Python app for drawing Bode diagram asymptotes of transfer function for minimum and non-minimal phase systems

The purpose of this article is to introduce an application to draw the asymptotes of Bode diagram module and phase from each constituent elementary factors of any transfer function for minimum and non-minimal phase systems without transport delay. The Bode diagram is the most used tool in the frequency response method. Python was used to program the application to perform the operations as well as the Qt5 Design for the simple graphical interface for the application and all this in the Linux operating system. The application purpose is to assist students in learning the concept and drawing of Bode diagram. For students the non-minimum phase system Bode diagram is more difficult to draw than a minimum phase system due to the presence of zeros and/or poles on right half of s-plane. The phase asymptotes of a quadratic factor was closest to the real phase curve around the corresponding undamped natural frequency and this can be observed in the example showed in this article. This example must be used as a help and not a simply to solve a problem.

Differential electrochemical impedance spectroscopy of the polymer proton electrolytes

A method of deriving standard electrochemical impedance spectroscopy (EIS) data such as Bode diagram, Nyquist diagram, and others from frequency dependence of the external impedance using numerical differentiation of the indicated dependence in quadratic coordinates is proposed, the method being named as the differential electrochemical impedance spectroscopy (DEIS). The method was tested experimentally on polyvinyl alcohol-based proton membranes doped with sulphated montmorillonite in granulated or dispersed states as an example. It is shown that DEIS data can be easier and with higher accuracy described by regular semicircles while leaving intact values of ohmic resistance. Very high values of dielectric permeability were obtained in the work enabling to develop condensers with high capacity based on highly conductive polymeric proton electrolytes.

Interference Pattern Representation on the Complex s-Plane

In this work, the normalized interference pattern produced by a coherence interferometer system was represented as a complex function. The Laplace transform was applied for the transformation. Poles and zeros were determined from this complex function, and then, its pole-zero map and its Bode diagram were proposed. Both graphical representations were implemented numerically. From our numerical results, pole location and zero location depend on the optical path difference (OPD), while the Bode diagram gives us information about the OPD parameter. Based on the results obtained from the graphical representations, the coherence interferometer systems, the low-coherence interferometer systems, the interferometric sensing systems, and the fiber optic sensors can be analyze on the complex s-plane.

Design and Analysis of a Swashplate Control System for an Asymmetric Axial Piston Pump

Based on the previously developed fixed-displacement asymmetric axial piston pump, a variable displacement asymmetric axial piston pump (VDAAPP) with three independent suction/delivery ports is proposed. A basic linear model of VDAAPP is established to get open-loop bode diagram. Based on open-loop Bode diagram features and design requirements, P-controller is determined for VDAAPP. Then VDAAPP's performance is investigated by advanced modeling environment for performing simulations of engineering systems (AMESim) and automatic dynamic analysis of mechanical systems (ADAMS) joint simulation, and some key design parameters are obtained. Next, a VDAAPP prototype with a maximum displacement of 40 cc/rev is designed and manufactured, ratio of flow rates at ports A, B and T is 1:0.6:0.4. Due to hard limitations of the test bench, the performance only under the conditions of the opposite passive loads is tested. Preliminary test results indicate that VDAAPP prototype works normally and meets the design requirements for flow ratio, and the maximum rise time of the test pressure is about 0.32 s. However, due to special design of VDAAPP valve plate, the swash plate torque severely limits system dynamic response. Therefore, an improved swashplate control system based on asymmetric-valve-controlled asymmetric-piston scheme is presented as well, it is found to be an effective way to suppress the negative impact of swash plate torque on system dynamic performance. This provides a direction for the optimization of the swashplate control system for asymmetric axial piston pumps in the future.

Stability analysis for a rotor system in a magnetically suspended control and sensitive gyroscope with the Lorentz force magnetic bearing rotation

In order to intuitively and conveniently analyse the stability of a rotor system in a magnetically suspended control and sensitive gyroscope with the rotation of a Lorentz force magnetic bearing, this study proposes a stability analysis method on the basis of a pseudo-linear equivalent transformation and extended double-frequency Bode diagram. The working principle of the rotor system is presented, and the dynamic model for this system that considers the Lorentz force magnetic bearing rotation is established. The established real-coefficient two-input–two-output nonlinear system is transferred into a complex-coefficient single-input–single-output nonlinear system through variable reconstruction. Based on the complex frequency shift characteristics of Laplace transformation, the time-varying nonlinear system is converted into a pseudo-linear system. In accordance with the relationship between a Nyquist curve and a Bode diagram, the extended double-frequency Bode diagram method is proposed to analyse the stability of a non-minimum phase system with integral items. Simulation and experimental results demonstrate the correctness of the proposed analysis method.

Harmonic Coupling Analysis and Suppression Strategy of Grid-connected Photovoltaic Inverter

For the complex harmonic coupling problem caused by the parallel connection of grid-connected photovoltaic inverters to the grid, the mathematical models of a single three-phase inverter and two three-phase inverters connected in parallel are established in this paper. The transfer function is derived and the resonant characteristics of grid-connected single inverter and parallel grid-connected multi-inverters are analyzed by using Bode diagram. On the basis of the maximum power tracking link, This paper proposes a control strategy which combines the double closed-loop of current by using grid-connected voltage and capacitive current with the proportional feedforward compensation of grid voltage, which maximizes the use of solar energy and has a better harmonic resonance suppression capability at the same time. The effectiveness and correctness of the proposed control strategy are verified by Matlab/Simulink system simulation.

Modelling and experimental studies on a proportional valve using an innovative dynamic flow-rate measurement in fluid power systems

A numerical model of a servoactuator and of a four-port proportional direction control valve has been developed. Mechanical and hydraulic elements have been simulated in the LMS Amesim® environment. The complete model has been validated on the basis of the experimental time histories of the actuator velocity and of the flow-rate controlled by the proportional valve. The validation data have been acquired on a fluid power system used to test electro-hydraulic servovalves according to ISO 10770-1 standard. The measurement of the instantaneous flow-rate through the valve has been performed with an innovative high-dynamics flowmeter, recently developed for high-pressure liquid flows. Furthermore, the model predicted static characteristic of the proportional valve has been compared with a corresponding experimentally derived curve and an analysis of the cause-and-effect relationships has been carried out for the valve static performance. Measured data on valve leakages have also been presented in order to complete the steady-state characterization of the tested valve. The developed model of the hydraulic system has been then applied to realize the Bode diagram of the proportional valve, which is expressed in terms of instantaneous flow-rate as a function of the sinusoidal driving command, as well as the Bode diagram of the subsystem made up of the proportional valve and of the linear actuator. The latter Bode graph is plotted in terms of piston velocity as a function of the sinusoidal driving command provided to the valve. The comparison between the two Bode diagrams has confirmed the accuracy of the ISO procedure, which is based on the assumption of negligible delay introduced by the dynamic response of the servo-actuator and by the oil compressibility. A reliable and cost-saving methodology, which uses the innovative flowmeter instead of the low inertia servo-actuator, is proposed as an alternative to the ISO standard for testing the dynamic response of proportional valves.