| Condition monitoring technology for hydraulic system is an effective method, which can guarantee hydraulic equipment to run efficiently under reliable condition. At present, most condition monitoring instruments are not portable enough, and parameters which are disturbed easily are difficult to be measured. Besides, there is few special instruments to monitor the power of hydraulic system. In view of characteristics of mechanism, electrics, liquid as well as disadvantages of existing instruments, the on-line monitoring instrument for hydraulic power system based on single chip is designed and the prototype instrument is manufactured.The monitoring parameters of the instrument include motor parameters (current, voltage, power factor, motor power) and dynamic parameters of hydraulic system (pressure, flowrate, temperature, output power of pump). By analyzing motor-pump coupling model about hydraulic power system, the monitoring approaches for hydraulic system are given by monitoring motor condition. The line voltage, line current and power factor are monitored by the quasisynchronous sampling method, then, motor power is calculated. Using the testing combination module, the pressure, flowrate and temperature of hydraulic system are monitored and the output power of pump is also calculated.The data sampling circuit board whose core is AT89S52 is designed. The sampling procedures for pressure, flowrate, temperature, motor current and voltage are programmed. The host monitoring software is designed by VisualBasic6.0, which can display, save data and make alarms. Experiment results indicate that the sampling frequency of instrument is eligible and the measure precision grade is 1.5. This instrument can accomplish condition monitoring for hydraulic system. The study result indicates: the motor-pump mathematical model about the hydraulic power system, the quasisynchronous sampling method, the design of hardware and software meet on-line monitoring requirements of hydraulic power system.
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