Control System Design Of Treadmill

Recent years, with the socioeconomic development and the improvement of people's living standard, people are increasingly concerned about the health of themselves. Fitness becomes a newly fashion, and fitness equipment industry has also gradually emerged a major consumer market. Electric treadmill as an important fitness equipment has been increasingly broad application, and has a great market prospects. Development of a multi-functional and high value-added electric treadmill is of great realistic significance.Treadmill control system is the core of treadmill running. It needs to have the function of the user interface, speed control of motor and so on. The paper studies for the treadmill control system in the goal of practical value, high comfort, high cost-effective and high reliability. The designed tasks are the hardware design of speed control system of brush DC motor, the design of cardiotach ometer and the software design of control system. The paper detailedly shows the whole design process of control system from theoretical analysis to the software and hardware design.First of all, in this paper, the main formulas and the working principle of permanent magnet brush DC motor are introduced. And the mathematical model of speed control system based on voltage negative feedback with current compensate is built. To creative propose a solution which is called "speed buffer" to increase the comfort of treadmill. Then we finish hardware design according to the control strategy.And then, the paper shows the hardware and software design of cardiotach ometer for treadmill. Heart rate is an important feedback signal of the health status, it is necessary for people to reasonable control the number of heartbeats in the time of fitness. Cardiotach ometer as an additional device of treadmill gradually becomes an important reference optional of treadmill. In this paper, heart rate measuring principle and design are detailedly introduced. Getting ECG signal of human hands through electrodes at the rails of treadmill, modifying it by the circuits of filter and amplifier, extracting R wave and shaping it, then we would get square waves which could be directly measured by microcontroller. In the design of hardware, 10-35Hz bandwidth in which mostly energy of R wave placed and there was less interference is magnified; in the design of software, several algorithms, such as conditioned filter, median filter, limiting filter and moving average filter, are used to hugely improve the accuracy of measurement.After that, with assemble language of ATmega32, the software program is written. The program includes the main routine and the interrupt service subroutines. The main program is used for the initiation of the chip, flags polling, events treatment, data calculation, keys treatment, buffers of display refresh and so on. And the function of heart rate control speed is realized based on cardiotach ometer. The interrupt service subroutines are used to treat events which need real-time, for example, data acquisition, keys scan, dynamic display, overload detection, etc.Finally, the experiment concerned about control system is processed based on the theoretical analysis, and the results prove that the design of the system is feasible.