Questions tagged [kinematics]

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

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Forward kinematics of spherical parallel manipulators with revolute joints

I found an article that can help in my investigations. Forward kinematics of spherical parallel manipulators with revolute joints The problem is solved for the following system of vectors, which is ...
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Finding Jacobian matrix using the DH parameter table and relative transformation matrices

Let's say we have a three revolute joint robot with the following DH parameter table: Where the last row corresponds to the transformation between the last joint frame and the end-effector frame. We ...
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63 views

Modeling of Robots

There are mainly two approaches for controlling robots (mobile robots and static robots): 1) working with kinematic equations, controlling joint or wheel speeds , 2) working with dynamic equations and ...
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Extract Coriolis matrix from Coriolis*q-dot vector multiplication

I have been using matlab to do some robotics simulation. I am able to Create the forward kinematics with transformation matrices Create the jacobian matrix Find joint velocities Create the ...
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Angular velocity in terms of quaternions

Im reading Theory of Applied Robotics, 2nd edition by Jazar, specifically section 7.1, example 207 on page 390. The author is trying to express angular velocity by unit quaternions. Starting from ...
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FlexiTimer giving errors in servo motion

I am working on a quadruped bot, spiderbot and I am trying to make a creep gait using Forward kinematics however, for some reason my code stops working after the execution of the line - ...
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Gyroscope signal when mounted on a deflated tire

Before I do the experiment, I am a bit confused about the expected signals provided by a 3-axis gyroscope (angular velocities vs. time) mounted on the edge of a (slightly) deflated car tire when the ...
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41 views

How do I add a tool to an inverse kinematic solver

This may be a very basic question, however I am having great difficulty to find the right answer. I have a functioning python code for the inverse kinematics of a 6 axis UR Robot. For any ...
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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 ...
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The Jacobian resulted from Screw method is different from analytical one (Example Inside)

I am currently solving a kinematics example that asks for the Jacobian. However, when I solve it using the Screw method I get different results from the analytical method, The example is kinda hard to ...
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26 views

Calculation of error, based on camera images

I am trying to measure the precision error of a gripper that is mounted to the flange of a 6 DOF industrial robot. The gripper-design is rather complex, therefore we would like to make sure it is ...
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About kineto-statics duality of the closed chain

I can't understand the content from the book "Robotics Modelling, Planning and Control", page 151. Suppose that there is a manipulator which has a closed chain. And Let $\textbf{q}_a$ actuated joint ...
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KUKA KR6 R900 sixx (Agilus) robot - Space frame screw axis

how do I find the space (and body) frame screx axis (s1..s6) of this agilus robot?
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Robotic Manipulator 3-RRP v2

I recently asked a question about a 3-RRP manipulator but the only answer didn't work for my robot. I would describe the manipulator as an arm that rotates around the shoulder over the x-y axis, the ...
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136 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 ...
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1answer
26 views

Angular Velocities of CoM in Global Coordinate

The block diagram of the robot is shown as above. Here, $\phi$ is the angle between $X_v$ and $X_0$ (Yaw angle of the robot), and $\psi$ is the angle between $Z_b$ and $Z_v$ (pitch angle of the robot'...
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How does it get a bizarre term in triangle law of vector equation in a paper

I am reading the paper "Motion control of wheeled mobile robots" at page 5, as we have the equation (34.7), i wonder how it contains $− dc(s)\dot s$ in side. As the triangle law of vector: $\vec{OP}=...
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Does Vehicle Yaw angle measures same at every point on it? If not, how to translate yaw rotation to COG of the vehicle from different point?

I am using an IMU to measure the yaw rotation angle of a car. I need to translate the rotation measured to COG of the vehicle. I can ignore roll and pitch as I am driving it on a flat surface. So, ...
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27 views

Constant Offset matrix

I've been reading about controlling systems via momentum wheels. Such as in Satellites, or fancy inverse pendulums. In a particular paper, the writer tries to explain away an offset and settling of ...
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105 views

question about spatial velocity in the book <modern robotics>

I think the equation(3.73) should be: $\dot p-w_s$x$p=\dot p-\dot p=0$ have no idea how it can be wrong and don't know the difference between infinitely large body and a body just include the fix-...
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102 views

Null space of the Jacobian matrix for a robotic arm

I have doubts on how to find all the joint velocities that don't produce any linear velocity, so are in the Null space, when we are in a singular configuration. For example, suppose we have a 2R ...
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68 views

Libraries to calculate kinematics using Screw Theory

Most kinematics libraries/packages use the conventional transformation matrices (DH parameters). However, I'm looking for something that uses Screw Theory principles to set up the Product of ...
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Do I need to use Inverse Kinematics if I have the coordinates of all joints?

So I have the positions of all the joints (x,y,z) of a robot arm. I need to calculate the angles of the joints to feed them to another similar robot arm. I cannot get the angles from the robot I need ...
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Advice for suspension 101 for a small ATV robotic platform [duplicate]

I'm a recent grad from mech. eng. program and going into robotics field. I want to design a suspension for a small ATV robotic platform on 4 wheels that carries max 75 kg load. I might use the wheels ...
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Effective forces on an object for grasping

For example, a robot or a humankind is grasping an object such as a bottle. Which forces are effective on that bottle ? This is my opinion: When we grasp a ...
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All Joint Angle values not converging to desired set point (I am using Roy Featherstone's Spatial Toolbox)

I need the robot joint angles to become the same as given (desired) joint angles. The kinematics and dynamics (used Spatial Toolbox) are correct and the motor models are realistic too. But out of 3 ...
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Forward Kinematics of non-planar robot using Roy Featherstone's Spatial Toolbox

I have a non-floatbase 3 DOF non-planar robot whose forward kinematics I need to compute using Spatial Toolbox. The code for this purpose is p = fbkin(q) but as my ...
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3 DOF robot torque not converging Robotics Toolbox

I have a Simulink model in which desired torque is [0;0;0] and current torque should converge to zeros too. But I am getting oscillatory torque as output. This is the block diagram of what I am ...
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33 views

Joint torque sensor vs end-effector force sensor

I am trying to understand the difference between joint torque sensors, and force sensors, in a robot arm. From what I understand, joint torque sensors estimate the torque at each joint, whereas a ...
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Can Swedish wheels be used in two wheeler configuration?

