Servo or ? for Winch/Hoist/Lift Application

Welcome to the forum, and thank you for the detailed question....

Hi SolarEagle.

Thanks! It's nice to be here.

Found this....

http://www.globalspec.com/pdf/viewpdf?partId={D19698C1-335B-4E69-B11B-D5178ACFF734}&comp=49&from=detail&vid=157440

Look under products....MS series servo indexers....click on calculators and sizers

Welcome to CR4 -- when you talk nicely to the members, they talk nicely back and share their wide-ranging knowledge and common-sense approach to problem-solving.

If you're looking for winch suppliers, try http://www.globalspec.com/search/products?page=ms#sqid=11661874&comp=2363 and http://www.globalspec.com/search/products?page=ms#comp=2880&show=products&sqid=11661881.

SolarEagle: I'm getting a 404 error for both of those links. Were they to suppliers of off-the-shelf microprocessor controlled winches?

BestinShow: Thanks for the welcome. I've done some extensive searches for motion control winches and have found some products in the theatrical industry for things like stunts and moving scenery but they are quite expensive and I'd like to look at a DIY design solution before I resort to spending lots of loot. That said, those suppliers seem to use VFD.

I'm still hoping someone can chime in with more information on how servos work and whether they can work as I described with a remote encoder.

Ignore the 404....click on products etc as per instructions above....this leads to calculators for determining size of servo.....and also offers servos and controllers...

Thanks. I'll have a look.

Normally I don't promote any particular business, but in your case I might suggest that you get hold of an Automation Direct catalog (www.automationdirect.com). They sell almost all of the equipment that you will need for your project (PLCs, servo drives and motors, VF drives, encoders, and even the box to put them in and the wire to hook them up) and the nice thing is that the products they sell are compatible! In addition, their catalog is filled with the technical details you will need to chose your components.

And, NO. I don't have any financial connect with them. I just have been using them as a source for many successful automation projects for the past 12 years.

I'll let others more knowing than I speak to the motor/drive type. But I had a similar application in that we needed to track/control the cable speed on an already installed vintage winch-type application (a pull-carriage over-head strip accumulator for an ERW mill)... as cheaply and quickly as possible.

We added a follower arm to the winch that had a sensor that measured wound cable OD at pay-off/take-up point.

First draft worked OK but we had to refine it over time to ignore variances caused by grease clumps, etc.

Just an option to the sheave-mounted sensor which would require remote install from winch; I like to keep my control components as close as possible to what they're controlling.

And, Welcome to CR4!

Hi GringoGreg.
I'll trust your impartiality on that recommendation. :-) At the very least it gives me a place to start with sourcing or even just learning more about motor options and at this point that's very helpful. I'll do as you suggest and check out the information suggested by SolarEagle.
Hi JavaHead. It's always nice to hear someone has solved the problem you are currently facing! Just so I'm clear on the design you went with, the follower arm would have had a wheel encoder of some kind that rode on top of the cable as it spooled off the drum? Grease and other contamination should be pretty minimal in this case.

Not quite. We added some TG&P Shafting across the wench with a slide plate and attached an L-Bracket. One leg of the L had a feed-through hole for the cable and the other end extended over the centerline of the drum to which we mounted an optical/laser displacement sensor. We calculated velocity based on diameter and rpm, then adjusted speed as we passed through different diameter ranges.

Mind you, this was a much larger wench than your application so you have a much tighter window of measurement than we had with the 3/4" diameter wire rope on this particular wench.

For your application, you're more concerned about position as opposed to speed so the best solution for you might be better realized with the provision of a mechanical system diagram.

Most of my work has been in converting, dealing with unwind and rewind rolls where the roll diameter is measured by either a rider arm attached to a potentiometer or an ultrasonic sensor to provide an analog diameter input to the controller. However in the OP's case I agree with him to use an idler and quadriture encoder to measure velocity and position. of the cable. Most PLCs provide high speed encoder inputs for this purpose.

Just as an aside to this and other new members. The quality of our replies is directly related to the quality of the presentation of your question. Good questions receive good replies, great questions receive great replies, thoughtless questions get flogged.

Well I'm pretty thrilled with the thoughtful and useful replies I'm getting.

If anyone who has experience with drives happen to have a look at this thread I'd sure like to hear the voice of experience on whether I'm better off with a servo or some other option here.

To add a little more detail, the payload in this project will be steadied by two vertical static cables strung along either side of it. For example, the winch could be placed at the top of a 100 m cliff and the job is to lower the payload down the face of the cliff. In order to keep the payload from twisting and swaying, it is guided by two static cables, each about 18" to each side of the payload, that are fixed at top and at ground level. The payload has two outriggers that reach out to the guide cables and can run up and down the static cables as the payload is raised and lowered.

