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Pan-tilt (tip-tilt) platform for laser distance sensor

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torbjoen

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Hi,

I am looking at **broken link removed**, and I need to control its direction by mounting it on a sort of pan-til platform that I can control from a computer. I also need to be able to read the amount of tip/tilt from the platform.

Preferably it should be able to tip and tilt between 20 and 40 degrees in both directions. And it should be fast and last "forever" ;-)

Can anyone point me to some servos or piezo electric motors that I can use for builing such a platform?

Or better yet, do you know if such platform exists already that I can buy of the shelf?

Thanks!
 
Hi, check out this motor; **broken link removed**

Or this one; 5V MINI LINEAR STEP MOTOR-MPJA, Inc.

It is a linear stepper motor. It and a bipolar stepper driver, would do what you want. They move in 0.001 inch increments and lock in position when you stop driving them. They are very small but fairly powerful. The main body diameter is less than a inch.

If you want I could make a rough sketch of a way you could make up a mount that will do what you need.

Cary
 
Thanks a lot Cary,

Can I read out the position of these types of motors?

It seems like the minimum step angle of one of the motors is 15 degrees. I forgot to mention that I need down to 0.1 degree or even lower - at least when it comes to the step increments for changing the direction of the laser - perhaps the motor can be geared somehow to achieve this.

In https://www.electro-tech-online.com/custompdfs/2009/12/23M014.pdf, there are some charts. I'm not sure which chart to read to know the step rate, but the first chart seems to show that it can provide up to 350+ steps per second, which again means 350 * 15 = 5250 degrees per second, or 5250 / 360 degrees * 60 seconds = 875 rpm. Is this correct, or am I completely mistaking?

If I am correct, the speed of this motor is good, but I need better step resolution.

Also I am worried about the lifetime of a motor that costs 10$ or 15$. How long could I expect such a motor to last assuming that it runs continuously at almost full speed (allthough it will not in reality)?

What about piezo electric motors - would such motors be suited for this kindo of tilt/tip platform? Wishlist: High speed, high accuracy, long lifetime...

If you are able to provide a rough sketch, that would be brilliant!
 
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It seems like the minimum step angle of one of the motors is 15 degrees. I forgot to mention that I need down to 0.1 degree or even lower - at least when it comes to the step increments for changing the direction of the laser - perhaps the motor can be geared somehow to achieve this.
...

I would look into a high quality RC servo. Being analog you can drive them right down to 0.1 degree with ease. You can easily get 2000 steps within 90 degrees rotation, so that is double the resolution you need.

A small spring will remove any gear backlash and since they are internally closed loop you won't need an external sensor, you can just send the control pulse and they turn to where you want.

The Karbonite gear models have very low gear wear and low backlash.

...
Wishlist: High speed, high accuracy, long lifetime...
...

You forgot; Small size, light weight, easy to purchase and of course "low cost". :D
 
torbjoen, even though the step angle is 15* the actual movement of the shaft is 0.002 inch per step. On this type of stepper, the shaft is threaded, but doesn't move. The moving part is inside the motor and is a nut. The shaft stays still and the nut turns inside, moving the shaft in or out, depending on the rotation direction. Kind of like a air or hydraulic cylinder, that works by electricity!

Could you post the dimensions of the unit in inches? Then I'll sketch it up to scale.

Cary
 
Thanks Cary and Happy New Year!

Thank you for your clarifications regarding the step angles. I'm not sure if I understand exactly what you are saying, but what is the actual resolution (in degrees) that I can rotate the motor? In other words, how many angles is the minimum I can rotate it?

The laser distance measure sensor has the following dimensions:

5.35 x 2.24 x 4.09 inches (or 136 x 57 x 104 mm)

I appreciate your efforts and input!

Cheers,
Torbjørn
 
Thank you for your input, Mr RB!

Since I am a complete newbie to servos and motors, would you mind pointing me to a high quality RC servo with Karbonite gear? Thanks!
 
Thanks Cary,
This looks pretty much like what I am looking for, yes. This one is perhaps the closest one: **broken link removed**.

I am a little bit concerned about the fact that it is made out of plastic, since there will be quite a bit of vibrations where my laser distance measurement will be positioned. But I could try this out and in the future perhaps built something similar made out of e.g. steel.

Thanks again!
 
"SPT200 Pan & Tilt System."
At $46 that looks very good value for money with ball bearings, double sided support and metal clamps. You still have the cost of a couple of good servos and maybe 2 springs to remove any backlash.

Which laser distance measure device are you using? I thought they were big and heavy (and expensive!).
 
