| Manipulation technology has always played an important role in various disciplines.In the fields of biological cells,chemical pharmaceuticals,electronic assembly and human health care,the demand for contactless control gradually emerges.As a cheap and nondestructive energy carrier,ultrasound has been widely used in the field of non-contact control.Compared with other non-contact manipulation methods,acoustic manipulation has the advantages of flexible,ability to penetrate the human body and no requirements for the controlled object.Traditional acoustic manipulation uses standing wave.The standing wave has the disadvantages of single direction of control force and the need of acoustic elements to surround the controlled target.The single plane ultrasonic array is studied,and the computational model of holographic acoustic trap generated by planar ultrasonic array is established.The mechanical and morphological characteristics of the acoustic trap are analyzed by simulation.According to the force of particles in the acoustic trap,a suitable control model is established to realize the trajectory control of particles in the plane.In order to analyze the sound field formed by the ultrasonic transducer array,deducing the calculation model of the sound pressure generated by the target point of the ultrasonic array.From the perspective of acoustic energy focusing,the influence of the probe phase in the ultrasonic array on the sound field above the array is simulated and analyzed.The mechanical and morphological analysis of two typical holographic acoustic trap is carried out by simulation.The twin trap is used as the manipulation model of particle trajectory control.The influence of the control phase on the position and angle of the twin trap is analyzed,and the phase calculation method for the particle manipulation by using the twin trap is established.The particle acoustic manipulation model of twin trap is analyzed and researched,and it is abstracted as the control model of spring oscillator,and the control performance of twin trap is analyzed.In order to reduce overshoot in control,a sliding mode controller is proposed to improve the control performance of acoustic control.The feedback of the controller is provided by the computer vision sub module.The camera parameters were calibrated and orthodontic,and the transformation relationship between pixel coordinates and control plane coordinates was established by hand eye calibration method.The target detection method based on threshold segmentation is used as the detection algorithm.In the experimental part,the hardware experimental circuit with FPGA as the core is built,which mainly includes FPGA core board,driving circuit and ultrasonic array.The phase receiving module and square wave output module of FPGA,the phase calculation module and phase transmitting module of PC are programmed.The shape measurement,trajectory movement and rotation experiments of sound trap,as well as the stable suspension and trajectory movement experiments of micro particles are carried out.The experimental results verify the correctness of the phase calculation method and the feasibility of trapping microparticles by acoustic trap. |
