10
votes
Accepted
Why do current manipulators tend to use 7 DoF instead of 6 DoF?
Adding a 7th joint, and still targeting a 6D pose, would result in a
null space of at least one dimension anywhere in the workspace.
That is basically one the reasons people may wish to use a 7-DOF ...
- 443
8
votes
Accepted
Cartesian Velocity Control between Two 3D Poses
You essentially want to find the time derivative of a linear interpolation between two rotations. The easiest way to obtain this would probably to convert the rotation matrix between the two ...
- 941
7
votes
Accepted
Is there a way to determine which degrees of freedom are lost in a robot at a singularity position by looking at the jacobian?
Not by merely looking at Jacobian but by looking at the Singular Value Decomposition of the Jacobian, one can see the degrees of freedom that are lost, if lost. Of course it technically somehow turns ...
- 196
7
votes
Accepted
Why are joint velocities very high near a singularity?
First of all, singularities are not configurations that have the same end-effector position and orientation. Those configurations are inverse kinematic (IK) solutions to that end-effector pose (...
- 1,879
6
votes
Programming Inverse Kinematics in C++
I agree with SteveO that there is nothing wrong with reinventing the wheel if you want to learn about wheels. And for a single application, 4 DoF arm, the IK is probably not too hard.
But I feel ...
Ben♦
- 5,885
6
votes
Inverse kinematics for differential robot knowing linear and angular velocities
Your linear velocity should be the average of both wheel values. Assuming there's some wheel radius of WHEEL_RADIUS, as you've stated, then you should get each ...
- 15.9k
6
votes
Accepted
Why with the pseudo-inverse it is possible to invert the Jacobian matrix even in a singular configuration?
The pseudoinverse gives a “least squared error, minimum-norm” solution: Out of all $\dot{q}$ vectors at your current $q$, the vector
$$\dot{q}_{s} = J^{+}(q)\dot{p}_{\text{in}}$$
satisfies two ...
- 619
5
votes
Accepted
Programming Inverse Kinematics in C++
It is rather straightforward to implement inverse kinematics for a particular manipulator in C++. Of course, you need to begin with the inverse kinematic equations themselves. Putting those into ...
- 4,416
5
votes
Accepted
Does Inverse Kinematics need the current joint angles?
It depends on the method that you use for computing an IK solution. If you have an analytic formula for IK solutions then you do not need the current joint values of the robot. You just plug in the ...
- 1,879
5
votes
How do CAD programs solve for Inverse/Forward Kinematics problem in Assembly?
EDIT: Improved based on the comments below.
If you have a CAD assembled, that means that you have one valid configuration given. You move the TCP (Tool Center Point) only a small amount, since your ...
- 6,682
5
votes
Inverse Kinematics problem formulation (optimization)
The formulation is typical for redundant robots, in which there are an infinite number of joint velocity vectors that could satisfy the $\dot{r}_{t}$ goal. In the version you cite, the $Q$ matrix ...
- 4,416
5
votes
Struggling to understand Jacobian Inverse Kinematics
You will find it helpful to keep the physical robot and the math separate.
The kinematics equations map joint parameters (which are often grouped as a vector $q$) to Cartesian coordinates ($x$,$y$,$z$...
- 4,455
5
votes
Accepted
How do I find the inverse kinematics of a 5-DOF manipulator having the following DH parameters?
A general IK solution is not possible for an arm with less than 6 joints. You can move the gripper to any point (within reach) but you can't completely control the orientation. If you fix the ...
- 1,722
5
votes
Can workspace of a manipulator change after considering its dynamics?
The workspace of a manipulator is strictly determined by its kinematics. Since kinematics only consider the geometry of motion, without regard to forces and torques needed to accomplish tasks, you ...
- 4,416
5
votes
Accepted
Velocity-Control of a manipulator without a dynamic model
Your intuition is partially correct in the sense that you ought to go with position control implemented via velocity commands resorting to a kinematic (not dynamic) model of the manipulator.
This can ...
- 4,020
5
votes
Accepted
Solving inverse kinematics with non-linear optimization libraries
Is it a good idea to solve inverse kinematics with non-linear optimization libraries such as Ceres?
Yes, definitely!
The trend in literature during the last years is to walk away from the traditional ...
- 4,020
5
votes
How to control a 4 wheel mechanum wheel robot with PID?
Let's consider first the task you are wanting to accomplish: following some sort of Cartesian space trajectory. So, you are wanting to make sure your robot is only moving in the x-direction. However, ...
- 904
4
votes
Denavit Hartenberg parameters - 3DOF articulated manipulator
I defined the robot using your (assumed standard) DH parameters:
...
- 1,722
4
votes
Human arm inverse kinematics
You are tackling two non trivial problem at the same time
1. Inverse kinematics of an overactuated manipulator
2. Obstacle avoidance using the null space
By definition of the null-space projection ...
- 1,411
4
votes
Matlab Inverse Kinematics 6 DOF
Ideal solution can be defined in many ways.
The simplest way to choose one is to compare which of the 8 solutions is closest to your current pose in joint space. This is usually a good idea if you ...
- 6,682
4
votes
Self-Motion Manifolds
Saw this question and figured I would throw my two cents in 5 years later.
Gilhad's reasoning about the mathematical process of simple to complex theorems/proofs makes sense as to why the analysis is ...
- 904
4
votes
Accepted
Inverse kinematic orientation problem
Up till now, I am using the Euler angle representation but I have not been successful. After referring to the book "Robotics Modelling, Planning and control" by Bruno Siciliano form Springer ...
- 186
4
votes
How do I find the inverse kinematics of a 5-DOF manipulator having the following DH parameters?
If you say you're are stuck after values for the first two angles, you are probably trying an analytical approach. Try solving for IK using standard techniques Jacobian Pseudo Inverse or Cyclic ...
- 681
4
votes
Controlling the pose of a manipulator using inverse kinematics
As you already have the Jacobian vector, I assume you also solved the inverse kinematics problem. I will refer to the IK problem as $f^{-1}$
In order to get the joint space equivalent of the ...
- 6,682
4
votes
Solving pseudo inverse of Jacobian in Matlab/Octave
After running your code, it looks like everything is behaving how you have defined it to. The problem you are running into has more to do with the Jacobian itself and less to do with any mistakes you ...
- 904
3
votes
Accepted
Dealing with fixed transformations while solving inverse kinematics
Hopefully you still have only 4 rows in your DH matrix, not 8 as you said. I think you mean that your Jacobian matrix has 8 $\require{enclose} \enclose{horizontalstrike}{\text{rows}}$ columns.
...
- 4,416
3
votes
Rotation matrix sign convention confusion.
The real dig to the sign convention is direction and the way humans like to perceive things orderly or at least using a reference. clockwise and anti-clockwise directions only exist with ...
- 131
3
votes
Accepted
Inverse kinematics for a four-legged robot
You do not (only) need inverse kinematics. Inverse kinematics can give you e.g. the angles in your leg joints for a particular leg position, however it does not define a gait type.
For 4 legged ...
- 6,682
3
votes
Help with setting up Inverse Kinematics
If I have correctly understood your question, you have those values (the angles that you want for the pose of the end-effector of the robot) but you don't actually know how to use them, since in the ...
- 131
3
votes
Accepted
Help with setting up Inverse Kinematics
You need to turn each rotation angle (XRot, YRot, ZRot) into their own 3x3 rotation matrix. Once you have three 3x3 rotation matrices, you multiply them all together to get a singular "final" 3x3 ...
- 15.9k
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