coaxial axes / offset comp how to

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10 years 10 months ago #66699 by bkt
coaxial axes / offset comp how to was created by bkt
I have 2 rotary axis coaxial ..... in my custom kins I have add these row in inverse kins
Code:
joints[3] = world->a; joints[4] = world->b+a;

in these way when move a Axis I move b axis too .... the axes have the same parameter, and same type of mechanical constructions. When move b axe ... a axes no move. It's all I need. And In these way I obtain the right mouvement in world mode. But in manual mode this magical trik obviusly not work.
I think is better choice to do this It is make some changes in my hal file .... I use analogue + encoder .....

this is my actual hal file (A-B section):
Code:
#******************* # AXIS A #******************* setp pid.a.Pgain [JOINT_3]P setp pid.a.Igain [JOINT_3]I setp pid.a.Dgain [JOINT_3]D setp pid.a.bias [JOINT_3]BIAS setp pid.a.FF0 [JOINT_3]FF0 setp pid.a.FF1 [JOINT_3]FF1 setp pid.a.FF2 [JOINT_3]FF2 setp pid.a.deadband [JOINT_3]DEADBAND setp pid.a.maxoutput [JOINT_3]MAX_OUTPUT setp pid.a.error-previous-target true #setp pid.a.maxerror .0005 net a-index-enable <=> pid.a.index-enable net a-enable => pid.a.enable net a-pos-cmd => pid.a.command net a-vel-cmd => pid.a.command-deriv net a-pos-fb => pid.a.feedback net a-output => pid.a.output # ---PWM Generator signals/setup--- setp hm2_5i25.0.7i77.0.1.analogout3-scalemax [JOINT_3]OUTPUT_SCALE setp hm2_5i25.0.7i77.0.1.analogout3-minlim [JOINT_3]OUTPUT_MIN_LIMIT setp hm2_5i25.0.7i77.0.1.analogout3-maxlim [JOINT_3]OUTPUT_MAX_LIMIT net a-output => hm2_5i25.0.7i77.0.1.analogout3 net a-pos-cmd joint.3.motor-pos-cmd net a-enable joint.3.amp-enable-out # ---Encoder feedback signals/setup--- setp hm2_5i25.0.encoder.03.counter-mode 0 setp hm2_5i25.0.encoder.03.filter 1 setp hm2_5i25.0.encoder.03.index-invert 0 setp hm2_5i25.0.encoder.03.index-mask 0 setp hm2_5i25.0.encoder.03.index-mask-invert 0 setp hm2_5i25.0.encoder.03.scale [JOINT_3]ENCODER_SCALE net a-pos-fb <= hm2_5i25.0.encoder.03.position net a-vel-fb <= hm2_5i25.0.encoder.03.velocity net a-pos-fb => joint.3.motor-pos-fb net a-index-enable joint.3.index-enable <=> hm2_5i25.0.encoder.03.index-enable net a-pos-rawcounts <= hm2_5i25.0.encoder.03.rawcounts # ---setup home / limit switch signals--- net a-home-sw => joint.3.home-sw-in net both-a => joint.3.neg-lim-sw-in net both-a => joint.3.pos-lim-sw-in #******************* # AXIS B #******************* setp pid.b.Pgain [JOINT_4]P setp pid.b.Igain [JOINT_4]I setp pid.b.Dgain [JOINT_4]D setp pid.b.bias [JOINT_4]BIAS setp pid.b.FF0 [JOINT_4]FF0 setp pid.b.FF1 [JOINT_4]FF1 setp pid.b.FF2 [JOINT_4]FF2 setp pid.b.deadband [JOINT_4]DEADBAND setp pid.b.maxoutput [JOINT_4]MAX_OUTPUT setp pid.b.error-previous-target true #setp pid.b.maxerror .0005 net b-index-enable <=> pid.b.index-enable net b-enable => pid.b.enable net b-pos-cmd => pid.b.command net b-vel-cmd => pid.b.command-deriv net b-pos-fb => pid.b.feedback net b-output => pid.b.output # ---PWM Generator signals/setup--- setp hm2_5i25.0.7i77.0.1.analogout4-scalemax [JOINT_4]OUTPUT_SCALE setp hm2_5i25.0.7i77.0.1.analogout4-minlim [JOINT_4]OUTPUT_MIN_LIMIT setp hm2_5i25.0.7i77.0.1.analogout4-maxlim [JOINT_4]OUTPUT_MAX_LIMIT net b-output => hm2_5i25.0.7i77.0.1.analogout4 net b-pos-cmd joint.4.motor-pos-cmd net b-enable joint.4.amp-enable-out # ---Encoder feedback signals/setup--- setp hm2_5i25.0.encoder.04.counter-mode 0 setp hm2_5i25.0.encoder.04.filter 1 setp hm2_5i25.0.encoder.04.index-invert 0 setp hm2_5i25.0.encoder.04.index-mask 0 setp hm2_5i25.0.encoder.04.index-mask-invert 0 setp hm2_5i25.0.encoder.04.scale [JOINT_4]ENCODER_SCALE net b-pos-fb <= hm2_5i25.0.encoder.04.position net b-vel-fb <= hm2_5i25.0.encoder.04.velocity net b-pos-fb => joint.4.motor-pos-fb net b-index-enable joint.4.index-enable <=> hm2_5i25.0.encoder.04.index-enable net b-pos-rawcounts <= hm2_5i25.0.encoder.04.rawcounts # ---setup home / limit switch signals--- net b-home-sw => joint.4.home-sw-in net both-b => joint.4.neg-lim-sw-in net both-b => joint.4.pos-lim-sw-in

