Robust control of tomato picking robotic arm considering contact constraint

doi:10.13733/j.jcam.issn.20955553.2024.12.016

Abstract

Abstract:

Aiming at the problem of picking damaged fruits by the end effector caused by low positioning accuracy of the robotic arm, a finite time robust control method is designed. Firstly, the mathematical model of the picking robotic arm with frictional resistance and contact constraints was established, and the dimensions were reduced. Then, the tracking error and the contact constraint of the tomato picking robotic arm end position were taken as the control targets, and the terminal sliding surface was designed. Finally, the finite time Robust control law under the contact constraint was designed by using auxiliary parameters, and the angle error and end contact constraint error of the designed tomato picking robotic arm could converge to 0 in finite time that proved by Lyapunov function. The simulation results show that the designed robust control method can stably track the control command within 0.3 s, and the maximum tracking errors of joint rotation angle and contact force are only 0.3° and 0.08 N·m, respectively, which has better rapidity and accuracy. The results of picking tomatoes tests show that the proposed robust control method can achieve a maximum positioning error of only 0.19 cm at the end of the picking arm, and the maximum contact constraint error is only 0.06 N·m.

Key words: tomato picking, robotic arm, frictional resistance, contact constraint, terminal sliding surface, robust control

摘要： 针对机械手臂定位精度低导致的末端执行器采摘伤果问题，设计一种有限时间鲁棒控制方法。首先建立带有摩擦阻力和接触约束的采摘机械手臂数学模型，对其进行降维处理；然后将采摘机械手臂末端位置和接触约束的跟踪误差作为控制目标，设计兼顾两者的终端滑模面；最后利用辅助参数设计接触约束下的有限时间鲁棒控制律，并通过Lyapunov函数证明设计的番茄采摘机械手臂的关节角度误差和末端接触约束误差均能在有限时间内收敛到0。通过仿真试验结果表明，设计的鲁棒控制方法可在0.3 s内稳定跟踪控制指令，关节角度和接触约束的最大跟踪误差分别仅为0.3°和0.08 N·m，具有更优的快速性和准确性。通过对番茄采摘测试的结果表明，提出的鲁棒控制方法可使采摘手臂末端的最大定位误差仅有0.19 cm，接触约束的最大误差仅为0.06 N·m。

关键词: 番茄采摘, 机械手臂, 摩擦阻力, 接触约束, 终端滑模面, 鲁棒控制

CLC Number:

S225
TP241

Yao Yunlei, , , Li Hui, . Robust control of tomato picking robotic arm considering contact constraint[J]. Journal of Chinese Agricultural Mechanization, 2024, 45(12): 101-108.

姚云磊, 李辉, . 考虑接触约束的番茄采摘机械手臂鲁棒控制[J]. 中国农机化学报, 2024, 45(12): 101-108.

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