Friction as B times angular speed?

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SUMMARY

The equation for friction in a rotating motor is defined as Tfriction = B × dθ/dt, where B represents the viscous damping coefficient. This equation parallels the translational motion equation F = B dv/dt, indicating that the damping force is proportional to the rate of change of angular displacement. The concept of damping in rotational systems is crucial for understanding control systems, particularly in the context of motors and their performance characteristics.

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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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