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In this paper, a new closed-loop charge-pump circuit with adjustable output voltage and an on-chip compensation technique is proposed. The environmental temperature and process corner can be detected with an on-chip detection circuit and automatically feedback an adjusted reference voltage. With this, the magnitude of the charge-pump output voltage with Pulse-Width Modulation (PWM) can be compensated. The charge-pump circuit is designed and verified with a 180 nm Bipolar-CMOS-DMOS (BCD) process, and its output voltage at different process, voltage, and temperature (PVT) is controllable with low ripple. There are three selections for adjusting the output voltage: +5 V/+7 V/+10 V shifts, with the supply voltage ranging from 5 V to 32 V. It can remain tunable and stable at any shifts. The maximum deviation is ±0.265%, and the maximum load current can reach 30 mA. The ripple voltage is less than 0.3% (Δ Vripple/Vout) underthe maximum load. The Monte Carlo simulation results show that the worst case of the process sensitivity (σ/μ) is 0.1%. The charge-pump core area is 0.308 mm2, and the power consumption is 4.753 mW. The circuit can produce high-precision output and is suitable for high-side driving IC applications.

Tuned Mass Dampers (TMDs) are widely used in human-induced vibration control of footbridges. When they are tuned to the footbridges' fundamental frequency, they have good effects in vibration control. However, TMDs are highly sensitive to deviations in the natural frequency of footbridges, which leads to mistuned TMDs and their control effects will decrease sharply. Traditional in-service TMDs used in the footbridges cannot retune themselves. In this paper, a new TMD named Adaptive-Passive Variable Mass TMD (APVM-TMD) is proposed, which is an upgrade device of the formally invented Self-Adjustable Variable Mass TMD (SAVM-TMD). It can retune itself through varying its mass by an acceleration sensor, a microcontroller and actuating devices, without any manual operations. The structural acceleration under ambient excitation is recorded and processed by an acceleration sensor and a microcontroller, then the footbridge's fundamental frequency can be identified by Short-Time Fourier Transformation (STFT) – based algorithm. Subsequently, the microcontroller will retune the APVM-TMD by controlling actuating devices to vary its mass. The performance of APVM-TMD is studied via both experimental studies and numerical simulations under different human-induced excitations. The damper's working performance with an identified frequency, optimal frequency and structural actual frequency is investigated, and the influencing parameters (e.g., mass ratio, optimal frequency ratio and damping ratio) are studied. The detailed comparative study and the advantages of APVM-TMD over SAVM-TMD are highlighted. The results show that the proposed APVM-TMD can easily retune its frequency with little power consumption. Although the footbridge frequency may change for certain reasons, this damper can still effectively reduce structural acceleration response and increase equivalent damping ratio. APVM-TMD is better than SAVM-TMD in the robustness, economy and operational convenience.

Floor structures, especially large-span floor structures, are sensitive to human-induced vibrations, which might cause a serviceability problem. Multiple tuned mass damper (MTMD) system is often used in the vertical vibration control of large-span floor structures. While it is difficult to determine the design parameters of each TMD in an MTMD system, a passive MTMD system still has the detuning shortcoming. In order to overcome this problem, an adaptive-passive variable mass multiple TMD (APVM-MTMD) system is proposed in this study. Each APVM-TMD in the system has a variable mass configuration and a microcontroller system consisting of an accelerometer, a control circuit board, and a driving device. Under ambient excitation, the control circuit board gathers the signals of the accelerometer on the floor, which can identify the dominant natural frequency of the primary structure where this APVM-TMD is located; this is done through the short time Fourier transformation (STFT)-based frequency identification algorithm. Then, each APVM-TMD can automatically control the driving device to retune itself by varying its mass. After retuning steps of all APVM-TMDs, the previous MTMD system becomes a new MTMD system with a different frequency distribution. A large-span floor structure is proposed as a case study. The original finite element model (FEM) is updated according to the in-situ test. In the updated model, an APVM-MTMD system is designed according to the previous model, then the frequency retuning function is verified. Finally, by applying several kinds of human-induced excitations, the vertical vibration control effect of the retuned MTMD system is compared with the mistuned one. The results show that the APVM-MTMD system can retune itself, and the retuned MTMD system has the best vibration control effect compared to the case without control and the mistuned MTMD system case.

