| Modular robot manipulator(MRM)is a robot with multiple modules,which can be added or subtracted modules according to the requirements or variable tasks.In addition,these modules have standard electrical and mechanical interfaces,each of which integrates communication unit,drive unit,control unit and sensing unit.Furthermore,robot has the property of ‘high precision',and human has the characteristics of rapid judgment,thus the advantages of robot and human can complement with each other to complete the task together.When humans and robots are coupled together to carry out operations,these two individuals with self-determination and autonomy carry out information exchange,which is called physical human-robot interaction(p HRI).Benefit from the advantages that modular robot can be added or subtracted modules according to the requirements,these kind of robots are applicable to p HRI in complex fields because of the properties that are oriented to varied tasks and different human partners.Therefore,it is an urgent requirement to investigate an appropriate control method that realizing completely high performance position tracking in p HRI.The decentralized control strategy adopts the local signal control of the system,which will result in that the failure of a few actuator information will not lead to the failure of the control of the whole system.Therefore,the decentralized control strategy is more suitable for modular robot system.In this paper,the decentralized control strategy of modular robots in the context of physical human-robot interaction is studied as follows:(1)The mechanical structure of harmonic drive,the principle of kinematic transmission theory and torque transmission theory are introduced,and the compliance model of harmonic drive is established by considering the flexible deformation.By using the idea of torque feedback technology,the modular robot dynamics model based on joint torque sensor is established.Meanwhile,the dynamic characteristic is analyzed,and the state space equation is established,which lays the foundation for the design of control strategy and the established harmonic drive compliance model-based dynamic model of modular robot in the following chapters.(2)In the context of p HRI,the decentralized robust control strategy of modular robot is proposed to realize that the robot show the property of compliance and follows the movement of human when the robot follows the motion of the collaborator.Different from the traditional human-robot interaction control method that relies on the precise dynamic model and centralized control scheme,the decentralized robust control method is proposed based on the human motion intention,which is estimated through radial basis function neural network.By only using local dynamic information of each joint,a decentralized robust controller is designed to deal with various model uncertainties and joint trajectory tracking problems.The uniformly ultimately boundedness of tracking error is verified under the principle of Lyapunov theory.Eventually,the experiments are verified the efficiency of presented modified decentralized robust controller.(3)The harmonic drive compliance model is introduced,which combines with the proposed torque feedback-based dynamics model of modular robot.The harmonic drive compliance model-based modular robot dynamic model is established,which avoids the installation of joint torque sensors.The installation of joint torque sensor and sixdimensional force sensor will increase the cost burden,and furthermore,the installation of these sensors will lead to more measurement errors and calibration errors,which will cause the decline of the overall accuracy of the MRM.In this term,a harmonic drive compliance model-based decentralized integral sliding control method of modular robot manipulators is proposed under the situation of physical human robot interaction.Different from the method of human motion intention estimation and control strategy of the second part,in this investigation,the decentralized integral sliding interaction control is implemented that using only position measurements of each joint module.Based on the harmonic drive compliance model,a method for identification of human motion intention was proposed in p HRI.On this basis,the decentralized integral sliding control scheme is presented to achieve high performance of position tracking and ensure the security of interaction.The uniformly ultimately boundedness of tracking error is verified under the principle of Lyapunov theory.Eventually,the experiments are verified the efficiency of presented modified decentralized robust controller. |
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