Reverse homework question

jdbrandt · Nov 11, 2015

Yes, we get homework questions on here all the time, and usually most are patient enough to help or guide the OP to a solution.

In this case, I have the opposite question:

What are some good examples of PLC programs/systems which involve trigonometry?

Something that actually uses the SIN/COS/TAN functions, and the like.

I thought of motion applications, of course. Flying knives, etc.

What else would be good ones?

I ask, not because I am dreaming up impossible questions for a PLC course, but because I have a cross-training opportunity coming up which this relates to.

Thanks.

kamenges · Nov 11, 2015

I deal with this all the time with pneumatically loaded pivoting lay-on assemblies on winders. The user will command a lay-on force, 30 pounds for example. In order to maintain the commanded force through the roll build the programmer needs to account for the changing gravity load of the assembly as well as the changing force angle of the loading cylinder.

Keith

OkiePC · Nov 11, 2015

At a tire plant we had "beam shears" that had adjustable infeed conveyor angles to convert raw stock into steel belt material for tires' belts. The angle adjusted from 19 to 90 degrees depending on what machine, most of them ran at 22 to 28. We had to use trig in the PLC to calculate the desired encoder values for the angle setting.

Peter Nachtwey · Nov 11, 2015

I would start with the simple vertical speed of the die in a mechanical press.

A wave generator would hyperbolic functions but how about a simple testing machine that generates sine waves.

A ladle pouring hot metal is a good one. The ladle tilts 0 vertical to 100 degrees to empty the metal. The ladle tilts by using a hydraulic cylinder that pushes on a arm attached to the ladle.

Raising pipe for an oil rig. The metal pipe starts out horizontal and is tilted vertically using hydraulic cylinders.

A 6DOF Stewart platform would lots of sines and cosines..

Normally these are all better done in the motion controller and most of the time we use splines or cam tables instead of trig functions where all the heavy math is worked out before run time.

rootboy · Nov 11, 2015

Calculating the mass from a flowmeter and the known temperature of the gas.

jdbrandt · Nov 11, 2015

Peter Nachtwey said:
I would start with the simple vertical speed of the die in a mechanical press.

A wave generator would hyperbolic functions but how about a simple testing machine that generates sine waves.

A ladle pouring hot metal is a good one. The ladle tilts 0 vertical to 100 degrees to empty the metal. The ladle tilts by using a hydraulic cylinder that pushes on a arm attached to the ladle.

Raising pipe for an oil rig. The metal pipe starts out horizontal and is tilted vertically using hydraulic cylinders.

A 6DOF Stewart platform would lots of sines and cosines..

Normally these are all better done in the motion controller and most of the time we use splines or cam tables instead of trig functions where all the heavy math is worked out before run time.

These are all excellent. Yes, this kind of stuff is generally better handled in a motion controller....and perhaps that should be part of the reverse-solution set in addition to the PLC.

The metal ladle operation...I assume the goal is for constant flow of metal. (I worked in aluminum for many years, but not where we had ladles....we had tilt furnaces...and I suppose a tilt furnace and a ladle could be considered the same thing...just different shapes.

James Mcquade · Nov 12, 2015

In the auto industry, we have to plot a hysteresis curve and calculate several
values using sin, cos. We also had to fatigue parts at different angles. I'm sorry, it wasn't my project, so I can only remember bits and pieces of the project.

hope this helps,
james

Gil47 · Nov 12, 2015

In electrical distribution systems Kw and Kvar metering is common
from this data calculate KVA and Power factor

Archie · Nov 12, 2015

I was once asked to find a way to locate a drum center at each end based on a rotating measuring device. I do not have pictures, but the best to think of it is if you had a lathe with a roll of about 500mm in diameter. Above and slightly behind the roll center line is a set of opposing probes on an assembly that rotated down to measure the diameter of the roll. The problem is that you do not know the angle to rotate the measuring device to align it to the center, so you were truly measuring a chord. Also the vector that passes through the 2 measuring probes also does not intersect with the center line of the measuring mechanism's rotation point.

The objective was to take 2 measurements at each end of the roll and calculate the difference in the X-Y positions in order to tell the operator how much to adjust one end of the roll to make it exactly parallel to the measuring device.

I broke it into a mathematic problem which is in the attached PDF. This is truly a challenging academic problem.

nehpets · Nov 12, 2015

I've recently completed a project where I had to monitor the volume in two horizontal tanks, one circular the other elliptical as they were being emptied using a pressure sensor to detect the height of the falling liquid. I can tell you arccos and sin were used.

Steve

mk42 · Nov 12, 2015

This is perhaps a little more simplistic than some of the motion options above, but I've used Sin/Cos a lot to calculate animations on the HMI. For something like a rotary table, if you want to move an object around the circumference, we would calculate the X/Y coordinates in the PLC, and then pass them to the HMI. I worked on another system that needed to display the position of the sun in the sky, and we used the same method.

jdbrandt · Nov 14, 2015

Archie said:
I was once asked to find a way to locate a drum center at each end based on a rotating measuring device. I do not have pictures, but the best to think of it is if you had a lathe with a roll of about 500mm in diameter. Above and slightly behind the roll center line is a set of opposing probes on an assembly that rotated down to measure the diameter of the roll. The problem is that you do not know the angle to rotate the measuring device to align it to the center, so you were truly measuring a chord. Also the vector that passes through the 2 measuring probes also does not intersect with the center line of the measuring mechanism's rotation point.

The objective was to take 2 measurements at each end of the roll and calculate the difference in the X-Y positions in order to tell the operator how much to adjust one end of the roll to make it exactly parallel to the measuring device.

I broke it into a mathematic problem which is in the attached PDF. This is truly a challenging academic problem.

WOW!
The target of my effort is a high school trig teacher (a family member), and this looks like a good challenge.

jdbrandt · Nov 14, 2015

nehpets said:
i've recently completed a project where i had to monitor the volume in two horizontal tanks, one circular the other elliptical as they were being emptied using a pressure sensor to detect the height of the falling liquid. I can tell you arccos and sin were used.

Steve

good one(!)

Archie · Nov 15, 2015

jdbrandt said:
WOW!
The target of my effort is a high school trig teacher (a family member), and this looks like a good challenge.

This is probably a bit beyond high school level, but if any high school student comes up with a solution, I will write them a letter of recommendation to college of their choice.

Reverse homework question

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