Hi everybody, howz everyone doing.
With the mathematical and mechanical(simulations) ground work complete we are ready to actually build a Quad rotor of our own with the design specs. from the PRO Engineer/Solid Works model, and actually if I may say even controlling the Quad rotor. Now you might think I must be crazy. Well I just jumped a few steps or you may say a month's preparatory work to give you the good news. For any control technique that you may employ you will need the observation of variables being controlled. That observation will come from the various sensors that you will use. Even if you can't sense all the parameters of the aircraft you will at least need some of them and the rest can be estimated. In my experience if you have 3 angular velocities, 3 accelerations and 3 positions(x, y and z) you can estimate the remaining 6 parameter i.e. 3 angular positions and 3 linear velocities.
Now the problem of sensors is not straightforward. 9 DoF IMUs with on board gyro, accelerometer and magnetometers are available. The output of the IMU consists of acceleration in 3 axes, angular velocity about 3 axes and magnetic field intensity in the three axes. You might think, like we did at first "what the hell, double integrate the accelerometer and integrate the gyro readings and we have all the parameters that we want". It might be true in an ideal world, free of motor vibrations and white noise but not on our beloved planet Earth. Gyros and accelerometers have biases in their output and which compound on integration and with time the results diverge. Although with sensor fusion we can find attitude of the craft i.e. roll pitch and yaw but the same is not true for position estimation. I will be discussing these topics in detail in the next few posts.
Now to the controls portion. Once you have interfaced the sensors with the micro controller that you are using, you can use a simple PID controller and adjust the gains by hit and trial. Although it is a crude approach and one that I am not in favor of but still it works. But before all that fairytale begins you will have to select the motors, the drives, the sensors and estimate the states from them. So stay tuned as there is lots more to come.
Due to the lack of interest in the documents I uploaded along with the last two posts, i am not going to be posting any documents from now on unless required by the post itself. Cheers.
With the mathematical and mechanical(simulations) ground work complete we are ready to actually build a Quad rotor of our own with the design specs. from the PRO Engineer/Solid Works model, and actually if I may say even controlling the Quad rotor. Now you might think I must be crazy. Well I just jumped a few steps or you may say a month's preparatory work to give you the good news. For any control technique that you may employ you will need the observation of variables being controlled. That observation will come from the various sensors that you will use. Even if you can't sense all the parameters of the aircraft you will at least need some of them and the rest can be estimated. In my experience if you have 3 angular velocities, 3 accelerations and 3 positions(x, y and z) you can estimate the remaining 6 parameter i.e. 3 angular positions and 3 linear velocities.
Now the problem of sensors is not straightforward. 9 DoF IMUs with on board gyro, accelerometer and magnetometers are available. The output of the IMU consists of acceleration in 3 axes, angular velocity about 3 axes and magnetic field intensity in the three axes. You might think, like we did at first "what the hell, double integrate the accelerometer and integrate the gyro readings and we have all the parameters that we want". It might be true in an ideal world, free of motor vibrations and white noise but not on our beloved planet Earth. Gyros and accelerometers have biases in their output and which compound on integration and with time the results diverge. Although with sensor fusion we can find attitude of the craft i.e. roll pitch and yaw but the same is not true for position estimation. I will be discussing these topics in detail in the next few posts.
Now to the controls portion. Once you have interfaced the sensors with the micro controller that you are using, you can use a simple PID controller and adjust the gains by hit and trial. Although it is a crude approach and one that I am not in favor of but still it works. But before all that fairytale begins you will have to select the motors, the drives, the sensors and estimate the states from them. So stay tuned as there is lots more to come.
Due to the lack of interest in the documents I uploaded along with the last two posts, i am not going to be posting any documents from now on unless required by the post itself. Cheers.
Thanks a lot for this blog. I am working on a quad rotor project of my own, and this is proving to be an awesome resource. Please continue posting more content.Big ups!!!!!
ReplyDeletei read ur previous tuts but u havnt given complete info , but still waiting for ur next one please fast
ReplyDelete