Wide-band disturbance rejection technique of dual observer for an inertially stabilized platform

Bian Qihui; Miao Qingqing; Tang Tao; Ma Haotong

doi:10.12086/oee.2025.240305

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Bian Q H, Miao Q Q, Tang T, et al. Wide-band disturbance rejection technique of dual observer for an inertially stabilized platform[J]. Opto-Electron Eng, 2025, 52(3): 240305. doi: 10.12086/oee.2025.240305

Citation:

Bian Q H, Miao Q Q, Tang T, et al. Wide-band disturbance rejection technique of dual observer for an inertially stabilized platform[J]. Opto-Electron Eng, 2025, 52(3): 240305. doi: 10.12086/oee.2025.240305

Wide-band disturbance rejection technique of dual observer for an inertially stabilized platform

1.
National Key Laboratory of Optical Field Manipulation Science and Technology, Chinese Academy of Sciences, Chengdu, Sichuan 610209, China
2.
Key Laboratory of Optical Engineering, Chinese Academy of Sciences, Chengdu, Sichuan 610209, China
3.
Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu, Sichuan 610209, China
4.
University of Chinese Academy of Sciences, Beijing 100049, China

Fund Project: National Natural Science Foundation of China (62375267)

More Information

^*Corresponding author: taotang@ioe.ac.cn
CSTR: 32245.14.oee.2025.240305

Received Date 23 December 2024

Revised Date 10 February 2025

Accepted Date 11 February 2025

Published Date 28 March 2025

Abstract

Abstract

Increasing the active vibration isolation capability between the optical payload and the motion platform has always been a challenge for optoelectronic tracking systems. Therefore, a dual observer method is proposed to achieve wide-band disturbance rejection for an inertially stabilized platform. The dual observer method consists of two aspects. Firstly, a classical error observer has a strong low-frequency suppression ability through the design of a low-pass filter. Secondly, a saturated acceleration disturbance observer improves its disturbance suppression characteristics and completes the rejection of medium and high-frequency disturbances by adjusting the saturation threshold and filter bandwidth according to its stability conditions. The dual observer combines both advantages, and the interaction between the two observers is analyzed for better parameterization. Closed-loop verification of the proposal is carried out using the inertial stabilization device. The experimental results show that the dual observer can improve the closed-loop performance under both single-frequency and mixed-frequency disturbances.
- inertially stabilized platform /
- disturbance rejection /
- error observer /
- saturation limiting /
- dual observer

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References

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Overview

Overview

Inertially stabilized platforms (ISPs) are the servo systems used to isolate disturbances and point to targets, which are currently widely utilized in fields such as aerial remote sensing, optoelectronic tracking, and target recognition. However, ISPs are inevitably affected by disturbances caused by the movement/rotation/vibration of motion carriers, so disturbance suppression has become an urgent problem for ISPs to solve. At present, the mainstream method of ISP disturbance suppression is feedback control combined with other control algorithms, such as feedforward control, sliding mode control (SMC), active disturbance rejection control (ADRC), fuzzy control, etc. However, these methods have problems, such as the need for additional sensors, the introduction of chattering, and the need for many parameters. The error observer is designed by optimizing the sensitivity function based on error observation, which enables the system to have strong low-frequency disturbance rejection capability. Nevertheless, the stability condition limits the error observer bandwidth, so the frequency range of disturbance rejection is not high. As an active disturbance rejection method, disturbance observer (DOB) is widely adopted. Due to the limited bandwidth of traditional DOB, current researches on DOB are mostly focused on improving the structure and thus enhancing the transfer function characteristic. So, a saturation module is introduced into the acceleration disturbance observer. According to the stability condition, the filter bandwidth is increased by adjusting the saturation limit threshold. This allows the observer to sacrifice some low-frequency suppression effects while increasing the suppression of medium- and high-frequency disturbances. Therefore, a dual observer is proposed without compromising stability, which combines the error observer and the saturated acceleration disturbance observer within a single loop to achieve wide-band disturbance suppression. The interaction between the two observers is also analyzed. The existence of the error observer depresses the saturation threshold. If the saturation observer wants to increase the threshold, the error observer bandwidth needs to reduce. The two complement each other and restrict each other. In addition, the disturbance suppression capability of dual observers under different observer parameter selections is analyzed to provide more options for various application scenarios. The experimental results show that the dual observer combines the advantages of both and improves the system's closed-loop performance under both single-frequency and mixed-frequency disturbances. At the same time, the experimental results also confirm the restrictive relationship between the two observers.