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Questions tagged [dynamics]

Dynamics is a branch of applied mathematics (specifically classical mechanics) concerned with the study of forces and torques and their effect on motion, as opposed to kinematics, which studies the motion of objects without reference to its causes.

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Gazebo does not calculate dynamics when joint_trajectory_controller with position command_interface is used

I was wondering why Gazebo does not calculate dynamics (velocity, acceleration, effort) when JointTrajectoryController is used with ...
Jakub Ivan's user avatar
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Designing the kinematics and Dynamics of a spherical joint as 3 revolute Joint

I am working on a project where I am trying to mimic human like motion and for that I am designing a 7 DOF arm with the spherical joint in shoulder as 3R joints and 2R joints for elbow and 2R joint ...
Anshul Nayak's user avatar
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How does joint torque varies wrt joint velocities in Recursive Newton Euler algorithm?

I'm currently working on solving the inverse dynamics of a 6-axis articulated robot, similar to the UR5, using the recursive Newton-Euler algorithm. I'm very confused with the results I'm getting, as ...
Vishaal's user avatar
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Issues with Torque Distribution in State-dependent Differential Riccati Equation (SDRE) Controller for 4W SSMR Trajectory Tracking

I am currently working on implementing a State-dependent Differential Riccati Equation Controller (SDRE) to track the trajectory of a 4-wheel skid steer mobile robot (SSMR), where torque serves as the ...
MUHAMMAD SAQIB's user avatar
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Hexacopter Simulation

I am doing a project to simulate a hexacopter with the mathematical model and its dynamics with PID. I've got the theoretical knowledge but am stuck on simulation. Would any of you happen to have any ...
DragonSlayer's user avatar
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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 (...
ElbCox3's user avatar
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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\}...
Molecular Lionel's user avatar
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Robot model explodes in Gazebo

I am currently working on developing a model of a robot that moves in space (gravity=0) in the Gazebo simulator. The robot is based on a body with one continuous joint and two revolute joints. Jount1 ...
Yuki's user avatar
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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 ...
Molecular Lionel's user avatar
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35 views

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 ...
Molecular Lionel's user avatar
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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 (...
Molecular Lionel's user avatar
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What are the gain and bias parameters used to control actuators?

When I read the Mujoco official document, the following paragraph raises my confusion: Different settings of the gain and bias parameters can be used to model direct force control as well as position ...
KKKmelody's user avatar
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Controlling motion of single link

This seems like it should have been a well studied problem, but I can't find any solution. We want to define what a motor must be commanded to do to move a single link with mass $m$ and length $l$ $...
guero64's user avatar
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Understanding Virtual Velocities in Delta Robot Dynamics Modeling

I want to model the dynamics of a delta robot, and I came across this article. It utilizes the Newton-Euler method with virtual work to derive the equations. There's a section called Simulation ...
Ali Ent's user avatar
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Rolling friction of a swedish type omni wheel dependent on the direction of movement

I'm trying to find, as well as derive, the equation for rolling friction of a swedish type omni wheel (not mecanum) that depends on the angle at which the wheel is oriented to the direction of ...
Radar32's user avatar
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How do you get the force acting from the first robot link on the second robot link knowing the forces and moments in the base of the robot?

Inverse dynamics (ID) is the concern of finding the required joint forces from a specification of the joint positions, velocities, and accelerations. In the figure bloew, the ID problem would be the ...
deralbert's user avatar
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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 ...
RaMathuzen's user avatar
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Dynamic model of a robotic arm

I have a question regarding the dynamic model of a robotic manipulator. It is commonly written as follows: $$ \tau = M(q)\ddot{q} + C(q,\dot{q})\dot{q} + G(q) + J^\intercal F_{ext} $$ From what I have ...
fi-xgamex do's user avatar
1 vote
1 answer
138 views

