Research On Multi-point Variable Parameter Compliance Control Of Redundant Robot In Human-robot Safety Interaction

With the rapid development of robot technology in recent years,human-robot collaboration/human-robot integration has become a mainstream trend in the market,and its broad application prospects have been extended to aerospace,manufacturing,healthcare,home furnishings.As one of the representatives of service robots,the development goal of mutual redundant smart robots is to build a human-robot integrated work mode in a shared work environment with humans.How to enable robots to safely and reliably coexist with humans or the environment,and realize safe and friendly interactions between humans and robots,has become a focus and research hot spot for researchers in robot field.Currently,there has been a lot of research by domestic and international scholars on the implementation of safe human-robot interaction with redundant robotic arms in specific scenarios,and some research advances have been made.However,for human-robot interaction in complex scenarios,especially in the process of multi-contact interaction,there are many uncertainties and complex nonlinear coupling issues such as human-robot shared working environment,perception,dynamics,and control.This poses new challenges for safe human-robot interaction and compliant operation,and is one of the key issues that need to be urgently addressed.Therefore,the current technological development is still insufficient to support manipulators to perform relatively fine manipulation tasks in the unstructured,narrow space of human-robot shared work spaces,and there is still room for improvement and innovation.In light of this,this paper is important for the study of human-robot safety interactions in dynamic narrow-space scenarios,especially the flexible control of redundant manipulator in multi-point contacts.?In this paper,the human-robot mutual aid redundant dexterous manipulator as the research object,aiming at the scientific issues and key technology of obstacle avoidance and flexible manipulation in human-robot safety interactions,from the obstacle avoidance realization based on the visual skeleton,the trajectory planning under the contact of the redundant robotic arm end-effector and the multiple-point contact variable parameter compliant control in several aspects has been thoroughly studied.(1)Based on the analysis of the structural configuration of the seven degrees of freedom redundant robot arm,the inverse motion is analyzed using a geometric solution method parametrized by the arm angle,which is optimized iteratively based on the avoidance joint limits.In addition,the equivalent dynamics of the seven degrees of freedom humanoid flexible-joint manipulator is modeled.The kinematic simulation analysis and dynamical simulation validation of the redundant manipulator were implemented using Sim Mechanics/ADAMS and other related software.(2)Research on the control method of multiple virtual end-effectors based on 3D visual sensing skeleton extraction.In view of the problem of the dynamic obstacle response of the redundant robotic arm in the human-robot safety interaction,the skeleton extraction is realized through the 3D visual sensor,and the object bounding box is constructed by combining with geometric primitive,so as to realize the real-time evaluation of the human-robot safety distance.On the basis of the construction of equal effect Jacobian at the virtual end and reaction force,the damping parameters are adjusted in real time,and the simulation analysis and comparison verification were carried out with ROS/Gazebo and other related software,so as to realize the safe interactive and flexible obstacle avoidance operation at the dynamic level.(3)Study on sliding mode variable impedance control method of virtual force estimation based on interaction intention.For the difficulty of controlling both trajectory tracking accuracy and force compliance of manipulator end,based on the establishment of flexible contact dynamics at the end of human-robot interaction,by adding virtual force estimation based on interaction intention,hyperbolic tangent function was introduced into sliding mode control,and through stability analysis,realizes the force flexibility control and trajectory tracking contact with the human-robot interaction end.Matlab/Simulink simulation verifies the effectiveness of the control algorithm in the aspects of high-precision tracking and force compliance when man-machine terminal contact.(4)The multi-point variable parameter compliance control strategy based on the human-robot safety interactive flexible contact dynamics equivalent twin system is studied.Aiming at the problem that the dynamic coupling mechanism of multi-point/arbitrary point contact is not clear in the human-robot safety interaction process of redundant manipulator in narrow space,the RFVE arbitrary point contact dynamics model is proposed,and the contact force conversion is realized by combining the skeleton principle,and the flexible contact dynamics equivalent twin system of redundant manipulator is constructed.Based on this system,the impedance stiffness coefficient was adjusted in real time by combining the velocity of the virtual end of the manipulator,the manipulator joint angular velocity under the redundant degree of freedom motion distribution was optimized,and the multi-point contact variable parameter compliance control of human-robot safety interaction was carried out.The feasibility of multi-point contact dynamics model and variable parameter compliance control method of human-robot interaction redundant manipulator is analyzed by ROS system simulation.(5)The experimental verification was carried out with mycobot cooperative manipulator as the experimental object.By using ROS robot system,experiments were carried out on the methods in the process of human-robot safety interaction,such as multi-virtual end-effectors algorithm based on vision,the sliding mode variable impedance control algorithm based on interaction intention,and the multi-point variable parameter compliance control strategy based on the equivalent twin system of flexible contact dynamics.The effectiveness and practicability of the compliance control method proposed in this paper are verified by in-depth analysis of the experimental results.