Research

Research Directions

The Aerospace Mechanism Testing laboratory focuses on three core research areas: planetary anchoring and sampling, ultrasonic drive and control, and load simulation and testing. The laboratory committed to promote innovation and application in aerospace structure and mechanism technology. The laboratory upholds the philosophy of “engineering nurtures academia, and academia promotes engineering,” integrates closely scientific research with engineering practice, drives technological breakthroughs according to the practical needs and enhances the engineering capabilities through academic achievements. In the research system, graduate students focus primarily on scientific research, conducting in-depth analysis of key technological issues within engineering practice, striving to distill innovative academic results, and laying a theoretical foundation for the development of the field. Meanwhile, engineers focus on the design, integration, and engineering implementation of electromechanical systems, ensuring that the project progresses steadily and maintaining the quality of the work. The two teams, as the core forces of the laboratory, support each other, engage in collaborative innovation, and grow together. The academic exploration of graduate students provides theoretical support for engineering practice, while the technical implementation by engineers drives the practical transformation from research outcomes. The closely integrated model that enables the laboratory to continuously achieve breakthroughs in the field of aerospace mechanism testing, contributing solid support to the development of aerospace engineering.

• Planetary Anchoring and Sampling

Deep space exploration refers to aerospace exploration activities conducted on celestial bodies beyond Earth, outside the influence of Earth’s gravity field. China’s deep space exploration missions primarily include the Chang’e program and the Tianwen series. Among them, the Chang’e program focuses on lunar exploration, while the Tianwen series is aimed at a broader range of planetary exploration tasks. The AMT laboratory develops foundational theoretical research and engineering application exploration focused on planetary anchoring and sampling mechanisms within the significant mission backgrounds of the Chang’e program and the Tianwen series. The laboratory is committed to break through the bottlenecks of the key technological in the exploration of the Moon, Mars, asteroids, and the Jupiter system for deep space missions, providing solid technical support for the successful implementation of deep space exploration tasks.

Planetary anchoring can be divided into mobile anchoring and fixed anchoring. The choice and design of the method of anchoring determined by the different environmental conditions of celestial bodies. Mobile anchoring: In lunar exploration missions, rovers must operate in an environment with 1/6g gravity and in the soft, rugged terrain of the lunar soil. Therefore, it is necessary to design a reasonable wheel configuration and optimize the wheel slip ratio to ensure that the rover has reliable propulsion performance, avoiding getting stuck or slipping. In the exploration mission of Callisto, the robot needs to operate in a 1/8g gravity environment. Considering the possibility of existing complex terrain covered by an icy crust on Callisto, the robot needs to employ an efficient mobility system to ensure stable movement without jumping or rolling, in order to complete the exploration mission. Fixed anchoring: In asteroid exploration missions, traditional modes of movement are difficult to apply due to the extremely low surface gravity of asteroids (<0.028 g). If the robot is not secured, it is easily rebound off from the asteroid’s surface by even minor external forces. Therefore, the spacecraft needs to utilize fixed anchoring technology to establish a reliable mechanical connection between the robot and the surface of the asteroid, providing a stable operating platform for subsequent sampling operations. Planetary sampling is a crucial component of deep space exploration, referring to the utilization of sampling mechanisms such as drilling, shoveling, excavating, and collecting to obtain surface or near-surface samples from the Moon, Mars, and asteroids. Then the samples are packaged and processed to support scientific research and resource analysis.

China’s lunar exploration program is divided into four stages: orbiting, landing, returning, and surveying, gradually developing in-depth exploration and scientific research of the Moon. The Chang’e 1 and Chang’e 2 spacecraft conducted Moon orbit missions, performing global surveys of the Moon and obtaining comprehensive maps of the lunar, thereby laying the foundation for subsequent exploration missions. Chang’e 3 achieved China’s first soft landing on the Moon, with the lander successfully delivering the Yutu lunar rover, which subsequently conducted surface exploration and surveying. The Chang’e 5 spacecraft successfully achieved a soft landing on the Moon surface, performing drilling and sampling tasks with its mechanical arm, and successfully returned lunar soil samples to Earth, providing valuable lunar material samples to humanity. The Chang’e 4 mission, as the first human endeavor to explore the far side of the Moon, successfully delivered the Yutu-2 lunar rover to far side of the Moon and conducted exploration and surveying, filling a gap in global deep aerospace exploration. The Chang’e 6 mission further enhanced the capabilities of sampling by achieving the first-ever sample return from the far side of the Moon, exploring the material composition of the Moon far side and providing new evidence for lunar evolution. The Chang’e 7 mission conducts comprehensive exploration focused on the scientifically significant hotspot region of the south pole on the Moon, with particular emphasis on investigating the potential presence of water ice resources in that area. The Chang’e 8 mission not only conducts scientific and technical experimental verifications on the lunar surface but also aims to establish a lunar research base, paving the way for future manned lunar landings and long-term lunar exploration.

