In high speed and high precision machining applications, it is important to monitor the machining process in order to ensure high product quality. For this purpose, it is essential to develop a dynamometer with high sensitivity and high natural frequency which is suited to these conditions. This paper describes the design, calibration and performance of a milling torque sensor based on piezoresistive MEMS strain. A detailed design study is carried out to optimize the two mutually-contradictory indicators sensitivity and natural frequency. The developed torque sensor principally consists of a thin-walled cylinder, and a piezoresistive MEMS strain gauge bonded on the surface of the sensing element where the shear strain is maximum. The strain gauge includes eight piezoresistances and four are connected in a full Wheatstone circuit bridge, which is used to measure the applied torque force during machining procedures. Experimental static calibration results show that the sensitivity of torque sensor has been improved to 0.13 mv/Nm. A modal impact test indicates that the natural frequency of torque sensor reaches 1216 Hz, which is suitable for high speed machining processes. The dynamic test results indicate that the developed torque sensor is stable and practical for monitoring the milling process.

This paper proposes a multidirectional piezoelectric vibration energy harvester based on an improved U-shaped structure with cross-connected beams. Benefitting from the bi-directional capacity of U-shaped beam and additional bending mode induced by cross-connected configuration, the proposed structure can well capture the vibrations in 3D space at the frequencies lower than 15 Hz. These features are further validated by finite element analyses and theorical formulas. The prototype is fabricated and the experiments under different conditions are carried out. The results show that the proposed harvester can generate favorable voltage and power under multidirectional vibrations at a low operating frequency. Practical applications of charging capacitors and powering a wireless sensor node demonstrate the feasibility of this energy harvester in supplying power for engineering devices.

In this study, an innovative orthogonal decagonal ring three-dimensional cutting force sensor (ODRCFS) was designed to address the insufficient static and dynamic performance assessment of cutting force sensors during high-speed cutting. First, the viability of the sensor structure was established and the prototype was fabricated by theoretical analysis and simulation verification. Then the strain gauges were pasted to the orthogonal decagonal ring before the prototype was tested for performance and cutting force measurement. The test results showed that the orthogonal decagonal ring three-dimensional cutting force sensor has a sensitivity of 4.9×10 ^-2 mV/N, 5.2×10 ^-2 mV/N, and 1.1×10 ^-2 mV/N in the F_c , F_f , and F_p measurement directions, respectively, which is 3.62, 3.56, and 5.11 times higher than that of the octagonal ring cutting force sensor in each direction. The natural frequencies of F_c , F_f , and F_p are 1605Hz, 1611Hz, and 3733Hz, respectively, which is 39% higher than that of the octagonal ring cutting force sensor in the F_c direction, indicating that the ODRCFS can sensitively reflect the change in cutting parameters during cutting.

To meet the measurement needs of multidimensional high-g acceleration in fields such as weapon penetration, aerospace, and explosive shock, a biaxial piezoresistive accelerometer incorporating tension–compression is meticulously designed. This study begins by thoroughly examining the tension–compression measurement mechanism and designing the sensor’s sensitive structure. A signal test circuit is developed to effectively mitigate cross-interference, taking into account the stress variation characteristics of the cantilever beam. Subsequently, the signal test circuit of anti-cross-interference is designed according to the stress variation characteristics of the cantilever beam. Next, the finite element method is applied to analyze the structure and obtain the performance indices of the range, vibration modes, and sensitivity of the sensor. Finally, the process flow and packaging scheme of the chip are analyzed. The results show that the sensor has a full range of 200,000 g, a sensitivity of 1.39 µV/g in the X direction and 1.42 µV/g in the Y direction, and natural frequencies of 509.8 kHz and 510.2 kHz in the X and Y directions, respectively.

Harmonic drive is susceptible to strength failure and performance degradation failure during operation. Given the long life test cycles, limited sample size, and incomplete understanding of degradation laws, this study conducted comprehensive life test and performance degradation test research to enable future failure prediction and reliability assessment for harmonic drive. Building upon established test rigs for a HD life test and performance degradation test, a step-down accelerated life test methodology was developed. Life tests under step-down accelerated conditions were executed, with a concurrent performance degradation test throughout the life test. Key datasets acquired include vibration signal histories, degradation data for critical performance indicators such as stiffness, precision, transmission efficiency, and backlash. Test results show that the predominant strength failure in the atmospheric environment is flexspline fatigue fracture, while significant degradation occurred in stiffness, precision, and backlash across all test conditions; transmission efficiency showed gradual degradation before strength failure followed by a marked decline post-failure. Finally, the failure mechanism of strength and performance degradation is analyzed, and the mechanism consistency of the two failures is verified by Hilbert envelope spectrum analysis and degradation trajectory shape consistency, respectively. The results from this paper provide critical data support and a reference foundation for the proactive maintenance of the harmonic drive.

The accurate measurement of film pressure distribution in water-lubricated bearings (WLBs) is crucial as it offers insights into bearing traits, like bearing capacity and the lubrication status. The prevailing testing method involves drilling holes into the shaft to redirect water, and incorporating pressure sensors. These sensors communicate their signals via a wireless sensor node (WSN). However, traditional power supply methods for the WSN - namely, battery power, slip ring conduction, and self-power - do not provide the continuity, safety, and stability needed under rotational conditions. To overcome this, our study proposes a contactless power supply method for the film pressure WSN that can provide stable and continuous power under rotating conditions, and avoid safety risks posed by friction and wear of the slip ring. Next, we designed and produced a magnetic coupler which underwent static and dynamic tests on an actual WLBs test bench. The test results revealed that the coupler can generate 13.429W power with a 5mm air gap following a Series-Parallel (SP) compensation, reaching an efficiency of 88.64%. This surpasses the efficiency rates reported in recent studies. Additionally, the system’s voltage fluctuation on the actual test bench is a mere 0.55% within the range of 50 to 500 rpm, which demonstrates excellent stability. While this system is primarily engineered for the film pressure WSN, it may also be applicable to other rotating equipment, thereby broadening its practical use scope.