Hot answers tagged

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

Am I correct in saying that this would not require a gyro, just a 3 (2?) axis accelerometer, to detect pitch and roll, then adjust the ailerons and elevator to compensate? No. The opposite is true. The accelerometer will be almost useless to detect rotations on a platform that's experiencing unknown accelerations. Your plane will be subject to two force ...


5

As the name of the accelerometer implies, you measure the acceleration on your system excluding that from the gravitational force. When your sensor is at rest, you measure the acceleration from the force that you use to counteract the gravitational force. This is how you can fix your orientation vs the gravity vector. When the sensor is accelerated, as would ...


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

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

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

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

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

The glider definitely is a non-holomonic 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 aicraft can reach a pose (position and orientation) in space regardless of its prior states (path taken)...


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

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

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

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.


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

I think you're mixing two meanings of the word "sensitive". Input Sensitivity If you have an IMU that gives very raw ("twitchy") readings, then you should be able to generate the output of a less input-sensitive IMU by simply computing a moving average or using a Kalman filter on the output. This will produce an effect similar to running a low-pass ...


2

If I'm understanding your architecture (from joystick to UAV) correctly, it is this: ${[\text{joystick}]-\text{wires}- \atop [\text{RPi}]-\text{USB HID}-}-[\text{Nano}]-\text{XBee}-[\text{UAV}]$ You're considering laying it out like this: $[\text{joystick}]-\text{wires}-[\text{Nano}]-\text{USB HID}-[\text{Rpi}]-\text{USB HID}-[\text{Nano}]-\text{XBee}-[\...


2

The Arduino Nano should be able to interface with the XBee no problem. If all you are using the Arduino for is forwarding a message that comes from the RPi, you might as well just use an XBee Explorer board (basically a FTDI Chip with a socket fit for an XBee). After configuration, all you need to do is to write to a serial port to get the XBee to send a ...


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

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 ...


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

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

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

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 ...


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