Search Results (16)

Thermal management remains a key challenge for lithium-ion batteries in electric vehicles, especially under transient driving and charging conditions. This study develops a coupled thermo-hydraulic model for a liquid-cooled battery thermal management system and uses it to compare four coolants with different thermophysical properties: water, ethylene glycol–water, propylene glycol–water, and Jet-A aviation fuel. Unlike studies that focus mainly on temperature reduction, the present work evaluates battery temperature, hydraulic pump power, and cooling load/heat rejection demand within the same framework. The coolants are tested under the FTP-75 driving cycle and a high-rate charging case while pump speed is varied between 1500 and 4500 rpm. Water provides the strongest cooling performance, reducing the battery temperature during FTP-75 from about 30 °C to 21.2 °C at 1500 rpm and 20.6–20.8 °C at 4500 rpm. During charging, water maintains the battery temperature near 23 °C at 1500 rpm, whereas ethylene glycol–water and Jet-A reach about 46–47 °C. Increasing pump speed improves thermal regulation, particularly for weaker-performing coolants, but it also increases auxiliary demand; for example, the RMS pump power of water during charging rises from 0.039 to 0.735 kW. Overall, the results show that coolant selection in liquid-cooled BTMS requires a balanced assessment of heat removal capability, pumping demand, and heat rejection requirements. Full article

Vapor compression heat pump technology is a widely utilized method for energy conversion. Lubricating oil plays a crucial role in the heat pump system cycle by effectively reducing wear on the compressor’s moving parts and preventing refrigerant leakage. However, it can also create an oil film in the heat exchange equipment, which increases thermal resistance and diminishes heat transfer efficiency. This study utilizes a vapor compression heat pump system test bench to investigate factors influencing the system’s oil circulation rate, the two-phase flow patterns of refrigerant and lubricating oil, and the impact of oil circulation on system performance. The findings reveal that as the compressor speed increases, the oil circulation rate initially decreases before increasing again. Additionally, a decrease in the evaporator’s heat load leads to a reduction in oil circulation at high temperatures, while it increases at low temperatures. Furthermore, increasing the opening of the electronic expansion valve results in a gradual decrease in the oil circulation rate, whereas an increase in the refrigerant charge correlates with a rise in the oil circulation rate. The oil return flow pattern can primarily be categorized into three states: slow oil return, oil film flow, and high-speed oil return. These patterns are closely related to the degree of superheat, with lower superheat levels intensifying oil return. Full article

This paper presents an innovative powertrain design and an energy regeneration system for hybrid hydraulic excavators to reduce energy consumption and emissions. The proposed system is designed to maximize engine efficiency and make full use of the energy gained from boom and arm retraction. The powertrain features an innovative design that incorporates a continuously variable transmission (CVT), which drives the main pump. It enables precise control of both the engine’s speed and torque, ensuring that the engine operates within the high-efficiency range. The energy regeneration system is applied to regenerate the potential energy of the boom and arm, which can be used to either charge the battery or directly supply power to the main pump. Moreover, an energy management strategy based on an equivalent consumption minimization strategy is used to distribute the power while offering maximum engine efficiency. When compared with the existing hybrid system and conventional system, the simulation results indicated that the proposed approach achieves energy-saving efficiencies of $16.9\%$ and $77.1\%$, respectively, at high velocities and $22.25\%$ and $53.5\%$, respectively, at medium velocities. This research signifies a promising advancement for sustainable and efficient hydraulic excavator operations. Full article

This paper presents the design and performance analysis of a wideband charge-pump phase-locked loop (CPPLL) characterized by low reference spur and low phase noise. The proposed CPPLL, operating as a wideband phase-locked loop (PLL) with a reference frequency of 100 MHz, achieves a wide tuning range of 40% from 2.0 GHz to 3.0 GHz. A clock feedthrough suppressed charge pump with additional bias current branches is used to reduce the PLL’s loop reference spur. The 4-stage current mode logic (CML) divide-by-2/3 circuit is utilized in the frequency divider to achieve high-speed frequency division. The circuit of an AND gate and latch in the 2/3 divider adopts a full differential symmetric structure to minimize the phase error of high-frequency differential signals. The voltage-controlled oscillator (VCO) is designed to provide a wide tuning range while optimizing the trade-off between the phase noise and power consumption. The fabricated PLL is implemented using a 0.13 µm CMOS process. Experimental measurements reveal a reference spur of −74.39 dBc at an oscillation frequency of 2.4 GHz. Moreover, the CPPLL achieves phase noise of −102.55 dBc/Hz@100 kHz and −127.15 dBc/Hz@1 MHz, while consuming 33.6 mW under a 1.2 V supply voltage. The integrated root-mean-square (rms) jitter, measured from 10 kHz to 10 MHz, is 340.99 fs, and the figure-of-merit (FoM) is −234.08 dB at a carrier frequency of 2.4 GHz, highlighting the potential of the proposed PLL for integrated circuit applications. Full article