So, I'm planning to use 1/4" wire rope for the winch cable. I'd like to use the same for the two static guide cables. My question is about keeping enough tension in the guide cables that they will resist being blown around in windy conditions. How/where would I find out what kind of tension is required in a 100 m cable?

Thanks for the additional info re the application and solution you really need.

What you're describing is vertical tag lines to stabilise a hoisted load....the tension in those guides would need to be a alot, a real lot to provide any sort of guidance but you don't say how much it can flap around or how windy this cliff face is.

On measuring the length of payed out steel rope to determine position, you will have a lot of stretch in that when you have significantly played out some rope and then the stretch varies with load.

If the vertical accuracy is necessary to marry the platform height with a feature on the cliff face then a CCTV camera looking at the face and a VFD driven hoist would get you right on the money with somebody sensible looking at the target on a monitor driving the hoist.

This reply implies that you will be outdoors with this device. This brings up the question of your power supply. Will you have AC power available? This may not be a problem as a DC gear motor may be the most economical solution an either case.

A couple other points:

• Did you include the weight of the cable in your calculations. 100 meters of 1/4" cable is significant.
• This will be an "overhauling" load. That is, the load will try to drive the motor. So, a means of breaking and holding the load must be provided, either mechanically or electrically.

Worm drive prevents self spooling. Motor in and motor out.

Brake is still good to have in case of catastrophic gearbox failure.....

Welcome to the forum Vanbot and good luck on your project. As you have some of the finest minds helping you and I can not add to their great info I will bow out gracefully.And again Welcome! to the forum.

Hi LOCKDUKE and thanks. I am already enjoying the experience and knowledge on display here and especially the willingness to share those things with someone like me who is learning on the fly. Before I found this forum I had tried posting on a couple other forums and got very little interest or participation. What happens here is much more in line with my idea of active, curious minds enjoying a bit of a challenge and community effort.

gringogreg: AC power is available (this is not a very remote cliff!) although the motors I've looked at so far are all in the 210-240 V range and I had hoped some 110-120 V options would be available. Maybe something suitable will come up once I start chatting with suppliers.

Wal: Hi and thanks for your input. I did take into account a wire rope weight of ~18 kg. The actual payload is 22 kg. I had considered the change in length of the wire rope due to temperature change but hadn't thought about stretch until you mentioned it. I'm wondering if the control program can include inputs for air temp and can automatically correct for stretch, i.e. as the value for "how much cable is out" increases, the program will automatically compensate for the relevant stretch. Did I mention this will be an automated winch? :-) It will be possible for someone to help correct for position manually via a camera since the payload includes a camera anyway, but the hope is that this winch will run automatically after some initial user input.

I had been thinking of using a worm gear since the payload will spend most of its time descending and the inherent braking provided by a worm gear would reduce wear on the motor.

I will firstly confess that I have absolutely no experience with what you are attempting, but from what I have read so far, I am wondering if a simple rolling counter at the winch to measure the length of cable paid out or retrieved would work.

Stretch could conceivably cause compounding errors but as you have surveillance, that could be corrected, and fail safe switching to prevent inadvertent over-run at either end should not be difficult.

If the payload is simply being transported between two fixed points, then maybe simple limit switching with due consideration of over-run would suffice. Positional accuracy may or may not matter??

As for the tension required on the guys, I guess it depends on the sail area of the load as to what effect any prevailing breeze has on it, increased distance from the cliff face may make that a non issue as a bit of lateral movement may not then matter.

That's my bit, if it helps - good, if it doesn't - well I did warn you.

If you need to descend to a pre benchmarked position (you suggested cable length) you could directly measure the distance to the platform with a laser ranging instrument (like surveyors use) with a digital output. No moving parts and very exact.

With a VFD drive you could even have a braking sequence and then slow inching to desired level dependent on the distance data feedback in your automation.

Stabilisation will be a challenge. It won't be qty2 1/4" steel rope guitar strings.

This is a very bespoke bit of rigging you are proposing...what you really upto?

Seems to me it would be easier to just use a steel structure that would eliminate any movement and tracking location could be precise by design....being able to support the structure from the top as well as the bottom, and possibly at midstructure would minimize weight and size requirements compared to a stand alone structure...

A properly designed and fixed 100m tower would solve the movement issue.

