Questions tagged [kinematics]
Kinematics is the branch of mechanics dealing with the motion of points and objects.
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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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Adjusting Path Planning Origin in ROS2 Nav2 for a Long Vehicle
I am working with ROS2 Nav2 and the SMAC planner for a long vehicle (a truck), where the planning origin’s traditional placement at the geometric center (base_link) causes some practical issues in ...
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Using KDL to calculate a custom Jacobian for 5 cartesian DOF
I want to calculate the Jacobian of a robot system while I want to restrict the rotational change of the pose to only the unit vector of the relative rotation, which essentially says that I don't ...
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How to Calculate the Correct Orientation (rx, ry, rz) When Rotating a Pose Around an Axis in 3D Space in Python
I created a function to compute the rotated pose around a given rotation axis. Here is my code:
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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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Getting pitch, yaw and roll from Rotation Matrix in DH Parameter
I've calculated a DH Parameter matrix, and I know the top 3x3 matrix is the Rotation matrix. The DH Parameter matrix I'm using is as below, from https://en.wikipedia.org/wiki/Denavit%E2%80
Above is ...
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Question about inverse kinematics for 2 axis gimbal
If I have a 2 axis gimbal (pitch and yaw) and I want to set the camera to a specific inertial orientation (in the world frame), how can I do this? How do I know what to set each motor to achieve this?
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Very high position_tolerance with inverse kinematics
I finally managed to make my manipulator work also with Pose Goal using KDL as Inverse Kinematics plugin.
The problem is that I cannot in any way go below a certain level of position tolerance (0.12) ...
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Mobile Manipulator: Is it possible to use the output state of an MPC position controller instead of the optimized control inputs (acceleration)?
Good day, I hope you are all well :) It's been 7 years since I've last been here haha.
I am currently trying to implement this paper: https://www.mdpi.com/2077-0472/12/3/381
Their mobile manipulator ...
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Force transformation problem
I have the following set-up:
I read force and torque values in sensor frame, but I want to transform the to tool frame. I have the following equation:
where:
This last matrix shoul be 6x6, but if I ...
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How can I find a robot's distance from an object given FOV, bounding box measure, and image width and height in pixels?
The robot is standing in the middle of the arena. I am confused on how to convert the pixels into a real life distance and how to use the bounding box. Starting help is appreciated.
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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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What determines a robots euler rotation order?
I know Fanuc robots use the XYZ rotation order, ABB uses ZYX and some robots use the ZYZ rotation order. What actually determines this order? is it the way the frames are setup on the DH table? Or ...
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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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How do I convert horizontal inward motion to vertical downwards motion
I have a small coil gun project for which I designed a magazine to put my soft iron projectiles, my main concern is to design some sort of magazine mechanism with a safety because the “accelerator” is ...
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What is my last rotation matrix for the last three angles when i have found the first three when doing inverse kinematics to a 6dof robot?
I am doing inverse kinematics for a 6dof robot.
I have used the geometrical method to describe the angles from one to three. I have trouble doing the next part. I know I that I have found the ...
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Derivation regarding spatial velocity
In the rigid body dynamics algorithm book (Featherstone et al.) it claims
We start with a rigid body, $B$, and choose a fixed point, $O$, which can be located anywhere in space. (See Figure 2.1(a).) ...
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DH table for a 4 DOF Scara Robot
Kinda bangin my head here trying to make a DH table for a robot. So I found a 4 DOF Scara robot online and am trying to make a DH table for that robot just with different link lengths.
Would the DH ...
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Probabilistic Robotics by Thurn: Velocity motion model. Detailed derivation for eq. 18
In the book, The equation for finding center of circle is denoted in eq. 5.17, which is as
$$\begin{pmatrix} x^* \\ y^* \end{pmatrix} = \begin{pmatrix} x \\ y\end{pmatrix} + \begin{pmatrix} -\lambda \...
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What is the kinematic model of a quadrotor/quadcoptor with an X configuration?
I would like to know what is the kinematic model of a quadcopter in X-configuration. Basically I want the relation mapping rotor speed to the body twist (or body frame velocity).
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Lynch, Park derivation of the dynamic equations of motion
In Park and Lynch's "Modern Robotics" textbook (Section 8.2.1), they give the following derivation for the velocity and acceleration of a point $p_i$ with respect to a fixed body frame $\{b\}...
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Articulated Kinematics
I'm currently engaged in developing the lattice generator for the state lattice planner in Nav2. The motivation is to integrate articulated vehicles, which are characterized by 4 state variables, as ...
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Transforming between a local and global frame for a Kalman filter
I want to track an object in a global Cartesian frame, denoted $G$. The object has a local frame, denoted $L$. The object is controlled by a velocity command $v$, defined in its local frame. This "...
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Help with clarifying UR10e center of mass
I'm doing an assignment related to the Universal Robot UR10e robot for a robotics class. I have to use the center of mass of each link to solve the problem. I found the information on the link below (...
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IMU frame to body frame
I am thinking about this problem:
My IMU is centered at point O, and my structural body is centered at point p. Points O and P are two points on a rigid body. Point P is always moving and its motion/...
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Inverse kinematics for an unusual system
I'd like to use inverse kinematics for an unusual system. Basically it looks like this: I have a bunch of small objects (let's say A,B,C,D... which can be modeled as points) connected with revolute ...
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What is the preferred approach to derive the kinematics/dynamics of a floating base 3-link robot?
