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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17 views

Dynamics of a mobile robot (Roy Featherstone's spatial_v2 toolbox & Simscape) [on hold]

I am using Roy Featherstone's spatial_v2 to model a mobile robot. I have a Simscape model of the robot that I use to generate test case and I encountered a situation that I don't understand. I have ...
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20 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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27 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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11 views

Using Simulink Interpreted MATLab fcn for robot dynamics using Robotics Toolbox

I am using Interpreted MATLab fcn to compute forward dynamics. I am using code of accel in which I have added my robot model in the beginning, making the accel function: ...
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15 views

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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1answer
19 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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1answer
48 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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2answers
23 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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22 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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25 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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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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36 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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56 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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1answer
48 views

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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213 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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65 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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26 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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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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1answer
95 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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43 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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151 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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5answers
122 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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63 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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62 views

Why using screws instead of homogeneous transforms in kinematics and dynamics?

Can anyone give a justification for using screws (twists, wrenches) instead of the traditional approach (rotation matrices, homogeneous transforms)? Even if screws are more compact, the situation gets ...
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70 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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64 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
63 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
115 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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2answers
160 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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1answer
41 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
90 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
131 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
78 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
199 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
56 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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421 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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75 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
72 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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57 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
480 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
885 views

D(q) Inertia Matrix and the Jacobian Matrix

There is something I need to verify. Say we have the following RPR robot manipulator. The DH table yields 3 rotational matrices: \begin{equation} R^0_1, R^0_2, R^0_3 \end{equation} Using these ...
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1answer
88 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
205 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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59 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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818 views

What does SE mean in robotics literature?

I've come across the abbreviation SE several times recently. I know it has to do with the pose of the robot, and the degrees of freedom. Most recently I found it on page 8 of this paper: D. Kragic ...
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211 views

Holonomic constraint forces using Lagrange multipliers

Consider a multibody robotic system with Lagrangian $ L = \dot{q}^{T}M\dot{q} + V $ and equations of motion of the form $$M(q)\ddot{q}+C(q,\dot{q})\dot{q}+A^{T}(q)\lambda+N(q)=0 $$ where $N=\frac{\...
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66 views

clarity in understanding the moment of inertia matrix D and Coriolisis and centripetal matrix C as per attached equations

Would appreciate if anyone could help me understand the how if equation 6 and 7 are derived. Helping with any one D22 and C32 would suffice.
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426 views

Euler-Lagrange Dynamic model

I'm working on a masters thesis and need to calculate Mass inertia matrix ($M$), Coriolis/Centrifugal matrix ($C$), and the gravity matrix ($G$) in the equation $M\ddot{\theta} + C\theta + G = \tau$ (...
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2answers
716 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 ...
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91 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{...