11
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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 ...
- 16k
10
votes
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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 ...
- 16k
8
votes
Accepted
Why do 3-axis accelerometers seemingly have a left-handed coordinate system?
The answer is that 3-axis accelerometers don't have a left handed coordinate system just for the gravity. In static condition (i.e. if the accelerometer is not accelerating with respect to any ...
- 235
7
votes
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What information an IMU gives to a drone?
You already know the answer - because as you say it contains an accelerometer and a rate gyro.
An accelerometer measures linear acceleration, a rate gyro measures angular velocity. These are the only ...
- 1,041
7
votes
Open source implementations for GPS+IMU sensor fusion?
Yes. The px4 software for the pixhawk autopilot has an extended kalman filter that uses an accelerometer, a gyroscope, gps, and mag.
A paper describing the a smaller ekf which only estimates attitude ...
- 1,853
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 ...
- 450
7
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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 ...
- 1,919
6
votes
Accepted
Kalman Filter GPS + IMU
This is a complete re-working of the answer I had originally provided. If you're curious, you can check the edit history and see what was posted earlier.
In comments to this question, OP stated that ...
- 16k
6
votes
Accepted
How to avoid gimbal with Quaternions
Quaternions are a more efficient way of storing the orientation matrix of a frame.
I use the vector-scalar convention for quaternions (3+1 = 4 quantities) and have defined the following utility ...
- 383
4
votes
Accepted
Angular velocities and rotation matrices
If your object $O$ has a different orientation from your global frame $S$, and you know what that difference in orientation is, you can create a 4x4 transform matrix between the two:
$$
T = \left[ \...
- 16k
4
votes
Accepted
Balancing a plate with an IMU offset from the center
Basically it does not matter.
But you have to be carefull if the plate is rotating fast, because the rotation of the plate around its center point, with the IMU placed out of center, will cause the ...
- 1,657
4
votes
Open source implementations for GPS+IMU sensor fusion?
ROS has a package called robot_localization that can be used to fuse IMU and GPS data. This package implements Extended and Unscented Kalman filter algorithms.
The package can be found here.
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4
votes
Pose-Graph-SLAM: How to create edges if only IMU-odometry is given?
First off, it doesn't sound like you're actually doing SLAM. You didn't mention an exteroceptive sensor (e.g., laser, camera) that actually maps the environment. With just an IMU, you are doing ...
- 980
4
votes
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Practicality of using magnetometer inside AUV
Mags are used in almost all UAVs. It will be useful and it will be a unique source of information.
Adding a some shielding between the mag and your computers and power lines will greatly reduced the ...
- 1,853
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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 ...
- 255
4
votes
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What is the consquence of Gimbal lock?
I made a clip for you (https://i.stack.imgur.com/Z0q5Y.jpg) using Unity, which internally represents rotations as quaternions, but uses Euler angles for display and positioning.
You can see that, at ...
- 16k
4
votes
Accepted
Why do we need to know the translation between Camera and IMU?
You answered yourself.
Your underlying model of point moving through space usually assumes the center of gravity to match the camera frame.
If your inertial sensor have a translational offset from ...
- 271
3
votes
Multi-Rate Sensor Fusion using EKF
Part 1. Use one or the other. Often odometery is used instead of kinematics or dynamics for prediction, at least in my work.
Part 2.
This is handled by the construction of the measurement equation ...
- 5,312
3
votes
Is there a way to measure 3 axis orientation without a magnetometer?
Calibration procedures for magnetometers exist, to compensate for soft iron (nearby ferromagnetic objects) and hard iron (nearby magnetic fields) offsets, which skew the measurements. However, these ...
- 550
3
votes
Using Accelerometer, Gyroscope and any sensor to track speed, position,
You are essentially making your own IMU. The way this works is essentially:
the accelerometer gives you linear acceleration
the rotational gyro gives you angular velocity
integrate the rotational ...
Ben♦
- 5,825
3
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imu position without GPS or camera
No, it is not possible to eliminate the cumulative position error caused by sensor noise and bias without using an additional sensor which can report any kind of position measurement.
Even the best ...
- 550
3
votes
Accepted
Localising a robot placed at an unknown position in a known environment
The problem is that you can't apply path planning until you know where the robot is in the global coordinate frame. There are many localization techniques, and each has its pros/cons; I have used ...
- 926
3
votes
Need help regarding development of Extended Kalman Filter for sensor-data fusion of odometry and IMU data
Adding to the above, my favorite way to debug a misbehaving filter is to isolate each step.
Make sure your prediction step works before correcting it. Your bot should drive straight right with 0,0,0 ...
- 5,312
3
votes
Shield IMU from magnetic interferences
Nope. Magnetometers measure the magnetic field. The field it's measuring is going to be the sum of fields from a variety of sources. The field you're interested in is the earth's. But it is not ...
- 1,853
3
votes
Self balancing robot control system strategies
I can recommend an alternative which has worked for me quite well.
I derived the dynamical model of a inverted pendulum, then linearised it around the stable operating point. With this simplified ...
- 71
3
votes
Compensation for IMU mounting misalignment
You need the transformation from the car to the IMU.
You can get this by recording the IMU published attitude with the car in known orientations.
You should be able to construct the IMU to car ...
- 1,853
3
votes
Accepted
I fused a GPS and IMU and I am wondering if my results make sense
Do you have a simulation? I would recommend that you simulate the data first to debug and tune your KF. The simulation should model the true IMU outputs (Grove has some details on that) and true ...
- 46
3
votes
angular velocity output of IMU
1) An inertial frame is one in which a free particle travels in a straight line at constant speed, or is at rest. Practically speaking, you usually check if a frame is inertial or not by ...
- 331
3
votes
Navigation - GPS + IMU; how to make it more accurate?
You should use a Kalman Filter. Here are two nice tutorials that explain how Kalman Filter algorithm works and the working principle of IMU/GPS sensors.
short: https://www.navlab.net/Publications/...
- 367
3
votes
Accepted
Yaw from IMU acceleration
If you assume the IMU lies on a fixed incline plane with pitch $\theta$, and you define yaw $\psi$ as the rotation between the IMU and the downhill direction, then the answer is
$$\psi = \text{atan2}(-...
- 449
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