I would like to derive the kinematics and dynamics of a floating planar robot with two leg links and a hip link while the robot is in free-fall (i.e. no ground contact at the "feet"). This ...
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Relationship between Lie Algebra (Murray, Lynch) and spatial vector (Featherstone) approaches
I am curious about the relationship between the Lie algebra/group approach to robot kinematics given by Murray (et al.) in "An Introduction to Mathematical Robotic Manipulation" and Lynch (...
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Screw theory for kinematics/dynamics of mechanisms
Is screw theory commonly used for general kinematics/dynamics of mechanisms (not just robotics)? I'd be interested in anything that covers the types of mechanisms you would find in a typical ...
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Simultaneous dual arm movement
I am attempting to plan and move two arms using moveit2 at the same time. I have setup a move group that contains both arms and am using the c++ move_group_interface to attempt to plan and execute for ...
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End effector velocity control of a 6-DOF robotic manipulator using MPC
I've been trying to utilize Model Predictive Control (MPC) scheme that I have for end-effector position reference $x(t)$ tracking control to build end-effector velocity reference $\dot{x}(t)$ tracking....
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3R Planar robot arm singularity
To find the situation where singularity occurs, the determinant of the Jacobian is used.
For the RRR planar robot with angles $q_1$, $q_2$, and $q_3$ and the length $L_1$, $L_2$, and $L_3$ as shown ...
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How to calculate error for inverse kinematics?
I am implementing inverse kinematics on a robot, and I am confused about how to calculate error from my desired pose to my current estimated pose. Both are orocos-kdl frames that consist of a 3x3 ...
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3-dof Kinematics dh table [closed]
Hello, I have some questions about kinematics. There are three of them:
When we align (z_o) with the z-axis, how should we define the x and y directions? It seems like pointing the right-hand thumb ...
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Issues with cube stacking controller for Panda Robot using Behavior Trees and Task Space Control
I have been working on a controller for a Panda (Franka Emika) robot (simulation, RobotDART and py_trees) and i can't figure out why the gripping mechanism doesn't work correctly. Initially the robot ...
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Adjoint representation of twists in the Jacobian derivation
In section 5.1.1 of Modern Robotics by Park and Lynch (pg. 153 of 1st edition, pg. 177 of updated 1st edition), the following derivation is given for the Jacobian matrix.
I don't understand this ...
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Standard Notation/Name for Velocity Transformations
I've been looking to see if there's any standard notation for a matrix to convert an end-effector velocity vector $\xi_n^0 = \begin{bmatrix} v \\ \omega \end{bmatrix}$ from one frame of reference to ...
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Inclined Slew Joint Kinematics
I have a robot wrist with a non-typical joint configuration that I have been trying to come up with kinematics equations for. Not sure if there is a common name for it but I have not been able turn ...
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How to reduce the turbulence of a robotic arm, when it's end effector touches a surface?
I am working on a project related to tele-robotic ultrasound where I have to tele-operate a virtual UR5 robotic arm with a end-effector(a thin rod) through a haptic device in PyBullet. When I make the ...
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DH Paramater and Kinematic diagram for 2DOF Cobot
Here is my robot model in moveit, I believe the kinematic diagram is not right. Can anyone tell me the correct DH parameter values for this robot model.
As far as I understand the values should be:
<...
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Coordinating long-running actions with independent threads [closed]
Basically, some things have real-world durations that need to be accommodated. For example, moving a servo arm 180° will take a significant number of milliseconds.
What is the best practice for ...
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ROS force vector transformation
In my work, I am using force sensors that provide measurements based on their frame pose in Gazebo. Due to the fact that frames are not constructed based on DH parameters, I need to track the tip's ...
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Instantaneous Center of Rotation of Skid-Steering Mobile Robot
Is there a instantaneous center of rotation (ICR) for 4-wheeled skid steering mobile robot (such as Husky , Pioneer 3-AT) if the center of mass is located at the geometric center of the robot? What if ...
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Constraint Jacobian vs Space Jacobian
In the context of the book "Modern Robotics" of Kevin Lynch, and in the context of closed-chain mechanisms, what's the difference between the constraint Jacobian and the space Jacobian?
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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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Transformation matrix between base and end effector in Staubli
I have a Staubli TX2-140. I want to know if the controller gives the transformation matrix between base link and end effector in the actual robot arm configuration or if I have to calculate it. I ...
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Kinematic model of skid-steering mobile robot (4 wheeled mobile robot)
The kinematic model for skid-steering mobile robot (4 wheeled mobile robot) is
where state vector is $q = (x,y,\theta)$, and $\eta = (v,w)$ is the linear and angular velocity of the robot, and $x_{...
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Is the angular velocity vector the derivative of a time-varying quantity?
On page 111 (section 4.6) of Robot Modeling and Control (Second Edition) by Spong, Hutchinson and Viyasagar, the authors define a "body velocity" vector $\xi$ of the end-effector as follows:
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Calculate joint torques in 3 joint RRR mechanism
I don't know if I could upload these things here, but I want solve the following exercise:.
I undestand that I should use the following formula:
But, I have to solve every joint torque, so how could ...
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Rotation of a point in 3D space
I want to rotate a point (3,4,5) by an angle 45 degrees(0.785398 rad) in 3D space. I have used the standard DCM matrix in the order Rx, Ry and Rz.
Where,
theta = 0.785398,
Rx= ( [ 1, 0, 0]
[ 0, cos(...
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