AN1914 Freescale Semiconductor / Motorola, AN1914 Datasheet - Page 52

• Manufacturer Part Number: AN1914
• Description: 3-Phase BLDC Motor Control with Sensorless Back EMF Zero Crossing Detection Using DSP56F80x
• Manufacturer: Freescale Semiconductor / Motorola

Setting of SW parameters for other motor kits
11.2.5 Commutation Proceeding Period
#define x_CONST_PERPROCCMT_US 170.0 /* Period of Commutation proceeding [micros]*/
Notes:
#define x_CONST_PERPROCCMT
11.2.6 Commutation Timing Setting
Notes:
x_StartComputInit
x_RunComputInit
Coef_CmtPrecompLShft
Coef_CmtPrecompFrac
Coef_HlfCmt
Coef_Toff
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Commutation preceeding period is the constant time after motor commutation, when BEMF Zero
Crossing is not measured (until the phase current decays to zero).
The unit of this constant is 1 s.
The older versions of the software (SDK 2.2) used the constant with system units:
The unit of this constant is 1.777us. This constant is automatically calculated in newer SDK software
versions.
If it is required to change the motor commutation advancing (retardation) the coefficients in starting
and running structures need to be changed:
Both structures are in bldcadczcdefines.h.
The x_StartComputInit structure is used by the application software during Starting stage (see
Section
The x_RunComputInit structure is used by the application software during Running stage (see
Section
fractional and scaling part of Coef_CmtPrecomp
final Coef_CmtPrecomp = Coef_CmtPrecompFrac << Coef_CmtPrecompLShft
this final Coef_CmtPrecomp determines the interval between motor commutations when no BEMF
Zero Crossing is captured. The application SW multiplies fractional Coef_CmtPrecomp with
commutation period.
determines Commutation advancing (retardation) - the interval between BEMF Zero Crossing and
motor commutation
The application SW multiplies fractional Coef_HlfCmt with commutation period.
determines the interval between BEMF Zero Crossing and motor commutation
The application SW multiplies fractional Coef_Toff with commutation period
This constant needs to be lower than 1/3 of (minimal) commutation period at motor maximal
speed.
Normally this structure should not necessarily be changed. If the constants described in this
section need to be changed a detailed study of the control principle needs to be studied in
Section 5
Crossing sensing (MotorControl.pdf).
5.4.3).
5.4.2).
and SDK document describing algorithms BLDC motor commutation with Zero
DSP56F80x MC PWM Module in Motor Control Applications
Freescale Semiconductor, Inc.
For More Information On This Product,
100 /* Period of Commutation proceeding [1.7777us]*/
Go to: www.freescale.com