Research On Slip Adaptive Control Of Electron-hydraulic Hitch Of Tractor

The control of the slip of the Electron-hydraulic hitch directly affects the uniformity of the tilling depth,that is,the quality of tilling is affected,and the tractor’s tractive efficiency is also affected.Under the condition of ensuring the stability of tilling depth,the slip control of Electron-hydraulic hitch is the requirement for the development of precision agriculture,and it is alos one of the key technical issues for the automation and intelligent control of Electron-hydraulic hitch.Based on this,the paper aimed at improve the tractive efficiency of plow unit and ensure the uniforminty of tilling depth as the goal,and studied the slip adaptive control method of Electron-hydraulic hitch of plow unit under plowing state.Fristly,the paper theoretically analyzed the relationship among slip,tractive force and tractive efficiency,and factors affected the tractive efficiency of plowing unit,a tractive efficiency prediction model based on slip and soil load coefficient was established,and the accuracy of the model was verified by experiments.Based on this,an ANN(Artificial Neural Network)optimal slip identification model with actual slip and tractive efficiency as parameters was established.The analysis results showed that the ANN optimal slip identification model could identified the optimal slip when the tractive efficiency of the plow unit is maximized according to the actual slip and tractive efficiency.Secondly,established the dynamic model of plow unit was established,the characteristic parameters of plow unit that represent the tilling conditions when the optimal slip identification and slip adaptive control were analyzed,and the plow unit state parameters measurement method and measurement error correction method of the plow unit state parameters were discussed.The slip measurement method was analyzed.The slip was estimated online using multi-parameters Kalman fusion filter.The direct and indirect measurement devices for tilling depth were designed and the causes of indirect and direct measurement errors of tilling depth were discussed.Kalman and linear fitting were used to correct the direct and indirect measurement errors of tilling depth respectively.The correction results showed that the fitting could reduce the deviation of the tilling depth measurement,and Kalman prediction could eliminate the noise of the measured value of tilling depth.The influence parameters of implement draft were analyzed.Based on the analyzed parameters,the ANN model and multivariate regression model were established to predict the implement draft in the horizontal direction,and the performances of the models were analyzed.The results showed that the ANN model could learn the nonlinear relationship between implement draft and its influencing factors,and the prediction performance was better.Thirdly,the ANN fuzzy and ANN fuzzy PID controller for the slip adaptive control of electrically controlled hydraulic hitch were designed,and the performance of the controller were simulated.The simulation results showed that both the fuzzy and fuzzy PID control could control the slip at the optimal value,and the slip control required only a small engine torque to exert a large driving force and improved the tractive performance of the plow unit.However,when single fuzzy control is applied,throttle opening would have large oscillation and mutation,and the convergence was relatively low.Fuzzy PID control has better effect and faster response.Finally,the paper carried out target slip control and slip adaptive control experiment and data analysis.The experiment results showed that the actual slip and the tiling depth fluctuate greatly when the target slip control,which can neither guarantee the smooth operation of the unit nor guarantee the tilling quality.The slip adaptive control could identified the optimal slip at which the tractive efficiency maximizes and maintain the slip at the maximum by adjusting the engine load characteristics.The slip adaptive control not only guarantees the constant tilling depth,promotes the development of precision agriculture,but also improves the tilling efficiency and tractive performance.