29
votes
Accepted
What is the difference between path planning and motion planning?
Compare the following two images:
The path planning is somewhat trivial. There's only one path: the rope. The motion planning on the other hand is not that easy.
In a maze the path planning is hard ...
- 1,425
11
votes
What is the difference between a holonomic and an omnidirectional robot?
Holonomic is a precise mathematical term; one definition is velocity constraints can be integrated into the form
$$\begin{align}
f(q1,q2,...,t) = 0.
\end{align}$$
Roughly, that means the ...
- 2,794
9
votes
Accepted
How exactly does sensor fusion work in Kalman filters?
I realize this question already has an accepted answer, but I'd like to provide some additional input. The question of sensor fusion is a good one, but, depending on the application, you don't ...
- 126
8
votes
Alternative to ROS?
I think you are getting confused between the basic ROS possibilities and some more advanced libraries which are integrated but do not need to be used by users without 'advanced' requirements. If you ...
- 1,402
7
votes
Accepted
Finding Center of Mass for Humanoid Robot
Yes. As @hauptmech mentioned, you can use your forward kinematics to get the center of mass of each link in the base frame. Then you can simply compute the weighted average of the masses and ...
Ben♦
- 5,825
7
votes
Motor Choice given size constraint and load requirement
If you have some budget for your project, both Maxon and Faulhaber have good DC motors and motor-gearhead combinations.
Maxon publishes a nice set of formulas and background theory on electric motors....
- 4,385
7
votes
Accepted
How many robots is considered to be a robotic swarm not a group of robots?
A robot swarm is defined by its behaviour, rather than the number of robots it contains. Swarm robots:
"... are coordinated in a distributed and decentralised way"
[Iñaki Navarro and Fernando ...
- 1,054
6
votes
What is the difference between path planning and motion planning?
What's the difference between turn-by-turn GPS and driving a car?
GPS is path planning: high-level commands like, "turn right in 1 mile."
Driving is motion planning, which means following a route ...
- 16k
6
votes
Understanding Drift in Simultaneous Localization and Mapping (SLAM)
Your intuition is mostly correct. Returning to where you started and re-observing landmarks you mapped earlier is called closing the loop in the SLAM literature. As you mentioned, your uncertainty ...
- 980
6
votes
Accepted
Why would a drone need a magnetometer? Are an accelerometer and a gyroscope not sufficient?
The main difference between accelerometer and gyroscope vs magnetometer is that first two give only relative information - you may calculate heading relative to your starting position, but you won't ...
- 953
6
votes
Accepted
Stabilising an inverted pendulum
There are lots of ways to solve this problem, which falls into the category of Control Engineering. There are two standard approaches:
Classical Control: The control command has to be proportional ...
- 1,268
6
votes
Motor Choice given size constraint and load requirement
20kg is a mass. It makes a force on Earth (20*9.81 = 196N), but that's not a torque. Motors make torque - what is your maximum torque specification?
Once you know how much torque you need (that will ...
- 16k
6
votes
Is there any robot stability control equation that describes the relation between velocity of the robot and its orientation?
That's not obvious. If I'm in a tank, going 0.5 km/h, I don't need to slow down at all. If I'm in a bobsled going 100km/h and the track banks, I don't need to slow down at all.
When you steer, you ...
- 16k
6
votes
Accepted
How to measure pull force on a (kite) rope?
The component you highlighted is called a tensile load cell. You could buy one from a supplier, but it probably would be cheaper to buy a cheap digital hanging scale and taking the sensor out of it - ...
- 521
6
votes
Which is a good and cheap 3D LIDAR or other options?
There are now some sub and around ~1000USD 3D Lidars available. I wanted to provide an answer for future reference if anyone else comes looking for "cheap" Lidars.
LeddarTech M16 ~500 USD ...
6
votes
What's the difference between Pose Measurement and Position Measurement?
what you are looking for is written in the paper. Position refers only to x,y,z translational measurements while pose means position and orientation.
- 497
5
votes
image processing
Ball detection using vision is not extremely difficult, especially if the ball is easy to recognize. There are a lot of tutorials and blogs which give a detailed explanation on how to implement an ...
- 260
5
votes
Accepted
Is modelling a robot and deriving its Equations of Motions more applicable to a system that is inherently unstable?
A system is (marginally) stable if all of the poles are (equal to or) less than zero. In general, the poles of a system determine whether a system is stable or not, and the zeros of a system determine ...
- 16k
5
votes
Accepted
Humanoid balancing
Keep in mind that the ZMP is a simplification. In practice with walking robots the support polygon is constantly changing so it can be tough to keep the ZMP inside.
Pregenerated (offline) ...
- 4,385
5
votes
How to align solidworks global origin with assembly origin while exporting in solidworks to urdf
I did a little step-by-step tutorial with images, but if my other answer regarding aligning frames didn't work well for you, or the definition of "Front Plane" or "Top Plane" is confusing in ...
- 16k
5
votes
Best sensor to determine "up" versus "down"
if you aren't moving, the accelerometer will give you the direction of gravity. if you are moving and hoping to use this orientation data for control you'll need to incorporate at least one more ...
- 1,853
5
votes
What's the diffrence between $H_2$ and $H_\infty$ control?
In short answer:
yes
Kalman filter is a special case of an $H_2$ observer
Yes
Yes ... LQG is just Kalman filter + LQR controller, which are both special cases of $H_2$
Depends on the use case. $H_2$ ...
- 2,794
5
votes
Accepted
In SLAM loop closure, What does a sim3 matrix do?
Sim3 is just the lie group associated a similarity transform which is the exact same thing as your 3D Affine transform. If you work out the multiplication for your two matrices you would find that ...
- 1,831
4
votes
Accepted
Robot arm reachability of a pose in Cartesian space
Nowadays we no longer employ exact solutions for the IK problem, simply because the number of degrees of freedom so as the number of constraints the final configuration needs to comply with make the ...
- 3,995
4
votes
Accepted
Angular velocities and rotation matrices
If your object $O$ has a different orientation from your global frame $S$, and you know what that difference in orientation is, you can create a 4x4 transform matrix between the two:
$$
T = \left[ \...
- 16k
4
votes
Accepted
Weird magnetometer values
Apparently a magnetometer is useless in indoor environments like man made buildings. I cite from this paper
Multi-Magnetometer Based Perturbation Mitigation for Indoor Orientation Estimation
...
- 681
4
votes
Accepted
Best power solution for my robot
I agree with @Greenonline 's recommendation regarding LiPo batteries along with his warnings on battery care. It seems you will need a fairly small battery, considering your current requirements (...
- 550
4
votes
Computer stereo vision simulator
I highly advise against using synthetic image data for testing your stereo vision algorithms. What will happen is that you end up with a system that works excellent on your synthetic data, but poorly ...
- 41
4
votes
Relationship between motor torque and acceleration
1) but the more torque, the faster the robot's acceleration: YES
$$
F=\frac{Torque}{wheelradius}
$$
and robot's acceleration is
$$
a=\frac{F}{m}
$$
so, from that equation you can see that linear ...
- 470
4
votes
Accepted
Relationship between motor torque and acceleration
Based on the calculations, it seems that any amount of torque can get
the robot moving
That is true only for a theoretical robot moving in vacuum without any friction in its mechanisms. Normally if ...
- 953
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