Motorola M68HC08 manual Speedminrpm = 0.07 to 0.5SPEEDMAXRPM

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

User Guide

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:

SPEED_MIN_RPM = (0.07 to 0.5)SPEED_MAX_RPM (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:

KP = SPEED_PIREG_P_GAIN*2SPEED_PIREG_P_GAINSCALELEFT (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
Designer Reference Manual		DRM028 — Rev 0
152	User Guide	MOTOROLA
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