prismatic | color manipulation R package Simply and Tidy | Development Tools library
kandi X-RAY | prismatic Summary
kandi X-RAY | prismatic Summary
The goal of prismatic is to provide color manipulation tools in R, in a intuitive, low-dependency and functional way.
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QUESTION
I am trying to build and simulate a simple diff-drive robot under drake to get familiar with the components offered. I created a simple URDF which bases on existing PR2 URDF. I load the model with AddMultibodyPlantSceneGraph
. With following snippet,
ANSWER
Answered 2022-Apr-03 at 19:51The problem is that you passed the plant
to the Simulator
. You need to pass the diagram
. (The plant doesn't have the input port connected, only the diagram does).
QUESTION
I have imported a urdf model from Solidworks using SW2URDF plugin. The model loads correctly on Gazebo but looks weird on RVIZ, even while trying to teleoperate the robot, the revolute joint of the manipulator moves instead of the wheels. Is there anyone who has faced this issue before or has a solution to it? Here is how it looks on Gazebo
Here is the URDF file of the Model:
...ANSWER
Answered 2022-Mar-22 at 13:41So, I realized two problems:
First, you have to change the fixed frame in the global options of RViz to world
or provide a transformation between map
and world
.
Second, your URDF seems broken. There is something wrong with your revolute
-typed joints. Changing their type to fixed
fixed the problem. I think, it's best if you ask a separate question with a minimal example regarding this second problem.
QUESTION
I am working on a project and I do a simulation in a program called Prismatic to get files which I want to use later, Prismatic outputs files in h5 format, which I was able to extract data out of them using Python, the simulation produces an image, which is saved in two data sets (dim1, dim2), each is a numpy array of size 219 and I having trying to create the image from them again but I am not sure how that works, I tried to stack the numpy arrays but I just get a line in the image, I just learned about numpy arrays I don't know much about them yet, can anyone help? that's my code here.
...ANSWER
Answered 2021-Jun-14 at 20:10Ok Given your dataset,I managed to find an image.
QUESTION
I am building a two link system. The parent link is a curved object and the second link has a single degree of freedom to follow the curved length. I attempted to implement this with a prismatic joint but I can only define a linear path. How can I model this system in drake?
...ANSWER
Answered 2021-Mar-01 at 21:15You could use a joint with more degrees of freedom and then use a controller (e.g. PD) to force it to track the curve you want. If you really only need 1 dof you could use two prismatic joints; if the object needs also to be able to rotate you could start with a planar joint (two translations and a rotation) and use the controller just to constrain one of the dofs.
It is also possible to create a new joint type that would have a single dof and follow a curved slot. That would require some engineering though. The basic theory is covered in this paper which Drake follows closely.
QUESTION
In my block diagram I insert an Enumeration, call it "jointKind", and give it attributes "revolute", "continuous", "prismatic", "fixed" and "floating". Each attribute is Scope=Public, Stereotype=enum. Except for Name, Scope and Stereotype I left other fields (e.g. Type, Alias, Initial) empty.
I then create a block, called it "Robot", and give it a property. That property is typed by "jointKind". However when I chose an initial value I'm given an empty space to type my value.
I should think that when I choose an initial value then the attributes I previously assigned to the enumeration are mad available for me to chose from.
How to enforce enumerations on properties typed by Enumeration?
...ANSWER
Answered 2020-Nov-26 at 09:40You can't. EA doesn't limit the values you can enter in the initial value, regardless of the type of your property or attribute.
You can use this link to request this as a new feature: https://www.sparxsystems.com/support/forms/feature_request.html
If your really want to, you could create an add-in that checks the initial value of an attribute against it's type, and refuse any values that are not part of the enumeration. I'm not sure if it would be worth the effort though.
QUESTION
I am a newbie to HTML, CSS and JavaScript and I learned just enough to make a startpage. I have a search bar which toggles between two different search engines when an image element(here it's the logo of the search engine) on the side is clicked and also switches the image element to match the new state. Here's the JavaScript code:
...ANSWER
Answered 2020-Jul-13 at 20:15You can make use of the localStorage
feature of browsers to persist the current-preferred engine.