Can we use any of the Swedish 90°/45° Omni or Mecanum wheels in two wheeler configurations?
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175 views

What are the differences between trajectory planning, trajectory tracking, path planning, path following and motion planning?

What are the differences between trajectory planning, trajectory tracking, path planning, path following and motion planning? And what are the basic methods they use?
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Task Space Control Parameters for 6-Dof Manipulator

I'm developing a Task Space controller based on speed for a Universal Robot 5. I've already calculated the Jacobian, position and rotation error for the classic control method: The method works fine ...
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1answer
85 views

Kinematics with Product-of-Exponentials terminology: not forward, not inverse

I'm working on a kinematic estimation algorithm, and am trying to come up with the right terminology. I'm using the Product-of-Exponentials formulation for kinematic chains (and ignoring position ...
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106 views

Adjusting the PWM frequency and duty cycle to achieve the desired angular velocity in differential drive robots

I am practicing C++ and intro to robotics using a simple differential drive robot and a raspberry pi. Also following along the GA Tech course on control of mobile robotics. The implementation I am ...
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How can Denavit-Hartenberg representation with only 4 variables describe rototranslations with 6 DOF?

I am wondering how the Denavit-Hartenberg representation is able to describe rototranslations with 6 DOF with only 4 parameters? Some context: Denavit-Hartenberg representations can be used to ...
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186 views

Controllability of a car with a single trailer

I'm studying the kinematic model of a car with a single trailer. This picture shows the system: I started from the following statements: With these constraints, I got the Pfaffian form: And then ...
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342 views

Finding correct RPY for approaching a known point on a plane

I have a robot with 6 DOF that I want to use to grab a hanging sheet at a specific point near its edge. The grip needs to be perpendicular to the edge and co-planar with the point of course. I have ...
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How do I calculate the direction robot is facing, pose from velocity and yaw rate?

I have a simple car robot with four wheels moving relatively slowly (5~10 mph). The robot has a velocity magnitude and yaw rate sensor and the sensor samples about every 0.1 seconds. I want to map the ...
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112 views

3D Inverse Kinematics Jacobian Construction

I am following this article: Overview of Jacobian IK From the link, an example says: O is a pose vector which represents the initial orientation of every joint And following this, it gives an ...
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179 views

How to determine the direction of X-Axis in Denavit Hartenberg process? [Sketch inside]

The rules of assigning axes for DH parameters are (as I know them): 1- Z: in the direction of the axis of rotation/translation of revolute/prismatic joints. 2- X: perpendicular to the previous Z axis ...
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83 views

3D Inverse Kinematics Jacobian

I am reading up on inverse kinematics and have a few questions I hope could be answered. This example is from a 3-revolute-joint, where $ E $ is the end effector and $ G $ is the goal position of the ...
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51 views

Add control and planning trajectory to double pendulum [closed]

How do I control a double pendulum to get the end effector link to go in the trajectory shaped in a perfect circle? I have the equation of the circle to go in but I don't know how to get the double ...
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1answer
54 views

Why is the endeffector of a delta-robot on the slant?

A delta-robot is a nice design for a robot, because it allows to separate the motor from the moving parts. As a result, large and heavy motors with 800 Watt can be used and at the same time the ...
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3answers
453 views

Finding Mass/Inertia Matrix of a robot

Hi I am trying to model my humanoid robot. The general EoM is $M(q)\ddot{q}+C(q,\dot{q})+G(q)=U$ I know $M(q)$ is Inertia matrix which depends on joint positions $\textbf{q}$. However, I am having ...
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55 views

Are underactuated robots easier to program?

The first examples for passive dynamics were introduced by Ted McGeer in the early 1990s. The main principle of so called underactuated robotics is, that not all joints in the system can be controlled ...
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underactuated robot problem

Lets say the robot has 4Dof and the operator gives (x,y,z,roll,pitch,yaw ) as control input( rank(J) < dim(task) ). Now the robot is overwhelmed and will probably show some jerky movement. But can ...
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State Space model for bouncing ball

In lecture 5.5 Bouncing ball, slide 26, Coursera's Control of Mobile Robot course, how are the state space equations formed in "Equations of motion in-between bounces"? Why is [0 -g] added? And how ...
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407 views

How do I find the inverse kinematics of a 5-DOF manipulator having the following DH parameters?

alpha = [ -90, 0, 0, 90, 0] a = [ 0, 400, 200, 0, 0] d = [63.5, 0, 0, 90, 100] I am trying to calculate the joint angles but I am stuck ...
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29 views

Maximum value of norm of mass matrix M

How do I compute the maximum values for ||M(q)|| and ||M_dot(q)||, the induced 2-norms, where M(q) is the mass matrix from the standard dynamical model of a robotic manipulator. I have the numerical ...
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33 views

Vertically moving robot

I want to build a 4WD robot that can travel vertically by pushing against opposite rails. The wheels push against the rails and generate friction, the robot moves upwards as the wheels rotate. This is ...