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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41 views

Can knowledge of robot's dynamics help in motion planning?

Some planners assume a kinematic model of the robot for example diff drive or omni directional etc. while generating motion plans for the robot. Can knowledge of the dynamics of the robot help ...
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Determination of the operational space dynamic model (Task space)

I am trying to implement a hybrid Force/Motion controller for a quadruped. To do that I first need the Inverse Dynamic Model of the robot in Operational Space. I found a lot of resources on how to ...
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4 wheeled differential wheeled (skid-steer) robot steering problem

My question is about a square shaped differential wheeled robot, I built, that has a hub-motor (BLDC motor) attached to each corner, i.e., the wheels on the same side, either left or right, have the ...
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1answer
30 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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49 views

Cannot get 3 DOF bicycle model to run correctly

I'm trying to simulate a vehicle using a dynamic bicycle model but I cannot seem to get it working. If I set a constant steering angle the lateral velocity grows exponentially and creates impossible ...
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286 views

Why do we need coriolis and centrifugal forces when it comes to the dynamics of a robotic arm?

So we all know (and love) the typical dynamic equation of a robotic arm: $$ M(q) \ddot{q}+C(q,\dot{q})\dot{q}+G(q)=\tau $$ Where M is the mass matrix, G is gravity and C is Coriolis and Centrifugal ...
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2answers
605 views

Understanding the kinetic energy expressions for a 1 link vs 2 link robot arm

I'm studying these lecture notes on dynamic models of robot arm links, slides 33-36, where two examples are given for the kinetic energies for a single link and two link robot arm. In the single ...
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28 views

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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1answer
47 views

Non-planar robot Dynamics error using Roy Featherstone's Spatial toolbox

I am using this code to test robot dynamics of above robot using Spatial Toolbox function: FDab(rob, [0;0;0], [0;0;0], [0;0;0]) %a_grav = [0,0,-9.81] But it ...
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1answer
163 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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90 views

3-DOF Robot Dynamics error in Robotics Toolbox

I am trying to compute dynamics of 3 DOF robot using Robotics Toolbox by executing this code: robot.accel(q, zeros(1,3), zeros(1,3)) But I am getting this error: ...
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140 views

Effiecient computation of coriollis matrix

I want to perform kinodynamic motion planning on a 6DoF hybrid manipulator. I calculated mass matrix, coriollis matrix etc using the lagrangian method. The coriollis matirx was calculated symbolically ...
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1answer
208 views

When are non-diagonal matrices advantageous for linear quadratic regulators?

When setting up an optimal control problem using a linear quadratic regulator, one often chooses semi-definite matrices Q and R such that the objective function J has the form $$J=\int_{t_0}^{t_f}(...
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241 views

Calculate the inertia matrix of complex robotic mechanism

Motor, irregular rigid body of Different materials Forming a single robotic. For example, Industrial robot, every geometric shape of the link is very complex. But we can find inertia matrix form CAD ...
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51 views

Determine moments of inertia of a tool experimentally

I've mounted a broom as an effector of the Kuka IIWA. I've configured a tool in the Kuka Sunrise Workbench software with approximative mass and center of gravity. However, when control is started with ...
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What's the difference between a holonomic and a nonholonomic system?

I was wondering if a 1D point mass (a mass which can only move on a line, accelerated by an external time-varying force, see Wikipedia - Double integrator) is a holonomic or a nonholonomic system? Why?...
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Doubt linearizing 2D planar quadrotor equation of motion

Equation of motion for 2D planar quadrotor are as follows $\ddot{x} = \frac{1}{m} (u1+u2)sin(\theta)$ $\ddot{y} = \frac{1}{m} (u1+u2)cos(\theta) - mg$ $\ddot{\theta} = \frac{r}{I} (u1+u2)$ How to ...
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168 views

Free Multibody Dynamics Software?

