Questions tagged [kinematics]

Kinematics is the branch of mechanics dealing with the motion of points and objects.

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28 views

Trajectory following of 3-wheel omnidirectional robot

I created a three-wheeled omnidirectional robot on omni-wheels, there is also a program in which I can plot a trajectory when plotting a trajectory, such data are obtained (X, Y, Tangent X, Tangent Y, ...
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What does RR stand for in RR-manipulator?

I have memorized RR-manipulator as having 2 arms from Google images but "arm" isn't spelled with "R". I also noticed that RRR-manipulator has 3 links. Does R stand for revolute?
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How to calculate DH parameters for Higher Pair?

I am trying to build a robot which is having Bevel Gears connecting two links. I want to calculate DH parameters, but i am stuck with this bevel gear as when the joint rotates both angle and ...
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39 views

Drive unicycle kinematics equations through the geometry

The unicycle dynamics in discrete-time is given by: $$ \begin{array}{l} {x_{k + 1}} = {x_k} + \Delta {s_{k + 1}} \times \cos ({\theta _{k + 1}})\\ {x_{k + 1}} = {x_k} + \Delta {s_{k + 1}} \times \sin (...
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How to correctly determine the θi Denavit-Hartenberg parameter for a SCARA manipulator?

I am using Tsai's Robot Analysis (The Mechanics of Serial and Parallel Manipulators) and I am working on deriving the homogeneous transformation matrices for the SCARA robot with the assigned frames ...
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IK Jacobian is always a singular matrix

I am trying to solve an inverse kinematics equation for 6DOF system, 3 rotation and 3 prismatic joints. I am trying to solve using perturbation method, by adjusting each joint and calculating the ...
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39 views

Joint space trajectory script unclear

I have a script provided by The MathWorks Inc. that makes a robot end-effector follow both a task space and a joint space trajectory through several waypoints. These trajectories are then plotted in ...
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72 views

4 Axis Gimbal Nodal Robot DH Parameters

I'm working on a robot gimbal where there are 4 revolute joints (4th axis for gimbal lock, reducing inertia etc). The robot is nodal such that all axes have the same nodal point and rotating any axes ...
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can anyone explain detailly this video(title: sensorless active complaince)

https://www.youtube.com/watch?v=g8Je93soOZE i am interseted in how they achieve compilance and detect collision in servo without the use of sensors. so any one please explain briefly
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Confusion over configuration space, workspace and task space

I have been watching Kevin Lynch's videos on Coursera in this series on the basics of robotics. From that I gathered these are the definitions. configuration space is the space of all configurations ...
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If a point in a sphere can be given by longitude and latitude, why isn't a torus (also representing 2 dimensions) its configuration space?

In Modern Robotics by Kevin Lynch et al, there is mention of the difference between topology and sample representation as shown by the figure below. I am curious as to why the topology of a point is a ...
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Multiple Rotations via Matrix Multiplication

so I am having an issue understanding why you right multiply for current frame rotation vs left multiply for fixed frame. Let us say you want to: Rotate about x, then Rotate about current y, then ...
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How do you end up with 1 degree of freedom with one big link connecting 3 other links?

I was reading Modern Robotics by Kevin Lynch et al. and this robot was presented. They had introduced Grubler's formula which assumes independent joint which gives $dof = 0$ but this is not the case ...
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Can 2 spaces with different dimensions be topologically equivalent?

I am a bit confused with topology and am reading the next section after configuration spaces. I bumped into the question and got really confused.
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Is the translational vector (positon) in transformation matrices in cm or another unit (MATLAB)?

My transformation matrix gives me, for example, x = 0.06, y = 0.27 and z = -0.04 It does not make a lot of sense to me if this is in cm.
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Orientation Problem of a 4-DOF manipulator

As shown in figure, I have a 4-DOF manipulator. I want to control the robot such that the end-effector should always be pointing down no matter where the robot is in the end space. For the ...
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Finding torque equation for my robotic arm

I am designing a 5 dof robotic arm, and for that I would like to find a torque equation. However, I am a little confused here: According to me the torque equation for M1 should be l2m2+l3m3+l4m4+l5m5 (...
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How can I input joint angles to transformation matrix to get position in matlab?