For example, you can add a document.onload
function to your script to check the value persisted in browser's localStorage
and update the logo in the searchbar on the basis of the persisted logo.
QUESTION
I have started to write some classes to compute the transformation along a kinematic chain. I'm having a templated parent class KinematicChainSegment
and multiple specialized implementations of it (e.g. for revolute or prismatic joints). To give a concrete, minimum example - this how I would like it to look:
ANSWER
Answered 2020-Jun-17 at 10:35You're trying to return an object of an abstract class by value. The problem is unrelated to using templates.
In C++ you need either a pointer or a reference for inheritance based polymorphism to work.
A simple solution would be to make inverse
return a std::unique_ptr>
and use std::make_unique
in the overriden functions.
This solution may not be ideal if you often use the object in a non-polymorphic way - as presented in your example - because it causes an unnecessary allocation and B bf = *b.inverse()
would be required which makes a copy.
It is possible however to preserve both interfaces.
QUESTION
I'm trying to find contact Jacobian defined as M(q) q_ddot + C(q, q_dot) = G(q) + B(q) u + J'(q) lambda.
I tried to mirror the function CalcNormalAndTangentContactJacobians()
as in multibody_plant.cc
link but the values are not adding up.
Here is how I setup the system (for the simplest setup possible):
I have a cylinder mounted to world through a revolute joint and a ball that can freely move in the x-y plant through dummy prismatic joints. I run the simulation that drives the joint at constant torque to make contact with the ball and push it off. I log the states of the system through simulation and find an instance when there is contact and look at that particular instance.
I set the MultibodyPlant(MBP) to the states as exactly in the simulation by SetPositionsAndVelocities
and SetActuationInArray
, and get the relative variables M, Cv, tauG, B, q_ddot, tauExt, and contactResults.
Now I'm ready to find the contact Jacobian. (Updated in reflection to the two suggestions from @Alejandro)
...ANSWER
Answered 2020-May-14 at 03:26Your problem seems to be in two places;
Problem 1QUESTION
In using a multibody plant (MBP) for estabilishing dynamics constraints for multibody system with contact, we look at the dynamics equation
M(q) q_ddot + C(q, q_dot) = G(q) + B(q) u + J'(q) lambda
where q is the states of the system, *_dot and *_ddot denotes *'s time derivative and double derivative, respectively; M(q) is the inertial matrix, C(q, q_dot) consists of the terms for Coriolis, centripetal, and gyroscopic effect, G(q) is the gravitational force, B(q) is the actuator matrix, u is the input (torque/force), J'(q) is the contact Jacobian transposed, and lambda is the contact force in the contact frame.
is there a way to get the contact Jacobian terms J(q) from the plant or is it up for the users to implement it with the contact results?
Question Update:
I've been trying to verify the returned results from hand-derived Jacobian and there is some mis-matching that I don't understand.
First, I constructed a very simple system: a link fixed to world through a revolute joint and a sphere that can roll in the x-y plane through dummy prismatic joints. The link is named left proximal. The contact Jacobian is easy to derive by hand with contact point returned from contactResults
using which, the contact dynamics is verified.
Now, here is how I find contact jacobian from drake functions:
...ANSWER
Answered 2020-May-07 at 20:40I think the recommended workflow is to get a QueryObject
from the SceneGraph
output port. On this QueryObject
you can call ComputeSignedDistancePairClosestPoints()
, to find the closest points on each pair of bodies. The distance between these two points is what we call φ(q) in the notes. Then you can call the Jacobian methods on MultibodyPlant
to take the gradients of φ with respect to q.
QUESTION
I am not able to run "lein ring uberjar" from my local machine. I get the following errors:
...ANSWER
Answered 2020-Apr-02 at 14:44I think my JVM's CA settings got mucked up, I was able to resolve this issue by:
- Downloading the missing .crt file via browser.
- Adding .crt file to key store.
keytool -import -trustcacerts -file [.crt file path] -alias [alias] -keystore $JAVA_HOME/lib/security/cacerts
- Checking .crt file was definitely added to the key store
keytool -list -keystore $JAVA_HOME/lib/security/cacerts
- Reran
lein ring uberjar
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