| The thesis is based on the national science and technology support program(project number: 2013BAH57F01).The purpose is to study the motion stability control strategy of agricultural foot mobile platform,and to enable it to complete the task of independent transportation and walking in mountainous,woodland,hilly and other slope fields,and it provides a theoretical basis for the functional and practical application of agricultural foot mobile platform.China is a country with a relatively less arable land,for some of the mountain,forest land and hilly farmland by wheeled agricultural machinery is not suitable for such work,often use the traditional manual farming field operations,reduces the working efficiency.Therefore,it is necessary to study the new mobile platform for rational and effective development and utilization of agricultural land.In this paper,the agricultural foot mobile platform can affect its operating performance due to the environmental rigidity of the pavement and the constant changes of the body posture during the operation of the complex field terrain.However,this article is to study the stationary control strategy of the agricultural foot mobile platform,it is based on the quadruped robot,and in order to solve the difference of the fuselage attitude stability of the agricultural foot mobile platform in the uneven road surface and slope walking,at the same time,the vibration of agricultural foot mobile platform in walking is reduced,the stability of foot force tracking control of agricultural foot mobile platform is guaranteed,and to improve the active flexibility of the leg of the agricultural foot mobile platform,and thus achieve the stationarity of its movement posture.This article mainly from the trajectory planning,kinematics analysis and three-dimensional slope posture and gait planning,force tracking control of hydraulic servo system and the prototype test analysis to the agricultural foot type mobile platform motion stability control strategy for research.The main research contents are as follows:(1)This paper introduces the principle of structure and analyze its kinematics of the agricultural foot mobile platform,using the D-H method,the kinematics model is established and the homogeneous transformation matrix to solve,and analyze the velocity and acceleration of their legs,establish Jacobi matrix,by foot end force relation with the change of the joints,at the same time,five-degree polynomial is used to plan the foot trajectory,providing the precondition for the steady-state walking control of the agricultural foot mobile platform.(2)In order to ensure the stationarity of the agricultural foot mobile platform in the field,the theoretical research on the horizontal attitude control strategy of the bionic quadruped mechanical dinosaur was carried out.At the same time,the planar Trot and the slope Walk were planned,and the simulation analysis was carried out by combining Matlab/SimMechanics and Matlab-Adams simulation.Results show that the agricultural foot mobile platform in gradually into the three-dimensional slope,the body posture can do in 2 ° ~ 4 ° continuous level transformation;And walking in the plane and three-dimensional slope of pitch and roll attitude Angle keep in-2 ° ~ 2 °,three-dimensional slope walking horizontal posture control strategy is verified and the effectiveness of the gait planning.(3)Due to the agricultural foot mobile platform adopts hydraulic servo system to control the leg joints,the essence of the foot force tracking is to analyze the terminal position force control of the hydraulic servo system.The hydraulic servo system has the problem of controlling nonlinearity and parameter time-varying,and the high quality agricultural foot mobile platform has a large load disturbance.Therefore,the single position control can hardly meet the need of walking stability when the agricultural foot mobile platform walks in different environmental stiffness and irregular pavement.Therefore,the impedance model is established by analyzing the force variation of the end position of the hydraulic servo system in contact with the environmental model.On this basis,this paper puts forward a composite particle swarm adaptive impedance control strategy,through the simulation analysis,and USES the cubic spline interpolation impedance parameters change with environment stiffness equation,at the same time on the terminal position force tracking steady-state error reason and its mathematical model is established,according to the force and the terminal end of the current position,using adaptive algorithm to estimate the environmental stiffness and environmental position,and compensate for the desired location and select the impedance parameters.Combined with the original impedance and fuzzy adaptive impedance control,using Matlab-Adams virtual prototype simulation and two connecting rod end serial mechanism platform for hydraulic servo system in different contact environment model in force tracking test,the results show that the control strategy proposed in this paper in the terminal position steady state error of 0 ~ 1;Through two connecting rod series mechanisms become expect force tracking test bench,in the expectation force changes,tracking the response time of 0.4 s,overshoot amount to 9%,that force tracking dynamic performance is good,to verify the composite particle swarm algorithm of the adaptive impedance force tracking control of hydraulic servo system is effective.(4)In order to validate the presented the running smoothness of the effectiveness of the control strategy for the foot end force tracking,slope walking posture stability,through the building and the design of the agricultural foot mobile platform for foot force tracking experiment prototype system test,the pitch attitude Angle and joint Angle change relationship between testing and slope walking posture,and analyze the test results,verify the running smoothness control level of force tracking control and attitude the practicability of the effectiveness of the control strategy and control system.Through the relevant research,it was improved agricultural foot type moving platform in the uneven road surface and slope surface movement stability,and large quadruped mobile platform for hydraulic drive about sports attitude stability control as reference for related research,as well as large bionics agriculture since the robot design and development to provide the reference. |
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