Low cost Gyro stabilization

What are you trying to track with the telescope? If it is stars, an equatorial clock drive, oriented to earth axis, will do this without gyroscopes. If it is animals in the woods, that's a bit unpredictable, but gyroscopes are likely to be even less helpful.

However, if you are tracking the sky from a moving vehicle, a gyroscopic baseline might help to keep a gimballed carriage oriented properly.

Tornado, This is not a tracking system. I am not looking to match the Sidereal rate. I know how to do that.

What I am trying to do is create a vibration free mount that is stable without mass and while lacking the rigidity normally associated with conventional mounts.

L.J.

Sorry if I misread the original intention. Here is a motor that might be suited to your application, at a nice price from the HarborModels Website. I forget what happens with two (or three?) perpendicular gyros. It looks as though they would fit into your envelope, but the total amp draw might require some cooling provisions. The wheels would surely need to be very precisely balanced. Now that I see the picture better, I hope you keep us posted on this project.

	Graupner Motors Speed 400 Highly efficient, small motor for medium-sized boats. 1" x 1", 2.3 mm shaft, 3.6-8.4V Specification: Shaft 2.3mm Length, excl shaft 1.5" Case diameter 1" No load RPM: 16400		GR1794 $11.95
		Motor Mount Speed 400 Motor	GR1794.2 $4.95

Thanks Tornado. I recognized some of the characteristics so I went to HobbyLobby and a few other RC modeler sites and found that whole family of motors. What is funny is that I already buy a lot of components from them for use in the secondary cells of telescopes. I do so because of the weight.

I am hoping that when the motor is running and the flywheel up to speed, the start up loads that draw the amps will settle down. This looks like a high torque unit so it should be well suited to bringing the fly wheel up to speed form a dead stop.

Thanks

L.J.

Tornado, your earlier response suggests an interest in astronomy. Are you perhaps a closet ATM?

L.J.

Years ago I took an introductory college class in astronomy, and have read a few articles from time to time, but not a deep interest. More recently I have thought about 2:1 geared down clock drives for solar reflector tracking (in relation to Gaiatechnician's solar cooker threads). That's why I noticed your OP.

If there is still an interest and you have need for a low cost ($5.00!) device that tracks the Sidereal Rate precisely, then I invite you to go to an appliance store, Radio Shack, Home Depot, etc, and pickup a geared appliance timer. The motors are synchronous (60 CPS) and match the Sidereal Rate precisely.

I've used them for many years to power the polar axis on small scopes with great results. A slight mod to a 12 VDC inverter, allows me to vary the 12 VDC output frequency for even better resolution. You need only put a friction coupler on the polar shaft.

Where are you located: in the Northern or Southern Hemisphere?

L.J.

OOPS!

I wrote: "A slight mod to a 12 VDC inverter, allows me to vary the 12 VDC output frequency"

I should have written "A slight mod to a 12 VDC inverter, allows me to vary the 12 VAC output frequency".

L.J.

Hi, I'm astronomer. If the system must be not expensive you can realize by yourself the gyro using the configuration you mentioned. Of course you risk to pump in vibrations if the rotating masses are not perfectly balanced. At any rate the best solution is to use DC motors that can reach very huighj rotating speed. You have to provide by yourself to the system optimization. It is the best and cheaper solution. Of course the gyro must be fixed to the tripod interface to the tube and not to the tube itself. The motors you can use are very very cheap and I suggest to left the masses rotating during observation and run the motors pnly during pointing or when the angular speed of the masses is going down. You launch them and then they are free and noiseless. If you need to take pictures with a camera you can balance the acqusition time with the masses speed. When you disconnect the motors you reduce the noise due to the commutation of the motor collector. I hope some of that can help you. Dario

Laughing Jaguar,

You need to state the minimum magnification that will suffice. MEMS gyros are used in modern digital cameras to electronically steady the images. Also I believe that Minolta or Nikon make binoculars with image stabilization. In these devices, adjustable angle prisms are servo driven to compensate the angular motion detected by MEMS gyros. I believe that the steady binoculars have been available in the $400 range for several years. If you require higher power than 20X, you may have to roll your own. Do not try to use large mechanical gyros because they will precess from your movement i.e. a sideways angular shake would just cause additional vertical angular motion. It works in ships, but is not good for hand held optics. Stable camera platforms used in TV helicoptors measure the angular motion using gyros with tight feedback loops that drive dual axis servo motors to reduce the motion. These cost thousands of dollars.

