# Tag Info

9

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 from several sensor. A voter decides the output(final) value. Boing 777 has 6 sensors for each function. Safety and critical systems: if one sensor fails, ...

9

Let's look at how a quadrotor flies, then apply that to a trirotor. Let's assume that we want to remain in a stationary hover position. To do that, you need to balance all the forces: thrust from the propellers vs. gravity, and the torques of each motor. Each motor produces both thrust and torque according to the equations: $$T = K_T\rho n^2 D^4$$  Q = ...

5

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 such a way that they move to reduce the error thus obtaining the desired orientation So the right order is: Read RX signal Calculate desired pitch, roll, ...

4

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 are just the opposite in order to achieve fast maneouvres, among other reasons. Read this aviation thread where this question was replied.

4

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 null speed - when the system has only one input variable, let's say the "thrust" driving the UAV dynamics. The correct scheme should be the one depicted below: ...

4

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 on the path taken in order to achieve it. So, if an aircraft can reach a pose (position and orientation) in space regardless of its prior states (path taken) ...

4

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 - at least I couldn't find one less than \$100, ten times the price of a 50kg digital hanging scale. You will need to do some analog conversion and amplification ...

3

The mechanical answers above are correct. The inherent stability problems with single large motors are exchanged for dynamic comtrol over 12 dimensions of acceleration, yaw, pitch, roll which can be partially coupled (the translational amd rotational matrix) where one is presented with a simplified diagonal inertial frame to build a dynamic model with. In ...

3

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 other modules and doesn't offer a terrific amount of content on its own. This means you get to buy Simscape, then buy whatever other toolboxes you want that ...

3

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 designed to use the LSM303D chip, as it was supposed to be better. Initial prototype testing of Pixhawk boards revealed problems with the LSM chip. To avoid ...

3

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 integrate acceleration to get velocity, and then integrate velocity to get position. The problem with this though that any drift/error/noise on the ...

3

Telemetry is used to get in-flight data back to a ground station. For example, attitude (roll, pitch, yaw), altitude, GPS position, speed, battery voltages. It just gives you more feedback. It can also be used to alert you when battery levels are too low or when a fault occurs.

3

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 fact that they must maintain some forward velocity that is related to its bank angle. Aircraft motion planning typically also contains maxium g force ...

3

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). You may also want to check out this survey paper.

3

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 in a known starting position and orientation (position + orientation = "pose"). Capture IMU accelerometer and gyroscope readings. Use numeric integration on the ...

2

The LEDs on the board indicate the status of the Ardupilot. See the LEDs on the boards on the Arducopter wiki for more detail. Of interest to you are likely the A (red), B (yellow), and C (blue) LEDs. LED A is solid when the motors are armed and blinks otherwise. LED B flashes while the Ardupilot calibrates. Finally LED C indicates the status of the GPS ...

2

This depends on a few things. First of all, are you using ArduPlane or ArduCopter, and what mode are you in? For ArduPlane, your answers are here, and for arducopter, here. In both cases, the software has safeguards that will not let you arm or start the motor while it is initializing. In both cases, the LEDs indicate when it is ready to arm or fly. Of ...

2

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 implment whatver it is that you are trying to do. Normally a quadrocopter will drift a certain amount, you would want some kind of external position input ...

2

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 position. You might still be able to reduce the amount of drift a little: Make sure that the center of gravity of your quadrotor is actually in the center. If ...

2

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 something to adjust the roll/pitch PIDs. Try tweaking them. Under-compensated integral error may be a possible culprit. Some issue with ESC calibration. Try ...

2

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 on them? First, I'll say that system response, stability, etc., are all based on mathematics, and math does not have feelings. That is, a system doesn't "...

2

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 filter or heaven higher to generate a smooth trajectory up to the n-th order. Typically in my lab we try to impose up to smooth jerk or snap, for high agility ...

2

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 example, putting 3” props on a motor designed for 5” propellers will result in extremely high RPM and power draw and will create very little thrust. Likewise, putting ...

1

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 sensor to know its orientation and its altitude (using a pressure sensor). Chuck is correct in saying that a quadcopter only pushed thrust downwards. The ...

1

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), then you need to write to each motor individually. There are other problems, too - read on for more. In looking at your code, I found a couple points where ...

1

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 to set it to /map or /world, depending on what the name of the frame is that the package provides. The list can be seen in the dropdown menu of fixed frames. ...

1

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 neutral position (of stick of the controller for example), 2ms max and 1ms min. Unfortunately when I connected my microcontroller to the CC3D I wasn't able to get ...

1

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 one unit of "forward" in the world. However, when the robot is allowed to rotate, one unit of "forward" for the robot now corresponds to a partial unit "...

1

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 one that can handle full power (200W per motor so 800W total for a 12V*3Ah battery=>36Wh so that's 800/36=22C) so a 3S 3000mAh 25C constant LiPo would be perfect ...

1

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 possible, given only the angular camera measurements. Possible solutions: If you have two images with a known relative position between the two, then you can ...

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