Auto Level Surface

Good luck, sounds quite a challenge, especially achieving a decent reaction time.

Using gravity (gimbals) has the advantage of simplicity but perhaps disadvantages of weight and space.

You might try using some mercury switches mounted underneath the table to activate the levelers.

Be aware that the motor mounts and linkages will determine whether you have 2 DOF or 3 DOF. You can check out links to Stewart platforms to see how this works.

You also may need to worry about stiffness.

Tom

Hi Balraj,

Does your unit look something like this?

Oops, I put pneumatic cylinders instead of stepper motors but the principle's the same. I don't know the dynamics but I think this system is workable. The pivot's in the wrong place (it's supposed to be just underneath the center of the table) but I'm a little lazy to redraw it. You get the idea anyway, I hope.

I am sorry for not posting a picture

To have precise tilt angle measurement, you need a gyro positioner, transmitter.

The signal will be output through a Fuzzy logic controller to the Servo motor.

tijit

Okay, my idea wasn't quite accurate but similar, in a way.

I've reread your post. What were you asking about? You just asked for support without specifying what kind of support you needed.

Barry Controls and others make pneumatic, self leveling, vibration isolation tables used primarily for isolation of optical systems. Design specifics depend on the amplitude and frequency you need to isolate to. Generally, they can isolate down to low numbers of hz and can provide output levels of a few mili Gs throughout the entire spectrum of noise inputs. The design you show will not isolate through the center leg, unless it also is a pneumatic cylinder or some type of compliant member.

This is how naval radar arrays are mounted, the ones you see spinning around at the top of the superstructure. The antenna stay level whilst the ship pitches & yaws around in the ocean. The stabilised gimbal mounts use stepper motors & gyroscopic detectors to maintain stability.

Are you a yachtsman or similar? Is that the reason for building the table in the first place?

You say "the platform of the table will be tilted by +/- 5 cm," but you don't say that the +/- 5 cm is measured at the edge, for example. In the 12" dimension, 5 cm translates to a larger angle than it does in the 18" dimension, if the 5 cm is measured at the edge. (By the way, thanks for mixing units of linear measure.)

It is possible to use two devices called a LOHET (Linear Hall Effect Transducer) to measure two dimensions of motion and directly control servo motors as a function of distance off-level. The output of the LOHET is a function of the strength of the magnetic field it is subjected to. A rigidly attached arm extending down from the bottom of the plate with two or four LOHETS or permanent magnets free to move between two or four permanent magnets or LOHETS rigidly attached to the bottom plate extending upwards will produce the position feedback necessary to control servo motors.

Of course, there are other ways to do the same thing.

Go to Newport.com. Look at "Smart Tables." They have exactly what you want.

-Robert Pettis

I allready checked that website long time ago, but that is vibration isolation. I am dealing with low frequency only between 1 to 5 hz. I will be using linear actuator and servo motor to keep it balanace. If you could help me finding linear actuator with servo motor for cheap plrice that would be good. Actuator should be able to lift 5Kg, it should have stroke of 12-14cm. I will be using Lab view to control it as well as memes INclinometer.

I'm curios why don't you use gyro stabilization ...im not being smart I'm really asking ...

X-Y Auto level platform:

As a sensor for your leveling mechanism you can use 2 gyroscopic artificial horizons, mounted perpendicular to each other. This will only be feasible if a very high degree of accuracy is needed. You can use two auto pilot general aviation type artificial horizons, they already have the outputs you need. you can get a good used one for $300.00 to $700.00.(calibrated)

A more rudimentary solution is to use capacitive level indicator. that is, 2 perpendicular horizontal levels such as construction level, with two conductive rings wrapped around each end of the liquid tubes at the level markers. Tilting of the level will vary the capacity between the links. You know what to do with this variation.

A third possible solution is to use Mercury switches, and so on.

Telling us what exactly you want to do with your table, might bring some more ideas? however, I hope this helps.

Wangito.