Motorola M68HC08 Reference Manual page 44

BLDC Motor Control
Designer Reference Manual
44
Freescale Semiconductor, Inc.
The best commutation was get with Advance_angle:
60Deg*1/8 = 7.5Deg
which means Coef_HlfCmt = 0.375 at Running state
with default s/w setting
Per_Toff[n+1] = Per_ZCrosFlt*Coef_Toff and Per_Dis minimum
Coef_Toff = 0.375 at Running state, Per_Dis = 150
with default s/w setting
Per_ZCros0 <-- Per_ZCros[n]
T_ZCros0 <-- T_ZCros[n]
T2*[n] = T_ZCros[n] + HlfCmt[n]
• If no back-EMF zero crossing was captured during preset
commutation period (T2P[n] then Corrective Calculation 1. is
made:
T_ZCros[n] <-- CmtT[n+1]
Per_ZCros[n] = T_ZCros[n] - T_ZCros[n-1] = T_ZCros[n] - T_ZCros0
Per_ZCrosFlt[n] = (1/2*Per_ZCros[n]+1/2*Per_ZCros0)
HlfCmt[n] = 1/2*Per_ZCrosFlt[n]-Advance_angle =
Coef_HlfCmt*Per_ZCrosFlt[n]
The best commutation was get with Advance_angle:
60Deg*1/8 = 7.5Deg
which means Coef_HlfCmt = 0.375 at Running state!
Per_Toff[n+1] = Per_ZCrosFlt*Coef_Toff and Per_Dis minimum
Per_ZCros0 <-- Per_ZCros[n]
T_ZCros0 <-- T_ZCros[n]
• If back-EMF zero crossing is missed then Corrective Calculation
2. is made:
T_ZCros[n] <-- CmtT[n]+Toff[n]
Per_ZCros[n] = T_ZCros[n] - T_ZCros[n-1] = T_ZCros[n] - T_ZCros0
Per_ZCrosFlt[n] = (1/2*T_ZCros[n]+1/2*T_ZCros0)
HlfCmt[n] = 1/2*Per_ZCrosFlt[n]-Advance_angle =
Coef_HlfCmt*Per_ZCrosFlt[n]
The best commutation was get with Advance_angle:
60Deg*1/8 = 7.5Deg
which means Coef_HlfCmt = 0.375 at Running state!
Per_ZCros0 <-- Per_ZCros[n]
T_ZCros0 <-- T_ZCros[n]
• Where:
T_Cmt = time of the last commutation
T2 = Time of the Timer 2 event (for Timer Setting)
T_ZCros = Time of the last zero crossing
T_ZCros0 = Time of the previous zero crossing
Per_Toff = Period of the zero crossing off
Per_ZCros = Period between zero crossings (estimates required
commutation period)
Per_ZCros0 = Pervious period between zero crossings
Per_ZCrosFlt = Estimated period of commutation filtered
BLDC Motor Control
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DRM028 — Rev 0
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