Gizmocopter Work Session Notes for March 13th, 2003
The Gizmocopter work session began at 7:00PM. Chris, Bill, David M., Nate, Sean, Michelle, Sarija, and several cats and a dog were in attendance. Dinner consisted of lazagna, and was delicious. The Gizmocopter work session was somewhat muted tonight as most efforts have come to a standstill until the Interface Board -- a PCB housing power, control, and analog interfaces -- is complete. The board will be home to a 5VDC power converter, analog to PWM converters for the primary motor drive circuits, and a general connector interface for the gyro/accelerometer array/cube for Gizmocopter's IMU function. Chris showed the two 2-axis, 10g, accelerometer chips that he acquired from Analog Devices. Additionally, two more Analog Devices gyros (ADXRS150ABG) were purchased for Gizmocopter's IMU during the meeting. We now have parts. Now if we can only get boards...
A few points:
I am looking forward to hearing how the Analog Devices gyros work out.
The IMU functionality should communicate with the CPU over a serial line if possible, so it can be tested on desktop computers as well as the flight computer. If you are just using an existing A/D board on the CPU, it probably isn't worth adding another controller for, but I have often found it very handy to test IMU things on a desktop computer.
The accelerometers are useful as an inclinometer for initialization of the gyros, but you can live without them if you have a level launch pad. Don't expect to be able to integrate accelerometers and gyros for accurate 3D positioning for hovering or auto-land. Even the much more expensive ones I use aren't up to that task at the few-feet precision level that is needed.
Analog to PWM? Does this mean that the flight computer is using a D/A board to generate an analog signal for throttle level, which is being converted back to a digital pulse train for the motors?
John Carmack
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