Project Name :- HF15 Robot

Status:-  Declassified as of 01/10/2015

Department:- Helium Frog Robot Development Works - Area 13

HF15 Quadruped Robot

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A brief introduction

After completion of the hexapod robot I have always wanted to build one with less legs. This is more of a challenge as a 4 legged robot needs the centre of gravity to shift or at the very least be inside the three legs that remain on the floor. This time I felt that there was no need to reinvent the wheel, so I downloaded the excellent model by regishu from thingiverse .This was a great start, but I found some of the models were incorrect in small ways such as thread spacings and also translation from .stl files is never the best, so in the finish I redid them all on Catia so I had some decent models to work with modify. The firmware that regishu had developed was also a great help, but again there were a few things that I thought I could improve on.

Over the past few weeks I have been working on the design and I have managed to get the project working successfully. It's based on the MG90 servo version files from regishu.

As you can see I have again used a Dagu robot controller. The original design used an arduino Nano and a home made PCB, but to avoid this I added some spacers and mounted the larger board above the main chassis. This isn't as elegant as the initial design, but this is just a test bed and was the quickest way to achieve what I wanted. Of course I also added my customary "thimble boots" to the feet of the robot. I must say the regishu leg design is very good and the use of plastic pivots works really well and is much easier to print. This time I also used self tapping screws and this works so well that I will use them all the time when I can. They are strong and can also be dismantled easily without issue.

You can also see attached to the top of the main board is a lemon Rc radio reciever and I have the robot responding to commands from my 6 channel spectrum transmitter. So the robot is fully independant unlike the hexapod!

From the rear of the robot you can see the battery connection. Strapped underneath is a Floureon 2200mAh 11.1v 20C battery. This is quite large and never seems to go flat! I think the robot may be able to walk miles between a charge! I had this spare from some of my quadcopter adventures and it was the correct size to fit in the chassis. I also made a stand for the robot (Shown in orange) so I could develop the firmware. I found some errors in the original code, particularly when the robot turns on its axis. I rewrote this with correct equations so the legs do not have to skid on the floor to achieve a correct turn. So far I have walk forward, walk back, turn left and turn right, sit and stand implemented. I consider the project is completed, but It will provide a useful test bed to work on other gaits for another robot that I would like to do.