All Questions
559
questions
81
votes
9
answers
338k
views
What are good strategies for tuning PID loops?
Tuning controller gains can be difficult, what general strategies work well to get a stable system that converges to the right solution?
- 1,327
31
votes
3
answers
10k
views
What is a suitable model for two-wheeled robots?
What is a suitable model for two-wheeled robots? That is, what equations of motion describe the dynamics of a two-wheeled robot.
Model of varying fidelity are welcome. This includes non-linear models,...
- 3,084
7
votes
3
answers
8k
views
What iRobot products support the open interface besides the iRobot Create?
I have read that certain iRobot products support or can be hacked to support something close to the open interace. There is even a book about hacking Roomba. What Robots have this capability?
- 123
70
votes
5
answers
12k
views
Why do I need a Kalman filter?
I am designing an unmanned aerial vehicle, which will include several types of sensors:
3-axis accelerometer
3-axis gyroscope
3-axis magnetometer
horizon sensor
GPS
downward facing ultrasound.
A ...
- 6,457
16
votes
2
answers
19k
views
Calculate position of differential drive robot
How do you calculate or update the position of a differential drive robot with incremental sensors?
There is one incremental sensor attatched to each of the two differential wheels. Both sensors ...
- 395
19
votes
7
answers
8k
views
Robot never goes straight
I am using 2 identical DC motors and a castor wheel. The motors are connected to L293D motor driver and are controlled by RPi.
The robot is not going straight. It veers off to the right. I am ...
- 313
9
votes
2
answers
7k
views
Line Follower optimization
I'm working on building a line follower robot and want to optimize its performance. It was suggested that I use a PID algorithm. I read a lot about PID but am confused a bit regarding following:
I've ...
- 221
7
votes
1
answer
1k
views
understanding the PID controller
I am trying to understand the effects of P, I and D constants in a PID controller on a system.
As far I've understood, P and I make the system 'faster', and D makes it 'slower'(which I read in books),...
- 345
39
votes
11
answers
57k
views
Preventing leaks in motor shafts for underwater bots
Whenever building an aquatic bot, we always have to take care to prevent leakages, for obvious reasons. Now, holes for wires can be made watertight easily--but what about motors? We can easily seal ...
- 1,833
32
votes
6
answers
63k
views
Which type of actuator will be suitable for a very strong robot arm?
I wish to build a robotic arm that can lift a useful amount of weight (such as 3-6 kg on an arm that can extend to approx 1.25 meters). What actuators are available to accomplish this? The main ...
- 420
28
votes
8
answers
18k
views
Absolute positioning without GPS
Using an IMU a robot can estimate its current position relative to its starting position, but this incurs error over time. GPS is especially useful for providing position information not biased by ...
- 2,162
22
votes
4
answers
7k
views
What frequency does my quadcopter output-sense-calculate-output update loop need to stay stable?
With a 600 mm (2 foot) motor-to-motor quadcopter, what frequency does my output-sense-calculate-output update loop need to stay stable?
I'm estimating a total takeoff weight of very roughly 2 pounds (...
- 4,545
21
votes
4
answers
21k
views
How can I use the Arduino PID library to drive a robot in a straight line?
I would like to create an Arduino based robot with 2 wheels, quadrature encoders on each wheel, a H-bridge driver chip (or motor controller) and a caster. I want to use the PID library to ensure the ...
- 361
19
votes
3
answers
3k
views
What is the best way to power a large number (27) servos at 5 V?
I apologize if this question may sound a little vague. I am working on a robotics project that will contain 27 servos of various sizes and I am having trouble figuring out how they should be powered.
...
user428
8
votes
3
answers
1k
views
What would be the best way to handle food grains?
I'm trying to handle food grains like rice, wheat in an automated way (to cook simple dishes). For this I have to transfer grain from a larger container to a weighing scale. I know I can use solenoid ...
- 223
7
votes
2
answers
8k
views
Position Controller for a Quadrotor
I have a question regarding the implementation of a quadrotor's position controller.
In my Matlab model the quadrotor takes 4 inputs: a desired altitude ($Z_{des}$) and desired attitude angles($\Phi_{...
- 700
6
votes
3
answers
2k
views
Create 2 losing serial communication after toggling full to passive while charging
We are having an issue where after toggling the create 2 from passive to active, then waiting a few seconds and toggling back to passive while on the charger, all serial communication fails a certain ...
