Questions tagged [manipulator]
manipulator is a device used to manipulate materials without direct contact.
156
questions
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Which is model is best for feedback control of robotic manipulators: MIMO or parallel SISO?
I'm currently designing a robotic arm with 6-DOF, and my goal is to be able to give setpoints for 3d position, velocity and orientation ($x,y,z,\dot{x},\dot{y},\dot{z},\theta,\alpha,\gamma$).
I only ...
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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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votes
1
answer
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Can a Jacobian be used to determine required joint angles for end effector velocity/position?
I'm in the early stages of working with a simple robot arm, and learning about the Jacobian and inverse kinematics.
From my understanding, the Jacobian can be used to determine the linear and angular ...
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3
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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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votes
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answer
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Computing inverse kinematic with jacobian matrices for 6 dof manipulator
I'm trying to calculate the inverse kinematic for an 6 dof manipulator.
Task:
A target point $p_{target} = (x,y,z)^T$ and the orientation $o_{target} = (a, b, c)^T$ are given and I want to get the ...
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6
votes
1
answer
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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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votes
2
answers
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Static equilibrium for 7 dof manipulator
I have a 7 dof manipulator (Kuka LBR4+) and would like to calculate the joint torques needed to keep the arm in a static equilibrium. In most books the transposed jacobian is used to map the forces ...
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5
votes
3
answers
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Proportional controller error doesn't approach zero
I'm reading this pdf. The dynamic equation of one arm is provided which is
$$
l \ddot{\theta} + d \dot{\theta} + mgL sin(\theta) = \tau
$$
where
$\theta$ : joint variable.
$\tau$ : joint torque
...
- 2,453
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votes
3
answers
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Computing the Jacobian Matrix -- chain rule?
I am learning about robot kinematics and the Jacobian matrix, and I'm trying to understand how to compute the Jacobian matrix given a kinematic chain, such as a robot arm. I understand the theory ...
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4
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Dynamic torque simulation for a 6 DOF robotic arm
I am working on a 6 DOF robotic arm(industrial manipulator). I have the basic structural specs (dimensions, weights etc) for the links and joints with me.
Basically, I want to simulate both static ...
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2
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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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answer
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What is the difference between the pose of a robot and the configuration of a robot?
Do "configuration" and "pose" means the same thing? If not what is the difference?
5
votes
1
answer
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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:
$$\tau = M(q)\...
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4
votes
2
answers
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Calculating Error of Arm Manipulator
How can we calculate the error position of arm manipulator?
Let's say we have a Transformation Matrix:
$$\begin{bmatrix}
R_{00} & R_{01} & R_{02} & x\\
R_{10} & R_{11} & R_{12} &...
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votes
1
answer
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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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1
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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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4
votes
1
answer
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Anthropomorphic Arm
I developed an anthropomorphic arm (structure in aluminium) with 6 DOF (3 plus spherical wrist) for direct kinematic.
I chose magnetic rotary encoders to measure angles but I am not satisfied, due ...
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3
votes
2
answers
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views
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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1
answer
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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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3
votes
2
answers
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Understanding MoveIt! and OMPL more deeply
I wanted to know the actual mathematics behind the path planners MoveIt! uses for manipulators from OMPL. I tried to look into source codes but couldn't get enough details.
I wish to know:
How cost ...
3
votes
1
answer
548
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Human arm inverse kinematics
Hi I want to implement an human arm robot and a task such as moving a glass between two points using Robotic Toolbox for Matlab by Peter Coorke. I'm a student and I'm a newbie in this kind of things ...
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3
votes
2
answers
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Calculate required motor torque through Harmonic Drive
I have a term project which is controlling a two-link manipulator with harmonic drive installed at each joint.
To control, i used Computed control method to determine the torque needed for each joints ...
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3
votes
1
answer
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Converting from Modified to Standard Denavit Hartenberg
This is probably a noob question.
But as of right now I am having difficulty converting from the Modified DH to a Standard DH parameters for the Franka Emika Panda. I need standard because it allows ...
- 344
2
votes
1
answer
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D(q) Inertia Matrix and the Jacobian Matrix
There is something I need to verify.
Say we have the following RPR robot manipulator.
