A control method to prevent falling from a treadmill based on STM32 microcontroller and ultrasonic transducer

A treadmill is widely used at home or health entertainment centers, its safety is essential. If the body gait is not appropriate or the inclination degree of the body is too large, movement instability may be caused or even be fallen down from a treadmill. This paper presents an intelligent electronic control method based on STM32 microcontroller and ultrasonic transducer, which can real-time automatically control the treadmill velocity through detection of the upper body position or the tilt angle of human body. Control components are mainly STM32 microcontroller, signal detection unit and motor control unit. The STM32 microcontroller accepts ultrasonic signals of detection unit from input port and digitally processes these signals, and then drives the motor control unit to adjust the operating state and speed of motor through output port. The emitting and receiving of signals are realized by using the ultrasonic T/R module. The main control method is using multiple ultrasonic transducers to measure the interval time between the emitting signals and receiving signals to detect the distance between the subject's position and treadmill or the tilt angle of the body. These collected measurement data are digitally processed by some correlation calculation algorithm, in which some noise and interference signals can be excluded to avoid false judgments. The preliminary test results show that the upper limit of the distance error is less than 8 mm for a 43 kHz ultrasonic wave, and the tilt angular error of human body is approximately 1 to 5 degrees. Therefore the proposed control method and correlation calculation are effective and feasible.