Question of pid-contorl on stepwise configuration

[Derek Lin23]

> -----Original Message-----
> From: James Feist <james.feist at linux.intel.com>
> Sent: Wednesday, September 4, 2019 8:43 AM
> To: Derek Lin23 <dlin23 at lenovo.com>; OpenBMC Maillist
> <openbmc at lists.ozlabs.org>
> Subject: [External] Re: Question of pid-contorl on stepwise configuration
> 
> On 8/21/2019 4:36 AM, Derek Lin23 wrote:
> > Hi team:
> >
> >            I have a question regarding stepwise configuration on
> > pid-control.
> >
> >            I have mine setup like below.
> >
> >                                         {
> >
> >                      "name": "Ambient_Temp",
> >
> >                      "type": "stepwise",
> >
> >                      "setpoint": 0.0,
> >
> >                      "inputs": ["Ambient_Temp"],
> >
> >                      "pid": {
> >
> >                          "samplePeriod": 1.0,
> >
> >                          "positiveHysteresis": 0.0,
> >
> >                          "negativeHysteresis": 0.0,
> >
> >                          "isCeiling": false,
> >
> >                          "reading": {
> >
> >                              "0": 25,
> >
> >                              "1": 30,
> >
> >                              "2": 35
> >
> >                          },
> >
> >                          "output": {
> >
> >                              "0": 15,
> >
> >                              "1": 15,
> >
> >                              "2": 15
> >
> >                         }
> >
> >                      }
> >
> >                  }
> >
> 
> I don't use the json configuration, so you'll have to do a bit of a comparison of
> apples and oranges, but here is an example of a stepwise
> configuration:
> https://github.com/openbmc/entity-manager/blob/08a5b175eec81c53506709
> fda8a7c168748cc22d/configurations/R1000%20Chassis.json#L577
> 
> Reading is the reading of the sensor, and output is the setpoint given to the fan
> pid. Depending on how you configure your system this can either be a percent,
> or it can be a tach reading. When a sensor reaches a reading, the
> corresponding output is given to the fan controller as a setpoint. So it my
> example, when we reach a temp of 30 degrees, the setpoint of 60 is given to
> the fancontroller. This 60 is unitless and depends on how the fan controller
> configuration is implemented how it affects the fans.
> 
> -James

Hi James:

	I'll give it a try. 

Thanks. 
> 
> >            And, I would like to know the meaning of each field, as far
> > as I understand from phosphor-pid-control, "setpoint" seems not used if
> > PID type is stepwise. Is that true? The "reading" field indicates the
> > temperature reading from the sensor "Ambient". The "output" field should
> > indicate the duty % corresponding to the fans, or should output be RPMs?
> > That gives me when a reading of 25 degree(whatever the unit is), the
> > output duty of fans should set to 15%, or set to corresponding RPMs.
> >
> > Do I understand the fields correctly?
> >
> > Thank you,
> >
> > ------------------------------------------------------------------------
> >
> > *Derek Lin*
> > Sr. BMC Engineer
> > 8F,66, San Chong Rd., Nankang Software Park, Taipei.
> > Lenovo Taiwan
> >
> >
> >
> > Phone+886281707411
> > Emaildlin23 at lenovo.com <mailto:dlin23 at lenovo.com>
> >
> >
> >
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