PI Control Method Research Articles

Adaptive variable impedance force/position hybrid control for large surface polishing

PurposeThis paper aims to propose a hybrid force/position controller based on the adaptive variable impedance.Design/methodology/approachFirst, the working space is divided into a force control subspace and a position subspace, the force control subspace adopts the position impedance control strategy. At the same time, the contact force model between the robot and the surface is analyzed in this space. Second, based on the traditional position impedance, the model reference adaptive control is introduced to provide an accurate reference position for the impedance controller. Then, the BP neural network is used to adjust the impedance parameters online.FindingsThe experimental results show that compared with the traditional PI control method, the proposed method has a higher flexibility, the dynamic response accommodation time is reduced by 7.688 s and the steady-state error is reduced by 30.531%. The overshoot of the contact force between the end of robot and the workpiece is reduced by 34.325% comparing with the fixed impedance control method.Practical implicationsThe proposed control method compares with a hybrid force/position based on PI control method and a position fixed impedance control method by simulation and experiment.Originality/valueThe adaptive variable impedance control method improves accuracy of force tracking and solves the problem of the large surfaces with robot grinding often over-polished at the protrusion and under-polished at the concave.

Double closed loop PI control with full compensation arc elimination based on zero sequence voltage of neutral point

Aiming at the problem of zero sequence voltage generated by unbalance parameters of line to ground, which affects arc suppression effect of grounding fault of controllable voltage source. By analyzing the influence of ground unbalance parameters on the arc suppression effect of controllable voltage source under different grounding modes, the mechanism of full compensation arc suppression based on zero sequence voltage of neutral point is revealed, and on this basis, a fully compensated arc suppression model of controllable voltage source controlled by double closed loop PI is established, and the deviation control is carried out by using the neutral voltage of distribution network and the voltage of fault phase supply. The residual voltage ring adopts the ground fault phase residual voltage for closed loop control. The simulation results show that the dual-closed-loop PI control algorithm can continuously stabilize the output waveform of the controllable voltage source. When the transition resistance is 0.1 ~ 10 kΩ, the residual voltage stabilization time of the independent controllable voltage source grounding method is 43 ms ~ 2.4 s, and the parallel arc suppression coil grounding method is 43 ms ~ 4.7 s. The proposed dual closed-loop PI control method for neutral point voltage deviation and fault residual voltage can stabilize the residual voltage of the grounded fault phase to below 10 V, forcing reliable arc extinction at the grounded fault point, exhibiting good stability. Low-voltage simulation tests have also proved the feasibility of the algorithm.

Auto-tuning method for PI controllers under Symmetric-Send-on-Delta sampling strategy

In this work, an auto-tuning method for PI controllers applied in a loop under a Symmetric-Send-On-Delta sampling strategy is proposed. Auto-tuning algorithms usually implement an identification phase to obtain some information about the system dynamic that is used for tuning the controller. In our proposal, two frequency response points are estimated through an iterative procedure. With this information, a simple tuning rule is applied which guarantees robustness against limit cycle oscillations that can be induced by the SSOD sampler. Both the robustness measure to limit cycles and the identification procedure are based on the describing function technique, whose validity in the networked control systems under study requires a low incidence of losing packets as well as the transmission delays to be known or negligible compared to the system’s dynamic. Comparatives with other classical tuning rules support the suitability of the proposed method. The auto-tuning procedure has been validated through a simulation study reflecting its applicability for the most common dynamics found in industrial processes.

