Feedback: Advanced motor designs, gain scheduling

Readers provide feedback on Control Engineering articles on advance motor designs and on gain scheduling. See links, comments, below.


Articles on advanced motor technologies and on gain scheduling drew reader feedback recently. See comments and links to articles, below.

FEEDBACK: Gain scheduling

Gain scheduling tutorial, Control Engineering Back to BasicsConcerning your article titled “How gain scheduling works” on page 56 of the January 2011 edition of Control Engineering, I have a suggestion.

Instead of implementing gains scheduling, why not linearize the process feedback to units of volume?  If you use the water level to calculate the current volume of water in the tank, the need for gains scheduling goes away.  While the gains of the PID are no longer scheduled, the effective gain of the system still changes – so the engineer would have to be careful to tune his PID so that it was still stable in the region where the ratio of tank level to volume was the highest (in this case, the mid-point of the tank).  However I would argue that the overall system will be easier to tune, take less time to tune, and be simpler.  Plus it allows you to determine the percentage of the tank’s capacity, which will likely be more useful to the operator or controls software than percent of non-linear level.

John Blystone, Instrumentation & Controls Department Supervisor
Louis Perry & Associates Inc.

FEEDBACK: New motor technologies

South Korea’s Electric Research Institute (KERI) has been building various transverse flux motors for more than 10 years.Great article from Dan Jones on new motor technology. Great to get this by email. [This article was included in the Feb. 10 Control Engineering Machine Control monthly eNewsletter. Others may subscribe to eNewsletters at; browse other motor developments at]

The article cuts across many industries and should be followed up with some details on the individual companies that were cited. [See additional links added below.] I think there is a lot of interest because motors are so widely used and so poorly understood. The connection to the electric car is also a popular theme.

Thanks for a great job. 

Steve Meyer, CEO/Senior Consultant

Solid Tech Inc.

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