Structure of the Simulation Environment


-- Conception of the Training System --

The Karlsruhe Endoscopic Surgery Trainer is based on the following concept of an endoscopic simulation environment.

The basic structure is called a 'man-in-the-loop'-simulation because the control loop is closed by the human who acts as user or trainee. The system is divided in two parts: the real world which represents the user's immediate environment, and the so called virtual world created by the simulation with hardware, software and data. Goal is to provide a very realistic impression, the user must feel like in his usual environment and work in his normal way.

'Man-in-the-loop' - simulation (JPEG 96 kB)

As a surgeon-computer interface, a 'Phantom Box' is used as an artificial cavity together with the correct instrument set, maintaining the realistic environment of a laparoscopic operation. Inside the box, FZK designed and manufactured mechanical guidance systems are used for each instrument and the camera. An electrical tracking system aquires the relative joint positions by potientometers hinged to all internal instrument degrees of freedom. Additionally, several foot switches are implemented providing surgical (coagulation) and general functions (change of instruments, reset of scenario).

Training setup for laparoscopic operations (JPEG 56 kB)

User interace with endoscopic camera and original instruments (JPEG 54 kB)

Instrument guidance and tracking system (JPEG 16 kB)

The trainee surgeon manipulates the instruments and the camera in the normal way, and in our case the movements are converted to digital data by means of a PC-based measurement system. The PC provides 48 analog 12-Bit input channels and 32-Bit digital input. On request of the graphical workstation, the signals are submitted via asynchronous RS-232 Interface with 38400 Bits/s. The maximum response time delay for acquisition and transmission of one data block is less than 50 ms.

The design concept of the 'Karlsruhe Endoscopic Surgery Trainer' takes into account the kinematics of conventional endoscopic handling with four degrees of freedom. Furthermore it allows for future extension of the training interface with dexterous instruments with 6 or more joints, i.e. kinematically redundant mechanics.

Structure of the Training Environment (JPEG 165 kB)

The basic hardware system is a high-performance graphics workstation, in our case a SILICON GRAPHICS 'Onyx' with RE2 graphics subsystem and 2 processors (MIPS 4400, 200MHz). The simulation system 'KISMET' is used as core software, extended for 'deformable objects' and interactive object manipulation. The software package KISMET is under development at Forschungszentrum Karlsruhe (FZK) since 1986, primary for support of numerous robotics and teleoperation applications during equipment design, task planning, training and execution. KISMET is based on topological, geometrical, kinematical and dynamical models of the working environment and the handling tools.

For modelling and realistic simulation in medical applications, following data is required:

model-database
defines the geometrical shapes and the physical/mechanical properties of the tissues, organs and vessels as well as the geometry and kinematics of the instruments
knowledge-base
specifies the interaction behaviour and the handling of the model manipulation

As additional part of the man-machine communication, a graphical user interface is implemented. KISMET does all the necessary calculations in realtime and generates the virtual endoscopic view of the operation area, which is in reality provided by the endoscopic camera.

Training Environment in Use (JPEG 68 kB)


Back to page 'Karlsruhe Endoscopic Surgery Trainer'
This page is maintained by Christian Kuhn, FZK/IAI-SK
E-Mail: kuhn@iai.fzk.de
Last modification: January 17, 1997.