All Questions

48
votes
9answers
161k 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?
29
votes
3answers
7k 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,...
14
votes
2answers
11k 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 ...
5
votes
3answers
3k 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?
8
votes
2answers
5k 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 ...
18
votes
6answers
5k 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 ...
56
votes
5answers
8k 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 ...
23
votes
9answers
12k 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 ...
26
votes
5answers
51k 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 3-6kg on an arm that can extend to approx 1.25 meters). What actuators are available to accomplish this. The main factors ...
20
votes
4answers
5k 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 (...
17
votes
3answers
2k 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 it how they should be powered. ...
8
votes
3answers
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 ...
24
votes
5answers
19k 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 ...
38
votes
4answers
21k 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 ...
34
votes
11answers
40k 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 ...
4
votes
1answer
5k 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_{...
20
votes
4answers
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 ...
18
votes
4answers
17k 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 ...
7
votes
3answers
4k 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 ...
5
votes
4answers
3k 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 ...
4
votes
3answers
136 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 ...
4
votes
1answer
1k 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 ...
2
votes
2answers
3k views

How to further understand the computed torque model controller

For the following controller what do $q_{des}$ and $q_{act}$ stand for? Also, what is the general principle of this controller? Thanks!
2
votes
1answer
2k 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 ...
25
votes
6answers
22k 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 ...
40
votes
2answers
67k 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 ...
18
votes
4answers
11k 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 ...
15
votes
6answers
28k 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 ...
18
votes
3answers
9k 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 ...
12
votes
3answers
18k 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 ...
3
votes
3answers
7k 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 ...
3
votes
2answers
12k views

Quadcopter PID output

I'm trying to develop a control system to a quadcopter and one of my options is to use a PID controller (which I think is the most used method). From what I've read, the commom strategy is to run a ...
7
votes
1answer
874 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),...
4
votes
2answers
1k 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 ...
8
votes
4answers
1k 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 ...
20
votes
5answers
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
votes
1answer
2k 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 ...
3
votes
1answer
348 views

Cannot disable sleep in passive mode for iRobot Create 2

I tried to disable sleep by pulsing the BRC pin low for one second every minute as suggested in the OI, but my Create 2 still goes to sleep after 5 minutes. My firmware is r3_robot/tags/release-3.2.6:...
2
votes
1answer
3k views

Quadcopter controlled by Raspberry Pi

I have: Raspberry Pi 3. Pi camera. CC3D flight controller. I have already developed a Python script that decides whether the quadcopter dron has to turn left/right, move straight on or to stop. Is ...
5
votes
2answers
620 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 ...
4
votes
1answer
5k 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. ...
3
votes
3answers
30k 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 ...
2
votes
1answer
309 views

Data association with ekf?

Given part of the following algorithm in page 217 probabilistic robotics, this algorithm for EKF localization with unknown correspondences 9. for all observed features $z^{i} = [r^{i} \ \phi^{2} \ ...
1
vote
3answers
136 views

Quadcopter Charging

Our thesis is about Multicopter using two batteries wherein the first battery is used and when the power goes out, a switch is placed use to charge the first battery while the second battery is ...
24
votes
2answers
22k 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 ...
22
votes
4answers
23k views

Is it possible to run a neural network on a microcontroller

Could you implement a simple neural network on a microprocessor such as the Arduino Uno to be used in machine learning?
15
votes
2answers
648 views

How do robotics startups work?

In software engineering startups, you generally go to a room with a computer or bring your own laptop, and write code. I'm interested in how robotics startups work: Is there a separate location for ...
15
votes
2answers
4k views

Programming a line following robot with reinforcement learning

I am considering programming a line following robot using reinforcement learning algorithms. The question I am pondering over is how can I get the algorithm to learn navigating through any arbitrary ...
7
votes
3answers
31k views

How to calculate quadcopter lift capabilities?

I'm looking for an equation (or set of equations) that would allow me to predict (with fair accuracy) how heavy a payload a quadcopter is capable of lifting. I assume the main variables would be the ...
20
votes
10answers
4k views

How mature is real-time programming in robotics? [closed]

Edit: I don't know why, but this question seems to be confusing many people. I am aware of when/where/why/how to use real-time. I am interested in knowing whether people who have a real-time task ...

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