| As an important indoor fitness equipment, motorized treadmill has won a rapt attention of people at its first appearance. With similar mechanical characteristics to brushed ones, rare earth permanent magnetic brushless direct current motor(BLDCM) is thriving on low power motor driving occasions with the advantage of higher power density and reliability, lower noise and loss.This paper firstly introduces the basic structure of BLDCM and analyzed its operating principle and method of speed regulation in detail. Mathematic model of BLDCM is established in the 3-phase ABC coordinates, the relationship with brushed ones is also proposed. The simulation model of the driving and controlling system is established on the basis of the former research. The theoretical feasibility of speed-current double closed-loop control algorithm in treadmill driving and controlling system is verified according to the load characteristics of treadmill with simulation.Secondly, the total hardware structure is proposed according to the functional requirements of an intelligent motorized treadmill. The inverter and its driving circuit are mainly studied, and the problems existing in inverters using bootstrap driving method is also analyzed. The microcontrollerμPD 78 F1213 is taken as the core of central control circuit while an intelligent power module (IPM) as the core of main power circuit. The software is designed using modular programming principle and foreground-background software architecture based on the designed hardware. Functions of system initialization, speed and gradient regulation are fulfilled in software design, while the information in the controlling frame from the up controller is also decoded by the method of state machine.At last, the designed control system is tested on an actual motorized treadmill platform based on the design of hardware and software. The results of experiment indicate that the system introduced in this paper works well with high reliability and safety. |
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