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Mobile Robots as Research Tools

The K-Robot Family

(Visitors since 24 July 1996)

 

Motivation and Concept

The K-Robot Family

The Khepera Mobile Robot

The Koala Mobile Robot

Research Methodology and Environment

 

Commercialisation of our Robots (K-Team SA)

International Contacts (Khepera and Koala Users)

Khepera Robot Contest

Motivation and Concept

Due to the fact that more and more people want to use mobile robots not only in robotics but also for research in artificial intelligence, production management, biology, cognitive sciences and other domains, new robots have to be developed to satisfy the following characteristics:

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  • Easy to install (plug and play)
  • Robust (no need of an electronic engineer to be consulted every week)
  • Easy to program (standard or graphical programming environments)
  • With a good computational power
  • Modular (flexible configuration)
  • Practical to use and ... not dangerous
  • Low cost (as cheap as possible ...)

The K-Family Robots (Khepera and Koala) are the result of this basic motivation and satisfy these constraints. The large number of actual users (more than 250 worldwide) and the diversity of their background (from biologists to mathematicians) proves that the effort was made in the right direction, giving to all these people the possibility to work on a real robot without being a robotician.

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The K-Robot Family

The K-Family Robots (Khepera and Koala) build a unique family of robots that make a smouth evolution from simulation to applications possible.

The three main steps of development of a mobile robotics application are covered by this unique family of robots.

• Simulation: As first step for the understanding of the basic mechanisms, simulation is the fastest and cheapest investigation method. This is valid only if this stage is followed by the experimentation on a real robot. A simulator of Khepera is available here.

   

• Desktop experiments: Khepera is well known for its size (55mm in diameter) and can be used near to the computer, on a normal desk. Its compact power allows an efficient experimentation using a real robot and applying the basic tools that are normally used for the simulation.

   

• Real world application: Koala is a "full" size mobile robot, but easy to use and "plug and play" like Khepera. Compatible with Khepera in software, hardware and concepts, it allows to bring to the "real world" the ideas developed on Khepera, using the last technology available.

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The Khepera Miniature Mobile Robot

The MINIATURISATION of Khepera makes it possible to have the power of a big robot on a normal desk close to the computer. The advantages given to the user are multiple:

• The environment is easy and cheap to build.
• The robot can be manipulated easily
• The connection with a computer can be made with an aerial cable without problems.
• Computer, robot and environment are on the same table, close to the user.
• The miniature robot is relatively much more robust than a big one. Imagine Khepera, 50 mm in diameter, running against a wall at a speed of 5o mm/s. Now compare it with a big robot, 1m in diameter, going against a wall at a speed of 1m/s ... Guess who`ll survive, the wall or the robot ?
• To ship or to take the robot to a conference won't be a problem anymore !

Technically, Khepera is a complete robot, with a lot of interesting characteristics.

To increase the functions of the basic version, several EXTENSION TURRETS can be plugged on the top of it.

On the picture above, you can see Khepera in a extended version (Gripper) grasping a small piece of sugar.

As reference for this work, please consider the following paper:

• F. Mondada, E. Franzi and P. Ienne, Mobile Robot Miniaturization: a Tool for Investigation in Control Algorithms, ISER'93, Kyoto, Japan, October 1993.

   

The full paper (PostScript, 9 pages, 334453 bytes) can be downloaded in PostScript format here.

• The General I/O turret makes simple extensions possible. Several inputs and outputs are available to the user to connect motors, sensors or any other device.

   

• The K213 Vision turret includes a linear pixel array to allow simple vision. A local processor on the turret manages the linear array and communicates with the main processor of Khepera.

   

• The K2D Video turret supports a black/white or color CCD camera. The video signal is not processed on board but is transmitted through the cable on the fixed computer.

   

• The Gripper turret makes object manipulation possible. Equipped with an arm with two degrees of freedom, Khepera can grasp, recognise and transport objects.

The Koala Mobile Robot

Koala is an application-oriented Khepera: Bigger than Khepera, more performant, open to real-size extensions, with more functionalities necessary to the realisation of real application (like the correct management of the battery charge), with 6 wheels for cross-country operation and a bodywork for good demonstrations. In addition to these new features, Koala keeps a shape and a structure compatible with Khepera, in such a way that experiments made on Khepera can be transposed to the Koala. The BIOS of both robots is compatible, so that programs written for one robot can be easely adapted (for some size parameters) and recompiled for the other one.

Extension modules are planned but not available yet. More informations here in the near future ...

As an example of a real application, this robot has been used for the test of a Vacuum Cleaner Robot.

Research Methodology and Environment

All the robots presented on this page are used in three main configurations:

1) The oldest and well known development methodology consists in building the binary code for the robot on a computer, transfer it to the robot and run it on the robot. A library of procedures is available to control the robot hardware: Wheel speed and position control, sensor reading, multitasking management and many other features are included in the BIOS of our robots and can be used from a C program.

This configuration has the advantage to allow the robot to run independently from the computer, but it has the disadvantage that the user has no access to the running code. This is very problematic for debugging the program and for the understanding of the tested control program. Note that only very few Khepera or Koala users work in this configuration.

2) Most of the actual users of these robots work by running the control program on their favourite computer (PC, SUN, MAC, SG, HP ...) in their favourite programming environment (C, C++, LISP, LabVIEW, PackLIB ...) by controlling the robot through a standard RS232 serial link. Khepera and Koala have a running mode called "SerCom", where all functionalities of the robot can be controlled with simple ASCII commands sent on the RS232 serial line. For instance, the command "D,5,3" sets the speed of the left wheel to 5 and the speed of the right wheel to 3 (the unit correspond to 8mm/s). When the robot receives the command, it executes it and answers with the acknowledge "d". In the same way, when the user send "E" on the serial line, the robot answer "e,2,3", where 2 and 3 are the measured speeds of the left and right wheel (in the example described, it means that the left wheel is blocked).

This configuration allows to split the control of the robot between the local processor placed on the robot and the host computer: The robot processor manages all strict real-time tasks (motor control, for instance) and the computer manages the task of higher level, which are the most interesting ones for the user. The fact to have this part of the control program on the computer allows an easier development (known environment and good debug tools) and a much better understanding of the system due to the possibility of a much better interaction (graphical representation, mouse and keyboard which are not on the robot).

3) When users start to understand their algorithms and want another kind of distribution of the tasks between robot and host computer (more treatment made at the level of the robot, for instance), they use a combination of the two previous methodologies, downloading some code that communicates with the host computer ... in the way and for the purpose they want to. This configuration is very powerful, but needs a good knowledge of the system.

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Homepages: Robots at LAMI - LAMI - DI - EPFL