I hope this helps. Freescale.com and NXP have MEMs acceleration and gyro sensors which are typical of the state of art available.

Luther M

The dynamics of a low cost gyro stabilizer will make it unsuitable for any work with telescopes. It is doubtful if a meaningful response time can be achieved, especially at high magnifications.

Hi L.J.,

interesting project, some specs needed to suggest solutions.

Stabilised mount: any direction (3 axis) or horizontal (2axis) platform?

Long term stabilisation quality: degrees random drift within 1 minute, 1hour, 1 day, 1 year, whatever is applicable.

Angular vibration: how much is allowed at which frequencies? Motors make big vibration sources.

Passive or active stabilisation?

The Binoculars mentioned above are two different classes: one class has a prism that is mounted on a flexure thus stabilising for seconds (the hand and vehicle) but not longer.

The other class has three gyros (one axis) or 2 gyros 2 axis to actively stabilise with 3 servo loops if 3 axis operation is necessary.

Modern airplanes have virtual platforms: 3 gyros strapped down to the aircraft frame together with 3 accelerometers- without the gimbal system used in former times.

The gyros measure in 1ms time intervals the angles (roll, pitch, yaw) that the craft has moved and updates the memory where the orientation data are stored. So at any time the aircraft orientation is known and can be calculated with respect to any other coordinate system.

Any other orientation (camera or gun) is then servo-slaved to this orientation with some deviation introduced to fulfill required mission.

In the aircraft system the angular movements are resolved (also in 1 ms time increments) to the inertial directions of Earth, Sun or whatever else.

The outputs of the three accelerometers are recalculated to give outputs with respect to the inertial 3 axis system. Next these acceleration signals are integrated to give velocity, once more to give position. 1 nautical mile circular error probability is typical since 30 to 40 years and requires gyros of 0.01°/h random drift specification.

Coming back to your system: how accurate, which time for observation or taking photos? How to re-orientate to a new direction? Any "stabilised platform" included in your 15lbs? Only pointing of your scope necessary or rotation (around line of sight) to be stabilised too?

RHABE

(I worked for 7 years full time and 7 more years as a consultant to ANSCHUETZ, KIEL, Germany, then a Carl Zeiss company, later sold, now Raytheon-Marine)

You might take a look at the Steadicam range for inspiration. They have been making stabilised camera mounts for 30 years for film and TV cameras and now even for the iPhone. They are the industry standard in this field; pricey but very effective. web: www.steadicam.com. ( I am having trouble seeing some of their pages but there are ways around the front page via news to get to their product range.)

I appreciate the generosity of ideas as well as the sophistication of some of the solutions. However, many of them demand that I engage in a protracted learning curve before I can conjure up a design. Electronics are not my forte. I have been a machine designer for many years so I am inclined to explore a mechanical solution.

The prospect of success with a gyro stabilized system was first explored using a pair of discarded 12,000 rpm hard drives. Remarkable how effective they were given the crude experiment. The experience I gained isolating vibrations from cooling fans for mirrors also proved valuable.

Most of the instability that occurs manifests itself when focusing the instrument at magnifications in excess of 125x. There isn't sufficient hysteresis in most optical system to dampen the vibrations quickly.

The success of using hard drives suggests that an increase in the mass of the gyro or its speed, might be all that is needed. With high torque motors in the 7.8 to 12 VDC range and no load speeds in excess of 16,000 rpm, I suspect that I need only fabricate a low friction mount for the flywheel to keep the reactive loads from damaging the motor. Most of the motors I've investigated only have 3mm shafts and are not designed to withstand such loads. There appear to be no commutators in any of themotors considered thus far (permanent magnets only).

I do want to use rate sensors, solid state circuits or anything more complex than a simple gyroscope. However, many of these motors are multiphase devices which do require a microprocessor. I am trying to avoid those too. They push the material costs into the low 3 digit range. Still affordable but already outside the envelope I'd hoped for.

Thanks for the support.

L.J.

