Motorola M68HC08 manual PerSpeedMAXRange and zero crossing period PerZCrosFltT2

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

BLDC Motor Control

Application Control

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

DRM028 — Rev 0		Designer Reference Manual
MOTOROLA	BLDC Motor Control	55
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