Video-based measurement, as one of the most common noncontact measurement methods for industrial inspection, has been developed rapidly. Digital video cameras offer the benefit of low cost, high automation, and are capable to make the simultaneous full-field measurement. This article focuses on studying the microvibrational signal extraction for high-speed rotating machinery with digital cameras. An improved phase-based motion extraction and learning-based video magnification are proposed for measuring the microvibration with high frequency and small amplitude. The phase-based motion extraction is improved by directly transforming the phase variations into the displacement without the computation of phase gradient. Furthermore, the learning-based motion magnification is utilized to amplify and qualitatively measure the microvibration in specified frequency bands. The phase-based motion extraction is a quantitative measurement, while the learning-based video magnification is a qualitative measurement. Experimental results for microvibration measurement rising from a magnetically suspended motor system validate the effectiveness of the proposed method.

Phase-Based Noncontact Vibration Measurement of High-Speed Magnetically Suspended Rotor

The rotor system of magnetically suspended control moment gyro (MSCMG) inevitably has unbalanced amount due to errors in its materials and processing accuracy. The mass unbalance of the rotor will cause the system to generate synchronous vibration and then transmit it to the spacecraft platform through the base, which will seriously affect the imaging quality. The realization of synchronous vibration suppression depends seriously on the rotor speed signal. When the Hall speed sensor has a large measurement error or fails, it is necessary to adaptively estimate the rotor speed to suppress the unbalance vibration of the rotor system. This paper proposes an improved adaptive frequency estimation (IAFE) method. This algorithm uses the characteristics of the rotor radial displacement sensor signal to adaptively estimate the rotor speed, and then suppress the synchronous current generated by the control system. It maintains the stability of the system by changing the phase shift angle at different frequencies, and the residual displacement stiffness force is also compensated. The simulation results show that the proposed method is easy to be implemented, and it can achieve high-precision suppression of unbalanced vibration.

Synchronous Vibration Suppression of Magnetically Suspended Rotor System Using Improved Adaptive Frequency Estimation

Field dynamic balancing for active magnetic bearings supporting rigid rotor shaft based on extended state observer

Video cameras are capable to collect high-density spatial data as each pixel is a sensor. An issue is that the video data is difficult to convert into the motion information, such as displacement. This paper presents a novel camera-based vibration measurement methodology for the lightweight structure. First, the phase-based motion extraction method is improved by directly transforming the phase variations into the displacement without the computation of phase gradient. The displacement is then converted into acceleration information to describe the vibration. Moreover, the proposed vibration measurement is investigated for a lightweight structure without attached sensors to change the physical properties. The measurements of the acceleration signals from camera and accelerometer are compared for verification. The experimental results for the effect of mass-loading, different camera parameters and down-sampling on the measurement validate the effectiveness of the proposed method.

Camera-Based Micro-Vibration Measurement for Lightweight Structure Using an Improved Phase-Based Motion Extraction

For the unbalance vibration of the rigid rotor system on active magnetic bearings (AMBs) supported high-speed motors in the full rotational speed range, a method based on the polarity switching tracking filter (PSTF) and the disturbance observer (DO) is proposed to achieve vibration suppression. To identify the synchronous unbalance vibration, a positive polarity tracking filter and a negative one are adopted before and after the rigid critical rotational speed range, respectively. The rigid critical rotational speed is in this range whose lower/upper limit is the negative/positive polarity switching frequency. Although the PSTF can effectively reduce the rotor vibration when it rotates at subcritical rotational speed range and supercritical range, the vibration increases evidently and even destabilize the system within the rigid critical rotational speed range. It means that the PSTF cannot suppress the rotor unbalance vibration in the full rotational speed range. However, this vibration during the rigid critical rotational speed range can be considered as a kind of disturbance and the DO is adopted to observe it, then the vibration identified is compensated in the control current to reduce the rotor unbalance vibration in the rigid critical rotational speed range. Therefore, the method based on the PSTF and the DO can suppress the unbalance vibration in the full rotational speed range. Finally, simulation and experiment results demonstrate that the method proposed can effectively suppresses the synchronous unbalance vibration of the AMBs-rigid rotor system in the full rotational speed range.

Vibration Suppression for Magnetically Levitated High-Speed Motors Based on Polarity Switching Tracking Filter and Disturbance Observer

The vibration suppression in the presence of gyroscopic effects is an important issue for safe operations in magnetic bearing levitated varying speed rotor system. This paper proposes a synchronous vibration control method with a two-stage notch filter for the magnetically suspended rotor system with strong gyroscopic effects. First, the dynamics of the magnetically suspended rotor system with synchronous vibrations in the rotational motion is modeled. Then the proposed two-stage notch filter is designed and the solution of the two-stage switching point is derived to distinguish low speed and high speed. Stability analysis is also presented in the low-speed region and the high-speed region, respectively. Finally, simulation results demonstrate that the stability can be guaranteed by adjusting the phase shift angle of the notch filter over the entire speed range. Further experimental results confirm the effectiveness of the proposed suppression method.

Kun Wang

Papers

A Two-Stage Synchronous Vibration Control for Magnetically Suspended Rotor System in the Full Speed Range