LJ,

Look into HobbyKing.com for pm motors,brushless, with electronic speed controls, ESC, and model radio control helicopter gyros. If you need roll, pitch, and yaw the cost for 3 gyros and 3 servos will be just under $100 USD before shipping. Part #'s HK 401B digital heading lock gyro and Turnigy MG930 servos cost each 13.99 USD. You will have to build the platform and tune the gyro outputs to build a stable platform. For an extra $10 you can have three axis remote aiming using the 555 timer circuit and three pots- google (555 circuit drives radio control servos) or just go to: www.horrorseek.com/home/.../svoint_RCServos.html . This approach will not compete with the long term stability of expensive camera platforms, but it may work over short time periods. Some soldering is required, but no programming or MPU's required. Good counter balance will reduce the servo loading and the current drain of the servo motors. I would not advise the use of rotating mechanical gyros, for 3 axis pointing, it will be a nightmare of gyros precessing and stimulating each other through mechanical resonances-my advise do not go there.

Good luck

Luther M

Being an astronomer and telescope maker for over 40 years I feel this will never work.

High magnification is super critical on vibrations.

a gyroscope no matter how well balanced at high magnifications will destroy the image. even something as small and low mass as a 12 vdec muffin fan can destroy a high magnification image on a monunt that weighs hundreds of pounds.

even a truck driving by 500 feet away sets up enough vibrations in the earth itself to ruin a highy power image.

NSS wrote: "Being an astronomer and telescope maker for over 40 years I feel this will never work."

Having worked in engineering departments and designed complex machines for over 40 years I believe it will.

I have 15 telescope designs to my credit as well.

Nothing peaks my interest to attack a problem like someone telling me it ". . . this will never work."

Thanks for extra jolt of motivation.

L.J.

I need a 2 axis low cost stabilization platform to automatically level a machine while cutting limbs from trees with outputs to drive hydraulic valves to 4 hydraulic cylinders.

Hey Jim,

The MEMs 3-axis accelerometer integrated circuits are now available in tiny packages as small as 3x3x0.9 mm. Similar sensors are produced by several semiconductor manufacturers in the US southwest and Boston areas and also overseas. I will refer to one made by Freescale Electronics which spun off from Motorola several years ago. All you need is to find which way is "down". The logical way to do this with an accelerometer 3 axis chip is to mount the chip so that every axis on the chip is 45 degrees off axis when the platform is level. This is done so that the gain of each of the 3 sensors is the same. The Freescale part number is MMA7660FC for a part that has +_ 1.5 g spans, and you can download the data sheet at the sensors page from www.freescale.com. I will leave the details for actuating the solenoid valves to you, but the vendor's app notes should get you there with a minimum of fuss. You will also need one 8-bit MPU. A pure mechanical solution is available using a weighted bob and sensitive "micro-switches". You should use double piloted detented spool valves with a center off position to control three double-acting hydraulic cylinders, but the MPU and acceleratometer is far more rugged and dialing in the sensitivity and hysteresis needed to quiet the motion when the platform is plumb will be easier and more accurate with the accelerometer sensors. You can use a servo valve if you want a "live" zero position for your platform, but this level of accuracy is probably not required.

Luther M

Hi Luther!

The application you suggested is a bit too complex for me to implement without a significant investment of time. While I understood much of what you wrote, the technology is too intimidating to one who's specialty is mechanical design.

I have since discovered that a pair of computer hard drives secured to the head of the optical system, provides the necessary stabilization to offer the vibration free environment needed.

Coupled with a motorized focuser, the system is now disturbance free.

Thank you for the effort and support.

L.J.

Going through Old E Mails, and was wondering what ever became of this?

Joe

I've been thinking about the same thing to help stabilize my large astronomy binoculars. I found this and would appreciate a comment from an engineer please.

https://www.gyroscope.com/d.asp?product=SUPER2

look into RC (remote control) solid state giro for Helicopter, Drone ore other

another option is Arduino components light programmable and cheap

to my knowledge, the last one could be the most flexible

"look into RC (remote control) solid state giro for Helicopter, Drone ore other

another option is Arduino components light programmable and cheap

to my knowledge, the last one could be the most flexible"

I looked into these things and found them to be either cheap and inadequate or very expensive and complex. I'm thinking this https://www.gyroscope.com/basket.asp is worth a try for $107.00. I have a really good portable car battery starter that has ac outlets. If I can mount the gyroscope on the top of my binoculars, it should work. There are several videos showing this gyroscope in action and I think that mounting it in this position may work. Please give me your thoughts on whether or not this may work. The video shows a hand puting a rod into the gyroscope and making it rotate, but I would position the gyro straight up or perpendicular to the top of my binoculars to spin without any rotation involved. https://www.youtube.com/watch?v=OgT-tE6R4JE&list=PLcLePN0VJPzcDtVYhX_Nu7NBstISNTNvc&index=4

Again, please give me your thoughts.