Absolute positioning technology for analytical encoders

An encoder is a device commonly used in measurement and control systems to achieve precise position detection by converting position information into digital codes. In many industries, such as machinery manufacturing, robotics, automation control and other fields, the absolute positioning technology of encoders is widely used.

Absolute positioning technology means that the encoder can output a unique coding value at each position. Through this feature, absolutely accurate position measurement can be achieved. Compared with incremental encoders, absolute encoders can avoid the problem of position loss or position deviation, and can achieve accurate position detection without the need for an initialization process.

The following takes a commonly used absolute encoder, the magnetic absolute encoder, as an example to analyze its working principle and provide specific code examples.

The magnetic absolute encoder uses the interaction of the magnetic field sensor and the magnetic scale to achieve absolute positioning. The magnetic code bits on the magnetic scale are divided into several equally spaced magnetic poles. Each magnetic pole has a different magnetic pole direction. The position is determined by detecting changes in magnetic field intensity and magnetic pole direction measured by the magnetic field sensor on the scale.

The specific code examples are as follows:

#include <SPI.h>

const int chipSelectPin = 10; // 定义片选引脚
const int numPoles = 10; // 定义磁极数
const float resolution = 360.0 / numPoles; // 计算每个磁极的角度

void setup() {
  SPI.begin(); // 初始化 SPI
  pinMode(chipSelectPin, OUTPUT); // 设置片选引脚为输出模式
}

void loop() {
  int angle = readEncoder(); // 读取编码器的角度值
  Serial.println(angle); // 打印角度值到串口
  delay(1000); // 延时1秒
}

int readEncoder() {
  SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE0)); // 设置 SPI 参数
  digitalWrite(chipSelectPin, LOW); // 选中编码器

  SPI.transfer(0x10); // 发送读取命令
  byte highByte = SPI.transfer(0x00); // 读取高8位
  byte lowByte = SPI.transfer(0x00); // 读取低8位

  digitalWrite(chipSelectPin, HIGH); // 取消选中编码器
  SPI.endTransaction(); // 结束 SPI

  int encoderValue = (highByte << 8) | lowByte; // 将高8位和低8位合成一个16位的编码值
  int angle = map(encoderValue, 0, 4095, 0, 360); // 将编码值映射到0-360度的角度范围

  return angle;
}

The above example code demonstrates how to use the SPI interface to read the angle value of the magnetic absolute encoder. First, initialize the SPI parameters through the SPI.beginTransaction() function, then select the encoder and send the read command. Next, read the encoded value in order of high and low bits and uncheck the encoder. Finally, the encoded value is mapped to the angle range through the map() function and the read angle value is returned.

The absolute positioning technology of the encoder has a wide range of advantages in practical applications. Whether it is an industrial automation production line or a robot control system, encoders can be used to obtain position information in real time and accurately control the motion trajectory. By deeply understanding the working principle of the encoder and mastering the corresponding code implementation, we can better apply and optimize this technology and improve the accuracy and stability of the system.

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