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 ...
- 1,904
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
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
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
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
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
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 ...
- 1,853
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
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
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
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
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, ...
- 1,363
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 ...
- 1,853
2
votes
Localising a robot placed at an unknown position in a known environment
There are many tactics for localization in a known environment. the most popular ones are the Filtering methods which include Kalman filtering and Particle filtering. Nowadays the second one is the ...
- 400
2
votes
Drift in Integrating Angular Acceleration to Angular Velocity using two accelerometer data
The authors of the paper you supplied give two reasons (as I see it) for not using gyroscopes. The first is that the gyroscopes are subject to a maximum angular velocity. The second is the power ...
- 503
2
votes
Gauss Newton Method for Accelerometer calibration
$J^T \times J$ is an approximation to the Hessian which comes from the Levenberg Marquardt Algorithm. It is a least-squares approach, and seems to be used frequently in a variety of optimization ...
- 4,396
2
votes
Angles from gyroscope readings using quaternions
I'll link you to some math but try to give a conceptual explanation, too.
Consider a case where you want to start with the IMU upright and pointed forward and want to end with the IMU upside-down (...
- 15.9k
2
votes
Explanation of Quadcopter Dynamics, Components and Control
You're right. You should know the rpm of your propellers to build a mathematical model of your quadcopter and if you already have a mathematical model of your brushless DC motors you could compute ...
- 121
2
votes
What is required to get the roll, pitch and yaw of an aerial vehicle?
The only sustainable long-term acceleration (for anything terrestrial) is gravity. The Madgwick algorithm uses gravity and a magnetometer to correct gyro drift.
Watch the video, then head to the ...
- 15.9k
2
votes
How to create a Complementary Filter for a linearly accelerating body to obtain estimate of orientation in quaternion?
The point of a complementary filter is combine the low-pass parts of some measurements (e.g. accelerometer) with the high-pass parts of other measurements (e.g. gyro). If the accelerometer perfectly ...
- 2,814
2
votes
Accepted
Opposite direction of rotation calculated by Gyro and Accelerometer
Welcome to Robotics, KMC!
One thing I noticed is that your equation gives $\phi=\arctan2(-a_y,-a_z)$, but you're calculating it as $\phi=\arcsin(-a_y/\cos(\theta))$. If your sensor is oriented as ...
- 15.9k
2
votes
accelerometer and gyroscope fusion using extended kalman filter
You should be using quaternions for fusion for good behaviour. Addition and multiplication for quaternions will be swapped out by rotation composition operations for quaternions and your orientation ...
- 128
1
vote
How can I compensate for pendulum and cart motion when using an accelerometer to detect the tilt angle?
If an accelerometer is mounted along the pole axis of a pole-cart system with its axes oriented tangential and normal to the pole rotation, the components of acceleration can be found using rigid body ...
- 136
1
vote
which is best IMU for Quad-Copter
Both products are based on the same chip - MPU6050. I won't be surprised if passive components used in both modules will be the same too. That means, that from performance side, there will be probably ...
- 953
1
vote
Problem with angle calculation
Your equation is formed so that the angle can be zero only when the projection of the gravity vector onto the X axis is zero. That gives zero when the system is oriented vertically, because the ...
- 146
1
vote
Accepted
How to transform Accelerometer data from the robots frame to the world frame
If you are only computing the x, y and yaw (as I understand, these are the degrees of freedom of the robot) then:
1. The yaw acceleration is just what you measure
2. x and y acceleration is what you ...
- 26
1
vote
What sensors and algorithms are used in Digital Pen for tracking hand writing?
Classical odometry sensors:
IMU:gyro, accelerometer, compass (Wiimote IMU - not infrared)
Optical flow (optic mouse)
encoders (like mouse marble)
These systems are cheap and easy to apply. However ...
- 1,124
1
vote
What sensors and algorithms are used in Digital Pen for tracking hand writing?
Most smart pens use a number of differenst sensors different types of MEMS but more importanly they use optical sensors. Pen tip motions are recreated based on measurements of all sensors using sensor ...
- 6,682
1
vote
Utilizing the inertial sensors in an AR Drone
That's because your fixed frame is set to /odom (Essentially, you're setting your global frame to your local frame, so relative to the vehicle itself, the vehicle never moves!). The solution would be ...
- 1,106
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