I guess my hesitation was not around the torque, but the top speed and the torque.

You seem to be equating motor rotation(RPM) with the speed that a rack moves at. Rack and pinion ratio is not the same as spur gear type ratio. The speed/distance that the rack moves is calculated by the distance between theeth on the rack and the number of teeth on the pinion.

You seemed to think at the start of this, that a linear stepper type motor with no gearing advantage(like in a R&P) was going to be OK speed and force wise. But that stepper would basically only have a small number of coils energized at a time. But don't think a rotating stepper with many segments in it energized at the same time, giving more force, and then having the gearing advantage won't be enough force or speed? I guess I'm just getting senile in my old age, because it doesn't make sense to me.

Let me ask another question. Do you have any high speed video of someone making a break? that could be slowed down to see how much the arm moves. Or have you tried making a break shot into a force gauge to get a real world measurement, not a theoretical one?

 

This is good too

That's the linear stepper we were discussing back in poss #19 and #20. Instead of a shaft it turns a nut made internal to the shaft. The screw is held from turning and then moves in a linear motion.

 

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

Isn't a "servo" just identifying that there is feedback control, regardless of the motor type?

My basic understanding... and servo programming algorithms look like this...
If position is to the right of target position, move left.
If position is to the left of the target position, move right.
Or...
If velocity is less than target velocity, accelerate.
If velocity is greater than target velocity, decelerate.

So, in my mind, if I get linear position feedback from something like pic below, figure out how to use it and then close either the position or velocity loop, I'd have a servo.

 

You seem to be equating motor rotation(RPM) with the speed that a rack moves at. Rack and pinion ratio is not the same as spur gear type ratio. The speed/distance that the rack moves is calculated by the distance between theeth on the rack and the number of teeth on the pinion.

You seemed to think at the start of this, that a linear stepper type motor with no gearing advantage(like in a R&P) was going to be OK speed and force wise. But that stepper would basically only have a small number of coils energized at a time. But don't think a rotating stepper with many segments in it energized at the same time, giving more force, and then having the gearing advantage won't be enough force or speed? I guess I'm just getting senile in my old age, because it doesn't make sense to me.

Let me ask another question. Do you have any high speed video of someone making a break? that could be slowed down to see how much the arm moves. Or have you tried making a break shot into a force gauge to get a real world measurement, not a theoretical one?

I'm not equating RPM to rack velocity. I'm converting pinion revolutions to rack linear distance using the pinion pitch circumference. We're saying the same thing: you're counting teeth, I'm using the Pi*Diameter.

I'm not sure what you mean by "gearing advantage" in a rack and pinion system. Gearing advantage to me means that an output shaft has increased torque or angular velocity as compared to an input shaft. Rack and pinions convert torque to linear force.

You aren't senile. I recognize the perspective that a stepper motor with many simultaneously active poles has more force than a stepper with just one active pole (as in my current system).

My thinking is that as each magnet is pulled by a coil, the coil adds kinetic energy to the whole moving mass... until it ultimately has lots of energy to transfer to the cue ball. In my mind it is similar to the reasoning behind the choice to use railgun systems, not stepper or servo motors, to accelerate planes off aircraft carriers.

I do not have high speed footage of a break shot. Nor do I have data on force. I agree that it is time to get data. I have a new force meter I've been trying to get moving. I'll step up efforts there and hopefully have data to report related to the new system using the new IRL540 chips and human break shots.

 

Isn't a "servo" just identifying that there is feedback control, regardless of the motor type?

My basic understanding... and servo programming algorithms look like this...
If position is to the right of target position, move left.
If position is to the left of the target position, move right.
Or...
If velocity is less than target velocity, accelerate.
If velocity is greater than target velocity, decelerate.

So, in my mind, if I get linear position feedback from something like pic below, figure out how to use it and then close either the position or velocity loop, I'd have a servo.

Yes, a servo is any type of motor with feedback and a closed loop system. But when people say "servos" they usually mean the 180 deg. BDC motor ones.

 

Hola Ben

A simple search brought me here

Suggestion: first watch the whole video. Then, with the video in pause, using "L", "J", "." or "," go back and forth as needed.

I do not know how good you could be at doing an educated guess for distances. Should be not difficult.

Buena suerte.

PD: "use as much power as you can control". Wow. Did not expect that.

 

And this, just for fun.

 

And this, just for fun.

The shot being made by using a simple solenoid ...

 

That would be my first pick a solenoid then maybe servo But I think really a well made solenoid would run the table.
and the servo to place the stick. But I can see this done using servo's only too.

