Team Solid-state

[GAHD]

1. In this thread I will discuss the design, and hopefully construction of an entirely solid-state lunar rover.
   
2. The first few posts will be reserved for future editing to include links to related reference material.
   
3. The only posts permitted in this thread will be those pertaining to the subject at hand, any superfluous posts will be deleted with impunity.
   
4. critiques are welcomed, but preferably should include a suggested work-around.
   
5. This rover must comply with all specifications outlined in the x-prise thread

The basic concept of this rover relies extensively on magnetic forces. A more complete description will follow.

[GAHD]

1. magnetic levitation primer
   
2. Bismuth - strong diamagnetic, Mass Susceptibility (10-6 c.g.s. units) -280.1 (Molar?)
   
3. electric motor - the foundation of the wheel
   
4. stepper motor - what makes it turn?
   
5. coils - the crux of solid-state; antennas and induction
   
6. Inverter
   
7. Magneto statics - how does it all bleed together?
   
8. microwave power transmission
   
9. Reserved

[GAHD]

Schematic upload.

 

Mainly detailing basic layout, most major components left in "black box" form.

[Turtle]

1. magnetic levitation primer
   
2. Bismuth - strong diamagnetic
   
3. electric motor - the foundation of the wheel
   
4. coils - the crux of solid-state; antennas and induction
   
5. Reserved

 

batteries of course and inverter(s) to change the DC delivered by the batteries into AC for use by the induction devices. :hihi:

[Jay-qu]

I asked a question in the other thread but will put it here in a more broad sense because it relates to the rover design.

 

How will thermal expansion be coped with?

[Roadam]

If the goal is no mechanically connected parts, then thermal expansion is not a problem, right? At least for motor, bearings and wheels. No precise enginering of course. :hihi: The "black box" would of course have to be thermally controlled.

[GAHD]

thermal expansion /contraction will hopefully be of minimal importance to this design, but that's what prototyping for, right?

 

 

This is rough sketch of my initial wheel/motor design.

 

Legend:

1. A solid hemisphere of a diamagnetic material, approximately 1/4 from the equator there is a band of inset permanent magnets oriented so like poles are facing each other.
   
2. As #1, but with a hole at it's pole to allow a mounting strut to pass through
   
3. A spherical casing containing a relatively strong permanent magnet, and 16 individually switched electromagnets.
   

 

#1 and #2 are of equal diameter, #3 is scaled to be significantly larger than the hole at the pole of #2, but smaller than the internal diameter of #1 & #2. All coils are to be secured in a solid material(such as epoxy) to prevent unwanted movement. Once system is verified to work correctly the hemispheres will be permanently welded together preventing #3 from escaping.

 

The general idea is that the diamagnetic field created by the wheel casing in reaction to the large permanent magnet be sufficient to levitate 1/4-1/2 the total weight of the rover.

 

Expansion of various materials to be tested, and proper spacing tolerances apllied (such as a 1/32" gap around the inset magnets, total size of the spheres also taking these variances into account, internal filling materials being spongy enough to expand and contract in a predictable manner).

 

16 isn't a number I'm set on for the number of coils and inset magnets, it just happens to be a number easily divisible by binary computing systems and spaced around a circular pattern.

 

The as-yet mostly undetailed main-body design I've tentatively listed as cylindrical. The idea being that such a design allows us to wind an antenna and induction coil along it's length, have cameras mounted on either side, and to use th batteries themselves as a small insulating layer and heat-sink for the primary components.

 

Turning will be handled tank-style with each wheel or set of wheels rotating at a different speed, or even direction. hemispherical wheels are also not something I'm set on, my initial sketches having fairly standard pie-plate wheel designs.

 

more after work(which I'm already late for...)

[Jay-qu]

Hmm I see how you mean you want to make the rover 'levitate' within these hemispheres, but how is it that they will rotate and propel the little bugger?

 

I think this design may need to much power to be properly realised under the conditions we want - but the moon is 1/6g so would need considerably less power than here on earth.

[GAHD]

they move via the same principles of a standard electric motor: the coils in #3 create a local disturbance in the overall magnetic field created by the central magnet(primary source of levitating force). Overall the idea is to be a stepper motor

[Roadam]

So one motor for each wheel?

[GAHD]

Each wheel *IS* a motor, yes. The idea being you can alternate between FWD, RWD, 4WD, or even 1WD allowing a wide range of traction and power saving (and possibly recuperation) options.

[Turtle]

Each wheel *IS* a motor, yes. The idea being you can alternate between FWD, RWD, 4WD, or even 1WD allowing a wide range of traction and power saving (and possibly recuperation) options.

 

Yes; as well as steering by varying wheel rpms side-to-side as in a bulldozer or tank.

[Roadam]

There may be a little problem with magnets: most moondust is feromagnetic.

Maybe it is not so good idea to put batteries around outer side of the central part becouse they too require minimal temperature when drained and even higher when recharged.

[MITH]

Hey GAHD,

 

have you taken into consideration the magnetism (and thereby attraction) of the dust particles (caused by ferromagnetism) as indicated in the primary thread?

 

Theoretically the wheel in a non operating mode could possibly avoid attracting particles if all particles share a similar charge and the "baseline" of the wheel was the same, however once you induced the stepper function you would have numerous particles attempting to reach the opposing force, thus contaminating your wheel. Perhaps the use of a magnetic field as a barrier of some sort would suffice but it would have to be passive or once power cut in a failure or temporary shutdown the particles could still be attracted by any remaining charge. Just wondering....

 

MITH

[MITH]

Another quick thought. If moon dust shares a similar charge throughout (to be assumed or it'd be a big clump any time it was kicked up), then couldn't a principal of levitation be used ala hoverboard as opposed to any physical connection with the ground? A floating rover could be pretty cool (steering could be an issue).

[GAHD]

magnetic Hoverboarding would require quite a powerful field, I don't see it happening on the moon any more than I do on earth.

 

I forsee h epossibility of dust getting in, but I doubt it will interfere what with there being a large, open space in between. I'm ASSuming that particles the size of smoke won't interfere with a space many orders of magnitude larger than they are in between #1/2&3.

[MITH]

individual particles may not, however the concern is of build up as well as the interference caused when said build up occurs.

 

Recent experimentation with the <10 mm fraction of mature hi-Ti mare soil 79221 has shown that a small hand magnet will easily attract practically all the grains, even those that are plagioclase.

 

 

Travel over 500m will allow quite a bit of particles to be attracted from the surface. This is why I brought up the factor of incorporating a repulsive field at the openings to ensure no particles would become stuck inside.