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91 votes
4 answers
19k views

Why are Mars rovers so slow?

Mars rovers are typically very slow. Curiosity, for example, has average speed of about 30 meters per hour. Why is it designed so slow? Is it because of some specific power restrictions or for other ...
sharptooth's user avatar
  • 1,191
81 votes
9 answers
343k 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?
Felix's user avatar
  • 1,327
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 ...
Rocketmagnet's user avatar
  • 6,457
60 votes
2 answers
113k views

Why are capacitors added to motors (in parallel); what is their purpose?

I've seen many motors having capacitors attached in parallel in bots. Apparently, this is for the "safety" of the motor. As I understand it, all these will do is smoothen any fluctuations--and I doubt ...
Manishearth's user avatar
  • 1,833
44 votes
4 answers
122k views

What is stall current and free current of motors?

What are the stall and free currents of an electric motor? For example, this Vex motor lists its stall and free currents at the bottom of the page. I think I understand the general idea, but a ...
golmschenk's user avatar
  • 1,564
44 votes
11 answers
8k views

Programming Robots with JavaScript

As somebody who is spending the majority of his time programming in JavaScript, what's the best route to get into small-robotics without needing to deviate too much from my current language focus? ...
Sampson's user avatar
  • 681
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 ...
klonq's user avatar
  • 543
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 ...
rics's user avatar
  • 846
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 ...
Manishearth's user avatar
  • 1,833
37 votes
4 answers
46k views

Quadcopter liPo battery weight/capacity trade off

I'm trying to find where additional battery capacity becomes worthless in relation to the added weight in terms of a quadcopter. Currently with a 5500 mAh battery, 11.1V, I can get between 12 minutes ...
Chris's user avatar
  • 1,005
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 ...
Robz's user avatar
  • 2,162
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 ...
Mark W's user avatar
  • 420
32 votes
14 answers
17k views

Can ROS run on a Raspberry Pi?

Can ROS run on a Raspberry Pi? ROS is resigned to run on a network of machines, with different machines, even different cores on the same machine doing different jobs. Can one of those machines be a ...
Rocketmagnet's user avatar
  • 6,457
32 votes
1 answer
7k views

Why are Servo Motors so noisy?

I was working on a project to make a bedside night light out of a stuffed butterfly or bird. I was making a mechanism to make the wings flap with a servo motor and some small gears. The servo motor ...
Michael's user avatar
  • 423
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,...
ronalchn's user avatar
  • 3,094
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 ...
Jason Sperske's user avatar
29 votes
5 answers
34k 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 ...
Daniel Eberts's user avatar
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 ...
Robz's user avatar
  • 2,162
25 votes
5 answers
6k views

How can I integrate a smart phone with my robotics project? [closed]

Smart phones these days typically come with a gyroscope, accelerometer, compass, camera, and GPS sensor all on board. They also usually have a connection to the internet with Wifi and mobile data ...
Robz's user avatar
  • 2,162
25 votes
5 answers
29k 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?
Jordan's user avatar
  • 911
25 votes
3 answers
4k views

What algorithm should I use for balancing a two wheeled robot using a gyroscope?

Is there a good, popular and reliable algorithm I can use by taking input from a gyroscope and using this to control two independant wheels to keep such a balanced robot reliably upright? I'm looking ...
berry120's user avatar
  • 1,265
24 votes
4 answers
19k views

How should emergency stops be wired?

Emergency stops are obviously a good idea on most robots, how should they be wired? What systems should be killed immediately, and what should stay working?
Felix's user avatar
  • 1,327
24 votes
2 answers
667 views

What useful gaits exist for a six legged robot, and what are their pros and cons? [closed]

http://www.oricomtech.com/projects/leg-time.htm lists three gaits: the tripod wave, and ripple. Can these be improved, or can their relative pros and cons be altered, and are there other gaits worth ...
Sparr's user avatar
  • 341
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 ...
DaemonMaker's user avatar
  • 3,921
23 votes
3 answers
22k views

Why do quadcopters use brushless motors?

I've been thinking about starting a quadcopter project, maybe building it from scratch. One of the main barriers-to-entry for me is the motors: it seems like most quadcopters use brushless motors. I ...
Robz's user avatar
  • 2,162
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 ...
golmschenk's user avatar
  • 1,564
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 ...
David Cary's user avatar
  • 4,545
22 votes
2 answers
32k views

ROS: catkin_make vs. catkin build

When using ROS: Why should I use catkin build from catkin_tools instead of catkin_make? I've been told that ...
SKA's user avatar
  • 323
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 (...
David Cary's user avatar
  • 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 ...
ronalchn's user avatar
  • 3,094
22 votes
2 answers
1k views

Visualizing and debugging an EKF

I am currently debugging and tuning an EKF (Extended Kalman Filter). The task is classical mobile robot pose tracking where landmarks are AR markers. Sometimes I am surprised how some measurement ...
r0nald's user avatar
  • 321
21 votes
6 answers
17k views

What is the difference between path planning and motion planning?

