| The tractor is the basic machine of during agricultural production, and it has been widely used in the field operation and in agricultural transportation production. With the improvement of the level of agricultural machinery and the development of the technology of mechanical and electrical integration, the tractor has become larger, more intelligent and more electronic-developed. The electro-hydraulic hitch system is the main electronic control system of the tractor. At present, the research on the electro-hydraulic hitch control system of high-power wheeled tractor is mainly focused on three aspects:traction control, position control and traction position combined control. On the contrary, research on vibration control is relatively smallrare. High speed of the high-power tractor will inevitably cause the vibration aggravation of vibration. In fact, the reducing vibrations problem of large-power tractor plays a decisive role to ensure its driving safety and comfort. The project is studying investigates the vibration characteristics and active vibration control methods of the electro-hydraulic hitch system by both in theory and through experiments. The purpose of the research is to improve the vibration performance of high-power tractor, which specifically includes the following aspects:(1)Study and analysis the structure of each components in the tractor with electro-hydraulic hitch system and the interaction between them of the tractor with electro-hydraulic hitch system, these components. In addition, the complete mathematical model of low frequency vibration of in the high-power wheel tractor with electro-hydraulic system in during the transportation process caused by two kinds of road excitation was established for the first time. Mainly achievements include:both the kinematics and the dynamics analysis of the hitch equipment and the tractor, the road excitation model, and the mathematical model of the hydraulic system. Finally, the vibration of the tractor is accurately described presented in the form of a number of nonlinear differential equations.(2)Set up a Simulink co-simulation model of the tractor vibration system with electro-hydraulic hitch system under the no-control condition based on the mathematical model. Then two kinds of the vibration response curve of the tractor that with the farm equipment and the curve of the tractor without equipment on it under the same road excitation are simulated. The simulation results are analyzed in time domain, in frequency domain and as well as in the time frequency analysis method. Thus, as a result, low-frequency vibration characteristic of the tractor with electro-hydraulic hitch system and the influence of hanging equipment on the tractor vibration characteristics are obtained theoretically.(3)Two kinds of road excitation vibration test of the tractor with electro-hydraulic hitch system was carried on and the vibration data was acquired via Lab VIEW. Analyze the experimental data statistics through a variety of vibration analysis methods and then low-frequency vibration characteristics of the tractor with electro-hydraulic hitch system and the influence effects of the hanging equipment on the tractor vibration characteristics was obtained from practice. The test results are compared with the simulation results, which verify verifiedproved the correctness of the mathematical model.(4) In combination with the mathematical model of the hydraulic system and the flow characteristic test results of the hydraulic system of the high-power tractor, its input and output rules are obtained; The correspondence relationship between the vertical acceleration of the farm implement and the vertical force of the lower pull rod’s hinge point of the electro-hydraulic hitch system was obtained from the simulation results and test data. According to the influence of the hitch mechanism on the vibration characteristics of the tractor and the nonlinear characteristics of the system, an innovative effective control algorithm which only depends on a traction force sensor and a position sensor of electro-hydraulic hitch system and does not attach other vibration sensors was innovatively designed, and the effectiveness of the this control algorithm is validated by computer simulation.(5) Choose the K60 development plate provided by LanZhou company to develop vibration system controller. The main chip of the development plate is MK60DN512ZVLQ10 from freescale company Kinetis series and design damping control program in the Keil development environment. Select and install appropriate sensors, actuators, and filters, and various calibrate the sensors. The vibration control system of the tractor with electro-hydraulic hitch system is finally established. In order to analyze and evaluate the performance of the vibration reduction control system, the comparison tests were carried out to verify the performance of the system. |
PDF Full Text Request