Skip to main content
20 votes

Position Control vs Velocity Control vs Torque Control

I'm going to take a slightly different tack to Chuck. What is Torque Control? For me, Torque Control is about performing a move with an explicitly defined torque, rather considering torque just the ...
Mark Booth's user avatar
  • 4,273
16 votes

Position Control vs Velocity Control vs Torque Control

Torque is analogous to force for rotating systems, in that: $$ F = m a \\ \tau = I \alpha \\ $$ Where $\alpha$ is angular acceleration and $I$ is moment of inertia. $m$ and $a$ are mass and linear ...
Chuck's user avatar
  • 16k
8 votes
Accepted

Can a state matrix have a row of zeros?

Yes, a state matrix with zero rows and/or columns makes sense and is viable. It typically signify pure integrators in the system. In the example you give, $$ \dot{v} = -\frac{b}{m} v +\frac{1}{m} u ...
Christo's user avatar
  • 385
7 votes

What's the difference between a holonomic and a nonholonomic system?

A holonomic constraint is a constraint on configuration: it says there are places you cannot go. That is a reduction in freedoms. That’s (usually) bad. A nonholonomic constraint is a constraint on ...
Franky's user avatar
  • 536
7 votes
Accepted

Damping vs Friction

A force balance equation is typically written as: $$ m\ddot{x} + b\dot{x} + k{x} = F \\ $$ where $F$ is an applied force, $x$ is position, $\dot{x}$ is velocity (first derivative of position), and $\...
Chuck's user avatar
  • 16k
7 votes
Accepted

What does SE mean in robotics literature?

In that context, SE means "Special Euclidean" group, e.g. SE(3)* which is shorthand for "the special Euclidean group of rigid body displacements in three-dimensions". *Planning ...
sempaiscuba's user avatar
  • 1,074
6 votes
Accepted

D(q) Inertia Matrix and the Jacobian Matrix

I think this is a matter of notations. In the given formula for $D(q)$, the matrices $J_{vi}$ and $J_{\omega i}$ are not simply the direct extraction of columns of the Jacobian of the system. $J_i$ ...
Petch Puttichai's user avatar
5 votes

Mathematical modelling of system dynamic on matlab

the Simulink diagram is straightforward. It is a matter of connecting blocks. For the differential equations provided in your post, the simulink is For $u_1$ and $u_2$, I've chosen the unit step. ...
CroCo's user avatar
  • 2,452
5 votes
Accepted

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

Series elastic actuators tend to have more stable force control because the spring filters out the high-frequency motion of the mechanism. A low frequency in the system dynamics means that you can use ...
hauptmech's user avatar
  • 4,445
5 votes

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

In short answer: yes Kalman filter is a special case of an $H_2$ observer Yes Yes ... LQG is just Kalman filter + LQR controller, which are both special cases of $H_2$ Depends on the use case. $H_2$ ...
ryan0270's user avatar
  • 2,814
5 votes
Accepted

Confusion about Jacobians stemming from class notes

Short answer Robot Dynamics and Control by Spong et al. (especially Chapter 5) can definitely help you on this matter. Long answer First of all, you are partially correct about a Jacobian. It is ...
Petch Puttichai's user avatar
5 votes

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

The author appears to be writting in a self promotional style, where the details listed about other work are simplified or ignored so that their claim, that their approach is better, can be ...
hauptmech's user avatar
  • 4,445
5 votes

Can workspace of a manipulator change after considering its dynamics?

The workspace of a manipulator is strictly determined by its kinematics. Since kinematics only consider the geometry of motion, without regard to forces and torques needed to accomplish tasks, you ...
SteveO's user avatar
  • 4,396
5 votes
Accepted

Cartesian Impedance control Damping Design (Double Diagonalization)

A hint towards what the answer is given in the paper. Namely, one can use the generalized eigenvalue decomposition, which in this case can be formulated as finding eigenvalues $\lambda \in \mathbb{R}$ ...
fibonatic's user avatar
  • 941
5 votes
Accepted

