Questions tagged [manipulator]

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

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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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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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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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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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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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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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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 ...
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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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How to combine URDF files in pybullet?

I have a URDF file for the Kinova Gen3 robotic arm (6 dof) and a URDF file for a suction end effector that was built for a UR5 arm. I am able to load the file for the arm along with a table and some ...
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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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velocity and acceleration of end effector

assume we have maximum angular velocity and maximum angular velocity for each joint in 6 DOF manipulator. now how can we calculate maximum velocity and acceleration of end effector at any path planing?...
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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 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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Sinusoidal trajectory of each cartesian coordinate for the end effector

Consider a 7-DOF robotic manipulator. I want the end effector to follow a predefined trajectory and suppose I care only about the position and not about the orientation. So, the rotation part of the ...
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How to calculate potential enegy of manipulator dynamics?

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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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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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 ...
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My Pick and Place Program Not Working

hope you are all well. I am trying to finish a capstone project on Coursera. It asks me to carry a cube object from an initial position to goal. This video shows the movement. Project website: http://...
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Robotic Platforms Similar to the PiBot(Locobot)

I am brain storming platforms to use for a project I am working on. I'm looking for an mobile platform with a manipulator attached. I originally was focusing on the PiBot, but after doing some ...
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Multi-Link Robot Degrees of Freedom

I want to compute the DOF of this system if it composed of (n) such links grasping this common object using Grubler's formula obtaining the solution as a function of (n), considering this to be a ...
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Is it possible to control a 5 DOF manipulator in the 6 DOF Task Space?

I am referring to pre-computed torque control techniques that are based on the Task Space dynamic model. Maybe by using pseudo-inverse for the Jacobian and the task space inertia matrix ? Cheers, ...
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How to calculate displacement of the end effector by the yaw, pitch, and roll in the spherical joint?

For planar robots, we can calculate how small changes in the angle of each joint corresponds to the displacement of the end effector, by constructing a jacobian consisting of cross products between ...
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Cartesian Velocity Control between Two 3D Poses

I am really struggling to understand how to do Cartesian velocity control when 3D rotations are involved. So, below is a very simple example which I am hoping somebody can help me with. Let's say the ...
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How do I decide the minimum number of link lengths and joints my manipulator must have from the configuration space?

I have a configuration space in 3D where my manipulator must reach certain points. Taking into account all the factors how do I decide the mininum number of links and joints my arm must have?
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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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Dexterity calculation with dual quaternions

How can the manipulability of a robot arm be calculated when the kinematics are described with screw theory such as dual quaternions? These methods are sigularity-free, but what could we say about ...
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281 views

Inverse Kinematics with Orientations

Let's say I have a robot consisting of a base $B$ and a manipulator $M$. The pose of the manipulator can be expressed as the transformation matrix $T_{BM}$. I also have a goal $G$ which I want to move ...
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Controlling the pose of a manipulator using inverse kinematics

I want to control a robotic manipulator in Cartesian space, using inverse kinematics. I know that I can do this using $\omega=J^{-1}v$, where $\omega$ is a vector of joint velocities, $J$ is the ...
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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 ...
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Cartesian Impedance control Damping Design (Double Diagonalization)

In the literature, it is often seen that for a system: \begin{align} \Lambda \ddot{e} + D_d \dot{e} + K_d e = F_{ext} \end{align} A dynamic damping matrix is required for a robot to take ...
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How do I find the minimum time for computing a trajecotry for a robotic arm?

I am studying robotics and I am focusing on trajectory planning. I have been struggling with this topic for a while, and I still have some doubts that I cannot solve. One of them is the following: I ...
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159 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. ...
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What is the reasoning for solving inverse kinematics problems?

I am a student, and I am studying robotic arm manipulators. I am focusing on the concept of inverse kinematics, I have understood is the process of finding, from the direct kinematics, the joint ...
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Jacobian Derivative (Analytical?)

If I understand this correctly, given the Jacobian Derivative $\dot{J}(q)$ derived using the method presented from the paper by (Rhee, J. Y., & Lee, B., 2017) where the algorithm summarized ...
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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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What is canonical grasp?

What is a canonical grasp and how is it different from normal/other grasp? I've searched through internet and forums but haven't found any answers.
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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 ...
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Understanding Impedance Control

I have a question regarding impedance control for a robotic manipulator. Given that we have a task space trajectory: $\ddot{x}$, $\dot{x}$ and $x$ And the dynamics model of the robot: $$\tau = M(q)\...
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Can workspace of a manipulator change after considering its dynamics?

As per my knowledge, the workspace of a manipulator can be determined if one knows the forward and inverse kinematics. But is it possible that the workspace of the manipulator can change after ...
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Find the kinematic parameters using DH by Craig convention

I am trying to find the kinametic parameters using the J. Craig of the DH parameters for the following 2-DOF robotic manipulator. where $\ x,y $ are the axes of the reference frame and $\ q_1 , q_2 $...
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What does "resolution of a sensor" mean? [closed]

I am studying robotics and I am focusing my attention on the sensors used on robot manipulators. I have seen that there a proprioceptive sensors, such as encoders, and exteroceptive sensors, such as ...
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Why in trajectory planning in joint space the manipulator never crosses a singularity?

I am studying robotics kinematics and I have studied that if we plan a trajectory in joint space it is impossible for the robot manipulator to cross a singularity during its motion, while in cartesian ...
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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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Problem defining rotation matrix

I am studying robotic kinematics , and given the following manipulator with its D-H frames assigned: I have to find the rotation matrix $R_{e}^{2}$, which is the rotation matrix of frame $e$ with ...