超声波钻谐振控制算法设计及试验验证

为解决小天体表面引力小及温差变化大难以实现锚固的问题,提出以超声波钻作为锚固工具并采用模糊控制和恒流控制相结合的策略,实现了低钻压力和高低温环境条件下的超声波钻钻进锚固。压电驱动的超声波钻将高频电能转化为高频机械振动,驱动钻具高频破碎岩石,具有极低钻压力的显著优势,尤其适用于弱引力小天体的钻进锚固作业。针对超声波钻的驱动,对超声波钻的谐振控制算法进行研究。首先,建立超声波钻换能器的等效电路模型,在等效模型基础上研究换能器的阻抗特性、负载特性、温度特性和滞后特性。其次,根据超声波钻的工作特性研究谐振频率识别算法、谐振频率跟踪算法和恒电流控制算法,针对谐振频率跟踪算法研究了基于递归最小二乘估计的频率跟踪算法和基于模糊控制的频率跟踪算法,并对实际控制效果进行对比分析。最后,进行常温常压和高低温环境下钻进试验,试验结果表明,在不同温度环境和不同的钻进对象条件下,所设计的谐振控制算法能够实现对超声波钻的稳定驱动。研究结果表明,所提出的模糊控制和恒流控制能够有效的在低钻压力以及不同温度下实现有效钻进。

一种压电换能器的结构设计与拉伸式装配方法

压电换能器装配预应力直接影响产品性能。大直径压电换能器对装配预应力控制和压电陶瓷应力分布均匀性提出了更高的要求。为实现大直径压电换能器的高预紧力装配,开展了大直径压电换能器结构设计、装配方法设计和径向应力均匀化研究。首先,基于传输线方法和模态分析开展压电换能器设计,采用Morris方法进行了尺寸参数对压电换能器纵振频率、振幅比和节面位置偏差的灵敏度分析,并设计了预期性能的压电换能器;然后,根据压电换能器对预应力控制的需求,提出了一种液压拉伸式装配方法;针对拉伸装配过程中压电陶瓷组的径向应力分布不均匀问题,对拉伸装配过程中的2个关键状态进行了静应力分析,以指导压电换能器的结构改进设计;最后,设计了拉伸装配装置,并基于该装置完成了压电换能器装配试验。试验结果验证了所提拉伸式装配方法可实现预期性能的压电换能器装配。压电换能器装配后的串联谐振频率和并联谐振频率分别稳定在18.05 kHz和19.57 kHz附近,串联谐振阻抗在10Ω以内,机电耦合系数在0.34~0.36之间。研究结果为控制压电换能器装配预应力提出了新的解决思路,并为大直径压电换能器设计时如何均化陶瓷应力状况提供了解决方法。

一种单压电叠堆驱动的回转冲击超声波钻

为提高冲击式超声波钻的排屑效率,基于压电驱动原理提出了一种单压电叠堆驱动的回转冲击超声波钻(RPUD)。RPUD仅利用单一压电叠堆两侧的振动实现了钻具的回转冲击运动,将一侧振动转变为回转运动,另一侧振动转变为冲击运动,且回转运动和冲击运动可单独调节。为实现超声波钻回转运动和冲击运动的同步谐振,借助有限元方法,对超声波钻换能器进行模态分析和瞬态分析。基于优选的结构设计参数,研制了RPUD样机并开展了钻进实验研究。实验结果验证了RPUD的钻进功能,并利用响应面方法分析了钻压力等各钻进参数对钻进效率的影响。

多臂协作式小天体附着取样机器人机械系统

为解决探测器在弱引力、特性未知小天体表面的附着取样难题,提出一种融合着陆缓冲、附着固定、取样、放样等核心功能为一体的附着取样一体化机器人设计方案。基于腿臂复用,提出多臂协作主动自适应式着陆缓冲方案;利用超声波钻钻压力小、硬质岩石表面钻进效率高的特点,提出针对岩石类小天体的超声波钻式附着固定方案;针对星表特性不确定,取样适应性要求高的需求,提出砂轮磨削、毛刷清扫的双模式取样方案。采用仿真方法对着陆缓冲性能、取样性能等进行分析;在原理样机研制基础上,开展附着取样全流程实验。结果表明,附着取样机器人可实现着陆缓冲、附着固定、取样、放样等功能,验证了该系统的核心功能。本研究旨在探索小天体附着取样方法,为小天体取样返回任务提供技术支持。

一种压电换能器直接驱动钻具的超声波钻探器

为满足深空探测任务中,空间环境苛刻的外星体表面岩石钻取采样任务的使用需求,本文设计了一种基于压电驱动原理,可搭载在漫游车机械臂末端的超声波钻探器。超声波钻探器的压电换能器直接与钻具发生冲击碰撞,以驱动钻具作高频冲击运动,达到冲击破碎岩石的目的。设计了钻探器的压电驱动单元,并理论分析了压电换能器变幅杆与钻具的冲击碰撞过程。通过实验研究了超声波钻探器对砂岩的钻进性能及钻压力与钻具长度对钻探器钻进性能的影响。实验结果表明:所研制的超声波钻探器可对砂岩进行有效钻进,而且所需的钻压力较小,可用于彗星、小行星等弱引力场的地外天体表面岩石的钻取采样。

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.

