Active Suppression Method Research Articles

Adaptive control design for active Pogo suppression based on vibration-acceleration feedback

The Pogo suppression method can be divided into active suppression and passive suppression. For practical engineering, passive suppression is generally achieved through accumulators, but this method sometimes cannot meet the design requirements of liquid rockets with uncertain model parameters and time-varying parameters. As for active suppression methods, state variables are mostly used as feedback thus leading to poor practical feasibility. In this study, an adaptive Pogo active suppression controller design method is proposed where measured acceleration is used as feedback. The eigenspace transformation theory is utilized to design two types of dimensional reduced models: an observation-oriented dimensional reduced model (O-ODRM) and a control-oriented dimensional reduced model(C-ODRM). The former works for observer design, and its state variables can be reconstructed by measuring only the acceleration and can be input to the adaptive controller after matrix operations. The latter is employed for adaptive controller design, and it can effectively process the issues of model parameter uncertainty and time-varying parameters. To demonstrate the effectiveness of the proposed method, a certain type of rocket was selected as the research object for simulation analysis. The simulation results show that the proposed method, which uses measured acceleration as feedback, can achieve Pogo active suppression for liquid rockets with uncertain and time-varying parameters.

Modelling and control of current full compensation system‐based controllable voltage source

AbstractCurrent active suppression technology of arc overvoltage in distribution network has small capacity of controllable voltage source and complex control and cannot flexibly adjust the zero‐sequence voltage of neutral point. This study proposes a controllable voltage source system to fully compensate the arc current of ground fault for solving these problems. A controllable voltage source model based on passive supply voltage converter is established, utilising Dyn transformer to carry unbalanced load for a long time. The model output voltage is the same amplitude and frequency as that of single‐phase ground fault phase, but opposite phase. The compensation switch is operated when a ground fault occurs. The output voltage amplitude of the controllable voltage source is controlled, the fault phase voltage is controlled to be 0 in the closed loop, the grounding fault arc current is eliminated and the arc grounding overvoltage is suppressed. The control strategy was verified by the PSCAD/EMTDC simulation model of single‐phase grounding fault arc in 10 kV distribution network and the real single‐phase fault experiment platform of 0.4 kV distribution network. Results proved the model and strategy's accuracy and effectiveness. It provides an engineering practical method for active suppression of arc grounding overvoltage in distribution network.

High-Frequency Oscillation of the Active-Bridge-Transformer-Based DC/DC Converter

The dual-active-bridge converter (DAB) has attracted tremendous attention in recent years. However, its EMI issues, especially the high-frequency oscillation (HFO) induced by the dv/dt and parasitic elements of the transformer, are significant challenges. The multi-active-bridge converter (MAB) based on the multi-winding transformer also faces similar problems, which are even more complicated. This article investigates the HFO of active-bridge-transformer-based DC/DC converters including DAB and MAB. Firstly, the general HFO model is studied using the analysis of the AC equivalent circuit considering the asymmetrical parameters. Ignoring the AC resistance in the circuit, the high-order model of the voltage oscillation could be reduced to a second-order system. Based on the simplified model, the oscillation voltage generated by an active bridge is analyzed in the time domain. Then, a universal active voltage-oscillation-suppression method-selected harmonic-elimination phase-shift (SHE PS) modulation method is proposed. The impacts of the system parameters on the method are also revealed. The experimental results show the excellent performance of the proposed active suppression method, with voltage spike amplitude (VSA) reductions of 92.1% and 77.8% for the DAB and MAB prototypes, respectively.

Active Suppression Method of Dangerous Behaviors for Robot-Assisted Vascular Interventional Surgery

The procedure of vascular interventional surgery (VIS) is very complicated. It requires doctors to wear the protecting suits and manipulate the flexible instruments (catheters and guidewires) for a long time to complete the treatment, which may fatigue the doctors and lead to misoperation. Besides, the X-ray radiation in the operating room is also bad for doctors&#x2019; health. So, to solve the above challenges, a novel robot-assisted system was developed for VIS, which realizes the separation of the doctor and the operating room; a preliminary method was used on the slave side to reduce the excessive collision force when the tip of the catheter travels through the curved blood vessel, and the active enhancing safety method of the robot-assisted system was proposed to reduce the danger caused by doctors&#x2019; misoperation (dangerous behaviors) during the surgery. Finally, to verify the proposed methods, a series of experiments <i>in vitro</i> were conducted, and experimental results indicated that the method of assisting the deflection of the tip of the catheter has the potential to reduce the excessive collision force, the collision force at the tip of the catheter was reduced by 0.104 N when a misoperation occurred during the operation procedure under the condition of the active enhancing safety method, and the stronger sense of the tactile presence was generated by the master manipulator when the total force of the slave side was greater than 1.0 N. Therefore, based on the above results, we believe that the proposed methods are effective.

