Feed Forward

It is the topic of a lecture “Mechatronics” last week, about “feed forward system”
Now “feed back system” is very popular. Feed forward is a simpler system, which had been the only system of controllers, before a feed back systemappeared.

What is feed a forward system? The answer is, there’s no feed back.
The input is not changed with the output.
It is not flexible, sometimes dangerous if it includes heat , chemical reaction etc.
But it is simple.

Think about a driver pushing the pedal to accelerate his car.
Let θ to be the angle of pedal and v to be the velocity of the car.

The professor drew on the blackboard, a curve of change in v (vertical axis) with change in θ (horizontal axis), as the specification of the car in question.
Then he asked:

“If the driver controls his car in a feed forward system, what curve between v and θ should be drawn in his brain, in contrast to this curve for his car? ”

It seemed us to be a difficult question. No one could imagine it.

Then he drew another curve next to the original, and said, “It should be exactly the same. that means, the driver should know the spec of his car completely, in order to control it without a mistake.”

Oh yes, that’s right.

Moreover converted the graph, which had been in v(output)- θ(input) form, to θ(output)-v(input) form. “Actually the driver will think, how much θ he should output, based on an information of v which input to him.”

Yes, I understood how important it is to ensure quantitatively or semi-quantitatively, what sewms at a glance so easy and spontaneous.


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