What is a nominal load and payload in control engeneering?

[skyhj105]

Hi. I have read some books about control engeneering .
In some books, there are some terms which are ambiguous to me.
The parts which I can`t understand is that "less mass axis(There are two axis in nanopositioning) frequency response for nomial load is plotted" and "with the maximum payload, the response frequency reduced to 415Hz."
What is the meaning of nominal load and payload in these sentences?

 

[Nidum]

All those terms could make sense in the right context but as stated above they are just a jumble .

Conrol engineering applies to all sorts of systems large and small .

You mention nanopositioning but what is the actual hardware that you are dealing with ?

 

[skyhj105]

All those terms could make sense in the right context but as stated above they are just a jumble .

Conrol engineering applies to all sorts of systems large and small .

You mention nanopositioning but what is the actual hardware that you are dealing with ?

First of all, Thank you for your reply.
Actual hardware what I`m dealing with is commercial serial-kinematic nanopositioning stage which is composed with Noliac NAC2003 piezoelectric stack actuator, Micro 6810 capacitive sensor and 6504-01prove.
I will use this apparatus for physics research. Because It is a two-axis nanopositioning stage, it has two resonance frequencies for each axis.
Resonance frequency of the x-axis is 513Hz and the other axis has 727Hz.
Because of larger resonance frequency of x-axis than the other axis, x-axis will impose greater limitation on performance.(I don`t konw why but it is just written like this. If you know, could you let me know why it is?)
So, in what i have read, x-axis frequency response for nominal load and payload are plotted. The format of the plotted graph is a bode plot

 

[Tom.G]

frequency response for nomial load is plotted" and "with the maximum payload, the response frequency reduced to 415Hz."
What is the meaning of nominal load and payload in these sentences?

"Nominal" in this context would be either a "very light" load or the load that the device is designed to work with.
Without looking at it, the data sheet "maximum" load is probably the load beyond which no reliable position change takes place.

Resonance frequency of the x-axis is 513Hz and the other axis has 727Hz.
Because of larger resonance frequency of x-axis than the other axis, x-axis will impose greater limitation on performance.(I don`t konw why but it is just written like this. If you know, could you let me know why it is?)

Something seems to be reversed in that description. The 513Hz resonant frequency of the x-axis is lower than "the other axis" at 727Hz.
In any case, the frequency response tells you how rapidly the device can respond to an input. 513Hz would be 1.9mS and 727Hz would be around 1.4mS. Depending on how they are defining it, the minimum pulse repetition time may be two to four times these values.

From the numbers you quoted, apparently the X axis stage carries the actuator for "the other axis", thus adding to the mass it must move, and it consequently has a lower mechanical resonant frequency. Think of it as a mechanical spring-mass system. For a given spring, a higher mass will yield a lower resonant frequency.

 

[skyhj105]

Without looking at it, the data sheet "maximum" load is probably the load beyond which no reliable position change takes place.

Thank you for your help. But I have a question about your reply.
First, You said that "maximum"load. Is it same with "maximum payload" that I mentioned before?

In any case, the frequency response tells you how rapidly the device can respond to an input. 513Hz would be 1.9mS and 727Hz would be around 1.4mS. Depending on how they are defining it, the minimum pulse repetition time may be two to four times these values.

Second, frequency response is same as resonance frequency?
I said "Resonance frequency of the x-axis is 513Hz and the other axis has 727Hz" and ,In your reply, you said "the frequency response tells you how rapidly the device can respond to an input. 513Hz would be 1.9mS and 727Hz would be around 1.4mS."
The meaning of resonance frequency, in physically, is the frequency of force which can be absorbed effectively. So energy of system can be larger easily.
Why this is related with response?

 

[Tom.G]

First, You said that "maximum"load. Is it same with "maximum payload" that I mentioned before?

Yes.

Second, frequency response is same as resonance frequency?
I said "Resonance frequency of the x-axis is 513Hz and the other axis has 727Hz" and ,In your reply, you said "the frequency response tells you how rapidly the device can respond to an input. 513Hz would be 1.9mS and 727Hz would be around 1.4mS."
The meaning of resonance frequency, in physically, is the frequency of force which can be absorbed effectively. So energy of system can be larger easily.
Why this is related with response?

I used "frequency response" as a general term, it is often displayed as a graph of response versus frequency. A resonance shows up on such a graph as either a peak or a dip in the response curve. Just as in a usual mechanical system, you usually need to stay below the resonant frequency to have effective control of the action. For instance with a spring and mass system, if you apply energy pulses above the resonant frequency, some of the pulses will occur while the mass is rebounding and energy is wasted fighting the kinetic energy (inertia). Also, some of the energy pulses may occur when the mass is away from the input point and be wasted.

In your nanopositioning stage, it takes a finite time for the actuator to actually move the stage to a new position (F=MA or A=F/M). If the input pulse stops before the movement is complete, you will not get the expected amount of movement. It also takes time for the actuator to return to its rest position after an input pulse. If the next pulse occurs too soon, you will again get either a smaller than expected movement of no movement at all.