Power Regulation of a Three-Phase L-Filtered Grid-Connected Inverter Considering Uncertain Grid Impedance Using Robust Control

Uncertain grid impedance is often common in power distribution networks; therefore, it is crucial to design an efficient controller in this situation. An issue that frequently occurs is the problem of unpredictable grid impedance, which can cause voltage fluctuations, power quality problems, and potential damage to equipment. This work provides a systematic control strategy to tackle these issues by supplying well-regulated power from a DC source to an AC power grid. A linear matrix inequality (LMI)-based robust optimal control is proposed in this paper to provide stability to the inverter system without offset error at the output side. The convergence time to steady state is minimized by solving the LMI problem to maximize the eigen value of the closed-loop system with the inclusion of the uncertainty of the filter parameter and grid impedance. Furthermore, the uncertainties in this study include the potential variation of values for the filters and the grid's impedance. These uncertainties occur because the grid impedance can fluctuate fast in the event of a fault or termination of a transmission line, while the filter's impedance can also be affected by changes in operating temperature. The simulation study of this proposed control includes a comparison between wide and narrow uncertainty ranges, as well as a performance comparison under uncertain parameters. Furthermore, this approach exhibits a lower power ripple in comparison to existing PI control method.

Rectification and converter control of the FPSLGs for energy storage applications

AbstractThis article presents two power converters with controllers attached to the Free‐Piston Stirling Linear Generator (FPSLG) and energy storage system (ESS). The rectifier uses hysteresis‐SVPWM current regulation and CB‐SPWM, while the buck‐boost converter utilizes the dual‐loop PI control method. The storage battery receives energy from a linear‐generator with a rectifier and converter. The FPSE and linear motors in the FPSLG convert thermal to electrical energy. A two‐level electrical energy conversion technique using a three‐phase AC signal to DC and DC‐DC converter has been devised to reduce output electrical energy oscillation as well as stabilize the generating system's DC power. Initially, the FPSE's nonlinear model and the three‐phase permanent magnet linear‐motor's linear mathematical model were created and followed by the ESS and control mechanism simulation. The simulation shows that the ESS system and control approach can give stable power to the storage battery using linear‐generator power. The PR controller replaces the PI controller in the position loop to improve frequency and displacement tracing. The control system design was simulated in MATLAB and the topology's feasibility and correctness were confirmed. Comparative analysis shows that, rectifier uses the H‐SVPWM's unity power factor of AC and stability controllability of the DC‐side voltage is better than the CB‐SPWM approach.

Research on a Sensorless ADRC Vector Control Method for a Permanent Magnet Synchronous Motor Based on the Luenberger Observer

A sensorless vector active disturbance rejection control (ADRC) method for permanent magnet synchronous motors (PMSM) utilizing a Luenberger observer is presented. This method aims to address the challenges associated with weak active disturbances, substantial steady-state speed amplitude fluctuations, and difficulty in achieving a balance between overshoot and speed control in the sensorless PMSM control system. Mathematical models of the Luenberger observer and the ADRC were analyzed, leading to the proposal of a second-order ADRC control method based on the Luenberger observer. A mathematical model of the permanent PMSM has been introduced. Additionally, the necessary conditions for the convergence of the Luenberger observer were derived and examined. The allowable range of error feedback gain values was determined, and rotor position data were acquired using a phase-locked loop. The principle of the ADRC was analyzed, and the ADRC simulation results, along with the PI simulation results, were detailed. When the target speed is 1000 r/min, the steady-state error and load disturbance resistance of the ADRC control method outperform those of the PI control method. Finally, the control method was experimentally tested on an STM32F4 chip, demonstrating the advantages of small steady-state error and strong active disturbance ability.

Design of MIMO PI-compensators without exponentially unstable poles

Abstract There is a class of systems that can only be stabilized by unstable compensators. However, for most practical systems suitable for use with linear regulators, this is possible with stable ones. To avoid exponentially unstable results in the design of pole placing PI-compensators it is of crucial importance to consider the position of the transmission zeros. This also has a favourable effect on the disturbance rejection. In multi-input multi-output (MIMO) systems, however, not only the zero position but also the zero direction is of importance. In this paper, a design method for multivariable PI-controllers in the time- and in the frequency-domains is presented which helps to avoid the occurrence of exponentially unstable controllers. A modified design method for multivariable PI-controllers, recently published in this journal, facilitates the procedure.

