Haptic Perception And Display For Remote Soft-tissue Palpation

As one of the key technologies of Virtual Reality and Augmented Reality,haptic interaction not only helps users to touch and perceive virtual objects,but also allows them to perform active operations to complete the two-way interaction with the virtual environment.In recent years,with the development of 5G communication technology and Ultra-Reliable Low-Latency Communication technology,the realization of remote tactile reproduction is becoming possible.Among them,affected by large-scale infectious diseases,remote palpation technology has the most urgent need for realization.The remote palpation technology collects haptic perception on the patient's end,transmits it to the doctor's end via a wired or wireless network,and uses various haptic devices to redisplay it,thus completing the diagnosis operation while separating the doctor from the patient.It actually provides a new way for the diagnosis and treatment of contagious diseases.This research mainly focuses on remote soft tissue palpation technology,including tactile perception and acquisition using a handheld palpation joystick,as well as kinesthetic sense display and vibration tactile enhancement based on electromagnetic haptic device.The main research works of the thesis is as follows:1.Hand-held haptic sensing collection.Design a handheld palpation stick that integrates visual-inertial-pressure sensors.Fusion of orientation and pressure data is used to calculate haptic feedback force,fusion of visual and inertial data is used to achieve high-frequency precise positioning,so as to fully and comprehensively capture the position,orientation and pressure information of the stick during the process of remote palpation;2.Dynamic electromagnetic haptic device design.The electromagnetic haptic device uses the array of three iron core coils with adjustable position and orientation to excite an magnetic field in space,and display magnetic force on the magnetic palpation stick in the magnetic field to simulate haptic feedback.The coil current is driven by the H-bridge structure circuit,and four complementary high-frequency square waves are used to control the switching status of bridge arms,thereby adjusting the magnitude and direction of excitation current.And it is demonstrated that the refresh rate of haptic feedback under this current-driving mode can meet the dynamic requirements of human skin's perception;3.Accurate kinesthetic sense display.The generation process of the current and magnetic field of the iron core coil in the electromagnetic tactile device and the magnetic field superposition mode of the coil array are deduced.A time-varying state space model of the magnetic field generated by the coil array is established.The structure parameters and material parameters of the model are obtained through measurement and simulation,and the experiments of driving voltage,current and magnetic field proved the correctness of this model.Use the positioning result of palpation stick to update the magnetic field generation model in real time,and combine with predictive control to achieve accurate magnetic field generation;4.Vibration tactile feedback to guide operation.Superimpose the ultra-high frequency vibration modulation signal on the square wave used for the coil current drive,and transfer different operation guidance information by designing the time characteristics of the vibration signal such as frequency,amplitude,and duration,thus assisting the user to easily determine the exact position where the kinesthetic sense is reproduced.