Qiquan Quan

Drilling power consumption and soil conveying volume performances of lunar sampling auger

The sampling auger used in lunar sampling and return mission is to transmit power and convey soil, and its performance is the key factor of the whole mission. However, there is currently a lack of the optimization research on soil conveying volume and power consumption models in auger structure design. To provide the drilled object, the simulation lunar soil, whose physical and mechanical property is the same as the real soil, is made by reducing soil void ratio. The models are formulated to analyze the influence of auger structure parameters on power consumption and soil conveying volume. To obtain the optimized structure parameters of auger, the multi-objective optimization functions of the maximum soil conveying volume and minimum power consumption are developed. To verify the correctness of the models, the performances of different augers drilling simulation soil are tested. The test results demonstrate that the power consumption of optimized auger is the lowest both in theory and test, and the experimental results of soil conveying volume are in agreement with theoretical analysis. Consequently, a new method for designing a lunar sampling auger is proposed which includes the models of soil conveying volume and transportation power consumption, the optimization of structure parameters and the comparison tests. This method provides a reference for sampling auger designing of the Chinese Lunar Sample Mission.

Development of a drilling and coring test-bed for lunar subsurface exploration and preliminary experiments

Drill sampling has been widely employed as an effective way to acquire deep samples in extraterrestrial exploration. A novel sampling method, namely, flexible-tube coring, was adopted for the Chang’e mission to acquire drilling cores without damaging stratification information. Since the extraterrestrial environment is uncertain and different from the terrestrial environment, automated drill sampling missions are at risk of failure. The principles of drilling and coring for the lunar subsurface should be fully tested and verified on earth before launch. This paper proposes a test-bed for conducting the aforementioned experiments on earth. The test-bed comprises a rotary-percussive drilling mechanism, penetrating mechanism, drilling medium container, and signal acquisition and control system. For granular soil, coring experiments indicate that the sampling method has a high coring rate greater than 80%. For hard rock, drilling experiments indicate that the percussive frequency greatly affects the drilling efficiency. A multi-layered simulant composed of granular soil and hard rock is built to test the adaptability of drilling and coring. To tackle complex drilling media, an intelligent drilling strategy based on online recognition is proposed to improve the adaptability of the sampling drill. The primary features of this research are the proposal of a scheme for drilling and coring a test-bed for validation on earth and the execution of drilling experiments in complex media.

A real-time recognition based drilling strategy for lunar exploration

Drilling & coring is considered as an effective way to acquire deep sample on the moon. Since the lunar regolith environment in depth is unknown, sampling drill should be developed to adapt to the undetermined drilling medium on the moon. Once mechanical system of sampling robot was finished, control strategy is a key to realize the high-efficiency drilling process. Since composition of lunar regolith is complicated, its not easy to evaluate all the physical parameters to judge the drilling difficulty level. This paper proposes a novel idea of lunar regolith drillability which is established on the rate of penetration under the given standard terms. Drillability is selected to describe the drilling difficulty level which can be identified online by use of pattern recognition method of SVM. Control algorithm tunes the drilling parameters to adapt to the recognized medium. Experiments are conducted to verify the drillability online recognition based intelligent control strategy can make sampling robot adapt to complicated drilling media.

Real-Time Drilling Strategy for Planetary Sampling: Method and Validation

AbstractDrilling and coring, due to their efficient penetrating and cutting removal characteristics, have been widely applied to planetary sampling and returning missions. In most autonomous planetary drilling, there are not enough prior seismic surveys on sampling sites’ geological information. Sampling drills may encounter uncertain formations of significant differences in mechanical properties. Additionally, given limited orbital resources, sampling drills may have a stuck fault under inappropriate drilling parameters. Hence, it is necessary to develop a real-time drilling strategy that can recognize current drilling conditions effectively and switch to appropriate drilling parameters correspondingly. A concept of planetary regolith drillability based on the rate of penetration (RoP) is proposed to evaluate the difficulty of the drilling process. By classifying different drilling media into several drillability levels, the difficulty level of drilling conditions can be easily acquired. A pattern recogn...

Mechanical Analysis and Measurement of Parameters of Wheel -Soil Interaction for a Lunar Rover

Mechanical models of the wheel-soil interaction are constructed for a rigid wheel of lunar rover when rolling and steering, based on the theories of terramechanics and passive earth pressure. The mechanical affect of different parameters of the soil to the rigid wheel is analysed, such as drawbar pull, rolling torque and steering torque. Experimental results of a rigid wheel in a kind of dry soil, whose mechanical parameters are some similar to lunar soil, validate the models correct. A novel test-bed and its data acquisition system are also designed for testing the performance of the wheel-soil interaction of lunar rover, and their key technologies concerned are discussed.

