With new tyres and a tweak to the acceleration profilers it is time to grab some data from Decimus again. The tyre seem to give me reliable grip up to 4m/s/s. They will probably manage more but I seem to have other control issues then. In any case, a dusty maze will soon put paid to that. For this trial, the mouse was commanded to move forward 4 squares with no limit on its top speed…
The Pit Shimizu tyres arrived today. I had to order them from Hong King and they took a week or so to arrive. These are PS-0300 according to the label and have 15° Shore hardness. This is a bit harder than the PN racing set that came the other day…
All fools day it may have been … but not at the Open University headquarters today in Milton Keynes. The ‘Robotics in the Curriculum’ event was attended by a variety of people from the commercial and education worlds. Looking for ways to develop the use of robotics in education, there was plenty of experience to be shared. I was there showing off micromouse and the related schools competitions to pretty well anyone who would stand still long enough to look interested…
For consistent results, the sensors on a micromouse need to be carefully aligned and then fixed in place. In a perfect world, the emitters would all have the same radiation pattern and would generate the same amount of illumination for a given current. Well, that is never going to happen without hand-picking the devices. That would take a long time so we make do with what we have and work around their limitations. Similarly, the detectors have variations to cope with as well. The first step is to get the emitters lined up and pointing where they should…
These new soft tyres are so soft that it is difficult to get them onto the wheels without stretching them way out of shape. No matter how hard I try, they still run unevenly. Some of that is due to the tyre itself but mostly it is just a question of trying to spread the tyre evenly. After several attempts, I gave up and decided to make a small tool to help me with the job…
That was quick. One of the new sets of tyres just arrived. They are the PN racing 8 degree slicks. I ordered them 3 days ago from Kenon Hobby in the US. These tyres certainly are soft and sticky so I put a pair straight on the test rig and compared them to the tyres I have now. They seem to have about 20% more grip than the current ones. This was encouraging so I mounted them on the micromouse. That is when the first little issue came up…
This micromouse thing is a bit tricky. I have not been happy with the accuracy of the results I have been getting with Decimus. Occasionally, a move is significantly shorter, or longer than intended. Looking at the code does not help – either the code is fine or I just follow the same thought process leading to the same errors every time I look. There is, however, something odd about the encoders.
The National Space Centre is having a robot weekend in May this year: See robots from the TV series Robot Wars Compete in the battle arena Take part challenges to test your skills and win prizes Build and test your own robot, including the new LEGO Mindstorm Support your team…
It is true, I am losing my grip. A while ago I posted a link to a Japanese site demonstrating the grip available from a particular micromouse. A common way of doing this is to lock the wheels and place the mouse on a tilting surface. As the slope of the surface is increased, the downforce available to the tyres is progressively reduced until the mouse slips. Part of the downforce is lost due to the angle alone and is proportional to the tangent of the slope.
In general the dsPIC is well blessed with peripherals. The dsPIC30F6015 I am using at the moment has two serial ports in addition to a couple of SPI ports and an I2C port. These UARTs seem pretty easy to use as well. Still, like other peripherals on the dsPIC, they still found a way to catch me out. My own fault for not reading the data sheet properly. The trick here is to realise that there are FIFO buffers associated with the ports.