Questions tagged [manipulator]
manipulator is a device used to manipulate materials without direct contact.
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UR robots always have 2 parallel axes. Why not at a singularity?
I thought I understood the Jacobian and singularities pretty well, but then I was asked: UR robots (and others) have 2 joints that are always in parallel. Doesn't this put the robot at a singularity ...
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Why the robot is not at the zero configuration
As part of my testing, I was using Kuka's arm to test some kinematic controllers. In the picture below, when the arm is spawned in Gazebo, the positions of the joints are zero (i.e. obtained from <...
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DH parameters of a serial manipulator RRRRRR
I am trying to find the forward kinematics of this manipulator in the picture using DH notation. All of the joints are rotational.
I managed to get to the third joint. The parameter table is below.
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ROS Openmanipulator-X: it recognized AR marker, but don't move
Our team is following this manual, and we have run into an error when attempting to call the /set_actuator_state and ...
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How to define the degrees of freedom of a flexible manipulator?
Consider a cable-driven flexible manipulator which has 3 cables. Consider the 3 cables to be actuated by 3 motors. Assume that by pulling the three cables in different configurations, we can span the ...
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Standard Notation/Name for Velocity Transformations
I've been looking to see if there's any standard notation for a matrix to convert an end-effector velocity vector $\xi_n^0 = \begin{bmatrix} v \\ \omega \end{bmatrix}$ from one frame of reference to ...
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Robotic Manipulator 3-RRP v2
I recently asked a question about a 3-RRP manipulator but the only answer didn't work for my robot.
I would describe the manipulator as an arm that rotates around the shoulder over the x-y axis, the ...
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How to calculate operating torque and holding torque of a slew drive for a manipulator arm?
Hope you are doing good and enjoying your weekend.
I have a question regarding calculation of torque and tilting moment for a slew drive. Slew drive (motorised) will be used at the base of a ...
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DH Parameter for OpenManipulator X from Robotis
I try to solve forward kinematics problem for OpenManipulator X from Robotis by using standard DH convention. The figure and dimension of the robot like this pic
I try to find DH parameter and got ...
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When assigning frames in Denavit-Hartenberg (DH) parameters, where do I put the frame on end effector?
I have a simple question, for the last link (end effector) I need to estimate the parameters but when I put the reference frames in the center of the end effector, I just don't know.
Last link (end ...
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Parallel spatial mechanism - DOF
The parallel mechanism is composed of a moving platform
and a base (or frame) connected by four legs. Each leg is composed of five
revolute joints numbered 1, 2, … 5 from the base to the moving ...
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How do I assign the origin of the frames in the Denavit Hartenberg convention?
I am studying the Denavit Hartenberg and to practice I am using the following manipulator:
I have been able to assign some of the frames almost correctly, but i did some mistakes I cannot understand. ...
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Where can I find 6 DOF manipulator packages for gazebo?
Hello. Where can I find 6 DOF manipulator with a 4-wheel mobile base packages for gazebo?
Thanks.
Originally posted by NickRos on ROS Answers with karma: 1 on 2023-02-14
Post score: 0
NickRos
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How to calculate Exponential coordinates of end_effector from Transformation matrix
I want to know Exponential coordinates of end effector $\text{S}\theta$(6-vector) from end effector transformation matrix. I calculated the transformation matrix of the end effector from the forward ...
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Question about Impedance control in The Modern Robotics: Mechanisms, Planning, and Control
Impedance equation In 11.7.1 section $\tau = J^T(\theta)(\hat{\Lambda}(\theta)\ddot{x}+\hat{\eta}(\theta,\dot{x}) - (M\ddot{x}+B\dot{x} + Kx))$ is actually means $\tau = J^T(\theta)(\hat{\Lambda}(\...
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How to add gripper to robot arm and plan according to the end effector on Moveit
Hello! I am simulating for a university project, the Elfin 5 robot arm which package can be found here along with a gripper which package is found here.
