anyone great at math?

I have a car traveling one direction, and a machine traveling the opposite direction.
The idea is to have the machine (bridge) travel at a rate to spend the most time possible on the car based off the length of the car but arrive at the end of travel at the right time.
This is the formula I have:
(*formula for calculating reverse bridge speed*)

(* (cnv_speed_inches / 60 * Bridge Travel Distance inches) / (car_length_inches + 28 inches(dist between pes) - Bridge Travel Distance inches) *)

It works in the field, but not in the shop.
The physics engineer found an error in the above formula and changed it to:
(*formula for calculating reverse bridge speed*)

(* (cnv_speed_inches / 60 * Bridge Travel Distance inches) / (car_length_inches + 28 inches(dist between pes) - cnv_speed_inches) *)
This new formula worked in the shop, but not in the field.
I'm perplexed.

In the shop, the car length could be incorrect. The engineer is convinced that the second formula is correct, but the first formula works. But I don't understand either.

Units?
identify/describe/sketch all input variables.
The machine is sitting on top of the car?
what is "pes?" Is it something that lengthens the car, as far as the machine "spending the most time possible o the car" is concerned?

pes = photo eyes

(*calculate bridge reverse speed (BRS) in inch/sec*)
BRS_InSec:= (CnvSpdInSec * BTD_in_real) / (car_length_tmp_real + 28.0 - BTD_in_real - 5.0);

FYI: this is what I am understanding from the description.


Are the photoeyes fixed with respect to the car or with respect to the ground? Do they indicate the start and end position of the bridge?


Where is BTD? Is BTD referenced against the car or over the ground? Is it between my A0/Aend marks, if they mean anything?

BTD stands for bridge travel distance.
The photo eyes are on wash arms attached to the trolley, so basically on the bridge.

I am still not seeing a coherent picture. Treat me like a 5y old. A sketch would be nice, showing start, intermediate and end positions of bridge, car (trolley?), machine.



Is the bridge fixed wrt the ground?


Does the car move relative to the bridge at a fixed rate in one direction?


Does machine move relative to the bridge at a fixed rate in the opposite direction?


What are the relative lengths of the items?

ganutenator said:

BTD stands for bridge travel distance.
The photo eyes are on wash arms attached to the trolley, so basically on the bridge.

Click to expand...

I asked where is the BTD, not what it is. That said, is BTD the distance the machine moves with respect the bridge, or does the bridge itself move relative so something else?

What are the units of cnv_speed_inches? Is the value of 60 a conversion between seconds and minutes?

I'm struggling to imagine this, as well. Perhaps some more text may help us "see" what you are working with.

Is the bridge a device that performs work on the car? Is it meant to lower from some mounting point to do the work and then raise back up? Are the bridge and the car dynamically moving simultaneously, or does the bridge simply lower down as the car passes beneath it and then raise back up as the car exits its station (waiting for the next car to come in)?

Based on you description, the bridge moves to the left (let's say) as the car is sitting on an active conveyor moving to the right (let's say). If the bridge does, in fact move, don't you need to move it back to the starting point to process the next car?

The formulas are also inconsistent. The code you posted shows a 5.0 subtracted in the denominator, which is never mentioned in your first post. I also am wondering what the 60 is meant to represent in the formula in your first post. Is the conveyor speed measured in inches/min, so you need to divide by 60 to convert it to inches/sec (the only conclusion I can draw)?

The bridge travel distance is not clicking with me. If the bridge is actually moving parallel to the conveyor (or "to the left"), then you actually need to go 2 times the BTD, as you have to return to the starting point (right?).

Edit: I see more posts were made while I was writing this. Is this a car wash?

There are a large number of people in the forum who are great at math, and may see this, and may take an interest.


But, by the lord, the OP lacks the gift of clear communication (cf. Siegfried Farnon, ACGAS, season 1, episode 7), and none of us know the process, and even fewer can read minds, so unless they provide a cogent description there cannot be a useful answer.

the 5 inches was added later as an offset for the photo eye.
everything is in inches per second.
and yes, the 60 is probably there to convert the inches per minute into in/ sec.
sorry folks. hard for me to explain.
Hope the video helps?

OK, now for some fun. Before we begin, is the "bridge" exactly the same as what is in the video (immovable, but consists of three zones of spray nozzles to hit the front/side/back of the car)?

no, the bridge moves parallel to the conveyor/car. The trolleys move inboard and outboard to spray the front and back of the car.

ganutenator said:

the 5 inches was added later as an offset for the photo eye.
everything is in inches per second.
and yes, the 60 is probably there to convert the inches per minute into in/ sec.
sorry folks. hard for me to explain.
Hope the video helps?

Click to expand...

Yes, are you talking about the part that starts at 2:52 of the video i.e. here https://www.youtube.com/watch?v=vap1oRysyk8&t=2m52s?


So you want the washer

• to start at the downstream end (on the left in the video i.e. at 2m52s) of the fixed bridge at the same time the front of the vehicle reaches that point,
• to finish at the upstream end (on the right in the video i.e. at 3m14s) of the fixed bridge at the same time the back of the vehicle reaches that point.

Is that what you have been describing?