Motorola M68HC08 Reference Manual page 55

DRM028 — Rev 0
MOTOROLA
Freescale Semiconductor, Inc.
The Sp_Input variable is used for speed control. In PC master software
mode, it can be modified from PC master software (otherwise, it is set
according to speed potentiometer value).
Desired speed [rpm] =
Sp_Input/255*(
Speed_Max_RPM-Speed_Min_RPM) + Speed_Min_RPM
So, the required motor commutation period is determined by the
and
Speed_Max_RPM Speed_Min_RPM
according to which optional board and motor set by the BLDC control
MCU software.
The variable Speed_Range_Max_RPM determines scaling of the
speed variables.
The actual speed of the motor can be calculated from
Per_Speed_MAX_Range and zero crossing period Per_ZCrosFlt_T2:
Actual speed [rpm] =
Speed_Range_Max_RPM
The variable Commut_Rev can be used for calculation of the BLDC
motor commutation period:
Commutation Period [s] = 60 / Actual Speed [rpm] / Commut_Rev
The variable Curr_Range_Max_cA determines scaling of the current
variables. So, the actual dc-bus current is:
dc-bus current [A] = Curr / 256*Curr_Range_Max_cA / 100
BLDC Motor Control
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variables. These are chosen
*Per_Speed_MAX_Range/Per_ZCrosFlt_T2
BLDC Motor Control
Application Control
Designer Reference Manual
55