Being new to Moveit, I am finding trouble to ...
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Grasp matrix implementation
I've majorly followed Dex-net implementation to calculate a grasp matrix (G) to compute other grasp quality metrics (e.g., Ferrari Canny L1 metric or smallest singular value of G).
Based on my ...
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For robot manipulators what is the relationship between angular velocity and time derivative of quaternions?
For a robot manipulator with joint angles $\theta$, the well-known relationship is
$$\omega = J_\omega(\theta)\dot{\theta}.$$
What if the angular velocity is represented as the time derivative of ...
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Newton-Euler Inverse Dynamics by Screw
I paste this algorithm from textbook Modern Robotics P294 in chapter 8:
This is coordinate invariance of Newton-Euler equations. In the textbook, they use the ...
Ben♦
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Meaning of p(q) in the expression for minimum clearance from obstacle for redundant robotic manipulators
Can somebody who has studied Industrial manipulators or has worked on Industrial manipulators using Jacobian Inverse and Jacobian Pseudo inverse algorithm for Inverse Kinematics please explain what ...
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Why does the Denavit-Hartenberg representation fail to capture the length of the last link in my model?
The length of the last link (1.73) of my model (of a human finger) is not represented in any of the parameters that I calculated using the Denavit-Hartenberg algorithm, which I think can't be right. I ...
Ben♦
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definition of self motion
From my understanding, self motion refers to a set of joint velocities which doesn't cause any cartesian motion on the end-effector. Here, by motion it is meant both linear and angular components or ...
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Design optimization method using indices
There are several methods like manipulability and conditioning index for design optimization kinematics performance, but these methods rely on the singular values of the jacobian matrix. I described ...
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Redundancy and Null space projection
I'm reading "Theory of Robot Control" by Carlos Canudas Wit, Bruno Siciliano, Georges Bastin. In Task space control chapter, exploiting the redundancy by means of null space as shown below ...
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Implementing a torque-controlled method on a position-controlled robot
I am working with a position-controlled manipulator. However, I want to implement a torque-controlled method on this robot. Is there any way to convert a torque command to a position command?
I try ...
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Why applied joint torque will affect another joint?
I want to ask a very simple question.
For the robot dynamics Newton-Euler algorithm, suppose there is a two-link planar robot, we can write the simple dynamic equation form as $M(\theta)\ddot{\theta} ...
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How to find workspace of parallel manipulator by monte carlo method?
I am working on a 3 DOF parallel manipulator, I was successful in solving the inverse kinematics and forward kinematics of my manipulator. But I am facing a problem in generating a workspace for it.
I ...
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Is this motion possible for this manipulator?
I'm currently solving the exercises of Modern Robotics book. I came across this problem but it is not clear to me how to approach it. I computed the analytic Jacobian which is
$$
\begin{bmatrix} \dot{...
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Equations of motion with mass attached to end effector and external force
I have to find the equations of motion for the given manipulator:
The links of the manipulator are considered weightless and the equations of motion have to be derived by using the Lagrange equations....
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How to obtain the Jacobian matrix for this 2Planar without differentiation
Take a look at the below picture, I would like to derive the Jacobian matrix without differentiation. In this Modern Robotics book, the screw theory is used. I've derived the forward kinematic using ...
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Degrees of Freedom
What is the Degree of Freedom for a k-link planar serial chain for k = 2, 3, 6?
Using Grüber Formula, I get k-link chain has k Degrees of Freedom. But the maximum DoF in a plane can be 3. I am not ...
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Feed-forward controller with lookup table
does anyone have experience in implementing a feed-forward controller for a hydraulic cylinder?
Often, when a hydraulic cylinder is controlled with PWM values, people (https://drive.google.com/file/d/...
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How to calculate potential enegy of manipulator?
I'm trying to obtain dynamics of a 4 DOF robot. Firstly, I calculated all Transformation matrices and Jacobians. While solving Lagrangian there is two main things one is kinetic energy and the other ...
