| China’s logistics industry has continued to grow in the past decade,forklift handling as an important part of the rapid growth of the domestic forklift industry.However,in recent years,the shortage of fossil energy in the world has frequently been on the hot search.Meanwhile,the low efficiency and pollution emission of fuel forklifts have made the electrification of forklifts a trend.With the decrease of battery cost and the continuous improvement of lithium battery energy density,domestic and foreign manufacturers are more inclined to invest in the research of electric forklift.At present,when the load of forklift truck drops when carrying goods,the gravitational potential energy of goods and door frame is lost at the throttle valve of hydraulic system.Therefore,it is of far-reaching significance to recycle this part of energy and improve the energy utilization rate and endurance level of electric forklift truck.n this paper,the lifting electric drive system of electric forklift truck is taken as the research object,and the lifting and descending actions of the door frame are studied respectively:1.The driving motor control algorithm is studied when the forklift door frame is lifted with load to improve the anti-jamming ability and current utilization rate of the motor;2.2.When the door frame of forklift truck drops with load,the energy recovery system is designed to recover the gravitational potential energy of the door frame and load and store it for reuse in the next lift.According to the performance and working characteristics required by the hydraulic lifting system of electric forklift,the motor is selected as the driving motor,the mathematical model of the motor is analyzed,and the vector control is selected and realized in Simulink.The classical control theory method was used to set the parameters of the motor current loop and speed loop PI regulator,then the fuzzy algorithm was used to optimize the parameters of the PI regulator,and the Simulink model was built to verify the speed and torque results.The simulation results show that the fuzzy algorithm improves the anti-interference performance and adjustment time of the motor.Finally,the motor reluctance torque is used to improve the motor current utilization rate,and the MTPA algorithm is used to achieve the simulation model in Simulink.The simulation results show that the optimization can improve the motor response speed and antiinterference ability,and the current utilization rate is increased by 5.95%.In order to avoid energy loss at throttle valve during the recovery process,an energy recovery system based on excitation DC generator is designed.The system controls the electromagnetic torque of the generator through the excitation controller,and finally controls the load falling speed.The Simcape module of Simulink is used to build the energy recovery system model and the hydraulic model of forklift lifting system.The speed control and recovery efficiency of the energy recovery system are verified by simulation.The simulation results show that the excitation controller can control the load drop rate stably,and the energy recovery rate is 55.4%at full load,54.1%at half load and 36.1%at no load.On the basis of the energy recovery system,the paper designs the electricity electricity recovery recycling system and the energy distribution scheme,and stores and redistributes the electricity recovered from the generator reasonably.Supercapacitor,DC/DC,relay and other electronic device models are built in Simulink to form the forklift working system together with the motor and energy recovery system.According to the international forklift truck energy consumption testing standards,two forklift truck working conditions,"international standard working condition" and "single stacking working condition",analyze the power consumption of the two working conditions.The results show that the endurance is improved by 58.77%under standard conditions and 4.5%under single stacking conditions. |
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