| 果蔬采摘机器人末端执行器的柔顺抓取力控制 |
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| 引用本文： | 姬伟,罗大伟,李俊乐,杨俊,赵德安.果蔬采摘机器人末端执行器的柔顺抓取力控制[J].农业工程学报,2014,30(9):19-26. |
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| 作者姓名： | 姬伟 罗大伟 李俊乐 杨俊 赵德安 |
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| 作者单位： | 1. 江苏大学电气信息工程学院，镇江 2120133. 机械工业设施农业测控技术与装备重点实验室，镇江212013;1. 江苏大学电气信息工程学院，镇江 212013;1. 江苏大学电气信息工程学院，镇江 212013;2. 东南大学复杂工程系统测量与控制教育部重点实验室，南京210096;1. 江苏大学电气信息工程学院，镇江 2120133. 机械工业设施农业测控技术与装备重点实验室，镇江212013 |
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| 基金项目： | 江苏省博士后基金资助项目（1102110C）；东南大学复杂工程系统测量与控制教育部重点实验室开放课题基金（MCCSE2013A03）；江苏省高校优势学科建设工程资助项目（苏政办发〔2011〕6号） |
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| 摘 要： | 为了尽可能减小采摘机器人末端执行器在采摘过程中对果蔬的损伤,提出了一种基于广义比例积分(GPI,generalized proportional integral)的抓取力矩控制方法。首先,对由电机驱动的末端执行器建立模型,推导出电机输入电压与负载力矩之间的数学关系;然后,利用积分重构器设计GPI力矩反馈控制器,将力偏差转化为电机的输入电压控制。该方法不需要对力矩跟踪误差进行求导计算,避免了求导所带来的系统延时和噪声问题。仿真和实物抓取试验结果表明,采用GPI的末端执行器力矩控制对跟定信号的跟踪误差达到10-3量级,具有良好的力矩跟踪能力,与传统PI(proportional integral)控制方法相比,其控制力矩和电机控制电压输出平稳,降低了末端执行器抓取时对果蔬的损伤,无损采摘效率达到90%,比PI控制的采摘完好率高出8个百分点,适合于对果蔬的柔顺抓取控制。该研究可为果蔬采摘机器人无损采摘提供参考。
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| 关 键 词： | 机器人 模型 控制系统 末端执行器 广义比例积分 柔顺控制 |
| 收稿时间： | 2013/6/17 0:00:00 |
| 修稿时间： | 2014/3/28 0:00:00 |
Compliance grasp force control for end-effector of fruit-vegetable picking robot |
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| Ji Wei,Luo Dawei,Li Junle,Yang Jun and Zhao Dean.Compliance grasp force control for end-effector of fruit-vegetable picking robot[J].Transactions of the Chinese Society of Agricultural Engineering,2014,30(9):19-26. |
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| Authors: | Ji Wei Luo Dawei Li Junle Yang Jun and Zhao Dean |
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| Abstract: | Abstract: In order to minimize the harm due to robot end-effector grasp fruits and vegetables, a generalized proportional integral (GPI) output feedback control scheme is proposed in this paper. First, the study object is the end-effector with two fingers that mounted on the top of a rigid manipulator, force sensors are mounted at the root of the finger, the output force signal was obtained by a force sensor, treating the model of the end-effector as a particle model and gravity does not affect the dynamics of end-effector, so the effect of gravity can be disregarded in the modeling. The modeling of the motor and the end-effector respectively and combining them together, the integrated model of end-effector is obtained, the mathematical relationship between the motor input voltage, and the load torque is also obtained. Then, the designed integral reconstructor, taking ramp error into consideration, the system gains robust characteristics to the ramp error that consists of force tracking error and constant disturbance, the integral reconstructor does not change the characteristic of the closed-loop. The computation of time derivatives can cause many common problems, such as a noisy signal, output delays, etc. In order to avoid these problems, making full use of integral reconstructor to design GPI force feedback controller, the force deviation converted to the input voltage control of the motor, this way needn't to derivate torque tracking error, so avoiding system time-delay and noise problem results from derivation. Making use of simulation software of MATLAB, taking sine signal and ramp signal as reference forces respectively, the force trajectory tracking error and the force output are analysed, the simulation result shows that the unit of force tracking error is 10-3, the real output force trajectory is close to the reference force trajectory, only having a little disturbance in the beginning, the output force trajectory reach a steady tracking status within 1 s, then the real output force trajectory smoothly tracks the reference force trajectory. Simulation results show that the GPI torque control has good torque tracking capability, which can decrease the damage of fruits and vegetables caused by end-effector grasping, and it is suitable for compliance grasp control of fruit-vegetable. Generalized proportional integral controller was applied to a fruit-picking robot to grasp apples and pears, after several the experiment of grasping fruits, the experimental results indicated that the method has a good performance and the fruit-picking robot can grasp and release fruit steadily and harmlessly. The ratio of successful grasping is 90%. Comparing with the situation that adopted traditional proportional integral control, the damage of fruits and vegetables caused by the end-effector grasping is reduced, fulfilling the demand of fruit picking. The research can provide a reference for the nondestructive picking of fruit-vegetable picking robot. |
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| Keywords: | robots models control systems end-effectors generalized proportional integral compliance control |
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