Each leg touches the ground for about 1/4 of its rotation and it is in the air for the remaining 3/4 of the rotation. To keep itself stable the robot needs at least three legs on the ground at all times. So, we needed to make the 3/4 'air' portion happen in the same amount of time as the 1/4 'ground' portion. The only way to do that is have the ground portion slower than the air portion. That way three legs leave the ground at the same time the other three contact the ground.
That IS a constant speed, silly. The amount of time it takes for the thing to get back to the other side and in the air again depends on how flat the terrain is, so obviously there's no way to make it perfectly smooth.
The RHex in the video is actually going as fast as the motors will allow. These motors are geared down a fair amount so that they provide enough torque (or strength), but that comes at the expense of speed. We have been looking at a number of different motor technologies to use in the next version. Running also requires compliant, or flexible, legs; something that we are also looking into.
We would love to hear suggestions from viewers. If you have leg or motor ideas, please post a comment.
Would this work in run mode if there were only one motor on each side, running each three legs via gearing?
garagecrap 1 year ago
wouldn't it be faster to make the legs spin at a constant speed, instead of slowing down when it touches ground?
KrykoStorm 2 years ago
Good question.
Each leg touches the ground for about 1/4 of its rotation and it is in the air for the remaining 3/4 of the rotation. To keep itself stable the robot needs at least three legs on the ground at all times. So, we needed to make the 3/4 'air' portion happen in the same amount of time as the 1/4 'ground' portion. The only way to do that is have the ground portion slower than the air portion. That way three legs leave the ground at the same time the other three contact the ground.
CRRas01 2 years ago
That IS a constant speed, silly. The amount of time it takes for the thing to get back to the other side and in the air again depends on how flat the terrain is, so obviously there's no way to make it perfectly smooth.
N7a7v7i 2 years ago
Nice, but can this thing run,
like Boston's RHex?
Bonerdelli 2 years ago
The RHex in the video is actually going as fast as the motors will allow. These motors are geared down a fair amount so that they provide enough torque (or strength), but that comes at the expense of speed. We have been looking at a number of different motor technologies to use in the next version. Running also requires compliant, or flexible, legs; something that we are also looking into.
We would love to hear suggestions from viewers. If you have leg or motor ideas, please post a comment.
CRRas01 2 years ago
The legs should have multiple joints...
N7a7v7i 2 years ago
Comment removed
Bonerdelli 2 years ago
wow! really cool!
i wanna build one self
ratinoec 2 years ago
Rasmussens, they are everywhere!
spartonne 3 years ago
Great job Greg! That must have been a fun senior project.
bigatl22 3 years ago
great job on your senior project Greg! This looks like it kicked butt!
vizualgraphix 3 years ago