Not sure if this would add something helpful to the OP but, for some time, I was an avid reader of catalogs listing hundreds of voice coil motors. I got the concept that the definition (?) of their movement is as fine as your electronic control could be. The other concept: going higher in power, price goes high quickly.

Every time the actuators subject comes, I recall Firgelli.

Isn't the OP saying that bypassing all the control stuff, he got a clear response?

Thank you atferrari! Yes. A very clear response.
Amidst learning of all these things I don't know, it is good to remember that the stick jumped aggressively when I shorted the coil. I'm on to something.

Firgelli. What a resource. Wow, thank you. Currently there is a linear actuator from amazon, designed for solar tracking, controlling the tilt angle of the shooting platform. Choosing an actuator from Firgelli will be an easy upgrade.

I see voice coil stuff as the specialization of how just one coil performs. I got nervous hearing about "digital signal processing" and "adding sine" and whatnot, but I have to remember that I don't want complex control of one coil. I want much simpler control of multiple coils. And, according to your comment, this should be cheap... good stuff. thank you.

 

See, I thought you needed to use a solenoid, coils or linear type motor. Why not a stepper motor with a pinion gear mounted on the shaft. This pinion would mate with a rack gear. Then by the number of steps being taken from ball contact(the zero point, like in a CNC mill) the number of steps backward could be programed and the number of steps forward of zero could also be programed. The rack would be tipped on both ends by a cue segment, like used in a two piece cue, to mimic a "human" using one with the motor and rack area mimicking the 'bridge' hand of a human. By using a zero point, step limits and speed of movement for stroke, all of the normal computations that a human does when making a shot are also able to be programed into the robots movements.

...and I would be able to use all of the existing algorithms for rotational stepper motor motion control BR-549 mentioned earlier in the thread. I'll add it to the list of things to try. I'm only worried because, although this method would be great for soft shots, I'd need a monster motor to get the mass up to speed for a break shot. Maybe I have a break system (giant soloniod) and a strategic shot system: Stepper, rack and pinion.

 

While waiting for IRL540 chips to arrive, could the discussion perhaps cover why an activated coil inside another activated coil doesn't make a motive force? (Here the coils are wrapped in the same orientation and the current is flowing in opposite directions)

I was hopeful this setup would launch the stick forward, as removing permanent magnets from the machine would reduce a bunch of headaches. The stick goes off camera when I close the circuit, my mistake. It just twitches.

My take is that the long thin coils must create a series of small magnetic fields and that when both coils are activated the small magnetic fields must align in the way that two pieces of corduroy align when lain face to face. Am I close?

 

When you strike a pool ball straight on....the ball travels in the hit direction.

How would you like NEW pool balls, that when you hit them straight on.....the ball will fly 90 degrees to the right or to the left of the hit direction?

You will have to learn to play with these new pool balls. A new mechanics.

Sorry to spoil the analogy by trying to spell it out, but I want to be sure I'm getting the right message from it. Electrons are the new pool balls, yes? And the bouncing left or right, determines their north or south magnetic field creation... ?

 

Yes but not just, electrons. It was to realize that the reactions in electronics are different than the reactions of mechanics......which is neutral matter. You call the reaction... inertia in mechanics.....but in electronics it is called reactance. Reactance introduces an angle of separation between the voltage and current in time. A time angle. This screws up the voltage to current ratio because the peak current will not happen at the same time as peak voltage.

Reactance has other characteristics too.....such as direction and inversion.

It all starts at the beginning. The understanding of these concepts....are step built. Things have to be learned in an order.

It's easy to understand the meaning of 5......because you know 1,2,3 and 4.

 

So V=IR is essentially an averaged statement for simple folk. My life is a lie.

I hope this project takes me through a path needing me to know about reactance.

I guess we'll see. I found the IRL540 chips on amazon prime, so hopefully I can get moving with testing again soon.

 

So V=IR is essentially an averaged statement for simple folk. My life is a lie.

Oh no... it's not a lie, at all. In fact, that rule comes in handy every time ... it's just that when you add the time variable to voltage and/or current, a whole new dimension opens up ... literally ... things (mathematically speaking) get exponentially more complicated.

But don't let that intimidate you. I suggest you make a practical approach to what you want, without entirely discarding theory.

 

Oh no... it's not a lie, at all. In fact, that rule comes in handy every time ... it's just that when you add the time variable to voltage and/or current, a whole new dimension opens up ... literally ... things (mathematically speaking) get exponentially more complicated.

But don't let that intimidate you. I suggest you make a practical approach to what you want, without entirely discarding theory.

Thank you cmarinez. I'm big on the practical approach... and was definitely feeling intimidated by this new dimension on what I've always taken as carved-in-stone law. I'm excited to see how crazy things get when I start reducing time between coil activation. Maybe I'll start seeing reactance come into play.

 

I'm only worried because, although this method would be great for soft shots, I'd need a monster motor to get the mass up to speed for a break shot.

I don't understand your thinking here. Why do you think it would take a "monster motor"? Have you ever watched a video of someones DIY CNC machine working, taking a cut? Most of them only use a NEMA 17 or NEMA 23 motor. And cutting metal while moving a 30 pound mill table at the same time takes way more energy than hitting a pool ball.

A break shot would only take more stroke and fast speed, the same as when a human is doing it. Do you use a different arm when you do a break shot than you do when making a play shot? I haven't played pool for maybe 45 years, but when I did I only had one set of arms. Maybe things are different now.