I try to add (with sum function) encoder.04 to encoder.03 velocity and position ... but I have follow error ....

Is possible to do this? What is the right mode to do?

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10 years 10 months ago #66731 by andypugh
Replied by andypugh on topic coaxial axes

k-1 wrote:

Code:
joints[3] = world->a; joints[4] = world->b+a;


That almost certainly needs to be world->a + world->b

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10 years 10 months ago #66737 by bkt
Replied by bkt on topic coaxial axes
sorry. Not remember the correct syntax. I modify it some time ago. I think you are in right ... excuse the inaccuracy .... but my intent is make the same things in my hal file ... so I think I will have the same behavior in the world and axes mode too ... (obviusly when hal file is right modified in custom kins joint[4] return to = world->b).

to do so in my hal file I add the value of the encoder (i just try this without succes) or the N- pos - cmd ?? or still I have to add the values ​​of the pid ??

Tanks in advance
Giorgio

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10 years 10 months ago #66746 by bkt
Replied by bkt on topic coaxial axes
perfect if sum :
Code:
......................... net a-pos-cmd => joint.3.motor-pos-cmd sum2.0.in0 ............................. net b-sum-a joint.3.motor-pos-cmd => sum2.0.in1 net b-pos-cmd sum2.0.out

obtain a correct mouvement of these 2 axis but when exeed the amount of ferror value (set hight ...100 for testing) I obtain following error of axis4 ..... obviusly I must sum the encoder signal .....
Is necessary sum all encoder signal (velocity pos rawcount etc etc...) or only encoder position?
I must sum the pid.N.output signal too??

regards
giorgio

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10 years 10 months ago #66749 by andypugh
Replied by andypugh on topic coaxial axes
I have no idea why you are trying to do it in HAL if you had it working in kinematics.

You will get a following error if |axis.N.motor-position-fb - axis.N.motor,position.cmd| > F_ERROR

So, you have to arrange the HAL so that that doesn't happen.

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10 years 10 months ago #66759 by bkt
Replied by bkt on topic coaxial axes
because it work only in world mode .... when homing the axis for example the axis move one to one ... in my case on B axes these causes mecanical damage ..... however if I change hal so always follow the axis B axis if it moves ..... for example during the reset will not go banging .

it was not clear if the two axes A and B have mouvemente mechanically limited ... so it is not sufficient that it functions in world mode only.... it must always work .

I am right if I make the sum of hm2_5i25.0.encoder.03.position + hm2_5i25.0.encoder.04.position instead only hm2_5i25.0.encoder.04.position for B axes ? Or must sum other pid and encoder signal too??