This paper presents a single-channel 12-bit, 2 GS/s pipelined analog-to-digital converter (ADC) for wideband sampling receivers. The design adopts a novel source follower input buffer with multiple feedback loops to improve sample linearity and extend bandwidth. Additionally, an improved two stages charge pump amplifier topology is introduced, which doubles the Gain Bandwidth Product (GBW) without consuming additional power. To address the back-end ADC and background calibration, a multi-level dither strategy is employed, utilizing a new high-speed and low-cost uniform distribution pseudorandom code generator. The prototype ADC fabricated in 40 nm CMOS process achieves 68.24 dB SFDR up to Nyquist frequency with a sampling rate of 2 GS/s. Measurement results demonstrate a bandwidth exceeding 5 GHz, resulting in a Schreier FOMs of 152.4 dB. Full article

As major projects such as nuclear power plants continuously increase, it is inevitable that loopholes will arise in safety precautions. Airplane anchoring structures, comprising steel joints and acting as a key component of such a major project, directly affect the safety of the project due to their resistance to the instant impact of an airplane. Existing impact testing machines have the limitations of being unable to balance impact velocity and impact force, as well as having inadequate control of impact velocity; they cannot meet the requirements of impact testing for steel mechanical connections in nuclear power plants. This paper discusses the hydraulic-based principle of the impact test system, adopts the hydraulic control mode, and uses the accumulator as the power source to develop an instant loading test system suitable for the entire series of steel joints and small-scale cable impact tests. The system is equipped with a 2000 kN static-pressure-supported high-speed servo linear actuator, a 2 × 22 kW oil pump motor group, a 2.2 kW high-pressure oil pump motor group, and a 9000 L/min nitrogen-charging accumulator group, which can test the impact of large-tonnage instant tensile loading. The maximum impact force of the system is 2000 kN, and the maximum impact rate is 1.5 m/s. Through the impact testing of mechanical connecting components using the developed impact test system, it was found that the strain rate of the specimen before failure was not less than 1 s⁻¹, meeting the requirements of the technical specifications for nuclear power plants. By adjusting the working pressure of the accumulator group, the impact rate could be controlled effectively, thus providing a strong experimental platform for research in the field of engineering for preventing emergencies. Full article

In this paper, we describe the upgrade of a small electrostatic dust accelerator located at the University of Stuttgart. The newly developed dust source, focusing lens, differential detector and linac stage were successfully installed and tested in the beam line. The input voltage range of the dust source was extended from 0–20 kV to 0–30 kV. A newly developed dust detector with two differential charge sensitive amplifiers is employed to monitor particles with speeds from several m/s to several km/s and with surface charges above 0.028 fC. The post-stage linac provides an additional acceleration ability with a total voltage of up to 120 kV. The entire system of this dust accelerator works without protection gas and without a complex high voltage terminal. The volumes to be pumped down are small and can be quickly evacuated. The new system was used to accelerate micron- and submicron-sized metal particles or coated mineral materials. Improvements in the acceleration system allow for a wider variety of dust materials and new applications. Full article

In this paper, we present a successive approximation register (SAR) analog-to-digital converter (ADC) with a charge-pump (CP) phase-locked loop (PLL) and a bootstrapped switch, also called PLL-SAR ADC. To meet system-on-chip (SOC) and industrial requirements, the proposed SAR ADC and the control circuits of electric vehicles must be integrated into a single chip and be fabricated using the TSMC 0.25-μm 1P3M complementary metal oxide semiconductor (CMOS) high-voltage process. It is difficult to implement a high-speed SAR ADC with the TSMC 0.25-μm CMOS high-voltage process because it includes an N-type buried layer, which shorts all p-type metal oxide semiconductor field-effect transistor (PMOSFET) bodies together to withstand high voltages. In the proposed PLL-SAR ADC, two clock signals, an external clock signal and an internal clock signal from the CP-PLL, are provided to guarantee that a correct clock signal is fed. This design improves the robustness of the designed system. A monotonic capacitor-switching procedure is considered to reduce power consumption. Furthermore, a bootstrapped switch was added along with a dummy switch and a dummy transistor to eliminate disturbances in the input voltages and to improve the device’s anti-noise capability. Moreover, a two-stage dynamic comparator was used to prevent kickback noise induced by the parasitic capacitors. The measurements indicate that the signal-to-noise-and-distortion ratio, effective number of bits, power consumption, and chip area are 53.82 dB, 8.65 bits, 1.256 mW, and 1.261 × 0.975 mm², respectively. The FoM is approximately 0.625 pJ/conv-step at 1.256 mW, 8.65 bits, and 5 MS/s. The high sampling rate of 5 MS/s and high accuracy of 8.65 bits are the main advantages of the proposed PLL-SAR ADC. Full article

