Posted by Tom Oldfield on October 21, 2009 at 2:23pm
Hi guys!I've picked up this new project. Basicly improving a quadcopter system, totally redoing it.At the moment im using a arduino duemilanove board that has a ATmega168 microcontroller. It has Accels and Gyros giving me 6Degrees of Freedom. I have plans to attach a GPS unit as well, after IMU has been done.Currently working on the IMU. Just got a bit of a problem getting my head around it. Im not going to FULLY use Ardupilot since i want my IMU to be automatic calibration, i want it to be a full control system self sufficent on its self (in the future i want to take off on its own and controlable via laptop). I have looked around a lot and people have suggested kalmans filtering but im still confused. Do I take the Outputs from accels/gyros and "input" them into the kalmans equation? What do i do with that output?Any help and advice would be awesome, i've already looked through kalmans filtering on the web but it still confused me inrelation to IMU quadcopters.Thanks again,Tom
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If you have Kalman Filters on the pitch and roll axis fusing the accelerometer and gyro data, then a PD control routine on the pitch and roll axis is what's needed to balance the platform. For example, on the pitch axis the angle from the Kalman Filter is the difference between the desired angle (set point) and the current (measured) angle of the platform, and the rate from the Kalman Filter is the unbaised rate. The angle difference (error) is the Proportional input to the PD controller and the unbaised rate is the Differential input. With the right gains set (Kp & Kd), the PD controller will drive the angle error to zero so the platform maintains the angle set point. If you want to hover, set the angle set points in pitch and roll to zero. If you want to set the platform in motion, then set the pitch and roll angle set points to something other than zero.
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