Aim and Introduction

The mini humanoid, called Elvina(*), is a somewhat simplified, scaled model of a full-size humanoid with body dimensions that mirrors the dimensions of a human. It is a relatively cheap platform, primarely intended for doing research in humanoid robotics, and studying biped locomotion. Since it is small, cheap, and lightweight, the creation of multiple instances would well serve the purpose for studying multi-robot teams. Elvina is a fully autonomous robot with onboard power supply and computer. It is 28 cm tall and it weights about 1.5 kg including batteries. Each of the two legs has 5 degrees of freedom, of which 4 dof is active and 1 dof is passive. The head, the torso and the arms has 1 dof each, giving a total of 14 dof. The robot is equipped with a color camera, mounted in its head. The computer is attached to the back of the robot's body. The body also houses a near-infrared PSD (position sensitive detector) that is used to determine distances to nearby objects. In its present status, the robot is capable of static walking. Meet Elvinas twin brother ZORC, who lives in Dortmund, Germany! (*the robot was named Elvina by the childrens watching "Hjärnkontoret", which is a science tv program for kids.)

Experiments

An evolutionary experiment was conducted with Elvina, in order to optimize a previously by hand specified gait cycle. The onboard camera and distance sensor was used to obtain feedback to an evolutionary algorithm, which was used to optimize the robots gait. The outcome of the experiment was that the robot could walk in a straighter path than before, but not much faster.

Elvina is walking in a way that could best be described as a semi-static walk. During the gait cycle, the robot is statically supported by at least one leg an appreciable amount time. There are however dynamical phases in the gait cycle too, as when the supporting leg is changed from left to right, and from right to left. The picture to the left is showing exactly one gait cycle, starting with the lifting of the left leg, taking one step with it, lifting the right leg, taking one step with that leg, and ending up in the same position as before (but closer to the camera :)).

Construction

These pictures shows the robot in an incomplete stadium of its assembly. The robots actuators are 14 Hitec mini servos, mounted in a chassis/skeleton made of 6mm thick blank PVC panel. This is an excellent prototyping material for robotics. It is light weight yet strong and durable. It can be easily drilled, machined, or cut with most types of hand or power tools.

The height of the robot, when it is completed with camera and other stuff, will be approxemately 23 cm, and its weight is estimated to be around 1000g.

The EyeBot controller will be attached to the back of the robot and the batteries on its front (chest). This arrangement will keep the center of gravity in a position that assures good balancing.

Publications

• Wolff, K., and Nordin, P. (2002). "Evolution of Efficient Gait with an Autonomous Biped Robot using Visual Feedback." In van Amerongen, J., Jonker, J., Regtien, P., Stramigioli, S., editors, Proceedings of the 8th Mechatronics Forum International Conference 2002 (pp 504-513). June 24-26 2002, University of Twente, Enschede, Netherlands.
  
• Wolff, K., and Nordin, P. (2001). "Evolution of Efficient Gait with an Autonomous Biped Robot using Visual Feedback."
  In Late-Breaking Papers of the 2001 Genetic and Evolutionary Computation Conference, GECCO 2001. (pp. 482-489). San Francisco: Morgan Kaufmann Publishers, Inc.
  
• Ziegler, J., Wolff, K., Nordin, P., and Banzhaf, W. (2001). "Constructing a small humanoid walking robot as a platform for the genetic evolution of walking." In U. Rückert, J. Sitte and U. Witkowski, editors, Proceedings of the 5th International Heinz Nixdorf Symposium: Autonomous Minirobots for Research and Edutainment, AMiRE 2001 (pp. 51-59). Paderborn, Germany: Heinz Nixdorf Institute, University of Paderborn.

These papers can be downloaded from Krister Wolff's publications page.