Robotic – Final Project Part 5(Final ) – The Curious & Timid Turtle.

Continue from my part 4 of this project updates, This is the final part which leads to the completion and is rather long as many things from getting the power supply, modelling, testing, painting, assembling to coding had been done in the past 2 weeks.

First, the final video of The Curious & Timid Turtle.

And then, into the process….

NEW POWER SUPPLY!!!

At the end of last post, I was waiting for the power supply to reach and it did during these 2 weeks so I’ve tested it out, The one that I bought is a AC-DC converter at 6V 20A when all I needed was 6V 8A, i decided to buy the higher Amp one just if i need more amp in the future, and I could also share the supply to my Interactive device project during the End of sem show.I did some wiring afterwards.

And after the wiring, I did power test, it could easily run 8 servos simultaneously with nothing overheating. which is a great news for me!

NEW LEVER SYSTEM FOR THE LEGS!!

Since the last post that I’ve decided to change the system in the legs to save space and shorten the overall length by stacking a smaller MG90S on the MG966R to act as a lever system to pull control the legs.
After testing this system out and seemed to be working, I merged it with the turtle leg that I’ve modeled in Zbrush, I don’t know about Zbrush before this project and it tool a long time just to model the shell, the legs and the feet.

I merged the leg with the previous test “rod-like” leg because I’ve already gotten the dimension in there so i just need to scale the Zbrush modeled leg accordingly to fit the “rod-like” leg.

changing of the entire base layout to reduce size and increase EFFICIENCY for the back legs.

At this point, I was wondering if I should change the MG966R(metal gears) into SG-5010(plastic gears) due to weight issue I might face later after adding the shell and so on, so I weigh the motors and decided that I should change the back leg to SG5010(but I changed it back to MG966R one day before submission due to the internal gears got loose in SG5010)

SG5010 is 44g, the difference is 10g so by switching 2 motor, I could save 20g of weight in my system. and so I did.

Major changes were made for whole layout of the base due to various reasons – the backleg will move differently from the front and since my project is basically a turtle with round shell instead of a flat one, it made more sense to use a smaller but higher layout rather than a flatter and wider one to make use of all the space within the shell.

This was the previous layout(Version 4) which made the whole shell really flat and big

and this is Version 5(left) and Version 6(right) which I stacked the servo for the back leg on the shoulder servo of the front leg.

This was quite the final base before I added the mount for the small backleg servo and the servo driver mount which will be attached it using screws.

Zbrush Modelling Nightmare Funfair

Since my Zbrush was cracked, it crash rather often and I did the same thing over and over if I forgot to save frequently and hence it took quite long to model anything, but well~~

and tried to model it as close as the turtle head as possible.

slowly, I edited it to look like a reptilian head, and instead of getting the real look of the eye, I’ve decided to enlarge the eye to give my turtle a cute look (and because the eyelid looks too hard to model).,

As for the shell… it took so much time and crashes to get it right, because the shell cannot be too thin(unable to print later) and cant be too thick (too heavy) and I cant find a function that could allow me to see the thickness (like reduce opacity of the material to see through), so everytime to check the thickness, I have to export into STL, and import into Tinkercad to check the thickness.

This is like the version 11 of the shell.

I used this image as the sample for my shell pattern

topview when I marked the turtle pattern onto the shell

the rim of the shell i did without any reference and I marked it out

Everytime I made major changes to the shell, I’ll have to import to Tinkercad to check the thickness and shape.

this was almost the final shell before splitting the shell for printing.

I split the shell top(transparent) and bottom(Pink) in Zbrush because its following the shape of the pattern of the shell, and the top half into 2 in Tinkercad as a straight cut will ease my printing later. I also added 4 holes that allow me to reassemble them using bolt and nuts later.

The model appear

Nothing is more satisfying in removing the support in one whole chunk(I did alot of cutting before this video so I can pluck out in one piece.)

The comparison of V4 base with V6 base. V6 is much shorter at 150% higher,

The white one was Version5 which was a test print that I realized that the motor is unable to be fitted into it so I cut some material off and remeasured.

the front of the base is a liner bearing that i could slide the rod for the head.

this is the liner slider an an aluminium rod for the head system.

Printing for the base shell:

It look really nice, like wooden texture due to layering.

The base of the shell took almost 7 hours.

Printing for the top shell:

half of the shell took 10 hours and 30 minutes to print

The completed print of front and back legs.

and the completed print of the shell with the legs.

And then the finishing(PART1)of the model.

Before the spray with Krylon Dual Superbond so that I don’t have to sand it to achieve a reasonable finish.

and the small bolt and nut to hold it in place.

The Final mechanism of the turtle

testing out of the head slider and to mark the length I need it to move and cut.

The mechanism to slide the head that I will use after cutting the rod to almost the size I need.

3d print a longer fulcrum to increase the distance

and I file off the bottom and the side of the rod to increase the angle of movement using the steel wire.

this is the final mechanism for the head after I printed a small piece to prevent the wire from tilting too much when pushing the rod.

the head could be push and pull out nicely even before adding the string to control the tilt of the head.

metal rod were epoxyed into the head to tie the elastic thread to control the tile of the head.

and a elastic thread was added to counter the tension created by the elastic thread to turn the head

And then the finishing(PART2)of the model.

I sprayed the overall colour of the turtle with Tamiya Acrylic paint.

halfway through the spraying, I remembered that I need to epoxy the two pieces of the shell together first.

and so I epoxy it 3 times and sand off the extra epoxy to hide the glue line by a bit.

although it is still visible, I think it is a reasonable standard since I will be painting it further with darker color afterwards which will hide the glue line more.

and i masked the eye using tape for me to spray it black and glossy

and i carefully cut out the tape in the shape of the eye.

The final test of the turtle before I finally started coding it. The head uses elastic thread because it will go forward and retract, since I dont want anything to be loose and might interfere with the shoulder servo motor, I decided to use elastic thread so that the thread wont be loose when the head is retracted.

This is the almost completed sequence of action,the turtle’s movement is quite restricted due to the shell and the back leg is unable to push the turtle forward because of the shell’s restriction as well as the weaker servo(MG90S) which is responsible for the forward and backward thrust, while the MG966R is strong enough to lift the turtle up, so the turtle could do movements up and down but not walk.

After this, I added a few lines of code to substitute the button pressed with sound sensor to make the turtle more intractable and a few more actions that made it more timid looking (head peeking out to check the environment before the whole body come out.)

In conclusion:

Overall, I really liked this project although I kind of regretted trying to make a turtle during the process because the shell is giving a lot of layout and movability problem made me kept thinking that if I were to make something without shell, it will be so much easier, but the reason that I first wanted to make a turtle is the best is because the shell naturally hide all components that break the user’s perception that this is a robot and a turtle is my spiritual animal, now that I finished the project, I am really glad that I sticked to my initial idea of making a turtle and persevere through all the problems I faced(mainly hardware and mechanical problems which I changed my system and design so many times.).

This was what made into my final turtle with many component being edited into the next version.

With more time, I am sure that I could code the turtle be able to be scare back into the shell by another sudden loud noise – I tried to change the delay in my code to Millis multiple times and it do every action in the sequence twice so I sticked to using delay for now, which disabled me to write the activation code for using the sound as a trigger since it is in a delay loop. But, it looked really nice for now even if there is only one sequence of movement and I am glad that people were thinking that the turtle is cute when they saw it.

Author: Ong Zi Feng

Just doing things, making stuffs. View all posts by Ong Zi Feng