I have decided to rebuild DARSU, this robot was one of the more powerful robots I have built mainly because of the motors I obtained.
There were a couple of issues with DARSU such as the motor controller made from 4 relays, the wheels made from wood, and the poorly shielded electronics which kept crashing. The aim is to fix all of these problems and produce a well built, strong and powerful robot base which I can then use for future projects.
I am going to use the same 24v geared down motors I used in the previous robot, these are fairly low powered drawing less than 5A but they are very powerful.
I have found some pneumatic rubber tyres on eBay, these are 10" in diameter so they are a little smaller than the original wheels but they will hopefully stop a lot of the vibrations and knocks as they will be fairly springy. The only issue with these wheels is that they have bearings inside making attachment to the motors difficult, to fix this i have designed a simple bracket thing which fits inside the bearing and bolts onto the wheel hub, this then allows the main shaft to pass though and bolt together.
Instead of using relays again or building my own motor controller I have opted for an of the shelf one. I have selected the Motion Mind motor controller as it isn't to expensive, it has a decent current rating 9A and has a wide range of interfaces from a direct switch control, to a serial interface.
I will mount two of these (one for each motor) in a steel box mounted below the chassis at the rear of the robot. As these are one of the key systems they are going to be securely and permanently mounted although they can be replaced in case one breaks. I will try and make the box fairly water proof so if it drives through a puddle or gets wet it wont break.
For more information you can follow the link below to the shop where I bought them.
Active Robots - Motion Mind Controller
I have decided to run the motors at their rated voltage of 24V unlike last year when I was using them at 12V. I will have 4 7.2Ah 12V gel batteries; two pairs will be in series giving me 24v batteries these will then be connected in parallel providing a 24V 14.4Ah power supply, hopefully enough to run the robot for well over an hour.
Like the motor controller the batteries are one of the fundamental components so they will be housed below the main chassis in a semi-permanent housing.
I have made the decision to run the robot directly from a computer rather than individual microcontrollers.
The program will be written in Visual Basic (its the only relevant language I know) and will control all the main systems.
I have also added a secondary manual control system; the robot has an Xbox 360 USB receiver attached, the computer program will be setup to allow manual control of the robot using a standard controller.
The robot will be equipped with a variety of sensors which will allow it to move around and detect its environment
GPS - I have fitted a GPS receiver which will allow the robot to transmit its current position back to base as well as allowing it to move from position to position.
WebCam - A webcam will be attached to a servo controlled pan and tilt mechanism mounted on the front of the robot, this will be used for recording video footage and taking photos as well as identifying its surroundings.
Heat Sensor - I have fitted a heat sensor to the webcam mounting, this will allow it to easily identify hot objects such as people or fires.
Range Finder / Proximity Detector - I will have three of these mounted on servos and placed in each corner of the robot, they will each have 180 degree coverage allowing for complete coverage of its surroundings.