Implemented FreeWheel #4004

AHaumer · 2022-06-26T16:48:07Z

As mentioned in #3977:
I see that we have a rather sophisticated Mechanics.Rotational.Components.OneWayClutch, but no simple ideal freewheel (like the Electrical.Analog.Ideal.Diode). We could introduce such a component for usage e.g. in bicycle models.

christiankral

@AHaumer Please check the following changes and re-invite me for a review afterwards.

I added SI units the parameters in 8c6ba79
I updated the documentation of the example in 73078a6

beutlich

The new model is missing in ModelicaTest.Rotational.AllComponents.
The new example misses the required file Modelica/Resources/Reference/Modelica/Mechanics/Rotational/Examples/DemoFreeWheel/comparisonSignals.txt

beutlich

The new model is missing in ModelicaTest.Rotational.AllComponents.
The new example misses the required file Modelica/Resources/Reference/Modelica/Mechanics/Rotational/Examples/DemoFreeWheel/comparisonSignals.txt

tobolar

Is there any reason to not extend from Modelica.Mechanics.Rotational.Interfaces.PartialCompliantWithRelativeStates as e.g. Rotational.Components.Clutch does?

…rdLibrary into FreeWheel

…alCompliant Thus, the sign convention of phi_rel (and w_rel) established for "rotational" components is assured. Note: doing so, the sign of w_rel and tau changes - compared to the original implementation.

tobolar · 2022-08-03T08:30:41Z

Is there any reason to not extend from Modelica.Mechanics.Rotational.Interfaces.PartialCompliantWithRelativeStates as e.g. Rotational.Components.Clutch does?

With 7e6f667, the freewheel extends now from Mechanics.Rotational.Interfaces.PartialCompliant (without the state selection since it could be problematic). Thus, the sign convention of phi_rel (and w_rel) established for all rotational components is assured now. Consequently, the sign of w_rel and tau changes - compared to the original implementation. The example models work fine.

tobolar

Fine for me now. Nice work!

christiankral · 2022-08-03T19:31:27Z

Some time ago we were trying to get rid of all the "Diagram" drawings that explain the model. Instead, the "Diagram" diagram shall be added to the documentation. ~~I will add it.~~
The diagram tau vs w_rel has to be adapted, because:

With 7e6f667, the freewheel extends now from Mechanics.Rotational.Interfaces.PartialCompliant (without the state selection since it could be problematic). Thus, the sign convention of phi_rel (and w_rel) established for all rotational components is assured now. Consequently, the sign of w_rel and tau changes - compared to the original implementation. The example models work fine.

The currently implemented diagram is a bit misleading, as it is not clear what the parameters tauRes and wRes really mean. The current "Diagram" view shows:

christiankral · 2022-08-03T19:57:38Z

Before implementing a change I would like to discuss the meaning of the parameters tauRes and wRes:

The current implementation is:

if free = false the characteristic is indicated by tau = tauRes @ w_rel = 1 (1/s)
if free = true the characteristic is indicated by w_rel = -wRes @ tau = -1 (Nm)

Hmmm.... the actual implementatioin is somehow avoiding the units that specify the slope of the two branches in the diagram. The diode models uses Ron (unit V/A) anf Goff (unit A/V): this makes a lot more sense to me.

a. Creating the new units "Nm.s" and "1/(s.Nm)" may be one way to resolve this point.

b. We could improve the description to better explain the meaning of tauRes and wRes: this, however, seems not to be a sound way of dealing with this problem, as we avoid the slopes -- which indicate the physical nature of the model.

@AHaumer @tobolar any ideas on how to resolve this "unit" issue?

christiankral · 2022-08-03T20:00:45Z

OK, possibly the unit SI.RotationalDampingConstant could resolve this issue...

tobolar · 2022-08-04T07:24:34Z

The current implementation is:

if free = false the characteristic is indicated by tau = tauRes @ w_rel = 1 (1/s)

if free = true the characteristic is indicated by w_rel = -wRes @ tau = -1 (Nm)

To my understanding, the implementation is:

if free = false then tau = (-)flange_a.tau -> s -> w_rel = s*tauRes
if free = true then w_rel -> s -> tau = s*wRes

Hmm, the documentation says:

free = false: torque is transferred with a residual difference wRes of relative angular velocity of the flanges.
free = true: the flanges move independently except a residual friction torque tauRes.

