How to create a negative feedback on a case structure to estimate gear changes from an array of speeds

[mmahon365]

Hi I am new to programming and LabVIEW and I am trying create a program which can estimate gear changes based on what speed bracket the vehicle falls in. The speed is measured by an OBD device and results are logged to a spreadsheet. I have created a sample program which contains a loop which reads the array of speeds row by row. I have then set up a 2 case structures for 2 example speed brackets each bracket represents a gear (3rd gear 35-54kmph, 4th gear 55-79kmph). My problem is I wish to count how many times the speed changes from one bracket to another to symbolise a gear change. At the moment my program will just count the number of speeds within each bracket from the entire speed array.

So in summary I need help trying to create a negative feedback effect so that the first speed which falls within a speed bracket is counted as a gear change but none of the speeds following it are counted until a new speed bracket is entered.

I have attatched the log file and VI any suggestions would be greatly appreciated!

Thanks,

Michael

[AmyNK · Accepted solution]

Hi Michael,

I have made a few changes to your code

1. Replaced the 2 case structures with one, which outputs the current gear.

Using numerics (instead of booleans) as the case selector - you can only use integers; I see in the CSV file that all your speeds are integers anyway, but I added a bit of code which will convert to an integer, rounding down. So where the logic says 35-54kph inclusive, because anything between 54 & 55 will have been rounded down, this will also take in speeds up to 54.999999 (etc) if needs be.

I have then sent this "current gear" variable to a shift register, so each iteration of the while loop can compare the current gear with the previous gear. This case structure outputs a 0 if the speed is outside of the limits (35-80).

2. I have added code which basically says "Is the new gear different to the gear from the last iteration? YES - increment the number of gears variable. NO - Do not change the number of changes variable" This variable is also passed into a shift register, so that is can be passed from iteration to iteration.

3. I have gotten rid of the 2 shift registers which you had added, to index sectios of the array, as it is more efficient/less code to just use the iteration terminal. (Remember iterations of loops are zero indexed).

At the moment, the code which I have written outputs the total number of gear changes (0-3, 0-4, 3-4 4-3, 4-0, 3-0). If you only want the gear changes to be counted between 3 & 4, you could put a case structure around the section of code which I have added a decoration box around, and only run that code if the current/previous gear is not = 0.

I hope this helps - at least to give you an idea of how this can be accomplished.

Thanks,

Amy

[mmahon365]

Thanks very much Amy this is very helpful and a very clear explanation. Really appreciate the help.

Thanks,

Michael

[AmyNK]

Brilliant, glad it helps!

Amy