# Tag Info

Accepted

### Why does the Pixhawk have 2 IMUs

Generally engineers implement dual, triple or more sensors with the same function for one or more of the following reasons: Reliability: the system should be reliable. Several values can be fetched ...
• 408
Accepted

### Will this pseudocode work as a basis for a flight controller?

The signals to the ESC's using PWM should be sent after the PID algo is done processing the errors. The output calculated from the PID is the PWM value to be sent to the ESC's to actuate the motors in ...
Accepted

### The aerial refueling problem: sketch of a feedback controller

Both the solutions you proposed do suffer from unwanted interaction among the two PIDs. You're basically trying to assign two simultaneous goals - i.e. final relative position along with terminal non ...
• 3,555

### Fixed Wing UAV: Do inherently unstable systems desire to be stable for all cases when a closed loop control is implemented on them?

Not all fixed wing aircraft are inherently instable. That feature greatly depends on the center pressure and gravity center designed position. Passenger aircrafts are quite stable, and fight planes ...
• 440
Accepted

### 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 ...
• 6,412
Accepted

### How to measure pull force on a (kite) rope?

The component you highlighted is called a tensile load cell. You could buy one from a supplier, but it probably would be cheaper to buy a cheap digital hanging scale and taking the sensor out of it - ...
• 501
Accepted

### what is the algorithm to get position (Linear displacement and linear velocity ) using IMU (Like MPU6050)?

I thought for sure that there would have been a duplicate question somewhere on the site that answers this question, but I can't find one, so here's a quick description of the method. Put your IMU ...
• 14.7k
Accepted

### Is MoveIt! suitable for fixed-wing aircraft path planning and obstacle avoidance?

Not really MoveIt! is designed for robotic arms, and is being heavily adapted for the applications you see here, fixed wing aircraft typically use very diffrent types of motion planning becouse of the ...
• 1,909

### Generate a coverage path given a polygon region

This thing is generally called coverage path planning. If you are particularly interested in Boustrophedon Cell Decomposition, you may have a look at the paper introducing it: Choset and Pignon (1998)...
• 1,799
Accepted

### Are there any aerodynamics modeling/simulation software that is capable to consume a SolidWorks model and to interface with MATLAB/Simulink?

Matlab has a package called Simscape that you can use for modeling physical systems in general. I would just caution you up front that Simscape is almost more like a plugin manager in that it enables ...
• 14.7k

### Why does the Pixhawk have 2 IMUs

This was on rcgroups: Reply by Rob_Lefebvre on December 31, 2014 at 7:02am Here is a brief history: The APM class boards used the MPU6000 gyro/accel chip. The Pixhawk was originally ...
• 31

### Displacement with accelerometer

This will depend on what you mean by "displacement" and for how long you want to do this. Can you supply more details on what your trying to accomplish and why? As Bending Unit 22 mentioned, you ...
• 106

### Implementing a position control for UAV through a flight controller. Plant model is unknown

What is your final desired result? You will certainly want to switch to a different Flight controller like the Pixhawk it will allow you mutch finer control and allow you to reprogam it at will to ...
• 1,909

### Our quadcopter goes forward instead of hovering in place. How to correct it?

You seem to be controlling the quadrotor's attitude (roll, pitch) to (0, 0) and not its position. What you are seeing is drift in position, which is inevitable if you do not control the quadrotor's ...
• 629

### Our quadcopter goes forward instead of hovering in place. How to correct it?

There are quite a few possible explanations for the instability, I'll try to list 'em: PID settings are off the mark. I'm not familiar with KK2.1.5 Multi-Rotor controller, but I'm sure there will be ...
• 409
Accepted

### Fixed Wing UAV: Do inherently unstable systems desire to be stable for all cases when a closed loop control is implemented on them?

I'm going to ignore your section on aircraft and attempt to answer the (vague) question, Do inherently unstable systems desire to be stable for all cases when a closed loop control is implemented ...
• 14.7k

### Generation of a trajectory (position,velocity,acceleration) from velocity

With the method you describe you are bound to have non zero velocity or non acceleration (based on if you consider a + pi/2 offset or not). Despite @combo answer I would suggest you a second order ...
• 1,327

### How is the IMU used in the PixHawk?

Take a read here and here. The Flight Management Unit (FMU) board and the IO board combined make a Pixhawk autopilot. The FMU is contains the control logic and the sensors while the IO takes care of ...
• 510

### Are all drone propellers compatible with all brushless motors?

Not at all. It is about efficiency, agility, and maneuverability of your drone. Just like wheels on a car, the size of the propeller needs to be matched to the rest of the power system. For ...
• 96
1 vote

### How to implement a novel control algorithm for a drone

Assuming you know how to model a regular quadrotor as $\dot{x} = Ax + Bu$, the only difference with the addition of the extra propeller will be in your control matrix and control vector (one more ...
• 71
1 vote

### How many independent control inputs does a hexarotor have?

When assuming that the axles of all the rotors are oriented parallel to each other then the thrust will also only be along the same direction as these axles, so this only adds one degree of freedom. ...
• 931
1 vote

### How to convert raw Pitot tube readings to air speed in m/s?

In a classic pitot tube setup, we make use of a liquid (density $\rho$)in a U tube. One end of the U tube is connected to the dynamic pressure source (front of the pitot) and the other end is ...
• 41
1 vote

### CC3D PWM control signal characteristic (to be simulated by Raspberry PI)

Ok I actually was able to make it work. First of all in the beginning of the testing I used my own program which generated PWM signals. I wanted to make them 50Hz with 1.5ms of duty cycle being ...
• 31
1 vote
Accepted

### Estimating the displacement of a drone in three dimensions

If the robot's orientation is fixed, then determining its linear displacement is sufficient to determine its location in the world. This is because one unit of "forward" on the robot is equivalent to ...
• 14.7k
1 vote

### Possible stabilize Crazyflie 2.0 drone autonomous flight without additional sensors?

You will not be able to achieve stable horizontal flight without external sensors. The reason is that the Crazyflie 2.0 quadcopter does not have sensors to know where it is in the room, it only has ...
1 vote

### Possible stabilize Crazyflie 2.0 drone autonomous flight without additional sensors?

tl;dr - You can't control the aircraft's side-to-side motion because you are only modifying "thrust", which controls the up-and-down motion. If you want to control roll and pitch (side-to-side motion),...
• 14.7k
1 vote

### Utilizing the inertial sensors in an AR Drone

That's because your fixed frame is set to /odom (Essentially, you're setting your global frame to your local frame, so relative to the vehicle itself, the vehicle never moves!). The solution would be ...
• 1,091
1 vote

### Compatibilty of my setup?

The website that you have used seems to be down, however looking at the specs announced on banggood, it looks compatible. You would need some 8*4 props and a 3S battery, I'd advise getting a 3000mAh ...
1 vote

### Vision-based Position Estimation for a quadrotor

Because a camera is a range-only sensor, you cannot directly estimate the relative position of the object. Additionally, because you have only one object, there are infinite solutions that are equally ...
• 872
1 vote

### Vision-based Position Estimation for a quadrotor

It's odd that you're suggesting computing the position of a landmark. Literally, a mark on the land -- a position that you should already know and will use to localize your vehicle. You can give it ...
• 10.8k

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