Program FrSky X-20S for Droid Tank Drive

[@HoboJard]

Thanks Tim for the video, this really helps those who have to look up multiple videos.

[@GunnerAl9]

Thank you for sharing this. I was hoping you would have demonstrated the difference in movement between the normal R2D2 Droid Movement and the tank movement. Not 100% sure of what the difference is and how it appearance on the droid. I'm new to the droid channel mixing and I have my R2 set up for movement so I'm apprehensive to try and re-program to tank mode.

[@TheEebel]

Tank mode is just the nomenclature of this style of mixing. It’s also called arcade style. If your R2 is driving fine, there is no need to change anything. This video was made to get someone new to RC to a drivable state. I searched all of the internet trying to figure out how to do a mix like this for my first RC droid and there was not a video for it. This video, hopefully, fills that gap.

[@TrollandError]

It's not about a difference in the droid's movement so much as a difference in how you get those movements from the radio. Tank mixing lets you combine the horizontal and vertical axes of a single gimbal in such a way that it can control both of the tracks (or wheels) freeing up the second stick for other purposes. This way, left/right on that stick rotates/steers the droid, and up/down moves it forward and reverse. The alternative control scheme is typically to use the vertical axis of the left stick to control the left track, and the vertical axis of the right stick for the right-hand track. With this method, you've simply moved the tank mixing off of the radio and into your brain. The main (only?) advantage of this second control scheme is that it's a bit more straightforward to implement ... each stick controls one motor directly. The downside is that separating the droid's movement inputs from each other like that can be sub-optimal, especially when your droid has other multi-axis inputs that should logically be grouped together and/or suggest use of a gimbal's vertical axis. For example, consider the droid in my profile pic, LD-F1. In addition to the tank drive, he can both nod his head front-back and tilt it left-right (he can also look to either side, but I use a potentiometer for that). Intuition suggests using a vertical axis for nodding and a horizontal axis for tilting, ideally on the same stick. I can easily do that with the gimbal left free by in-radio tank mixing. On the second control scheme, I'd be forced to not only split LD-F1's locomotion onto two different sticks, I'd also have to split his head motion as well, and I'd have to control the front-back nodding motion by moving one of those stick left-right. It doesn't make sense from a puppeteering standpoint. It can also be weird to control. Say I'm turning him, driving the right track forward by moving the right stick up ... but I accidentally nudge the stick a bit to one side. Suddenly, his head is also either tilting or nodding, depending which stick I mapped those to. Putting a bit of deadband on the sticks (so slight deflections away from the center of each axis won't trigger that axis to move) can mitigate that, but it's best to avoid the issue altogether by grouping related functions on one stick.

[@GunnerAl9]

@@TrollandError Excellent explanation. I cut and pasted your explanation into my "Notebook" for programming for future reference. Thanks again. Easily understood what you provided.

[@TrollandError]

@@GunnerAl9 I should also note that some control systems don't necessarily even have two sticks to use with that second control setup. SHADOW, for example, can be used to drive a droid with only one single-stick PS3 Nav controller (you can also use two of them though). Tank mixing would be required for this setup, and would have to be programmed into the code running on the Arduino or whatever. When I did my first build (Artie Deco from Hardware Wars), SHADOW didn't have built-in tank mixing. It relied on the Sabertooth motor controllers to do the tank mixing for you. Since Artie uses regular R/C speed controllers that don't do that, I ended up having to code the tank mixing formula into it myself.