1st things first. What is your pay 25 kg load? Gold? Why would ut require expensive parts to lift? Whats your lifting elevation? Encoder would do the trick, if this all mechanical and vfd, proximity level switches would do rather than encoder

I don't see a problem using an external encoder attached to your pulley. By selecting the resolution (PPR) you can have as much accuracy as you want.

I am also curious what you are doing.

Good luck.

Hi Spades. Yes that was a useful comment. At this point they're all useful so fire away! The plan is to use limit switches on the payload sled that will be tripped by stoppers of some kind at the upper and lower extents of the guys to tell the winch when top or bottom has been reached. Sail effect should be pretty minimal as the payload is compact and dense (although sadly it's not gold Kulas) although I'm still a little antsy about turbulence around the cliff face causing oscillation.

Wal:

• As I understand it, a VFD or servo should be programmable enough to allow the payload to inch towards each stopping position. Can you confirm that or are you guessing like I am?
• I'm really interested in the laser idea. As long as it wasn't limited by bad weather, i.e. rain or mist, then it could work very well to give position and velocity. It could also be an anti-over-run backup to the limit switches. I will look into that option for sure. Another potential problem could be oscillation in the payload. Whether the laser was mounted on the payload itself or at the top of the cliff, if it requires the beam hit a target reflector or receiver, that could be compromised by movement of the payload.
• I could use larger guys if that would help significantly with stability.The 1/4" wire rope was an initial guess at the lightest option that would work and be tension-able by hand winches. Would I get substantial gains in guy stiffness by increasing the guy diameter a notch or two?
• I can't spill all the beans about the project yet. It's something I'm doing to help a friend who needs it as a tool for a research project he's involved in. He's even less of a engineer than I am so right now I'm his "expert". I feel like I'm writing a serial suspense story in a magazine. Now the pressure is on to keep you guys entertained and guessing! :-)

SolarEagle: Unfortunately the whole rig needs to be person-portable so a tower won't do the trick. It will be set up in one position for a period of time then shifted laterally to the next position.

Hi Kulas: Sorry to say, no the payload's not gold. Lol. For now the planned max elevation is ~110 m.

Hi lyn. Thanks for your input. The encoder wheel is an attractive option and could easily be the first one we go with to get this thing built although Wal's suggestion of a laser range finder would, as long as it works in an outdoor environment with wet weather, instantly solve problems such as correcting for stretch in the winch cable to determine actual vertical position.

• As I understand it, a VFD or servo should be programmable enough to allow the payload to inch towards each stopping position. Can you confirm that or are you guessing like I am?
• Not guessing. You also have a large reduction gearbox on your hoist. Think "elevators"....
• I'm really interested in the laser idea. As long as it wasn't limited by bad weather, i.e. rain or mist, then it could work very well to give position and velocity. It could also be an anti-over-run backup to the limit switches. I will look into that option for sure. Another potential problem could be oscillation in the payload. Whether the laser was mounted on the payload itself or at the top of the cliff, if it requires the beam hit a target reflector or receiver, that could be compromised by movement of the payload.
• The target can be whatever is on the end of your hoist rope, eg the cargo deck. Don't need a special steady reflector. just a big flat patch of surface. Rain or mist..don't know.The top and bottom limit switches can all be mounted at the top. Max lift is a knob fixed to the rope near the hook end that opens a switch, Max down is a limit switch on the drum that opens when you get close to running out of cable....like a construction hoist.
  
• I could use larger guys if that would help significantly with stability.The 1/4" wire rope was an initial guess at the lightest option that would work and be tension-able by hand winches. Would I get substantial gains in guy stiffness by increasing the guy diameter a notch or two?
• (much)Bigger guys can be stretched tighter and will be stiffer. Consider a third guy. Your guys are really guides but I know what you mean. You can use a hand winch (come along) at the bottom, a tirfor would be better. You could use one as your hoist too.
  
• I can't spill all the beans about the project yet. It's something I'm doing to help a friend who needs it as a tool for a research project he's involved in. He's even less of a engineer than I am so right now I'm his "expert". I feel like I'm writing a serial suspense story in a magazine. Now the pressure is on to keep you guys entertained and guessing! :-)
• Not too much guessing and games of 100 questions please. It gets hard.

How about active stability control like window cleaners use when hanging off their BMUs. Ducted, vectorable air thrusters (fans)?

Stability control on a BMU is done through a wide stance on the supports and Quick Release Pins inserted into sockets that are permanently installed in the side of the building. A BMU or Swing Stage is going to be no more than 3' - 4' from the exterior.

And NO.... There is no BMU that has ducted fan stabilizers or Vector control. That would be an Aircraft!

