Questions tagged [manipulator]

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

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11
votes
3answers
565 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 ...
7
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 ...
6
votes
3answers
967 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 ...
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
2answers
687 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 ...
5
votes
3answers
602 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
172 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 ...
4
votes
2answers
204 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
227 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
978 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
187 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
36 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 ...
4
votes
1answer
283 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
810 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
491 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
461 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
147 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
289 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
289 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 ...
2
votes
2answers
200 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
200 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
481 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
713 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
220 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
146 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
38 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
1k 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
260 views

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 ...
2
votes
1answer
43 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
1answer
2k 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
569 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
2k 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
2answers
191 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
839 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
404 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
404 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
557 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
1k 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
513 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
35 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
95 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
568 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
115 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
1answer
29 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 ...