Speed control by pedal force or movement?

[Gymnast]

When the F16 fighter jet came to use in the 1970s, it had a control stick using force instead of movement. The control was all by electronics anyway, and electronics was not trusted that much before the F16. The development guys found out, that the ergonomics of force control is better than "movement control". This issue is discussed in this link:

https://aviation.stackexchange.com/questions/32280/do-we-fly-full-size-aircraft-with-video-game-style-joysticks/32281

I think most sewing machines still use a pedal, where the speed is controled by the pressed down position of the pedal. I did found one reference from a report made in Portogal regarding use of force for control:

https://repositorium.sdum.uminho.pt/bitstream/1822/14917/1/PaperPresserFootDraftPostRefereeing.pdf;Automatic

I do not know if any commercial products have adapted these findings.

I did some electronics for control of my domestic sewing machine using air pressure from pressing a piece of wood against a silicon tube. So an electronic air pressure sensor is in use. In this way you achieve food force control. I like it, and I find the control better than my alternative normal sewing machine pedals. Please see attached picture.

Actually I am not sure, if the servo motors do have movement control og force control - what do you think? When I look at this video, the control arm do have some movement:

https://www.youtube.com/watch?v=VOTFolRZw-4 

[Wizcrafts]

On all the servo motors I have and have had, the speed increases with movement on the control lever, not the force applied to the lever. The lever is held back by a spring that is just strong enough to let it return to the off position when the floor pedal is released. I don't know how many micro-ergs of force are involved in moving these levers, but it can be done by hand if a foot is unavailable.

[Gymnast]

20 minutes ago, Wizcrafts said:

On all the servo motors I have and have had, the speed increases with movement on the control lever, not the force applied to the lever. The lever is held back by a spring that is just strong enough to let it return to the off position when the floor pedal is released. I don't know how many micro-ergs of force are involved in moving these levers, but it can be done by hand if a foot is unavailable.

Thanks for the reply Wiz. I think most leatherworkers would like to have force control instead, but they have never tried it yet.  Hopefully one day, a servo motor manufacturer will provide this option. Actually i should think, that the manufacturing cost of force control should be less and be more reliable.

[nylonRigging]

2 hours ago, Gymnast said:

Thanks for the reply Wiz. I think most leatherworkers would like to have force control instead, but they have never tried it yet.  Hopefully one day, a servo motor manufacturer will provide this option. Actually i should think, that the manufacturing cost of force control should be less and be more reliable.

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Good luck on making a better machine speed control . ( There is not much in between ) . as far as control .
You either use your physical 'Feel' with push/pull with hands-feet for spring-lever on clutch or servo motor .
Or, it just swings to the total opposite end using little physical Feel of input by your using just a little 'Tap' of the foot or finger for activating a On/Off switch for pneumatic solenoid switch or inboard attached servo motor and electronic board, or your running CNC program, multi-directional free motion stitching .

I still pretty far behind 21st century Tech. and my most complicated control is a Bartack with 'ancient technology' Pneumatic/solenoid press-foot lift and stitch cycle  . All my other machines are Muscle pushing a spring-lever, with two of them still being old clutch motors .
Small custom design like here on this board with leather will always hang on the end with the most invested in muscle memory with an eye on every stitch and pushing a spring-lever with a foot or hand for machine control and speed .
You need to build a cheep-$ robot instead of a better switch . My Ass gets sore sitting on a stool behind machines for hours, Personally I want a A.I. Robot that podcasts my favorite listening, that will do all my sewing for me ....LOL
.

[Wizcrafts]

3 hours ago, Gymnast said:

Thanks for the reply Wiz. I think most leatherworkers would like to have force control instead, but they have never tried it yet.  Hopefully one day, a servo motor manufacturer will provide this option. Actually i should think, that the manufacturing cost of force control should be less and be more reliable.

Perhaps, if you knew where these motors are designed and manufactured, your expectations would become less theoretical and more along the lines of: "Thank God when I pull the lever down - the motor turns faster the farther I pull it and it doesn't explode."

As for any thought you have about bugging the builders of the popular servo motors, we don't need another Sew Pro 500GR incident. Buyers and dealers complained about case warping problems that came from a redesign of their motor. They chose to close the company rather than fix the problem.

[dikman]

7 hours ago, Gymnast said:

 I think most leatherworkers would like to have force control instead

I'm not sure how you've reached this conclusion, given that it's unlikely very few have actually used such a system to comment on it. The good thing about a pedal/linkage system is that it's easy to adjust so that you can have either minimal travel or longer travel to actuate the motor (or engage the clutch in the case of clutch motors). I suspect that most are quite happy with this system. Personally, I can't see too many (if any) manufacturers being interested in designing/implementing such a system. Why would they want to?

[Gymnast]

I think the key issue here is how the sensors in the human body works. It is the ergonomics. It is somewhat explained in my first link. You can very well feel and control how much pressure, that you apply to something by your fingers, hand or food. You can hardly feel the position of your fingers, hand or food. That is why force control is better than movement control.

I think, that the first pilots in the F16 had some reservations to a new way on handling the control surfaces of the plane. I think pilots will be the most critical people regarding their ability to control an aircraft safely. So why do designers new fighter aircrafts and Commercial jets make force activated stics with no movement. They could easely make some movement on such sticks for the electronics, but they dont. It is because the pilots likes them too.

