Design Optimization of a Compact Double-Ended-Tuning-Fork-Based Resonant Accelerometer for Smart Spindle Applications

Abstract

With the rapid developments of the Industrial Era 4.0, numerous sensors have been employed to facilitate and monitor the quality of machining processes. Among them, accelerometers play an important role in chatter detection and suppression for reducing the tool down-time and increasing manufacturing efficiency. To date, most commonly seen accelerometers have relatively large sizes such that they can be installed only on the housing of spindles or the surfaces of workpieces that may not be able to directly capture actual vibration signals or obstruct the cutting process. To address this challenge, this research proposed a compact, wide-bandwidth resonant accelerometer that could be embedded inside high-speed spindles for real-time chatter monitoring and prediction.Composed of a double-ended tuning fork (DETF), a proof mass, and a support beam, the resonant accelerometer utilizes the resonance frequency shift of the DETF due to the bending motions of the structure during out-of-plane accelerations as the sensing mechanism. The entire structure based on commercially available quartz tuning forks (QTFs) with electrodes for symmetric-mode excitations. The advantages of this structure include low noise and wide operation bandwidth thanks to the frequency modulation scheme. A theoretical model and finite element analysis were conducted for designs and optimizations. Simulated results demonstrated that the proposed accelerometer has a size of 9.76 mm × 4.8 mm × 5.5 mm, a simulated sensitivity of 0.94 Hz/g, and a simulated working bandwidth of 3.5 kHz. The research results are expected to be beneficial for chatter detection and intelligent manufacturing.Micromachines 2020, 11, 42 2 of 11 highly reliable, and low-cost sensors are in high demand in the era of the internet of things (IoT). The commonly used accelerometer transducer mechanisms include capacitive [8], piezoresistive [9], and piezoelectric [10,11] mechanisms, all of which produce an output voltage or charge proportional to the measured acceleration. While capacitive and piezoresistive transducers suffer from a relatively weak mechanical-electrical conversion efficiency and a higher power consumption, respectively, piezoelectric transducers surpass the other two mechanisms with a higher transducer efficiency and no standby power. For a typical piezoelectric accelerometer, acceleration will cause the proof mass to exert a force on the beam or film, creating a charge due to piezoelectric effect. However, most resonant type accelerometers have relatively large sizes and are usually installed on the housing of spindles or the stage of workpiece holders.The goal of this research is to design a compact, resonant-type accelerometer for chatter detections. In general, the rotation speed of high-speed spindles can be as high as 30,000 rpm (i.e., 500 Hz), and chatter frequencies usually occur near the operation frequencies with several harmonics. For chatter detections, the working bandwidth of a measuring accelerometer should be 7 times the operation frequency, which is ...

Finite Element Analysis for Design Optimization of MEMS Double Ended Tuning Fork Resonator

“…In the anti-phase vibrational mode for DETF resonators, the coupling stiffness between two tines is smaller than the stiffness of each tine. Hence resonant frequency for DETF resonators can be deduced with the approximations of doubly clamped beams (17). The formula for the desired characteristic resonant frequency of antiphase mode can be obtained by equation given below (18).…”