Latest Dada robot drawing

It took me ages to get around to editing this video. The drawing was made back in February, in time for the FITC conference that Justin was presenting at. I guess I forgot about it until then.




Read more about it on the Dada website: http://dada.soulwire.co.uk/2012/04/collaborative-drawing/

Cloud Timelapse

Due to some lab modifications, I've been temporarily relocated next to a window with an awesome view. Here's a timelapse of the clouds last Friday with a bit of Aphex Twin in the background.



I deliberately saturated the colour on the webcam. Somehow it made me think of the cover to Innerspeaker by Tame Impala.

As usual I used a webcam with AnimatorDV Simple+.

L92100 Linear Stepper Motor with Arduino

A few years back I mentioned to a friend that I was interested in using linear actuators for a particular project. They turned up a few days later with this unusual looking motor.

Instead of rotating a protruding shaft, like a regular motor, this motor rotates an internal threaded section (something like a nut). If you hold the motor the way I have in the second picture and activate it then the threaded part rotates. However, if you prevent the threaded section from rotating then the movement of the internal nut pulls the threaded rod through it, with the action of a lead screw.

I couldn't find much documentation from the serial number (ODV76/L92111-P1), so had to do some detective work to figure out how to use it (which is why I'm writing this post). Atually, you can get some data on it by typing 'L92100 linear stepper' into google (rather than all the other characters). Evetually I found this datasheet, and more recently this one too.

It's a 6 wire unipolar stepper so I used the circuit diagram from azega as a base, changing the transistors to N-channel Mosfets (I had some lying around) and not using diodes (I didn't have any lying around). It'd be a good idea to include these at some point.

Here's a video of it working with the Arduino stepper library: 



Currently the motor gets pretty hot during use, which is concerning and somewhat unexpected, as there is no load on there at the moment.

Here's the Arduino code for the movement in the video (a modified version of one of the stepper examples included in Arduino 0022).
 
#include

const int stepsPerRevolution = 200;  // A random value for now

// initialize the stepper library on pins 2 to 5
Stepper myStepper(stepsPerRevolution, 2,3,4,5);           

void setup() {
  myStepper.setSpeed(60);
  // initialize the serial port:
  Serial.begin(9600);
}

void loop() {
  Serial.println(" down" );
  myStepper.step(-200);
  delay(200);
  myStepper.step(-200);
  delay(200);
  myStepper.step(-200);
  delay(500);
  Serial.println(" up" );
  myStepper.step(600);
  delay(500);
}

I hope all this helps someone...

Recent dada (drawing robot) developments

I've just uploaded a few new updates to the dada project website. These are pre-2012 videos but I hadn't got around to editing / uploading them previously.

Dada is a collaborative project I'm working on with Justin Windle of Soulwire fame. The project had to sit on the backburner for awhile but over the last 6 or so months I've been making some good progress in getting our rescued robot arm up and working and writing some control software (the stuff that comes built in to commercial robots).

For those too lazy to follow the link here's one of the videos, showing a home made solution to self calibration and some grid drawing.

Palpating Gripper Video

This is a video explaining the palpating gripper I have been developing as part of my work on augmenting robotic minimally invasive (keyhole) surgery with haptic (touch) feedback.



The basic premise of the work is that more tactile properties may be determined from an object if it can be actively explored using one or more fingers. To facilitate this sort of exploration inside the body I have been designing a robotic gripper that is simple enough to be manufactured for keyhole surgery but has enough dexterity to replicate some of the exploratory hand motions of a surgeon.

This work has been accepted for publication at IEEE Haptics Symposium 2012.

PhD Thesis Online

I've finally put my PhD thesis online with open access. The title of the work is: "Robust and Intelligent Control Approaches for Biologically Inspired Motion Generation with an Anthropomorphic Robot Arm".

The work attempts to find ways of modelling human motion patterns mathematically and then getting a robot arm to obey those mathematic rules in a safe and efficient manner. A good chunk of these rules dealt with producing optimal motion (in terms of 'effort') that could also deal with the robot having a imperfect model of its own body (for example, we didn't model the friction in the gearboxes). All the control is done dynamically (in terms of forces and torques) rather than kinematically (in terms of positions and angles). This is more difficult but gives more control over the robot.

The below figure shows one of the early results in the thesis, where the robot's reaching motion (to a target height) is based largely on effort minimisation and ends up appearing very human. The person in the image is only included for comparison, the robot isn't copying him.

You can view or download the full pdf of the thesis here.

Paper Accepted for Haptic Symposium

My research on a novel miniture robot gripper for tele-operated palpation has been accepted for presentation at Haptics Symposium 2012 in Vancouver.

Haptics Symposium Logo

Palpation is defined in the Oxford English dictionary as "[to] examine (a part of the body) by touch, especially for medical purposes". 

My submitted paper involved a bio-inspired approach to electromechanical device design, where the finger motions of surgeons were studied during exploratory scenarios in order to set a number of functional objectives for the device. The other design requirements were set by the proposed application of minimally invasive surgery.