| Dynamometer card is an important method in analyzing working status of deep-well pump, pumping unit and sucker rod. It is often obtained by means of traditional tie-line style at present. However, it has many disadvantages, such as bulky instruments, high rate of broken wire, and serious locally wearing out etc., which brings inconvenience in the field testing operation.A scheme of portable dynamometer card testing and analysis system based on accelerometer is proposed. The stroke is calculated indirectly to avoid the inherent disadvantage of tie-line style. Meanwhile, the system has the features of convenient carrying and easy operating. A user-defined data transfer protocol is used to receive mass data in the dynamometer card analysis software, and the software provides many functions such as dynamometer card area computation, load diagram, displacement diagram and so on. The main research results are summarized as follows:The portable dynamometer based on accelerometer chip and ultra low-power microcontroller (MSP430) has been designed. An algorithm of displacement calculation based on double integrals to measure stroke has been used. The hardware circuit system with data acquisition, data storage, data transmission and human-machine interaction has been achieved. Each software function based on MSP430 microcontroller has been programmed and debugged.A hybrid algorithm of acceleration signal filtering has been presented, which is suitable for testing stroke of beam and belt pumping units. This algorithm has improved the accuracy of stroke measurement, and it also determines the upper dead center and bottom dead center accurately. The algorithm is realized on portable dynamometer based on MSP430.A communication protocol between the MCU and the PC is designed to guarantee efficient data transmission. The data analysis software has the functions of displaying several modes diagram, arranging dynamometer card by time and unit name, and comparing the same unit at different times etc. The software is developed by Visual Basic platform.The system has been tested in laboratory. Field experiments have been carried out in pumping unit. Experimental results have shown that the designed system is more accurate and better compatible for measuring the beam and belt pumping units. The whole system has been working steadily, and meets the design requirements. |
