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1  Topics / Robotics / Re: Thesis suggestions in robotics for electromechanical engineer on: May 03, 2011, 04:10:07 am
Yeah they wanted to simplify the complex human hand design but combining the universal's gripper strength with human fingers/palm should be a combination worth investigating. In fact the idea of the subject is nicely written in the comments section of the link I posted above (the first reactions). Making a robotic human hand is so complex but I hope I can achieve some acceptable results (and like you say I will probably encounter many 'unknowns' but that is the challenge)!

Thanks
2  Topics / Robotics / Re: Thesis suggestions in robotics for electromechanical engineer on: May 02, 2011, 12:05:14 pm
After some discussions with the responsible people and after knowing more about the university's interrests I made a decision for my thesis subject. I stayed away from the artificial intelligence side of robotics (that is for later!) and sticked to the mechanical stuff. It was a subject they proposed and I think it is a good start for me in the field of robotics.

It is about engineering and building a robotic gripper using universal grippers (from scratch). The goal is to pick up as many things possible with a 2 or 3 fingered gripper design making use of the universal gripper system (http://www.gizmag.com/universal-robotic-gripper/16729/) in each finger and/or palm. It must be able to hold all kinds of objects from the environment. I should also think about a way of controlling it as user-friendly as possible (with a glove, buttons, joysticks,...).

I'm already looking forward to it and I hope I can use the Arduino platform for this 'project'. Of course I hope to get some useful results but first I should think about finishing this year with no problems smiley.

@ TND,
What did you choose for your endwork? Thanks for the news sites links, I added them to my 'daily check' list.
3  Using Arduino / Sensors / Re: Guide to gyro and accelerometer with Arduino including Kalman filtering on: April 27, 2011, 03:33:09 am
This is a great for IMU-starters like me. I will give it a try.
Thank you very much.

Fons
4  Using Arduino / Sensors / Re: angular position from gyroscope on: April 25, 2011, 04:13:47 am
Hi,

I would like to copy the pitch and roll of a platform but don't know what I need for it.
So basically I want to reproduce the pitch and roll angle on another platform so that the two platform are 'pitched' and 'rolled' the same way (so I can give the occupants on platform A the same feeling as if they where on platform B). That is why I post this message in this topic (I need to know the angular position after all).
Do I need accelerometers, gyros, compasses or a combination of them? It looks like I need a balancing robot kind of setup which uses a combination of gyros and accelerometers (?).
I only know that gyros measure angular velocity and accelerometers measure acceleration and that an iphone uses accelerometers...

Thanks,
Fons
5  Topics / Robotics / Re: Thesis suggestions in robotics for electromechanical engineer on: March 23, 2011, 05:58:05 pm
Ok thank you guys!

It is a wonderfull world (robotics) to play in and yes there are so many thinks you can do...
Emotions/human interaction is a hard nut to crack but it has a lot of potential.

This weekend I will hunt down the internet and look at those links. They surely look cool at first sight. I should indeed be more specific.

Fons
6  Topics / Robotics / Thesis suggestions in robotics for electromechanical engineer on: March 21, 2011, 05:00:36 pm
Hello everybody,

Don't know if it is the right play to look for but here is my question:

At the end of this academic year I need to hand in a thesis subject for my masters degree in electromechanic engineer at GroupT Leuven College university. The school has some suggestions but they are open for new suggestions so your ideas are more than welcome. First of all I'm interested in the tele-operation of humanoid robots (more the mechanical side) but that is not the college's focus. The college is currently working on robot/human interaction topics and robot/environment interactions (together with another university). I would like to build something and than program it but it seems they use platforms that are already built and that need some complex code to do cool stuff (in robotics you can't have one without th other I guess!). So I will probably suggest something that I will build and then let it do something.

So if you got some (good) ideas please let them come. Something concerning robotics of course! If I know more info about what I can suggest and what not I will let you know.

Thanks
7  Topics / Device Hacking / Re: Arduino PS/2 Mouse controlled RC car on: March 20, 2011, 05:17:06 am
Good first project! I like it cause my first Arduino 'project' is to control two DC motors with a PS/2 mouse too.
Why are there 3 different files (one .txt and two .zip files) you can download on the Arduino homepage about PS/2 interfacing? If I only want to read the data from the mouse I only need the first .zip right? I haven't tried much yet but I am just wondering.
8  Using Arduino / Motors, Mechanics, and Power / Re: A4983 stepper driver problems on: March 09, 2011, 01:52:11 pm
You're welcome hehe smiley .

