# 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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### Position Control vs Velocity Control vs Torque Control

Please can somebody explain to me the difference between Position Control, Velocity Control, and Torque Control? Specifically, I am thinking in terms of a robot arm. I understand that position control ...
28k views

### 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?...
460 views

### Adding an Actuator or Force to a (Featherstone) Articulated Rigid Body Model

I'm working on a project where I need to model a system that is essentially comprised of a series of ball-and-socket joints attached to a base, which is attached in turn to a prismatic joint (rail). ...
596 views

### Building a balancing robot with differential drive

I've already built a two wheeled balancing robot using some continuous rotation servos and an accelerometer/gyroscope. I upgraded the servos to some geared DC motors with 8-bit encoders with the goal ...
2k views

### Optimal location of the center of mass for an inverted pendulum

I'm building an inverted pendulum to be controlled by DC motors, but I've run across a conundrum. Personal life experience tells me that it's better to have a lower center of mass to maintain balance....
321 views

### “Time-varying” and “nonautonomous” dynamical systems and their Lyapunov analysis

It is possible to distinguish the properties "time-varying" and "nonautonomous" in dynamical systems regarding Lyapunov stability analysis? Does it make a difference if the system depends explicitly ...
585 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 ...
585 views

### Effectiveness of a Mobile Robot In Relation To Mass

Do mobile and/or autonomous robots become more or less effective the bigger they get? For example, a bigger robot has bigger batteries, and thus bigger motors, whereas a smaller robot has the exact ...
2k 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 ...
136 views

### Cartesian Impedance control Damping Design (Double Diagonalization)

In the literature, it is often seen that for a system: \begin{align} \Lambda \ddot{e} + D_d \dot{e} + K_d e = F_{ext} \end{align} A dynamic damping matrix is required for a robot to take ...
3k views

### Dynamic torque simulation for a 6 DOF robotic arm

I am working on a 6 DOF robotic arm(industrial manipulator). I have the basic structural specs (dimensions, weights etc) for the links and joints with me. Basically, I want to simulate both static ...
786 views

### Where to make changes for simulation project Bullet/Gazebo/ROS/Orocos

I am starting to develop robotics project which involves simulation (and maybe real world programs) of soft-body dynamics (for food processing) and clothes/garment handling (for textile industry or ...
251 views

### Calculating required torques for a given trajectory using Lagrange-Euler

I have a 2DOF robot with 2 revolute joints, as shown in the diagram below. I'm trying to calculate (using MATLAB) the torque required to move it but my answers don't match up with what I'm expecting. ...
106 views

### Conventional Land Vehicle Dynamic Models for GPS/INS augmentation

I am looking to augment a GPS/INS solution with a conventional land vehicle (car-like) model. That is, front-wheel steered, rear wheels passive on an axle. I don't have access to odometry or wheel ...
2k views

### Why do series elastic actuators have more accurate and stable force control?

The other day, somebody was telling me about a robot in their lab, and they mentioned that it has "series elastic" actuators. But after doing a bit of Googling, I'm still not sure as to what this ...
2k views

### What is the difference between screw and wrench in rigid body motion?

A screw is defined by a six dimensional vector of forces and torques. It can represent any spatial movement of a rigid body (as written here). But I don't get the following distinction between screw ...
990 views

### What is the bicycle model for a dynamic robot?

I was asked this in a phone interview for a robotics job. Googling has not really helped. I assume it is some sort of state prediction model that can be used in a Kalman filter. Can anyone give me a ...
I'm trying to implement the tracking problem for this example using PID controller. The dynamic equation is $$I \ddot{\theta} + d \dot{\theta} + mgL \sin(\theta) = u$$ where $\theta$ : joint ...