Xuyan Hou

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.

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.

Research on the adhesion characteristic of climbing robot feet with bionic gecko microarray for spacecraft based on DEM

At present, the robot arm technology occupies the dominant position in the space payload control field. However, with the limitations of robot arm technology, the load control technology with higher flexibility and mobility came into being. The space miniature climbing robot performs on-orbit control tasks such as fault repair and waste removal by crawling through the robotic arm and adhering to the target spacecraft. In this paper, the adhesion characteristic of space climbing robot is studied, an adhesion microarray structure is proposed, and the influence of the contact area, slenderness ratio, length, diameter and density of the microarray on the adhesion characteristics in the zero - gravity environment is analyzed respectively by using the discrete element software EDEM. Results show that: 1) Increasing the density of array with no fibers tangling each other, can obtain the larger adhesion. 2) In order to obtain a larger tangential adhesion, the fiber diameter should be increased and the length be reduced, while in the actual environment, the length/diameter ratio should be appropriately increased because limitation of adaptability to the surface.

Study on the dynamic characteristics of a hammer-driven-type penetrators in the penetration process

Dynamic penetration test by a penetrator is an important detection method for lunar exploration. The analysis of the dynamic penetration properties of the penetrator significantly helps to design the penetrator structure. In this article, the dynamic penetration mechanical model was established according to soil mechanics. Then, the discrete-element simulation model, which was established using the application program interfaces of the EDEM software, was used to simulate the penetration process. The penetration experiment demonstrated the accuracy of the dynamic penetration model and the discrete-element simulation model. This study of dynamic penetration model of a penetrator may provide technical support to the deep space exploration.

Coordinated motion control model of a six-wheeled rocker lunar rover

At present, control methods of the six-wheeled rocker lunar rover primarily consist of setting the same driving parameters for each wheel. This type of control method ignores the multiple active driving characteristics of the lunar rover and causes parasitic power loss. The main cause of the parasitic power loss is the uncoordinated motion of the driving elements. Therefore, in this article, a coordinated motion programming model of the six-wheeled rocker lunar rover based on the velocity projection theorem, the quasi-static mechanical model, and the rated power of the motor is established to eliminate parasitic loss, reduce driving energy, and improve energy efficiency. The analytical solution of the programming model based on the Kuhn–Tucker condition is also calculated. The coordinated motion control model saves energy, and it is suitable for other wheeled-type planet rovers. This model provides technical support for reducing the energy consumption of planet rovers.

The study of the drilling core features of a multi-pipe deep lunar soil sampling driller for manned lunar exploration based on the discrete element technology

Lunar soil sampling is important for human beings to know about the components of lunar soil and the lunar geological structure. By now, lunar soil between the depths 0 and 3 meters is researched, but there are not any drillers which can collect the much deeper lunar soil. In this paper, a multi-pipe driller that can drill 5 meters deep for manned lunar exploration was proposed. In order to verify the reliability of drilling core, the drilling core features of the driller were studied by using the EDEM software. The influences of drill pipes rotation speed and feed rate to the drilling core were studied. The results turned out that the feed rate had a significant influence on the drilling core features and the rotation speed had an important influence on the power and the torque. The simulation results can provide guidance for the optimization of the system structure and the technical supports to Chinas deep lunar soil sampling project.

A simulation study on a digging-typed lunar soil sampling device and its sampling characteristics based on discrete element method

Lunar soil sampling is an important task for lunar probe. It is the premise of the analysis of lunar soil and the study of lunar environment and evolutional history. Lunar soil sampling techniques have different classifications according to different standards. In view of goals of Chinas lunar exploration sampling project, a design of digging-typed lunar soil sampling device based on the mechanical arm is proposed in this paper. Mechanical characteristics of digging sampling process are analyzed in EDEM as well. Analysis results based on discrete element method show the compressive stress distribution of lunar soil particles during the digging process, vertical force and horizontal force of the sampling device during the digging process and the weight of samples in one sampling action. These simulation results prove the feasibility of the sampling device and lay the foundation for Chinas manned lunar exploration in the future.

A drilling tactic to tackle indeterminable environment in lunar regolith sampling

Drilling and coring, as a main sampling method to acquire subsurface media, has been generally utilized in the extraterrestrial explorations. Due to the indeterminacy of the media beneath the planetary surface which is mainly caused by the various formation processes of planet, there will be great discrepancies of the drilling load between the different locations on the planet. Thus, how to identify the medium at the present drilling position and then regulate drilling strategy to guarantee the load in an acceptable region are critical to ensure the drilling reliability. In order to handle the indeterminable environment in planetary sampling, this paper presents a drilling tactic by way of recognizing the media drillability and controlling the penetrations per revolution (PPR) during drilling process. Theoretical and experimental research on interaction between drill and media during PPR controlled drilling is utilized to solve the relation between the PPR and drilling load. Finally, a drilling test of stratified media based on on-line recognition is carried out to verify the feasibility of the drilling tactic.

Optimization of percussive mechanism in rotary-percussion drill for lunar exploration

Rotary-percussive Drill (RPD) has been widely employed in extraterrestrial exploration as a main drilling and sampling device. Percussive mechanism, as an inevitable part of RPD, is commonly utilized to exert percussion onto drill stem to improve drilling performance once hard rock is encountered. However, since driving resource provided by the probe is limited in lunar exploration, outputs of percussive mechanism-impact energy and percussive frequency-which are restricted by system power affect the drilling efficiency greatly. In order to maximize the percussive performance under a limited power resource, this paper presents a kind of feasible optimization approach aiming at optimizing the design parameter matches of percussive mechanism. The optimized result is compared with a group of randomly-selected parameters match to emphasize the advantage of optimization. Experiments are conducted on a Drilling and Coring Test-bed (DCTB) to verify the optimized result.

A piezoelectric-driven ultrasonic/sonic driller for planetary exploration

Drilling is an essential task in unmanned lunar exploration and future explorations of other planets like mars. The traditional way is to adopt a rotary-percussive drill usually mounted on the side of probe or at the end of a robotic arm on planetary rover. Large penetrating force is needed to cooperate with rotary and percussive motion to overcome hard rock. Under the low-gravity environment, it is not easy to provide large penetrating force. As a kind of percussive drill, piezoelectric-driven ultrasonic/sonic driller (USD) employs piezoelectric component to transfer electric energy to mechanical energy of drill bit. Since piezoelectric component has wide temperature tolerance ability, USD can work well in harsh planetary environment. A USD is developed in this paper which has only one degree of freedom of percussive movement and the physical process of percussive drilling is modeled. Experiments indicate that the USD is a high-efficiency drilling device which is lightweight and requires low penetrating force.