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Perseverance Rover Replica Challenge!


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On 8/6/2020 at 7:28 AM, vyznev said:

So, after thinking about this a little, I decided to try building a rover with a working rocker-bogie suspension as a proof of concept:

VRPAB59.png

It's all built with BG robotics parts, no stock wheels. The only powered parts are the wheel rotors and the two servos at the front used for steering. (I believe Perseverance uses four wheel steering, but I was lazy and only made two of the six wheel steerable for this test rover.)

The real secret ingredient is the unpowered servo at the back of the rover body and the two grip pads attached to it, highlighted in the screenshot above. The grip pads have same-vessel interactions turned on, as do the four pads on the suspension that they're sandwiched between. What this simple mechanism does is implement the rocker part of the rocker-bogie suspension: it holds the pitch of the rover body at the average of the pitches of the two upper suspension arms on either side of it, thus allowing the body to match the approximate tilt of the terrain below it, even when said terrain is highly uneven:

NpTgRPu.png

Craft file here: https://pastebin.com/LV6crxNq

Nice, I sorta gave up on a working system because of the pitch issue you fixed. I like it!

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On 8/6/2020 at 5:28 PM, vyznev said:

The real secret ingredient is the unpowered servo at the back of the rover body and the two grip pads attached to it, highlighted in the screenshot above. The grip pads have same-vessel interactions turned on, as do the four pads on the suspension that they're sandwiched between. What this simple mechanism does is implement the rocker part of the rocker-bogie suspension: it holds the pitch of the rover body at the average of the pitches of the two upper suspension arms on either side of it, thus allowing the body to match the approximate tilt of the terrain below it, even when said terrain is highly uneven.

Here's the same principle applied to an actual replica (minus a bunch of bells and whistles equipment and science instruments):

LoOJF2r.png

As you can see, it's not quite there yet as far as looks are concerned. But all the mechanically important parts work. :)

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  • 2 weeks later...
On 8/6/2020 at 4:28 PM, vyznev said:

So, after thinking about this a little, I decided to try building a rover with a working rocker-bogie suspension as a proof of concept:

@vyznev I tried to use this method of making a rocker-bogie suspension on one of my rovers (not a Perseverance replica, but maybe I'll build a Perseverance rover later) after I saw your post but I encountered a problem: I left my rover on the Mun and when I loaded it again the suspension was... some sort of broken. Am I doing something wrong?

Edit: Loading a quicksave doesn't help

Spoiler

AMTKlpI.png

rover.exe has stopped working

 

Edited by s_gamer101
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4 hours ago, s_gamer101 said:

 

  Reveal hidden contents

AMTKlpI.png

rover.exe has stopped working

 

I've had something similar happen too. Apparently the grip pads can sometimes slip or glitch past each other. :/

You might be able to fix it by manually turning off same vessel interactions for one set of pads so that the servo can rotate freely, and then try to jiggle it back into place. Then just re-enable same vessel interactions on the pads to lock them back together.

Come to think of it, it might be a good idea to make the servo motored and just have the motor disengaged by default. That way, if it glitches, you could turn off same vessel interactions, engage the motor and just rotate it back into position.

Edited by vyznev
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I managed to fix it manually now, but thanks for your support.:D It seemed like same vessel interaction was disabled on one side when the rover was loaded, which is probably a glitch since I‘m quite sure that it was turned on on both sides when I left the rover.

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On 8/8/2020 at 12:42 AM, vyznev said:

Here's the same principle applied to an actual replica (minus a bunch of bells and whistles equipment and science instruments):

Spoiler

 

LoOJF2r.png

 

As you can see, it's not quite there yet as far as looks are concerned. But all the mechanically important parts work. :)

I finally had some time to add some bells and whistles.

X1FC54W.png

UM3YUr1.png

Not all of the detail is entirely realistic; I went more for a general sense of "looks good from a distance", adding parts where there should be parts and clutter where there should be clutter. Also, some of the colors are off due to stock KSP part limitations. That said, some of the added parts are even functional: the RTG is an RTG, the radiators are radiators (not that you need them in KSP), the UHF and low-gain antennas are actual antennas (albeit retracted, so they don't actually work; there's a working antenna pretending to be part of the rocker mechanism, though) and the scanner arm is obviously a standard Breaking Ground light scanner arm (the medium one was just a little too big to fit comfortably). BTW, careful viewers may note the the front part of the rover is actually flipped left-to-right — that's because the BG scanner arm is a mirror image of the real one on Perseverance, and putting it upside down just didn't feel right. The camera assembly on the mast rotates and tilts, although there's no actual camera there.

Also, I spent way too long fiddling with the underside of the rover that nobody's ever going to look at. :P The second scanner arm under the rover body is supposed to represent the sample storage and analysis robot. And yes, there's an actual science container there, roughly where it should be. (The sample collection wheel is represented by the tilted OKTO2 probe core on the top front of the rover — that was the closest thing I could find in KSP.)

Spoiler

fVEMn19.png

Anyway, it still works and can climb over obstacles. Including some mountains. :cool:

Spoiler

 

CZTtz6g.png

xFsHBEy.png

NwOQx7I.png

 

I still need to make some final tweaks to it, though. For example, I really should add a hotkey to toggle the wheel direction so I can make it go in reverse too. :) 

Also, while looking at pictures of Perseverance, I realized that I could've really easily included a realistic mechanism to fold the wheels up during flight just like in real life just by adding one more servo to the suspension. But adding that servo now would require taking the whole suspension apart, and I really don't feel like doing that. :P 

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