2DOF (Originally 6DOF): 24V Wheelchair motors and MD13s Motor Driver

Dear all,

I've decided to create the thread for my project. As a lot of users here, I started by doing a lot of reading in other people's projects until I've gathered the courage to start my own.
I really enjoyed seeing the projects that all the users built here and the amazing support the users provide to each other in this forum.

My idea is to build a 6 DOF. Basically because it seems that with all the degrees I can have more fun while using the plataform later. I know it might be hard as a first project, but I also think it will be interesting and lots of fun.

About my setup:
I did some research on which components to use. A lot of threads suggest the usage of sabertooths as motor drives and the motors from motion dynamics.
Due to the prices and difficulties of shipment, I decided for some not so usual components.

This is what I've got so far:

1x MD13s motor driver: https://www.cytron.io/p-13amp-6v-30v-dc-motor-driver


1x 24V 250W 75rpm Wheelchair motor: http://aliexpress.com/item/32719954216.html


1x LED 24V 600W Power Supply from amazon:


My idea now is to set up a test bench and test this whole setup. If everything works then I can go foward and buy an extra five of these for the 6dof.

I wanted to give some more information on what I plan to make.

As an electronic engineer, I enjoy building electronic circuits and programming microcontrollers, so a lot of my decision where made based on that. I want to build my rig with rotary actuators, but I was not completely satisfied with how Simtools converts the axis to the motor angles with its profiles.

First thing I decided was to use a microcontroller to use Steward Table maths to calculate the exact motor angles that I needed. This way, Simtools will only export independant axis information and no advanced profile is needed. For this I choose the MSP-EXP432E401Y from Texas Instruments, as it has a lot of processing power and a dedicated floating-point unit to calculate all the matrices, sines and cosines needed for the math.

After that I decided to use another microcontroller to get the angle data, measure the positions with the hall -ffect potentiometers and implemente the PID controllers. (It would be possible to use only TI's microcontroller, as it should be powerfull enough. But this way I though it would be more fun).

To be easier to understand, I made some schematic on how things should be connected:

The coding of the two microcontrollers is practically finished. I assembled a test bench with the one motor and one hall effect pot to test the whole thing.
I'll be posting some more details and pictures on the next days.

Best regards,
BrazilianGuy

Hi. I will be attentive to the progress of your project. I am waiting for the components for a 2DOF. I tell you to buy 2 engines equal to those of your project. I will receive them in the next days. I'm going to use arduino uno and BTS7960. I have seen in a Youtube video that the DOFREALITY platforms use the MD13S controller with ARDUINO UNO without having to install heatsinks. If I get to have problems with the BTS7960 they would be an option for me too. I do not know if for these controllers I can use the same arduino programming as for the BTS7960.

Hi Arielnac. Nice to know that you are interested. I already did some tests with small loads with the MD13S and my motors. They seem to work well. I could not yet test with full load because the wooden levers I've built were not strong enough. I am replacing them with metal ones, but my building skills are somewhat limited.
It should be done by the weekend, them I can post more test results.

Where did you find this youtube video? I would like to get some more information about the MD13S too. It seems that there is not too much people using them.

Hi. This is the video link of the dofreallity platform test. At about minute 16 it shows the interior of the cabinet and mentions the circuits used.

As promissed, here is the test bench I used to evaluate the setup:

The idea is to test the following components:
- 250W DC motor
- 600W Power Supply
- MD13s motor driver
- Hall effect potentiometer
- TI controller (with my own code)
-Self made 'booster pack' for the TI controller (with my own coode)

On my final design I intend to use a 10 cm shaft to connect the motor to the 'legs' of the 6dof plataform. For this test I used a 30cm shaft to multiply the effect of the used weight by 3.
I am using 6kg of test weight here to test one motor, which multiplied by three equal 18kg per motor. For a plataform with 6 motors, that would be a total of 108kg.

The video below is a recording of a 'step test' that I created. The motor is on a fixed position and a sudden step of 15 degress is comand by the controller and back.



In the video, the motor stays on a fixed position until around second 17. After that it steps to a higher position and 2 seconds later comes back to the original position.
Everything works fine, however the wooden shaft I built breaks at the end. If you listen carefully, around sec 20 a laud crack sound can be here... Here is a foto of the result:


Now I will probably need some help fabricating a new shaft. I currently don't have the tools to make it from iron and I do not know if this is something possible to buy. Anyone with a suggestion?

Hi. You should make a lever like this in metal.

man, just as a commend, the link of your motors on alliexpress links to your order, not to your motor i found a similar one but with a bicicle sprock, if you could fix the link would be grate.



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Thanks for the comment man! I fixed the link. It should point to the correct page now.

It has been some time since my last post. I worked quite a lot on my rig, however I downgraded it to a 2DOF. Due to the complexity and size (and my lack of building skills) I decided to simplify the build.

Here are some pics of the progress:

Hi noorbeast, I actually used this method to find my center of gravity. I found that already on another post of yours.

Today I want to post the first video of the plataform in action. There are still some adjustments to be done, but I am very happy with the results already. This is me testing it with LFS:

Hi. It would be convenient to improve the fixation of the motors. When you manage to calibrate Simtools well you will achieve movements that will subject the engines to more leverage.

how much one motor left weight?... look to my thread down page https://www.xsimulator.net/community/threads/motors-for-2dof.14637/#post-197008

i used wiper motor but its not taking weight so ...if i used the same you use so its will be able to take about 100 to 200kg?

It looks very good. Surprised wooden structure can also have such good effect.

Hi. I am also using these motors in a 2DOF. They have a lot of power. I weigh 79Kg and I have tried reloading myself on the front of the platform to overload the motors and they have no problem to move.
But remember that these motors are for 24V and I am using them at 18.5 so that I don't have problems with the BTS7960. With 12v these motors will not work for you.

i know......i want to know how much the motor can take weight

if i used ibts with 12v model of the motot no problem right?...or can i use the 24v but with 12v to 24v converter?