Using PWM would be great indeed. I tried using standard PWM (500Mhz) and it works pretty well at quarter and eigth steps. Like you say changing this frequency means I have to understand the ATMega's registers. I want the most efficient result so I will surely give it a try and fine tune as long I can understand what I'm doing. But what I have now is more than enough in fact to start with.
Using home-made PWM, 300 microseconds (thats 1600Mhz pulsing) is still very well and I can use half steps. Don't understand why Arduino's standard PWM doesn't work with full steps (it's slower than the home-made PWM signal).

The fact that the serial part is making it slow is no problem after all. I don't have to use it. But good to know.

I'm not sure if I understand timed interruption. Is it like the BlinkWithoutDelay example? I undrstand that example/technique.
For my project I need to control 3 such stepper motors this means that I will also have to read 6 pots to control them. I don't know if my Arduino UNO can handle all that reading and writing at such a pace without loss in performance. If it can't I will have to find some more exotic/better code.

Thanks.
9  Using Arduino / Motors, Mechanics, and Power / Re: A4983 stepper driver problems on: March 09, 2011, 08:39:48 am
Got it!

Used your test code with 500 microseconds and worked very fast and smooth (50 was too fast, the motor made noise but didn't move). The reason why your code worked was because it did not contain serial.print command. It seems that using serial.print is not a good idea. I removed it from my position control code and it worked too. Now I will test the ideal pulse but without using println.

I use full steps cause my position sensors are not accurate enough. I have no load. The motor got warm after some serious stepping exercices but not alarmingly, looks that the current limiting is good.

Thanks for the help. I can go on with my project!
10  Using Arduino / Motors, Mechanics, and Power / Re: A4983 stepper driver problems on: March 08, 2011, 09:20:44 am
Sorry that I'm putting the topic back in the spotlights but I'm stuck with my speed control of my stepper motor. I contacted Pololu and my motor should do a few hundred RPM. They told me that the fact I can only reach 10 RPM is due to a bad code. In the post above I posted a code that I used for checking the best pulses. The code below is my code for positioning the motor at a precise angle. I would like to reach 60 RPM which means a pulse every 5 milliseconds (200 step motor) but using 5 milliseconds results in a poor 10 rpm...

If someone as an idea why I can only reach 10RPM please tell me! Could it be due to the use of the delay function? Or maybe my driver is broken (I saw solder smoke a few times because I connected the power supply the other way around)?
I will try another stepper motor and see what it does.
Thank you.

**CODE**

int stepPin = 2;
int dirPin = 3;
int enablePin = 4;

void setup()

  Serial.begin(9600); 
  pinMode(stepPin, OUTPUT); //STEP output
  pinMode(dirPin, OUTPUT); //DIR output 
}

void loop()
{
  int targetValue = analogRead(0); //pot value for the position input
  int actualValue = analogRead(1); // pot value from motor position
  int error = targetValue - actualValue;
  if (error < -3)
  {
    digitalWrite(dirPin, HIGH); // direction HIGH
    digitalWrite(stepPin, HIGH);
    delayMicroseconds(XX); //replace XX with a number (microseconds)
    digitalWrite(stepPin, LOW);
    delayMicroseconds(XX); //replace XX with a number (microseconds)
  }
  if (error > 3)
  {
    digitalWrite(dirPin, LOW); // direction LOW
    digitalWrite(stepPin, HIGH);
    delayMicroseconds(XX); //replace XX with a number (microseconds)
    digitalWrite(stepPin, LOW);
    delayMicroseconds(XX); //replace XX with a number (microseconds)
  }
  if (-3 < error < 3)
  {
  digitalWrite(stepPin, LOW); //when the position is reached stop pulses
  }
  Serial.print("target:");
  Serial.print(analogRead(0));
  Serial.print(" Actual:");
  Serial.print(analogRead(1));
  Serial.print(" Error:");
  Serial.println(error, DEC);
}
11  Using Arduino / Motors, Mechanics, and Power / Re: A4983 stepper driver problems on: March 05, 2011, 10:33:09 am
Ok thanks,

