Embedded Files
Project Goal
Project Goal
The goal of the project is to create a robotic dog. by the time i started this project i was fairly competent with CAD theory and design through time on a FIRST robotics team. the goal of the project is to improve my skill with Arduino coding and the solving of kinematic equations for robotic arm solving.
The Cad
The Cad
Overview
Overview
the largest chalange i had witht the original CAD was the need for two powerd likages to be driven from the same axis. while not a huge problem normaly this was considerable harder to acheve when your 3d printing most of the robot, as any shaft i would have designed would have been printed againsed the structural axis of any 3d printed parts my final soulution was to add an adisonal likage to the system and place the second servo above the first one.
Geomitry scetech
Geomitry scetech
as with most of my projects i started with a geomitry scetech to find all a leg ttructure that both worked well and i felt could reach all the points i felt it needed to reach and also had porportions that i felt looked good.
First iteration of leg
First iteration of leg
the first iteration of the leg was sloppy at best the two servos controlling the leg were end to end on eiter side of the leg witch created a bulky wide hip area on the dog.
The second layout
The second layout
the second major iteration of the dog leg stacked the two servos atop one another and used an additional linkage between the top of the parallelogram and the top servo to translate the motion into the leg itself. another thing of note is that until i started 3D printing the legs i planned on using carbon fiber rods to connect the outer and inner leg.
the main body
the main body
the body for the initial design for the robot changed verry little between the first time i designed it and what would have been the final printed model. the bot had a longer rounded body shown to the left and fetured an open top to allow for easer acsess to the wires for later. the shell was constructed of 4 indifidual mirrord peaces that slot together using pins int he shells outer walls and than larer i added lazercut acrilic plates to hold exerything together.
the quartars
the quartars
to the left is the original wuarter shell the box at the bottom was used to store the battery during use and although not origonaly addad to the moddle the extera space at the front allowed for the later addition of sensors later for planed autonomas use.
Central plate
Central plate
part of the the initial design inclided this acreilic plate in the center of the robot designed to hold the robot together and ceep the pined sections from seperateing. this plate also served the duil function of meing a mounting plate for all my electronic components, orifonaly just as a Arduino Mega, for conteroll, but later also for a ESP 32 to allow for wifi controll.
Practical changes
Practical changes
original
original
the orifinal design as stated earler was ment to use carbon fiber rods as conections for the upper and lower segments of the leg
final
final
the final design was fully 3d printable includeing the upper and lower segments of the leg with no need for any adishonal parts such as carbon fiber rods.
linkage
linkage
the original printed leg had lots of slop in the mechanisoms making later codeing of the leg paths dificult to predict and compansate for the first change made was to the upper linkage between the servo and the top of the patalalagram, creating a U shape helped considerably to reduce the toleralnces of the end position of the leg.
Bumies
Bumies
the second major changes was to move both mounting points to difernt sides of the lower atachment point moth atachmant holes were origonaly on the same side so splittong them helped reduce lashback on the lower part of the paralalagram. another change was to raise the lower arm slighly from the servo reduceing interfearinace witht he central screw on the servo allowingt he lower arm to sit flush with the servo arm.
Quality of life
Quality of life
the last major change was to split the lower arm on the the paralalagram into 2 pieces this allowed me to print more parts of the leg flush with the build plate and segnificantly reduced overhangs while printing as a nice bonus it increased the acsesability of some of the bolts while asembaly.
A Shift in derection
A Shift in derection
Problems
Problems
in the original dsign for the robotic leg i was haveing trouble with the kinimatic equations for the last linkage (shown left in yellow). while i knew that thier had to be en equation to intergrate the tip linkage into the rest of the project i could not figure out what that equation might be. my soulution the this problem was to shift to a 5 bar linkage for the legs.
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