Otto it is a robot with legs proposed as an approach to bipedal robots. Otto, still having a very simple mechanical configuration, has the ability to perform many movements such as walking, show emotions or dance thanks to his pair of legs.

Normally, all text books dedicated to bipedal robots begin by praising the advantages that robots with legs can have with respect to robots moved by wheels or other rotating elements.

However, I would like to approach the subject from another point of view: the robots with legs are cool.

They are awesome! without giving it more laps, and how cool it is worth breaking your head with impossible mechanical configurations, horrible equations and frustrating results. They are not very grateful robots, their start-up is usually slow (and desolating), and it is rare that they work at the first attempt "like all robots". In general, these robots are a challenge for both engineers and fans of robotics.

Focusing on robots with two legs, that is bipeds; we can find countless concepts: from single bipeds with a single engine to humanoids with more than twenty joints.

A good biped robot must be able to modify the position of its mechanical elements, to dynamically move its center of gravity. In fact, this ability will be the most important ingredient when it comes to getting our robot to stand up. A robot in a static position will remain stable if the projection of its center of gravity on the horizontal surface is within the area bounded by the support points of the robot. In summary, for a robot to walk, it is necessary to be able to support its weight on one foot or another, at different moments of time.

When designing and building bipedal robots, a first option is robots with 2-3 degrees of freedom. If there is a father of this type of robot, that is David Buckley. In 1998 he built the BigFoot, a robot that with only two servos has the ability to move forward, backward and make turns.

In this video you can see how the robot balances the weight inclining of its own structure to rest on its feet alternately. However, there is another way to address the problem of weight sharing. There are designs that achieve this effect through the movement of a moving mass, as is the case of Archer by Kåre Halvorsen, or Dead Duck by Frits Lyneborg. The two robots have placed a heavy component on top. By laterally displacing this mass, they are able to place the robot's center of gravity on the support foot.

Going one step further, we enter the configuration of four joints. Normally, when four servos are used, they are distributed in two symmetrical pairs for each leg. These servos can be connected in both roll-yaw and yaw-roll configurations without noticeable differences in their control. One of the precursors of this type of biped was David Steadman with the Stead-e-Man. This configuration has inspired hundreds of bipedal robots, both commercial designs and open projects. There are even competitions designed for these robots, such as the TIROL-CHOCO Robot Competition, in Japan.

One of the most famous robots of this type is BoB, a small printable robot created by Kevin Biagini and released under the CC-BY-SA license.

This robot has served as inspiration for Otto's design. Otto has been completely designed in ThinkerCAD, Autodesk Fusion 60 and FreeCAD, with parts from some robots of the MYOD project and sized to house a Arduino nano shield plate and standard size servos. The Otto kinematic model corresponds to a yaw-roll arrangement, represented in the following scheme.

In the case of BoB, the axis of vertical rotation (yaw) was placed 5 mm furthermore, in BoB, this displacement limited the range of lateral roll (roll) to 45º. Otto has the ability to rotate the articulation 90º, or in other words, does not mechanically limit the movement of the servo and allows it to perform a full range of 180º. In addition, the fact of using servos of standard size with double brackets, with respect to BoB, that uses micro-servos with simple brackets; gives it a robustness and precision much higher in its movement.

Otto , having such a simple mechanical base, is offered as a starting point to learn how robots work with legs and experiment with different movements. In addition, it is an easily modifiable and derivable robot, with some modifications as nice as Jason Snow.

If you liked this post, I recommend you visit the Wikifactory of Otto , where you will find all the necessary sources to build it yourself, and you can add your own creation!