Research on the Control Method of a Brushless DC Motor Based on Second-Order Active Disturbance Rejection Control

This research addresses the issues of weak anti-disturbance ability, fast response, and incompatibility of overshoot in the control process of brushless DC motors (BLDCs). A six-step commutation control method based on second-order active disturbance rejection control (ADRC) is derived following the analysis of the BLDC model and the mathematical model of ADRC. A control model of the BLDC using both PI and ADRC is constructed. Detailed comparative and quantitative analyses of the simulation results using PI and ADRC are conducted, focusing on the anti-load disturbance capabilities using the integrated square error (ISE), integrated time square error (ITSE), integrated absolute error (IAE), and integrated time absolute error (ITAE). Experimental testing on the STM32F4 controller is also carried out, analyzing four error integral criteria in depth. The results indicate that both the ADRC and PI control modes can track the target signal without overshooting, demonstrating strong anti-load disturbance ability and robustness at varying working speeds. In the BLDC control system, using the ADRC control method can achieve fast and non-overshoot tracking of target signals compared to the PI control method, and ADRC has stronger resistance to load disturbances.

Suppression Strategy of Starting Current Impulse in the Front Stage Rectifier of Electric Vehicle WPT System

The three-phase voltage type Pulse Width Modulation (PWM) rectifier is widely used in the front-end power factor of electric vehicle wireless charging systems due to its simple control structure and easy implementation. The system often adopts a double closed-loop PI control method based on voltage and current, which inevitably leads to a significant starting current surge and poses significant risks to the safe operation of the equipment. On the basis of establishing a mathematical model for PWM rectifiers, this article analyzes in detail the causes of starting over-current and designs a starting strategy with a voltage outer proportional and integral separated active current directly given. Simulation experiments show that this method can reduce the starting over-current of PWM rectifiers and the excessive DC voltage surge towards normal operation during the starting process.

Research on modular multi-level converter control based on passivity theory

All In view of the poor dynamic performance of the conventional PI control method in modular multilevel converter (MMC) systems, an up-to-date control strategy using passive theory is proposed. First, the topology of the system and its mathematical model are presented, then its Euler-Lagrange (EL) model is developed and its passivity is proved. Next, the dq-axis component of the current is chosen as the state variable to derive the passivity-based control (PBC) law and from this, the current passivity controller is designed. Simulation shows that compared with conventional PI control, the PBC in this paper can respond quickly to the change of current or power under different operating conditions, with good harmonic characteristics and better dynamic characteristics.

Genetic algorithm-enhanced linear quadratic control for balancing bicopter system with non-zero set point

Bicopter is an unmanned aerial vehicle (UAV) with the advantage of saving energy consumption. However, the unique two rotors design presents a challenge in designing a controller that achieves good stability, fast settling time, and the ability to overcome oscillations simultaneously. This article proposes a new control method for bicopter that uses a genetic algorithm optimization approach in the linear quadratic (LQ-GA) control method. The GA is used to search for the best weighting matrix parameters, Q and R, in the Linear Quadratic (LQ) control scheme. The proposed control method was tested on a balancing bicopter test platform with an input in the form of difference in pulse width modulation (PWM) signals for both rotors and an output in the form of roll angle. The control system was evaluated based on the stability of the transient response and the generated control signal. The results of the tests showed that the proposed LQ-GA control method has better stability, faster settling time, and smaller overshoot than the existing PI and standard LQ control methods. Therefore, the proposed LQ-GA control method is the most suitable for use in a balancing bicopter system with a non-zero setpoint.

