8
votes
Accepted
Calculating Required Torque
This is a standard dynamics problem. Let's use this figure I drew:
Some definitions:
$$
\begin{align}
m & \mbox{, the mass of the vehicle in kg.} \\
\mu_{\mbox{rolling}} & \mbox{, the ...
- 15.9k
7
votes
Accepted
What does SE mean in robotics literature?
In that context, SE means "Special Euclidean" group, e.g. SE(3)* which is shorthand for "the special Euclidean group of rigid body displacements in three-dimensions".
*Planning ...
- 1,054
4
votes
Explanation for exponential coordinate of rotation
The author expects a background that includes a course in physics or mechanics where this equation is taught. When that is the case, this equation gives you instantaneous velocity of a particle (point)...
- 4,355
4
votes
Accepted
Motion planning from a given path
Many articles reference algorithms such as A*, PRM or RRT based planners to motion planning algorithms which seems unreasonable since it is still necessary to parametrize found path with time.I wonder,...
- 1,829
4
votes
What does SE mean in robotics literature?
It is a mathematical concept call the "Special Euclidean" group. Roughly, it is a combination of a rotation and translation. You'll also frequently see SO3, which is the special orthogonal group which ...
- 2,794
4
votes
What are the equations of a s-curve position path?
The S-Curve profile can have several divisions along the time axis
7 divisions as per this image. This example has a constant positive jerk zone, a constant acceleration zone, a constant negative ...
- 671
3
votes
Accepted
State estimation of mobile robot
My solution is to use the following model with disturbance only at acceleration and curvature.
$$
\begin{bmatrix}
x_{k+1} \\
y_{k+1} \\
\theta_{k+1} \\
v_{k+1} \\
a_{k+1}...
- 218
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 ...
- 1,843
3
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 ...
- 1,402
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 ...
- 3,995
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
3
votes
Accepted
Why aren't more bipedal (or even quadruped) robots made with joints/articulations similar with those found on atmospheric deep dive suits?
Why aren't they, you ask? Typically, it would be a worse design.
Atmospheric deep dive suits, and, for that matter, space suits, are designed to maintain constant internal volume. Otherwise the ...
- 1,271
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
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
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
Probably basic question about how control a DC motor
Since the encoder with that motor is an incremental encoder, you would have to keep track of the motor position constantly.
If you really want to go to a home position, you'll need another sensor, ...
- 572
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 ...
- 1,402
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 ...
- 1,829
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 ...
- 385
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 ...
- 1,891
2
votes
Bump and turn toys: how do they work?
I think I know exactly what you are talking about. I don't know the physics of it all but it's not castor wheel or microswitch.
They are called 'Bump and go' toys which uses "universal/bump and ...
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 ...
- 618
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 ...
- 6,632
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( -...
- 3,995
2
votes
Accepted
Dynamical footprint in Nav2
The "easy" solution would be to use a footprint that covers the robot in any configuration - the downside is that footprint is likely quite large and if you are planning in confined areas, ...
- 5,912
1
vote
Controlling YuMi robot by serial port
There is an open source ROS library, which implements controlling an ABB robot using the EGM. You can find the library here.
The library allows the definition of a trajectory and adding points to the ...
- 6,632
1
vote
Accepted
Ackermann Motion Model Does not Drive in an Arc, but Turns on the Spot
The first ackermann model presented is based on dead reckoning, i.e. it needs wheel encoders. The ackermann model in edit 2 is based of velocity.
It can be found here:
https://pdfs.semanticscholar....
- 151
1
vote
Motion Profiling for Decreasing Energy Consumption
To paraphrase your question, you are using "bang-bang" control to keep the velocity of your vehicle within a desired range, and want to know if there is a better way to minimize energy consumption per ...
- 4,386
1
vote
Jacobian of kinematic IMU Model
A robot Jacobian is
The time derivative of the kinematics equations [...] which relates the joint rates to the linear and angular velocity of the end-effector.
I'll emphasize that it
relates ...
- 15.9k
Only top scored, non community-wiki answers of a minimum length are eligible