11
votes
If I must fly my drone in bad weather, how can I maintain control of it in strong winds?
In controls this is known as disturbance rejection. In order to sustain your motion in the presence of high winds you need the controller to be as responsive as possible, and an accelerometer would ...
- 4,386
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
8
votes
Accepted
Instantaneous velocity calculation from accelerometer?
The only way to get a velocity from an accelerometer is to numerically integrate the output of the accelerometer. That is,
$$
v = v_0 + a*dT \\
$$
where $dT$ is the elapsed time between ...
- 15.9k
7
votes
How to interpret and use values of an accelerometer
You should really read the datasheet that acs linked in a comment to your question.
The device you're using has a set of 16-bit analog to digital converters (ADCs) that convert the actual outputs of ...
- 15.9k
7
votes
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 ...
- 1,909
6
votes
Accepted
Stabilising an inverted pendulum
There are lots of ways to solve this problem, which falls into the category of Control Engineering. There are two standard approaches:
Classical Control: The control command has to be proportional ...
- 1,258
6
votes
Accepted
calculating position based on accelerometer data
You're trying to do numeric integration, which takes the form:
$$
\mbox{integrated value } +=\mbox{derivative} * \mbox{elapsed time}
$$
What you have instead of ...
- 15.9k
6
votes
Paradox: I can't use accelerometer measurements to obtain information about my states in a quadcopter?
If the drone is not falling (holding height in the sky), and it's not accelerating in any particular direction, then the accelerometer should be reading:
$$
a = \left[ \begin{array}{}
g_x \\
g_y \\
...
- 15.9k
5
votes
What does "6 degrees of freedom" mean?
Most "meters" of all varieties include up to three degrees of freedom simply to observe all three dimensions of reality we find ourselves in.
That said, every object in our three space has three ...
- 95
5
votes
Accelerometer deterministic errors
Cross-axis sensitivity: A reading on one axis creates a false reading on another axis. This could be because the signal traces are close together and capacitive coupling induces a voltage on the ...
- 15.9k
4
votes
Accepted
Complimentary filter issues
There are quite a few things wrong here. I'll split them into two sections: technical errors, and coding warnings.
Technical Errors:
You are not calculating your angles from accelerometer readings ...
- 15.9k
4
votes
Accepted
Paradox: I can't use accelerometer measurements to obtain information about my states in a quadcopter?
I encountered the same puzzle. I had a clue at the beginning that the gravity information is contained within accelerometer measurements due to aerodynamic drag. Then I found a paper The True Role of ...
- 56
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
Stabilising an inverted pendulum
The theory that describes what you are looking for is call Control Theory. Search for the Nonlinear Systems textbook by Hassan Khalil for an excellent overview of the material--the inverted pendulum ...
- 926
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
votes
Accepted
Which sensor type most accurately measures position?
I would use linear or rotary encoders - the difference in terminology, encoder vs. potentiometer, is in the fact that any linear potentiometer could be used as a linear encoder, but not all linear ...
- 15.9k
3
votes
Displacement with accelerometer
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 ...
- 106
3
votes
How to calculate Euler Angles from gyroscope output?
Using the Gyroscope
First thing to note is that the gyroscope is reporting angular rates with respect to the sensor. So if the sensor is rotating with some rate, the data it's outputting will be in ...
3
votes
Accelerometer calibration - how to get cross-axis sensitivities
I realize this question is 2 years old, but I have direct recent experience with this. The way I did this is with 6 rotated cube positions with 1000 points at each position, so a total of 6000 ...
- 141
3
votes
Accepted
Can I use a 3D gimbal system as a simplistic quadcopter IMU(3 axis accelerometer)?
A gimbal system will not replace an accelerometer. I assume by gimbal system you mean something like a Gyroscope, i.e. a device that has a fixed orientation allowing you to measure your orientation ...
- 218
3
votes
Paradox: I can't use accelerometer measurements to obtain information about my states in a quadcopter?
Accelerometers measure kinematic acceleration with the addition of gravity. So for an accel to measure 0, the vehicle would need to be accelerating downward at $g$. To get inertial acceleration out of ...
- 1,843
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 ...
- 1,843
3
votes
Data collected from ROS
As Ben noticed, you may want to elaborate on your question, but in general data collection in ROS is performed using tools from the rosbag package.
As you'll find when you read the documentation, ...
- 1,308
2
votes
Why do 3-axis accelerometers seemingly have a left-handed coordinate system?
This is not using a left-handed coordinate system! Check out my crude edits to the diagram.
Note each coordinate system (RGB for XYZ, black for gravity) has the gravity vector aligned in the negative ...
- 1,377
2
votes
Accepted
Quadrocopter problem with stability
You have far too much vibration reaching your sensors. Mount the board you're using with vibration damping mounts, this should solve most of your problem. An easy way to do this is to attach each ...
- 1,843
2
votes
What does "6 degrees of freedom" mean?
To understand what these gyroscopes and accelerometers are measuring, you first need to know the physics and geometry behind "Degrees of Freedom". In terms of physics, each degree of freedom (DoF) in ...
- 378
2
votes
What does "6 degrees of freedom" mean?
In IMUs, the number of degree of freedom is the number of independent readings they can do.
For 9 DOF IMU it is typically 3 for the accelerometer, then 3 for the gyroscope and 3 others for the ...
- 571
2
votes
What does "6 degrees of freedom" mean?
n degrees of freedom of an object means it requires n unique parameters to completely define itself. For eg., a 3-DOF arm requires 3 joint parameters with which each and every position on the arm can ...
- 173
2
votes
Generate synthetic accelerometer data based on (x,y,z) coordinate
I assume that the three location input signals are functions of time, i.e., $x=x(t)$, $y=y(t)$, and $z=z(t)$ relative to a fixed, non-rotating reference frame. Then one could create a simple ...
- 385
2
votes
Should I use or not EKF for Baro-Acc altitude estimation?
EKFs are appropriate when you have nonlinear equations describing the system, either in the system dynamics or the measurement dynamics. In this case, I think a plain KF should be sufficient assuming ...
- 1,843
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