【作者】 梁喜凤；

【导师】 苗香雯； 崔绍荣；

【作者基本信息】 浙江大学 ， 农业生物环境与能源工程， 2004， 博士

【摘要】 果实收获是农业生产过程的重要环节，为提高劳动生产率和作业质量，降低劳动强度，改善工作环境，实现收获作业机械化、自动化和智能化，基于番茄生物学特性与栽培方式，设计了7自由度番茄收获机械手，并进行了机构优化设计与仿真试验。 (1)根据番茄生物学特性、栽培方式与番茄收获机械手机构型综合原则，确定了番茄收获机械手是由2个移动关节、5个转动关节构成的7DOF冗余度机械手；以工作空间和杆件结构尺寸为目标建立了综合优化目标函数，获得了机械手结构参数的优化解，并根据实际工作方式确定了机械手结构尺寸参数。 (2)采用Denavit-Hartenberg方法设定了番茄收获机械手杆件坐标系，通过齐次变换建立了正运动学与逆运动学模型，获得了番茄收获机械手雅可比矩阵，为机械手运动学分析、仿真与性能优化奠定了理论基础。 (3)利用包络解析法和数值方法，并结合机械手末杆位姿图，获得了番茄收获机械手腕点工作空间、总工作空间与灵活工作空间。腕点工作空间满足机械手设计要求，末杆长度与末端执行器长度对总工作空间与灵活工作空间有较大影响，随着其长度增大，总工作空间增大，但相应的灵活工作空间减小，机械手灵活性降低；为减小工作空间中空腔区域体积，杆件3、杆件5的长度与关节5的转角应合理选择。 (4)采用蒙特卡洛方法对番茄收获机械手末端执行器位置空间进行仿真。结果表明，工作空间主截面区域能够覆盖番茄生长范围，内部工作点密集且分布均匀，满足番茄采摘要求。 (5)利用MATLAB／SIMULINK同时进行番茄收获机械手正运动学与逆运行学仿真试验。正运动学仿真结果表明，末端执行器加速度与给定加速度一致，速度与时间基本呈线性变化且斜率小；位置曲线变化平滑，无振动现象，满足正常工作要求。逆运动学仿真结果表明，关节1、3、7速度最小范数解、位置与加速度均满足运动要求，无异常波动现象，能够实现控制；而关节2、4、5、6速度在仿真时间t=[4.7197s，5s]时速度、位置和加速度出现异常振荡，关节运动失控，从而引起系统振动，其运动性能需进一步改进。 (6)通过雅可比矩阵奇异值分解进行番茄收获机械手奇异性分析，并采用阻尼最小二乘法对机械手运动中的奇异位形进行处理，使番茄收获机械手最小奇异值远离零点，各关节运动速度、位置和加速度运动无异常波动，解决了机械手在奇异位形处某些关节运动无法控制的问题。 (7)利用冗余度机械手自运动特性，综合机械手可操作度、避关节极限和避障等性能建立了番茄收获机械手综合性能优化目标函数，并采用零空间优化法进行性能优化。结果表明：机械手各关节速度、位置、加速度均变化连续且平滑，幅值与梯度变化小，无奇异现象，避免了关节越限，解决了由各关节位置的波动而引起的关节运动失控问题，改善了番茄收获机械手运动性能，系统工作平稳，为运动控制奠定基础。浙江人学博_l:学位论文摘要 (8)采用迭代法和优化方法对番茄收获机械手进行PTP运动规划与仿真试验。结果表明，番茄收获机械手能够由初始位置沿预定路径运动至目标位置且可以同时进行性能优化，机械手具有较高的灵活性，成功避开了作业空间的障碍物，奇异位形附近运动规划误差小，各关节位置变化连续、平滑，均能满足运动精度要求。但番茄收获机械手运动误差还受到关节极限等因素影响，运动规划中避关节极限等问题仍需进一步研究。更多还原

【Abstract】 Fruit harvesting is an important process in agricultural production. To raise labor productivity and working quality, reduce working density, improve working environment and realize harvesting mechanization, automatization and intelligentization, a seven-degree-of freedom tomato harvesting manipulator was designed based on tomato phytological characteristics and cultivating methods. Simultaneously, mechanism analysis and simulation were performed on kinematics and performances of the manipulator.(1) Mechanism type-synthesis and dimension-synthesis of the tomato harvesting manipulator were investigated according to some criteria of tomato physiological characteristics and cultivated methods and type-synthesis regulation. A redundant manipulator consisting of 2 prismatic joints and 5 rotational joints was determined for tomato harvesting. At the same time, a synthetic object function for optimizing design was set up based on workspace and link length. Optimal solutions of the manipulator mechanism structure and motion parameters were obtained. Furthermore, the rational structural parameters of the manipulator were determined according to the practical production environment and working mode.(2) Link coordinates of the manipulator were set up by Denavit-Hartenberg method. Simultaneously, forward kinematics and inverse kinematics was modeled through homogeneous transformation and Jacobian matrix was reached as well, which provided the basis for kinematics analysis, simulation and performance optimization.(3) The wrist workspace (WW), the accessible workspace (AW) and the dexterous workspace (DW) of the manipulator were obtained using the enveloping analytical method, the numerical method and the end link configurations. It was indicated that the WW satisfied the design requirements of the manipulator. The AW expanded with the increasing of the end link and the end-effector length, while the DW and the dexterity of manipulator reduced accordingly. In addition, the length of link 3 and link 5 and the angle range of joint 5 should be chosen reasonably in order to decrease the cavum volume in the workspace.(4) The position workspace of the end-effector was simulated by the Monto Carlo method. It was showed that the position workspace of the end-effector covered the growing range of tomato fruits completely, in which the working points were distributed density and equably and can satisfy the picking requirements.(5) Simulation of forward kinematics and inverse kinematics was performed on the tomato harvesting manipulator simultaneously by MATLAB/SIMULINK. The forward kinematics simulation results showed that accelerates of the end-effector obtained from simulation was equal to that of the given. The relation between the velocity of the end-effector and simulation time was nearly linear with gentle tangent slope, and the position varied with time continuously and smoothly without any vibration during moving. It was observed from the inverse kinematics simulation results that the position, accelerate and velocity minimum-norm solution of joint 1,3,7 of the manipulator were controllable with no abnormal fluctuates, which satisfy the motionrequirements. However, the position, the accelerate and the velocity of joint 2,4,5,6 of the manipulator varied with time irregularly with high efficiency during the simulation time t=4.7197s~5s, which would make the joint uncontrollable and result in the vibration of the manipulator system, hence the kinematic performance of manipulator should be improved.(6) The analysis on Singularity configurations of the manipulator were investigated by the singular value decomposition of Jacobian Matrix, which was treated with the damped least-square method in the motion. From the results obtained it was indicated that the minimum singular value of manipulator calculated by the damping Jacobian matrix were far from zero position. Velocity, position and accelerate of all the joints of manipulator moved regularly, consequently the problem that the joint of mani更多还原