The electro-hydrostatic actuator (EHA) is a type of highly integrated, compact, closed pump control drive system composed of a servo motor, a metering pump, a hydraulic cylinder and other components. Compared with the traditional valve control system, the electro-hydrostatic actuator has the advantages of a high power-to-weight ratio, high integration, environmental friendliness, and superior efficiency and energy saving. However, due to the complex mechanical–hydraulic coupling mechanism of the system and the existence of non-linear multi-source disturbances, the dynamic and static performance of the system is limited, particularly the pressure pulsation phenomenon under low-speed conditions, which seriously affects the high precision control requirements of the system. In order to address the low-speed pressure pulsation problem of the electro-hydrostatic actuator, first, the mathematical models of the servo motor, metering pump and hydraulic cylinder are established, and the simulation model of the EHA system is created based on MATLAB/Simulink. Second, from aspects of the servo motor and the quantitative piston pump, the causes of the pressure pulsation under low-speed working conditions are analyzed, and the parameter selection method of the accumulator is proposed to eliminate the pressure pulsation based on ${\omega }_n$ and $\zeta$ of the EHA system. Finally, the optimal charging pressure of the accumulator is simulated and experimentally analyzed. The simulation and experimental results show that the charging pressure range of the accumulator calculated with this method can effectively improve the pressure pulsation phenomenon of the EHA system under low-speed working conditions, and it plays a positive role in the engineering popularization and application of the EHA system. Full article

Primary control of linear motion by variable speed electric motors driving a hydraulic cylinder via a constant displacement pump is an established and successful concept with a frequent use in industry. One problem arises when low or zero motion speed has to be realized under high pump pressure conditions. Such load scenarios occur frequently in certain pressing processes, e.g., for sintering or veneering. Most pumps have a lower speed limit, below which critical tribological conditions occur which impair lifespan and efficiency. In addition, pump speed control and pump fluctuation suffer from the mixed lubrication conditions in such an operation range. For a circumvention of such low speed pump operation, a digital valve control concept is presented and studied in this paper. Valve control is used in load holding phases with low speed. Pressure is provided by an accumulator which is charged by the pump in short charging cycles at reasonable pump speeds. It is shown that the mean control error during load holding phase lies within the desired band and the fluctuations of the control force are lower than those of the pump control. In addition, the unfavorable pump operation conditions can be avoided via digital control. Full article

As the supply voltage decreases, there is a need for a high-speed negative charge pump circuit, for example, to produce the back-bias voltage (V_BB) with high pumping efficiency at a low supply voltage (V_DD). Beyond the basic negative charge pump circuit with the small area overhead, advanced schemes such as hybrid pump circuit (HCP) and cross-coupled hybrid pump circuits (CHPC) were introduced to improve the pumping efficiency and pump down speed. However, they still suffer from pumping efficiency degradation, low level |V_BB|, and small pumping currents at very low V_DD. A novel negative charge pump using an enhanced pumping clock is proposed. The proposed cross-coupled charge pump consists of the enhanced pumping clock generator (ECG) having a pair of inverters and PMOS latch circuit to produce an enhanced control signal with a greater amplitude, thereby working efficiently especially at low supply voltages. The proposed scheme is validated with a HSPICE simulation using the TSMC 180 nm process. The proposed scheme can be operated down to V_DD = 0.4 V, and |V_BB|/V_DD is obtained to be 86.1% at V_DD = 0.5 V and C_load = 20 nF. Compared to the state-of-the-art CHPC scheme, the pumping efficiency is larger by 35% at V_DD = 0.6 V and R_L = 10 KΩ, and the pumping current is 2.17 times greater at V_DD = 1.2 V and V_BB = 0 V, making the circuit suitable for very low supply voltage applications in DRAMs. Full article

