Original article date: September 1998
From an expensive prototype used in the Space Shuttle Columbia comes the affordable peripheral which is taking 3 CAD design by storm – presenting the Space Mouse.
Despite breathtaking advances in digital technology traditional man-machine interfaces such as the keyboard are not well suited for people to use in a 3D graphics environment.
But the Space Mouse is a professional 3D controller specifically designed for manipulating objects in a 3D CAD 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 normally to be used by the left hand and supporting its functions as a viewing or guidance hand while the right hand is released to concentrate only on the common construction functions with the help of the pointer mouse or tablet.
The result of years of development for man-machine communication in aerospace and robotic applications the predecessor of the European Space Mouse (known in the US and Asia as Magellan) was the DLR control ball used to control the first robot in space remotely. It flew in NASA’s Space Shuttle Columbia in 1993.
In fact Magellan 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. After lengthy experiments it turned out around 1981 that integrating a six-axis force-torque sensor (three force three 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 and torques of a human hand which were then transformed computationally into translational and rotational motions and speeds.
The first force-torque sensor used was based on strain gauge technology. Wide commercial distribution was prevented by the high price of about $8000 per unit. It took until 1985 for the DLR’s developer group to design a much cheaper optical measuring system based on six one-dimensional position detectors. 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 boards. The manufacturing costs were reduced to below $1000 but the sales price still hovered in the area of $3000. Only a few hundred were sold.
The original hopes of the developer group that license companies might be able to develop devices towards much lower manufacturing costs did not materialise. On the other hand with the passing of time other ball systems appeared on the market which differed in the type of measuring system.
DLR’s development group spun off a company called Space Control whose objectives were to redesign the control ball idea while retaining the opto-electronic measuring principle reducing manufacturing costs to a fraction of the previous amount so that it could approach the pricing level of high end PC devices. The new manipulation device should be able to function as a conventional mouse and appear like one yet maintain its versatility in a real workstation environment.
Ergonomically the mouse has a very flat and compact design allowing the palm of the hand to rest naturally on the device without fatigue leaving all the fingers free to interact with the mouse cap. This maximises the precision of movements in order to translate and rotate any object in the 3D CAD system screen.
Very slight pressure to push pull or twist the cap in any one or more of the six degrees of freedom is enough to move the object in the screen. Pulling the cap in the Z-direction corresponds to the zooming function pushing it distances the object relative to the viewer. Moving the cap in the X or Y directions drags the object horiizontally and vertically 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.
Within seconds of using the device the interaction with the cap becomes intuitive. This means that the user handles the object on the scren as if he were holding it in his own left hand observing or guiding it with high precision and helping the right hand to undertake the correct constructive actions on specific points lines or surfaces simply by unconsciously bringing to the front the appropriate perspective view of any necessary detail of the object. And with the integration of nine additional key buttins any macro function can be mapped onto one of the keys thus allowing the user most frequently used functions to be called by a slight finger touch from the left hand.
Now the European Space Mouse is becoming something of a standard input device for interactive motion control of 3D graphic objects in the Catia working environment and for many other applications. There are over 12 0 installations in Europe and US licensee Logitech aims to make it the world standard for 3 graphics interfaces. Silicon Graphics has integrated the interface driver into its new operating system and other leading CAD systems such as Pro/Engineer Ideas Solidworks and Cadds5 have dedicated Magellan drivers.
- Space Control
- Miguel G Leitmann
- 00 49 8105 3769 04