[[searchwing-ardupilot-parameters]]

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searchwing-ardupilot-parameters [2020/03/03 01:35]
wf68spef
searchwing-ardupilot-parameters [2020/07/04 04:27] (current)
wf68spef
Line 90: Line 90:
     1 1 BATT_VOLT_PIN 2 2     1 1 BATT_VOLT_PIN 2 2
     1 1 BATT_WATT_MAX 0 4     1 1 BATT_WATT_MAX 0 4
 +    ​
 +    ​
 +===== RPM =====
 +
 +To measure the RPM of the motor we can use a BACK-EMF Measurement from 2 of the 3 motorcables. For more info check out the page:
 +
 +https://​www.hobbywingdirect.com/​products/​rpm-sensor
 +
 +We connected the output pins to a AUX pin of the FC. Check out the info from Ardupilot for some info regarding the following config:
 +
 +https://​ardupilot.org/​copter/​docs/​common-rpm.html
 +
 +
 +^Parametername ​     ^Value ​      ​^Description ​                ​^Remark ​ ^
 +|RPM_MAX |100000.000000000000000000 | | |
 +|RPM_MIN |10.000000000000000000 | | |
 +|RPM_MIN_QUAL |0.100000001490116119 | | |
 +|RPM_PIN |Pin | PIN | depending on FC |
 +|RPM_SCALING |0.143 | ​ | check the hints below for this setting |
 +|RPM_TYPE |2 | AUX | Type needs to be AUX to calc using the given sensor |
 +
 +The RPM in general can be calculated using the formula from https://​www.radiocontrolinfo.com/​brushless-motor-efficiency/​measuring-motor-rpm/​ :
 +
 +''​RPM = ( 120 x Frequency ) / # of Motor Poles''​
 +
 +Thats because:
 +
 +''​The AC current that is produced alternates each time 2 magnetic poles pass by a winding in the stator.
 +''​
 +
 +As Ardupilot measures the periode duration ''​dt_avg''​ of the sensor rectangular signal, and calculates the RPM using
 +
 +''​float rpm = scaling * (1.0e6 / dt_avg) * 60;''​
 +
 +the scaling needs to correct this using
 +
 +''​SCALING = ( 1 / # of Motor Poles ) * 2''​
 +
 +For the Extron 800KV Motor , we have 14 Poles.
  
 ===== Tuning ===== ===== Tuning =====
  • searchwing-ardupilot-parameters.1583195756.txt.gz
  • Last modified: 2020/03/03 01:35
  • by wf68spef