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Tri Motored UAV
Submitted by Razor Concepts on September 17, 2008 - 4:31pm.
WORK IN PROGRESS
The project is to create an autonomous three-motored helicopter style UAV. An Axon will be used to process everything. In the beginning, I will be using Teleoperation (look under the RC tutorial) to allow me to test certain things at a time. As of 9/17/08, I have this:
The RC transmitter and the current test craft are shown. The transmitter is a Spektrum DX7 7-channel spread spectrum radio, currently the test craft is using a 6-channel half range receiver. Should the need arise, I can exchange receivers from one of my recreational helicopters, which uses a 7 channel full range receiver.
The test craft itself is manufactured by LaHeli in the Czech Republic. Before LaHeli began producing these a year ago, only a few tri-motored craft existed, and all were home built with varying sucess rates and flight characteristics. The main problem was the gyroscopic stabilization, which LaHeli solved by producing a small stabilizing unit that automatically mixed the 120 degree CCPM mixing for the motors, and has two small gyros to stabilize the craft.
I plan on removing the stabilizer, and replacing it with the Axon. The existing stabilizer does its job fairly well, but it wont be suitable for a UAV test platform, as the gyros are not accurate enough. However my first goal will be to insert the Axon in between the reciever and the stabilizer, to see how well the Axon can handle processing the signals from the receiver. The time between input and output should not exceed 100ms, or else the speed will be too low, and hinder flight ability. The current electronics have a delay of less than 40ms, and hopefully the Axon should not increase it by too much.
The Axon will be the central microcontroller, the thing that makes all of the decisions. Other microcontrollers will feed data into the Axon. The reason I am planning to split tasks to different microcontrollers is because certain peripherals need or return data at a certain time interval (servos every 20ms, compass sensor every 50ms, etc). Using the Axon as the central brain eliminates the need to focus on timing issues on the Axon. The other microcontrollers (Robodruino) will do a variety of other timed tasks. One will read data from the receiver and pass that data to the Axon, and it will do double duty - the Axon will send data to it and it will control the speed controllers and servo. A second Robodruino will handle the sensors, supplying the Axon with a constant stream of data so that the Axon won't have to sit around waiting for data to arrive.