I'm working on modelling a feller buncher, its end effector consists of a saw to cut trees and claws to bundle them together. I'm looking for a free/open source software that can simulate dynamics of ...
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3answers
2k 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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1answer
78 views

Bullet vs SimMechanics: Inverse Dynamics and sensed forces/torques

This question may be a little broad, but I could not find any other information. How accurate are the inverse dynamics functions in SimMechanics compared to Bullet? How accurate are the sensed/...
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2answers
586 views

Combining centres of mass and Inertia tensors

I'm trying to build the dynamic model of a 6DOF robot, and the company that has built it, kindly provides a document having the masses, centres of mass, principal axes of inertia and principal moments ...
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2answers
847 views

Estimating yaw angle and yaw rate for a frontal vehicle

I would like to know if it is possible (and if it is possible how can it be done) to estimate the yaw angle and yaw rate of a vehicle in front of me knowing the following information: -my speed (x,y,...
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how to introduce 2 inputs into a matlab block function that processes only one variable at a time? [closed]

Using SIMULINK, I wanted to optimize 2 variables with the ant colony optimization algorithm; which is written in a matlab function block, the function is of type function y = f (x) it has only one ...
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317 views

Quadcopter mathematical model and controller design

if we just examine the translational dynamics (X and Y direction), the dynamics are coupled, So if I want to design a PID controller to control the position, the outcome will be unpredictable because ...
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3answers
704 views

How to apply A bang-bang signal of amplitude 1 N and 1 s width as an input force to reproduce certain results in Matlab?

I working on dynamic modeling and simulation of a mechanical system (overhead crane), after I obtained the equation of motion, in the form: $$ M(q)\ddot{q}+C(q,\dot{q})\dot{q}+G(q)=Q $$ All the ...
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1answer
228 views

Reachable Position with endeffector robotic arm

I have a 7 DOF robotic Arm. All the 7 Joints are rotational and have upper and lower joint angle limits. Now assume my end effector has a certain Pose $x = [X, Y, Z, a, b, c]$. My Question now is ...
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0answers
48 views

OpenRAVE “fast-forward” physics simulation?

I am working with OpenRAVE simulator and I am using ODE Physics (OpenRAVE plugin to support ODE). I have a robot in an environment and multiple other objects that are subject to the physics engine. I ...
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5answers
146 views

Why we want to write all linear system into form of first order differential equations?

It seems to be taken granted that when we deal with some control system, the first thing we want to do is to linearize the system and put it in form of first order differential equations like $\dot x =...
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2answers
125 views

Dynamic model using identification for control

I'm currently working of a 5 DOF robot, for which i'd like to compute the dynamic model through identification. I have experimental data representing torques (inputs) and positions (outputs). How can ...
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1answer
121 views

PID control related to lagrange equation

I'm a beginner in robotics and so far followed the lecture series by Prof. Oussama Khatib and some blogs and papers. currently I'm following this studywolf blog. in the end I plan on building a simple ...
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178 views

Robot with Double Integrator Model

Does the robot described by Double Integrator Model is holonomic ? Let's say we have a robot with dynamics described by equations \begin{cases} \dot x = v, & \\ \dot v = \frac {1}{m}u \end{...
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589 views

Proportional controller error doesn't approach zero

I'm reading this pdf. The dynamic equation of one arm is provided which is $$ l \ddot{\theta} + d \dot{\theta} + mgL sin(\theta) = \tau $$ where $\theta$ : joint variable. $\tau$ : joint torque ...
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73 views

Doing a project for college for a manned drone theortically only

Weight of the Drone in total will be 240 Kg. It Will be a quad copter drone setup but with 8 rotors(two on each corner) for redundancy purpose. Aim is achieve Thrust/weight ratio of 2. So need total ...
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2answers
140 views

When and when not to use the Inertia tensor in Kinetic energy computing?

I'm trying to obtain the dynamic model of a 3D robot (academic problem), I have obtained the D-H table, the transformation matrix for each pair of links and the total transformation matrix. Now I'm ...
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1answer
129 views

Two 4 bar mechanism vs stepper motor on each linkage in a 4 DOF robotic arm

I am planning to make a 4 Degree of Freedom(DOF) robotic arm. I have a confusion in mechanical design of the robot. Shall I use two 4 bar mechanisms to reduce the number of actuators? or a stepper ...
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1answer
55 views

“modern contact dynamics” - Why are spring-damper contact models not being used anymore for dynamic simulations in robotics?