Speed Control of PMSM Based on Fuzzy Active Disturbance Rejection Control under Small Disturbances

Permanent Magnet Synchronous Motors (PMSMs), with their simple design, small size, and high-power factor, are ideally suited for realizing high-power AC drives and are widely used in various industries. In this study, Fuzzy Active Disturbance Rejection Control (Fuzzy-ADRC) is used to control the speed of the PMSM. When a slight external disturbance occurs, this control strategy maintains the suppression characteristics of the self-excited control for the disturbance and enhances its ability to compensate for the disturbance. First, a mathematical model was developed to study the surface mount PMSM. Then, a motor control simulation model was created using PI control, vector control, and other control methods. The verification results indicate that the improved Fuzzy-ADRC system performs well under both internal and external minor disturbances. It exhibits a faster dynamic response and reduced regulation time (0.026 s to 0.017 s) compared to the traditional ADRC system. Furthermore, it shows less overshoot (reduced from 70% to 2.9%) compared to the Sliding Mode Observer (SMO). Taken together, the improved Fuzzy-ADRC system is characterized by small steady-state error, high load capacity, and control accuracy. With the assistance of this control strategy, the system can track speed with high accuracy and possesses stronger anti-interference capability to mitigate load disturbances.

Active Disturbance Rejection Control Method for Marine Permanent-Magnet Propulsion Motor Based on Improved ESO and Nonlinear Switching Function

In the control of marine permanent-magnet propulsion motors, active disturbance rejection control has attracted much attention because it can deal with external load disturbances and uncertainties of motor parameters at the same time. However, the conventional second-order ADRC has the problem of slow disturbance observation speed. To this end, this paper proposes an improved third-order extended state observer using the proportional–integral disturbance update law to improve the tracking performance and anti-external disturbance ability of the motor control system. Then, aiming at the problem that the structure does not effectively use the current information, resulting in large speed fluctuations when the load changes, the measured value of the q-axis current is used as the disturbance feedforward compensation item to further improve the load disturbance suppression ability of the motor. Finally, in order to suppress the influence of the current periodic disturbance caused by unmodeled dynamics on the steady-state accuracy of the motor, a nonlinear switching function with bounded gain and an IIR low-pass filter are designed to suppress the periodic disturbance without affecting the dynamic performance of the system. Combined with the established ship propeller load model, the effectiveness of the method is verified on the motor experimental platform: When suddenly changing 75% of the propeller load, the motor speed decreases by about 20%, and the adjustment time is 0.1 s, which improves the performance by more than 70% compared to PI control and conventional ADRC methods.

Fractional Control of a Class of Underdamped Fractional Systems with Time Delay—Application to a Teleoperated Robot with a Flexible Link

This work addresses the robust control of processes of the form G(s)=K·e−τ·s/(1+T·sλ) with 1<λ≤2. A new method for tuning fractional-order PI and PD controllers is developed. The stability is assessed based on the frequency domain tuning of the regulators to control such delayed fractional-order underdamped processes. In order to analyze the closed-loop stability and robustness, the new concept of Robust High-Frequency Condition is introduced. The analysis based on that demonstrates that each controller has a different region of feasible frequency specifications, and, in all cases, they depend on their fractional integral or derivative actions. Finally, an application example, the position control of a teleoperated manipulator with a flexible link, is presented. Simulations and experiments illustrate that the region of feasible frequency specifications defined at low and high frequencies allows us to obtain robust controllers that fulfill frequency requirements.

Continuous Time Least Square PI Control Method for Quasi-Z Source Inverter

Continuous Time Least Square PI Control Method for Quasi-Z Source Inverter

Pulse Train Control Strategy for Autonomous Three-Phase Voltage Source Inverter in Stationary Reference Frame

Pulse train (PT) control strategy is proposed for autonomous three-phase voltage source inverter (3ph-VSI) in stationary reference frame. Compared with classical control strategies for 3ph-VSI system, the proposed PT control strategy of 3ph-VSI utilizes the combination of two different duty cycles to approximate the desired duty cycles of 3ph-VSI. The load voltage can therefore be regulated. Without error amplifier and its corresponding compensation circuit, the proposed control scheme features fast transient performance and simple operation. The control loop of the proposed control strategy is simple to design. The operation principle and structure of the proposed PT-controlled 3ph-VSI are introduced. Its implementation and control parameter design are presented as well. The effects of the control parameter on the performance of the proposed control method are verified by simulation results. Besides, the fault-tolerance analysis of the circuit parameters of the proposed control scheme is provided. A 1.0-kVA experimental prototype of 3ph-VSI is built to verify the proposed control technique. Experimental results of the proposed control technique are provided to compare with conventional Ziegler Nichols (ZN)-PI control method, which show that the steady-state, load transient and output frequency transient performance of the proposed PT-controlled 3ph-VSI can be maintained over a wide output power range of 0-1000VA.

