Questions tagged [manipulator]

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

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11
votes
3answers
531 views

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 ...
9
votes
4answers
2k views

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 ...
6
votes
1answer
8k views

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 ...
6
votes
1answer
4k views

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 ...
5
votes
3answers
571 views

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 ...
5
votes
3answers
1k views

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 ...
5
votes
1answer
109 views

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 ...
5
votes
4answers
3k views

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 ...
5
votes
2answers
636 views

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 ...
4
votes
2answers
129 views

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 ...
4
votes
2answers
143 views

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} &...
4
votes
1answer
882 views

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/...
4
votes
1answer
160 views

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)\...
4
votes
1answer
276 views

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 ...
3
votes
2answers
667 views

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
1answer
471 views

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 ...
3
votes
1answer
280 views

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 ...
2
votes
1answer
2k views

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 ...
2
votes
2answers
98 views

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 ...
2
votes
2answers
269 views

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 ...
2
votes
2answers
161 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 ...
2
votes
1answer
192 views

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}...
2
votes
2answers
445 views

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 ...
2
votes
1answer
86 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. ...
2
votes
1answer
33 views

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} ...
2
votes
2answers
715 views

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 ...
2
votes
1answer
697 views

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 ...
2
votes
2answers
214 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 ...
2
votes
1answer
1k views

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?
2
votes
1answer
531 views

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 $M\ddot{\theta} + C\theta + G = \tau$ (...
2
votes
1answer
1k views

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: ...
2
votes
2answers
1k views

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 ...
2
votes
1answer
39 views

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?
2
votes
2answers
162 views

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 ...
2
votes
2answers
560 views

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", ...
2
votes
1answer
374 views

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....
2
votes
1answer
362 views

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 ...
2
votes
1answer
479 views

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, ...
2
votes
1answer
899 views

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 ...
2
votes
3answers
3k views

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 ...
2
votes
0answers
426 views

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 ...
1
vote
2answers
34 views

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 ...
1
vote
1answer
83 views

How can serial manipulator have unique condition number for given end effector position?

I am reading about Condition Number which is considered as measure of manipulability of robotic arm, it is defined as $$ k = \parallel J \parallel \parallel J^{-1} \parallel $$ Where, $$ \parallel J \...
1
vote
2answers
505 views

Validation of dh parameters

I am working on a concept of robotic arm for which I have fixed DH frames and parameters. Is there any way to validate the correctness of DH parameters and frames ?
1
vote
1answer
26 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
1answer
49 views

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://...
1
vote
2answers
1k views

How to check reachability of manipulator to a point?

I have written a MATLAB code for inverse kinematics of 3R robotic arm, which returns value of joint angles for given link lengths and end effector position and orientation. But if location of point is ...
1
vote
2answers
2k views

Calculating the singular configuration of a 3 revolute joint manipulator

I would really appreciate it if somebody could help me calculate the singular configuration of this simple manipulator I am confused since J is a 2x3 matrix and I cannot simply calculate the ...
1
vote
2answers
872 views

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. ...
1
vote
1answer
77 views

Robot Graphical Representation in Real Time

I'm working with a robot intended to be placed in a tele-echography environment. To control the robot I'm using a 6D space mouse that control each degree of freedom of the robot. However, since the ...