A Quadruped Micro-Robot Based on Piezoelectric Driving

Inspired by a way of rowing, a new piezoelectric driving quadruped micro-robot operating in bending-bending hybrid vibration modes was proposed and tested in this work. The robot consisted of a steel base, four steel connecting pins and four similar driving legs, and all legs were bonded by four piezoelectric ceramic plates. The driving principle is discussed, which is based on the hybrid of first order vertical bending and first order horizontal bending vibrations. The bending-bending hybrid vibration modes motivated the driving foot to form an elliptical trajectory in space. The vibrations of four legs were used to provide the driving forces for robot motion. The proposed robot was fabricated and tested according to driving principle. The vibration characteristics and elliptical movements of the driving feet were simulated by FEM method. Experimental tests of vibration characteristics and mechanical output abilities were carried out. The tested resonance frequencies and vibration amplitudes agreed well with the FEM calculated results. The size of robot is 36 mm × 98 mm × 14 mm, its weight is only 49.8 g, but its maximum load capacity achieves 200 g. Furthermore, the robot can achieve a maximum speed of 33.45 mm/s.

Drilling states monitoring for a planetary drilling & coring testbed (PDCT): Method and design

Drilling & coring has been selected as an effective method of acquiring soil sample in robotic planetary explorations. To avoid serious overload faults, drilling states should be monitored online and be tuned in a reasonable range. Herein, a novel flexible tube coring (FTC) method is adopted in China lunar exploration mission. To verify the proposed FTC method and acquire useful drilling states for online control, a planetary drilling & coring testbed (PDCT) was developed. The flowing states of lunar regolith are accurately acquired by applying a camera to calculate the volume of removed cuttings and by utilizing an ultrasonic sensor into the hollow auger to monitor the state of coring soil. Besides, drilling loads are acquired by a F/T sensor installed at the bottom of soil container. Experiments in one typical lunar regolith simulant show that the designed PDCT can be used to conduct ground tests for optimizing drill tools structure and control strategy.

Development of a drilling and coring test-bed for lunar subsurface exploration

Drill sampling has been widely employed in extraterrestrial exploration. Since the extraterrestrial environment is uncertain and different from that on the earth, the extraterrestrial drill sampling mission is at risk of failure. Therefore, the principle of drilling and coring in extraterrestrial environment and the structural parameters of special drilling tools should be tested and verified. In this paper, a drilling and coring test-bed for lunar subsurface exploration is proposed. Firstly, this paper analyzes the requirements of the drilling and coring test-bed for lunar subsurface exploration. According the requirements, the test-bed consists of rotary-percussive drilling mechanism, penetrating mechanism, drilling medium container and signal acquisition and control system. Finally, this paper gives the experiments implemented on the test-bed. It has been verified that the principle of drilling and coring for lunar exploration, the design of drilling tools, the algorithms of medium recognition and real-time drilling control are effectual.

Optimization and Analysis of a U-Shaped Linear Piezoelectric Ultrasonic Motor Using Longitudinal Transducers

A novel U-shaped piezoelectric ultrasonic motor that mainly focused on miniaturization and high power density was proposed, fabricated, and tested in this work. The longitudinal vibrations of the transducers were excited to form the elliptical movements on the driving feet. Finite element method (FEM) was used for design and analysis. The resonance frequencies of the selected vibration modes were tuned to be very close to each other with modal analysis and the movement trajectories of the driving feet were gained with transient simulation. The vibration modes and the mechanical output abilities were tested to evaluate the proposed motor further by a prototype. The maximum output speed was tested to be 416 mm/s, the maximum thrust force was 21 N, and the maximum output power was 5.453 W under frequency of 29.52 kHz and voltage of 100 Vrms. The maximum output power density of the prototype reached 7.59 W/kg, which was even greater than a previous similar motor under the exciting voltage of 200 Vrms. The proposed motor showed great potential for linear driving of large thrust force and high power density.

Development of a rotary-percussive ultrasonic drill for extraterrestrial rock sampling

Compared with traditional rotary-percussive drills driven by electromagnetic motors, ultrasonic drills show advantages of small size, low power, low weight on bit, and lubrication free, making them available for the extraterrestrial rock sampling, especially for the minor planet with a weak gravitational field. To solve the problem that the conventional percussive ultrasonic drills cannot remove cuttings effectively, we proposed a rotary-percussive ultrasonic drill which realizes both rotary and percussive motions of the drill bit. The conventional percussive ultrasonic drills employ the vibration energy of the front mass of the Langevin transducers to generate mechanical vibration at the bottom surface of the horn, however, the vibration energy of the back mass is not utilized. Thus, we proposed to use the vibration energy of the back mass to generate a rotary motion via a longitudinal-torsional coupler. The rotary shaft drives the drill bit to rotate continuously to deliver the cuttings out so as to increase drilling efficiency. When the diameter of the drill bit is 5 mm and the axial load is 5 N, RPUD can drill the sandstone in rotary-percussive drilling mode with a speed of 12.4 mm/min while RPUD can only drill the sandstone at a speed of 8.7 mm/min in percussive drilling mode. Contrastive experiments show that the rotary-percussive drilling can actually raise the drilling efficiency compared with percussive drilling, which indicates that the RPUD is superior to conventional percussive ultrasonic drills.