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.

小行星探测器电磁阻尼着陆缓冲遇阻特性

着陆缓冲是小行星原位探测的基础。探测前小行星表面形貌未知,着陆缓冲时容易遇到阻碍并产生倾覆,因此需要研究小行星探测器着陆缓冲遇阻特性。建立机械与控制耦合的着陆缓冲动力学联合仿真模型,并采用神经网络对其碰撞接触参数进行标定。基于建立的仿真模型,理论研究了切向着陆速度、法向着陆速度、探测器偏航角、着陆倾角对着陆缓冲遇阻过程的影响规律,探究了不同偏航角对着陆过程各着陆缓冲阶段的影响,分析了着陆遇阻倾覆的主要影响因素及其影响规律。在微重力环境模拟小行星着陆缓冲实验平台上开展了着陆缓冲遇阻实验,研究了初始着陆参数及着陆介质对着陆缓冲过程的影响规律并验证了仿真模型。仿真获得的着陆缓冲时间与实验结果的误差小于15%,表明建立的仿真模型是准确的。

嫦娥五号月壤剖面钻进取芯状态分析与解译

嫦娥五号探测器通过表取和钻取的方式分别采集了表层和剖面月壤,并将月壤样品返回地球。月面钻进取芯过程的遥测数据直接反映了采样钻具与剖面月壤之间的相互作用状态,对其进行分析与解译能提高月面钻取采样任务的科学价值。基于嫦娥五号钻取采样装置的系统构成、工作原理和性能指标,从遥测数据中辨识出代表性钻进取芯工况。结合机-壤相互作用机理以及地面钻取采样试验数据,分析钻进取芯过程及其负载波动状态的月壤组构致因,并对全钻进剖面的月壤层序状态进行机理性解译。研究表明,嫦娥五号钻进点月壤剖面至少具有三个明显的层序结构,钻进剖面内存在着毫米级尺度月壤颗粒;钻取采样装置面对非确知月壤剖面已充分发挥其预定效能,并针对我国后续拟实施的星壤剖面采样探测技术做出了展望。

Drilling load modeling and validation based on the filling rate of auger flute in planetary sampling

Some type of penetration into a subsurface is required in planetary sampling. Drilling and coring, due to its efficient penetrating and cuttings removal characteristics, has been widely applied in previous sampling missions. Given the complicated mechanical properties of a planetary regolith, suitable drilling parameters should be matched with different drilling formations properly.Otherwise, drilling faults caused by overloads could easily happen. Hence, it is necessary to establish a drilling load model, which is able to reveal the relationships among drilling loads, an auger＇s structural parameters, soil＇s mechanical properties, and relevant drilling parameters. A concept for the filling rate of auger flute（FRAF） is proposed to describe drilling conditions. If the FRAF index under one group of drilling parameters is less than 1, this means that the auger flute currently removes cuttings smoothly. Otherwise, the auger will be choked with compressed cuttings. In drilling operations, the drilling loads on the auger mainly come from the conveyance action, while the drilling loads on the drill bit primarily come from the cutting action. Experiments in one typical lunar regolith simulant indicate that the estimated drilling loads based on the FRAF coincide with the test results quite well. Based on this drilling load model, drilling parameters have been optimized.

Multi-state autonomous drilling for lunar exploration

Due to the lack of information of subsurface lunar regolith stratification which varies along depth, the drilling device may encounter lunar soil and lunar rock randomly in the drilling process. To meet the load safety requirements of unmanned sampling mission under limited orbital resources, the control strategy of autonomous drilling should adapt to the indeterminable lunar environments. Based on the analysis of two types of typical drilling media （i.e., lunar soil and lunar rock）, this paper proposes a multi-state control strategy for autonomous lunar drilling. To represent the working circumstances in the lunar subsurface and reduce the complexity of the control algo- rithm, lunar drilling process was categorized into three drilling states： the interface detection, initi- ation of drilling parameters for recognition and drilling medium recognition. Support vector machine （SVM） and continuous wavelet transform were employed for the online recognition of drilling media and interface, respectively. Finite state machine was utilized to control the transition among different drilling states. To verify the effectiveness of the multi-state control strategy, drilling experiments were implemented with multi-layered drilling media constructed by lunar soil simulant and lunar rock simulant. The results reveal that the multi-state control method is capable of detecting drilling state variation and adjusting drilling parameters timely under vibration interferences. The multi-state control method provides a feasible reference for the control of extraterrestrial autonomous drilling.