This page describes how to identify the machine parameters by means of PMC. The knowledge of parameters is necessary to control.
WARNING: Any new machine connected to the PMC should be identified before run in closed control loop.
You may need to adjust some parameters in accordance with the capabilities of the machine to not burn it. Default is acceptable for most large RC motors but be aware. These parameters are used to probe the machine.
(pmc) reg pm.probe
There are a lot of parameters that can affect the machine identification. But we believe that they will need a change only in a complicated case. Most likely you will need to decrease probing currents for a small machine.
pm.probe_current_hold- Machine probing current that is used to estimate stator resistance. Note it must be large enough to get perceptible voltage drop.pm.probe_current_sine- Sine wave probing signal amplitude that is used to estimate stator winding impedance.pm.probe_speed_hold- Speed setpoint for the initial spinup. At this speed flux linkage and noise threshold will be estimated.pm.probe_loss_maximal- Maximal heating losses on stator winding. This allows us to assume maximal machine current.pm.forced_hold_D- Forced current setpoint which should be enough to hold rotor in aligned position and force it turn.
If you use power supply that not tolerate reverse current then pay attention to the wattage limit settings.
pm.watt_wA_reverse- Maximal reverse current on DC link.pm.watt_uDC_maximal- Maximal overvoltage on DC link.
Also do not forget to reset the machine parameters if you have previously run another machine.
(pmc) pm_default_machine
To achieve the best accuracy PMC has the ability of self-adjust voltage and current onboard sensors. The self-adjustment procedure allows you to match measurement channels between phases.
(pmc) pm_self_adjust
This is enough to do it once and store the values in the flash. But we recommend to do it again if you change DC link voltage.
Also look into Integrity Self Test page to get more info about self-adjustment functions.
This number relates the electrical speed with the mechanical. We believe you
are able to identify Zp simply by counting the number of magnets on the rotor
then divide it by 2. This is the most famous method.
(pmc) reg pm.const_Zp <n>
If access to the machine is restricted and to count the magnets is impossible
then you can leave a value 1. Instead of mechanical speed you will see
electrical speed. By independent measuring the mechanical speed you can
estimate Zp and set it later.
We measure the resistance pm.const_Rs by difference of voltage drop on two
values of holding current. For more accuracy you need to increase the probing
current or reduce DC link voltage.
Then we inject a high frequency sinusoidal signal to measure the full impedance
tensor and calculate DQ inductances pm.const_im_Ld and pm.const_im_Lq.
(pmc) pm_probe_impedance
If the procedure fails with an error code sure that probing currents are suitable for your machine.
This parameter also known as Kv rating. Internal representation is
pm.const_lambda that linked with Kv by following equation.
60
lambda = ----------------------------
2 * PI * sqrt(3) * Kv * Zp
To identify lambda you have to run the machine. Also the rotor should rotate
at significant speed to get enough BEMF voltage. We do a forced initial spinup
to reach this condition.
(pmc) pm_probe_spinup
If the procedure fails to spinup the machine try to adjust forced control parameters. Also you can specify Kv manually if you know it exactly and Zp number is already configured correcly.
(pmc) reg pm.const_lambda_kv <rpm/V>
To get a more accurate flux linkage estimate you can run the machine at high speed and request lambda probing manually. Do not load the machine at this.
(pmc) pm_fsm_startup
(pmc) reg pm.s_setpoint_rpm <rpm>
...
(pmc) pm_probe_const_flux_linkage
If you failed to start the machine with pm_probe_spinup you have an option to
identify the flux linkage in detached mode. You will have to rotate the machine
manually in this case.
(pmc) pm_probe_detached
PMC will wait for the machine to reach at least pm.zone_threshold speed.
In case of you use pm_probe_spinup after a flux linkage we estimate speed
noise level to know the lower bound of flux observer operation. As a result
these threshold values are calculated.
(pmc) reg pm.zone_noise
(pmc) reg pm.zone_threshold
If you have estimated flux linkage in detached mode or specified Kv manually you should probe the noise threshold manually when the machine is in run.
(pmc) pm_fsm_startup
(pmc) reg pm.s_setpoint_rpm <rpm>
...
(pmc) pm_probe_noise_threshold
In case of you use pm_probe_spinup the final estimate is a moment of inertia
pm.const_Ja. To do this possible a speed maneuver will be performed. Note
that this may result energy regeneration so your power supply must tolerate
this. Either you should limit maximal DC link current reverse as stated above.
This constant is used to tune speed control loop. Also it is used in operation to predict the speed changes from an applied current and so on.
If you have estimated flux linkage in detached mode or specified Kv manually you should probe the moment of inertia manually.
(pmc) pm_fsm_startup
(pmc) reg pm.s_setpoint_rpm <rpm>
...
(pmc) pm_probe_const_inertia
Also look into Trouble Shooting page in case of you
getting any error codes in pm.fsm_errno.