Transactions of China Electrotechnical Society  2024, Vol. 39 Issue (18): 5680-5691    DOI: 10.19595/j.cnki.1000-6753.tces.231093
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A Mechanical Resonance Suppression Strategy for Two-Inertia Elastic Servo Systems Based on a Phase Locked Loop-Type Extended State Observe
Wu Chun, Wang Chao, Zheng Luhua, Nan Yurong
College of Information Engineering Zhejiang University of Technology Hangzhou 310023 China

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Abstract  In a two-inertia servo system, mechanical resonance is generated due to an elastic part in the connection device between a motor and a load. Consequently, suppressing mechanical resonance has become a focus for achieving high-performance servo control. One effective strategy is notch filters, which can attenuate the magnitude of the resonance frequency. Nevertheless, the design of the notch filter requires accurate knowledge of the mechanical resonance frequency, which is a complex task. As a result, the use of the notch filter is limited due to the difficulties in obtaining an accurate mechanical resonance frequency.
The observer-based method for suppressing mechanical resonance does not require identifying the mechanical resonance frequency. Present studies adopt the observer method for mechanical resonance suppression, where the observer estimates and compensates in real time. According to the extended state observer (ESO), a new approach named the phase-locked loop type ESO (PLL-ESO) is proposed. The state equations of the PLL-ESO are designed based on the system’s kinetic equations, and the stability of the PLL-ESO is verified based on the pole location of state equations. A comparative analysis assesses the resonance suppression performance of the ESO and the PLL-ESO. The theoretical analysis indicates that the PLL-ESO method exhibits a larger phase margin of stabilization and faster dynamic performance than the ESO method.
The experiment aims to evaluate the effectiveness of PLL-ESO in suppressing mechanical resonance compared with notch filters and the ESO. The resonance frequency is identified by applying a sinusoidal sweep signal to the q-axis current reference. A fast Fourier transform (FFT) analysis of the q-axis current response and the real speed are performed on the sampled data to obtain the frequency characteristics of the two-inertia system. It confirms that an elastic connection causes mechanical resonance. A design procedure is established for implementing a resonance suppression strategy. Experiments are conducted under no load and rated load conditions. The results show that the notch filter method can effectively suppress mechanical resonance under no load but cannot wholly succeed in the rated load condition. The ESO method successfully suppresses mechanical resonance under no load and rated load conditions. However, its performance does not satisfy a fast dynamic response requirement. The PLL-ESO method demonstrates superior dynamic performance and achieves faster suppression. Under no load and rated load conditions, the PLL-ESO method reduces transient time by 10 ms and 40 ms to reach steady states compared with the ESO method. Additionally, experiments with different undamped natural frequencies of the PLL-ESO and the ESO reveal that the PLL-ESO method owns high bandwidth and large phase margin for the same pole configuration. Therefore, the PLL-ESO has vast frequency range choices of suitable undamped natural frequencies, especially in addressing inaccurate system parameters and shifted resonance frequencies. The impact of parameter b0 on the performance of the PLL-ESO is also analyzed. It is observed that decreasing b0 slows down the system’s dynamic response while maintaining effective resonance suppression. Conversely, increasing b0 has a weak effect on dynamic response but reduces the suppression of mechanical resonance. In conclusion, compared with the notch filter and ESO methods, the proposed PLL-ESO-based method effectively suppresses mechanical resonance.
Key wordsTwo-inertia elastic servo system      mechanical resonance      phase locked loop-type extended state observer (PLL-ESO)      resonant frequency     
Received: 11 July 2023     
PACS: TM921.2  
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Wu Chun
Wang Chao
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Nan Yurong
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Wu Chun,Wang Chao,Zheng Luhua等. A Mechanical Resonance Suppression Strategy for Two-Inertia Elastic Servo Systems Based on a Phase Locked Loop-Type Extended State Observe[J]. Transactions of China Electrotechnical Society, 2024, 39(18): 5680-5691.
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