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4 comments

Do Motors Really Need Sensors?

Posted September 27, 2007 8:09 AM by Sharkles

The servomotor-encoder combination has long been the standard for precise motion control applications, but Klaus Hofer thinks it's overkill. System intelligence can be increased by replacing sensor hardware with inexpensive" observer software," which is basically a mathematical model that calculates speed and torque online. What do you think?

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#1

Re: Do Motors Really Need Sensors?

09/28/2007 7:01 AM

Since several years some manufacturers offer in series such controllers They are getting better from year to year. At the beginning was the problem of mdelizing the motor in a correct way which lead to errors.

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#2

Re: Do Motors Really Need Sensors?

09/28/2007 2:21 PM

there are some ac servos that run on open system with servo controllers , they are fast, precise , but not that reliable as encoder feedback closed loop system

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#3
In reply to #2

Re: Do Motors Really Need Sensors?

09/29/2007 6:50 PM

What do you mean by "reliable"? Where is the problem?

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#4

Re: Do Motors Really Need Sensors?

02/05/2008 12:17 PM

So interesting blog entry indeed. But I have a some doubts about. Is ADC either encounter really so expensive to be replaced? The advantage of traditional method is separated motor and its control facilities.

"Observer software" consists embedded motor's model and uses as I could understand system of matrix equations of system state. Something like dx/dt=Ax(t)+Bu(t); y(t)=Cx(t)+Du(t) where in its turn A,B,C,D are matrix coefficients which consisting motor electro-magnetic and mech parameters. And speed as crucial factor is calculated here in no time. What's happened if physical parameters of motor will be changed by means of any reason and won't coincide with downloaded model (initially quite relevant)? Isn't it more reliable for assurance to leave encounter here? It just like you drive every day from home to work and back being quite relaxed as your brain holds good model of your way. But you need your eyes for accidental case at all.

This technology make process of control much more smooth going without known risk the controller loses it's track for motor. Therefore it would be more effective for authors make main accent on indirect advantages (better non-stress control) but not of direct merits of less cost.

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