Design of sensorless permanent magnet synchronous motor controller based on improved sliding mode observer

Because PMSM needs to install a position sensor in practical application, and the buffeting issue in sensorless control stems from an old SMO (sliding mode observer), an improved SMO is proposed. Stemming from the improvement of the switching function and low-pass filter of the traditional SMO, the chattering problem of the conventional SMO is optimized. Considering the reality that the traditional PI control strategy unable to respond accurately and quickly in the case of current coupling, the current complete decoupling integrates the traditional PI control method is adopted. It can speed up system response and improve system performance. The experimental consequence demonstrates that the improved SMO can effectively restrain the chattering phenomenon and realize the fast and precise control of the PMSM.

Second Harmonic Current Suppression and Dynamic Response Improvement for V2G System

Electric vehicles interconnect and interact with the grid bidirectionally through a vehicle-to-grid (V2G) system. In V2G, the output power on the AC side pulsates at twice the grid frequency 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> , which leads to the presence of a second harmonic current (SHC) on the DC side and reduces the reliability of the system. A bandstop filter (BSF) with a center frequency of 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> is introduced in the voltage sampling loop to suppress the SHC. A digital implementation of the BSF is proposed to apply at arbitrary frequencies, which avoids the cost increase and provides high simplicity and flexibility. An adaptive PI control method is further proposed to improve the dynamic performance, which adjusts the PI parameters in real-time according to the inductor current. A 3.5 kW V2G experimental prototype is built and tested to verify the feasibility and stability of the proposed strategies. The prototype offers an excellent dynamic and steady-state response in stand-alone and grid-tie modes.

Automatic Excitation Control Using PI Method Based on Analysis Root Locus for Synchronous Generator

The demand for electrical energy is increasing (at 2–3 percent per year). It is necessary to utilize the energy available in nature optimally and stably to fulfill electricity needs. Synchronous generators have an essential role in fulfilling electricity needs. Maintaining and improving the operational stability of the synchronous generator is fundamental to the safe and economical operation of an electric power system. The use of control methods to increase control excitation is recognized as an economical and effective way. Previous research shows there are still areas for improvement in the excitation control method. Thus, this research focuses on optimizing the automatic excitation system using the PI control method with stability analysis using the root locus. The effect of PI control on the results of the characteristics response has Tr is 1.9 s, Ts is 6.6 s, Mp is 38.95 percent, and Ess is 11.02 percent. While the generator excitation current will increase in line with the increase in load current, and the resulting output voltage will be stable with errors that occur when compared to the nominal voltage is 10.51 percent because the sensor reading is affected by a frequency that is not following the operating frequency.DOI: 10.17977/um024v8i12023p036

PIDD2 Control of Large Wind Turbines’ Pitch Angle

The pitch control system has a profound impact on the development of wind energy, and yet a delay or non-minimum phase can weaken its performance. Thus, there is a strong incentive to enhance pitch control technology in order to counteract the negative effects of unidentified delays and non-minimum phase characteristics. To reduce the complexity of the parameter-tuning process and improve the performance of the system, in this paper, we propose a novel control method for wind turbine pitch angle with time delays. Specifically, the proposed control method is state-space PIDD2, which is based on internal model control (IMC) and the open-loop system step response. Then, considering the tracking, disturbance rejection and measurement noise, the proposed controller is verified through simulations. The simulation results demonstrate that the state-space PIDD2 (SS-PIDD2) can provide a trade-off between robustness, time domain performance and measurement noise attenuation and effectively improve pitch control performance in contrast to series PID and PI control methods.