- 91
5
votes
1
answer
3k
views
The aerial refueling problem: sketch of a feedback controller
At first happy new 2015!!!
I'm looking for my next simulator development: a Tanker is flying at constant speed (350 Knots) (no acceleration, no change of altitude or direction). The Tanker is ...
- 700
5
votes
1
answer
5k
views
Robot path planning
My goal is to move robot in certain points as shown in the figure. It's initial position is (x0,y0) and move along other coordinates.
I am able to track robot position using a camera which is ...
- 83
4
votes
2
answers
889
views
Evaluating the similarity of two 7 Degree of Freedom Arms
I am working on the Baxter robot where I have a first arm configuration and a bunch of other arm configurations, where I want to find the closest arm configuration to the first among the many other ...
- 304
43
votes
4
answers
26k
views
What is the difference between Kinect for Windows and Kinect for XBox?
As I see there is a huge price gap between the two \$223 vs \$99 (at amazon).
My intention is to use one of those from Ubuntu linux to perform depth sensing, navigation etc. and naturally I prefer ...
- 846
29
votes
5
answers
33k
views
Particle filters: How to do resampling?
I understand the basic principle of a particle filter and tried to implement one. However, I got hung up on the resampling part.
Theoretically speaking, it is quite simple: From the old (and ...
- 821
22
votes
4
answers
4k
views
Why are quadcopters more common in robotics than other configurations?
I've noticed that almost all research being done with helicopter robots is done using quadcopters (four propellers). Why is there so little work done using tricopters in comparison? Or a different ...
- 1,564
9
votes
4
answers
4k
views
Why do 3-axis accelerometers seemingly have a left-handed coordinate system?
Careful inspection of page 35 (figure 58) of the ADXL345 datasheet shows that under gravitational loading only, the chip uses a left-handed coordinate system. My own experiments with this chip ...
Ben♦
- 5,855
7
votes
3
answers
4k
views
Jacobian-based trajectory following
I would like to control my 7 DOF robot arm to move along a Cartesian trajectory in the world frame. I can do this just fine for translation, but I am struggling on how to implement something similar ...
Ben♦
- 5,855
6
votes
4
answers
8k
views
PID output does not reach setpoint precisely enough
I'm developing/tuning a software PID for a quadcopter. For now I'm only trying to stabilise the pitch angle using the front and back motors, and I'm only looking at Kp. The motors have a control ...
- 478
6
votes
3
answers
15k
views
Hand Eye Calibration
I'm trying to use a dual quaternion Hand Eye Calibration Algorithm Header and Implementation, and I'm getting values that are way off. I'm using a robot arm and an optical tracker, aka camera, plus a ...
- 506
5
votes
3
answers
3k
views
IRobot Create 2: Powering Up after Sleep
I've notice the IRobot Create 2 does not respond to the app's commands when it has been sleeping. If I press the Clean button and re-run the app then the robot is responsive to the commands.
My ...
- 173
4
votes
1
answer
1k
views
Robotic manipulator Jacobian by product of exponentials
I've taken a class and started a thesis on robotics and my reference for calculating the Jacobian by product of exponentials seems incorrect, see:
http://www.cds.caltech.edu/~murray/books/MLS/pdf/...
- 95
3
votes
1
answer
3k
views
iRobot Create 2: Encoder Counts
This post is a follows from an earlier post (iRobot Create 2: Angle Measurement). I have been trying to use the wheel encoders to calculate the angle of the Create 2. I am using an Arduino Uno to ...
- 926
2
votes
1
answer
4k
views
PID controller that targets a set rotation and a set velocity at that rotation?
I have a 3d physics simulation where I use a PID controller to reach a set orientation (orientation error drives a torque output). Which works well enough some cases, but in others it's not working ...
- 123
2
votes
1
answer
1k
views
How to import a 3D model in Webots_R2022b?
I have a 3D model which is made by SolidWorks. I remember that in older versions there was a function to import 3D models but I can't find it in R2022b. Can you tell me how to import it? Thanks so ...
- 23
0
votes
1
answer
429
views
Gazebo plugin location and documentation
I have a basic question regarding gazebo plugins. The gazebo tutorial 'Moving the Robot' available at Link refers to the differential drive plugin coded as shown in the picture.
Where can I find more ...
44
votes
2
answers
70k
views
How to choose the right propeller/motor combination for a quadcopter?
