Cool Engineering

Info on some cool engineering projects

Tuesday, September 30, 2008

Bus Addressable Motor Driver

Information on the motor shrouds is coming but will be delayed another couple of days as I didn't follow the measure first rule and made them too small to fit over the propellers. The new 100mm shrouds have now been made and will be fitted in the next few days.
On the topic of motors - another interesting little board inside the ROV is the motor control board. I decided to make this generic as possible so it can be reused in different vehicles (including my PhD project!) in different conditions with minimum overhead.
Here are the specs:
- Bi-Directional motor driver up to 4A (implemented using a H-Bridge made up of FETs) (with heavier wiring we could go higher)
- Microprocessor driven
- H-Bridge shoot-through logical prevention
- Bus operated - connect up to 4 on the same bus line and refer to each by a different address
- With the flick of a switch it accepts a direct PWM and direction signal rather than the serial addressed scheme
A website for this has been thrown up too.

Monday, September 29, 2008

ROV braves the Moat

The ROV has officially been in real water (not including the bathtub). The first testing ground was the Professor's swimming pool and the follow-up test was in the University moat system.
The initial tests show both positive and negative results:
The good:
- No leaks were encountered at all - the ROV was taken down to a maximum depth of 1.7m and was underwater for approximately an hour in total - not a single drop of water was found inside.
- There is ton's of bouyancy to play with - we literally had to add approximately 3kg of extra weight to make it neutrally bouyant
- The ROV moved around under computer control as expected
- A great crowd attractor with many people particularly at University coming up to take a look and ask questions (and offer advice!)

The not-so-good:
- The ROV was quite slow (see video). In the first test this was due in part to the batteries not being installed correctly. It still seems to be an issue and so we probably will need to swap the NiMH batteries with the SLA that we had originally planned on using with a lower internal resistance
- It was really heavy - with all the extra weight - I'm considering replacing our big ballast tanks with some stabalising foam and we should be able to reduce our weight significantly - hopefully allowing it to be a bit faster
- The propellors had a habit of catching weeds and junk (leading me to finally build the propellor guards - to be discussed in the next post)
To do:
- Fit propellor guards
- Re-adjust bouyancy to ensure overall load can be lightened
- Trim off to neutral bouyancy using lead sinkers ($3.30 from Kmart)
- Fit SLA 12V 3A Battery
- Retest
The sports centre at the Uni has given permission to perform testing in the deep water section of the pool (2.8 m from memory) but that won't be to mid next week - they are draining the pool for the break - so until then we will be testing probably in the moat or other swimming pools.

Sunday, September 28, 2008

POV and Project of the Month

The previous post mentioned the POV project whilst lacking some detail or any conclusion for the matter. The POV project was completed and looked really great on open day. Unfortunately we ran out of time to get the wireless updates running but is successfully wrote LA TROBE pretty clearly through the lab causing lots of people to point and stare. A page on my website has now been created for the POV.
This project was the first of a new initiative which has been named 'Project of the Month' - for lack of a better name. Basically it is a staff/student mentorship program which aims to address three key areas:
- Many staff have ideas small projects they would like to create but don't have the time
- Many students want extra project experience but need some direction and motivation and will benefit hugely skills wise
- The more presentations at Open Day the better - and many of these types of projects would be more than suitable
I supervised the first 'Project of the Month' and a rather bright third year student (Duc) completed the project. It is preferrable to keep the projects short so that it doesn't interfer too much with other academic activities for both staff and students. Right now I have half a whiteboard full of project ideas - so it looks like it will be a fun summer.
If anyone has any other ideas for a short project please send them through.

Saturday, September 27, 2008

Open Day Reflections

How quickly the time has gone already nearly a month since La Trobe Uni Open Day.
We had about 7 engineering displays in total:
- The UAV
- The ROV
- A line tracking robot
- A Persistence of vision sign writer
- A traffic congestion Zigbee and GPS based monitoring system
- Some fancy image recognition for speed signs
- A waveform generator
When people walked in they were often really interested in moving things and interactive things - the POV and line tracking robot in particular attracted lots of attention. Unfortunately the ROV and UAV as cool as they are were simply static displays which weren't too exciting. Next year we will aim to have more interactive and visually stimulating projects, in particular some we have earmarked include:
- A hexapod insectoid robot
- A horizontal 3D POV display
- A PID balance beam or inverted pendulum
- My PhD research on SLAM (Simultaneous Localisation and Mapping)
- An active ROV display (people control the ROV)
- Mini-ROV's in a fish-tank (from the schools program)
- High altitude balloon research
- Quadrature rotor chopper