Thanks Mr RB,

Oh, yes, it is very good value for money, but it is to be used at an industrial site with heavy vibrations, so I would rather pay more for a pan & tilt system made in some kind of metal. Anyway this is a good sart. Regarding the springs, won't they wear out after a relatively short while? I am looking for a "maintenance free" system (as much of the parts as possible)

I am planning to use this laser distance measurement device: **broken link removed**. Yes, it is very expensive, hence I would like to make sure the pan & tilt unit will last even with rough handling. The laser sensor weighs 800g (or 1.76 pounds) which I think the SPT200 can handle (right?).

You mentioned Karbonite gear models. Do you know of any that would interface with the SPT200?

Thanks again for your input!
 
Hi, the servos are available from the same place; **broken link removed**

The way that I was thinking of with the linear stepper would be much more complicated than these. I reread your original post and didn't see that you wanted to stop at different angles. To do that you would need a feedback type sensor to tell what angle it was at.

With the servos that RB suggested the angle is known by the signal to the servo.

The mounts that I linked to are, I think for mounting a camera to a RC airplane or helicopter. They should be strong enough and vibration resistant enough. I would make sure that what ever you chose is rated at least 50% more than the weight of your sensor. That should make it strong enough to last a long time. But I come from the "when in doubt make it stout" school of engineering.

I went back to that site and found these;
**broken link removed**

**broken link removed** They are a little more money than what you picked BUT, they include the servos. Then all you need to add is a controller.

Cary
 
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I am planning to use this laser distance measurement device: **broken link removed**. Yes, it is very expensive, hence I would like to make sure the pan & tilt unit will last even with rough handling. The laser sensor weighs 800g...
...

That's the sort of information that should have been in the first post! (Well, OK, maybe I should have followed your original link and read all the specs...) A laser distance sensor weighing 800g, 5" in size and costing multithousands of dollars, that needs to operate in a harsh vibrating industrial environment?

You are way outside the abilities of a cheap hobby servo pan/tilt bracket!! :eek:

What distance will it be measuring? It has a 350 metre range, even a small amount of vibration is going to cause major misalignment with the target.

You are going to need a large metal pan/tilt device with vibration damping etc etc. It's going to get big and expensive!
 
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That's the sort of information that should have been in the first post! (Well, OK, maybe I should have followed your original link and read all the specs...) A laser distance sensor weighing 800g, 5" in size and costing multithousands of dollars, that needs to operate in a harsh vibrating industrial environment?

You are way outside the abilities of a cheap hobby servo pan/tilt bracket!! :eek:

What distance will it be measuring? It has a 350 metre range, even a small amount of vibration is going to cause major misalignment with the target.

You are going to need a large metal pan/tilt device with vibration damping etc etc. It's going to get big and expensive!

I should have put the weight in the first post (I probably shouldn't expect people to actually look at the links provided, I guess). And yes, I should have mentioned more about the harsh environment. Sorry about that. It will be measuring distances at 50-150 meters, most probably around 100 meters.

Would you happen to know of companies or professionals that would be able to help me design and/or construct such a device?

"It's going to get big and expensive!" --> By big, can you indicate the size needed for accuracy and stability of such a device? (Another fact that should have been mentioned already: I probably need an accuracy of 0.1 degree for the direction of the laser)
 
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I'm not sure how big, it would just be a guess. But as a guess you would need some decent sized gearmotors, some way of getting position feedback (probably optical encoders on the gearmotors) then bearings to support the weight and finally some vibration damping.

It might be best to build the pan/tilt mechanism in a metal frame, then mount the frame with some vibration cushes which you can get from the mech engineering suppliers.
 
Shortbus - These are some remarkable products. I've never seen such reasonably priced pan & tilt systems.
 
An alternative solution maybe ?

Hi,

I've been playing around myself with a similar idea. What I thought would be a better solution was to keep the laser stationary underneath the gimbal then only a mirror needs to be rotated and tilted. This solution requires a gimbal that had a clear line of sight from underneath up to the center of the mirror.
Still this might pose a problem for this type of laser since the emitter and detector are not cocentric. It will work though ,I think, with this one: AR4000 laser rangefinder measures long distances

My idea is to use the more powerful versions of AR4000 with reflectors. It should then work up to 30m-50m I think.
What is clearly a plus with this laser is the sampling rate which goes up to 200kHz! That should make it quite robust against a little shake.
 
Pan Tilt platform

Hi, this may be out of topic, I am looking for something similar but must have a load rating of around 55kg.

Does anyone know where I can get one?

Thanks in advance..
 
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