Okda, Sherif (2024)
Development of Actuator-Amplifier Systems for Active Vibration Control of Gearboxes.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00027879
Dissertation, Erstveröffentlichung, Verlagsversion

Kurzbeschreibung (Abstract)

Reducing carbon emissions stands as a paramount goal in the global effort to combat climate change. Reducing a vehicle’s weight enhances efficiency and reduces emissions significantly. However, this approach presents a challenge as lighter vehicles experience higher vibrations and noise emission levels. As a result, vehicle manufacturers are investing in addressing these issues to maintain passenger comfort standards and comply with regulatory requirements. This study presents the development and evaluation of an active vibration control system designed to minimize the transmission of vibrations to the car cabin, by actively countering vibrations in the gearbox housing and effectively limiting their transfer through the transmission mounts. The system is designed to specifically address the high-frequency vibrations that occur at the meshing frequency of the transmission and its harmonics, with an emphasis on cost-effectiveness, lightweight construction, and compact design tailored for automotive applications. The research focuses on the comprehensive development of both the actuator and power amplifier components of the active vibration control system, ensuring an integrated approach to improve vehicle comfort and performance. An inertial mass actuator is developed to counteract the housing vibrations, utilizing a piezoelectric stack selected as the active element, due to its superior performance and reliability at high frequencies. The actuator design, validated through Simulink modeling and experimental testing, achieves a remarkable balance of generated force, efficiency, lightweight construction, and compact dimensions. Additionally, a switching amplifier is developed, through the modification of a bidirectional buck-boost converter for efficient DC/AC conversion through the manipulation of its feedback loop. This design demonstrates high efficiency and compact dimensions, making it well-suited for automotive applications. An innovative test-rig is constructed to accurately replicate gearbox vibration phenomena, offering an economical alternative to complex setups. The developed test-rig is excited by a piezo stack actuator at the input shaft. Rigorous testing on the newly developed rig demonstrates significant vibration reduction across a broad frequency spectrum, particularly notable above 2500 Hz. However, there are some difficulties in controlling vibrations at certain frequencies. An average reduction of approximately 8.5 dB is achieved between 1000 Hz and 1500 Hz, an average reduction of approximately 14 dB is obtained between 1500 and 2500 Hz, and an average reduction of 10.8 dB is achieved between 2500 and 5000 Hz. The active vibration control system is also tested on an operational gearbox showing its ability to reduce the highest acceleration peak at the mounting point by approximately 40 dB. Subsequent to the validation of the active vibration control system, a novel concept of integrating piezoelectric shear actuators into the gearbox housing is introduced, presenting advantages such as reduced weight, lower power consumption, and improved accommodation. Two designs are developed utilizing single and double-shear actuators. Simulation and experimental validation on a simple plate structure effectively demonstrate the effectiveness of the shear actuators in vibration suppression. The single shear actuator design demonstrated reductions in vibration levels equivalent to approximately 34 dB when targeting the first local bending mode, While the double shear actuator design targeting the first and second local bending modes achieved a reduction equivalent to approximately 36 dB at steady state when targeting the first bending mode and approximately 41 dB is achieved at steady state by targeting the second bending mode.

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