Motorola M68HC08 - Manual (Page 55)

BLDC Motor Control
Application Control
DRM028 — Rev 0 Designer Reference Manual
MOTOROLA BLDC Motor Control 55
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
Speed_Max_RPM and Speed_Min_RPM variables. These are chosen
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 *Per_Speed_MAX_Range/Per_ZCrosFlt_T2
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
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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