Questions tagged [inverse-kinematics]

Inverse kinematics is a subtopic of kinematics dealing with equations that describe the joint parameters necessary to move a robotic arm to a particular position. Also called motion planning.

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How can the inverse kinematics problem be solved?

The forward kinematics of a robot arm can be solved easily. We can represent each joint using Denavit–Hartenberg transformation matrices. For example, if the $i^{th}$ joint is a linear actuator, it ...
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Computing the Jacobian matrix for Inverse Kinematics

When computing the Jacobian matrix for solving an Inverse Kinematic analytically, I read from many places that I could use this formula to create each of the columns of a joint in the Jacobian matrix: ...
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With a 6-axis robot, given end-effector position and range of orientations, how to find optimal joint values

Given a six-axis articulated robot arm holding a tool at its end-effector, if I have a desired tool position and tool orientation, there will be exactly 1 solution to the inverse kinematics equation ...
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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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Solving Inverse Kinematics with Gradient Descent

I am trying to implement my own inverse kinematics solver for a robot arm. My solution is a standard iterative one, where at each step, I compute the Jacobian and the pseudo-inverse Jacobian, then ...
8 votes
1 answer
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Is the geometric inverse problem's solution "continuous" for a redundant robot?

Let's say my redundant robot is at an operationnal position $x$. Is the set of all possible joint configuration "continuous", which would mean that it is possible to explore all the possible ...
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Is there an analytical solution for inverse kinematics of a 6 DOF serial chain?

Let's take a 6 DOF robotic structure. It's consisting of the 3 DOF global structure for the position - and the 3 DOF local structure for the orientation of the endeffector. If the last 3 axis (of the ...
8 votes
2 answers
290 views

Singularity problem at Inverse kinematic solver

I am struggling with this problem for days. I really hope that someone could give me a hint what the problem is. The robot consists of 5 axes. The first axis rotates around the z-axis and other 4 ...
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3 answers
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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 ...
7 votes
3 answers
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Is there a way to determine which degrees of freedom are lost in a robot at a singularity position by looking at the jacobian?

For a 6DoF robot with all revolute joints the Jacobian is given by: $$ \mathbf{J} = \begin{bmatrix} \hat{z_0} \times (\vec{o_6}-\vec{o_0}) & \ldots & \hat{z_5} \times (\vec{o_6}-\vec{o_5})\\ \...
7 votes
2 answers
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Are inverse kinematics and reinforcement learning competitive techniques?

Are inverse kinematics and reinforcement learning techniques contending techniques to solve the same problem viz. movement of robotic manipulators or arm? By a glance through the wikipedia article, ...
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Is there a tool for building and analysing robots (kinematics, control) visually?

I am reading research papers about robotics and many of them follow the same pattern: some construction is established kinematical formulas are read from the mechanical structure the state space is ...
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7 votes
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Decision trees for solving 2D inverse kinematics?

While experimenting with the OpenCV Machine Learning Library, I tried to make an example to learn the inverse kinematics of a 2D, 2 link arm using decision trees. The forward kinematics code looks ...
6 votes
3 answers
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Rotation matrix sign convention confusion.

In rotation matrix, Why do we rotate the first and third rotation in the opposite direction of the 2nd rotation, this is confusing. Image is attached with this. In this image we can note that for x ...
6 votes
1 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 ...
6 votes
2 answers
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Inverse kinematics with joint contraints

I have a manipulator having 4 revolute joints with some movement limitations. So, when I apply inverse kinematics, I'm getting results which are out of limits. Please provide me an algorithm that ...
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Assigning Frames and Deriving Link Parameters

The textbook I'm using doesn't have the answers to the practice questions, so I'm not sure how I'm doing. Are the following DH parameters correct given the frames I assigned? The original question is ...
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How to apply Inverse Kinematics with angle constrained servos?

I want to implement Inverse Kinematics and i understand the inverse jacobian method but the servos i have only have a range from -90 to +90 degrees, how can i implement this detail in the algorithm? I ...
6 votes
6 answers
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Forward and Revers Kinematics For Modified Hanging Plotter

I'm building a modified version of the standard hanging plotter (v-plotter). The basic idea is that you have two cables hanging from stepper motors which form a triangle supporting the pen at the tip. ...
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Forward kinematic and inverse kinematic... When to use what?

I am not quite sure if I quite understand the difference between these two concepts, and why there is a difference between these two concept. Yesterday I was trying to compute the jacobian needed ...
5 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 ...
5 votes
2 answers
328 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 ...
5 votes
3 answers
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is it possible to get all possible solutions of inverse kinematics of a 6 DOF arm?

I would like to know if there is any way to get all the possible solutions of inverse kinematics of a 6 DOF robotic arm? I have found some good Matlab codes but gives only one solution like in Peter ...
5 votes
2 answers
643 views

Humanoid robot arm - inverse kinematics - choose joint solutions

I have developed a 7DOF arm for a humanoid robot (see pic below for more details) I have implemented the IK using a closed form solution and of course I come up with eight solutions - each one is ...
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5 DOF robot - Velocity Inverse Kinematics

I am modelling an articulated robot arm with 5 degrees-of-freedom from igus (igus Robolink). I deduced its direct kinematics equations using Denavit-Hartenberg parameters and homogeneous ...
5 votes
1 answer
331 views

Is this a singularity or incorrect implementation of inverse kinematics?