Velocity-Control of a manipulator without a dynamic model

Your intuition is partially correct in the sense that you ought to go with position control implemented via velocity commands resorting to a kinematic (not dynamic) model of the manipulator. This can ...
Ugo Pattacini's user avatar
4 votes

Damping vs Friction

Friction would be your standard "sliding friction", and exerts a force opposing the motion, proportional to the load (or the normal-force of the load, when talking about your classic sliding), but ...
Mark's user avatar
  • 331
4 votes

Dynamic torque simulation for a 6 DOF robotic arm

The dynamics of robotic arms are fairly complex, especially when there are more than three joints to consider. The problem is that the movement of each joint moves all the links beyond it, which can ...
BarbalatsDilemma's user avatar
4 votes

What's the difference between a holonomic and a nonholonomic system?

Holonomic constraints are constraints that can be expressed in the form of an equation relating the coordinate of the system and time Non-holonomic are constraints that cannot be expressed in the ...
Gori Erick's user avatar
4 votes

Position Control vs Velocity Control vs Torque Control

I think Mark Booth's answer was best. Talked about the applicational differences between the modes, without getting into theory or detracting from the original question. If I can expand a little ...
Rob Koch's user avatar
4 votes

What does SE mean in robotics literature?

It is a mathematical concept call the "Special Euclidean" group. Roughly, it is a combination of a rotation and translation. You'll also frequently see SO3, which is the special orthogonal group which ...
ryan0270's user avatar
  • 2,814
4 votes
Accepted

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

About why screw axes: According to Kevin Lynch in his video of Twists, "just like the time-derivative of a rotation matrix is not equivalent to the angular velocity, the time-derivative of a ...
daniglezad's user avatar
4 votes

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

I will use Mr. Richard Feynman's quote to answer your first question: Finally, we make some remarks on why linear systems are so important. The answer is simple: because we can solve them! Yes. That'...
CroCo's user avatar
  • 2,452
4 votes
Accepted

Finding Mass/Inertia Matrix of a robot

The inverse dynamics of a robot is given by the relationship $\tau = D^{-1}(q, \dot{q}, \ddot{q})$ where $\tau \in \mathbb{R}^N$ is a vector of the required torque per joint and $q \in \mathbb{R}^N$...
Peter Corke's user avatar
  • 1,702
4 votes
Accepted

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

But my understanding is that all calculations happen relative to the base frame This is incorrect. Take a look at this two-link arm manipulator. The point ($x_2,y_2$) is obviously expressed in a ...
CroCo's user avatar
  • 2,452
4 votes
Accepted

Moment of Inertia of a Dumbbell

First, I don't get the same mass for the spheres. Volume of a sphere is $\frac{4}{3}\pi r^3$, right? When I do $5600\left(\frac{4}{3}\right)\left(\pi\right)\left(0.1^3\right)$ I get a different answer....
Chuck's user avatar
  • 16k
4 votes
Accepted

Motion profile and Motion control scheme, how do they interact?

These two concepts are complementary and you use them together, the motion profile providing the input to your control scheme. At each time-step the motion profile gives you the reference values for ...
50k4's user avatar
  • 6,682
4 votes

Robot model explodes in Gazebo

This is a famous crash in Gazebo, similar to the one shown below.  It is one of the confusing errors. To debug this issue, start the Gazebo with simulation paused. We can pause the simulation by ...
Robotawi's user avatar
  • 510
3 votes

Dynamic torque simulation for a 6 DOF robotic arm

I think you may be going about this problem wrong. If you find a simulator that reports joint torques, then what? Are you going to iterate through every possible start and end location? You should ...
Chuck's user avatar
  • 16k
3 votes
Accepted

What is the bicycle model for a dynamic robot?

The bicycle model is a simplified model of vehicle dynamics. It's really common so I'm not sure why a web search did not get any results for you. A random paper, first one in my search that had a ...
hauptmech's user avatar
  • 4,445
3 votes

Combining centres of mass and Inertia tensors

You are lucky to have the inertial parameters for the robot! This is something that manufacturers very rarely share and it is hard to reverse engineer. Given that you have these inertial parameters, ...
Peter Corke's user avatar
  • 1,702

Only top scored, non community-wiki answers of a minimum length are eligible