Software Design
Data Flow
DRM028 — Rev 0
Designer Reference Manual
MOTOROLA
Software Design
81
5.3.6 Process Commutation Time Calculation, Corrective Calculation 1, Corrective
Calculation 2
These processes provide calculations of commutation time intervals
(periods) (
Per_ZCros
,
Per_ZCrosFlt
), from captured time (
T_Cmt
,
T_ZCros
,
T_ZCros0
), and sets Timer 2 with variable
T2
. These
calculations are described in
3.3.1.5 Starting — Commutation Time
Calculation
and
3.3.1.3 Running — Commutation Time Calculation
.
5.3.7 Process Desired Speed Setting
The desired speed, held in register
Speed_Desired
, is calculated from
the following formula:
Speed_Desired
=
Sp_Input
*
Coef_Speed_Inp
/255 +
Speed_Min_U8
5.3.8 Processs Speed Control
The general principle of the speed PI control loop is illustrated in
Figure 5-3
.
Figure 5-3. Closed Loop Control System
The speed closed loop control is characterized by the feedback of the
actual motor speed.
The actual motor speed is calculated from zero crossing period:
Actual motor speed = 256*
Per_Speed_MAX_Range
/
Per_ZCrosFlt_T2
(
OutReg_U8
)
(256*
Per_Speed_MAX_Range
/
Per_ZCrosFlt_T2
)
-
REFERENCE
SPEED
(Speed_Desired)
SPEED
ERROR
PI
CONTROLLER
PWM
DUTY CYCLE
CONTROLLED
SYSTEM
ACTUAL MOTOR
SPEED
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