The DH table
yields 3 rotational matrices:
\begin{equation}
R^0_1, R^0_2, R^0_3
\end{equation}
Using these ...
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2
votes
1
answer
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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 ...
- 2,453
2
votes
2
answers
335
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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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2
votes
2
answers
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Dealing with fixed transformations while solving inverse kinematics
I am trying to solve inverse kinematics (using the Jacobian pseudoinverse method) for a 7 DoF arm, but because of the way the robot is mounted, the base frame does not coincide with the frame of the ...
- 1,096
2
votes
2
answers
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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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2
votes
1
answer
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Integrating Forward Kinematics Map
Let the forward kinematics map be denoted by $\mathcal{F}$ such that
$\mathcal{F}: \theta \in \mathbb{R}^{n} \rightarrow g \in SE3$
Let the minimal representation of $g$ be given by $x \in \mathbb{R}...
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votes
2
answers
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Inverse kinematics: how to specify TCP constraints in an iterative algorithm?
I am trying to write some simple code to perform IK for a 6 DoF redundant robot using the Jacobian pseudo-inverse method. I can solve IK for a desired pose using the iterative method, and I want to ...
- 1,096
2
votes
1
answer
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7DOF inverse kinematics spherical wrist
Is it possible to apply kinematic decoupling for a 7 DOF 7R manipulator with spherical wrist? If it is possible, can anyone suggest a reference on how to apply this approach with a redundant ...
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2
votes
2
answers
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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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votes
1
answer
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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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votes
2
answers
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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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votes
2
answers
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3-RRP manipulator robot
I'm having some issues with a planar manipulator I have to deal with.
The first two moves are rotational and the third one is a prismatic one. The shoulder and elbow move around the X-axis, while the ...
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2
votes
1
answer
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Why do I need impedance control?
I am having a hard time understanding the impedance controller.
I see that it looks at the manipulator as impedance and the environment as admittance. However, it is hard to grasp the concept and ...
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2
votes
1
answer
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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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2
votes
1
answer
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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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votes
2
answers
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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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2
votes
1
answer
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Euler-Lagrange Dynamic model
I'm working on a masters thesis and need to calculate Mass inertia matrix ($M$), Coriolis/Centrifugal matrix ($C$), and the gravity matrix ($G$) in the equation $M\ddot{\theta} + C\theta + G = \tau$ (...
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votes
1
answer
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showing error while using inverse kinematics "ikine" for 4 dof robotic arm
I want to do forward dynamics but before that I got struck in inverse kinematics for 4 dof. My code is given below:
...
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2
votes
2
answers
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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 ...
2
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2
answers
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Inverse Kinematics - How to only find a unique joint angle solution in 4 dof robot?
I have to develop an algorithm to determine the necessary joint angles to achieve a desired TCP position and orientation in a 4 joint manipulator. I have come across a concept called "degeneracies", ...
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votes
1
answer
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Significance of link length ratio in serial manipulator
I am formulating a problem to optimize link lengths of 3R serial manipulator shown below :
I do not assume any explicit relationship between the link lengths, but in one of the papers (http://www....
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2
votes
1
answer
556
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Dynamics of a robot manipulator with a force acting on the end-effector
I have this exercise
The dynamic model is
$B(q)\ddot{q}+S(q,\dot{q})\dot{q}=\tau+\tau_k$
Where $B(q)$ is the inertia matrix, $S(q,\dot{q})\dot{q}$ are the centrifugal and Coriolis terms, $\tau$ is ...
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votes
1
answer
730
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Optimization of link lengths for 3R serial manipulator
I am trying to formulate an optimization problem for determining link lengths of 3R manipulator shown in picture below,
Following are the constraints,
Robot arm should be reachable at point x = 100, ...
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votes
1
answer
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Symbolic Representaion of Links and Joints: How to sketch complex manipulators using simple symbols?
In some papers and books we can see that authors using symbols to represent robot arms. My question is, is there a convention for such sketches? If so could you provide a reference which shows how ...
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votes
3
answers
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How to decide links length of manipulator?
I'm working on pick and place robotic arm with 4 dof. I'm using MATLAB for inverse kinematics. But, I want to know how to decide links length. Say, I have four point in space upto where my robotic arm ...
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2
votes
0
answers
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 ...
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2
votes
0
answers
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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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