# What is the meaning of this symbol in Control System Diagram

I was reading the paper "Full-Speed Range Self-Balancing Electric Motorcycles Without the Handlebar" released in March 2016 by Professor Yang and Murakami in Keio University.

I couldn't figure out what the meaning of the following block is :

from the following control system diagram on page 1915 of IEEE Transactions on Industrial Electronics, Vol. 63, No. 3, March 2016.

I would greatly appreciate if someone could explain the meaning of the mentioned block symbol.

• Is there an index or explanation of the various symbols in the book? Jun 27 at 6:53

If $$\alpha$$ has units of angle and $$\tau$$ has units of torque, then $$I$$ has units of moment of inertia. It is likely to be the moment of inertia about the axis which is being controlled.
The block is very likely a plain gain block which multiplies the angular acceleration signal with the value of the moment of inertia.