I am trying to get the forward kinematics for a robot model in matlab (rigid body tree). I created a 4 x4 transformation matrix from the base to the end-effector using the gettransform() function. I ...
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Robotic Tasks in relation with components

I will try to ask the best i can: Our Human Body has parts like arms, legs, head etc. An arm can rotate 360 degrees. Arm has a hand with five fingers which can grip, poke, push etc. How would we ...
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how to find the kinematic and dynamic model of the mechanism

enter image description here 5 links 4 revolute joints find the kinematic and dynamic model ,link 3 should be horizontal with ground and one end of link 1 and 5 there are sliders enter image ...
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61 views

Calculating wheel linear velocity from body velocity

A frame {b} is attached to the centre of a robot chassis. The planar configuration is given by $(x,y,\phi)$ where $\phi$ is the angle between the x axis in {b} and the x axis of a fixed reference ...
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66 views

Omnidirectional Movement for 3 Wheeled Spherical Omni wheel robot

I was watching James Bruton's video on his spherical omniwheeled robot and he was explaining how to go directly sideways. He explains this from 6:09 to 7:06. I didn't understand how the velocity of ...
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Looking for a course (online?) RE: systems with XY stages

Using XY stages is common in many fields: 3D printing Genetics instruments semiconductor lithography automated microscope slide imaging See for example https://www.asml.com/en/technology/lithography-...
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inverse kinematics robot RRR

I realized an analisis of inverse Kinematics but I couldnt solver the equations that I find. the robot is RRR I believe that this problem have solution however I didnt find in the web :( if somebody ...
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velocity and acceleration of end effector

assume we have maximum angular velocity and maximum angular velocity for each joint in 6 DOF manipulator. now how can we calculate maximum velocity and acceleration of end effector at any path planing?...
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6DOF kinematic robotic arm programm

I am trying to find a well documented library which I can use for my 6dof robotic arm (https://www.thingiverse.com/thing:1693444) But I cant find anything :( Does anyone have a python/c code for ...
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120 views

6DOF Kinematics moveo

I asked on stackoverflow for the DH-Parameter for my robotic arm (moveo bcn3d). I also copied the arduino code of Skyentific (YouTuber). Modified it to match my settings but i still does not work. Can ...
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51 views

Range of a heading angle [0,2π) or [−π,π)

Consider the unicycle dynamics in 2D plane: $$\begin{array}{l} \dot x = v\cos \varphi \\ \dot y = v\sin \varphi \\ \dot \varphi = \omega \end{array}$$ What is the range of the heading angle $\phi$? ...
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69 views

Calculate Torques & Forces From Jacobian Matrix

Dear Robotics Stack Exchange, I am trying to calculate the torques and forces for a 2DOF robot. I’m used the partial differentiation method to find the Jacobian matrix. I managed to find the ...
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35 views

How to find Joint Angles or Theta for 7DoF Robotic Arm

I am trying to find the joint angles or at least theta to be used to find the Denavit-Hartenberg Parameter for a robotic arm (Baxter's right arm). I have the link lengths and such, but I don't know ...
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Deduce all possible configuration for a given CONF param FANUC

I am working on the "CONF" parameter of FANUC Robots. The "CONF" param determine the pose of the robot (maybe to have only one inverse kinematics solution). This configuration is ...
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53 views

Parallel spatial mechanism - DOF

The parallel mechanism is composed of a moving platform and a base (or frame) connected by four legs. Each leg is composed of five revolute joints numbered 1, 2, … 5 from the base to the moving ...
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38 views

Elegant way to mathematically relate joint positions (without a root/base joint) for easy re-rooting?

I'm pretty new to robotics, but have learned about the tranformation matrices and how to relate relationships between joints using transformation matrices. I just wonder if there is a system that ...
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105 views

How to find angular velocity using pure pursuit algorithm?

