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Trick and Trail VESC Package

by Mike Silberstein (send questions, comments, requests to [email protected])

1. What Is Trick and Trail Package?
2. How is Trick and Trail Package different?
3. How does this affect the ride
4. What does this package not have?

What Is Trick and Trail Package?

Trick and Trail Package was developed based on Float Package 1.2 by Surfdado and Niko. It departs from the traditional PID control scheme that is rooted in the balance robot design. This is replaced with a user defined, current output curve that is based on board pitch. This allows for an infinite number of throttle/braking curves that gives the user the ability to truly tune the board how they want. In addition, there are modifiers for roll, surge, and traction control to provide the best possible performance for the nastiest tricks and the dirtiest trails.

Features

• Current output defined by a user input curve, instead of PID factors, allowing for ultimate control over the board performance.
• Roll kp curves for acceleration and braking. Modifies current output based on increasing roll of the board to carve as hard as you want.
• Roll kp modification for low speeds for better maneuverability and 180's.
• Surge similar to the Onewheel XR that gives the board a boost of power when the nose dips quickly. Allows for smooth and tight curb nudges.
• Traction control to handle the loosest, rockiest trails. Reduces wheel spin while in the air and tire bite when landing. Affords an opportunity to recover when you lose traction in a big way.
• Sticky tilt allows the user to set persistent board angles with a remote.

How is Trick and Trail Package different?

The primary innovation in the Trick and Trail Package is the throttle and brake control. In Balance and Float Packages we see that the throttle and braking control is governed by a PID loop. PID stands for proportional, differential, and integral and these factors apply to the board angle and cycle time to determine the current output. In general, boards that feel unstable have high differential and integral factors. These factors are time related so that the more time the board spends at a certain pitch angle, the more impact these factors have on the output of the motor. The feeling they create is generally referred to as "trottery", after the Chinese knock off, the trotter.

As Float package has evolved Surdado has been able to remove the trottery feeling by removing the differential factor, reducing/limiting the integral factor, and depending largely on the proportional factor for current output. This allows for a predictable current output with minimal overshoot. However, it is limited in that it only has proportional and integral factors as the primary controls (although there are many other factors you can play with).

The solution that Trick and Trail implements can be considered to be multiple proportional factors and no integral or differential factors. Instead the user decides specifically what current they want at what pitch angle. For example, we can say at 1 degree we would like 20 A output. This would be equivalent to a proportional kp of 20. If that was the only point we defined this would feel just like Float package with Angle P 20 and I of 0. But we have 6 points we can define. So instead let's define 1 degree of pitch as 10A and 2 degrees of pitch as 40A. That means from 0 to 1 degrees we will have a kp of 10A/1=10. Then from 1 to 2 degrees our kp will linearly scale from 10 to 20 (40A/2). Then above 2 degrees it will continue with a kp of 20 so that 3 degrees gives us 20 * 3 = 60A.

How does this affect the ride?

This creates a much smoother ride. For trail riding having a high proportional factor is beneficial to keep the nose and the tail off the ground. But having a single high proportional factor like 25 can make the board feel jerky when going over objects and landing tricks. This is because the board is sensitive at low pitch angles. To solve this we can potentially lower the proportional factor and increase the integral factor to make the board a bit looser. However, adding the integral factor introduces the time related instability and that trottery feeling.

Instead we would like to have two or more proportional factors, one lower factor at low pitch angles and a higher factor for high pitch angles. This will make it smooth at low angles without sacrificing clearance when current demand is high on uphill and downhills. Additionally, a low current demand at low angles makes it easier to prevent wheel spin while in the air. Typically you want to keep the board level and current demand minimal so the speed of the wheel is consistent with the speed of the ground when you land. Finally, this adds a unique feeling to the acceleration/braking transition so that it feels easier and more natural to set your center of mass before the board starts reacting harder.

What does this package not have?

While many features from Float Package are include some are not. Here are those I chose to not include and why:

• All tune modifiers and ATR (except constant tiltback). The main reason is that automatic tiltback is not good for tricks. When the board changes setpoints while the wheel is in the air, it is hard to know how the board will react when it lands. Remote tiltback is superior for doing tricks while trail riding.
• Darkride. It's cool but it is a lot of code to maintain for something that has minimal practical function.
• Magic Flywheel. Again, very cool, but not super useful.
• I term and I filter
• Reverse Stop
• App Quicksave. Perhaps in the future.