China’s planetary exploration missions are named the “Tianwen Series,” aimed at exploring deep space targets such as Mars, asteroids, and Jupiter. Tianwen-1 (First Phase of Mars Exploration): This is the China’s first independent Mars exploration mission, achieving both the orbiting and landing of the spacecraft on Mars. The Zhurong Mars rover successfully soft-landed on the Martian surface and conducted survey explorations, obtaining data on Mars’ geology, climate, and environment. Tianwen-2 (Exploration of Small Celestial Body): The mission aims to explore near-Earth asteroids. The spacecraft anchors the surface of the asteroid for sampling and returns the samples to Earth. After completing the sampling mission, the spacecraft continues its flight to explore a main-belt comet, carrying out multi-target exploration tasks in deep space. Tianwen-3 (Second Phase of Mars Exploration): The mission plans to achieve a soft landing on the Martian surface and conduct a soil sampling task to bring Martian surface materials back to Earth, further analyzing Mars’s evolutionary history and potential signs of life. Tianwen-4 (Exploration of Jupiter System): The spacecraft performs orbital exploration of Jupiter and its satellites, obtaining key data on Jupiter’s magnetic field, atmosphere, and gravity. The mission also includes a soft landing on one of Jupiter’s satellites to conduct scientific investigations in situ, exploring the potential presence of oceans and signs of life on it.

1）Lunar Mobility and Exploration (2005~2007) : In the lunar rover exploration missions of Chang’e 3 and Chang’e 4, the research team conducted in-depth studies on wheel configuration design and testing to enhance the traction capability of the Yutu rover on the soft and rugged lunar surface. In the analysis of the motion characteristics of lunar rover wheels, based on Vehicle Ground Mechanics, dynamic models for wheel rolling and steering on soft lunar regolith are established. The research team study the drawbar pull and driving torque in relation to variations in vertical load, sinkage, and slip ratio of the wheels [1]. To meet the testing needs of lunar rover wheels, the first domestic test bench for the motion characteristics of lunar rover wheels is successfully developed [2]. The test bench is equipped with multiple functions, including vertical load simulation, slip ratio simulation, forward speed simulation, and steering speed simulation, allowing for the precise quantification of the wheels’ rolling and steering characteristics. During the testing process, the research team conducted systematic experiments on wheels of various sizes, configurations, and materials. Ultimately, it was determined to adopt a mesh wheel configuration, which consists of a mesh material paired with an appropriate amount of claws. The wheel has a diameter of 300 mm, a width of 150 mm, and a weight of 735 g per wheel. The Shanghai Academy of Spaceflight Technology utilized the test bench to conduct rigorous experimental validation of the wheels employed in the Yutu lunar rover. The following is quoted from a report by People’s Daily: The mesh wheel has not been applied to ground vehicles, which led to skepticism from domestic experts in wheel loads [3]. Designer Jie Xiao from the No. 805 institute of the Shanghai Academy of Spaceflight Technology said that “We decided to let the experimental data speak for itself, and contacted domestic experts specialized in wheel engineering to test the drawbar pull, adaptability, load-bearing capacity, and other factors of the mesh wheel, thoroughly dispelling the experts’ doubts.” This innovative wheel design scheme provides strong support for the smooth operation of the Yutu lunar rover and offers valuable technical experience for the wheeled design of future lunar rovers.

2）Lunar Drilling and Sampling (2010~2024) : In the Chang’e 5 mission, the spacecraft employed a drilling and sampling method to obtain subsurface samples of the Moon, while ensuring the preservation of the original. A “dual-tube single-bag” drilling with non-sliding differential coring which has the capability of maintaining the lunar soil profile sequence was designed, ensuring that samples are not disturbed during the drilling process, thereby preserving complete geological stratigraphic information [4]. A test bench for the comprehensive performance of the drilling was developed [5], which verified the effectiveness of the coring scheme with flexible bag and thoroughly evaluated the sampling performance of the drilling. Under the strict constraints of quality and energy, a parallel axis rotary impact drilling mechanism was proposed after comparing multiple schemes. Additionally, the envelope range of the drilling drive parameters was determined to ensure the stability and efficiency of the drilling operations. The research developed a multi-segment elastic sealing device and tested equipment for the high and low-temperature stiffness of the seal, which ensures that the drilling mechanism can achieve reliable sealing under the extreme environmental conditions of the lunar surface. In response to the complex drilling target of uncertain lunar regolith, a drilling control method was proposed that integrates state monitoring variables for online identification of drillability. This approach enables intelligent adaptive drilling, thereby improving drilling efficiency and success rates. In 2020, the Chang’e 5 mission successfully completed China’s first unmanned lunar sampling exploration, obtaining 260 g of drilling samples, which provided precious physical samples for lunar scientific research. In 2024, the Chang’e 6 mission accomplished a groundbreaking task on the far side of the Moon, successfully collecting 320 g of drill samples, further expanding human understanding of the composition and evolutionary processes of the lunar far side.

