Research On The Bias Control Of Electrohydraulic Vibrator Based On 2D Valve

Vibration table is a standard test equipment, which provides typical vibration conditions and is used for testing and evaluating the mechanical properties of engineering equipment. The performance of vibration table has a great impact on the progress of various areas. So the exploration of higher frequency range and greater output force has been the main task in the development of vibration table. In the electrohydraulic vibrator based on 2D valve, the movement of piston in the cylinder is controlled by the oil from 2D valve. Since 2D valve is rotary, the frequency and amplitude of cylinder in electrohydraulic vibration exciter is regulated by the spool's rotational speed and axial slide in 2D valve. In order to control offset independently and to get asymmetric load, a scheme of adding a bias valve in parallel to cylinder is proposed to control the offset. This paper is focused on the bias control in the 2D exciter. The main contributions of this thesis are as follows.1. For the asymmetric load in 2D exciter, a scheme is proposed to control the offset in which a bias valve is added in parallel to 2D exciter.2. The mathematical model of 2D exciter's hydraulic power structure is established. The coupling relationship among frequency, amplitude and offset are studied through simulation and analytic methods. The impact of frequency and the spool axial of bias valve on amplitude and that of frequency and the opening of 2D valve on offset are analyzed.3. The experimental equipment is established, from which the vibration-exciting displacement signals are obtained. Interactions among frequency, amplitude and offset are discussed, and the experimental results and theoretical studies are analyzed and compared.4. It is concluded that frequency, amplitude and offset can be controlled independently in 2D exciter. Before the flow is saturation in cylinder, offset follows a linear law with the spool axial of bias valve. When the opening is nearly 50%, the slope decreases. At a lower frequency, the impact of frequency on offset is significant, the higher the frequency, the greater the offset. At a higher frequency, there is no saturation and frequency has little effect on offset. At the same time, when the opening of bias valve is fixed, the greater the opening of 2D valve, the smaller the offset.5. In this paper, offset can be controlled precisely and the independent control of frequency, amplitude and offset in 2D exciter is realized. In the future, more work can be done to improve the damping ratio and eliminate resonance, to achieve non-sinusoidal excitation waveform, and to achieve higher-frequency electro-hydraulic excitation.