
controllable up to six degrees of freedom- three translational and
three rotational. Industrial robots made up the most prominent category
needing six degrees of freedom by maneuvering six joints to reach any
point in their working space with a desired orientation. Even broader
there have been a dramatic explosion in the growth of 3D computer
Already in the early eighties, the first wire frame models of volume
objects could move smoothly and interactively using so called knob-
boxes on the fastest graphics machines available. A separate button
controlled each of the six degrees of freedom. Next, graphics systems
on the market allowed manipulation of shaded volume models smoothly,
i.e. rotate, zoom and shift them and thus look at them from any viewing
angle and position. The scenes become more and more complex; e.g. with
a "reality engine" the mirror effects on volume car bodies are updated
several times per second - a task that needed hours on main frame
computers a couple of years ago.
Parallel to the rapid graphics development, we observed a clear trend
in the field of mechanical design towards constructing and modeling new
parts in a 3D environment and transferring the resulting programs to NC
machines. The machines are able to work in 5 or 6 degrees of freedom
(dot). Thus, it is no surprise that in the last few years, there are
increasing demands for comfortable 3D control and manipulation devices
for these kinds of systems. Despite breathtaking advancements in
digital technology it turned out that digital man- machine interfaces
like keyboards are not well suited for people to use as our sensomotory
reactions and behaviors are and will remain analogous forever.
4.2 DLR control ball, Magellan's predecessor
At the end of the seventies, the DLR (German Aerospace Research
Establishment) institute for robotics and system dynamics started
research on devices for the 6-dof control of robot grippers .in
Cartesian space. After lengthy experiments it turned out around 1981
that integrating a six axis force torque sensor (3 force, 3 torque
components) into a plastic hollow ball was the optimal solution. Such a
ball registered the linear and rotational displacements as generated by
the forces/ torques of a human hand, which were then computationally
transformed into translational / rotational motion speeds.
The first force torque sensor used was based upon strain gauge
technology, integrated into a plastic hollow ball. DLR had the basic
concept centre of a hollow ball handle approximately coinciding with
the measuring centre of an integrated 6 dof force / torque sensor
patented in Europe and US.
From 1982-1985, the first prototype applications showed that
DLR's control ball was not only excellently suited as a control device
for robots, but also for the first 3D-graphics system that came onto
the market at that time. Wide commercial distribution was prevented by
the high sales price of about $8,000 per unit. It took until 1985 for
the DLR's developer group to succeed in designing a much cheaper
optical measuring system.
4.2.1 Basic principle
The new system used 6 one-dimensional position detectors. This system
received a worldwide patent. The basic principle is as follows. The
measuring system consists of an inner and an outer part. The measuring
arrangement in the inner ring is composed of the LED, a slit and
perpendicular to the slit on the opposite side of the ring a linear
position sensitive detector (PSD). The slit / LED combination is mobile
against the remaining system. Six such systems (rotated by 60 degrees
each) are mounted in a plane, whereby the slits alternatively are
vertical and parallel to the plane. The ring with PSD's is fixed inside
the outer part and connected via springs with the LED-slit-basis. The
springs bring the inner part back to a neutral position when no forces
/ torque are exerted: There is a particularly simple and unique. This
measuring system is drift-free and not subject to aging effects.
The whole electronics including computational processing on a one-chip
-processor was already integrable into the ball by means of two small
double sided surface mount device (SMD) boards, the manufacturing costs
were reduced to below $1,000, but the sales price still hovered in the
area of $3,000.
The original hopes of the developers group that the license companies
might be able to redevelop devices towards much lower manufacturing
costs did not materialize. On the other hand, with passing of time,
other technologically comparable ball systems appeared on the market
especially in USA. They differed only in the type of measuring system.
Around 1990, terms like cyberspace and virtual reality became popular.
However, the effort required to steer oneself around in a virtual world
using helmet and glove tires one out quickly. Movements were measured
by electromagnetic or ultrasonic means, with the human head having
problems in controlling translational speeds. In addition, moving the
hand around in free space leads to fairly fast fatigue. Thus a redesign
of the ball idea seemed urgent.
