Friction as B times angular speed?

AI Thread Summary
The equation Tfriction = B×dθ/dt describes the torque caused by friction in rotating systems, where B represents the viscous damping coefficient. This coefficient is analogous to the damping force in translational motion, represented by F = B dv/dt. The concept of damping in rotational systems parallels that of translational systems, where a viscous fluid provides resistance proportional to angular velocity. Understanding this relationship is crucial for applying control systems effectively. The discussion clarifies the connection between linear and rotational friction equations.
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Friction as B times angular speed??!

Hi,

My control systems book uses a weird notation for the moment caused by friction in a rotating motor. The equation is

Tfriction = B×dθ/dt

Where does this equation come from? The author assumes the reader is already familiar with this equation.

The only definition of friction I am familiar with is F = μN. Obviously the torque is given by T = Fd. I have never learned about torques in rotational systems so I assume the equation used in the book is well known and analogous to the translation friction equation.

What exactly is the B coefficient called? Where does this equation come from?

Thanks.
 
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That equation for translational motion would be F = B dv/dt. It is termed the damping force.

B is the viscous damping coeficient. A damper is represented as a pictogram of a dashpot where a viscous fluid such as oil provides the damping force as a linear function of translational velocity dv/dt, or in rotational motion dθ/dt.
 

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