It seems this fits not well.

already solved

AHaumer · 2022-08-05T08:20:50Z

@tobolar and @christiankral thanks for taking care!
I need some free hours to consider the changed sign convention ... then I'll propose the following:

Keep the "Diagram" drawing, but check whether it has to be adapted to the changed signs.
Check the documentation whether it has to be adapted to the changed signs.
Replace the parameter tauRes by RotationalDampingCoefficientFree.
Replace the parameter wRes by 1/RotationalDampingCoefficientLocked.

AHaumer · 2022-08-05T17:15:32Z

@tobolar and @christiankral I think a have a sound solution (looks like a translation of the electrical diode):

  parameter SI.RotationalDampingConstant residualFriction=1e-5 "Residual friction coefficient (free = true)";
  parameter SI.RotationalDampingConstant torqueTransmission=1e5 "Torque transmission coefficient (free = false)";

free = false: flange_a is driving flange_b; residual slip is defined by w_rel = tau/torqueTransmission.
free = true: flange_b rotates (nearly) independent of flange_a; residual friction is defined by tau = w_rel*residualFriction.

tobolar · 2022-08-18T16:06:26Z

@AHaumer , @christiankral
Thinking again about the two "residual" parameters.
One can understand tauRes at free=true being a residual torque due to some friction occurency between the two flanges. Thus, for me both tauRes (N.m) and also residualFriction (no SI unit!) could be acceptable.
Regarding wRes (rad/s), this is a sort of slip velocity ("Schlupf") which occurs at free=false and forces w_b being smaller then w_a.
So to me, the current documentation of the model is fine and provides an explanation everybody can follow.
(I know, you both clarified this already. ;-) )

I'm still stumbling about the two parameters. Using tauRes and wRes has an advantage that user can use its own terms to get they values, e.g. the friction. In contrast, torqueTransmission is somehow fancy.

Regarding units - both tauand w_rel depend, in fact, on the unitless variable s which only "transfers" value, not unit.
So I would tend to b) in #4004. Of course, this makes plotting of the two branches in the diagram difficult.

christiankral · 2022-10-17T12:29:47Z

@tobolar Would the following wording make it better on your opinion:

parameter Real(final unit="rad/N/m/s") residualAngularVelocity =1e-5 "Residual angular velocity coefficient (free = false)";
...
  w_rel = s*unitTorque         *(if free then 1 else residualAngularVelocity);

tobolar · 2022-11-08T09:19:11Z

Would the following wording make it better on your opinion:..

Sounds good. The following could be a reasonable implementation now:

parameter Real residualFriction=1e-5 "Residual friction coefficient (if free = true)";
parameter Real residualAngularVelocity=1e-5 "Residual angular velocity coefficient (if free = false)";
...
w_rel = s*unitAngularVelocity * (if free then 1 else residualAngularVelocity);
tau   = s*unitTorque          * (if free then residualFriction else 1);

The documentation shall be modified then:

free = false: flange_a is driving ...
...
tau = w_rel / residualAngularVelocity;

Regarding the two equations for tauin the documentation (where neither unitAngularVelocity nor unitTorque is used), the correct units of the two parameters shall be:

residualFriction (unit="N.s")
residualAngularVelocity (unit="1/N/s")

but it seems to be strange since one could, in general, expect both friction and a coefficient being unitless.

christiankral · 2022-11-15T11:02:58Z

w_rel = s*unitAngularVelocity * (if free then 1 else residualAngularVelocity);
tau   = s*unitTorque          * (if free then residualFriction else 1);