I at moment trying to compute the Q configuration that moves my robot from it current state described by this transformation matrix. with rotation ...
5 votes
2 answers
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"Smooth" inverse kinematics model for 2-wheeled differential drive robot

I have been reading about kinematic models for nonholonomic mobile robots such as differential wheeled robots. The texts I've found so far all give reasonably decent solutions for the forward ...
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5 answers
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Programming Inverse Kinematics in C++

I want to write my own kinematics library for my project in C++. I do understand that there are a handful of libraries like RL (Robotics Library) and ROS with inverse kinematics solvers. But for my ...
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Help with setting up Inverse Kinematics

I'm working through the Inverse Kinematic example for the Unimation PUMA 560 from Introduction to Robotics by Craig. In it he specifies the IK equations like so: In my software program I have three ...
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2 answers
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Struggling to understand Jacobian Inverse Kinematics

I'm trying to find a method to control a moveo 5dof arm. My goal is to calculate the right angle to turn for each stepper motor to reach a desired point in real environment. I've spent time looking at ...
4 votes
1 answer
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Finding Center of Mass for Humanoid Robot

I've been working on Humanoid Robot, and I face the problem of finding the Center of Mass of the Robot which will help in balancing the biped. Although COM has a very simple definition, I'm unable to ...
4 votes
2 answers
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Inverse Kinematics of Parallel Manipulator (Delta Robot)

Let me start off by saying that I am currently going to university majoring in computer engineering. I love software/hardware and I especially love robotics and I want to apply my knowledge of ...
4 votes
2 answers
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Kinematics of a 4 wheeled differential drive robots

I have a 4 wheeled differential drive robot, like the Pioneer 3-AT. There are only two motors, one for left wheels and one for right wheels. I want to send velocity commands to the robot, I'm using ...
4 votes
5 answers
976 views

Finding inverse kinematics algorithm for a specific manipulator

I need to find a way to solve invrese kinematics for Comau SMART-3 robot. Could you give me a few hints where to start looking? I have no idea about robotics and I couldn't find an algorithm for this ...
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Algebraic and geometric in inverse kinematic

I'm just wondering that is there any case that when algebraic way can't solve the problem while the geometric can ? Cause I'm working on a 2DOF robotics arm This one, I know the length of L1 and L2, ...
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Why with the pseudo-inverse it is possible to invert the Jacobian matrix even in a singular configuration?

Consider the following situation: I have a robotic arm manipulator with all revolute joints, for example consider a 2R planar manipulator. We know that if we compute the direct kinematics of it, anf ...
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1 answer
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inverse kinematics for 6 jointed robots

I am a uncertain about how to compute the right homogeneous transformation matrix to compute an inverse kinematic Q-configuration. Looking at robot like this Where at the end of this robot I have ...
4 votes
2 answers
726 views

Evaluating the similarity of two 7 Degree of Freedom Arms

I am working on the Baxter robot where I have a first arm configuration and a bunch of other arm configurations, where I want to find the closest arm configuration to the first among the many other ...
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2 answers
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Robot arm reachability of a pose in Cartesian space

Given a set of robot joint angles (i.e. 7DoF) $\textbf{q} = [q_1, ... , q_n]$ one can calculate the resulting end-effector pose (denoted as $\textbf{x}_\text{EEF}$), using the foward kinematic map. ...
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How do CAD programs solve for Inverse/Forward Kinematics problem in Assembly?

I am trying to solve for the Forward kinematics of a spatial parallel manipulator. Its loop closure (LC) equations are pretty long, and are being solved using numerical methods. As I am adding more ...
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Is it correct to think of forward kinematics as merely a 'check' for the inverse kinematics?

When the only inputs to your robot are the next x,y,z coordinates of the next point on and on, I can simply just calculate IK to find the angles and make my actuators move to these angles. Whats the ...
4 votes
1 answer
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IK - 3dof - iterative

I want to solve for a 3dof planar arm using gradient descent to approximate end position. Now I am a little confused about the formula and was wondering if someone can help me out. This is my thought ...
4 votes
1 answer
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Implementation of inverse kinematics solution in c++

I am having some issue with implementing a least square solution of the inverse kinematics problem. The q configuration I get are rather large, or makes no sense, so I was hoping someone here could ...
4 votes
3 answers
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Which joints to discretize for IK

I am using ikfast in OpenRave for my inverse kinematics. This is an analytical solver, so if your robot's DOF matches the IK type's DOF, then you get all possible solutions. But if your robot has ...
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How to invert D-H parameters

I currently have a working kinematic chain made by a set of ten links in D-H convention (with usual parameters [ $A_i, D_i, \alpha_i, \theta_i$]). But my task currently requires the inversion of some ...
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inverse kinematics matlab RVC for 3 joint RRR

Hi im having problem with Inverse kinematic using RVC toolbox in matlab for RRR manipulator. ...
4 votes
1 answer
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Inverse kinematic solution with constraints on Rotation for Homogeneous Matrix

I have a 4 degree of freedom robot arm with 3 revolute joints and one prismatic joint as shown in the image: I can give just Target Point position to the Inverse kinematic chain and find a solution ...
4 votes
1 answer
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How to move robotic arm in straight line

So here is my problem. I need to grab an object with my robotic arm, but I don't know the position of the object. The only thing I know is the angle between object and gripper. You will maybe better ...
4 votes
1 answer
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Performing inverse kinematics based on a displacement of the end effector?

I think i have an simple problem, but can't my head around how i should resolve it... My setup looks like this: The grey box on end effector is supposed to be an camera, which measures a dx,dy,dz ...
3 votes
2 answers
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Inverse kinematic orientation problem

I am trying IK for 5-DOF robot all revolute joint. I am working IK with Jacobian inverse i.e end effector velocity = J inverse * error vector. In error vector I am feeding (x,y,z) positional error; ...

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