This paper presents a novel approach to the design of an active suspended handle by identifying the effective frequency range, based on the saturation effects of the piezo stack actuator, in terms of the force-displacement-voltage relationship as a function of the excitation frequency. The effective range allows for proper matching between the operating speed of the machine and the suspended handle. A model of the active suspended handle was developed, which took into account the non-linear saturation effect of the piezo stack actuator. A proportional-integral-derivative controller generated the counter voltage for the piezo stack actuator, using a proportional feedback gain (P) step up method, in order to attenuate the vibration transmitted to the handle. By including the saturation effect, the Pearson’s correlation coefficient ( R2) of the model improved to 0.97, within the frequency range of 50 ∼ 500 Hz. Using this approach, we identified that the effective frequency range of isolation with transmissibility less than unity is between 250 ∼ 450 Hz. The active suspended handle was attached to a die grinder with a nominal operating speed of 25000 rpm and the vibration transmitted from the die grinder to the handle was reduced by 91%.
Heating, ventilating and air conditioning (HVAC) system is one of the major sources for the vehicle noise and vibration, which subsequently contribute to the bad acoustical environment. The components of the HVAC system can produce a significant level of vibration during the operation and contributed to an unwanted noise. As the vibration of HVAC components get worse, it will be transferred to other components and excites the natural frequencies of the HVAC system. Natural frequencies of the components are depending on the mass and stiffness of the HVAC components and the value can been modify using these two parameters. This study is focusing on the specific type of HVAC noise and vibration problem and the counter measure has been perform by implementing the structural dynamic modification (SDM) method to the air conditioning (AC) pipe. The lab-scale of the vehicle HVAC system is set up to represent the actual HVAC system with the real vehicle operation. Noise and vibration of the HVAC system in the system level are measured and compared. From this data, the Dynamic Vibration Absorber (DVA) is designed and applied at the AC pipe of the HVAC system. The result shows that, the natural frequency of the AC pipe can be shifted which resulting a wide effective frequency range of 100-500 Hz. The effect of DVA on the HVAC system is observed during operation whereby a significant vibration attenuation has been achieved for operating frequency range of 100-300 Hz.
Dam reliability analysis is conducted to access the integrity of dam structure and thus to prevent dam failure. This paper presents the numerical reliability study of reservoir banks of water dam by the mean of fluid/structure interaction (FSI) simulation. Through FSI, the hydrostatics effect of the water in reservoir on the wall of dam was successfully simulated and identified. From the current numerical work, relatively stagnant water on the dam bank was observed, with the increasing water pressure along the water depth. Subsequently, localized high stress and deformation on the dam structure was successfully identified, and suitable countermeasures were being recommended. For the current investigated dam bank structure, the highest deformation and stress detected are respectively 1.185 mm and 3.12 MPa. Therefore, at present operating configuration, it is concluded the bank would not exhibit any failures.
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