Key Technologies Of Remote Ultrasound Robot Based On Tactile Perception And Virtual Environment

At present,medical robot related technologies are developing rapidly,especially in the field of ultrasonic scanning.With the continuous development of teleoperation and virtual reality technology,the remote ultrasonic robot is becoming more and more prominent in its application value.With the orderly advancement of hierarchical diagnosis and treatment,ultrasound departments continue to expand,and ultrasound itself has the characteristics of non-trauma,no radiation,no pain,accurate and rapid results,which makes the practical application of ultrasonic testing wider,the development of ultrasound department of specialization is becoming higher and higher,and the shortage of ultrasound doctors is becoming more and more obvious.In China,experienced sonographers are concentrated in large hospitals,and most rural areas are unable to perform ultrasound therapy effectively.To provide equal ultrasound treatment for these areas,a teleoperated robot was introduced in this study to assist in ultrasound examination.Starting from the virtual force representation system and virtual environment model mediated teleoperation control algorithm,this thesis studies the kinematics and dynamics,bilateral control algorithm,virtual environment,and tactile sensing technology of remote ultrasonic robot system.The contents are as follows:Firstly,aiming at the different configurations of the doctor-side and patient-side robot arms of the remote ultrasonic robot,the kinematics and dynamics modeling of the master manipulator Omega.6 and the kinematics and singularity analysis of the slave manipulator were studied respectively.According to the structural characteristics of the master hand,a kinematic algorithm based on a vector loop equation is proposed,which has the advantages of small computation and fast computation,and all explicit solutions of forward and inverse kinematics are obtained.According to the tactile feedback function of the master hand,a dynamic model was established based on the principle of virtual work,and a simplified method was proposed according to the characteristics of the mechanism,which ensured the real-time and fidelity of the force feedback.The forward and inverse kinematics model of the serial slave manipulator was established based on the D-H parameter method,which laid a foundation for prediction display in the virtual environment.Secondly,to solve the problem that the remote ultrasonic robot doctor can not get real touch perception,a virtual force perception reconstruction method based on the particle spring model was proposed.According to the characteristics of human soft tissue and skin deformation,a particle spring model was used to abstract the abdominal ultrasound region,establish a physical model of the ultrasound region,and study the collision detection algorithm between the virtual ultrasonic probe and the virtual plane.Finally,a deformation model that can realize virtual force reproduction was obtained.In terms of force feedback,a new virtual force calculation method is proposed based on Hunt-Crossley environmental contact dynamics model to obtain more real tactile feedback.With the help of the CAHI3 D development environment,the deformation of the virtual abdomen and real-time force feedback program was realized,and the virtual force perception of the main end was reconstructed by the master manipulator during the remote ultrasound.Thirdly,an incremental heterogeneous master-slave compliant control algorithm based on the hybrid force/bit control is proposed based on the virtual force perception reproduction system based on the particle spring model.According to the requirements of ultrasonic scanning,the force control of the probe direction of the manipulator and the tangential position of the human body were respectively carried out by using the information provided by the virtual force representation system of the main end,to realize the stable and accurate teleoperation ultrasonic process.In terms of compliance control,the force error is introduced into the position loop to improve the fit ability and force control accuracy of the ultrasonic probe when it contacts the human body.The security of the ultrasonic robot is analyzed comprehensively,and the pose limitation algorithm and safety protection mechanism are designed to ensure the safety and applicability of remote ultrasonic in various scenarios.Fourthly,an improved model-mediated teleoperation control algorithm based on a virtual environment is proposed to solve the problems of long-time delay and errors between the virtual force model and the real environment of the remote ultrasonic robot.Firstly,Unity3 D was used to establish a virtual simulation model of the robot arm at the doctor side,and the position and attitude of its end were controlled in real-time through the kinematic model to display in augmented reality.Aiming at the defects of existing environmental contact force models,this thesis proposes a continuously switching contact force model for complex human environments and uses the least square method based on an adaptive forgetting factor and self-perturbation mechanism for online parameter identification.The obtained environmental model parameters are used for force prediction,which further reduces the influence of long-time delay on teleoperation and improves the safety and transparency of master-slave control.Fifthly,to verify the effectiveness of a model-mediated teleoperation control algorithm based on the virtual environment,a complete set of the teleoperating ultrasonic robot system is built.For structured and unstructured scenes,experiments are conducted on the sponge and human body respectively.The results show that virtual reality technology can make up for the impact of the delay between the doctor and the patient,and the error between the virtual force and the actual feedback force obtained by the modelmediated teleoperation control algorithm is small,overcoming the influence of model error on teleoperation,and ensuring the doctor has real and accurate tactile feedback.To sum up,the virtual force representation system and the hybrid force/position control algorithm proposed in this subject can realize the remote ultrasonic function with immersion.Meanwhile,to solve the problem of the influence of long-time delay on teleoperation and haptic model mismatch,a model-mediated teleoperation control algorithm based on a virtual environment is proposed.It ensures the accuracy of tactile perception and the transparency of teleoperation under long delays.