In order to make the 3DOF Quadruped kit 4DOF, what additional brackets/parts have to be added?
@Mt_Mintronics91 Welcome to the RobotShop Community. Can you confirm you mean the following Lynxmotion robots? Do you already own the 3DoF?
3DoF:
4DoF:
If so, we can provide a list of parts. The body is effectively the same, as are the shoulder joints and link between the shoulder and knee. The additional degree of freedom is between the knee and ankle joints.
Thank You, Wanted to make this 4DOF
I see the additional degree, is it achieved with this bracket? Please provide the additional parts to upgrade it to 4DOF, that would be awesome
Ah, understood. Note that the robot you have is made using the Lynxmotion Servo Erector Set V1 modular building system. There are no specific ways to make a 4DoF arm since the bracket system allows for many different possible designs.
Based on what you’re describing, one way would indeed be to replace the C-bracket in the knee by the angle bracket. You would also replace the 90 degree bracket connecting the knee to the lower leg by the C-bracket you had removed (or another angle bracket - the choice is yours), to which a servo and additional multipurpose bracket would be needed.
Note however that we have not tested a quadruped robot with 4DoF legs, let alone using the Hitec 645MG servos. You would need to know which style of walking (dynamic vs. static) and angles are best. If you try to stretch the legs out, the servos will likely not have enough torque, causing the robot to fall. For example in a dynamic gait where two legs are lifted, the servos in the shoulder of the two remaining legs touching the ground need to produce a LOT of torque, which the 645MG likely won’t be able to provide.
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Would HS-5645MG be he next option in terms of Torque? Are the pins on the SSC-32 programmable for digital servos? You make an insightful point regarding torque, it has been done with the 645mg, I’m sure it calls for alot of trial and error that could be surpassed with a higher output servo. I do not have the kit yet, am very much set on customizing the platform, although. Would I be better off with the SQ3U or Flowbotics studio version if I am adding leg sensors and additional servos? It seems both versions are equally as expandable, one bypassing the Botboarduino, which seems like a very no frills microcontroller
Video where 645mgs are used
645MG: 9.6Kg-cm / 133 oz-in
5645MG: 10.3Kg-cm / 143 oz-in
The two are quite similar in specs actually, so although the “digital” aspects may have some advantages, it’s not on torque. If you really want / need higher torque, you might consider replacing the multipurpose bracket and C-bracket in the shoulder by ones for a larger servo like the 755MG:
Would I be better off with the SQ3U or Flowbotics studio version if I am adding leg sensors and additional servos?
The SQ3 provides the 3DoF version of what you want, but the FlowBotics interface is only set up for three degrees of freedom, and modifying it for four will take quite a bit of understanding of the back-end. If you opt for the BotBoarduino version, you’ll still need to modify the code to use a fourth degree of freedom per leg.
It seems both versions are equally as expandable, one bypassing the Botboarduino, which seems like a very no frills microcontroller.
The BotBoarduino is essentially as powerful as an Uno with more IO.
You might want to reach out to Erik Lely to see if he’d share some tips for you. He seems to have provided a link to the code he used via Dropbox.
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