Actuators workshop held in London on 2-3rd of February

Posted 02 Feb, 2008

Tinker.it notes can be found here: www.tinker.it/en/Teaching/Actuators

Intro notes

Mechatronics
Non-magnetic actuators used in MRI machine (piezo).
Human reaction - we are tuned to recognise natural movement.

Gordon Pask

Cybernetic Serendipity 1968 (ICA electronic art) Gordon pask. Later toured US & Canada at the Exploratorium.
SAM (Sound Activated Mobile) - early senstor. Had to 'talk' to it in a steady murmur in order to atract its attention.
Examined animals for types of movements - Lobster leg.
Senstor looked scary when going through its test routine i.e. moving in its rigid way.
Hydraulics very quiet as pumps can be placed remotely.
Behaviour rather than appearance is important.
Evoluon - spaceship event.
Machines need maintenance.
Senstor in Holland on blocks.
Possibly one of the biggest computer art commissions.
Employed by UCL.
Recorded movements & from those movements could statistically identify if you were male or female.

People

Simon penny - artists - autonomous robot.
Ken Rinaldo - artist - dried grapevine. Cables create movement. Infrared sensors to detect movement. Sound sensors. MAchines whistle at each other. Fish in bowls move around.
Yves Amu Klien - Octofungi.
Driessens & Verstappen - Tickle Salon. Tassel strocks & builds a model of the person laying down.
Paul Granjon - Low tech robots. Sexed robots. Robustly built. Big battery.

The only maths you need to know

Voltage = Current * Resistance. (V=IR)
Power = Voltage * Current (P=VI)
Power = Current2 * Resistance (P=I2R)
Torque measured in Newton meters: (needed to spec installation).

Very useful function - Constrain number range

int rangeAdjust(float oldMinVal, float oldMaxVal, float newMinVal, float newMaxVal, float currentReading)
{
float ratio = (currentReading-oldMinVal)/(oldMaxVal-oldMinVal);
float newValue = ratio * (newMaxVal - newMinVal);
newValue = newValue + newMinVal; // bump up the figure into the new range
return newValue;
}

Actuators

Solenoid - Linear motion. Digital action.
To drive 8 actuators use ULN2803 (has 8 transistors & diodes built in 500ma per channel)
Centrifugal fan for inflating fan
Speaker: 2 mirrors with laser.
Floppy drive (linear motion)
Hard drive head (make jumping robot.)
H-Bridge - L293D
Can make true analog output with resistor & capacitor - make an oscillator display an image.
Servo: can get metal ones. Lots of different types.

Shops/Materials

TP.org (for pump)
Power supply from Rapid. £60.
BOOK: Robotics, Mechatronics & artificial intelligence.
BOOK: Muscle wire.

Detecting position of motors:

- Could use a cam to count spins i.e. cam makes switch go on one rotation.
- Slots on a disk to count spins (optical encoder).
- Slotted opto switch (found in printers etc.).
-

Stepper motor

1. List wires & measure resistance between pairs to work out which are connected.
Standard degree shift: 1.8, 7.5, 15, 30

Accelerometer and Servo example

Accelerometer / Servo example

The Anthill Social