 

That would be my first pick a solenoid then maybe servo But I think really a well made solenoid would run the table.
and the servo to place the stick. But I can see this done using servo's only too.

Yeah ... he'd require a BIG solenoid for what he wants, if I understand things correctly ... it could perhaps be energized by a capacitor bank, and the proper IGBT ... mosfets might be too wimpy for the job, maybe ...

 

That would be my first pick a solenoid then maybe servo But I think really a well made solenoid would run the table.
and the servo to place the stick. But I can see this done using servo's only too.

With much respect, I say let's not get carried away. A really well made solenoid could hit the cue ball very solidly. Running the table is a completely different set of engineering challenges...

 

Yeah ... he'd require a BIG solenoid for what he wants, if I understand things correctly ... it could perhaps be energized by a capacitor bank, and the proper IGBT ... mosfets might be too wimpy for the job, maybe ...

Speaking of giant solenoids, the shooting-mechanism-fail before this latest one is shown here... five pounds of magnet wire. I thought additional metal would amplify the magnetic field so I wrapped a metal pipe. The huge magnet I put in the shooting tube just locked onto the pipe... anyway, big solenoids.


I appreciate mention of IGBTs. The following was a very informative read: https://www.electronicproducts.com/...iscrete_Power_Transistors/MOSFET_vs_IGBT.aspx

 

Hola Ben

A simple search brought me here

Suggestion: first watch the whole video. Then, with the video in pause, using "L", "J", "." or "," go back and forth as needed.

I do not know how good you could be at doing an educated guess for distances. Should be not difficult.

Buena suerte.

PD: "use as much power as you can control". Wow. Did not expect that.

I'm surprised he lifts his body right before contact. I'd think he would want to reduce the number of moving parts... Good vid. Thanks.
15" feels like a good estimate on break shot stroke length. That's what I have been using and what I see here.

 

And this, just for fun.

Videos of this machine make me happy there is no point in making a pool playing robot. If Boeing, Northrup Grumman, Google, Teslsa or any legitimate organization batted an eye and put a week into the challenge it would be solved and my hobby would be spoiled. But, they don't, because there is no point... but, as this video shows well, they certainly could.

Anyway, I think this robot is cool, but not impressive in the pool playing realm. It is running an open loop routine that has zero processing of the actual game... or of any inputs at all for that matter. This is a sales person throwing something together for a trade show. Deep green is impressive, and the furthest on the pool playing robot trail that I know of:

 

I'm not sure what you mean by "gearing advantage" in a rack and pinion system.

The gearing advantage comes from the distance between the center of the pinions shaft to the pitch contact point on the rack. While I'm probably not using the correct terms when talking "gearing advantage" there is a leverage advantage when considering the same force being place on the end of the rack. It has been many, many years since I had to figure anything like this, so my terms may not be correct.

That robot in the 'deep green' video looks like it uses the same rack and pinion idea for it's cue movement, that I was suggesting. Also what I said about not using this 'engineering' type information for a long time also applies to stepper motors. I didn't take the time to look into the motor you referenced earlier,(since it's not my project) but the torque on it looks kind of low. Was it a single stack motor? You need to compare oranges to oranges, not oranges to apples.

 

The gearing advantage comes from the distance between the center of the pinions shaft to the pitch contact point on the rack. While I'm probably not using the correct terms when talking "gearing advantage" there is a leverage advantage when considering the same force being place on the end of the rack. It has been many, many years since I had to figure anything like this, so my terms may not be correct.

That robot in the 'deep green' video looks like it uses the same rack and pinion idea for it's cue movement, that I was suggesting. Also what I said about not using this 'engineering' type information for a long time also applies to stepper motors. I didn't take the time to look into the motor you referenced earlier,(since it's not my project) but the torque on it looks kind of low. Was it a single stack motor? You need to compare oranges to oranges, not oranges to apples.

I didn't mean to be picky about the semantics. Sorry, I really appreciate your responses.
I should know more about all of this tomorrow. My IRL540 chips arrived, I got the force sensor working and I have 2 hours carved out of my schedule. Will post results.

 

I didn't mean to be picky about the semantics.

You're not making me upset, I was just clarifying that I may be using the wrong 'technical terms' many members point that out to me. I enjoy discussing and working through problems. The one thing I miss most about being in retirement, solving problems.

 

The one thing I miss most about being in retirement, solving problems.

Ohhh... I can give you plenty of that!

 

Ohhh... I can give you plenty of that!

When did we get married?

 

When did we get married?

... I don't think I'll ever get that drunk ...