Gazebo joint velocities do not agree with joint displacement

In a simulation that I am running, which is described below, the angular velocities that I get from the joint_states topic, do not give me the angular displacement I calculate from the joints angular ...
MIKE PAPADAKIS's user avatar
2 votes
2 answers
178 views

kinetic and potential energy of 3 DOF robot having 2 cylindrical links

Assume two uniform cylindrical links robot has 3 DOF as shown in the figure. Where link one has 1 dof that is rotation on its main axis. The second link has 2 DOF yaw and pitch movements. I can ...
DANAISH's user avatar
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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: ...
Molecular Lionel's user avatar
1 vote
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100 views

PD control with gravity compensation

Given the robot dynamics of the form $$M(\theta)\ddot{\theta}+C(\theta, \dot{\theta})\dot{\theta}+G(\theta)=u$$ where the notations have the standard meaning ($M$ is the inertia matrix, $C$ is ...
The Limit Does Not Exist's user avatar
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How to compute the force applied to point P given the torque registered by the sensor?

I have the following set up: I want to understand how to compute the force that is being applied to the F_knife point given the Force/Torque registered by the sensor at T_Sensor. The position vector ...
cambel's user avatar
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Define system forward dynamics with sympy

I would like to model the dynamics of a robot via the usual discretized system of equations $$ x_{k+1} = f(x_k, u_k) \qquad x\in\mathbb{R}^{n_x}, \quad f:\mathbb{R}^{n_x}\times\mathbb{R}^{n_u} \to \...
SystemSigma_'s user avatar
3 votes
1 answer
613 views

Calculation of IMU offset for Placement of Inertial measurement unit away from centre of mass

I am working on a 6DOF IMU that contains a 3-axis accelerometer and a 3-axis gyroscope. I am building a project to plot the position and orientation of a vehicle/dirt bike in a 3d plane. However, the ...
Akash Sagar's user avatar
1 vote
1 answer
1k views

Center of gravity offset for accelerometer and gyroscope readings

I am working on a 6DOF IMU that contains a 3 Axis Accelerometer and a 3 Axis Gyroscope. I am building a project to plot the position and orientation of the turret/cabin in a crane in 3D space. The IMU ...
Akash Sagar's user avatar
1 vote
1 answer
107 views

Determine the maximum joint velocities for a PTP-Movement

Assuming an industrial robot performs a PTP movement with a speed of 100% for each joint, it often happens that the joints never reach 100% of speed because the torque limits of the actuators are ...
Afrobeta's user avatar
1 vote
2 answers
222 views

Estimating angular velocity from position

If you have two position estimates $P_{t_1}$ and $P_{t_2}$ and times $t_1$ and $t_2$ how do you extract the average angular velocity from them? The linear velocity is a simple difference but how do ...
FourierFlux's user avatar
3 votes
1 answer
95 views

Articulated Body Algorithm with gear ratio

I am reading up on the proposed articulated body algorithm by Featherstone, which goes like: Pass 1: \begin{equation} \nu_0 = 0\\ \nu_i = {^i}X_{\lambda(i)}\nu_{\lambda(i)}+s_i\dot{q}_i\\ c_i = \nu_i \...
Josef's user avatar
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2 votes
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In Dynamic Motion Primitives, why we need to approximate f if f_target is given?

I seem to misunderstand something crucial regarding finding the force vector in the process of DMPs: The way I understand it, I should come up with a dataset of trajectories $\{y_i\}_{i=1}^n$, and ...
Hadar's user avatar
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2 votes
1 answer
311 views

Finding error in euler angle from quaternion

I'm currently working on creating a ROS controller package for franka arm, which I choose to implement a feedback linearization controller that works as following: Assume we have a planned trajectory $...
Heming Huang's user avatar
1 vote
1 answer
41 views

what does free or forced torque mean in robot arm dynamics?

