gfeng Guan

Random vibration control of a hydraulic shaking table

A multi-input multi-output (MIMO) random vibration control method is proposed for a multi-axis hydraulic shaking table system to replicate the reference power spectral density (PSD). Kinematics analysis is presented to reduce cross-coupling between the axes of the hydraulic shaking table. The time histories generated by time domain randomization in conventional MIMO random vibration control have spectral leakage between the frequency resolutions. The drive signal PSD is used in the proposed control method to design a linear time-invariant system. Circular convolution is then proposed to implement the designed system and convert the PSD to time histories with white noise. Experimental results obtained in step response and two-axis PSD replication show the effectiveness of the proposed control method.

Multi-input multi-output random vibration control of a multi-axis electro-hydraulic shaking table

An online multi-input multi-output (MIMO) random vibration control method is presented for a multi-axis hydraulic shaking table system to replicate the reference acceleration power spectral density (PSD) by the reproduction of the acceleration time domain histories that are proportional to the reference. The offline iterations are implemented using conventional random vibration control to compensate for the changes in the frequency response function (FRF) of the system. The successful test mainly depended on the experience of the operator. In online MIMO random vibration control, the reference PSD is transformed into time domain histories by filtering white noise. The impedance matrix of the shaking table system, which is the inverse of the FRF, is calculated and updated online. The time histories are compensated based on the system impedance matrix and then used as the drive signals to the shaking table. The overlap-save method and fast Fourier transformation are proposed to implement the transformation and compensation online. Two-axis random vibration experimental results obtained with the proposed control method show that both the reference PSD and the time domain histories can be replicated with high precision in the output of the shaking table without operator intervention.

Adaptive random control of a two-axis redundantly actuated electro-hydraulic shaking table

An adaptive random control method is presented for a two-axis redundantly actuated electro-hydraulic shaking table system to replicate the reference acceleration power spectral density (PSD). The redundant force controller is developed to reduce the cross-coupling among the actuators. The offline iterations are implemented in conventional random control to compensate for the changes in the frequency response function of the system. Stability and responsiveness of control are determined by operator-selected parameters. In adaptive random control, the reference PSD is transformed into time domain histories by filtering white noise. The adaptive finite impulse response (FIR) filters are used to model and track the inverse system online. The weights of the FIR filters are updated by the forgetting factor recursive least-squares algorithm. The time histories are corrected by the copy of the inverse model. Experimental results obtained in step response and PSD replication demonstrate the effectiveness of the proposed control method.

Vibration control of multiaxis hydraulic shaking table

The control system of 3 axis, 6 degree-of-freedom (DOF) hydraulic shaking table with 8 actuators is presented to reproduce the multiple DOF reference waveforms. The servo control is used to expand the acceleration frequency bandwidth and transform signals between the 8 actuators and 6 DOF. The multi input multi output (MIMO) vbiration control is presented to update the drive signals and reproduce the reference waveform in high precision. The MIMO waveform replication control test results on one hydraulic shaking table demonstrate the effectiveness of the proposed algorithm.

Servo controller design for two degrees of freedom redundant drive shaking table

A servo controller for redundant force is designed based on DOF shaking table. Firstly, according to the geometric position of hydraulic cylinders, the composition and decomposition matrix are achieved. Secondly, in order to reduce the coupling on shaking table, which derives from redundant force within the system, force transformation matrix is calculated. Thirdly, a three-variable controller is utilized to control the acceleration of shaking table, which provides the system higher bandwidth of acceleration response, better stability and higher damping ratio. In the final part of this paper, the related real-time control system is developed based on XPC target box, and a shaking control experiment is conducted to testify the effectiveness of the servo controller designed in this paper.

Random vibration control based on adaptive filter

The random vibration adaptive control method is presented based on the recursive least-squares (RLS) adaptive filter. The power spectral density (PSD) of drive signal is updated based on the off-line identification of frequency response function (FRF) in conventional random vibration control system. And the pseudo-random drive signal generated by the conventional time-frequency transformation has leakage between frequency resolutions. The control precision is difficult to meet with conventional random vibration control method. The finite impulse response (FIR) filter is designed with the reference PSD in random vibration adaptive control system. And the time domain drive signal is generated by filtering a series of independent white noise. The RLS adaptive filter is designed to obtain the inverse model of the device under test (DUT) based on adaptive inverse control algorithm. The time domain drive signal is filtered by the inverse model so the PSD of the DUT output signal can replicate the reference PSD in high precision. Random vibration test results show the effectiveness of the proposed algorithm.

Adaptive control of random vibration test system

The random vibration adaptive control method is presented based on the Kalman adaptive filter to improve the control precision of random vibration test system. The Kalman adaptive filter is used to obtain the on-line inverse model of the device under test (DUT). The time domain signal having a reference power spectral density (PSD) is updated by the inverse model. The reference PSD is replicated by the reproduction of the time domain signal at the output of the DUT. The random vibration adaptive control is developed and used for the PSD replication in the hydraulic vibration table. Test results shows that the algorithm is favorable to improve the control precision of random vibration control system.

6 Degree-0f-Freedom Long-Term Waveform Replication Control

The multi-input multi-output (MIMO) long-term waveform replication control is presented to reproduce the long- term reference waveform and further enhance the effectiveness of multi degree-of-freedom (DOF) vibration qualification test. When the duration of the reference waveform is long enough that can not be processed within a single fast Fourier transform (FFT) frame, the conventional MIMO transient waveform control algorithm can only take the typical part-time duration as the reference waveform. In MIMO long-term waveform control algorithm, the drive signals is segmented into subsequences and updated in each based on MIMO circular convolution. And then the whole long-term reference waveform can be replicated in high precision. The improved algorithm is applied to the acceleration waveform replication on the 6 DOF hydraulic vibration table. Test results verify the performance of the algorithm. Keywords-MIMO system; circular convolution; 6 DOF hydraulic vibration table; waveform replication control