11
votes
If I must fly my drone in bad weather, how can I maintain control of it in strong winds?
In controls this is known as disturbance rejection. In order to sustain your motion in the presence of high winds you need the controller to be as responsive as possible, and an accelerometer would ...
- 4,376
11
votes
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Quadcopter PID Algorithm
The glaring issue I see at the moment is that you are forcing polarity on the I and D terms. In general, you are using a lot of sign checks, sign assignments, and conditional programming.
None of that ...
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10
votes
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How can we use the accelerometer for altitude estimation?
The barometer carried on the pixhawk has an altitude resolution of 10 cm. If that isn't enough, you could write a kalman filter that uses the accelerometer data in the prediction step and the ...
- 1,833
8
votes
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How to calculate quadcopter lift capabilities?
Similar answer to this post:
Choosing motor for a tricopter
This depends on what you want to do with your copter.
Hovering: 100-150 Watt/kg
ScaleFlight: 200-300 Watt/kg
Some chilling acrobatic ...
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7
votes
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Stabilizing a Drone
Gyro is needed to stabilize angular acceleration. Knowing only your attitude, drone doesn't know how fast on which axis is rotating, knows only where is gravity ...
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7
votes
Explanation of Quadcopter Dynamics, Components and Control
A couple things, the first is that the controller does not really care what the "real" values are. Everything is relative, if the controller sees that it is sinking it will increase the thrust until ...
- 1,909
7
votes
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What is the purpose of these grey balls on the drone?
These are markers for a visual Motion Capture system. Buy some markers here
Most MoCap systems work by setting up multiple cameras with strong IR-Flashes and IR-Cameras and the surface of the balls ...
- 1,355
6
votes
Paradox: I can't use accelerometer measurements to obtain information about my states in a quadcopter?
If the drone is not falling (holding height in the sky), and it's not accelerating in any particular direction, then the accelerometer should be reading:
$$
a = \left[ \begin{array}{}
g_x \\
g_y \\
...
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5
votes
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How do safety cages around quadcopter rotors/blades affect lift capabilities?
To what degree are you looking to cage the fans? IP code gives some grades for fan protection, which may help you decide or even find some stock guards. Level 'A' protects against striking by the back ...
- 15.9k
5
votes
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Arduino or Raspberry Pi?
For interfacing with a camera, I would recommend the Pi. The reason is that the AVR in the Arduino is an ordinary processor, whereas the Broadcom SoC in the Pi was originally designed for multimedia. ...
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5
votes
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What's wrong in controlling Roll+Roll rate in a quad-copter instead of using 2 separate loops for each?
That only works when the desire roll angle is 0. What happens if you are trying to turn and have a desired roll angle of 1deg? Even changing your sum to match the angle error, $w_1 (\theta - \theta_d) ...
- 2,774
5
votes
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What flight firmware stack is most common in aerial robotics research environments?
It is usually a combination of 2 different pieces software. Generally a higher level software which implements most of your autonomy, advanced navigation algorithms, and a lower level software which ...
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4
votes
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Quadcopter frame design
A frame in that configuration or any other witch holds the props in a square without being unbalanced would work, the reason that most people do it with cross bars is because the FC batteries and ESCs ...
- 1,909
4
votes
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how to implement and code inner and outer PD controllers for quadrotor for position tracking
As extension to this answer, I'd like to share with the community a Simulink model implementing the system described above. It does not represent a solution for the code reported by CroCo but it may ...
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4
votes
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Quadcopter - is iPhone the ultimate flight controller?
Speaking from experience, smartphones (android in my case) do work as flight controllers but they have significant drawbacks
The operating system gets in the way. You don't have root access and can't ...
- 2,774
4
votes
Trying to calculate the Thrust of my quadcopter motors
Thrust is a force. You probably have a device in your house to measure force: a scale, so why not determine the thrust empirically?
Build a little mount to place the prop on a scale securely.
Tare ...
- 1,425
4
votes
What exactly are PPM controlled ESCs? Are most ESCs available to build quadcopters PPM Controlled?
I believe there is confusion about these terms. Strictly speaking, the ESC is PWM controlled. Although the signal usually gets there from a transmitter and receiver signal that is PPM encoded.
It ...
- 1,047
4
votes
How to have a 'Auto Go Home' feature, like the DJI Phantom 3, on a project built quadcopter?
I would go with one of two-ish methods to do this, but both methods require the craft to know its own position. You could do this with GPS, or an IMU, or any other means or combination of position ...
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4
votes
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Will a 5200mAh 30C 22.2V 6S Lipo battery work with
Your motors are rated for 466W max, which with a 6S battery gives about 20A max current draw per motor (This also tells you your ESC are a good choice, provided that they can handle the 6S voltage).
...
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PID Control: Integral error does not converge to zero
I don't think this is related to integral windup at all.
I noticed that the I-error does not converge to zero
That's a good thing, because it means your integral term is not useless.
The integral ...
- 1,425
4
votes
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Quadrocopter PID
Technically, you can do it either way, but consider the following scenario: You are flying with a heavy load, and there is a wind gust. Each rotor is operating at almost 100% capacity due to the heavy ...
- 15.9k
4
votes
How to compensate the brushless DC motor for voltage drop?
STOP USING YOUR BATTERY IMMEDIATELY!
First of all you shouldn't let the voltage of a lipo battery drop below 3V per cell which in your case comes to 12V. Lipo Batteries are extremely dangerous and ...
4
votes
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Holonomic and Non-holonomic UAV's: Gliders vs Quadcopters
The glider definitely is a nonholomonic system, but not (only) because it has no propulsion.
As Wikipedia defines it:
A nonholonomic system in physics and mathematics is a system whose state depends ...
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Paradox: I can't use accelerometer measurements to obtain information about my states in a quadcopter?
I encountered the same puzzle. I had a clue at the beginning that the gravity information is contained within accelerometer measurements due to aerodynamic drag. Then I found a paper The True Role of ...
- 56
4
votes
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Detection of linear acceleration vs rotational velocity/acceleration
The IMU itself cannot distinguish between "true" linear acceleration and "fictitious" (Coriolis) linear acceleration induced by rotation of the IMU coordinate frame with respect to ...
- 245
4
votes
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What is the consquence of Gimbal lock?
I made a clip for you (https://imgur.com/a/KPeQ7Ia) using Unity, which internally represents rotations as quaternions, but uses Euler angles for display and positioning.
You can see that, at zero ...
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3
votes
Quadcopter frame design
To answer your questions directly, the X-shape is not the only design that will work. There are many variations of frame design around a number of rotors that can range from 3 to (in some cases) 8.
...
- 11k
3
votes
How to use quaternions to feed a PID quadcopter stabilization loop?
This paper, Full Quaternion Based Attitude Control for a Quadrotor by
Emil Fresk and George Nikolakopoulos, demonstrates what you are trying to achieve.
Abstract— The aim of this article is to ...
- 31
3
votes
How to estimate yaw angle from tri-axis accelerometer and gyroscope
yaw can be measured by rate gyro and magnetometer not with accelerometer because accelerometer values depends on gravity component but on rotation in z axis only there is no change in gravity ...
- 31
3
votes
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thrust measurement
Okay I thought I'd move this to an answer because I think this will help clear up some confusion you have.
First, if you are trying to plot RPM vs Thrust, then your battery, ESC, power, etc. have ...
- 15.9k
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