4.3 Magellan (the European Spacemouse):
the result of a long development chain
With the developments explained in the previous sections, DLR's
development group started a transfer company, SPACE CONTROL and
addressed a clear goal: To redesign the control ball idea with its
unsurpassed opto electronic measuring system and optimize it thus that
to reduce manufacturing costs to a fraction of its previous amount and
thus allow it to approach the pricing level of high quality PC mouse at
The new manipulation device would also be able to function as a
conventional mouse and appear like one, yet maintain its versatility in
a real workstation design environment. The result of an intense one-
year's work was the European SpaceMouse, in the USA it is especially in
the European market place. But end of 93, DLR and SPACE CONTROL jointly
approached LOGITECH because of their wide expertise with pointing
devices for computers to market and sell Magellan in USA and Asia. The
wear resistant and drift free opto electronic, 6 component measuring
system was optimized to place all the electronics, including the
analogous signal processing, AT conversion, computational evaluation
and power supply on only one side of a tiny SMD- board inside
Magellan's handling cap. It only needs a few milliamperes of current
supplied through the serial port of any PC or standard mouse interface.
It does not need a dedicated power supply. The electronic circuitry
using a lot of time multiplex technology was simplified by a factor of
five, compared to the former control balls mentioned before. The
unbelievably tedious mechanical optimization, where the simple
adjustment of the PSD's with respect to the slits played a central role
in its construction, finally led to 3 simple injection moulding parts,
namely the basic housing, a cap handle with the measuring system inside
and the small nine button keyboard system. The housing, a punched steel
plate provides Magellan with the necessary weight for stability; any
kind of metal cutting was avoided. The small board inside the cap
(including a beeper) takes diverse mechanical functions as well. For
example, it contains the automatically mountable springs as well as
overload protection. The springs were optimized in the measuring system
so that they no longer show hysteresis; nevertheless different
stiffness of the cap are realizable by selection of appropriate
springs. Ergonomically, Magellan was constructed as flat as can be so
that the human hand may rest on it without fatigue. Slight pressures of
the fingers on the cap of Magellan is sufficient for generating
deflections in X, Y, and Z planes, thus shifting a cursor or flying a
3D graphics object translationally through space. Slight twists of the
cap cause rotational motions of a 3D graphics object around the
corresponding axes. Pulling the cap in the Z direction corresponds to
zooming function. Moving the cap in X or Y direction drags the
horizontally and vertically respectively on the screen. Twisting the
cap over one of the main axes or any combination of them rotates the
object over the corresponding axis on the screen. The user can handle
the object on the screen a he were holding it in his own left hand
and helping the right hand to undertake the constructive actions on
specific points lines or surfaces or simply by unconsciously bringing
to the front of appropriate perspective view of any necessary detail of
the object. With the integration of nine additional key buttons any
macro functions can be mapped onto one of the keys thus allowing the
user most frequent function to be called by a slight finger touch from
the left hand. The device has special features like dominant mode. It
uses those degrees of freedom in which the greatest magnitude is
generated. So defined movements can be created. Connection to the
computer is through a 3m cable (DB9 female) and platform adapter if
necessary. Use of handshake signals (RTSSCTS) are recommended for the
safe operation of the spacemouse. Without these handshake signals loss
of data may occur. Additional signal lines are provided to power the
Magellan (DTS&RTS). Thus, no additional power supply is needed. Flying
an object in 6 dof is done intuitively without any strain. In a similar
way, flying oneself through a virtual world is just fun. Touching the
keys results in either the usual menu selection, mode selection or the
pickup of 3D objects.
Table-1 Technical specifications of spacemouse
MAGELLAN: FEATURES AND BENEFITS
Â¢ Ease of use of manipulating objects in 3D applications.
Â¢ Calibration free sensor technology for high precision and
Â¢ Nine programmable buttons to customize users preference for
Â¢ Fingertip operation for maximum precision and performance.
Â¢ Settings to adjust sensitivity and motion control to the users
Â¢ Small form factor frees up the desk space.
Â¢ Double productivity of object manipulation in 3D applications.
Â¢ Natural hand position (resting on table) eliminates fatigue.