 

I don't understand your thinking here. Why do you think it would take a "monster motor"? Have you ever watched a video of someones DIY CNC machine working, taking a cut? Most of them only use a NEMA 17 or NEMA 23 motor. And cutting metal while moving a 30 pound mill table at the same time takes way more energy than hitting a pool ball.

A break shot would only take more stroke and fast speed, the same as when a human is doing it. Do you use a different arm when you do a break shot than you do when making a play shot? I haven't played pool for maybe 45 years, but when I did I only had one set of arms. Maybe things are different now.

I doubted that a small motor could move a human on a skateboard and am now regularly passed by people riding booster boards. Sooo, my doubting small motors has been wrong before... Then again, booster boards aren't using steppers.

let's chat through some calcs:
Earlier I came up with the number of 6.4N as the force needed to accelerate the shooting mass to breaking speed within the 0.4m stroke. (nobody challenged that, so let's use it for now)
Say we're using a 0.5" diameter pinion, the torque needed would then be 6.4N*0.635cm or 4.68Ncm.
To reach the ~13 m/s break speed on a 0.5" pinion, the motor would also need to access rotational velocities of [13m/s]/[pi*0.0127m] or 326 rps, (~19,500 rpm). I guess my hesitation was not around the torque, but the top speed and the torque. 19.5krpm feels super fast for a stepper motor. But, let me dig for some Nema 17/23 performance curves... (https://catalog.orientalmotor.com/v...-motors/pk-series-60mm-5-phase-stepper-motors)



The chart ends at 1500 RPM... roughly 1/13th the velocity needed. A little searching says that 1200 RPM would be stretching it for a stepper motor. I suppose I could increase the pinion diameter 13x to reduce the angular velocity need into spec, but then I'm ramping up the torque need out of spec. This leads me to therefore want a monster motor... that is my thinking. Where am I going wrong?

 

I doubted that a small motor could move a human on a skateboard and am now regularly passed by people riding booster boards. Sooo, my doubting small motors has been wrong before... Then again, booster boards aren't using steppers.

let's chat through some calcs:
Earlier I came up with the number of 6.4N as the force needed to accelerate the shooting mass to breaking speed within the 0.4m stroke. (nobody challenged that, so let's use it for now)
Say we're using a 0.5" diameter pinion, the torque needed would then be 6.4N*0.635cm or 4.68Ncm.
To reach the ~13 m/s break speed on a 0.5" pinion, the motor would also need to access rotational velocities of [13m/s]/[pi*0.0127m] or 326 rps, (~19,500 rpm). I guess my hesitation was not around the torque, but the top speed and the torque. 19.5krpm feels super fast for a stepper motor. But, let me dig for some Nema 17/23 performance curves... (https://catalog.orientalmotor.com/v...-motors/pk-series-60mm-5-phase-stepper-motors)

View attachment 151902

The chart ends at 1500 RPM... roughly 1/13th the velocity needed. A little searching says that 1200 RPM would be stretching it for a stepper motor. I suppose I could increase the pinion diameter 13x to reduce the angular velocity need into spec, but then I'm ramping up the torque need out of spec. This leads me to therefore want a monster motor... that is my thinking. Where am I going wrong?

Have you considered using a screw and spring mechanism, in which the motor turns the screw, which compresses the spring, which is later released by a trigger?

 

Have you considered using a screw and spring mechanism, in which the motor turns the screw, which compresses the spring, which is later released by a trigger?

Hello again cmartinez, thanks for your continued interest.

The screw and spring mechanism was tried... somewhat. A linear actuator for solar tracking was the compression device. However, the springs in compression were quickly switched out to elastic in tension, as adding/removing bands is easier than changing the spring constant.

Pros: Varying the actuator extension distance directly controls the shot strength, repeatably.
Cons: Releasing the cue under large tension force is touchy, feels like it is always going to misfire and generally a continuous headache. Reloading, or re-latching the actuator to the cue stick after the shot was mechanically complicated and also a massive headache.

This video shows the best performance of the trigger system (modeled after a gun trigger seer)... only needing a pencil whack. The plan was to add a car door lock actuators as the trigger, but the design path shifted towards electromagnetism as, in theory, an electromagnetic solution eliminates the need to "release" or "relatch" the cue... dodging two big headaches.

 

Have you considered using a screw and spring mechanism, in which the motor turns the screw, which compresses the spring, which is later released by a trigger?

Trying to make head and tail of your suggestion, César.

I could not resist

 

There a video of where a guy make a stepper.

 

This is good too

 

There a video of where a guy make a stepper.

This is encouraging. That looks like analog linear motion without notched steps.
I'll certainly need faster, bigger and stronger, but this is encouraging. I wonder what is in the silver tube...

 

This is good too

Thanks for the reference here.
I can't imagine a screw assembly getting up to the speed necessary to reach break speed of a professional pool player. I'm sticking with this electromagnetic solution until it fails, then I'm going with a monster stepper motor belted to the loaded cue stick.

 

Stepper not what you want a servo would work way better.

 

Stepper not what you want a servo would work way better.

And be way pricier ...

 

Servo would give the same movement as a arm.
That's why there used in robotic more then a stepper as a matter of fact there used in a lot of stuff to make movement
more like the hand or arm, That's not to say a stepper cant do what you want it's just easier with a servo to get fluid motions.