Research And Design Of Overload Limiter Without Load Sensor

With the socio-economic development,there is an increasing demand for cranes.At the same time,crane also has developed towards the direction of large-scale,high-speed and automation.Crane is a typical mechanical equipment which has more potential risk factors and greater chances of accident occurance. Every year,there are a large number of accidents caused by crane operation at home and abroad,such as equipment damagement and even casualties.Therefore, development of the crane's overload protection device is urgently required..Basing on native and foreign research on present Crane Safety Monitor System,and making the full use of the latest technical achievements in electronics,computer, sensing telemetry control,we put forward a new method of measuring crane load, that is,measuring directly the asynchronous motor's output power from which the load weight of cranes could be educed.Described in this article forklift without load sensor system limited mainly by the current sensors,transmission unit,main control unit is composed of three parts. Control unit is ARM7(LPC2138) as the core components of the transmission unit of data transmission to determine the deal to make a variety of control actions;and LCD modules through the LCD display data in real time;In addition,the unit also has the SD Card storage functionality,can be easily transferred data.Transmission unit is MCU as the core components mega16 also selected A/D conversion chip AD1674 and True RMS converter chip AD736,can be collected quickly and accurately rotor RMS current and frequency;and through the RS-485 total line to the data acquisition and processing to the main control unit.Current sensor is used in KTC-B Series Hall Current Sensor,the sensor measuring range up to 900A,the rated output of 4V,measured the frequency of 0-25KHZ.The system has some conventional functions,such as detecting,controlling, overrun alarming,it adopts SD card to store data and has a human visual interface. Compared with the traditional Crane Overload Limiter,the system depends on Hall Current Sensor rather than gravity sensing,which can greatly reduce the Mechanical installation intensity,and the weight measurement accuracy will not be impacted by mechanical levelness.Therefore,the development of sensing lifting limited system without load has an important practical significance.