measuring torque in simhydraulics

lalley khan

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Jan 19, 2010, 6:19:04 AM1/19/10

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Hi,

I am driving a variable displacement pump with a constant angular velocity source. I need to measure the torque at the pump shaft, but when I connect the torque sensor;s port R to the shaft and port c to a mechanical rotational reference, I am getting the following error.
"Dynamic states at start of simulation are not consistent. Setting all dynamic state initial conditions to zero may fix this problem."

I am a new user to simulink. Please help me on how to measure the torque. Thanks

Arnaud Miege

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Jan 20, 2010, 12:04:19 PM1/20/10

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"lalley khan" <bari_Z...@hotmail.com> wrote in message <hj44f8$lq8$1...@fred.mathworks.com>...

That's because torque is a through variable and therefore should be measured in series, not parallel. Connect port R to the shaft as you've done, but port C to the ideal angular velocity source port R, not to a MRR. Read the Simscape documentation for details on through and across variables.

HTH,

Arnaud

Zeeshan

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Jan 20, 2010, 7:08:03 PM1/20/10

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Thanks a lot Arnaud! You really solved my problem and a gave me a great tip about the variable types!

Marco Miola

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Feb 3, 2010, 9:34:03 AM2/3/10

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On 20 Gen, 18:04, "Arnaud Miege" <arnaud.mi...@nospam.mathworks.co.uk>
wrote:
> "lalley khan" <bari_Zees...@hotmail.com> wrote in message <hj44f8$lq...@fred.mathworks.com>...

Hi, I've got a similar problem. I need to measure the force from a
pneumatic piston chamber driven by air pressure. I did what you told,
but it still doesn't work and reports the same error log. How can I
sort it out?
Thanks in advance

Lallaey khan

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Jun 8, 2010, 6:34:05 PM6/8/10

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Hi,
In the "Power Unit with Fixed-Displacement Pump Demo", the port R of the torque sensor is attached to the angular velocity source and port C to the shaft whose torque is being monitored. My question is that Port C is the reference probe, so why it is connected to the shaft? shouldn't it be connected to the angular velocity port?
(Type sh_power_unit_fxd_dspl_pump in the command window.This will open the model and the orientaiton can be checked)

Any comment will be highly appreciated. Thanks!

"lalley khan" <bari_Z...@hotmail.com> wrote in message <hj44f8$lq8$1...@fred.mathworks.com>...

Arnaud Miege

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Jul 13, 2010, 11:08:05 AM7/13/10

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"Lallaey khan" <sidh....@yahoo.com> wrote in message <humggt$d9e$1...@fred.mathworks.com>...

> Hi,
> In the "Power Unit with Fixed-Displacement Pump Demo", the port R of the torque sensor is attached to the angular velocity source and port C to the shaft whose torque is being monitored. My question is that Port C is the reference probe, so why it is connected to the shaft? shouldn't it be connected to the angular velocity port?
> (Type sh_power_unit_fxd_dspl_pump in the command window.This will open the model and the orientaiton can be checked)
>
> Any comment will be highly appreciated. Thanks!
>
>

You can actually orient the torque sensor block either way, as long as it is in series, not in parallel. It'll just change the sign of the torque you measure. It's a matter of sign convention.

Arnaud

Arnaud Miege

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Jul 13, 2010, 11:10:22 AM7/13/10

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>
> Hi, I've got a similar problem. I need to measure the force from a
> pneumatic piston chamber driven by air pressure. I did what you told,
> but it still doesn't work and reports the same error log. How can I
> sort it out?
> Thanks in advance

Again, you need to insert the force sensor block in series, not in parallel, because force is a through variable. If it still doesn't work, there's something else that's wrong with your model (as a check, try removing the force sensor, and see if you still have the same error).

HTH,

Arnaud