Optimal Shifting ??

[Mike Bortfeldt]

Sam,

I'll point you to this post I made a number of years ago. For clarification, it was orginally for a 4 speed automatic transmisstion, but the process works just as well for a 2 speed. The time for the reduced power is approximately 50-75 ms. We also run the air pressure around 30 psi.

Mike

[cmwilson13]

i should also say that we had to switch to vexpro ball shifters after andymark changed to screws instead of the roll pin due to shifting at 60 psi we kept breaking screws but 60 psi shifting is worth no delay.

[Alan Anderson]

Originally Posted by cmwilson13

i should also say that we had to switch to vexpro ball shifters after andymark changed to screws instead of the roll pin due to shifting at 60 psi we kept breaking screws but 60 psi shifting is worth no delay.

Instead of changing to a completely different gearbox, wouldn't it have been simpler just to replace the screws with pins?

[cmwilson13]

Originally Posted by Alan Anderson

Instead of changing to a completely different gearbox, wouldn't it have been simpler just to replace the screws with pins?

the vex transmissions just work better in every way. and shifting is smoother with the ball shifter rather then dog gears. and there much lighter and smaller

[JamesCH95]

OP, I think to find optimal shift points you'll have to do a little math to figure out what works best for your particular robot and goals. Providing more details would be great.

In our first attempt at automatic shifting we are utilizing a shift table scheme. A CSV file is loaded onto the robot representing a shift table with throttle position on one axis and speed of the robot on another axis. The robot code automatically sets the actual throttle position and speed values based on how many rows/columns are in the CSV file and based on a 'max shift table speed' variable, namely just above the fastest speed 1st gear can reach.

A representation of what our table looks like. We haven't set actual values (or shape) yet.



1 indicates first gear, 2 indicates second gear, and 0 indicates keeping the last gear the robot was in to give the table some hysteresis.

We plan on setting up the table for optimal acceleration at high throttle values and energy conservation at low throttle values. Then optimizing the table through testing. As a car guy used to tuning spark and fuel maps like this it seemed like a straight-forward way to do shifting for the robot.

We don't shift while rotating in place.

Comments from you experts who've been doing this for a long time are more than welcome.