Rhexalion - Alternated Tripod Walk implementation on a Four Wheel/Legs Bio-Inspired Robot

In this post, we would like to share some information about another conceptual robot prototype that we are building and testing for different purposes, one of those purposes would be a "Plan B" in case something goes terrible wrong with our Dandelion design...But even if this new robot is not use it in our next Space Mission to the Moon, there are a lot of potential features and applications that we can apply to this robot here on Earth and even may be in future Space missions...

We call this robot "Rhexalion", because is kind of a mix between "RHex" from Boston Dynamics and our Dandelion design (as a joke we say here that is the result of a drinking night between RHex and Dandelion :-) ...

In this adaptation, our goal is to implement the "Alternate Tripod Walking" that we can find in several insects and that is implemented by RHex with 6 Wheels/Legs, but in this case with just 4 Wheels/Legs, reducing size, weight, power consumption and reduce risk of mechanics failure due to minor amount of mechanical and moving parts...

Here is how the adaptation looks:

The robot is implemented with 4 Stepper Motors of High Torque, an on-board full x86 computer with WiFi (Roboard RB-110), a Sparkfun QueadStepper controller and some sensors...

Here is the explode view of all components:

Here is how it looks after the implementation:

One of the more complicate things was the proper construction and calculations for the motors and the blades. After all, the blade manufacturing was implemented by a pretty smart approach using simple PVC tubes...but we are not going to tell you all the secrets ;-)

To implement the Alternate Tripod Walk in a 4 Wheel/Legs you must synchronize the movement of the Wheels. First, each wheel need 4 blades instead of just the One that we can see on the RHex original design, this is becouse we have less number motors and for that less legs in each corner. Next we need to simple move each motor 45°, the trick is how to initially positioning the blades on the wheels.

On the next picture you can see how the both tripods are formed, in each one both motors at the front rotates exactly 45° to position the next blade on the ground. On the blades in the back part of the robot, one is initially set to allow a blade to touch the ground and the other back motor in a "intermediate" position without any blade touching the ground and forming one of the tripods...Then the same pattern is repeated but this time with the opposite motor with a blade touching the ground and the other in a intermediate position, alternating the tripod formed.   

This walking patter, with a flexible material for the blades, allow a pretty strong and smooth movement for the robot that can travel a wide range of surface, pretty much as the insect since its implement in a engineering way, the abstract concept of the insect walk.

 Here is our little Rhexalion on a flat surface...

 Here is on grass...

On mud...

 On a raw terrain..

 This one is on a really extreme terrain with a slope of about 45°.

 In this picture Rhexalion is coming out of a big whole...

 Here is climbing big rocks..

And finally on small rocks...

As you can see it can cover a big wide range of raw and extreme surfaces, here a couple of videos showing it in action:

Hope you enjoy it...Cheers!