Three-loop Control System Research Articles

Analysis of the operation of electromagnetic bearings in the difference of the center of the magnetic system relative to the axis of rotation and variations of the supply voltage

The article sets the task of reducing the consumption of electrical energy by electromagnetic bearings. To achieve this goal, it is proposed to shift the center of the magnetic system of bearings that compensate for the weight of the rotor relative to the axis of rotation. The displacement value is assumed to be equal to half the clearance value in the safety bearings of the unit under consideration. A mathematical model of a radial electromagnetic bearing, its design scheme, taking into account the displacement of the center of the magnetic system relative to the axis of rotation, a block diagram of a three-loop control system and formulas for calculating the parameters of regulators are presented. Regulator settings for a specific type of electromagnetic bearings are determined. A calculation model has been developed that makes it possible to study the operation of an electromagnetic bearing when the center of the magnetic system is displaced relative to the axis of rotation and the supply voltage is varied. The results of simulation in the Matlab Simulink software environment of the process of rotor ascent from safety bearings and rotor levitation in a displaced state at different values of the supply voltage are given. It is shown that the voltage reduction by 16.7% ensures stable operation of the electromagnetic suspension of the rotor in all possible modes. Therefore, shifting the center of the magnetic system can reduce the power consumption of electromagnetic bearings by 30%.

Sliding mode‐based velocity and torque controllers for permanent magnet synchronous motor drives system

To minimise the torque ripple for vector control of interior permanent magnet synchronous motor (IPMSM) of railway traction system, this study proposes a new velocity, torque and current three-loop control system, and designs a velocity and torque sliding mode controller (SMC) for permanent magnet synchronous motor (PMSM) driven system. First, the mathematical model of IPMSM is described and the new velocity and torque closed-loop control system for PMSM is designed. Second, the velocity SMC and torque SMC are designed. The fast convergence of the motor velocity and torque is realised, and the torque ripple is reduced effectively. The stability of the designed SMC is analysed. Finally, the effectiveness of the proposed scheme was compared with PI by simulations and experiments. The results show that the proposed method has good control performance and strong robustness.

A control system of an electromagnetic bearing

A three-loop control system for the radial electromagnetic bearing of powerful rotating machines is proposed, the working clearances in which between the stator and rotor amount to tenths of a millimeter with a rotor weight of about 1 t. In the open state, the system is unstable and has features that need to be taken into account when creating the controllers. The control system is designed in accordance with general principles typical for the systems of subordinate regulation. The problems of design of the pulse-control system and various variants of constructing the internal current loop were considered. For calculating the parameters of controllers, the method of transfer functions and z-transformation method were used. At the initial stage, the internal current loop was investigated and it was revealed that the construction of the current loop of an electromagnetic bearing with a relay controller operating in a sliding mode is the most appropriate. In accordance with the mathematical model of an electromagnetic bearing and corresponding structural diagrams, simulation models were designed in the MATLAB/Simulink software package. As a result of simulating the pulsed control system of an electromagnetic bearing, oscillograms of transient processes under control and disturbance effects were obtained. Analysis of transient processes during simulation revealed that electromagnetic bearings equipped with a three-loop control system have a high static rigidity and high operating speed. The obtained results were used in constructing a control system using the electromagnetic bearing of the gas pressurizer at the Pomarskaya compressor station.

Small-Signal Modeling of <italic>I</italic><sup>2</sup> Average Current Mode Control

I 2 average current mode control is a promising control technique featuring fast dynamic response, cycle-by-cycle current limiting and accurate current control. It can be treated as peak current mode control with no peak-to-average error. By combining direct current feedback and average current feedback, I 2 average current mode control is a three-loop control system. Since it is a new control technique proposed in 2013, few papers exist which discuss the small-signal model for this control method. In this paper, a small-signal model for constant frequency I 2 average current mode control is proposed which successfully predicts the subharmonics oscillation when the duty cycle is close to or greater than 0.5. The characteristics of I 2 average current mode control are also compared with average current mode control and peak current mode control to show its advantages.

Design of Rate Gyro Stabilized Platform Control System

Seeker plays an extremely important role in precision-guided weapons, among which the high tracking precision ability of servo system is one of the key technology. This paper studies the three-loop control system applied in the rate gyro stabilized platform of an infrared seeker and researches the stability, rapidity and accuracy of speed loop ,current loop and position loop. Finally, according to the engineering project, we can verify the validity and applicability of this triple loop system.

A Novel Control Strategy for Input-Parallel-Output-Series Inverter System

This paper presents a topology structure and control method for an input-parallel-output-series(IPOS) inverter system which is suitable for high input current, high output voltage, and high power applications. In order to ensure the normal operation of the IPOS inverter system, the control method should achieve input current sharing(ICS) and output voltage sharing(OVS) among constituent modules. Through the analysis in this paper, ICS is automatically achieved as long as OVS is controlled. The IPOS inverter system is controlled by a three-loop control system which is composed of an outer common-output voltage loop, inner current loops and voltage sharing loops. Simulation results show that this control strategy can achieve low total harmonic distortion(THD) in the system output voltage, fast dynamic response, and good output voltage sharing performance.

A three-loop model-following control structure: theory and implementation

This article presents a novel three-loop control system, which supplements control structures known from the literature as model following control (MFC). The major advantage of the proposed system is its high robustness to process parameter variations; it is much higher than that offered by single-loop or two-loop control systems. Features of the new structure are revealed by a theoretical analysis that has been carried out from the viewpoint of requirements for a force/pose controller of a Stäubli RX60 manipulator. This article shows how the proposed control structure responds to such strong process parameter variations and makes a comparison to results yielded by single-loop control structures.

A MULTIPLE-LOOP SLIDING MODE CONTROL SYSTEM WITH SECOND-ORDER BOUNDARY LAYER DYNAMICS

Presented is a method of continuous sliding mode control design to provide for the second-order sliding mode on the selected sliding surfaces in a three-loop control system, where two outer-loop virtual control signals must be smooth enough to be tracked in the inner loops. The control law in the vicinity of the sliding surface is a nonlinear dynamic feedback that in absence of unknown disturbances provides for finite-time convergence of the second-order reaching phase dynamics. The controller with a second-order disturbance observer in a combination with the proposed continuous dynamic feedback attracts the system trajectories to boundary layers around two sliding surfaces of the outer control loops with the second-order sliding accuracy in presence of unknown disturbances and the discrete-time control update.

Three-loop feedback control of fault-tolerant power supplies in IBM Enterprise System/9000 processors

In an Enterprise System/9000™ (ES/9000™) processor, a fault-tolerant power system composed of multiple power supplies connected in parallel provides thousands of amperes of current to low-voltage (1–2 V) logic circuit boards, monitors the voltage at each board, and immediately responds to compensate for failure of a supply. If a supply fails, the very fast closed-loop response redistributes the current uniformity among the remaining supplies and allows the normal functioning of the processor logic to continue uninterrupted. This rapid response is not obtained from a conventional two-loop (current-mode) feedback power supply because the loop bandwidth is restricted by a resonance that develops in the power distribution. A third feedback loop that is added to each supply controls this power distribution resonance and makes possible the wide loop bandwidth necessary to achieve the required power system control. Analysis is presented of a three-loop control system, and a simulation of its application to a typical ES/9000 power system is described.