I will give you that much, that producers of aircraft have put millions of dollers in the design of these control stics. Designers of servo motors do not have this kind of money. However sensors of force has becomes more cheep and reliable in the past 20 years. Every smartphone have them in order to sense the elevation. Three force sensors in the phone with a small mass on them finds the direction of gravity in relation to the phone position.

Actually I think that most well designed servo motors will have one or more springs applied to the control arm. In this way a higher force is needed to move the arm towards maximum speed. In this way you will have some force control anyway.

On clutch motors the control by the pedal to the speed is purely mechanical. On servo motors you need to have an Electronic signal to control the speed. It can be achieved by a force sensor or by a sensor of position or angle.

[mikesc]

You are waaay over thinking this..all you have to do to get a pressure or force sensitive speed control pedal, is to put a small air filled ball, such a a child's foot ball, or an air-filled "softball" or "handball ball" ( under the front end of the pedal that is pulling on the pitman rod ) ..the more you squash the ball by pressing down on the pedal, the harder it gets to squash the ball ( it is "harder" , requires more force, to "compress" air that is already being compressed* ) this solution can be "retro-fitted" to any sewing machine that does not use a rheostat in the pedal..Actually it can even be used on one of those, but requires opening the pedal, fitting a smaller ( air-filled ) ball, inside the pedal, and closing up the pedal again..

Voila !!

I did this as soon as I got my first industrial machine, many decades ago ( works also under the pedal on clutch machines ) ..and on all subsequent machines ( servo or clutch ) ..with the exception of "treadle" machines, such as most patchers..But you are unlikely to want to run a patcher faster than one stitch ( each stitch exactly where you need it ) at a time..If you switch the treadle mechanism on a patcher to a servo mechanism, then you could apply it..

Child's air-filled vinyl ball ( small enough to wedge under the pedal of an industrial machine ) will cost you no more than a few dollars..

Just don't try and patent the idea in any way..I have "prior art" ;-)

*Physics..which apparently they do not teach enough of nowadays..

Edited April 17, 2019 by mikesc

[Gymnast]

It seems to me like a great idea, mikesc  Hopefully other people can benefit from your finding.

Now you got some theoretical links to back your story.

[tofu]

8 hours ago, Gymnast said:

I think the key issue here is how the sensors in the human body works. It is the ergonomics. It is somewhat explained in my first link. You can very well feel and control how much pressure, that you apply to something by your fingers, hand or food. You can hardly feel the position of your fingers, hand or food. That is why force control is better than movement control.

I don't know about you, but I can certainly feel, with accuracy, what angle my foot/ankle is in. It would be pretty difficult and dangerous to drive otherwise.

 

I also imagine it would be pretty difficult to shoot if you can "hardly feel the position of your fingers, hand..."

[DonInReno]

On 4/17/2019 at 3:49 AM, Gymnast said:

So why do designers new fighter aircrafts and Commercial jets make force activated stics with no movement. They could easely make some movement on such sticks for the electronics, but they dont.

Um...99.99% of all speed/volume controls use some movement - it works.

[Gymnast]

I just discovered, that the Swiss sewing machine manufacturer, Elna have used air foot control for some years:

https://www.sewingpartsonline.com/air-foot-control-elna-436410-20.aspx

They marketed this inovation in the early 1980s.

I think than my version on the thread start picture is cheaper

[Gymnast]

I have tried to measure force and displacement of an ordinary foot pedal and the force controlled pedal I got. The measurement results are in the diagram below. For the force measurements, I used a digital kitchen weight.

I have tried only a couple of industrial sewing machines, so i am not so sure about the normal pedal behavior of them, so I hope you can help me with your experience. I suppose you got a industrial sewing machine with a servo motor on it.

When you press down the speed pedal with your foot, then first you need to apply some force before the pedal starts to move downwords. You need to overcome a spring pulling up the pedal to a stop. In the diagram you should look at the red dashed line, and for this pedal it starts to move with a pressure of 10 N or about 1 kg. When you press down further then the pedal moves downwords. At about 15 N force the machine starts to turn. In the diagram below it is when the pedal have moved about 3 mm down. When you press further down the force needed increase and the speed increase. At some position you reach max speed of the machine. This is at about 43 N force and 28 mm displacement on pedal. However it is possible to press the pedal further down, but the max speed is maintained. At some position the pedal go against a stop, and it do not move further even if you press harder with your foot.

Apart from the numbers - is this text an accurate technical description on how your pedal work?

Do you think the numbers for your machine is much different?

[Constabulary]

Sorry to say that but for "just operating a sewing machine" this is a bit too much science for me. Pedal down force? Really? For what? Honestly I do dot care and I´m not event trying to follow all this. But as we say in German "Jedem Tierchen sein Pläsierchen"  Good luck with this!

[DonInReno]

Everyone has a different preference for length of movement, force required, and how fast the force increases.  Personally I like 2”-3” of movement and very light constant pressure on what is essentially an automotive pedal.   

[sheathmaker]

Boy, if I have ever seen a solution looking for a problem, this is a classic example.  Force, movement,....who cares?  I just want my machine to sew correctly when I turn it on and to start and stop when I say Go and Whoa.  Now before anyone gets their feelings hurt, the foregoing is just my personal opinion and is not intended to sway anyone one way or the other, or criticize others for their opinions.  I'm a believer in the old "If it ani't broke, don't try to fix it" camp and my Cobra machines have been (with servo motors)  sewing just dandy since I brought them into the shop.  Good luck!

 

Paul

Edited October 23, 2019 by sheathmaker