# Maintaining Level AND HEIGHT

Picture a three wheeled cart with a platform on top. As the cart moves along uneven terrain, three ball screws with stepper motors control overall platform height and keep the platform level. Note, if the leveling system is set and the cart travels down a slope, the platform would lift relative to the cart (and sea level) until the ball screws max out their length.

Perhaps this is the best way to describe it: Many bird species readily display their natural ability to stabilize their heads, but - YouTube

I have a LSM9DS0 9 DOF Adafruit breakout wired to my Arduino but noticed none of the outputs really measured height. I’ve seen barometers used to determine height but they are not precise enough for my project.

Any help would be appreciated!

You have to compute the vertical distance from the starting point. The description of the device seems to be telling you that.

ALL height is relative. State the precision you require.

Paul

Adafruit TOF distance sensor. There's also a longer distance model.

dougp:
Adafruit TOF distance sensor. There's also a longer distance model.

A very interesting device. It would give the OP the distance above ground, but since he was discussing a barometer and relating that to height, I was supposing he wanted altitude. Who knows????

Paul

Use a camera to identify an external object or collection of objects, and move the platform to stabilize the object in the image.

Many people have used this idea and the Arduino-compatible Pixy camera to track colored blobs or laser pointers.

Paul_KD7HB:
You have to compute the vertical distance from the starting point. The description of the device seems to be telling you that.

ALL height is relative. State the precision you require.

Paul

Thanks for the replies!

Yes, there would be a set point before the cart would begin traveling. The problem I'm having is I see no data that actually represents height. Roll, pitch, and yaw don't really measure height.

Precision wise, +/- a mm would be great so the barometer wouldn't work.

I like the camera idea. I've thought about tracking a laser, too. Hmmm.

Are you trying to maintain height or level? The bird's head was maintaining position. Very little height change.

Hi,
Why do you need to know height above sea-level?

Tom..

MikeLittle:
Are you trying to maintain height or level? The bird's head was maintaining position. Very little height change.

I'm trying to maintain height and level. The birds head was stationary is relation to its body.

TomGeorge:
Hi,
Why do you need to know height above sea-level?

Tom…

I’m not actually interested in height from sea level. I was trying to convey the need to stay at a consistent height as if traveling along a carpenter’s level when the bubbles are within the hash marks (horizontally level). Since the ground is rare level (or smooth) the distance of the platform to the ground would be adjusted to maintain the platform at the same level.

Ok, so I am going to be real dumb here.

What type of ground are you traveling over? Open fields, blacktop, brush?
How does it move? Is it on rails, tires, track, what?
Is there some kind of suspension system on the cart? You said keeping it +/- 1 mm. Bouncing along on the ground will throw that out the window.
How fast are you traveling? How fast to you need to respond?
How much height are you expecting to be able to compensate for? Screws only come so long.

MikeLittle:
Ok, so I am going to be real dumb here.

What type of ground are you traveling over? Open fields, blacktop, brush?
How does it move? Is it on rails, tires, track, what?
Is there some kind of suspension system on the cart? You said keeping it +/- 1 mm. Bouncing along on the ground will throw that out the window.
How fast are you traveling? How fast to you need to respond?
How much height are you expecting to be able to compensate for? Screws only come so long.

Traveling over mostly grass.
On tires, probably about the side of a hand truck (dolly).
No suspension.
Very slow travel. Approximately, 10 seconds per foot. So, I don't expect any bouncing.
Height compensation will be max 36 inches.

A few other questions:

Are you transmitting or receiving something from the top of the platform?
Are you traveling in a straight line, and if so, how will you know?
How fast do you need to correct height?

Could you use something similar to what survey teams use (or even heavy construction equipment) and sense a laser? If you go above or below the target spot, move the platform.

Why are you still avoiding the question of where you are measuring the height from?

MikeLittle:
A few other questions:

Are you transmitting or receiving something from the top of the platform?
Are you traveling in a straight line, and if so, how will you know?
How fast do you need to correct height?

Could you use something similar to what survey teams use (or even heavy construction equipment) and sense a laser? If you go above or below the target spot, move the platform.

No transmitting or receiving from the platform.
Generally traveling in a straight line but precision is not important.
Height correction needs to be fast. 500ms or less.
Laser guidance could work really well but would involve placing a laser away from the cart, yes? It would be nice to have everything on the cart. Also, I suspect laser system would cost more.

Delta_G:
Why are you still avoiding the question of where you are measuring the height from?

I'm not avoiding, it's not just relevant. Height will be arbitrarily set. The only thing that is important is that height is maintained.

BenjaminPQ:
I'm not avoiding, it's not just relevant. Height will be arbitrarily set. The only thing that is important is that height is maintained.

No, you don't understand the question. Height involves two points. You want a constant height relative to WHAT? Do you want it to stay the same height from the ground? DO you want it to stay the same height from some reference point at the point where it started? If the cart goes down a hill does the platform raise up or does it maintain its height from the ground?

You keep just saying that it needs to keep the same height. But height is a meaningless quantity if you haven't defined the two ends of it. If I ask you how high is that hill, you can't answer because you don't know if I want height from sea level, the bottom of the hill, or where we are standing now, or even some other reference point.

That's what you need to define. The height from where. What height.

Why do I suspect that this project will never go anywhere?

Delta_G:
No, you don't understand the question. Height involves two points. You want a constant height relative to WHAT? Do you want it to stay the same height from the ground? DO you want it to stay the same height from some reference point at the point where it started? If the cart goes down a hill does the platform raise up or does it maintain its height from the ground?

You keep just saying that it needs to keep the same height. But height is a meaningless quantity if you haven't defined the two ends of it. If I ask you how high is that hill, you can't answer because you don't know if I want height from sea level, the bottom of the hill, or where we are standing now, or even some other reference point.

That's what you need to define. The height from where. What height.

Ahh, I see. The height will be selected based on a structure that the cart will run along the side of. The structure is already level (no, it can't be used to guide the platform). Since the structure is level you could also call that height from sea level, I suppose.

How high is it? There are proximity sensors you could use but the choice will depend on the distance you need to measure.

But really, if the track is level and the cart runs along it then how would the height of the cart ever change? Sounds like it is running along a level surface.