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Suspension adjustment of an "off-road" robot

Hi,

I'm working on a project named ALR2 (autonomous long range rover), based on a 1/10 scale off-road RC car (traxxas e-maxx) and I would like your opinion on how to ajust its suspension in order to carry robotic payload. I've came up with my own way of doing it, but I'm still open to other solutions that may be easier or more efficient.

The goal is to have the rover carry the required payload at reasonable speeds (about 10 mph) over rough terrain with a good suspension dampening These [electric] cars have individual suspension for each wheel (actually two shocks per wheel), but the problem is that they come adjusted for racing, not for carrying payload. In order to carry my stuff around (cpu, batteries, sensors, microcontrollers, etc - estimated worst case of 8Kg) I need to adjust the suspension by replacing the springs and shock oil. I already have a set of springs and oil of different thickness.

I came up with an idea on how to test which setup is more appropriate without having to devise complicated mathematical models for each one of the shocks.

Here's what I'm doing: I've installed 3 LEDs on my rover of different colors. All three leds are pointed to one side of the rover. LED 1 is positioned in the front, LED 2 in the rear and LED3 on the camera platform (that is 6 inches higher than the rest of the rover). In my garage, I've put a few obstacles of different sizes in the rover's path, and then at night I use a 35mm camera to take a picture of the rover going through the obstacles. I open the shutter before the rover starts going through the obstacles and close it after the rover went through the bumps. (I was a professional photographer, so photo technical details are under my domain).

The result is a picture with 3 line on it. Well, if the surface is flat and acceleration/braking isn't too heavy (causing the nose to go up under accel or the front to dive on braking), then the two LEDs positioned on the rover base will overlap.

I guess it works (I've already took a series of pictures with the rover without load), the goal is to find one suspension setting that under desired load, produces a picture where LED lines are more or less straight.

The drawback of this method is that I'm comparing suspension settings on a very limited scenario (artificial bumps on a 15ft route), do you think this would be enough? Any other ideas?

I'll post some pictures somewhere after I finish my testing.

Padu

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Reply to
Padu
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Hi,

tilt sensor would let you know if robot is tilting.

shocks: oil filled, have reservoir. Put a valve between reservoir that you can control. The more closed the valve, the harder to push oil through it. Stiffer shock. Open the valve farther, oil travels through it more easily, softer shock.

____ | |__ | | /\ /\ /|___ |___ | | | \/ \/ |

The spring on the "shock absorber" of that RC car is mounted between two fixed plastic "bumbers". The tires/arms are hinged. You could remove the top bumber, replace it with a threaded nut. Run a threaded rod through it. By threading the rod farther through it, you put more compression on shock, making it "stiffer". back the threaded rod out, you make it "softer".

Put a geared motor attached to the threaded rod, and you can vary the ammount of compression with your computer.

just ideas.

Rich

Reply to
aiiadict

This is a nice idea to make a dynamic adjustable suspension system, but in my previous post I was more interested in how to find out the optimum adjustment (read optimum set of spring/oil thickness) performing simple tests. I don't want to install sensors and creating code just to find out what is the best suspension setting.

The modern RC car shocks are already threaded, so you have this adjustment possibility. Additionally, there are 2 (or 3, don't remember) spots where you could fix your shock to the wheel arm at differnt angles, giving you another place to control how soft or stiff the suspension gets.

Yes, good idea for an "active" suspension system. If I come out with something like this, I could easily turn it into a project of its own and sell it to RC car racers... these guys are crazy about "modding" their little RC cars and they would be crazy to brag about their "F1 like active suspension system" :-)

As you see, there are a number of different ways to adjust the suspension, and I'm going to have only one static setting at the end. I just want to know of a method to find out what is the "best" setting for my application.

Thanks

Padu

Reply to
Padu

Try setting enough spring to keep the ride height at optimal, then expirement with different silicone oils in your shocks.

You will sant the softest spring you can get away with.

application.

Reply to
blueeyedpop

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