Too bad. I really wanted to see a photo of a BMU with propellers. I think it'd take a lot of juice to move a big swing stage around with a prop.

Or maybe something like this!!!

The only reason to be over the side of a cliff that I could think of would be to go fossil hunting like they do here in Indiana.

Wal:

• Not guessing. You also have a large reduction gearbox on your hoist. Think "elevators"....
• Bingo. Hoisting with relatively accurate positioning and a steady guided payload. All this time I've been thinking "crane" but I think you nailed it with "elevator" Wal. If only there was a community of obsessive 1/10 scale elevator enthusiasts out there to help out with this!
• The target can be whatever is on the end of your hoist rope, eg the cargo deck. Don't need a special steady reflector. just a big flat patch of surface. Rain or mist..don't know.The top and bottom limit switches can all be mounted at the top. Max lift is a knob fixed to the rope near the hook end that opens a switch, Max down is a limit switch on the drum that opens when you get close to running out of cable....like a construction hoist.
  
• The laser rangefinder is sounding more and more promising. I'll see if I can get some info on how well they function in wet conditions. Also, need a range of ~110 m in those conditions.
• (much)Bigger guys can be stretched tighter and will be stiffer. Consider a third guy. Your guys are really guides but I know what you mean. You can use a hand winch (come along) at the bottom, a tirfor would be better. You could use one as your hoist too.
• I used to work on maintaining and erecting (and repo-ing) tension fabric structures and used Tirfors a lot. I actually hope I don't need THAT much tension to get decent performance from the guides. The plan is to set up a portable jib crane of sorts at the summit to support the guide wires. In order to support their weight and provide enough of an anchor to tension against it'll be necessary to either drive anchors into the ground or, where the ground isn't cooperative, use copious counterweight on the back end. In either case a Tirfor could easily yank out anchors and dump counterweights off the back end of the jib. So increasing the size of the guide wires to, for example, 3/8" wouldn't really improve stiffness just because they're heavier? It would be more of a function of being able to apply much more tension with a larger guide wire?
• Not too much guessing and games of 100 questions please. It gets hard.
• I hear you. I'll check with the boss and see if I can divulge a little more.
• How about active stability control like window cleaners use when hanging off their BMUs. Ducted, vectorable air thrusters (fans)?
• This was something I'd wondered about. I like to play with quadcopters and there is some pretty powerful open source flight control software out there that could be adapted to maintaining stability on a platform like this. It is adding weight, complexity and power draw though. I did some searching for this kind of thing being used on BMU's and got nothing but results for BMW stability control. Lol. Have you seen it used on window cleaning platforms?

Now that you bring up elevators, why not forget the winch and use a counterweight system. This would drastically reduce the torque required for the drive motor and simplify the control system.

Replacing the cable with a chain and driven sprocket you may be able to use a stepping motor

I found this page which gives some good basic info on laser range finders. Unfortunately there's no option to view it all on one page so you have to do some clicking to get through it all:

http://www.opticsplanet.com/howto/how-to-guide-laser-rangefinder-features.html

I'm sure it's light (haha) reading to most of you but for a layman like me it helped put things quickly into focus (haha...sorry).

As expected, rain, mist and snow can be a problem and the article discusses overall accuracy of a few inches (for high end models) to a meter or so in good conditions. Whereas, with the encoder wheel I wanted accuracy of a half inch or so because compounded error over 100 m could get out of hand, with a LRF something like the .25 m this one offers could work since there wouldn't be any compounding of error. Except for on rainy days when all bets could be off. Hmmm...maybe I'm back to loving the encoder wheel.

http://www.lightware.co.za/shop/en/laser-rangefinders/38-sf30c.html

OK, sorry had to go AFT (away from thread) for a bit. But, now that I've caught up to a more developed thread - a couple things - brought on by military experience:

For your elevation issue, and taking into consideration both weather concerns and the desired portability of the system - what about a Dytter? Not really sure where the term came from but it's an audio altimeter we have in our helmet. (HALO Jumper).

Pretty sure that exact type will be of little use in this instance but there are all types of altimeters out there for different applications and they have all types of built-in logs (jump records) and transmission features. And I'm assuming they have some pretty high-speed ones in aeronautical craft. The question is, will they provide enough precision for your application?

As for the stabilization, drawing on first-hand rappelling experience, yes currents along a cliff face can be both turbulent and unpredictable. Can your load be domed, (i.e. smooth and symmetrical)? This would minimize spin tendency as compared to something that is irregularly-shaped with surfaces for the wind to catch against.

NO not a range finder like that.