What are the main differences between motion planning and path planning? Imagine that the objective of the algorithm is to find a path between the humanoid soccer playing robot and the ball which ...
Pooya Sagharchi's user avatar
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 ...
Robert's user avatar
  • 361
21 votes
3 answers
26k views

How to rotate covariance?

I am working on an EKF and have a question regarding coordinate frame conversion for covariance matrices. Let's say I get some measurement $(x, y, z, roll, pitch, yaw)$ with corresponding 6x6 ...
automatom's user avatar
  • 5,602
20 votes
10 answers
5k 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 ...
Shahbaz's user avatar
  • 3,250
19 votes
3 answers
30k views

Position Control vs Velocity Control vs Torque Control

Please can somebody explain to me the difference between Position Control, Velocity Control, and Torque Control? Specifically, I am thinking in terms of a robot arm. I understand that position control ...
Karnivaurus's user avatar
19 votes
7 answers
6k views

What good robotics software platforms / operating systems are available? [closed]

My company will soon be starting a brand new robotics project, and we are still trying to decide whether we should design and code a robotics software platform from scratch, or if there are any good ...
Rocketmagnet's user avatar
  • 6,457
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 ...
Mouse's user avatar
  • 313
19 votes
2 answers
11k views

How To Determine Heading Without Compass

Lets say I drop a robot into a featureless environment and any magnetic field based sensors (magnetometer/compass) are not allowed. What methods are there of determining where north is? Tracking the ...
user65's user avatar
  • 2,371
19 votes
3 answers
778 views

What's the most effective type of rechargeable battery when taking into account size / weight / Ah?

I'm looking to build an underwater glider robot that will need to remain autonomous for long periods of time, perhaps even months. Power draw should be minimal, and I'm thinking of including some form ...
berry120's user avatar
  • 1,265
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. ...
user avatar
19 votes
1 answer
4k views

ROS: Best practices?

I'm going to build a small robot system, and it seems like that ROS serves a nice framework to control and program the system. However, I am wondering which is the best practice to manage the ...
manf's user avatar
  • 193
19 votes
4 answers
27k views

Computing the Jacobian matrix for Inverse Kinematics

When computing the Jacobian matrix for solving an Inverse Kinematic analytically, I read from many places that I could use this formula to create each of the columns of a joint in the Jacobian matrix: ...
xenon's user avatar
  • 293
19 votes
2 answers
8k views

How to choose a good IMU for a wheeled robot?

At our lab, we have a several "Kurt" type robots (about the size of a Pioneer, six wheels, differential drive). The built-in gyroscopes are by now really outdated; the main problem is that the ...
Martin's user avatar
  • 4,243
18 votes
2 answers
23k views

Wheels vs Continuous Tracks (Tank Treads)

I'm building a small robot using some cheap Vex Robotics tank treads. However, my choice of picking tank treads is almost purely based on the fact that they seem like more fun than wheels. I don't ...
golmschenk's user avatar
  • 1,564
18 votes
4 answers
14k views

What is inverse depth (in odometry) and why would I use it?

Reading some papers about visual odometry, many use inverse depth. Is it only the mathematical inverse of the depth (meaning 1/d) or does it represent something else. And what are the advantages of ...
Mehdi's user avatar
  • 681
18 votes
3 answers
2k views

Why do Mars rovers designers prefer wheels over tracks?

Typically Mars rovers use wheels and not tracks. I guess Spirit would have better chances getting out of that soft soil should it have tracks. In general, Mars surface structure is not known in ...
sharptooth's user avatar
  • 1,191
18 votes
5 answers
33k views

How to detect when a stepper motor has stalled?

How can I detect when a stepper motor has stalled? A google search led me to some people who say that when the stepper motor stalls, the current spikes up, which is easily detectable with a Hall ...
David Cary's user avatar
  • 4,545
18 votes
3 answers
13k views

Calculating the efficiency of Mecanum wheels

I'm part of a FIRST Robotics team, and we're looking into using Mecanum wheels for our robot. What are the advantages and disadvantages of using Mecanum wheel versus regular ones? From looking ...
Michael0x2a's user avatar
18 votes
3 answers
5k views

What are good methods for tuning the process noise on Kalman filters?

Most often tuning the Kalman filter noise matrices is done by trial and error or domain knowledge. Are there more principled ways for tuning all the Kalman filter parameters?
Chris Mansley's user avatar

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