# All Questions

388 questions
176k 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?
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,...
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 ...
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?
9k 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 ...
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 ...
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 ...
13k 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 ...
52k 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 ...
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 (...
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. ...
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 ...
229 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 ...
20k 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 ...
22k 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 ...
41k 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 ...
5k views

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($\Phi_{... 4answers 4k views ### Why are quadcopters more common in robotics than other configurations? I've noticed that almost all research being done with helicopter robots is done using quadcopters (four propellers). Why is there so little work done using tricopters in comparison? Or a different ... 4answers 18k views ### How can I use the Arduino PID library to drive a robot in a straight line? I would like to create an Arduino based robot with 2 wheels, quadrature encoders on each wheel, a H-bridge driver chip (or motor controller) and a caster. I want to use the PID library to ensure the ... 4answers 3k views ### PID output does not reach setpoint precisely enough I'm developing/tuning a software PID for a quadcopter. For now I'm only trying to stabilise the pitch angle using the front and back motors, and I'm only looking at Kp. The motors have a control ... 1answer 2k views ### The aerial refueling problem: sketch of a feedback controller At first happy new 2015!!! I'm looking for my next simulator development: a Tanker is flying at constant speed (350 Knots) (no acceleration, no change of altitude or direction). The Tanker is ... 2answers 4k views ### How to further understand the computed torque model controller For the following controller what do$q_{des}$and$q_{act}$stand for? Also, what is the general principle of this controller? Thanks! 1answer 2k views ### iRobot Create 2: Encoder Counts This post is a follows from an earlier post (iRobot Create 2: Angle Measurement). I have been trying to use the wheel encoders to calculate the angle of the Create 2. I am using an Arduino Uno to ... 6answers 22k views ### What algorithm should I implement to program a room cleaning robot? For this question assume that the following things are unknown: The size and shape of the room The location of the robot The presence of any obstacles Also assume that the following things are ... 2answers 67k views ### How to choose the right propeller/motor combination for a quadcopter? There are many sites which explain briefly this problem and even propose combinations. I however would like a much more detailed explanation. What is going to give my quad the most agility? Do I need ... 4answers 12k views ### How to select cameras for a stereo vision system? I am in the process of building a stereo vision system to be used on a UGV. The system is for a robot that will be used in a competition wherein the robot is teleoperated to find relatively small ... 6answers 28k views ### What is the cheapest / easiest way of detecting a person? I'd like to know if anyone has had success detecting a warm-bodied mammal (ie. Human) using standard off the shelf, inexpensive sensors? Ideally, I'd like to use an inexpensive sensor or ... 4answers 9k views ### How can the inverse kinematics problem be solved? The forward kinematics of a robot arm can be solved easily. We can represent each joint using Denavit–Hartenberg transformation matrices. For example, if the$i^{th}$joint is a linear actuator, it ... 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 ... 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 ... 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 ... 3answers 5k 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 ... 1answer 883 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),... 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 ... 4answers 2k 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 ... 2answers 3k 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 ... 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 ... 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 ... 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 ... 2answers 638 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 ... 4answers 31k 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 ... 1answer 6k 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. ... 1answer 318 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} \ ...
136 views

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 ...
23k 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 ...
24k 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?
657 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 ...
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 ...