Multiple important physical parameters in the vanadium redox flow battery are difficult to measure accurately, and the multiple important physical parameters (e.g., temperature, flow, voltage, current, pressure, and electrolyte concentration) are correlated with each other; all of them have a critical influence on the performance and life of vanadium redox flow battery. In terms of the feed of fuel to vanadium redox flow battery, the pump conveys electrolytes from the outside to inside for reaction. As the performance of vanadium redox flow battery can be tested only by an external machine—after which, the speed of pump is adjusted to control the flow velocity of electrolyte—the optimum performance cannot be obtained. There is a demand for internal real-time microscopic diagnosis of vanadium redox flow batteries, and this study uses micro-electro-mechanical systems (MEMS) technology to develop a flexible five-in-one (temperature, flow, voltage, current, and pressure) microsensor, which is embedded in vanadium redox flow battery, for real-time sensing. Its advantages include: (1) Small size and the simultaneous measurement of five important physical quantities; (2) elastic measurement position and accurate embedding; and (3) high accuracy, sensitivity, and quick response time. The flexible five-in-one microsensor embedded in the vanadium redox flow battery can instantly monitor the changes in different physical quantities in the vanadium redox flow battery during charging; as such, optimum operating parameters can be found out so that performance and life can be enhancec. Full article

Bubble actuated micro-pumps have great potential to be integrated into microfluidic systems to allow the independence of peripheral equipment. Previous studies on bubble actuated valveless micro-pumps have been mainly limited to experimental studies and numerical simulations due to the complex behavior of bubbles. In this paper, the construction of a mathematical model for a bubble actuated valveless micro-pump considering fluid dynamics, heat and mass transfer and bubble dynamics is described. A prototype was fabricated and tested to verify this theoretical model. The morphological evolution of the driving bubbles during the heating process was observed by a high-speed charge-coupled device (CCD) camera, the flow rate produced by the micro-pump under different working conditions was recorded and the test results were explained by the heat dissipation model. The model in this study was able to precisely predict the flow of micro-pumps in different drive modes. The principle behind defining the heating frequency and the duty cycle based on the pump chamber volume was determined. The study shows the mechanism of bubble controlling and the good prospects of bubble actuated valveless micro-pumps. Full article

This study proposes a high-gain reflex-charging-based bidirectional DC charger (RC-BDC) to enhance the battery charging efficiency of light electric vehicles (LEV) in a DC-microgrid. The proposed charger topology consists of an unregulated level converter (ULC) and a two-phase interleaved buck-boost charge-pump converter (IBCPC), which together provide low ripple and high voltage conversion ratio. As the high-gain RC-BDC charges, the LEV’s battery with reflex charging currents, high battery charging efficiency, and prolonged battery life cycles are achieved. This is possible due to the recovering of negative pulse energy of reflex charging currents to reduce charge dissipations within LEV’s batteries. Derivations of the operating principles of the high-gain RC-BDC, analyses of its topology, and the closed-loop control designs were presented. Simulations and experiments were implemented with battery voltage of 48 V and DC-bus voltage of 400 V for a 500 W prototype. The results verify the feasibility of the proposed concept and were compared with the typical constant-current/constant-voltage (CC/CV) charger. The comparison shows that the proposed high gain RC-BDC improves battery charging speed and reduces the battery thermal deterioration effect by about 12.7% and 25%, respectively. Full article

Lean fueling of spark ignited (SI) engines is a valid method for increasing efficiency and reducing nitric oxide (NO_x) emissions. Gasoline direct injection (GDI) allows better fuel economy with respect to the port-fuel injection configuration, through greater flexibility to load changes, reduced tendency to abnormal combustion, and reduction of pumping and heat losses. During homogenous charge operation with lean mixtures, flame development is prolonged and incomplete combustion can even occur, causing a decrease in stability and engine efficiency. On the other hand, charge stratification results in fuel impingement on the combustion chamber walls and high particle emissions. Therefore, lean operation requires a fundamentally new understanding of in-cylinder processes for developing the next generation of direct-injection (DI) SI engines. In this paper, combustion was investigated in an optically accessible DISI single cylinder research engine fueled with gasoline. Stoichiometric and lean operations were studied in detail through a combined thermodynamic and optical approach. The engine was operated at a fixed rotational speed (1000 rpm), with a wide open throttle, and at the start of the injection during the intake stroke. The excess air ratio was raised from 1 to values close to the flammability limit, and spark timing was adopted according to the maximum brake torque setting for each case. Cycle resolved digital imaging and spectroscopy were applied; the optical data were correlated to in-cylinder pressure traces and exhaust gas emission measurements. Flame front propagation speed, flame morphology parameters, and centroid motion were evaluated through image processing. Chemical kinetics were characterized based on spectroscopy data. Lean burn operation demonstrated increased flame distortion and center movement from the location of the spark plug compared to the stoichiometric case; engine stability decreased as the lean flammability limit was approached. Full article