I meant more like this http://ptd.leica-geosystems.com/en/Leica-DISTO-D510_102636.htm

Surely +/-1mm will be good enough?

Regular builder's tool these days.

Not just +/- 1 mm but +/- 1 mm with 200 m range. Now THAT'S a laser rangefinder. Lol Yep that could work. I like that Bluetooth interface too.

gringogreg: A counterweight to reduce power requirement sounds pretty awesome but a 100 m chain sounds, in my admittedly limited experience, somehow difficult to manage. Wouldn't it be possible to do the same thing with wire rope and a nice grippy sheave? The only potential complication I'm seeing is that we already have three lengths of wire rope extending up to 100 m and this would involve more dangling wire rope with an object at each end in an application where there might be vegetation that this all has to be threaded through. And that might not turn out to be a complication at all and just my anxiety talking.

Javahead: At your suggestion I've started looking at altimeters but have so far found none that have the accuracy I'd need. I think you're right that some consideration should be given to the shape of the payload to minimize it being blown around. And from previous investigations I've done (i.e. looking it up on Wikipedia) into aero drag caused by various shapes, your sphere suggestion is on point. And there shouldn't be any problem making it spherical...it'll just have a couple of outriggers tacked on.

I have an Idea that will provide a counterweight and add additional stability. Think endless loop with sheaves top and bottom and a tensioning device. I will provide a sketch later today when I have time.

Sounds good. Looking forward to seeing it.

Hi gringogreg.
I'm still interested to see this idea of yours if you think it could be helpful.

This, apparently is the world's oldest elevator

They do not appear to be stabilised by anything other than the wall behind them.

This place

Where are you?

If you are in a city where one might find a glass enclosed passenger lift then go for a ride and consciously observe how it is working. The hoisting will be different but take careful note of the guide rails....you have to mimic that function.

Another thought regarding your guides...instead of a pair of large single steel ropes you could have multiple runs (a bundle) of your 1/4" acting as a larger rope.

I your outriggers are long tubes instead of rings then this will help too.

I've found on most jobs that access is usually a big hurdle. Is the top and bottom of this cliff face road vehicle accessible? You're gonna be carting a bit of gear.

I'm in beautiful, wet Vancouver, BC. :-)

A quick off topic here...I haven't seen all the details on that German airliner that went down but it seems odd that the route it took varied so much from the route it was supposed to take. It was supposed to stay over land the whole time heading NNE from Spain into France but instead took more of a ENE heading so that it was well over the Mediterranean the whole time. Not to start any conspiracy theories but does anyone know how common it is for commercial jets to deviate that much from expected flightpath? I thought they had strict lanes they're supposed to stick to. Anyone heard if communications between the plane and air traffic control was normal?

Anyway, back to "work". There is vehicle access to the bottom of the cliff and most of the way up the back of it but there is still a stretch of (good) trail up which this equipment will have to be humped by hand so there is motivation to keep the weight down. And the heavier the hung weight of all the cable + payload, the more weight must be carried in just to counterbalance it.

Just to give an idea of the type of hoist I'm considering. Sorry that it's more a cartoon than a diagram.

How about using a block and tackle for the winch line? If it was attached without any kind of swivel or joint to the hoist and the payload, it would add some weight but could it also act to counter twisting. Maybe that with one outrigger on a guide line could work?

OK, so we have a device we use in the military for accessing areas via unintended means and the closest thing I could find civilian-wise on the interwebs is:

http://www.liftingsafety.co.uk/product/deadweight-anchor-2641.html

Obviously would need modified to meet your need and mount your wench, but the counter weights are smaller plates that can be individually distributed across the Platoon or Squad. In your case, it would just be multiple trips ;-)

That's very cool! Very Special Ops. Yes the idea would have to be modified to work on uneven ground as well. There's also the cantilever effect of the boom extending over the edge. That will produce some lifting force that will reduce friction between weights ad ground. But still very interesting. In fact that company also makes this:

http://www.liftingsafety.co.uk/product/tractel-portafix-3496.html

I think my buddy could easily get a couple of hand carts of some kind to move a lot of this equipment around.

I think I have an answer to my original question, i.e. servo or ?

A local motor supplier here tells me that for a simple application like this where braking can be accomplished by using a worm gear, we can save some money by using a regular old AC motor with VFD. There are all kinds of existing winch software modules that work with these drives so one of those should be pretty suitable for this application.

So I can tell you all a little more about the job this is meant for. It's being used to survey populations of a bird species that nests on cliffs. Mostly this is done through rope access but the idea here is to keep humans out of it and that the birds can hopefully acclimatize to having a machine around watching them.