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10 years 10 months ago #66828 by andypugh
Replied by andypugh on topic coaxial axes

k-1 wrote: I am right if I make the sum of hm2_5i25.0.encoder.03.position + hm2_5i25.0.encoder.04.position instead only hm2_5i25.0.encoder.04.position for B axes ? Or must sum other pid and encoder signal too??


It is impossible for me to say, without actually knowing what you are trying to do, but the command signal and the feedback signal from and to motion have to be equal, and the PID component attempts to make the pid.command and pid.feedback equal.

The rest is arithmetic.

Bear in mind that there are an infinite number of possibilities for a + b = X.

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10 years 10 months ago #66839 by bkt
Replied by bkt on topic coaxial axes
.... I have two rotary axes. One shaft is inside to other .... when rotating the outer shaft (A axe) must turn also to the inner strength (B axe) . As if the outside is stopped I can stroll into the inner. All for only 360 °.

sum of encoder position not solve following axes B error.
Code:
net b-index-enable <=> pid.b.index-enable net b-enable => pid.b.enable net b-pos-cmd => pid.b.command net b-vel-cmd => pid.b.command-deriv net b-pos-fb => pid.b.feedback net b-output => pid.b.output # ---PWM Generator signals/setup--- setp hm2_5i25.0.7i77.0.1.analogout4-scalemax [JOINT_4]OUTPUT_SCALE setp hm2_5i25.0.7i77.0.1.analogout4-minlim [JOINT_4]OUTPUT_MIN_LIMIT setp hm2_5i25.0.7i77.0.1.analogout4-maxlim [JOINT_4]OUTPUT_MAX_LIMIT net b-output => hm2_5i25.0.7i77.0.1.analogout4 net b-sum joint.4.motor-pos-cmd => sum2.0.in1 net b-pos-cmd sum2.0.out #joint.4.motor-pos-cmd net b-enable joint.4.amp-enable-out # ---Encoder feedback signals/setup--- setp hm2_5i25.0.encoder.04.counter-mode 0 setp hm2_5i25.0.encoder.04.filter 1 setp hm2_5i25.0.encoder.04.index-invert 0 setp hm2_5i25.0.encoder.04.index-mask 0 setp hm2_5i25.0.encoder.04.index-mask-invert 0 setp hm2_5i25.0.encoder.04.scale [JOINT_4]ENCODER_SCALE net b-pos-fb-ab sum2.1.in1 <= hm2_5i25.0.encoder.04.position #net b-vel-fb-ab sum2.2.in1 <= hm2_5i25.0.encoder.04.velocity net b-pos-fb <= sum2.1.out #<= hm2_5i25.0.encoder.04.position #<= sum2.1.out net b-vel-fb <= hm2_5i25.0.encoder.04.velocity #<= sum2.2.out net b-pos-fb => joint.4.motor-pos-fb net b-index-enable joint.4.index-enable <=> hm2_5i25.0.encoder.04.index-enable net b-pos-rawcounts <= hm2_5i25.0.encoder.04.rawcounts

As you see the signal b-pos-fb is sum to a-pos-fb ... i try with gain0 to -1 ... but obtain only the negative amoun of error.

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10 years 10 months ago #66841 by andypugh
Replied by andypugh on topic coaxial axes
Do you want them both to turn independently?

As far as LinuxCNC is concerned it is all just numbers. You decide what each number means and what you want to do with it.

the A and B commands in G-code put numbers into HAL. The PID component tries to make two numbers equal. Encoders provide numbers that depend on position in any way that you decide they should.

Have you considered the "offset" HAL component? Does that do what you want?

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10 years 10 months ago #66842 by bkt
Replied by bkt on topic coaxial axes

Do you want them both to turn independently?


Yes.

I not consider offset components .... real sorry.

Correct me if I'm wrong, in my case:

offset.N.offset float in --> a-pos-cmd

offset.N.in float in --> b-pos-cmd

offset.N.out float out --> b-pos-cmd/joint.4.motor-pos-cmd

offset.N.fb-in float in -->a-pos-fb

offset.N.fb-out float out --> b-pos-fb

I misunderstood?

It update immediately or some in certain cases? I never try it.

regards
giorgio

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