| In asteroid exploration,the probe’s attachment and anchor sampling technology is of great significance for in-situ scientific exploration of asteroids and resource development and utilization.This article takes the application of the percussive ultrasonic drill(PUD)in the process of attachment and anchoring of the asteroid probe as the background,combined with the application requirements of the aerospace environment,to adapt to the complexity of the space environment,has the ability to resist space radiation,and can achieve the impact of the PUD.The goal is to develop an impact-type PUD generator based on FPGA(Field Programmable Gate Array)control with the aerospace DC 28 V as the power supply input and output power not higher than 200 W.The prerequisite for designing the driver is to analyze the working principle of the PUD,and analyze the energy conversion process of the PUD to convert the electrical excitation signal into mechanical vibration under the action of the driving signal.Establish the corresponding equivalent circuit model,analyze the impedance characteristics of the PUD from the perspective of equivalent electrical parameters,and study the impedance characteristics of the PUD under different load conditions.Based on the load characteristics of PUD,a characteristic matching network with better adaptability between the generator and the PUD is established.Considering that the PUD needs a variable frequency,high frequency and high voltage sinusoidal drive signal,the overall hardware circuit of the generator is designed,and the generator hardware is modularized according to the division of different functions.In the DC boost module,considering the selection restrictions of aerospace-grade power tubes,under the condition of DC 28 V input,the output design of DC 100 V switching regulator source is carried out.In order to meet the requirements of low power output,the half of the low-voltage drive signal control is designed.The bridge drive module realizes the inverter from DC to AC.Design a signal acquisition module capable of real-time acquisition of the impedance characteristic parameters of the PUD,and send it to the upper and lower computer system for monitoring and display.Construct a characteristic matching module with impedance matching and tuning matching functions to ensure effective energy transmission.In order to adapt to the drift of the resonance state of the PUD during drilling,and maintain the dynamic stability of the resonant working state,the resonance control method of PUD by the driver is designed based on FPGA.Design automatic scanning resonant frequency control method and frequency tracking control method with digital phase lock function,realize the function of automatic scanning PUD resonant frequency and real-time tracking adjustment of drift resonant frequency when the generator is turned on,using FPGA as the carrier,design the logic unit of each control stage,perform functional simulation,verify the control program’s effectiveness.On the basis of the design and completion of the generator’s hardware structure and control program,the driver characteristic test is carried out.With the transducer as the driving object,the end face amplitude characteristic test experiment was carried out when the transducer was driven.The test showed that the end face of the transducer can reach a mechanical amplitude of ±30 μm or more under drive control and maintain stable vibration.With the PUD drill as the driving object,the drilling test for different simulated star rock samples under normal temperature and pressure environment and the drilling test under high and low temperature environments are carried out,and the driving effect of the PUD is obtained from the drilling test results.With a power consumption of about70 W,a stable drilling effect of more than 20 mm/min can be achieved. |