3）Martian Flight-Based Sampling (2016~2028) : The lunar surface exists in a high vacuum environment with no atmosphere, resulting it impossible for traditional rotorcraft to operate on the Moon. However, different from the Moon, the Martian surface has a thin atmosphere (composed of 95% carbon dioxide), which provides the necessary aerodynamic conditions for rotorcraft flight. On April 19, 2021, NASA’s Ingenuity Mars Helicopter successfully achieved the first controlled flight by humans on an extraterrestrial body in history, marking a significant breakthrough in deep aerospace flight exploration technology. This achievement not only holds profound historical significance but also provides new technological pathways for future Mars exploration missions. For the Tianwen-3 Mars sampling return mission, the research team conducted flight sampling exploration studies employing Mars rotorcraft. Compared with the traditional Mars rovers, Mars rotorcraft offer significant advantages in exploration: It has a fast flight speed and high scientific detection efficiency, enabling them to quickly cover larger areas of the Martian surface; It can flight over complex terrains (such as steep cliffs and impact craters), performing stationary hover surveys to overcome the mobility limitations of rovers in rugged landscapes; It can autonomously generate high-resolution local maps of Mars, with a resolution far superior to satellite images captured by orbiters; It also can provide precise path planning for rovers, enhancing the execution efficiency of surface exploration missions. Despite Mars rotorcraft has the enormous potential, the development of it faces a series of significant challenges: The atmospheric density on Mars is only 1% of Earth’s average atmospheric density, resulting it difficult for the rotors to generate sufficient thrust, which limits the rotorcraft’s hovering and maneuvering performance. The extreme temperature range on the Martian surface, approximately −130°C to 30°C, poses severe challenges to the normal operation of batteries, motors, and sensors, especially in the extremely cold conditions at night, which restrict the survival capacity of electronic equipment. Due to the stringent requirements for carrying capacity in Mars exploration missions, the rotorcraft must adopt lightweight and highly integrated designs while minimizing weight without compromising structural integrity and the reliability of the power system. The communication delay between Mars and Earth can last several minutes, resulting in the real-time ground control unfeasible, so the rotorcraft must possess fully autonomous navigation capabilities. Without GPS support on the Martian surface, the rotorcraft needs to achieve high-precision positioning in a GPS-denied environment employing technologies such as visual navigation, inertial measurement, and terrain matching. In response to the low Reynolds number and high Mach number working conditions of rotor blades in Martian thin atmosphere, an optimization design of the rotor configuration is conducted to improve the lift-to-drag ratio and aerodynamic efficiency of the blades. This includes the optimization of blade airfoils, planform shapes, and twist angle distributions suitable for the Martian environment; A Martian Atmosphere Simulator (MAS) is constructed, allowing for continuous and controllable adjustments of atmospheric composition and pressure. Additionally, a series of prototype models named as the “MarsBird” are developed, providing key flight detection technologies for China’s second phase of Mars sampling return mission [6].

4）Asteroid Anchoring and Sampling (2017~2025) : Asteroids are named as “living fossils” of the solar system, as they preserved the history of the early formation and evolution of the solar system more completely. China’s Tianwen-2 mission will break through traditional exploration modes, which plans to achieve anchor and sample return from the near-Earth asteroid named 2016 HO3 with a diameter of 40~100 m. This goal far exceeds the existing asteroid exploration missions internationally. Internationally a total of 17 asteroid exploration missions are conducted, with thirteen being flybys and four involving contact sampling. Japan’s Hayabusa and Hayabusa2, as well as OSIRIS-REx of the United States, all employed a ‘touch-and-go’ exploration approach, which briefly contacted the asteroid’s surface without establishing a long-term and reliable anchoring between the spacecraft and the asteroid. China’s Tianwen-2 mission aims not only to anchor but also to sample, proposing the higher exploration requirements. The main research activities include the following: In terms of anchoring and sampling, the mechanisms robotic arm with joint buffer is employed for soft landing and an ultrasonic drilling anchoring sampling scheme are proposed, resulting in low drilling pressure and low-power ultrasonic cross-drilling anchoring technology [7][8]. This serves as the implementation plan supporting the national project for asteroid exploration engineering. In terms of asteroid anchoring, a claw-impaling anchoring scheme is proposed [9]. This approach utilizes the interlocking between the claw-impaling and the surface material of the asteroid to achieve stable anchoring of the spacecraft on low-gravity bodies. It effectively prevents the spacecraft from deviating from the asteroid’s surface due to minor disturbances, providing a stable operational platform for subsequent sampling activities. In terms of asteroid sampling, a disc cutter sampling and gas-blowing sample transfer scheme are proposed. This approach utilizes the high-speed rotation of symmetrically arranged disc cutters and gas-assisted sample transfer to achieve the cutting of surface samples and efficient transport under low-gravity conditions [10].

