The agile collaborative control technology of non-contact satellite based on laser precision measurement (<italic>inner cover paper·invited</italic>)

Significance With the continuous advancement of satellite remote sensing technology, the observation capabilities of high-resolution Earth remote sensing satellites and deep-space astronomical observation satellites have been significantly improved. The aperture of the world’s largest space telescope has reached 6.5 meters, and the space telescope currently under development in China has also achieved an aperture of 4 meters, both with angular resolutions reaching the micro arcsecond level. When observing the faint ground or space targets, the integration time often needs to be as long as hundreds of milliseconds or even seconds, which requires the camera to have "ultra-precise and ultra-stable", or "ultra-quiet" pointing capability during imaging. For example, the large-scale mapping satellite requires a pointing accuracy of 5×10−4 (3σ) and an attitude stability of 5×10−6 (°)/s (3σ), which far exceed the 0.01° (3σ) pointing accuracy and 5×10−4 (°)/s (3σ) stability achievable by current traditional remote sensing satellite platforms. The main factors restricting the ultra-precise and ultra-stable control capability of satellite platforms are the vibration disturbances from moving components such as on-board reaction wheels, control moment gyros (CMGs) and mechanical cryocoolers, as well as flexible components including solar arrays, large deployable antennas, and large lens hoods. Effective vibration isolation or suppression measures are therefore essential. Traditional vibration isolation methods primarily adopt passive isolation via spring-damper mechanical isolation systems, which can effectively isolate high-frequency vibrations but have limited effectiveness in isolating low-frequency vibrations from flexible solar arrays and antennas. To achieve broadband vibration suppression, more effective vibration isolation control methods are required. Domestic research institutions have successively proposed hybrid active-passive control methods, such as the Stewart isolation platform and the contactless magnetic levitation control method. The platform module and payload module of a contactless "magnetic levitation" satellite are connected via contactless magnetic levitation mechanisms, achieving thoroughly dynamic-static isolation between vibration sources and the payload, and fundamentally cutting off the vibration transmission path to the payload module. On-orbit verification via satellites such as the Chinese H-alpha Solar Explorer(CHASE), CHASE has demonstrated that this technology can realize "ultra-precise and ultra-stable" control. In pursuit of ultra-high precision, high-resolution, these kinds of remote sensing satellites or astronomical observation satellites typically have a narrow observation field of view. To improve the on-orbit observation efficiency, these satellites are required to have agile on-orbit pointing capability. Restricted by factors such as the internal magnetic field strength and product size of contactless magnetic levitation mechanisms, the relative movement gap between the two modules is usually on the millimeter scale. How to achieve agile coordinated maneuvering while controlling the relative position of the two modules within the millimeter range poses significant challenges to the high-precision relative measurement of the two modules and the design of coordinated maneuvering strategies. To meet the requirements of ultra-precision, ultra-stability, and ultra-agility for contactless satellite platforms, a relative pose calculation method based on laser measurement and a contactless satellite agile coordinated control technology is proposed. Semi-physical simulation verification shows that this technology can achieve high-precision, high-stability, and fast stable coordinated control of the attitudes of the two modules, providing technical support for subsequent engineering applications.Progess First, based on magnetic levitation actuators and laser displacement sensors, a fully orthogonal dynamic model of the contactless two-module attitude was established. Second, a solution model for the relative position and attitude of the two modules based on 8 high-precision laser displacement sensors was proposed, which can real-timely and jointly solve and calculate the relative position and attitude of the two modules, and evaluate the system redundancy. Third, a three-loop coordinated control law including the coordinated attitude maneuver control of the two modules and the relative position control was designed to meet the requirements of fast coordinated maneuvering between the platform and the payload module, as well as the fast stable control of the payload module. Finally, simulation verification of the control algorithm was carried out. The results show that the contactless satellite agile coordinated control algorithm based on high-precision laser measurement can achieve pointing accuracy at the level of 10−4 (°) and stability control at the level of 10−5 (°)/s, and have the improving capability of 10−6 (°)/s. It can also reduce the stable time after maneuvering from the minute level of traditional platforms to the second level. Meanwhile, it can ensure a sufficient safe distance for the relative position of the two modules during attitude maneuvering and stable control process, which can meet the on-orbit high-performance and high-efficiency imaging control requirements of high-precision and quantitative remote sensing satellites.Conclusions and Prospects A design and solution method for obtaining the relative pose between the payload module and the platform module of a contactless satellite through high-precision inter-module laser measurement is proposed. Including the designs of an agile maneuver control law for the coordinated operation of the two modules and a translational control law for the relative position of their centers of mass. Simulation results verify the effectiveness of the coordinated maneuvering strategy for contactless satellites. Compared with traditional platforms, this technology offers higher pointing accuracy and stability, as well as faster maneuvering and stable control capabilities. It can provide technical support for subsequent engineering applications such as large-scale mapping satellites and deep-space astronomical observation satellites.