Tuned mass damper (TMD) is a widely used vibration control device, consisting of a mass, some springs and damping elements. Viscous damper is mostly used as a damping element; however, it has many unsustainable problems, e.g., poor durability, sensitive to the change of temperature, difficult to adjust the damping, oil leakage etc. In this paper, a new sustainable adaptive-passive eddy current tuned mass damper (ECTMD) with variable damping, which is very easy to be further upgraded to a semi-active one, is proposed. Four important parameters, e.g., adsorption position of permanent magnets, thickness of the conductive plate, thickness of the extra steel plate and the air gap between permanent magnets and the conductive plate are investigated by a parametric study. Two new evaluation indexes are put forward to indicate the damping mechanism of the proposed device. The relationship between effective damping coefficient and air gap is fitted through a quadratic function. Then, the corresponding design method of the proposed adaptive–passive ECTMD is presented. At last, the previous adaptive–passive ECTMD is upgraded to a semi-active one, which can adjust its eddy current damping through adjusting its air gap in real-time, based on the linear-quadratic-Gaussian algorithm. The effectiveness of semi-active ECTMD is evaluated through harmonic excitations and human-induced excitations. The results show that the semi-active ECTMD with variable damping has a better vibration control effect than the optimized passive one.

Tuned mass damper (TMD) has a wide range of applications in the vibration control of footbridges. However, the traditional engineering design method may lead to a mistuned TMD. In this paper, an improved TMD design method based on the model updating is proposed. Firstly, the original finite element model (FEM) is studied and the natural characteristics of the in-service or newly built footbridge is identified by field test, and then the original FEM is updated. TMD is designed according to the new updated FEM, and it is optimized according to the simulation on vibration control effects. Finally, the installation and field measurement of TMD are carried out. The improved design method can be applied to both in-service and newly built footbridges. This paper illustrates the improved design method with an engineering example. The frequency identification results of field test and original FEM show that there is a relatively large difference between them. The TMD designed according to the updated FEM has better vibration control effect than the TMD designed according to the original FEM. The site test results show that TMD has good effect on controlling human-induced vibrations.

Tuned mass damper (TMD) has a wide application in the human-induced vibration control of pedestrian bridges and its parameters have great influence on the control effects, hence it should be well designed. A new optimization method for a TMD system is proposed in this paper, based on the artificial fish swarm algorithm (AFSA), and the primary structural damping is taken into consideration. The optimization goal is to minimize the maximum dynamic amplification factor of the primary structure under external harmonic excitations. As a result, the optimized TMD has a smaller maximum dynamic amplification factor and better robustness. The optimum TMD parameters for a damped primary structure with different damping ratios and different TMD mass ratios are summarized in a table for simple, practical design, and the fitting equation is also provided. The TMD configuration optimized by the proposed method was shown to be superior to that optimized by other classical optimization methods. Finally, the application of an optimized TMD based on AFSA for a pedestrian bridge is proposed as a case study. The results show that the TMD designed based on AFSA has a smaller maximum dynamic amplification factor than the TMD designed based on the classic Den Hartog method and the TMD designed based on the Ioi Toshihiro method, and the optimized TMD has a good effect in controlling human-induced vibrations at different frequencies.

Summary Tuned mass dampers (TMDs) represent a quite mature technology for controlling human-induced vibrations of footbridges, when they are tuned to the primary structure's fundamental frequency. However, the TMD is very sensitive to even a small change in the tuning ratio. This paper proposes a novel TMD named self-adjustable variable mass TMD (SAVM-TMD), which is capable of varying its mass and retuning its frequency on the basis of the acceleration ratio between the primary system and the TMD. The accelerations are obtained from two acceleration sensors, and the frequency adjustment is achieved by using a microcontroller and actuating devices. The acceleration ratio limit value should be set in the microcontroller firstly, and when the adjustment begins, the microcontroller will retune the TMD to a reasonable frequency region, under a specific harmonic excitation. The SAVM-TMD can be regarded as a passive control device capable of adjusting its frequency. The performance of SAVM-TMD is studied via both experimental studies and numerical simulations under different pedestrian excitations. It is found that the SAVM-TMD is effective in reducing the response and improving the equivalent damping ratio of the primary system when the structural frequency changes, with little power consumption. The results obtained from the experimental studies and the numerical simulations agree with each other very well. More pedestrian vibration situations are studied in the numerical simulations, and the results also show that the SAVM-TMD has excellent performance in controlling human-induced vibrations.