C8051F020在直流无刷电机转速控制中的应用

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"AN1175应用笔记主要探讨了C8051F020微控制器在直流无刷电机转速控制中的应用，详细介绍了软件和硬件的配置方法。关键词涉及MCU（微控制器）、直流无刷电机以及转速控制。" 在现代电子设备和自动化系统中，直流无刷电机（BLDC）由于其诸多优势而备受青睐。相较于传统的有刷直流电机，无刷电机的主要优点包括： 1. 无机械换向器：这使得无刷电机能够运行在更高的速度下，减少了因换向器磨损导致的性能限制。 2. 电压降减少：在有刷电机中，电刷的电压降是电机损耗的一部分，而在无刷电机中则不存在这个问题。 3. 动态响应改善：无刷电机的反应速度更快，因为没有换向器对电枢电抗电压的限制，可以减小转动惯量，提高特定扭矩下的速度响应。 4. 散热效率高：热量主要集中在无刷电机的定子部分，而有刷电机的热量主要在转子，因此无刷电机更易于散热。 5. 噪音与电磁干扰降低：无刷电机的运行噪音和电磁辐射比有刷电机低。无刷电机根据定子的相数和转子的磁极数，以及转子和定子相对位置的不同，可以分为多种类型。本应用笔记主要关注的是三相无刷电机。两相电机虽然结构简单，但在某些性能上可能不如三相电机。在控制无刷电机的转速时，C8051F020微控制器扮演着核心角色。MCU负责处理电机的传感器数据（如霍尔效应传感器），通过检测电机的位置来精确控制电机的电流换相，从而实现高效的转速控制。软件部分通常涉及到PID（比例-积分-微分）控制算法，用于实时调整电机的输入电压，确保电机按照预期的速度运行。硬件配置则包括MCU的选择、驱动电路的设计以及必要的保护机制，如过流和过热保护。 C8051F020是一款高性能的微控制器，内置模拟和数字功能，适合于复杂的电机控制任务。其强大的计算能力、丰富的外设接口和内置的ADC（模数转换器）使其能够轻松处理电机控制所需的实时计算和信号处理。本应用笔记详细阐述了如何利用C8051F020微控制器实现直流无刷电机的转速控制，涵盖了从硬件设计到软件编程的全过程，对于理解和实施无刷电机控制系统具有重要的参考价值。

AN1175

To resolve these drawbacks, there are other methods

that can be used to map the stalled position of the rotor

and immediately start commutating from that point.

For many motors, the simple method of a time out on

the zero-crossing forcing a commutation will result in

satisfactory performance; therefore, this is the method

for this application note.

Zero-Crossing Detector

The zero-crossing system consists of switching the

inputs to a comparator synchronously with the

commutation and monitoring the output of the

comparator. The comparator output is filtered with a

majority detector. This filter is table-driven and looks for

a transition from mostly 1’s to mostly 0’s. Once the

transition is detected, the commutation can take place.

Zero-Crossing Majority Detector

In a noiseless system, zero-crossing events can be

determined by observing when the output of a

comparator sensing the back EMF voltage transitions

from one to zero. Switching high currents at high

voltages introduces a tremendous amount of noise into

the system (see Figure 3). Determining when a zero-

crossing event occurs in such an environment requires

some sort of filtering to mitigate the noise. Filtering with

discrete components adds too much delay to be useful,

especially at high motor speeds. Discrete filters also

vary with temperature, which adds to the complexity of

delay management. A better filter is one that has a

predictable delay that does not vary with the

environment.

A majority filter is one that can be implemented in

software. Software filters have a predictable and fixed

delay that is not affected by the environment. The filter

uses a series of comparator output samples to detect a

zero-crossing event. Zero-crossing is said to have

occurred when most of the first half of the samples are

ones and most of the last half of the samples are zeros.

For a six-sample window, a zero-crossing event is

detected when two or three of the first three samples

are ones and two or three of the last three samples are

zeros. Table 1 illustrates all the possible combinations

that satisfy these criteria.

FIGURE 3: TYPICAL ZERO CROSSING

WITH PWM GENERATED

NOISE

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StephenGui

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