Motorola M68HC08 manual Bldc Speed Control and Calculation, Process Alignment Control

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

Software Design

This information is compared with the reference set point and the error signal is generated. The magnitude and polarity of the error signal corresponds to the difference between the actual and desired speeds. Based on the speed error, the PI controller generates the corrected motor voltage in order to compensate for the error. The speed regulator parameters (gain...), internal, and input/output variables are located in the structure PIParamsScl_U8_Speed.

The speed controller works with a constant execution (sampling) period.

The period is timed by timer 3, with the constant PER_T3_RUN_US.

PWM duty cycle is set for all six PWM channels according to regulator output, OutReg_U8. The maximum duty cycle is at OutReg_U8 = 255. The implementation is described in Implementation Notes — 5.6.3

BLDC Speed Control and Calculation.

5.3.9 Process Alignment Control

The process alignment control controls the current, Curr, using the PI regulator during alignment state (see 5.5 State Diagram). The dc-bus current is regulated to required value Curr_Align. The current regulator parameters (gain...), internal, and input/output variables are located in the structure PIParamsScl_S8_Curr.

The current controller works with a constant execution (sampling) period. The period is timed by timer1, with the constant

PER_CS_T1_US.

5.3.10 Processes Commutation and Zero Crossing Preset and Set

The processes commutation and zero crossing preset and set provides the BLDC commutation and zero crossing selection. Here the BLDC commutation means generation of the six step commutation which creates the voltage system shown in Figure 3-2. The required BLDC motor voltage system and commutation is provided using the MC68HC08MR32 PWM block.

The zero crossing selection means the selection of the required zero crossing phase as described in 3.2.4.2 Indirect Back EMF Sensing and

Designer Reference Manual		DRM028 — Rev 0
82	Software Design	MOTOROLA
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