I'm working in a project that involves gyroscopes...
I'm using Arduino and an ITG 3200 to read the data from the gyroscope. I get 3 values in deg/s for each axis (x,y,z).
My question is: How can I know the actual (physical) position or direction of the device (let's say an airplane). There has to be a math formula or something like that.
Using only the gyroscope signal (which you have to integrate numerically), you'll eventually run into trouble, due to drift. What's normally done is combining an accelerometer (for low frequency signals, i.e. drift) with a gyroscope (for high frequency signals). Here's a link few links showing more or less exactly what you want:
http://www.starlino.com/imu_guide.html
http://www.instructables.com/id/Accelerometer-Gyro-Tutorial
http://www.starlino.com/quadcopter_acc_gyro.html
Also, see these StackOverflow questions:
Combine Gyroscope and Accelerometer Data
Integrating gyro and accelerometer readings
gyro, accelerometer, magnetometer and Kalman filter
How to determine relative position using accelerometer and gyro data
We are working on a similar problem.
We found this video on YouTube especially helpful, as it came with a paper as well as an implementation (which runs on Arduino):
http://www.youtube.com/watch?v=fOSTOnQzZCI
The paper and source code:
http://code.google.com/p/imumargalgorithm30042010sohm/
In our case (getting the orientation of a remote-controlled ball), we also had to include an accelerometer and a magnetoscope.
Related
On a device I want to detect a range of forces: small forces (Minimum around 0.01g) but also stronger forces like 0.1g - 0.15g.
This device will have different positions in 3d space so in order to detect the small forces I have to know its angle in order to be able to subtract 1g. Because the device can have a random position (angle position).
What I did so far: I used the MPU6050 and used a complementary filter with accel. and gyro.
It's something like:
agnleX_k+1 = 0.98*(angle_k + deltaT * gyro_k+1) + 0.02*angle_acc_k+1;
angle_acc is the angle calculated from the accel. sensor. Something like:
arctan(accelX / sqrt(accelX^2 + accelY^2 + accelZ^2 + ))
So I am interested in:
forceX_k+1 = accelX_k+1 - 1g*sin(agnleX_k+1)
The problem is:
If I want to detect a small force coming in very fast, let's say on accelX_k+1 I would want to detect a Change from 0g to 0.01g or more but in a very small time range. The problem is that my calculated angle would then also be influenced by this small and fast change of the accel. sensor although the angle haven't really changed.
I think I would have to do the angle calculation independent of the accel. sensor. Can I do something like a complementary filter with gyro and magnetometer? Would that work the same as my filter described above but just with the mag. sensor instead? Or how would you do that? I was thinking about using MPU9250.
You stated using MPU6050, which contains both an accelerometer and a gyrosocpe. You could use them independantly - get acceleration from the accelerometer and get angles from the gyroscope, and then use the angles to compensate for rotation. There is no need for the angle to depend on your accelerometer.
Using DMP library fromJeff Rowberg will do the work for you.
it can compensate gravity acceleration internally way faster that Arduino code.
Link to github
I'm using arduino to read from an accelerometer and gyroscope, from which I can get a vector of accelerations and also a vector of speeds of rotations in the device's coordinates, now I want to transform the accelerometer data into the absolute coordinates, in which the Z axis straightly points up aligned with the direction of gravity force, and X, Y form an absolute horizontal plane.
I've read many posts on internet, but cannot find a good solution yet. These posts either discuss how to remove noise by combining gyroscope with accelerometer (e.g., http://www.starlino.com/imu_guide.html) or provide a solution based on Android, which could directly leverages the rotation matrix provided by Android API (For example, this post: Transforming accelerometer's data from device's coordinates to real world coordinates).
But now, I only have raw readings of accelerometer and gyroscope, how can I transform accelerations from device coordinates to absolute coordinates via python?
BTW, in my experiments, the device will be always in an relative stable state in a while, which can be used to estimate the direction of gravity in device's coordinates.
I am trying to build my custom Photosphere viewer to run using SDL2 and a custom IMU I purchased. So far, I have managed to read IMU values, open the .jpg and display it using SDL2.
My issue is how to make sense IMU data to read parts of the jpg appropriately. Basically, I do not want to display the whole jpg but just parts of it based on IMU data (I receive Euler angles or Quaternions). Right now, I am just using a single mono photosphere (I am not concerned with stereo yet), which is stored as a equirectangular projection, and I need to use the IMU to get it to a polar projection (I believe?)
I am not sure how to index the jpg based on IMU data to create a working photosphere viewer and I cannot seem to find a good explanation of how to address the jpg. Can anyone point me into the right direction? Thanks!
I was able to find a really great OpenGL based simple Python photosphere viewer here. I just then needed to create a rotation matrix from the sensor IMU. There are good tutorials to convert from Quaternion to Matrix like this one.
I know that what I'm going to ask could sounds crazy, but I'm trying to figure out how to resolve a problem in a smart way.
It's quite difficult to explain my problem, that's why I made an hand-made draft downloadable from here :) https://dl.dropboxusercontent.com/u/5049281/static/Images_Impulse_Direction.zip.
images in that zip (copied by Spektre)
The setup can be approximated with a pipe endorsed on a rubber wall. The pipe is firmly connected (whit an unknown position and orientation) to a IMU equipped with an accelerometer and a gyroscope (sample frequency 110 hz).
I would like to discover the direction of the pipe axis (expressed in the IMU reference system) analyzing the data acquired during some taps at the end of the pipe in the same direction of the pipe axis. The taps are applied with the palm of the hand. In the figure the direction should be just on X axis.
I think that if the motion is just a translation (I could verify it checking if gyroscope data is close to zero), the acceleration (with the gravity removed) during the tap should have the same direction of the pipe axis.
Is there a smarter solution than just apply an high-pass filter to the signal an then save the direction of the sample with the higher magnitude?
Thanks for your help!
I am using arduino and accelerometer MMA7341 to measure the acceleration in x direction of an oscillating metal table. But the mounting of the accelerometer is tilted by a small angle (say Q) . Is it affect the acceleration?. If it is affect the acceleration in x direction , how can correct it without changing the tilt of the acceleration sensor.
"Tilt" and "acceleration" are both the same, from the perspective of most sensors, since both measure a force, rather than an actual angle (tilt) or change in velocity (acceleration).
What you should do is make sure the object on which the sensor is mounted is "level", within the best of your ability to determine such a thing, and use the values from analogRead() or whatever else your device provides, as the "0" values.
For the MMA7341 you'll also need to calibrate your analog signals, or else use a high precision reference as input to the Aref pin, assuming you're Arduino exposes that pin.
I think this depends on what you are measuring. THe MMA7341 looks to be able to be used for acceleration as well as tilt. If you are measuring acceleration then the mounting position doesn't matter since acceleration is a change of velocity and the velocity delta will be constant regardless of orientation.
If you are measuring tilt then thats obviously different. You could theoretically measure the initial tilt and then compensate for that in your code if you wanted to of course.