8
votes
Accepted
Calculating Required Torque
This is a standard dynamics problem. Let's use this figure I drew:
Some definitions:
$$
\begin{align}
m & \mbox{, the mass of the vehicle in kg.} \\
\mu_{\mbox{rolling}} & \mbox{, the ...
- 14.7k
7
votes
Accepted
What does SE mean in robotics literature?
In that context, SE means "Special Euclidean" group, e.g. SE(3)* which is shorthand for "the special Euclidean group of rigid body displacements in three-dimensions".
*Planning ...
- 1,009
5
votes
How to convert vertical motion to horizontal?
Scott-Russell type mechanism. For weeks I was trying to come up with a solution for that exact problem for a engineering project mine. Look it up.
- 61
4
votes
Is there any advantage to velocity motion models over odometry motion models for SLAM?
I can't think of a reason why a velocity model (based on control commands)
would be superior to an odometry model (which uses the actual wheel speeds).
The lecture notes from Freiburg on motion ...
- 2,954
4
votes
What does SE mean in robotics literature?
It is a mathematical concept call the "Special Euclidean" group. Roughly, it is a combination of a rotation and translation. You'll also frequently see SO3, which is the special orthogonal group which ...
- 2,679
4
votes
Accepted
Motion planning from a given path
Many articles reference algorithms such as A*, PRM or RRT based planners to motion planning algorithms which seems unreasonable since it is still necessary to parametrize found path with time.I wonder,...
- 1,799
4
votes
Explanation for exponential coordinate of rotation
The author expects a background that includes a course in physics or mechanics where this equation is taught. When that is the case, this equation gives you instantaneous velocity of a particle (point)...
- 4,235
4
votes
What are the equations of a s-curve position path?
The S-Curve profile can have several divisions along the time axis
7 divisions as per this image. This example has a constant positive jerk zone, a constant acceleration zone, a constant negative ...
- 661
3
votes
Motion Model for Holonomic Robot
I agree that the motion models in Probabilistic Robotics are badly suited for omnidirectional robots. I always interpreted the models presented there as examples only that should enable you to devise ...
- 629
3
votes
How to turn a rover 90 degrees using wheel encoders?
All theory aside, circumferences and actual distances travelled will vary with your wheel geometry since your wheels aren't perfectly tangential to their direction of travel while turning. While Ian ...
- 1,027
3
votes
Accepted
Velocity Model Motion in Matlab (Probabilistic Robotics)
There are several traps you might have stepped into, but it is difficult to tell without more information. The first issues that came to my mind:
The equations you wrote down are for sampling from ...
- 629
3
votes
Compensation for IMU mounting misalignment
You need the transformation from the car to the IMU.
You can get this by recording the IMU published attitude with the car in known orientations.
You should be able to construct the IMU to car ...
- 1,825
3
votes
What does SE mean in robotics literature?
$SE(3)$ is the representation for both translation and rotation in 3D space, whereas $SO(3)$ is only the representation for rotations. $\mathbb{R}^3$ is for translations in 3D space.
If you only ...
- 31
3
votes
Accepted
What are the equations of a s-curve position path?
To come up with a mathematical expression of the position reference $x\left(t\right)$ as a function of time $t$, we can inspect the profile of the acceleration $a\left(t\right)$. It is piece-wise ...
- 3,575
3
votes
Accepted
Omnidirectional Movement for 3 Wheeled Spherical Omni wheel robot
I think this is not really difficult trigonometry. Suppose we want the robot to move in a forward direction? We need to use the two front motors. (I tried to sketch this out in the pictures, I will ...
- 158
2
votes
What are some good cheap, silent, motors for mannequin robots and what kind of controller should I use?
The majority of the noise you're hearing is not from the motor itself but from gearing, which both servo motors and drills have a lot of. However, if you don't have a gearbox then when power is cut ...
- 306
2
votes
How to convert vertical motion to horizontal?
This should have probably been a comment to @RobertEnglish answer ... but comments don't seem to allow pictures
Bavel gears. Plastic ones should be rather inexpensive.
- 137
2
votes
Best technique to built an ejectable drawer?
Assuming you need only to eject the drawer automatically and can close it back manually, I would suggest using compressed spring which would push out the drawer if there is no resistance.
A hook or ...
- 121
2
votes
Is there any advantage to velocity motion models over odometry motion models for SLAM?
Through my reading of this book "Probabilistic Robotics" chapter 5 pp. 120,121. It seems what you thought is right. And this is the reason the authors mentioned.
Many commercial mobile robots (e.g....
- 2,347
2
votes
Accepted
State estimation of mobile robot
My solution is to use the following model with disturbance only at acceleration and curvature.
$$
\begin{bmatrix}
x_{k+1} \\
y_{k+1} \\
\theta_{k+1} \\
v_{k+1} \\
a_{k+1}...
- 198
2
votes
Accepted
Finding cubic polynomial equation for 3 joints
I guess you want to find a cubic polynomial for the end effector. You have 3 coordinates for your points A and B, from your question is not clear if they are $x,y,z$ or $x,y,\theta$. Anyway, I'll show ...
- 341
2
votes
Accepted
Motion planning and robot controlling
The model you have given is called the unicycle model and is widely used n robotics. In general the model is given by
\begin{eqnarray}
\dot{x} &= v\cos \theta \\
\dot{y} &= v\sin \theta \\
\...
2
votes
Accepted
Why don't bipedal robots ever feature natural movement?
From my side I can provide two remarks.
First the human have elastic actuators (muscles) with a lots of sensors for balance. Whereas robots have mostly rigid actuators with a few dampers here and ...
- 1,327
2
votes
Accepted
Quadrotor SE3 Controller: Calculating Rd_dot
In this paper rotation matrices are used to describe the orientation of the quadrotor. This is chosen because each orientation as a single representation (contrary to quaternions) and gimbal lock is ...
- 1,327
2
votes
Accepted
Explanation for exponential coordinate of rotation
First note that
$p(0)$ travels along an arc of the circle of radius $r = \Vert p \Vert \sin(\phi)$ centered at a point on the axis of $\omega$; and
the velocity $\dot{p}$ is perpendicular to the arc ...
- 1,799
2
votes
A powerful pull/rotate device that provides a certain (controllable) force?
If I understand your question correctly, it seems to me that you are looking for a DC torque motor (brushed or brushless) with a suitable sensor attached to the load or to the output shaft. The sensor ...
- 375
2
votes
Bump and turn toys: how do they work?
There's two parts.
The wheel you're remembering is a castor wheel that's designed to stick at straight forward when the car is going forward, and will turn to about 20 degrees when the car goes ...
- 1,881
2
votes
Name of imitating motion technique in Robotics
A robot manipulator that’s designed to mimic an operator in real-time can be called a “waldo” or "telemanipulator". The term "waldo" originates from Robert Heinlein, and was widespread enough at least ...
- 609
2
votes
Real Time Motion Control
The key elements to real-time motor control is the motor controller and the motion controller (which can be a CNC, a robot controller or other type of controller). The following description fits most ...
- 6,437
2
votes
Accepted
Equations of motion with mass attached to end effector and external force
In Lagrangian mechanics, you're required to deal with the generalized forces and the concept of virtual work $\delta W$.
In our case we have:
$$
\delta W_{F_x} = F_x \cdot \delta q_1 + F_x \left( -...
- 3,575
Only top scored, non community-wiki answers of a minimum length are eligible