Electric Treadmill Digital Dc Drive System

In recent years, with the improvement of the people's living standard and enhancement of the consciousness of health-training, treadmill, one of the most important health-training equipments, is becoming more and more popular. Permanent-magnet DC servo motors are widely used in traditional treadmill driving systems. However, its inner deficiency-limited capability, big noise and low reliability because of its mechanical commutator and the brush, leads us to search for a kind of new drive motor with low noise, high efficiency and reliability instead of DC motor. Permanent-magnet brushless DC motor(BLDCM), which is more and more sophisticated with the development of the power-electronics and micro-control technique, takes on the advantage of small volume, light weight, high efficiency, low noise, big capacity and high reliability. As a result, it is significant to research on the application of brushless DC motor to the treadmill driving system.In this paper, a solution of building a speed-adjustment system for brushless DC motors with HALL position sensors based on TMS320LF2407A is presented. The new family of DSP enables cost-effective design of intelligent controllers for brushless motors. They can fulfill more conditions, configure fewer system components, lower system cost and increase performances.First of all, in this paper, the main formulas of brushless DC motor is deduced and its mathematical model is built. Based on this, the speed-adjustment principle and the solution for brushless DC motor are studied.Secondly, a digital solution with position loop, speed loop and c urrent loop is proposed. The system uses the TMS320LF2407A DSP as a microprocessor. The inverter is composed of the IR2130, which is a 3-phase bridge driver with a single power supply. The 6N137, Photoelectric Coupler, is used for transmission for the signal of PWM. And the control circuits are mainly composed of the state-detecting circuit of the HALL position sensor, the current-detecting circuit and the protection circuits. The protection circuits are used for over-circuit protection, under-voltage protection, over-voltage protection and overheating protection. Many EMC methods are adopted throughout the design of hardware to enhance the system's stability.Then, the software program is coded in assemble language of DSP and C language. The structure of the software of the whole design is composed of the main routine and the interrupt service subroutines. The main program is used for the initiation of the chip and other initiations. The interrupt service subroutines are used for converting of the phases, detecting and regulating speed and current, and system protection, etc..Finally, based on the theory analysis, the experiment is processed, and the result proves the reliability of the design of the system.