Motorola M68HC08 Starting Commutation Time Calculation, Computation coefficients are different

Freescale Semiconductor, Inc.

BLDC Motor Control

Used Control Technique

T_Cmt[1] T_Cmt[2]		T_Cmt[3]
T2[1]		T2[2]	T2[n]
n=1	n=2		n=3

Semiconductor, Inc.

Per_CmtStart

T_ZCros[0]

2*Per_CmtStart

ZERO CROSSING DETECTION SIGNAL

ZERO CROSSING DETECTION SIGNAL

ZERO CROSSING DETECTION SIGNAL

Per_Toff[n]

2*Per_ZCrosFlt[n-1]

COMMUTATION IS PRESET

COMMUTATED AT PRESENT TIME

NO BACK-EMF FEEDBACK WAS RECEIVED

CORRECTIVE CALCULATION 1

T2*[n]

COMMUTED WHEN CORRECT

BACK-EMF FEEDBACK

Per_HlfCmt[n] RECEIVED AND EVALUATED

T_ZCros[n]

T2**[n]

COMMUTATED WHEN BACK-EMF

ZERO CROSSING IS MISSED

CORRECTIVE CALCULATION 2.

Per_HlfCmt[n]

Freescale

Figure 3-20. Calculation of the Commutation Times During the Starting

(Back-EMF Acquisition) State

3.3.1.5 Starting — Commutation Time Calculation

Even the sub-states of the commutation process in the starting (back-EMF acquisition) state remain the same as in the running state. The required commutation timing depends on application state (starting state, running state). So the commutation time calculation is the same as that described in

Running — Commutation Time Calculation, but the following

computation coefficients are different:

coefficient Coef_HlfCmt = 0.125 with advanced angle Advance_angle: 60Deg*3/8 = 22.5Deg

	at Starting state!
DRM028 — Rev 0		Designer Reference Manual
MOTOROLA	BLDC Motor Control	49

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