Robot works short and then collapse, then restart and repeat all. Can anyone help?

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Hi Santa Dragon,

Your redesign looks great and sensible to add the bearings! Did you take the base model from DIY Robotics and modify that? Are you happy to share the modified design? I am not a mechanical person and was going to 3D print the robot components and then try and retrofit bearings which I don't think is practical as one could run the risk of damaging the parts.

Onto your problem.....

I recently got the time to build the control board and play around with the software (having downloaded everything some 8 months ago!). It is clear from the Arduino sketch that the software has not been clearly thought through, has been poorly designed and as such very, very poorly implemented. Point in case is the PC (data) update. In the sketch this is defined as follows:

const long interval1 = 5;               // interval at which to Send Data (milliseconds)

Considering that the total (defined) packet length is 15 characters, with a serial port setting of 9600:8n1, 10-bits are sent per character which means that a total of 150-bits are sent. At 9600 baud this will take at least 15.625ms. At a 5ms update rate the software will fill the Tx buffer faster than it is emptied. Looking at that my first thought was the 128-byte buffer will overrun very quickly. However, I didn't see that happening and so read up on the serial.write function that is used (https://www.arduino.cc/reference/en/language/functions/communication/serial/write/). This is what it says in the notes and warnings:

"As of Arduino IDE 1.0, serial transmission is asynchronous. If there is enough empty space in the transmit buffer, Serial.write() will return before any characters are transmitted over serial. If the transmit buffer is full then Serial.write() will block until there is enough space in the buffer. To avoid blocking calls to Serial.write(), you can first check the amount of free space in the transmit buffer using availableForWrite()."

Definitely not efficient and I wouldn't be surprised if the sketch is buggy.

Again with the supplied PC application (I am running DIY_Robotics_EducativeCell_720p.exe on my notebook) I noticed on connecting to my Arduino Micro, the yellow Rx LED is continually on (from a visual check). For some reason the PC application is writing to the Arduino Micro at a very high update rate which makes no sense at all. In practice the Arduino Micro should only be written to when a parameter is changed via the user interface. The duplex serial comms is working as if I change the digital inputs, the change is displayed on the user interface. Due to time constraints I haven't delved into this issue any further, but I will.

The long of the short of it is that if the PC software is of the same standard as the Arduino sketch and if the software (as a system) has not been adequately tested then more than likely your problems are due to undetected bugs due to possibly poorly implemented code.

I shall in due course be rewriting the sketch as-well-as the PC-based control software (tailored to my requirements) so that I know the system will work as expected. I shall upload both the sketch and the PC-application to this forum when it has been completed and thoroughly tested in the hope that it will help others who wish to play with the system.

Hi Paul,

thank you for your compliments.
Yes, I just took the design what was available (cause it was good so far) and updated it with ball bearings, as I recognized in a first test without them a shaky movement due to the rough surfaces of 3D-printed parts.

As I am in opposite to you the mechanical guy, I understand of the prgrammers part only "overflow" and that is mostly not good (except money overflow *small joke*).

But I am happy to hear that we could manage together to maybe improve that project for public use.
My goal would be to have a smart and handy version that people can use for small and hobbyist applications without paying thousands of Dollar / Euro and just play around to learn kinematics and teaching / programming a robot what does not move like a disabled :´)

Regards,
Philippe

Hi Philippe,

Good to hear from you. I like your idea and am very happy to work with you in getting a robust, reliable and correctly functioning DIY-Robotic arm going that will help those interested in the technology in assessing and playing around with it. I have a specific need with regards the system, hence my interest in the project. I have thought about the software (both the PC application and Arduino code) and have worked out how it should function as a system and from a user interface perspective. I am just busy designing it and then will implement everything. I am a bit short of time at the moment but have prioritised the implementation/testing with regards my free time. As mentioned I would love to use your design of the arm with the included bearings. If I can get the files from you together with information on the required bearings (and from where they can be ordered/sourced) I will get the components 3D printed and the arm built. I'll then be in a position to test the developed software. As mentioned I shall make the SW freely available on this forum and will provide whatever documentation is required so that people who want to use it, can understand how to use it and, importantly, how it works.

Pursuant to my comment pertaining to the (dubious) operation of the control software (DIY_Robotics_EducativeCell_720p.exe) in my initial reply, I have since dug a little deeper and have confirmed my initial suspicions. The following data was captured with a Saleae Logic16 on running the PC application and connecting to the Arduino Micro. I am transmitting the USB-based received data (sent at 9600 baud) from the PC application, via the ATmega32U4 on-chip USART (serial1) at 115200 baud - hence the Tx label:

As I expected for some bizarre reason the PC application just writes to the Arduino Micro continuously with the same data (not good) - I have seen that the interval between writes can be as short as 11ms! At 9600 baud and at such a high update rate, this just hammers the poor ATmega32U4 microcontroller. I have also monitored the traffic on the USB port connected to the Arduino Micro using USBTrace (https://www.sysnucleus.com/) which is a great program for PC-based USB debugging and protocol analysis. I captured a lot of data and not once (at any stage) did I see return traffic from the Arduino Micro. From what I have debugged it is doubtful in my professional opinion that the software, as provided, can or has every worked properly.

Philippe, just to give you an idea of where I am going with the PC-based control software. It is very much a work in progress.

Hi Paul,

looks great the "WIP" and of course I will share my files with you and the community:
https://www.dropbox.com/s/6ykkgbarzqw8ug2/DIY-RoboticCell.zip?dl=0

As soon as the electronics work fine I gonna modify my re-design further as I want to slim out the bearings, because at the moment they are way bigger than necessary and so also heavier.

