Research On Key Technology Of Tractor Power Shift Transmission Control System

The power shift transmission controls the shift clutch to achieve load shifting.It has the advantages of no interruption of power during shifting,which can reduce shifting time,simplify driver operation and improve production efficiency,and is widely used for transmission systems of large and medium power tractors.Compared with vehicle automatic shift control,the difficulty of controlling tractor power shift transmission is that the power shift transmission should achieve load shifting,and the load of tractor is a random load which is directly related to working mode and environment.The sudden change of tractor driving force before and after shifting,frequent shifting,and power cycling and excessive skid caused by unreasonable clutch engagement will cause adverse effects on power shift.In view of the above problems,CAN bus is applied to share multiple sensors signals,the state identification algorithm is applied to identify the tractor's running state and load state,and on this basis,the shifting rules and the clutch engagement rules suitable for the dynamic characteristics of the load are worked out to achieve smooth load shifting.This paper has completed the following four aspects:The important parameters of the control system are measured and calculated in this paper.The goal of this part is to help the power shift transmission control system to accurately perceive and judge the operating environment.The parameters which are more important and cannot be directly measured in the process of tractor power shift transmission include:the driving wheel slip ratio and the random load characteristic.The tractor slip rate directly reflects the tractive characteristics of the tractor.The difficulty of the measurement is that it is difficult to ensure the measurement accuracy.The characteristics of random load reflect the characteristics of tractor load.Although the characteristics of random load do not require high accuracy,the difficulty of measurement is that the off-line statistical value of load characteristics can not meet the needs of real-time control.Considering the characteristics and measurement requirements of these two parameters,an adaptive data fusion algorithm with noise observer is proposed in this paper,the online estimation of slip rate of tractor driving wheels is realized by multi-sensor data fusion technology,the eigenvalues of the random load are obtained by the adaptive filtering algorithm which contains two different sampling frequencies.Study on the law of power shift.The purpose of this part of the work is to determine the appropriate shift timing and target gear for the power shift transmission control system.In this paper,a dynamic model of a tractor under the action of random load and a mathematical model of three parameter shifting law that can realize the equal driving force before and after the shift are established.On the basis of the research model,an adaptive shift rule correction strategy is proposed,which takes the load fluctuation coefficient,the load steady state value change rate and the throttle change rate as the environment parameters,and obtains the speed correction parameters through the fuzzy algorithm.The revised shift regulation can be used to identify the operating state of the tractor flexibly and automatically select and maintain the high efficiency of the gear.When the tractor needs to shift,the shift rule can realize no obvious delay in shift,without changing the position of shift point,and the driving force will not change suddenly before and after shift.At the same time,the shift rule can automatically shield the random shift and ensure the stability of the transmission,which provides a precondition for the subsequent clutch's smooth shift control process.The dynamic shift clutch engagement law can be generated online to adapt to the real time working conditions.The goal of this part of the work is to optimize the shift execution process,that is,the power cycle does not appear during the shift process,and the sliding friction power of the clutch is the lowest.The randomness of the load of the tractor determines that the clutch separation and engagement law needs to be generated online to adapt to the time-varying working environment.Therefore,by establishing a unified dynamic model with load shifting process,the influence mechanism of clutch law on gear shifting process is analyzed,and the formulation principles of engagement and separation rule of power shift clutch are obtained.The range of torque variation slope of the clutch during sliding is derived,and a clutch engagement rule with minimum sliding power is proposed.The online generation of the joint separation law of the power shift clutch is realized.The related controller and sensor bus node and message transmission protocol stack are designed.The purpose of this part of the work is to provide information transmission guarantee for the whole power shift control system.The power shift control process involves a variety of technologies,such as multi-sensor data fusion technology,adaptive shift rule modification and online shift rule setting technology,etc.These technologies require the controller to read and process a large amount of environmental information and vehicle status information in real time.In this paper,the transmission controller is used as communication node,and the electric control network of tractor is built by using CAN bus technology to simplify the control system.According to the control and communication requirements of power shift transmission,the related control and sensor nodes are designed,and the CAN bus message transmission protocol stack based on ISO11783 standard protocol is designed.The data sharing between multiple ECU in the electronic control network of the tractor has been realized.