# All Questions

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### 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 ...
5answers
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 ...
9answers
209k 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?
2answers
91k 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 ...
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
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 ...
9answers
6k 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? ...
11answers
43k 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 ...
4answers
42k 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 ...
4answers
90k 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 ...
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,...
1answer
5k 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 ...
12answers
13k 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 ...
5answers
54k 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 ...
2answers
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 ...
6answers
23k 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 ...
3answers
3k 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 ...
5answers
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 ...
2answers
552 views

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

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 ...
5answers
22k 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 ...
4answers
25k 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?
9answers
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 ...
4answers
13k 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?
2answers
896 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 ...
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 ...
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 ...
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 ...
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 (...
7answers
5k 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 ...
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 ...
2answers
7k 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 ...
4answers
10k 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 ...
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 ...
3answers
678 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 ...
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 ...
3answers
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 ...
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. ...
2answers
20k 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: ...
3answers
3k 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?
4answers
8k views

### Single camera vision and mapping system

Some time ago I saw a demo of a small 'toy tank' with a single camera mounted on it. This tank was able to drive around the floor and detect objects and then move/steer to avoid them. The interesting ...
3answers
3k views

### Quadcopter Localization Beacon

I want to use an RF beacon to localize my quadcopter for autolanding, when GPS is not precise enough, for example, when my driveway is only 10 feet wide, and the GPS is only showing 20-30 ft. accuracy ...
2answers
18k 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 ...
4answers
6k views

### Will connecting two servo motors double the torque?

For my robot, I am using two continuous rotation servos to spin a threaded rod. I am trying to make this project as cheap as possible. Here are the servos that I can find: Servo #1: This is a very ...
3answers
21k 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 ...
2answers
6k 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 ...
1answer
1k views

### How does a six-axis force/torque sensor work?

I would really like a six-axis force/torque sensor for my robot, but I just can't afford one. I was thinking about making one of my own. I have experience using strain gauges, but I can't work out ...
2answers
2k views

### EKF-SLAM Update step, Kalman Gain becomes singular

I'm using an EKF for SLAM and I'm having some problem with the update step. I'm getting a warning that K is singular, rcond evaluates to ...
6answers
7k 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 ...
4answers
5k views

### How can I modify a low cost hobby servo to run 'freely'?

I've got some hobby servos (Power HD 1501MGs) and I'd like to be able to control them (via an Arduino) so they will either go to the angle I set, or put them in a 'free running' mode, where the load ...
2answers
680 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 ...

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