Robotics Stack Exchange
Robotics Stack Exchange

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1500 questions
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2 answers

What are methods for dealing with compass lag (rate dependent hysteresis)?

I've got a tread-driven robot, with low precision wheel encoders for tracking distance and an electronic compass for determining heading. The compass has significant (> 1 second) lag when the robot turns quickly, e.g. after reaching a waypoint —…
ViennaMike
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Odometry vs Dead-reckoning

In terms of robotics, what are the differences between odometry and dead-reckoning? I read that odometry uses wheel sensors to estimate position, and dead-reckoning also uses wheel sensors, but "heading sensors" as well. Can someone please…
John
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Ambiguous definition of Error-State (Indirect) Kalman Filter

I am confused by what precisely the term "Indirect Kalman Filter" or "Error-State Kalman Filter" means. The most plausible definition I found is in Maybeck's book [1]: As the name indicates, in the total state space (direct) formulation, total…
sebsch
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How to get two continuous tracks (tank treads) to move at the same rate?

I've got a couple Vex 269 Motors hooked up to an Arduino Duemilanove. These motors run a some Vex Tank Treads. The two motors are run as servos on the Arduino using the Servo Library. The problem I'm having is that the two tracks don't turn at the…
golmschenk
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What's the most accurate way to obtain a locational fix using GPS?

Obviously GPS is the most obvious and accessible technology for obtaining a locational "fix" for a robot at any particular time. However, while it's great sometimes, in other locations and situations it's not as accurate as I'd like, so I'm…
berry120
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3 answers

In PID control, what do the poles and zeros represent?

Whenever I read a text about control (e.g. PID control) it often mentions 'poles' and 'zeros'. What do they mean by that? What physical state does a pole or a zero describe?
Rocketmagnet
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Virtual Testing Environment for Drones

Does anyone know of a robotics developer environment ideal for testing AI programs for drones (e.g. quadrocopters, planes, helicopters, etc.)? I would like something like Microsoft Robotics Developer Studio that includes a virtual environment (such…
oalbrecht
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Choosing the right dimensions for an underwater glider

I'm looking to potentially build an underwater glider, a type of submarine that's slow but can operate on extremely low power draw. However, in order for it to work effectively I've found several sources hinting that the dimensions of the…
berry120
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Why should I still use EKF instead of UKF?

The Unscented Kalman Filter is a variant of the Extended Kalman Filter which uses a different linearization relying on transforming a set of "Sigma Points" instead of first-order Taylor series expansion. The UKF does not require computing Jacobians,…
sebsch
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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 representation? I can understand the interest of having a…
Thomas Moulard
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What do the commutation waveforms look like for a brushless motor?

I have seen waveforms for driving a brushless motor. I guess this is the waveform used for the simpler block commutation. But if I want to do sinusoidal waveforms, what does the PWM signal look like now? Is there a need to carefully synchronise the…
Rocketmagnet
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Starting out advice on making robots and tinkering with microcontrollers

I'd like to start making robots and tinkering with microcontrollers. Where do I start, and what do I need? I'd like to make my own robots. I'm comfortable with programming (assembly and C) so I've got that part covered, but my electronics/circuits…
Aitul
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Smooth servo movement for a crawling robot

I made a small crawler robot a little while ago that had two legs with two degrees of freedom each, so 4 RC servos total. While I was programming the movement of the legs I noticed that they moved rather stiffly. It makes sense that the RC servo's…
Robz
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What is the difference between a Robot and a Machine?

What is the difference between a Robot and a Machine? At what point does a machine begin to be called a robot? Is it at a certain level of complexity? Is it when it has software etc?. For instance: A desktop printer has mechanics, electronics and…
user797
12
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4 answers

Fixed point arithmetic on microcontrollers

Often we use microcontrollers to do things in our robots, but need to make some calculations in decimal. Using floating point variables is very slow, because a software floating point library is automatically included (unless you have a high-end…
ronalchn
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