Questions tagged [kinematics]
Kinematics is the branch of mechanics dealing with the motion of points and objects.
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questions
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Problem with Inverse Kinematics Solver (Jacobian Inverse Method)
I am trying to create an inverse kinematics solver for my 4-dof (all revolute joints) robot using the inverse Jacobian Method. However, it does not seem to be working as the distance between target ...
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Defining the specifications required by a 6DOF robot to impose a harmonic sinusoidal motion
Perhaps a bit of a simple question, but since I don't have a background in robotics/engineering, then I imagine this would be the perfect place to ask such a question.
I am buying a 6-DOF Stewart ...
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1answer
35 views
GPS + IMU data and kinematics equations
I have the following data
Longitudinal acceleration, $a_x^{IMU}$
Lateral acceleration, $a_y^{IMU}$
Vertical acceleration, $a_z^{IMU}$
Yaw angle, $\psi$
Yaw rate, $\dot{\psi}$
Latitude, $\rightarrow ...
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1answer
41 views
Equations of motion with mass attached to end effector and external force
I have to find the equations of motion for the given manipulator:
The links of the manipulator are considered weightless and the equations of motion have to be derived by using the Lagrange equations....
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1answer
28 views
Kinematic Bicycle Model theta units
I don't understand the $\theta$ units. The bicycle model defines $\theta$ as:
$$\theta=\theta +\frac{v\cdot\tan\delta}{L}\cdot$$
Where $v$ is the vehicle velocity, $L$ is the wheelbase distance, and $\...
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2answers
56 views
control of a rod attached to a motor
I have a 76 cm, aluminum rod, attached to the shaft of a 12v DC banebot motor. The rod is hanging vertically initially, and rotates in the vertical plane. The task is to control the rod to make it ...
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36 views
Robot differential drive wheel speed
I would like to build a small robot. The robot will have 4 independent motors, one for each wheel. It will have a rear axle fixed and the front axle will be freely pivoting around its center, somewhat ...
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17 views
Trajectory optimal for quadcopter
I have defined a quadcopter that I control with a PID controller. The dynamics that define it are such.
$T=mg+m\ddot{z}$
$\theta=\frac{\ddot{x}}{-9.82}$
$\phi=\frac{\ddot{y}}{9.82}$
As you can see I ...
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1answer
44 views
Holonomic constraints on an upright wheel
A wheel moving in free space has the six degrees of freedom of a rigid body. If we constrain it to be upright on a plane and to roll without slipping, how many holonomic and nonholonomic constraints ...
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In MuJoCo why do some XML files have objects fall to the ground while others are just fixed above the ground?
Why do some models, or objects in a MuJoCo XML script fall to the floor while others don't?
In the models files that come with the MuJoCo zip, the robot arm (arm26) does not fall to the ground while ...
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2answers
60 views
Confusion about Gimbal lock
I am trying to understand exactly what is happening when Gimbal lock occurs. I have read many explanations now which provide the high-level idea, in that Gimbal lock occurs when two axes are aligned ...
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1answer
35 views
Forward Kinematics for articulated manipulator not giving right answer
I calculated the forward kinematics for an articulated manipulator robot in ROS, but I am not getting the right answer. Here is the diagram for the robot configuration I used-
When Q1,Q2,and Q3 are ...
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35 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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1answer
32 views
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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1answer
32 views
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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1answer
50 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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80 views
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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37 views
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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56 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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1answer
86 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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1answer
50 views
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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1answer
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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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1answer
28 views
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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1answer
71 views
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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1answer
42 views
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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1answer
29 views
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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2answers
24 views
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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2answers
124 views
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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0answers
49 views
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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1answer
90 views
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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1answer
16 views
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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31 views
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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1answer
72 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 ...
2
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1answer
87 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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22 views
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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47 views
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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74 views
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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99 views
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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1answer
164 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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1answer
56 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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1answer
133 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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1answer
42 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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0answers
97 views
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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1answer
54 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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1answer
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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 ...
3
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1answer
154 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/...
3
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1answer
67 views
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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1answer
58 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 ...
3
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1answer
55 views
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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1answer
60 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 ...
