Design On The Leveling Control System Of A Rhombic Four Wheel Cultivator Body

Sugarcane is the most important sugar crop in China,it is widely planted in Guangdong,Guangxi,Yunnan provinces where the cultivated land is dominated by hills and mountains.By Sugarcane mechanization technology,the efficiency of sugarcane production can be greatly improved and the labor costs can be reduced.At present,the researches of sugarcane mechanization were focused on sugarcane planting and harvesting fields,while there was little research on sugarcane field management mechanization technology.Due to undulating terrain and large slopes,there were many problems in the process of operation during the field management of sugarcane,such as difficult operation,poor quality and easy to tip over.This thesis was based on a rhombic four wheel cultivator independently developed by our research group.Based on the coordinate transformation,leveling theory and control theory,the theoretical analysis and scheme design of the vehicle body leveling control system of rhomboid four wheel cultivator were carried out.And the mathematical model was established and the performance of the control system was verified by software simulation.Finally,the software and hardware of the control system were designed.This research provided technical support for mechanization of sugarcane field management in hills and mountains.The main research contents and conclusions were as follows:(1)The scheme design of the vehicle body leveling control system of rhombic four wheel cultivator.The mechanical structure of the rhombic four wheel cultivator was analyzed and the limited inclination of leveling was set.The control of the vehicle body leveling of rhombic four wheel cultivator was abstracted as the transformation of its working plane from one coordinate system(vehicle body coordinate system)to another coordinate system(horizontal coordinate system).Based on the theory of coordinate transformation and the geometric relationship of the cultivator structure,the characteristics and application range of various leveling methods were compared.The center points fixed leveling method based on four-point leveling method was adopted as the control strategy of the control system.At last,the "virtual leg" problem was solved.(2)Modeling and simulation of the vehicle body leveling control system.The mathematical model of the vehicle body leveling control system was established and the transfer function of the system was derived and calculated.According to the mathematical model,the stability and dynamic response of the control system was analyzed through MATLAB / Simulink.The results showed that: The control system was stable but the response time was too slow to meet the design requirements.It was necessary to introduce a control algorithm to correct the system.(3)Design and simulation of the controller of vehicle body leveling control system.The classical PID controller was used to correct the control system,and response speed of the control system was improved obviously,but it was still not suitable for a time-varying or nonlinear system.Based on the theory of PID control and fuzzy control algorithm,a fuzzy PID controller of leveling control system was designed.Finally,the two controllers were simulated to obtain its step response curve,and we did some analysis of the simulation results.The results showed that: the fuzzy PID controller was equivalent to the classic PID control in response time,but its oscillation and overshoot were obviously smaller than the classic PID controller.The fuzzy PID controller also has the ability to adaptively adjust parameters.Therefore,the fuzzy PID controller designed in this chapter can achieve the best control effect required by this control system.Which means,the controller met the design requirements of the control system.(4)Hardware design of the vehicle body leveling control system.According to the requirements of the control system,the overall design of the control system hardware was carried out.PLC was determined as the controller of the control system.The I/O ports of the hardware circuit of the control system were reasonably allocated based on the selected components by the detection module,the execution module and the human-computer interaction system.(5)Algorithm and software design of the vehicle body leveling control system.According to the scheme of the control system and the design principle of modularization,in the SIMATIC SETP7,the LAD programming language was used to design the functional programs of the signal acquisition and conversion module,leveling algorithm module(leveling method,automatic leveling sub-module,manual leveling sub-module,fuzzy PID algorithm module),system alarm module,etc.And the human-computer interaction system module was designed and programmed through the MCGS configuration software.(6)Testing of the vehicle body leveling control system.The test stands of the rhombic four wheel cultivator was designed.According to the test stands of the rhombic four wheel cultivator,the whole machine model was established in MATLAB / Simulink,and then the simulation was carried out to verify the feasibility and correctness of the control system.The results showed that: After the control system was started,the inclination of the horizontal axes and vertical axes of the vehicle body of cultivator was always kept within [-1.5 °,1.5 °].The control system ran stably,fast in response and without obvious vibration.So,the control system met the design requirements.