Rate-dependent input curve shaping of the piezoelectric actuator based optical resonator cavity displacement characteristics for an external cavity diode laser.

In an external cavity diode laser, the rate-dependent nonlinearity of the piezoelectric actuator based optical resonator cavity (ORC) restricts its application in high-precision measurements. This paper proposes a rate-dependent nonlinear active suppression method for an ORC system based on the Hammerstein model. Using a back propagation neural network and system identification algorithm, a high-precision rate-dependent Hammerstein model of the ORC system is established. The B-spline curve is used to simplify the input voltage curve, and the optimized voltage curve that can obtain the linear displacement output is solved by the particle swarm optimization algorithm. The experimental results show that in the frequency range of 2-50Hz, the regression coefficients (R2) of the ascent and descent stages at each experimental frequency of the ORC system increased to over 0.9998 and optimized the curve at the inflection pointto suppress the vibration at the inflection point.

Nonlinear energy sink to enhance the landing gear shimmy performance

The shimmy phenomenon is a significant concern in aircraft landing gear dynamics. The prediction of the shimmy instability is an essential issue in landing gear design to develop a passive or active suppression method. This work investigates the application of the nonlinear energy sink (NES) concept to mitigate the effects of shimmy in landing gears. The NES concept has been used in recent research on mechanical vibrations. It comprises a passive target energy transfer method that refers to a one-way energy transfer from a primary to a nonlinear subsystem. The landing gear model is based on torsional displacement coupled with the tyre classical elastic string analogy model. The NES device connects to the wheel shaft, and it comprises a mass, a linear damper, and a pure cubic spring. The numerical integration in time was used to assess the shimmy onset speed and the post-shimmy limit cycle oscillations. A parametric analysis of the landing gear nonlinear dynamics without the NES is presented. The design space of possible NES parameters is given, obeying design constraints, and inspected to assess adequate NES designs. The best NES samples are included in the landing gear dynamics to study their influence. Results have shown that the NES can adequately expand the operational speed range for no shimmy and lead to lower LCO amplitudes in the post-shimmy for a reasonable range of speeds. The NES concept’s successful employment for the landing gear dynamics suggests an enormous potential form of passive shimmy control.

Active Suppression of Piezoelectric Ringing in Pockels Cells for Laser Cavity Application

Pockels cells used as electro-optical modulators in high-power high-repetition lasers suffer from piezoelectric ringing phenomenon due to piezoelectric properties of the crystals. A new method for active suppression of the piezoelectric ringing in Pockels cells is proposed in this work. It is based on symmetric control of Pockels cell using burst of short positive and negative voltage pulses with the same amplitude instead of a single long pulse for light polarization modulation. Rising and falling edges of pulses of the burst induce symmetrical acoustic waves of the opposite phase and cancel the piezoelectric ringing of the crystal. A new high voltage driver capable of generating positive and negative pulses of tens of nanoseconds of 3 kV magnitude was developed for this purpose. The amplitude of laser beam intensity pulsations caused by the piezoelectric ringing can be reduced up to five times when active suppression method is used for the deuterated potassium dihydrogen phosphate (DKDP) Pockels cell. Such crystals like DKDP, LiNbO3, and LiTaO3 may benefit from the proposed method and find new use in lasers of high repetition rate where piezoelectric ringing is a major limiting factor.

Active suppression of swirl-stabilized combustion instability

In this paper, active suppression methods are studied to reduce combustion instability. In particular, a controller is used to output a control signal to a sampled oscillating pressure wave. A control acoustic wave is released from an actuator in opposite phase to the oscillating pressure wave. The two waves superimpose and reduce the oscillating intensity of combustion instability. The experiments suggest that the oscillating pressure presents mutagenicity in combustion instability conditions: the frequency, amplitude, and phase will change suddenly. Moreover, the flame pulsation will also follow the control acoustic wave. Therefore, the output control phase should have a higher refresh frequency. As the novelty of this paper, two methods of phase following/recognition based on FPGA are proposed to suppress oscillating pressure: Sinusoidal approximation and waveform delay, respectively. The former is responsible for identifying the initial phase of the oscillating pressure according to the sampling data every 25 ms, whereas the latter is responsible for suppressing future oscillating pressure by the waveform acquired in the previous period. The results suggest that the amplitude of the oscillating pressure can be reduced by more than 50% under different working conditions. Moreover, proper orthogonal decomposition and dynamic mode decomposition are used to study the suppression effects on the intensity of flame pulsation. The ability of active control in suppressing flame fluctuations is relatively limited.

