# Tag Info

Accepted

### Why is Screw Theory used in Robotics when you can do everything with regular kinematics?

Screw theory greatly simplifies the notation and expressions used. This allows for complex systems to be considered. As an added bonus it completely eliminates the need to specify which coordinate ...
• 333

### Relationship between the velocity twist Jacobian and the spatial velocity Jacobian

There are a lot of definitional problems and inconsistencies in this area. Geometric Jacobian. I'm not sure this has a precise and agreed upon meaning. But across the more classical robotics books (...
• 1,642
Accepted

• 2,764

### Velocity description in Screw Motion Theory

The body velocity $V_{b}$ is the velocity of the frame with respect to the world, as seen from the frame's perspective. Its rotational component $\omega_{b}$ contains the rotation rates around the ...
• 619

### Stationary/inertial reference frame

Due to the way that frames are defined in the Modern Robotics book (and in this type of vector-field mechanics in general, such as those of Featherstone), both the spatial frame and the body frames ...
Accepted

### Libraries to calculate kinematics using Screw Theory

Lynch and Park's Modern Robotics book uses the product of exponentials formula and screw axes to describe manipulators, and they have a well-documented library available in Python, MATLAB, and ...
Accepted

### Different methods to determine DOF: Chebychev-Kutzbach-Grubler method vs. Screw method

I will try not to skip too many steps. Assuming a Global coordinate frame at the base and the arm is fully extended along the Y-axis of the base frame. Since SCARA has four joints, we will create ...
• 103
Accepted

### Screw based Jacobian

Adding to Peter Corke's answer, there's also a Coursera course by Kevin Lynch which uses the Modern Robotics book as a reference and explains how to derive the screw based Jacobian. The Jacobian can ...

### Free-floating sphere dynamics using Roy Featherstone's spatial_v2 toolbox

You still haven't posted the (full) code that gives the results you've presented; when I run your snippet I don't the results you posted. Instead, I get: ...
• 15.7k

### The Jacobian resulted from Screw method is different from analytical one (Example Inside)

There are in fact two types of Jacobians, a geometric Jacobian and an analytical Jacobian. The intro to chapter 3 in the book: Robotics: Modelling, Planning and Control by Bruno Siciliano, Lorenzo ...
• 5,780

### Newton-Euler Inverse Dynamics by Screw

maybe need some transformation from centers of mass to the joint frame? Isn't that what $A_i$ is? I don't have the book with me, but from your excerpt: Let $A_i$ be the screw axis of joint $i$ ...
• 15.7k

### Forward kinematics confusing point

The author of the referenced thesis is using exponential coordinates and screw theory via the Product of Exponentials formulation to generate the sequence of transformations from one link to the next. ...

### In which frame this wrench is expressed?

Edited Answer From the question, it seems the loading is applied at the end effector but its line of action along the $x_s$ direction. I do prefer to resolve everything on the world inertial frame ...
• 333

### Why is Screw Theory used in Robotics when you can do everything with regular kinematics?

Why use polar or spherical coordinates when you can use Cartesian coordinates for everything? Why use Laplace transforms to solve differential equations? I think most of the challenge in higher math ...
• 15.7k
1 vote
Accepted

### 3D Rigid Body Pose Optimization in flat euclidean space

See https://www.cis.upenn.edu/~cjtaylor/PUBLICATIONS/pdfs/TaylorTR94b.pdf. You can absolutely use "flat" Euclidean space based optimizers while also optimizing on the manifold, but I agree ...
• 449
1 vote
Accepted

### what is difference between twist and classcial velocity

In these equations from Modern Robotics (by Park and Lynch), the fixed inertial frame ${b}$ is both the reference frame used to define all of the coordinate vectors and has its origin located at the ...
1 vote

### Difference between Denavit-Hartenberg and Rodrigues formulas/conventions

The DH method requires you to carefully specify local frames attached to each link and calculate linear and angular offsets between those frames in a very specific way in order to reduce the effective ...

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