Sunday, 9 September 2012

Delayed Test.

We have a new member to the group. Bart Hertog is a control systems engineer living in the Netherlands. Bart will be working on the vehicles control system and implementation.

Bart has designed a system that is based on two PI loops for roll control. There is a inner velocity loop that takes roll rate and an outer position loop that takes absolute position.

The plan was to test/tune the velocity loop on Sunday (yesterday) but after a full day of programming on Saturday I was tired, frustrated and starting to make mistakes so I decided postpone a week rather than rush to test something that was not ready.

Bart also had a really good idea to stop an auto hover if the roll/pitch became greater than 45 degrees. This is a really good safety mechnism.

If you think of the output from the control loop as a desired torque the main problem so far has been how to best convert the torque into 3 thruster forces in a way that maintains the desired thrust and also stays within the limits thrust that the thrusters can actually produce. Also the fact that we don't know exactly how much thrust the thrusters can output doesn't help.

We still need to make a proper battery mount to avoid the last minute duct tape we used after the battery came loose last time.

Buren has re-made the remote quick-disconnect with two solenoids which seems to work well so we shouldn't need to use the line cutter for the next test. He has also made a counterweight system so the solenoid and line will be automatically pulled to the top of the test stand after it is disconnected from the vehicle.

Nick is currently looking into a RTK gps system. He wanted to use a beagle board as the fixed base station but I would prefer to just use a computer. We will probably want to get another data modem just for the RTK system.

Sam is working on the control GIU which sends strings out via serial.

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