Analysis and Suppression Strategy for the Double-Line Frequency Pulsation in Single-Phase Quasi-Z-Source Converter

Devices and the passive components in the single-phase impedance source network converter are sensitive to the double-line-frequency (DLF) pulsation. Previous research works have studied the power decoupling and the DLF equivalent model for the power pulsation suppression method. This paper explored the DLF transfer routes in the impedance source network. A comprehensive stress derivation of the passive components and switching devices are obtained for the suppression method enhancement and optimization. For the DLF passive suppression method, the explanation for the passive component volume issue is provided from the stress aspect. The component value solution space and corresponding design guidance are presented. For the DLF active suppression method (ASM), a buck-type dc-side ASM suppression method is employed and its optimization is demonstrated with the assistant circuit stress analysis. The total capacitor and inductor values get reduced by 77% and 25%, respectively. The corresponding pulsewidth modulation method implementation and the common-mode leakage current demonstration are also presented. The effectiveness of the theoretical analysis and optimization methods is verified by simulations and experiments.

Control model for dampening hand vibrations using information of internal and external coordinates.

In the present study, we investigate a control mechanism that dampens hand vibrations. Here, we propose a control method with two components to suppress hand vibrations. The first is a passive suppression method that lowers the joint stiffness to passively dampen the hand vibrations. The second is an active suppression method that adjusts an equilibrium point based on skyhook control to actively dampen the hand vibrations. In a simulation experiment, we applied these two methods to dampen hand vibrations during the shoulder’s horizontal oscillation. We also conducted a measurement experiment wherein a subject’s shoulder was sinusoidally oscillated by a platform that generated horizontal oscillations. The results of the measurement experiments showed that the jerk of each part of the arm in a task using a cup filled with water was smaller than the shoulder jerk and that in a task with a cup filled with stones was larger than the shoulder jerk. Moreover, the amplitude of the hand trajectory in both horizontal and vertical directions was smaller in a task using a cup filled with water than in a task using a cup filled with stones. The results of the measurement experiments were accurately reproduced by the active suppression method based on skyhook control. These results suggest that humans dampen hand vibrations by controlling the equilibrium point through the information of the external workspace and the internal body state rather than by lowering joint stiffness only by using internal information.

Active Suppression of Low-frequency Interference Currents by Implementation of the High-performance Control System for the Grid-interfaced Converters

Operation of traction drive and auxiliary power supply converters installed onboard modern vehicles causes increased content of line harmonics and interharmonic components in the line current. Passive techniques for filtration of low frequency interference line currents appeared to be insufficient, but are combined with active mitigation techniques. The paper describes and suggests active suppression methods based on proper design of the grid interface of the power converter and its corresponding control system. Interference currents, including those induced by the operation of onboard power converters can significantly influence the correct operation of telecommunication, train control systems and other railway signaling infrastructure along the tracks, having direct impact to the safety of the railway transport. Therefore, suppression of low-frequency interference line currents requires careful implementation of active/passive methods. For purpose of quality evaluation of performances of the grid interface of the traction drive converters and its corresponding control system in particular, a series of tests for assessment of the line current frequency spectrum, resulting from the operation of the converter in typical exploitation conditions, were performed. Tests were performed in laboratory conditions and on the vehicle, with satisfactory results.

An optimization of energy addition to suppress the coalescence of the shock waves

A sonic boom problem has been a major inhibitor in the development of the supersonic/hypersonic vehicles flying over the ground. Pulsed energy addition upstream of a flying object is one of the active suppression methods to eliminate the sonic boom. Pulsed energy addition approach is investigated to suppress the coalescence of the shock waves and weaken the shock strength. To explore the efficiency of the proposed method, a numerical optimization methodology with off-body energy addition upstream of oblique shocks has been conducted in a Mach 2.6 flow. The dynamics of the interactions among the oblique shocks and pulsed wave were analyzed and the results from the near-field region were propagated through the Thomas code down to ground. These results suggest an essential chance to enable sonic boom reduction using an active control based on pulse shock generated by energy addition upstream of supersonic aircraft.

A further investigation into the method for active suppression of reflected sound waves based on the state feedback control.

A further investigation into the method for active suppression of reflected sound waves based on the state feedback control.