Simple Angle Conversion

[FireFist-Redhawk]

I cannot think this morning... what I need is super simple I feel like, but I can't figure out an easy way to implement it. Please halp.

Inputs: angles c and d:
current angle = c
desired angle = d

Output: angle z that is closest angle to c but is also in the set {d, d+-360, d+-720, ...}

examples:

c=0
d=270
z=-90

c=765
d=0
z=720

c=-361

d=-1

z=-361

c=0

d=3,602

z=2

[GerdW]

Hi Andrew,

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@FireFist-Redhawk wrote:

inputs: angles c and d:
current angle=c
desired angle = d

output: angle z that is closest angle
examples:

c=765
d=0
z=720

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Please explain this example!

Why should z be 720° when c=765° (=720°+45°) and d=0°???

[FireFist-Redhawk]

Hi GerdW,

I'm not sure I understand you're query. If my current angle shows 765, and I want to go to 0 (same place for me as +-360,+-720), then z is 720 because its the member of that set whose value is closest to my current angle, 765.

[FireFist-Redhawk]

That description was initially a comment label in LV, I went back and cleaned it up to possibly get rid of the confusion, and added a couple more examples.

[crossrulz]

I think this does everything you need.

The idea here is to find the differences and keep that difference in a shift register.  Add (or subtract) 360 until the absolute value of the difference is greater.  The previous value is therefore the closest value.

[altenbach]

Can you explain it graphically instead?

[GerdW]

Hi Andrew,

please explain this one:

c=0
d=3,602
z=2

Edit:

I think I get this one - decimal separator confusion. I'm used to commas instead of points…

[Sebastian.Weber · Accepted solution]

Let's say

e=(c-d)

and z'=(z-d)

then, you are looking for a z' in {..., -720, 360, 0, 360, 720,...} for which the difference to e is minimal.

Dividing e by 360 using the quotient & remainder VI gives a quotient which, multiplied with 360 again, is the next lower multible of 360 to e. If the remainder is >180, add 360 to get the nearest value. This is z'. Add d to get z.

In LabVIEW:

EDIT:

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c=0

d=3,602

z=2

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z must be in {..., d-360, d, d+360,...}, so it must be d=3,602 to be next to c....

[altenbach]

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@crossrulz wrote:

I think this does everything you need.

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That's very dangerous code because it will run forever if any of the inputs is NaN. 😮 Maybe you want to reverse some logic so it stops on FALSE instead.

(I am pretty sure there is a loop-free solution ;))

[FireFist-Redhawk]

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@altenbach wrote:

Can you explain it graphically instead?

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I think we all have the idea at this point but it took me a few mins to make, so may as well post.