There are many sites which explain briefly this problem and even propose combinations. I however would like a much more detailed explanation. What is going to give my quad the most agility? Do I need ...
- 543
33
votes
2
answers
25k
views
How to fuse linear and angular data from sensors?
My team and I are setting up an outdoor robot that has encoders, a commercial-grade IMU, and GPS sensor. The robot has a basic tank drive, so the encoders sufficiently supply ticks from the left and ...
- 2,162
29
votes
7
answers
30k
views
What algorithm should I implement to program a room cleaning robot?
For this question assume that the following things are unknown:
The size and shape of the room
The location of the robot
The presence of any obstacles
Also assume that the following things are ...
- 391
24
votes
4
answers
16k
views
How to select cameras for a stereo vision system?
I am in the process of building a stereo vision system to be used on a UGV. The system is for a robot that will be used in a competition wherein the robot is teleoperated to find relatively small ...
- 3,921
22
votes
5
answers
2k
views
Is it better to have batteries distributed at the rotors or the center of the multicopter?
I've seen 3 approaches to mounting batteries on a multicopter:
All the batteries rigidly mounted near the center of the airframe
All the batteries in a bag hanging under the center of the airframe
...
- 4,545
22
votes
3
answers
15k
views
How can the inverse kinematics problem be solved?
The forward kinematics of a robot arm can be solved easily. We can represent each joint using Denavit–Hartenberg transformation matrices.
For example, if the $i^{th}$ joint is a linear actuator, it ...
- 3,084
16
votes
6
answers
30k
views
What is the cheapest / easiest way of detecting a person?
I'd like to know if anyone has had success detecting a warm-bodied mammal (ie. Human) using standard off the shelf, inexpensive sensors?
Ideally, I'd like to use an inexpensive sensor or ...
- 321
15
votes
3
answers
19k
views
Quadcopter PID tuning
In continuation of the question I asked here: Quadcopter instability with simple takeoff in autonomous mode
...I'd like to ask a few questions about implementing a basic PID for a quadrotor ...
- 419
12
votes
2
answers
6k
views
What are the advantages of using the Denavit-Hartenberg representation?
When one wants to model a kinematic chain and in particular define the frames attached to each body, it is common to use the Denavit-Hartenberg parameters.
What are the advantages of this ...
- 1,194
8
votes
3
answers
9k
views
Simple equation to calculate needed motor torque
Suppose I have a DC motor with an arm connected to it (arm length = 10cm, arm weight = 0), motor speed 10rpm.
If I connect a 1Kg weight to the very end of that arm, how much torque is needed for the ...
- 191
7
votes
1
answer
14k
views
calculating position based on accelerometer data
Please help me with the following task. I have MPU 9150 from which I get acceleration/gyro and magnetometer data. What I'm currently interested in is to get the orientation and position of the robot. ...
- 175
6
votes
2
answers
882
views
Static equilibrium for 7 dof manipulator
I have a 7 dof manipulator (Kuka LBR4+) and would like to calculate the joint torques needed to keep the arm in a static equilibrium. In most books the transposed jacobian is used to map the forces ...
- 193
6
votes
2
answers
857
views
Sending commands from Ubuntu
I have a iRobot Create model 4400 and I need to send commands to the open interface through Ubuntu. I'm using gtkterm at 57600 baud but when I press play button, it only drives around itself. I have ...
6
votes
4
answers
48k
views
Need help calculating the thrust on quadcopter motors
I'm trying to calculate the lifting capability of my four quadcopter motors. I tried using eCalc but it doesn't have battery I'm using. Are there any equations to keep in mind for doing these ...
- 173
5
votes
1
answer
11k
views
How to program a three wheel Omni?
I have created a three wheeled omni robot like the diagram below. Now I am unsure of how to program it. I want to use a single joystick so one x and one y value. The values for x and y are between -1 ...
- 155
4
votes
2
answers
2k
views
the uncertainty of initializing new landmark in EKF-SLAM
In EKF-SLAM (based-feature map) once the robot senses a new landmark, it is augmented to state vector. As a result, the size of the state vector and the covariance matrix are expanded. My question is ...
- 2,453
4
votes
4
answers
2k
views
SetuptoolsDeprecationWarning in ros2 Humble
I was trying to follow this tutorial in the official documentation of ros2 Humble for Integrating launch files into ROS 2 packages and ran in to the below given error after doing trying to perform a ...
- 201