Paper: ILITE Drive Train Simulator, v2019

#1

ILITE-DriveTrainSimulator - v2019.2.xlsx (1.6 MB)

Prior Versions

ILITE-DriveTrainSimulator - v2019.1.xlsx (1.7 MB)

This is an updated drive train calculator that puts emphasis on time rather than maximum speed.

Input a target motor, number of motors, gearing, and a wide range of elements about the drive train and electrical system. The output at the bottom shows estimated peak speed, estimated sprint time, minimum system voltage, and maximum voltage while the drive train is at full speed.

  • NEW Now includes the NEO motor with a stall torque of 2.585 Nm and stall current of 105A. Note that minor variations in this stall torque do not really impact the final measurements of sprint time.
  • NEW Select a deceleration model to simulate a full trapezoidal profile of a sprint, start to finish. Never forget, what speeds up must also slow down!
  • Improved voltage ramp and current limiting models
  • NEW Extra output fields within the print boundaries for those who want to calculate their own items based upon the simulator results
  • NEW Includes rudimentary traction limiting on the acceleration model
  • The distance vs time chart now also shows indicator lines for whether the drive train is traction or current limited.
  • Charts that show impacts of varying gear ratios on sprint time, battery usage, and turning efficiency
  • Want to see the effects of Voltage Ramp or Current Limiting on your final sprint time? No problem! Input those parameters into the electrical system
  • Updated acknowledgements! If you would like to learn more, it is easy to go straight to the pros!

Features for the future:

  • Updated wheel slip to account for kinetic CoF
  • Updated current modeling to account for lower current draw during wheel slip
  • Add a graph line for “time to full stop” on the existing “time to target” graphs
  • Re-orient motor cells on the prelim calcs tab to account for copy/paste into those cells directly from the motors tab
8 Likes
Cycling Optimization
Good drivetrain calculator
Paper: AMB Design Spreadsheet v3
Defense and Drivetrains
#2

What is your NEO data based off of?

Exciting to see traction limiting included in this simulator. It was one of the few calculations I turned to other sources to perform in the past couple years.

#3

It is based off of the Kt rating in Richard Wallace’s tests with a controller cut-off of 100A.

1 Like
#4

Very cool!

I’m interested in comparing your drivetrain time-to-distance calculator to mine (based off Ether’s White Paper). One of the first things I see is that you only ask for the static CoF for the wheels. How do you calculate acceleration when slipping without the kinetic CoF?

I hope to do a deeper dive into your calculations in the next few days to see how they compare to Ether’s. I will probably have some more questions then. If you have any information about how you developed your simulator or have the calculations in a more readable format than excel formulas, I’d love to see them.

#5

Great question, and the answer is simple: I don’t.

This decision was for simplicity’s sake given the limited time I could put into iterating on the spreadsheet from last year. I’ll definitely note this for next year though.

#6

I just ran some numbers in this to compare it to my new dynamic simulator (my new one is still rough, but I promise to release it eventually). I got the same results, given the same inputs. Good job!

I have a slight difference in the handling of slipping. Although you should not design for this to happen (and should lower the current limit down to the traction limit point), you still correctly model the loss of traction (and acceleration), but the motor current stays high. If you calculate the motor current/torque from the actual tractive force (limited by traction) then your currents/voltages will be a bit more reasonable. This doesn’t change the distance, but does change the power consumption and potentially min voltage. It’s still not technically correct, since the motor speed will be higher than modeled, but it’s closer.

I did notice that my name is wrong though, you credited me as Brian Palardy. It’s actually Andrew Palardy, and Bryan Culver. Thanks for the credit though, I appreciate it.

1 Like
#7

Thanks for the feedback Andrew!

I will definitely correct the names.

#8

Thanks! This looks very useful and is working great in Excel. Has anyone succeeded in using this in any freely available spreadsheet programs? Our school doesn’t have MS Office.

In Google sheets, the drop-downs work but it is missing most of the chart output.

In LibreOffice Calc the charts look great, but none of the dropdowns work!

Is there anything I can configure to get these to work better, or do I need to use my own Excel account when we are working with these?

#9

There are tradeoffs between accessibility, version control, tool features, and of course expense, when creating complicated tools like this.

If you take the motor specs from the ‘Motors’ tab, and copy them to ‘DT-Prelim Calcs’ cells B6-B9, then LibreOffice should work better for you. In next year’s iteration, I’ll make this copy/paste a little easier by re-orienting those cells on that tab.

#10

One thing I’ve noticed is that on the Movement Characteristics graph, the simulations of the current limits kicking in don’t seem to be directly impacted by a robot’s weight. While the acceleration peak(s) move along the time axis as the weight is adjusted (and the current limit indications move with them), the presence or absence of current limits do not seem to change as I adjust the robot’s weight. Obviously a lighter robot is going to demand less current from its drive motors, so there should be thresholds in which these current limits are not presence when a robot’s weight is reduced and appear as the weight is increased.

FRC Battery Health