On my understanding the units of the proposed equations are not correct. They shall rather be:

parameter residualFriction (unit="N.m.s")=1e-5 "Residual friction coefficient (if free = true)";
parameter residualAngularVelocity (unit="1/N/m/s")=1e-5 "Residual angular velocity coefficient (if free = false)";
w_rel = s*unitTorque          * (if free then 1 else residualAngularVelocity);
tau   = s*unitAngularVelocity * (if free then residualFriction else 1);

Note, that I swaped unitTorque and unitAngularVelocity in the two equations.

christiankral · 2022-11-15T11:09:15Z

residualFriction (unit="N.s")

residualAngularVelocity (unit="1/N/s")

@tobolar As we deal with torques (not forces) the units shall rather be N.m.s and 1/N/m/s, isn't is?

christiankral · 2022-11-15T11:11:15Z

Alternatively we could consider the unit rad, but I am not sure if this makes sense.

parameter residualFriction (unit="N.m.s/rad")=1e-5 "Residual friction coefficient (if free = true)";
parameter residualAngularVelocity (unit="rad/N/m/s")=1e-5 "Residual angular velocity coefficient (if free = false)";

tobolar · 2022-11-16T10:38:12Z

@christiankral
IMO, one would expect regarding a mechanical component:

"friction coefficient" (mu overall in MSL) is generally a unitless quantity,
and so is probably also with "angular velocity coefficient".

This is why I tend to have no units. Optionally, we schould think again of changing "residualFriction" name and description. Not sure if this also holds for residualAngularVelocity.

HansOlsson · 2022-11-16T10:51:19Z

Note that unitless can mean two different things:

A variable without a specified unit.
A variable with unit="1", also known as dimensionless.

To me the friction coefficient should be of the second kind for translational friction, but I notice that often in MSL it is of the first kind. (And it is generally not possible to deduce its unit because it appears as mu*cgeo where the geometric coefficient also is without unit.)

For rotational friction it is not clear to me if mu or cgeo should handle the conversion between force and torque.

tobolar · 2022-11-16T11:35:40Z

@HansOlsson Need to open a new issue?
(See Sec. 2.3.3 Dimensions of quantities of the BIPM: The International System of Units – 9th edition (2019) - probably you know it already. )

HansOlsson · 2022-11-16T12:08:33Z

@HansOlsson Need to open a new issue?

Possibly. You decide.

christiankral · 2024-09-25T12:33:26Z

@HansOlsson Is using unitAngularVelocity and unitTorque still "state of the art" in how we handle the diode and freewheel implementation?

implemented FreeWheel

9c92137

AHaumer added enhancement New feature or enhancement L: Mechanics.Rotational Issue addresses Modelica.Mechanics.Rotational labels Jun 26, 2022

AHaumer requested review from dietmarw, christiankral, MartinOtter and tobolar June 26, 2022 16:48

AHaumer self-assigned this Jun 26, 2022

AHaumer enabled auto-merge June 26, 2022 16:48

christiankral added 4 commits July 4, 2022 11:39

Remove Dymola specific annotation, add stop time

b9c085e

Source code formatting

a4ea7f2

Add SI units to parameters

8c6ba79

Improve documentation

73078a6

christiankral reviewed Jul 4, 2022

View reviewed changes

AHaumer requested a review from christiankral July 4, 2022 16:57

beutlich requested changes Jul 4, 2022

View reviewed changes

comparisonSignals.txt and ModelicaTest

8696fef

AHaumer requested a review from beutlich July 5, 2022 06:29

beutlich previously requested changes Jul 5, 2022

View reviewed changes

tobolar added 5 commits July 5, 2022 14:26

Improve documettation

d3abff0

Improve documentation

4f654f8

Rename constants (similar to Rotational.Components.OneWayClutch)

7b7fd27

Icon: add dark border lines of "clutch"