While researching different physics engines for dynamic simulations in robotics I found the following statement on the MoJoCo documentation website: Physics engines have traditionally separated in ...
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1answer
745 views

6DOF serial robot (PUMA robot) dynamic model equations

I'm trying to find the most simplified (though accurate) calculations for the dynamic model of a standard 6DOF serial robot (PUMA robot). I found this great paper: https://www-cs.stanford.edu/group/...
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337 views

Calculation of inertia values of Ic and Im

In my dynamic model of two wheeled mobile robot, it has the total equivalent inertia, noted $I$, described by the equation below, $I_c$ is the moment of inertia of the DDMR about the vertical axis ...
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1answer
384 views

Dynamics of a robot manipulator with a force acting on the end-effector

I have this exercise The dynamic model is $B(q)\ddot{q}+S(q,\dot{q})\dot{q}=\tau+\tau_k$ Where $B(q)$ is the inertia matrix, $S(q,\dot{q})\dot{q}$ are the centrifugal and Coriolis terms, $\tau$ is ...
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1answer
230 views

Dynamic model of two wheeled mobile robot

I wanted to design a LQR controller for my two wheel mobile robot. What are the equation of two wheeled mobile robot can be rearranged into state space model? My two wheeled mobile robot is nonlinear ...
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1answer
134 views

Jacobian of kinematic IMU Model

I have the following problem: given two Input Vectors $x = \begin{pmatrix}x\\y\\z\\v_x\\v_y\\v_z\\q_1\\q_2\\q_3\\q_4\end{pmatrix}$, $u = \begin{pmatrix}a_x\\a_y\\a_z\\w_x\\w_y\\w_z\end{pmatrix}$ time $...
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2answers
407 views

Calculating C for a 6-DOF robotic arm

I've seen this equation for calculating the dynamics of a robotic arm a bunch: $\boldsymbol{\tau} = \boldsymbol{M}(\boldsymbol{q})\ddot{\boldsymbol{q}} + \boldsymbol{C}(\boldsymbol{q},\dot{\...
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1answer
68 views

Confusion about Jacobians stemming from class notes

So I thought I understood well enough what a Jacobian was (in the context of an $n$-DOF robot) -- a function that takes a vector of n joint positions and returns an $n \times n$ matrix that can be ...
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87 views

robotic arm DOF

I'm working on an assignment and was wondering aobut the degrees of freedom this system has. The generalized coordinates are: $\underline{q}:$ \begin{bmatrix} x \\ \theta_{1} \\ \theta_{2} \\ \end{...
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1answer
92 views

Quadrotor SE3 Controller: Calculating Rd_dot

I am trying to simulate and implement the controller in the paper Geometric Tracking Control of a Quadrotor UAV on SE(3). I have the dynamics implemented, however I am stuck at one part in the ...
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101 views

How to interpret and apply results from Inverse Dynamics

I am applying Recursive Newton Euler Inverse Dynamics to a simple two link model. If I apply the result torques and forces using PhysX or Bullet Physics I get unexpected results. The model spins and ...
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2answers
742 views

Quadrotor Dynamics: Calculating angular velocity of quadrotor

I am trying to simulate and implement the controller of the paper Geometric Tracking Control of a Quadrotor UAV on SE(3). To do this I need to first implement the dynamics of the quadrotor. According ...
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1answer
114 views

Urdf as a way to model dynamics?

Since urdf format serves the purpose of kinematic model but also extends for dynamical properties such as mass,moment of inertia and centre of masses, can it be considered a viable dynamical model of ...
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1answer
70 views

FPGAs and stepper motors for precision control

I'm looking at this Dexter robot that uses FPGA controllers to get really accurate position and force sensing on a cheap ($2K) arm. They say that the speed of the processor lets them get this accurate ...
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2answers
2k views

What's the diffrence between $H_2$ and $H_\infty$ controll?

There a two controllers named $H_2$ and $H_\infty$. Can someone explain if: They have have guaranteed stability margins? Do they have a Kalman filter? Are they for both SISO and MIMO systems? Can I ...