# Questions tagged [manipulator]

manipulator is a device used to manipulate materials without direct contact.

156 questions
Filter by
Sorted by
Tagged with
382 views

### 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 ...
28 views

### How to model the Cable composites in Mujoco Physics Simulation engine

How to name the cable composite in mujoco, also how to add equality constraint to the end of the cable with another body ?
28 views

### Why is admittance control better than impedance control for huma robot collaboration?

I have seen many papers that use admittance control for human robot collaboration but no one tells why admittance is the choice and not impedance. Is it something very trivial that I should know or ...
1 vote
295 views

### 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 ...
72 views

### 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 ...
23 views

### Transformation Pose

Hi I am doing a transform from the object to the base_link the orientation seems to be right but the positioning is wrong.Here is my code. i had to change the translation values as when i move foward ...
1 vote
42 views

### 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 ...
111 views

### 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 <...
99 views

### 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. ...
258 views

### 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 ...
1 vote
53 views

### 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 ...
2k views

### 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 ...
1 vote
189 views

### 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 ...
1k views

### 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. ...
4 views

### 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
62 views

### 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 ...
34 views

73 views

### 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 ...
60 views

### 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{...
139 views

### 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....
1 vote
154 views

### 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 ...
102 views

### 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 ...
1 vote
145 views

### 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/...
242 views

### 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 ...
200 views

### 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 ...
1 vote
56 views

### 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 ...
1 vote
88 views

### 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 ...
2k views

### 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 ...
153 views

### 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 ...
1 vote
800 views

### 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 ...
1 vote
78 views

### 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 ...
1 vote
110 views

### 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 ...
1 vote
1k views

### 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 ...
747 views

### 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 ...
227 views

### 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 ...
142 views

### 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 ...
1 vote
62 views

### 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 ...
1 vote