ZIP includes:
- all parts as .STL
- an Excel sheet with data to the needed parts
- one .STP of the complete assembly

Looking forward to hear of you again :)

Regards,
Phil

P.S.: If you are living in or near to Germany I would offer you to send my arm + control board, as it is standing around anyway actually and I am on another robotic project (a SCARA) and my first DIY-CNC mill anyway xD

You can contact my by ICQ: 94321016 for example :)

Hi Paul,

First of all, I can garantee that the provided PC software works on my end.
However, it is obvious that many people have problems with it, so it needs to be improved.

Keep in mind that this project was meant to be a fun/educative project for hobbyists.
Limited ressources were used for this project.
The package you have downloaded is the first and only iteration ever made.

You seem to have done a great job analyzing the serial communication and pointing out real issues.
If you wish to fix some bugs and improve this project, we would be more than happy if you share your work with the community on this forum !

If you download the package again, you will now find the Visual Studio project (source code) for the PC software:
https://diy-robotics.com/educative-robot-cell-free-package/

Have a good day.

Salut Mathieu,

in general you are right. "Fun / educative" shouldn't be bugged either ;)
So if there are, as you mentioned, "many people have problems", it could be time to work on it or delete the offer, before the trust in this project and company what offers half completed project is lost.

But no worry, if the ressources are offered to those like us and the community we can work it out so that it is really "educative" ;)
Regards

Hi Gents,

Phil good to hear from you. Thanks for the offer re controller and arm - I am, however, in Perth, Australia which is some distance from you in Germany. Fortunately I have all the requisite test equipment/tools for developing and testing the software without the need for the robotic arm itself - as mentioned initially I have built up the controller. My focus is to implement the design I have done and thoroughly test it so that the system is easy to use, robust and reliable. Once I am happy I shall send you the PC-based application, Arduino code and detailed instructions for how to use it (I'll also include Mathieu). I'll only 3D print my robotic arm once you are happy with your modified design. As mentioned previously all software will be made available on the forum with the requisite disclosures of course.

Mathieu. Thanks for the link. I had actually looked at the PC-based code when I initially downloaded the DIY robotic arm package. Not being familiar with C# or .NET platform development I really didn't delve into the code. For PC-based application development I tend to use Embarcadero's C++ Builder as I have a selection of good visual components available to me. Some I have developed and others I have purchased. Anyway it is an environment that allows me to develop with ease. I can appreciate that the project was developed for educational purposes and was thus done so on a shoestring budget. Experience, however, has taught me that if a project (be it educational or commercial) is buggy, rather than enthuse people it irritates them. I also believe that if something is for educational purposes it must work correctly out of the box so to say. Once everything is working I will send you what I did exactly along with whatever (C++) code I had to write to make it work. I shall then leave it to yourself to refactor the original PC-based application.

Hi Mathieu,

As I said I would, I have developed a new user interface and Arduino-based code for the educative cell. The software is both robust and reliable now and I have created a single installation file that installs the PC-based application under the current (windows) user along with all supporting files and documentation. When one runs the install package one can get information on the install by clicking on the More Information button.

The installer is not digitally signed so Windows 10 and 11 may have issues with that in terms of installation. Windows 8 complains but allows one to do the installation anyway. The control application was developed on a Windows 8-based platform, but once installed should run under Windows 10 and 11 using the compatibility mode.

The install exe is approximately 4.5Mbytes so if you e-mail me (you should have access to my e-mail address via the forum database) I can send the file to you. You can then test it if you are interested and make the install exe available to forum members.

I haven't had the time to implement system programming yet, so that one can execute a sequence of commands to make the robot do a specific task. I need to determine how best to implement this feature and then design/code it in my free time.

Kind regards,

Paul

Hi Paul,

just wanted to ask if this software will be available for us (other forum members) to download. I almost finished building my version of robot, however provided software crashes and servos can't be controlled. You would save me a lot of time and effort.

Regards.

Hi Dario,

Good to hear from you. This forum doesn't allow me to upload the installer so I shall have to create a GitHub account and place the software there for all interested parties to download. I'll place the link on this page when done. Will attend to it asap.

Kind regards,

Paul

Hi Dario,

Uploading the install exe that I created to GitHub is not a good idea. Git-based resources work well with text files, but they're not so good with binaries. The install program installs both the requisite Arduino sketch and the PC-based control application along with requisite information and documentation about the software. If you are happy to send me a contact e-mail address via this forum I will e-mail the install program to you - it is about 4.5Mbytes in size. Alternatively, maybe the forum moderator can assist in making the software available for all interested parties to use!

Kind regards,

Paul

Hello everyone,

I'd like to share a video of my 6-DOF robot arm. I created this to practice my skills in Fusion 360, so the 3D model isn't an exact replica of the one provided by DIY Robotics. I've encountered some issues with joint 5 and had to modify joints 2 and 3 to fit the servo horns, as using just a servo screw caused the entire joint to slip (possibly due to using PETG for printing, as I couldn't perfectly fit the servo gear into the hole by melting the plastic with a lighter). Additionally, I faced some software challenges, but Paul assisted me with his control program. As you'll see in the video, there's still plenty of room for improvement in this project.

https://gofile.io/d/dwuDtS

Hi Paul,

How can I get the files so I can test them on my robot arm?

Thanks in advance.
Jesus