191ea69

Diagram: use proper variable name

3ee5f45

tobolar requested changes Jul 18, 2022

View reviewed changes

Merge branch 'FreeWheel' of https://github.com/AHaumer/ModelicaStanda…

01670b6

…rdLibrary into FreeWheel

AHaumer requested review from beutlich and tobolar July 29, 2022 16:17

FreeWheel extends from Modelica.Mechanics.Rotational.Interfaces.Parti…

7e6f667

…alCompliant Thus, the sign convention of phi_rel (and w_rel) established for "rotational" components is assured. Note: doing so, the sign of w_rel and tau changes - compared to the original implementation.

tobolar approved these changes Aug 3, 2022

View reviewed changes

Change sign of s

f21bc0f

clarified the parameters for the modes free = true / false

fecf3c9

AHaumer requested a review from tobolar August 5, 2022 17:18

dietmarw removed their request for review September 5, 2022 13:03

beutlich removed their request for review September 24, 2022 10:20

christiankral added 2 commits September 25, 2024 14:13

Remove diagram drawing

cc28457

Add diagram drawing to documentation

da0450c

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Implemented FreeWheel #4004

Implemented FreeWheel #4004

AHaumer commented Jun 26, 2022

christiankral left a comment •

edited

Loading

beutlich left a comment

beutlich left a comment

tobolar left a comment •

edited

Loading

tobolar commented Aug 3, 2022 •

edited

Loading

tobolar left a comment •

edited

Loading

christiankral commented Aug 3, 2022 •

edited

Loading

christiankral commented Aug 3, 2022

christiankral commented Aug 3, 2022

tobolar commented Aug 4, 2022 •

edited

Loading

AHaumer commented Aug 5, 2022

AHaumer commented Aug 5, 2022 •

edited

Loading

tobolar commented Aug 18, 2022

christiankral commented Oct 17, 2022

tobolar commented Nov 8, 2022 •

edited

Loading

christiankral commented Nov 15, 2022 •

edited

Loading

christiankral commented Nov 15, 2022

christiankral commented Nov 15, 2022

tobolar commented Nov 16, 2022

HansOlsson commented Nov 16, 2022

tobolar commented Nov 16, 2022 •

edited

Loading

HansOlsson commented Nov 16, 2022

christiankral commented Sep 25, 2024

Implemented FreeWheel #4004

Are you sure you want to change the base?

Implemented FreeWheel #4004

Conversation

AHaumer commented Jun 26, 2022

christiankral left a comment • edited Loading

Choose a reason for hiding this comment

beutlich left a comment

Choose a reason for hiding this comment

beutlich left a comment

Choose a reason for hiding this comment

tobolar left a comment • edited Loading

Choose a reason for hiding this comment

tobolar commented Aug 3, 2022 • edited Loading

tobolar left a comment • edited Loading

Choose a reason for hiding this comment

christiankral commented Aug 3, 2022 • edited Loading

christiankral commented Aug 3, 2022

christiankral commented Aug 3, 2022

tobolar commented Aug 4, 2022 • edited Loading

AHaumer commented Aug 5, 2022

AHaumer commented Aug 5, 2022 • edited Loading

tobolar commented Aug 18, 2022

christiankral commented Oct 17, 2022

tobolar commented Nov 8, 2022 • edited Loading

christiankral commented Nov 15, 2022 • edited Loading

christiankral commented Nov 15, 2022

christiankral commented Nov 15, 2022

tobolar commented Nov 16, 2022

HansOlsson commented Nov 16, 2022

tobolar commented Nov 16, 2022 • edited Loading

HansOlsson commented Nov 16, 2022

christiankral commented Sep 25, 2024

christiankral left a comment •

edited

Loading

tobolar left a comment •

edited

Loading

tobolar commented Aug 3, 2022 •

edited

Loading

tobolar left a comment •

edited

Loading

christiankral commented Aug 3, 2022 •

edited

Loading

tobolar commented Aug 4, 2022 •

edited

Loading

AHaumer commented Aug 5, 2022 •

edited

Loading

tobolar commented Nov 8, 2022 •

edited

Loading

christiankral commented Nov 15, 2022 •

edited

Loading

tobolar commented Nov 16, 2022 •

edited

Loading