I thought I could achieve a speed of 1 revolution per second but after some testing with various values the best I achieved was only 1 revolution every 6 seconds. That is too slow for my project (I use pololu's 42x48mm stepper motor).
1 revolution per second means 200 pulses per second (it is a 200 step motor), with full steps this means a time of 5 milliseconds so I was thinking of using a pulse length of 2 millisecond and a time between pulses of 3 millisecond. Is my reasoning correct?
Here is the code I used for testing the optimal pulse:

int stepPin = 2;
int dirPin = 3;
int enablePin = 4;

void setup()
{  
  Serial.begin(9600);  
  pinMode(stepPin, OUTPUT); //STEP output
  pinMode(dirPin, OUTPUT); //DIR output  
}

void loop()
{
  digitalWrite(enablePin, LOW); //enables the driver
  unsigned int lowTime = analogRead(0); //potentiometer for variable low pulse time
  unsigned int highTime = analogRead(1); //potentiometer for variable high pulse time
  lowTime = map(lowTime, 0, 1023, 100, 100000); //from 0,1 millisec to 100 millisec
  highTime = map(highTime, 0, 1023, 100, 100000); //from 0,1 millisec to 100 millisec
  digitalWrite(dirPin, LOW); // direction LOW
  digitalWrite(stepPin, HIGH);
  delayMicroseconds(highTime);
  digitalWrite(stepPin, LOW);
  delayMicroseconds(lowTime);
  Serial.print("lowTime:");
  Serial.print(lowTime, DEC);
  Serial.print(" highTime:");
  Serial.println(highTime, DEC);
}

I hope I don't need another stepper motor for my project. If printers use these motors than something is very wrong here!
12  Using Arduino / Motors, Mechanics, and Power / Re: A4983 stepper driver problems on: March 05, 2011, 03:27:07 am
Wow I feel like a fool. Apparently the problem was that I switched the polarity of the power supply. I was sure it was properly connected so I never checked it! The stepper motor works fine and it is a beauty.
Sorry for posting a unnecessary topic on this forum. How can I delete this topic?

When I was calibrating my motor I heard the local radio station from the motor when I touched the current limit pot on the driver with the screwdriver. Strange to say the least!

**EDIT**
How do you increase the rotation speed of a stepper motor?? I have a 1 microsecond pulse every 2 microseconds at the step pin but with 1 microsecond the shaft turns very sloooow (and can't go below 1 microsecond I think).
13  Using Arduino / Motors, Mechanics, and Power / A4983 stepper driver problems on: March 02, 2011, 03:29:22 am
Hi,

I posted this on the Pololu support forum but I'm waiting for an answer so I'll just post it here too. I hope some people have a good experience with the A4983 stepper motor driver:

I have problems calibrating and using my A4983 driver with the Arduino UNO. When I connect my 12V DC supply to the driver I smell within 10 seconds solder and see some smoke (melting solder?) from the driver. I cannot see any unwanted solder bridges (that liquid in solder, does it conduct electricity??).
I made following connections (for calibration/current limiting):
- grounded STEP, DIR, MS1, MS2, MS3, and ENABLE
- grounded GND logic supply
- connected SLEEP to RESET
- VDD logic supply to the 5V pin of my arduino
- connected 5V to VDD for selecting 5V logic
- 1A, 1B and 2A connectd to a stepper motor (pololu #1200) to red, blue and black wire respectively.
- 2B is also connected to the stepper motor (with wire green) but got my multimeter between it to measure the current. It measured 0,00mA. So there is current going in but for a reason it can't go to the motor. The grounds are connected to the Arduino's GND pin.

I measured all pins and they are grounded or are high (sleep and reset are high). The used power supply is 12,2 V.
I don't know what I have to do now, hopefully someone can tell me what is wrong. And what can I measure to know if it is still alive? I'm afraid of trying it again cause I may damage the driver even more (if it is still alive).
If you need some extra info ask me please.

Thanks in advance.
14  Topics / Robotics / Re: My new Robot on: February 25, 2011, 03:46:47 pm
To all those who work in robotics we would like to techniques to link digital image processing our robot, well here I put a video on how do that with C #, OpenCV and Arduino, we can control two actuators with the movement of the face, when the face moves in X and Y.
You have to polish it, but hey it's a start.

That is cool. The servo reaction is not smooth but like you say its a start. My first project is also about headtracking (but then mechanically) and I would like to built a plexiglas setup like you did, nice.
15  Using Arduino / Motors, Mechanics, and Power / Re: Turning a motor into a servo on: February 17, 2011, 01:48:19 pm
Okay so my motor driver is the limit smiley. I used  a simple method to change PWM frequency (bit-banging PWM - see http://arduino.cc/en/Tutorial/SecretsOfArduinoPWM). I posted the used code earlier. It is probably not efficient but it is all the arduino needs to do. I did not yet tried the timer method.

Thanks
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