Research And Optimization Analysis Of Control Strategy For Electric Drive System Of Mining Truck

Large mining electric-wheel truck is an important transport equipment in open-pit mine transportation.Because of the strong carrying capacity,high mobility and high efficiency,it is widely used in the world’s open-pit mine.High-power AC(Alternating Current)drive technology as the key technology of mining electric-wheel truck is the core competitiveness of the worlds’ major mining equipment manufacturers’ products.As the core part of the AC drive system,the electric drive system control strategy turns the driving intention into the subsystems’ control targets,and controls the subsystems to have good working performance during the driving process.In this paper,the control strategy of the electric drive system for a 220t mining electric-wheel truck is studied to solve the problem of the dynamic performance requirement.A reliable control strategy is obtained.It is proved that the strategy can meet the requirement of the mining truck by the data of experiments.The construction of the typical duty cycle of the mining truck is studied,the control strategy is optimized according to the duty cycle,and the optimal control strategy of the electric drive system is obtained.Firstly,the research object’s electric drive system is analyzed.From the driving performance of the mining truck,the system power matching and the different driving conditions of the mining truck,the strategy are analyzed in order to meet the demand of the dynamic performance of the mining truck.The main framework of the control strategy is deduced.Then,the electric drive system is divided into two subsystems:power conversion system and traction system.The control strategies of the two subsystems are researched.For the power conversion system,according to the diesel engine performance curve and the rule of constant magnetic flux for the alternator,two following control rules are designed:the engine speed follows the accelerator pedal command and the DC(Direct Current)link voltage follows the engine speed.For the traction system,the torque control decision based on the logic threshold rule of the motor speed is designed according to the characteristics of the motor speed of the mining truck under different driving conditions,and the analytical relationship between the motor control target and the pedal instruction under different decision is determined.This paper also studies the judgment conditions and control decision about the special state in the driving process.The experiments data shows that the control strategy in this paper can meet the mining truck dynamic demand in working process.Then,for there are few researches about duty cycle of mining trucks,considering the importance of the duty cycle for the control strategy optimization analysis,this paper constructs the cycle by using the travelling analysis method.Based on the characteristics of mining electric-wheel truck,the kinematics sequences are divided and the appropriate characteristic parameters are chosen.Through the principal component analysis and density peak clustering analysis,the clusters of the kinematics sequences are obtained.A typical duty cycle for mining truck is built by combinating the sequences.All different clusters of the duty cycle can be used in the control strategy optimization.Finally,based on the duty cycle data,the control strategy is optimized.Through the analysis of the working data of the electric drive system,the most important of control points under different working conditions are deduced.By using the improved minimum distance classification method combined with the secondary judgment,the result of the condition recognition is used to guide the control decision.Based on the different control decision,the original control strategy is optimized.The optimization strategy re-planned the engine’s working curve to improve the fuel economy of the mining truck.At the same time,the driving intention analysis rules under different working conditions are made,so that the control target can meet the control points under the different working conditions.In addition,the speed range of the motor under different working conditions is limited to meet with the different conditions’ dynamic or handling requirements.