Design And Research Of Sampling Device For Rock Ultrasonic Grinding On Asteroid Surface

Small celestial bodies are one of the most important windows for humans to understand the solar system.At the same time,small celestial bodies are rich in precious metals and rare elements and have great exploration value.Therefore,the detection of small celestial bodies has long-term significance.The ultrasonic drilling device based on the inverse piezoelectric effect has the advantages of simple structure,small size,light weight and small axial force.It successfully solves the problems of tight carrying capacity,strict size restrictions,and limited anchoring force of the detector,shows significant advantages in deep space exploration.Aiming at the first asteroid landing sampling task in China,this paper combines a theory and simulation analysis method to design an asteroid surface rock ultrasonic sample grinding device.The dynamic model of piezoelectric transducer is established based on the elastomer assumption,and the dimensions of each part are preliminarily determined according to the frequency equation of the piezoelectric transducer.With the help of Mason's equivalent network principle,an equivalent network model of a longitudinaltorsion composite piezoelectric transducer was established,and the working rules of the piezoelectric transducer were described.Using the finite element method,the main parameters of the piezoelectric transducer were analyzed and optimized according to the output characteristics including output capability,longitudinaltorsional conversion capability,energy utilization rate and output mode stability.According to the modal analysis and harmonic response analysis of the optimized piezoelectric transducer,parameters such as maximum longitudinal-torsional ratio and output amplitude are obtained to characterize the output characteristics of the piezoelectric transducer.According to the motion output mode of the longitudinal-torsion composite piezoelectric transducer,the design and research of the energy transfer unit are completed.In order to understand the role of the free mass in the energy transfer process better,a collision vibration system including a piezoelectric transducer impact head,free mass and grinding rod was established.By modeling and analyzing the no-load collision vibration system,the collision frequency and motion curve of the free mass and the grinding rod are obtained under the determined initial state.Realize the nonlinear description of the complex motion of the collision vibration system.Based on the theory of rock fragmentation,the interaction process of rock grinding was studied.The rock stress distribution and rock penetration depth curves of different grinding heads are obtained,and the rock penetration depth and grinding speed of different free mass are obtained.The quantitative description of grinding effect is realized,and the selection of grinding head and free mass are also guided.Finally,based on the simulation analysis results,the design of the ultrasonic sample grinding device is completed.