Space Mouse

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

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:

SPACEMOUSE

Spacemouse is developed by the DLR institute of robotics and mechatronics.

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 graphics.

 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.

Details Via:seminarsonly.com