Motorola M68HC08 - Manual (Page 152)

User Guide
Designer Reference Manual DRM028 — Rev 0
152 User Guide MOTOROLA
SPEED_MIN_RPM determines the minimal desired speed. It must be
changed for any motor accommodation. The minimal speed is also
determined by the back-EMF zero crossing technique. Usually:
(EQ 6-11.)
Therefore, for low speed requirements minimal speed
SPEED_MIN_RPM must be evaluated experimentally.
NOTE: SPEED_MIN_RPM can be evaluated with PC master software tuning file
tuning_bldc.pmp.
Minimal PWM Duty cycle limit [-]:
/* CAN_CHANGE_11: */
#define DUTY_PWM_MIN 0.250
Range: <0,1>
DUTY_PWM_MIN determines minimal PWM duty cycle limit, and in
this way it restricts minimal voltage on the motor.
Therefore, DUTY_PWM_MIN must be changed if its default setting
creates a higher voltage than is physically necessary to run with a
speed close to SPEED_MIN_RPM.
CAUTION: If the motor is unable to run down to the speed set in SPEED_MIN_RPM,
then decrease DUTY_PWM_MIN constant.
Speed PI regulator constants:
/* MUST_CHANGE_13_EXPER: */
#define SPEED_PIREG_P_GAINSCALELEFT 0
Range: <0,8>
/* MUST_CHANGE_14_EXPER: */
#define SPEED_PIREG_P_GAIN 128
Range: <0,255>
where the current regulator proportional gain is:
(EQ 6-12.)
/* MUST_CHANGE_15_EXPER: */
#define SPEED_PIREG_I_GAINSCALERIGHT 0
Range: <0,8>
/* MUST_CHANGE_16_EXPER: */
#define SPEED_PIREG_I_GAIN 64
SPEED_MIN_RPM (0.07 to 0.5)SPEED_MAX_RPM =
KP SPEED_PIREG_P_GAIN*2
SPEED_PIREG_P_GAINSCALELEFT
=
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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