• Ultrasonic Drive and Control

Ultrasonic engineering can be divided into two main fields: power ultrasound and detection ultrasound. Power ultrasound generally operates below 60 kHz, with power capacities ranging from several tens to several hundred kilowatts. It is an application that utilizes ultrasonic waves to induce changes in objects and their properties. Since 2012, the research team initiated the direction of ultrasonic-driven control, focusing on the development of new types of power ultrasound working devices, explored the interaction mechanisms between ultrasonic waves and media, and promoted the application of ultrasonic technology in various fields. A high-frequency crushing ultrasonic drilling device is developed, which features a compact size, low power consumption, low drilling pressure requirements, a wide temperature range (−200 to 500°C), and no need for lubrication. These outstanding advantages make it more suitable than traditional electromagnetic motor-driven drilling for planet soil operations on planetary surfaces under weak gravitational conditions [11]. The team developed impact ultrasonic drills, rotary impact ultrasonic drills and an ultrasonic generator featuring frequency tracking, provided key technical support for the engineering project of the Tianwen-2 spacecraft. Face to automotive wiring harnesses, power batteries, new energy and other fields, ultrasonic welder for wire harness, ultrasonic spot welder, ultrasonic tube sealing welder, and ultrasonic mental roll welder are developed. In the domain of geological analysis and mass spectrometry detection, the research team developed an ultrasonic rock sample crusher, which has the following significant advantages compared with the traditional ball mill crushers: It has a high crushing efficiency, allowing rock samples to be rapidly crushed to sub-micrometer particles (≤10 µm); It has a good particle uniformity, ensuring the accuracy of mass spectrometry analysis; It can reduce the grinding medium cross-contamination, improving sample purity and ensuring the reliability of analytical data. The equipment can be employed for the preparation process of rock samples before they are analyzed by mass spectrometry, significantly improving the efficiency and quality of sample processing in the laboratory. The research team broke through several technical bottlenecks in key areas surrounding ultrasound-driven control technology, promoting the innovative development of ultrasound technology from deep aerospace exploration to new energy manufacturing and geological analysis. In the future, with the further development of ultrasonic engineering, these technologies will unlock greater application potential in more industries, including healthcare, aerospace, and others.

• Load Simulation and Testing

Since 2005, the first lunar rover wheel motion characteristics test bench in China was successfully developed, marking the official launch of research in the direction of load simulation and testing. The planetary anchoring and sampling mechanisms must operate stably in the extremely harsh conditions of space, including high vacuum, extreme temperatures, and strong radiation. To ensure high reliability of the mechanisms in the complex environments, it is necessary to develop specialized test bench and systems, and to conduct thorough experimental validation on the ground. Through long-term engagement in the development of load simulation and testing system, a profound understanding of mechatronic system design was accumulated, and a comprehensive “Fifteen-Step Method for Mechatronic System Design” was formulated. This method achieves the synchronized design of mechanical systems and electronic control systems, allowing for their organic integration. Additionally, based on years of research experience, a professional textbook titled “Mechatronic System Design” is published, providing systematic theoretical guidance for engineering practice in this field. The load simulation and testing of precision shaft systems are crucial in mechanical systems, as they directly affect the transmission quality of the shaft system. Load simulation is typically divided into active load simulation and passive load simulation: passive load simulation mainly involves rotary loading through brakes to simulate external resistance; active load simulation relies on motors for active loading, allowing the system to simulate real load conditions under different operating scenarios. During the load testing process, the torque sensor is a key tool that can accurately quantify the torque transmitted by the shaft system. In response to the core technical challenges in this field, significant breakthroughs are achieved in ultra-low range torque sensor technology, resulting in the development of both static and dynamic torque sensors, thereby filling the technological gap in this area within China. This breakthrough not only improves the capabilities for high-precision load testing but also is widely applied in engineering practices across multiple industries. The table below lists some of the successfully developed testing systems that are effectively utilized in actual engineering applications.

References

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