Ultrasonic Radiation Force Focusing On Palm Based On Visual Feedback

For many years,human-computer interaction technology has always been a hotspot of research and exploration.At present,mature interaction technology usually uses the human visual system,and usually ignores the important sense of touch.Palm detection and location is one of the most popular human-computer interaction technologies.However,human-computer interaction only through visual method often leads the human body unable to accept the most direct feedback,which brings bad interaction experience.Therefore,this paper proposes a tactile feedback method based on ultrasonic array,which can give a tactile feedback to the points on the trajectory according to the palm motion trajectory obtained by visual positioning.In order to achieve the sound field focusing of the ultrasonic array,the sound pressure equation of a single transducer in different positions in space according to the most basic acoustic principle,and then simulates the sound pressure model formed by the transducer array in space.The sound pressure of three-dimensional coordinate points in space is controlled by controlling the phase distribution of the transducer array.The single point focusing uses the distance between the transducer and the focal point to solve the phase distribution of the ultrasonic emitted by the transducer.In addition,using the deduced sound pressure model between the array and the focus point,the sound pressure relationship between multiple probes and multiple focus points is established,and the pseudo-inverse algorithm,random superposition algorithm and Gerchberg-Saxton algorithm are used to realize the space Multi-point focus.In order to locate the 3D coordinates of the points on the palm movement track by binocular vision,the binocular camera is calibrated and corrected firstly,and the distortion caused by the non-parallel camera plane is eliminated.Then,the corrected image is preprocessed by the target detection algorithm SSD and YOLOv4 to obtain the target candidate box containing the palm.Finally,according to the triangle similarity principle,the center point of the target candidate box is located,and the coordinate transformation process of the palm center point on the palm trajectory is obtained.In order to verify the function of the simulation,this paper built a complete ultrasonic tactile feedback platform composed of FPGA controller,driving circuit,ultrasonic transducer array circuit and binocular camera.The basic experiments of single-point,multi-point and trajectory movement are effectively implemented.According to the movement track of the palm located by the binocular camera,the phase distribution of the focusing sound field is calculated by the ultrasonic phased array,and the focused sound field is feedback to the moving palm in real time.Experiments show that the ultrasonic array phase calculation method used in this paper is true and effective,and the tactile feedback is given to the moving palm in real time.