Robotics Stack Exchange
Robotics Stack Exchange

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1500 questions
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4 answers

How can one determine whether a LiPo battery is going bad?

In our lab we use LiPo batteries to power our quadrotors. Lately we have been experiencing stability issues when using certain batteries. The batteries seem to charge and balance normally and our battery monitor indicates they are fine even when…
DaemonMaker
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Denavit-Hartenberg parameters for SCARA manipulator

I'm going through the textbook Robot Modeling and Control, learning about the DH convention and working through some examples. I have an issue with the following example. Given below is an image of the problem, and the link parameter table which I…
JDS
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5 answers

Low-cost centimeter accurate satellite positioning (GNSS/GPS)

I am looking for a cheapest possible GPS setup with a centimeter precision without much HW hacking. I am not able to produce my PCB or do any soldering (though I would do that if there is no other way) so a kind of a easy-to-assemble setup would be…
Kozuch
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How to use quaternions to feed a PID quadcopter stabilization loop?

I'm making a quadcopter. I have set up a PID loop to stabilize it to a given Euler angle (pitch and roll). The problem arises when the roll approaches 90 degrees (45 degrees and up). The values don't make sense anymore, as it approaches the gimbal…
Friend of Kim
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2 answers

Our quadcopter goes forward instead of hovering in place. How to correct it?

I'm trying to do a quadcopter with some friends and we have a problem. It goes forward instead of hovering in place. We made a video to explain it, you can see it here. As you can see, the quadcopter flight and go forward when I don't touch the…
Dougui
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9
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2 answers

Why is ROS not a real-time operating system?

ROS is not real-time OS. After reading the architecture of ROS, I am unable to realize why is ROS not real-time? What part of the architecture or what design decision is causing that?
Manas Paldhe
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2 answers

How to calculate the right and left speed for a tank-like rover?

I am trying to control the Rover 5 robot using an Android app with a touch-based joystick control in the app UI. I want to calculate the speed of the left and right motors in the rover when joystick is moved. From the joystick, I get two values, pan…
Punit Soni
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1 answer

AprilTag vs Aruco markers

AprilTag and Aruco are both popular methods for vision-based fiducial marker pose estimation. What are the pros and cons of each fiducial marker pose estimation systems?
Rufus
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3 answers

Motion Planning vs. Control

Often I see positions for robotics companies split into planning and controls engineers. But motion planning and controls seem to have a lot of overlap. As I understand in motion planning the planner produces a trajectory. But to make sure the…
Lubed Up Slug
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4 answers

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 confirm this. I typically only use the chip to…
Ben
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Localizing a swarm of robots

I have a 300cm x 300cm room with a 25cm high ceiling (yes twenty five centimeters). It contains 50 small wheeled robots (about 20cm x 20cm). A central computer will orchestrate the movements of the robots, using a wireless network to send position…
Rocketmagnet
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HMMs vs. CRFs to model time-series force data of robots interacting with environment?

I have a time-series of force data of robots interacting with environment objects with various textures. I would like to develop models of various textures using the time-series data to classify textures into smooth, rough, moderate, etc.…
Gilmour
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2 answers

How to model unpredictable noise in Kalman Filter?

Background: I am implementing a simple Kalman Filter that estimates the heading direction of a robot. The robot is equipped with a compass and a gyroscope. My Understanding: I am thinking about representing my state as a 2D vector $(x, \dot{x})$,…
Sibbs Gambling
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How exactly does sensor fusion work in Kalman filters?

I've been looking into implementations of Extended Kalman filters over the past few days and I'm struggling with the concept of "sensor fusion". Take the fusion of a GPS/IMU combination for example, If I applied a kalman filter to both sensors,…
MaskedAfrican
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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 calculated the error_value using $k_p *…
meteors
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