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Pose of the end-effector
I am trying to get the pose of the end-effector. I have attached the picture. I am stuck. I wrote the transformation matrices - I am not sure how to move forward next. How do I find the end-effector ...
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How to calculate holding and operating torque at the base?
Could anyone please help me with the formula to calculate the operating torque and holding torque at the base to rotate the structure on top of it as shown in image with white arrows?
Thank you in ...
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C space for R5 manipulator
Trying to create a collision avoidance model (RRT) for an RRRRR manipulator. I am unable to wrap my head around how to represent the same in configuration space. Anything upto 3 joint variables is ...
Ben♦
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Why do current manipulators tend to use 7 DoF instead of 6 DoF?
In theory, controlling a 6D pose (3D position + 3D orientation) would require 6 joints, and - assuming the robot is carefully designed - the inverse kinematics should be solvable for that case.
Adding ...
Ben♦
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Why are serial manipulators almost always made of single dof joints?
I am currently taking my first robotics class and I found it curious that all serial manipulators have single dof joints. Why not use joints with more dof and reduce the number of components? Will ...
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Forward/inverse kinematics and transformation matrices
I have found the homogeneous transformation matrix that can be used to determine the relation between the parent and child links of a robot. This matrix is shown below.
$T_i =
\left[\begin{array}{ c ...
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Why is a joint space trajectory unable to deal with operational space obstacles?
I have found several sources that state that a Joint space trajectory model is not capable of dealing with obstacles in the manipulator workspace. These sources include:
slide 10 of "Manipulator ...
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homogenous transformation matrix variants
I am working on some manipulator projects and come across a few variants of the homogenous transformation matrix. I've been working on matlab and they give slightly different answers. Assuming both ...
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How to draw robot manipulator diagram
I've been seeing a lot of these diagrams online and wondering how can I replicate this myself. Is there any easy-to-use software package that will allow me to draw these diagrams quickly and ...
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SLERP velocity and acceleration (3d Orientation interpolation)
Hey guys I am quite new to quaternions and I am a bit unsure as to how to use them. How are the velocities and accelerations trajectories determined using quaternions?
I have been using slerp to ...
Ben♦
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How do I select the best configuration for a known workspace, load and task?
Given workspace constraints, load and task to be done, how do I select the best configuration of my robot? How do I select between a cartesian or Scara robot for instance? How do I select a ...
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How can i consider orientation of 6dof manipulator for inverse kinematic?
i been trying to code IK solver for few days, and i finally move the robot to the desired position.
However im having hard time to orient the end-effector as i want it.
I read the "Robotics ...
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Force-torque sensor reading when a robot is stationary
Let's say I have a robot arm with a force-torque sensor on the wrist, between the final motor and the gripper. If the arm and wrist are stationary, then what would the reading on the sensor be?
I know ...
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How to find the body jacobain, for each link in a robot manipulator?
The links twist could be obtained, and thus The spatial manipulator Jacobian could be done, but when it comes to the body Jacobian, it is becomes difficult. Moreover, the adjoint transformation ...
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Robotic manipulator Jacobian by product of exponentials
I've taken a class and started a thesis on robotics and my reference for calculating the Jacobian by product of exponentials seems incorrect, see:
http://www.cds.caltech.edu/~murray/books/MLS/pdf/...
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Developing world-frame Jacobian using product of exponentials [closed]
I am going through different texts (Spong Robot Modeling and Control, Murray Mathematical Introduction to Robotic Manipulations) and I am seeing different Jacobians developed for the same RRRP ...
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Different methods to determine DOF: Chebychev-Kutzbach-Grubler method vs. Screw method
I'm familiar with Chebychev-Kutzbach-Grubler method to determine degree of freedom of a robot arm. But it seems this method fails to calculate the mobility of some parallel robots, as explained here.
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Ben♦
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