How is the heart rate algorithm of the smart bracelet implemented?

Heart rate detection is the core selling point of smart bracelets. Consumers are most concerned about the accuracy of these functions, which is also the most troublesome problem for smart bracelet manufacturers. Because according to the current technical level, no one can achieve 100% or close to 100% accuracy. Ah? Such a big error! Yes, but this step counting error will not have any impact on life and body, but the heart rate error will still have some impact! People are in various states such as walking, running, sleeping, etc., and the conditions for step counting are different in these states! Therefore, simply counting the number of steps will definitely bring a long difference! A good algorithm must take all these factors into consideration!

Regardless of the performance, let's first take a look at how the pedometer function is implemented? Later, we will explain how the heart rate algorithm is implemented! I worked with students to implement and test the pedometer algorithm, and the learning process made me very satisfied. Teaching and learning are also reflected in the process. However, there are very few such students, and it takes several years to meet a very hard-working person.

The core component of pedometer is the accelerometer, which can sense the direction and magnitude of an object's movement). This sensor can sense acceleration or vibration in different directions through a capacitive accelerometer. The three-dimensional motion state sensor is divided into three-axis and six-axis. The three-axis sensor generally records data when swinging the arm, while the six-axis sensor improves the data recording and accuracy of the movement through walking, running, cycling, and climbing stairs. The following figure is a schematic diagram of the three-axis sensing direction!

All smart products must be based on the regular state of stage time. Without regularity, there is no intelligence. The following figure shows the three-dimensional acceleration of the human body during movement, where a=x+y+z. x, y, and z are the acceleration magnitudes in the three-dimensional directions. Vector sum! Just a simple addition? Is this how data is used in practice? The specific calculation method will be given below the article! Only with practice can you have the right to speak!

Digital filtering: refers to the process of using digital devices to process signals through certain algorithms, filtering out signals in a certain frequency band, and obtaining new signals. What are the methods of digital filtering? Exponential filtering, median filtering, average filtering, etc.