As the user positions the 3D objects with the Magellan device the
necessity of going back and forth to the menu is eliminated. Drawing
times is reduced by 20%-30% increasing overall productivity. With the
Magellan device improved design comprehension is possible and earlier
detection of design errors contributing faster time to market and cost
savings in the design process. Any computer whose graphics power allows
to update at least 5 frames per second of the designed scenery, and
which has a standard RS232 interface, can make use of the full
potential of Magellan spacemouse. In 3D applications Magellan is used
in conjunction with a 2D mouse. The user positions an object with
spacemouse while working on the object using a mouse. We can consider
it as a workman holding an object in his left hand and working on it
with a tool in his right hand. Now Magellan spacemouse is becoming
something for standard input device for interactive motion control of
3D graphics objects in its working environment and for many other
FUTURE SCOPE AND CONCLUSION
6.1 FUTURE SCOPE
Magellan's predecessor, DLR's control ball, was a key element of the
first real robot inspace, ROTEX- (3), which was launched in April 93
with space shuttle COLUMBIA inside a rack of the spacelab-D2. The robot
was directly teleoperated by the astronauts using the control ball, the
same way remotely controlled from ground (on-line and off line)
implying "predictive" stereographics. As an example, the ground
operator with one of the two balls or Magellans steered the robot's
gripper in the graphics presimulation, while with the second device he
was able to move the whole scenery around smoothly in 6 dot Predictive
graphics simulation together with the above mentioned man machine
interaction allowed for the compensation of overall signal delays up to
seven seconds, the most spectacular accomplishment being the grasping
of a floating object in space from the ground. Since then, ROTEX has
often been declared as the first real "virtual reality" application.
6.1.1 VISUAL SPACEMOUSE
A most intuitive controlling device would be a system that
can be instructed by watching and imitating the human user, using the
hand as the major controlling element. This would be a very comfortable
interface that allows the user to move a robot system in the most
natural way. This is called the visual space mouse. The system of the
visual space mouse can be divided into two main parts: image processing
and robot control. The role of image processing is to perform
operations on a video signal, received by a video camera, to extract
desired information out of the video signal. The role of robot control
is to transform electronic commands into movements of the manipulator.
The graphics simulation and manipulation of 3D volume objects and
virtual worlds and their combination e.g. with real information as
contained in TV images (multi-media) is not only meaningful for space
technology, but will strongly change the whole world of manufacturing
and construction technology, including other areas like urban
development, chemistry, biology, and entertainment. For all these
applications we believe there is no other man- machine interface
technology comparable to Magellan in its simplicity and yet high
precision. It is used for 3D manipulations in 6 dof, but at the same
time may function as a conventional 2D mouse.
(1) J. HeintB, G. Hilzinger
Device for programming movements of a Robot, Enrop. Patent No.
0.108.348; US-Patent No. 4,589,810
(2) J. Dietrich, G. Plank, H. Krans
Optoelectronic System Housed in Plastic Sphere,
Emop. Patent No. 0 240 023; US-Patent No. 4,785,180; JP-Patent No. 1763
(3) G. Hirzmger and J. Dietrich, B. Gombert, J. Heindi, K. Landzettel,
The sensory and telerobotic aspects of the spare robot technology
Int. Symposium "Artificial Intelligence, Robotics and Automation, in
Toulouse Labege, France, Sept. 30 - Oct. 2, 1992.
Space mouse opens a new age for man-machine communication. This
device is based on the technology used to control the first robot in
space and has been adapted for a wide range of tasks including
mechanical design, real time video animation and visual simulation. It
has become a standard input device for interactive motion control of
three-dimensional graphic objects in up to six degrees of freedom.
Space mouse works with standard serial mouse interface without an
additional power supply. The ergonomic design allows the human hand to
rest on it without fatigue. Thus flying an object in six degrees of
freedom is done without any strain.
I express my sincere thanks to Prof. M.N Agnisarman Namboothiri (Head
of the Department, Computer Science and Engineering, MESCE), Mr.
Sminesh (Staff incharge) for their kind co-operation for presenting the
I also extend my sincere thanks to all other members of the faculty of
Computer Science and Engineering Department and my friends for their
co-operation and encouragement.
CHAPTER 1 INTRODUCTION
CHAPTER 2 HOW DOES COMPUTER MOUSE WORK?
2.1 INSIDE A MOUSE
CHAPTER 3 MECHATRONICS
3.1 WHAT IS MECHATRONICS ENGINEERING
3.2 WHAT DO MECHATRONICS ENGINEERS DO?
3.3 MECHATRONICS GOALS 8
3.3.1 MULTISENSORY CONCEPT
CHAPTER 4 SPACE MOUSE
4.1 WHY 3D MOTION
4.2 DLR CONTROL BALL 10
4.2.1 BASIC PRINCIPLE 10
4.3. MAGELLAN: SPACE MOUSE
CHAPTER 5 MAGELLAN: FEATURES AND BENEFITS
CHAPTER 6 FUTURE SCOPE AND CONCLUSION
6.1 FUTURE SCOPE
6.1.1 VISUAL SPACE MOUSE
6.2 CONCLUSION 17