Research And Development Of Electric Forklift And Electric Control System

The electric forklift has advantages of low noise, high efficiency, easy operation, energy conservation and environmental protection, etc. It’s more and more widely applied in the modern logistics industry, and has a tendency to gradually replace the traditional internal combustion forklift. The core technology of the electric forklift is the electric control system, so the study of the electric control system has real economic and social benefits.Based on the study of the internal electrical system of the electric forklift produced by Tailifu machinery and equipment(Qingdao) Co., LTD, this paper is to develop a full AC electric control system, which is compatible with the original electrical system. The electric control system consists of three units: the keyboard display unit, the intergrated control unit and the power dirve unit. The keyboard display unit is a human-computer interaction platform, the intergrated control unit is the control center of the whole system, and the power dirve unit is the output mechanism of the system.The keyboard display unit is developed based on the STC12C5410 SCM, and carries the dedicated LED driver chip MC14489, which adopts higy-speed SPI serial communication. The keyboard display unit has characteristics of strong anti-interference ability, easy operation, etc. The intergrated control unit is mainly composed of the control circuit and the signal detection circuit. The control circuit is built based on two pieces of dsPIC30F4011 microcontroller. To improve the reliability of the control circuit, the pulse blocking circuit is designed in the MCU peripheral circuit. The signal detection circuit is mainly to achieve the collect function of switching value, speed setting, bus voltage, current amplitude and motor speed. The power drive unit is composed of the power supply circuit, the drive circuit and the main circuit of inverter. The main circuit of inverter is characterized by low voltage and high current, the working voltage is 48 V, the maximum working current is 600 A. In order to achieve the high current technical indicator, this paper uses four power MOS transistors for shunting current to increase the current capacity of the inverter.The software programming is composed of the keyboard display unit software, the main control software and the auxiliary chip software. This paper adopts a slip frequency control algorithm based on SVPWM, which can arbitrarily control the slip frequency directly related to the torque and current. The control algorithm can improve the dynamic and static performance and the ability of restricting overcurrent of the system, and make its speed control performance close to the DC motor double closed loops speed regulation system. The system adopts the improved SVPWM algorithm, which is unique, small amount of calculation and easy to be achieved by programming.The experimental results show that the function of each part of the electronic control system has been achieved. The entire system is safe, reliable, and stable performance. And the experiment obtains good results.