I am using an Accelerometer to track the linear motion of an object x-axis. I need to precisely find the time instant when the object stops, so that i can integrate the accelerometer data to track the path of the motion from the start to the completion of motion.
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Does anyone know if Unity's API Gyroscope.userAcceleration (https://docs.unity3d.com/ScriptReference/Gyroscope-userAcceleration.html) is using gyroscope sensor to work or accelerometer?
Edit my answer:
Gyroscope.userAcceleration uses the acceleration data from the gyroscope and the accelerometer sensor of your device. (refers to linear acceleration, not rotational)
So it seems the Gyroscope class performs some sort of sensor fusion.
AccelerometerInput uses the build in accelerometer sensor of your device.
I believe it must use the accelerometer, since gyroscope cannot measure accelleration (while accelerometer can be used to extract rotation to a certain degree), userAcceleration just takes out the constant part (gravity aka earth acceleration) out, so when the device is not being moved user acceleration is zero even if actual data from the accelerometer contains gravity
How can i track a circular motion in 3D? Currently I'm using accelerometer & gyroscope and sensor fusion algorithm to calculate orientation. But i cannot calculate the position accurately and hence unable to track the motion precisely.Please suggest any algorithm or an alternate method.
Can i know through Gyroscope, if I've moved some distance?
To elaborate my question, can I be able to detect the device's motion if the user moves a couple of feet from the starting position?
Thanks in advance.
Linear motion is detected using the accelerometer. Rotation is detected using the gyroscope.
You can use the CMDeviceMotion class to detect both types of movement. You will have to integrate the value of userAcceleration over time to detect a change in position.
Check out the What's New in Core Motion video from WWDC 2011. You will probably find it helpful.
I want compute the current iphone motion velocity anytime based on accelerometer, the accelerometer is variable. Anyone can give any idea?
It's basically impossible. The only way is to integrate the acceleration, but that magnifies the inaccuracy of the iPhone's not very accurate accelerometer, and because you don't have an independent orientation sensor (the iPhone uses gravity to figure that out!), you can't distinguish lateral acceleration from tilting the phone.
How people do this in the real world is to measure velocity using something else like GPS, and use the accelerometer to interpolate.
I'd like to transform the yaw, pitch and roll of the iPhone from the body frame to the world frame, i.e. azimuth, pitch and roll. On Android this is easily done with the
SensorManager.remapCoordinateSystem(), SensorManager.getOrientation methods as detailed here: http://blog.mysticlakesoftware.com/2009/07/sensor-accelerometer-magnetics.html
Are similar methods available for the iPhone or can someone point me in the right direction how to do this transformation?
Thanks
The accelerometer is good enough to get gravity direction vector in device coordinate system. That is in case when device calms down.
The next step for full device orientation is to use CLLocationManager and get the true north vector in device coordinate system.
With the normalized true north vector and gravity vector you can easily get all other directions using the dot and cross vectors product.
The accelerometer (UIAccelerometer) will give you a vector from the device's accelerometer chip straight down. If you can assume that the device is being held fairly steady (i.e., that you're not reading acceleration from actual movement), then you can use simple trig (acos(), asin()) to determine the device's orientation.
If you're worried that the device might be moving, you can wait for several accelerometer readings in a row that are nearly the same. You can also filter out any vector with a length that's ± TOLERANCE (as you define it) from 1.0
In more general terms, the device has no way of knowing its orientation, other than by "feeling gravity", which is done via the accelerometer. The challenges you'll have center around the fact that the accelerometer feels all acceleration, of which gravity is only one possible source.
If you're targeting a device with a gyroscope (iPhone 4 at the time of writing), the CoreMotion framework's CMMotionManager can supply you with CMDeviceMotion updates. The framework does a good job of processing the raw sensor data and separating gravity and userAcceleration for you. You're interested in the gravity vector, which can define the pitch and roll with a little trig. To add yaw, (device rotation around the gravity vector) you'll also need to use the CoreLocation framework's CLLocationManager to get compass heading updates.