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 ...
SteveO's user avatar
  • 4,386
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 ...
Chuck's user avatar
  • 16k
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 ...
Chuck's user avatar
  • 16k
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 ...
Mark Omo's user avatar
  • 1,919
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 ...
Paul's user avatar
  • 1,278
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 \\ ...
Chuck's user avatar
  • 16k
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 ...
Chuck's user avatar
  • 16k
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 ...
V. Yao's user avatar
  • 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 ...
Chuck's user avatar
  • 16k
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 ...
BarbalatsDilemma's user avatar
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 ...
holmeski's user avatar
  • 1,853
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 ...
JSycamore's user avatar
  • 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's user avatar
  • 5,855
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 ...
Shrivathsav Seshan's user avatar
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 ...
JSycamore's user avatar
  • 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 ...
holmeski's user avatar
  • 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, ...
xperroni's user avatar
  • 1,353
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 ...
Christo's user avatar
  • 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 ...
holmeski's user avatar
  • 1,853
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 ...
koverman47's user avatar
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 ...
SteveO's user avatar
  • 4,386
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 ...
bergercookie's user avatar
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 (...
Chuck's user avatar
  • 16k
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 ...
gvgramazio's user avatar
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 ...
Chuck's user avatar
  • 16k
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 ...
ryan0270's user avatar
  • 2,804
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 ...
Chuck's user avatar
  • 16k
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 ...
Raggy's user avatar
  • 128
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 ...
acs's user avatar
  • 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 ...
50k4's user avatar
  • 6,662

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