Space Mouse
INTRODUCTION
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.
Space 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 mouse moves.
Space Mouse
Fig 2
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.
Space Mouse
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
Space Mouse
them into binary data that the computer can understand. The chip sends the
binary data to the computer through the mouse's cord.
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
Space Mouse
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.


MECHATRONICS
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 actions).
Space Mouse
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 Mechanical engineering,
Electronics engineering and Computing
These three disciplines are linked together with knowledge of management,
manufacturing and marketing.
Space Mouse
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 application.
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 areas including
• Design of data collection, instrumentation and computerized machine tools.
• Intelligent product design for example smart cars and automation for
household transportation and industrial application.
• Design of self-diagnostic machines, which fix problems on their own.
• Medical devices such as life supporting systems, scanners and DNA
sequencing automation.
• Robotics and space exploration equipments.
• Smart domestic consumer goods
• Computer peripherals.
• Security systems.
Space Mouse
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.
• stiff strain-gauge based 6 component force-torque-sensor systems.
• miniaturized triangulation based laser range finders.
• integrated inductive joint-torque-sensor for light-weight-robot.
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.