I'm trying to understand the dynamics (torque , velocity, etc ) of how a simple 2 DoF robotic arm rotates. I am using the RoboAnalyzer simulator 1 . It has a Inverse Dynamics setting of "Free&...
agribot's user avatar
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Body angle of a centre-articulated robot

Wondering if anyone can help me out with this one, or point me in the right direction. I am working on a centre-articulated robot, which is steered via a push-pull chain drive. The chain drive is ...
Alec Gurman's user avatar
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2 answers
68 views

Force sensors output when inclined

So here is the context: I am working on a motorcycle simulator. It consists of a motorcycle frame mounted on different actuators (see picture on the left). In particular, the two actuators at the ...
Pauline's user avatar
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1 answer
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Why in forward bending knee orientation in quadruped legged robot require less torque in knee joint?

I'm trying to find answer in terms of physics explanation, why knee joint torque requirement is less in the forward bending leg orientation of a quadruped legged robot. I'm referring this article, in ...
Dibyasankha Kundu's user avatar
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1 answer
101 views

3-links Robot Dynamic PD Computed Torque Control

I am designing the PD control of 3-links robot using Simulink. I can't figure out what to do in the 'Robot' block to get the acceleration d_qq back to calculate the error. What is happening in this '...
shippo's user avatar
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1 vote
1 answer
180 views

How to solve this basic dynamics/inverse kinematics problem

Suppose I have a 6-DOF robot arm with revolute joints whose tooltip is at some position $\bf{r_0}$ and I want to move it through some trajectory ${\bf r}(t)$. For simplicity, assume there are just 2 ...
guero64's user avatar
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1 vote
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512 views

Computation of centrifugal and Coriolis matrix

So I have a seesaw-cart electromechanical system which I want to control. It has 2-DOF (the angle of the seesaw $\varphi$ and the cart position $s$). I used the Euler-Lagrange method to get my ...
BigDuckPlaya's user avatar
1 vote
1 answer
99 views

Extract the potential energy from the gravity vector

I have a recursive Newton Euler algorithm from which I can compute the gravity vector. My question is, which is the better way to compute the potential energy? I know the following relation between ...
DarioZ's user avatar
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1 vote
1 answer
35 views

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 ...
Marc Schwambach's user avatar
2 votes
1 answer
190 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....
Teo Protoulis's user avatar
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98 views

Park and Lynch $F = ma$ derivation for a single rigid body

I'm having some conceptual difficulties with a derivation presented in the Modern Robotics text by Park and Lynch. Here are the relevant parts: At the beginning of the book, they insist that ${\it ...
HelpMe's user avatar
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1 answer
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Peter Corke Robotics Matlab Toolbox the problem of inverse dynamics in the Franka Emika Panda model

I have the following question about the Franka Emika Panda dynamic model. In case I perform the solution of the inverse dynamics problem using Robotics Toolbox (Peter Corke) I get different results ...
Daniel Kajzr's user avatar
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1 answer
187 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 $\...
nrofis's user avatar
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2 votes
1 answer
242 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 ...
Prakriti Khilnani's user avatar
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1 answer
135 views

Implementing Dynamic Balancing on Robot Dog

I made a robot dog using Lewansoul LX-16a Smart Serial bus motors and a 3D printed body. I am using an Arduino Mega 2560 to control everything. I already have the inverse kinematics working. But for ...
DragonflyRobotics's user avatar
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205 views

what is difference between twist and classical velocity

In ch 8.2.1 Classical Formulation in the book Modern Robotics by Frank C. Park I know some remarks about this formula.The origin of coordinate system is coincidence with the mass center of the rigid ...
eason's user avatar
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perplexity about ch8.2.1 the linear dynamics, in the book <modern robotics>

From previous chapters, I think I have understand the twist, it is about the angular velocity and the linear velocity, the difference is that linear velocity is not one fixed point in the body but is ...
eason's user avatar
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70 views

Spherical Parallel Manipulator Lagrangian problem

I faced a very serious problem and I urgently need the help of specialists in robotics, mechanics, physics and mathematics. I am trying to derive equations of motion from the Lagrangian of a spherical ...
dtn's user avatar
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Multidimensional obstacle avoidance in ODE. Part II

Multidimensional obstacle avoidance https://math.stackexchange.com/questions/4146255/multidimensional-obstacle-avoidance-in-ode For some time, I studied this question more closely and came to the ...
dtn's user avatar
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