A study of spiders

The decision of copying spiders in the physical design of the robot has spawned some extra focus to the project.

Here are some you-tube videos showing spiders moving in slow motion:


And here a study of the degrees of freedom found in the legs of a spider, summarized elegantly in the two shamelessly borrowed figures below:

Range of freedom in XZ plane (Z is up)

Range of freedom in XY plane (ground)


Cobalt blue tarantula

Lately I have pondered (in-between the bouts my extremely demanding and satisfying job) about how to model the physical layout of the robot.

I have proclaimed it to be a hexapod from the start. This idea seemed like the most logical at the time. 4 is too few and 8 is too many. Having an odd number of limbs leeds to more complex gaits. Also, keeping the number of movable parts per limb low would reduce the cost and complexity of each limb.

However now I am not so sure any more. I personally like spiders better than insects and spiders have 8 legs. Also, the number of moving parts per limb in a spider (and in insects too for that matter) is much higher than 3. Evolution is the best mechanism to achieve optimization there is, and it has been working for over 4 billion years to perfect the spiders we see today. It follows thusly that one would be unnecessarily stubborn/proud not to at least observe, analyse and learn from the way spiders are.

Anatomy of a spider, for study before deciding on the anatomy of a robot.

What's in a spider anyways?

So I decided  to go all in, and find the perfect spider species to use as a template for the design of the robot. I ended up with the cobalt blue tarantula as the best  candidate for the following reasons:

  • It is strikingly beautiful both in color and proportions. I firmly believe that aesthetics play a bigger role in design than merely pleasing one's eye.
  • It is not too specialized. Many spiders have specialized into niche markets that make them unfit as a model to a "general purpose" robot. It is a solitary hunter and so is my robot.
  • It has an well balanced anatomy that would be relatively easy to replicate.
  • It has a temper similar to that which I want to give the robot (shy but aggressive).