Research And Design On The Drive System Of Electric Forklift Based On The IFOC

As the energy crisis is increasingly serious, technologies of efficacy enhancement are always the hotspots in the field of scientific community, so the research of development of efficient electric forklift which can replace the inefficient internal combustion forklift becomes one of the important research projects. Because of the particularity of the motor generic inverters could not be applied to meet the control requirements of the electric forklift, and the key technology of controller is currently dominated by a few foreign companies, so it indicates high economic efficiency and broad market prospects to develop the high-performance electric forklift controller. Research on electric forklift drive system is the core of researching the electric forklift. Therefore, aiming at the electric forklift drive system, the research and design are made based on the Indirect Field Oriented Control (IFOC).Firstly, the working principle of the traditional SVPWM modulation technique is analyzed. It is found that the current waveform had evident distortion at the zero crossing by simulation and experiment on the traditional SVPWM modulation technique which adds dead zone time. A new modulation technique which could compensate the dead time by analyzing the causes of current distortion is proposed, and the dead zone’s impact on voltage vector detailed is analyzed, an concept of the transitional switching space vector is given, and the calculation method of switching time is illustrated. The simulation results turns out the new SVPWM modulation method which adopts dead-time compensation could effectively reduce the harmonic distortion.Secondly, the mathematical model and coordinate transformation of asynchronous motor are introduced. Control system based on indirect field oriented vector is projected. Current loop and speed loop of the control system is designed, the simulation of IFOC system is built, and the simulation results are analyzed. The simulation results show that the control system possesses good dynamic response and stability precision.Thirdly, the full-order observer is designed through analyzing the mathematical model of induction motor, and then simulation models of non-speed sensor vector control system based on full-order flux observer is built on Matlab/Simulink software. A large number of simulation experiments are conducted on the simulation models. The result indicates that the non-speed sensor vector system possesses good dynamic response and stability precision, estimated speed can track the actual speed well and possesses preferable robustness for system load changes.Finally, the new vector control modulation method with dead-time compensation is experimented on the developed experimental prototype. The current waveform has been significantly improved, the motor operation becomes more stable and it verifies the feasibility of the design of the system.