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Introduction: The electric drive system is usually composed of an electric motor and gear transmission system, and widely used for industrial applications. However, the dynamic behaviors of the coupled electromechanical system are still not well understood, especially when there are faults in the system. Purpose: The faults such as gear spalling fault of the mechanical system or inter-turn short-circuit fault of electrical device will threaten the operation safety of the electric vehicle. Thus, the faulty dynamic analysis for the electric drive system is crucial for avoiding fatal catastrophes. Method: In this paper, the permeance network motor model with inter-turn short-circuit fault and the dynamic planetary gear transmission model considering spalling faults are proposed, respectively. The electromechanical dynamic model integrating two models mentioned above is employed to acquire the fault characteristics. Then, the vibration characteristics of the electric drive system with and without gear fault or inter-turn fault under the effects of time-varying mesh stiffness, slot effect and magnetic saturation are distinguished at different operation conditions. Results: The results show that the inter-turn short-circuit fault can trigger conspicuous harmonics within the low frequency domain of the mesh force components, which will predicatively obstruct the detection or diagnosis of the spalling fault. Moreover, the vibration characteristics and vibration mechanism concerning these faults are revealed by the frequency and statistical analysis, which facilitates the condition monitoring for the gear transmission system when the tooth spalling and inter-turn faults are coupled. Conclusion: The research results bring theoretical reference for the dynamic analysis and vibration-based condition monitoring of the vehicles’ integrated electric drive system.

The high speed and high power density electromechanical system for the electric vehicle is urgently required to meet stricter emission regulation and achieve higher performance. Therefore, the electromechanical coupling effect is becoming more strengthened and may significantly degrade the performance of the motor and gear system. When gear or motor failures like gear tooth crack or rotor bar breakage are present, the operation safety of the electric vehicle would be threatened. So the exploration of the fault features for the motor-gear system is crucial for prevention of disastrous consequences. In this paper, the fault vibration features of the motor-gear system with gear root crack and motor rotor error under various excitations from both motor and gear transmission system are investigated. The electromechanical dynamic model considering the nonlinear air-gap permeance and time-varying mesh stiffness is employed, and the gear tooth root crack fault and the rotor bar breakage are integrated into the dynamic model to acquire the dynamic characteristics with faults. Then, the angular-synchronous average technique is applied to strengthen the statistical characteristics of fault vibration signal and eliminate the effect of speed variation due to the external excitation. The statistical indicators extracted from the angular-synchronous average vibration signals can reveal the progression of gear faults for the gear transmission without motor rotor error. However, the analyzed results indicate that the popular statistical indicators would fail to detect the early tooth fault when the motor rotor error is coupled.

Traditional two-dimensional transition metal carbides/nitrides (MXene) have gained much academic concern due to their excellent physicochemical properties, but their susceptibility to self-stacking leads to poor cyclic stability. In this paper, an MXene-based electrode active material was successfully prepared. The generated modified PPy (g-PPy) increases the active site, increases the accessibility of ions, and can give full play to the pseudocapacitance. By the combination of modified PPy (g-PPy) nanoparticles with pseudocapacitive behavior polymerized in situ on sulfonated cellulose (SC) and MXene, not only the electrochemical performance was improved by exploiting the synergy between different electrode materials and different energy storage mechanisms, but also the MXene as a skeleton limited the volume expansion and contraction of PPy during charge/discharge cycles and the g-PPy and SC composites (g-PPy@SC) as a spacer supported the MXene layer, resulting in much higher cycle stability. Cycle stability of 98.4 % even after 10,000 cycle tests. In addition, a symmetric supercapacitor assembled from this electrode material maintains a stability of 84.4 % under 10,000 cycles at a low temperature of −40 °C. Therefore, this study provides a feasible method for the preparation of MXene-based electrodes with high cycling stability.

Precise measurement of temperature is important in studies of chemical and biological systems as reaction kinetics are almost universally sensitive to temperature. However, the use of conventional temperature probes can introduce an exogenous temperature disturbance resulting in measurement artifacts. Infrared pyrometry is a noninvasive technique for temperature measurement, however, the challenge for current infrared pyrometry is low sensitivity to small temperature variations, which in many cases precludes determination of key diagnostic information. Here, we report a sensitive differential infrared pyrometer based on spatial modulation using a resonant oscillating mirror, which enables a sensitivity to temperature variations on the microkelvin scale. The instrument is employed to monitor minuscule heat evolution in an acid–base reaction and the decomposition of H2O2by bovine liver catalase. The instrument holds great promise for monitoring the dynamics of heat evolution in a range of chemical and biological systems in a completely noninvasive manner.

Two-dimensional material MXene (Ti3C2Tx) with multilayer structures is widely used in supercapacitors, but their structures tend to pile up and limit their performance. Therefore, a strategy is provided to synthesize the random copolymer aniline-co-pyrrole (ANPY) by in-situ polymerization of aniline and pyrrole on the MXene. The self-stacking of MXene materials can be prevented, and ANPY can be used as the intermediate layer to modulate MXene nanosheets forming more ion migration channels, which can improve the electrochemical performance of ANPY/MXene. MXene is used as a “backbone” for ANPY to adjust the chain space configuration of polymer molecules. The prepared ANPY/MXene electrodes have a high specific capacitance of 451.75 F/g increasing by 39 % on the original PANI electrode. PVA/MXene gel electrolyte and ANPY/MXene electrode are assembled to form a flexible supercapacitor capable of 91.8 % capacitance retention after 5000 cycles. It suggests that the ANPY/MXene material provides a new idea for preparing supercapacitors with good electrochemical performance.

In this paper, MXene based electrode active materials and MXene cross-linked polyacrylic acid hydrogel electrolytes with high cycling performance and high specific capacitance have been successfully prepared. Polyaniline with high capacitance values has been grown on the MXene surface by in situ polymerization, which can significantly improve electrochemical properties. As the MXene surface is rich in functional groups, it can be used as a nucleation site for in situ polymerization of aniline monomers deposited. The PANI filled with MXene forms a 3D porous conductive network reducing the self-stacking of MXene and providing a large number of channels for electrolyte ions to enter MXene. The supercapacitor has been tested and assembled with good flexibility and the specific capacitance has risen to 222 F g−1. The capacitance retention of 98.5 % after 10,000 charges and discharges is due to the improved performance of the composite material and the excellent stability of the gel electrolyte and electrodes. The above results show that the prepared electrodes and devices have promising applications in flexible wearable devices.

An electromechanical system consisting of an electric motor and planetary gear set is modeled and analyzed in this paper. The model integrates various internal excitations including time-varying gear mesh stiffness, nonlinear spatial effect and, saturation effect, and component flaws. The simulation results predict the effects of rotor and gear faults including broken rotor bar, rotor static and dynamic eccentricity, and tooth root crack of the gear on the electromechanical system behavior. It is verified as the results obtained are in accordance with the features derived within previous researches. Furthermore, new sidebands merged on the dynamic response spectra such as slip frequency harmonics, rotor rotational frequency harmonics, and fault-related rotational frequency harmonics can be applied to detect electrical and mechanical faults in the motor-gear system. This paper lays the foundation for the comprehensive further study of working condition monitoring for the motor-gear system.