I have implemented the pure pursuit algorithm for my differential wheeled robot as described in the following paper: http://www.enseignement.polytechnique.fr/profs/informatique/Eric.Goubault/MRIS/...
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Forward kinematics confusing point

I am studying robot arm kinematics. In order to construct a transformation from a global coordinate frame to the end effector frame, I have seen references to the Denavit–Hartenberg (DH) convention. ...
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43 views

Can a 6 DOF robot have multiple inverse kinematics solution with a constrained rotation/orientation

I trying to understand how manipulators robot works (6 DOF) I would like to know if the inverse kinematics (IK) solution give only one or multiple solution if we include the rotation (3x3 matrix) of ...
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Difference between Denavit-Hartenberg and Rodrigues formulas/conventions

I am trying to compute the forward kinematics for a 6 DOF robot arm. I've found two methods : the Denavit-Hartenberg (original and modified) and the product of exponentials with the Rodrigues formula. ...
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56 views

What type of electric motor and speed-controlled circuit do I use to bounce a hanging, 5 pound weight? (it's for a Halloween decoration)

I'm trying to make a roughly 5 pound, hanging halloween decoration bounce on a string from about 1-3 times per second, preferably at variable speeds if I can. I've looked up a simple DC motor circuit ...
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How to Calculate Individual Axis Commands Out of 5 Axes G-Code?

I am dealing with 5 axis CNC machining time prediction. I would like to ask the question with providing some background and mentioning the constraints which what I concluded from some of the ...
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Ground based path generation from RGBD camera

How does one generate a trajectory for a ground vehicle using an RGBD camera? For a drone it's simpler since you're not constrained by having to move on the ground but it's not clear to me how ...
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1answer
62 views

Inertial frame's angular velocity expression

I'm following a robotics course on coursera which talks about aerial robotics and more specifically quadrotors. I'm trying to understand the logic behind the relationship between the angular velocity ...
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95 views

Inertial frame VS Body-fixed frame momentum correction factor

I've recently enrolled in a Coursera aerial robotics course and i'm trying to understand how the rate of change of the angular momentum is computed from the inertia frame to the body-fixed frame. ...
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87 views

Path curvature in kinematic bicycle model

I'm trying to develop an understanding of the control law for longitudinal and lateral control for self driving cars. While doing so, I came across the kinematic bicycle model which is used to derive ...
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What is the mathematical relation between phi1, phi2, phi3 and motor PWM values for 3 wheel omni drive robot?

My question is that I cannot deduce the relation between phi1, phi2, phi3 values of the omni robot (3 wheeled) and the motor's PWM values, since I'm planning on designing the robot to perform "go ...
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134 views

Simple inverse Kinematic algorithm

I was looking for a simple inverse Kinematic algorithm that doesn't depend on eigen(doesn't work on my machine + dependency conflict never fixed it) Most of the code out in the internet is way to ...
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1answer
105 views

5 bar linkage hand exoskeleton

I have a project to design a hand exoskeleton for hand rehabilitation. The problem is that i'm thinked I only need the linkage mechanism with multiple 4 bar linkages. But because of human fingers ...
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Stationary/inertial reference frame

In Modern Robotics by Kevin Lynch, there is a term "stationary" frame, but this is never defined. Googling shows that this is synonymous with inertial frame. Apparently inertial frame means ...
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How do I calculate components of an angular rate on end effector frame?

I’ve helped develop the forward kinematic chain for a two-axis gimbal. The Denavit-Hartenberg parameter table for the kinematic chain is given below. $\theta$ $\alpha$ $r$ $d$ $90^{\circ}$ $90^{\...
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236 views

Denavit-hartenberg parameters sign 6-DOF

Trying to understand how does the Denavit-Hartenberg work. While I understood how is the table constructed, I however don't understand how are the signs for the orientation parameters (theta, joint ...
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184 views

how to find Singularity and jacobian Inverseof 5 DOF Robotic arm?

I am working on calculating the Jacobian Determinant to find the singularity of my 5 DOF Robotic arm, I have calculated the jacobian matrix, and the matrix I got is a very large value As it is non ...

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