| Cassava is one of the seven crops with a global output of more than 100 million tons.It is the main food crop of 1 billion people in the world.However,cassava planting machinery is not popular.Coupled with the characteristics of drought tolerance and poor economy of cassava,cassava is mainly planted in rugged mountains in China,which also brings great difficulties to the popularization of cassava agricultural machinery.Aiming at the problems of inconvenient adjustment of digging depth and unstable performance of the existing vibrating chain cassava harvester,resulting in high cassava damage rate and large machine loss,an automatic control method of cassava digging depth is put forward.The main contents are as follows:Firstly,understand the mechanized planting pattern and growth characteristics of cassava,and study the working principle and working environment of 4UML-130 vibrating chain cassava harvester.Therefore,the design requirements of vibrating chain cassava harvester are put forward,and the overall design scheme is put forward,including actuator,detection mechanism and controller.Secondly,the profiling mechanism is designed and analyzed,and the detection principle is described.Due to the large excavation depth of the excavation shovel,the ridge surface in front of the excavation shovel produces a large length of uplift,which brings difficulties to the measurement.Therefore,a multi-sensor joint indirect measurement method is designed.The profiling mechanism is designed,and the maximum slope angle that it can walk safely is obtained through mechanical analysis and simulation.To avoid resonance,the modal analysis of the mounting plate of the profiling mechanism is carried out,and the first four natural frequencies are obtained.Avoiding these frequencies can reduce the amplitude and reduce the detection error.Finally,the sensor is selected.Then,the overall design of the hydraulic system is carried out,the mathematical model of the hydraulic system is established,and the stability is analyzed.According to the performance of tractor and the stress condition of the cassava harvester,the working pressure of hydraulic system is 10 MPa.Select the appropriate hydraulic cylinder,oil pip e,electromagnetic proportional directional valve and shunt and collecting valve according to the flow of the tractor.The mathematical models of hydraulic cylinder and electromagnetic proportional directional valve are established to obtain the open-loop transfer function of the system,and the Bode diagram of the system is drawn to analyze its stability.Then,the component selection of the control system and the simulation are carried out,as well as the programming of the integral separation fuzzy PID control algorithm in PLC.For the traditional control algorithm is difficult to get fine results,an integral separated fuzzy PID control algorithm is proposed.The simulation results show that the effect of integral separation fuzzy PID control algorithm is better.The principle of the algorithm is applied to Siemens 1200 PLC,and an integral separated fuzzy PID control algorithm based on look-up table method is compiled.Finally,indoor and field experiments are carried out.In order to better show the control effect,a set of simulated ridge mechanism is made in the indoor experiment.The step response and sinusoidal response tests are carried out to test the control effect of the control system.The field experiment takes the actual excavation depth as the index to evaluate the actual control effect of the control system. |
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