High Steady-state Accuracy Research Articles

State Transformation Combined Adaptive Robust Control for Motor Driven Joint with State Constraints and Input Saturation

The control problem of the motor driven joint system under the state and input constraints is discussed in this paper. Firstly, a state transform function is introduced to transfer the state-constrained motor driven joint system to a transformed system, which no longer has the state constraints. Secondly, an adaptive robust control (ARC) with the specified performance bounds is proposed for this transformed system, where the ARC algorithm combined with an auxiliary variable are used to ensure the semi-globally uniformly ultimately bounded of all the closed-loop signals, and a time-varying barrier Lyapunov function (BLF) is designed to constrain all the tracking errors within the specified performance bounds. Thirdly, the above results are extended to the motor driven joint system. Namely, the boundedness of the states in the transformed system are converted into the satisfaction of the state constraints in the motor driven joint system, and the fast transient response and high steady-state tracking accuracy can be achieved by designing the appropriate specified performance bounds in the time-varying BLF. Finally, a simulation is carried out, and the results demonstrate the effectiveness of the proposed method.

The Dual-Core Sliding Mode Control Technology of Permanent Magnet Synchronous

Based on the structure and working principle of permanent magnet synchronous motor, a mathematical model suitable for engineering practice is established. For the system chattering problem caused by sliding mode control, a variable gain sliding mode controller is proposed to suppress chattering. Based on the MTLAB simulation platform, the permanent magnet synchronous motor servo control system model is designed and verified by simulation to verify the static and dynamic performance of the system. An experimental platform with DSP and FPGA as the core is built, and a new sliding mode control algorithm with DSP and FPGA as the core is verified. To verify the feasibility of the control strategy described in this article, the load experiment was carried out on the platform. Simulation and experimental results shown that the permanent magnet synchronous motor servo system based on dual-core sliding mode control technology has high response speed, high steady-state accuracy and robustness, and has good static and dynamic performance.

H∞ Optimal Control Design of Static Var Compensator Coupling Hybrid Active Power Filter Based on Harmonic State-Space Modeling

Compared with the conventional active power filter (APF), the static var compensator coupling hybrid active power filter (SVC-HAPF) has distinct characteristics of low DC-link operating voltage, which can lower the system and operational costs. It also has a wider operational range than the conventional hybrid active power filter (HAPF). In this paper, a harmonic state-space (HSS) modeling is firstly proposed to address the nonlinearity issue of the SVC-HAPF. The HSS based SVC-HAPF model is linear time-invariant (LTI), which enables the optimal control techniques. Then, the linear matrix inequality (LMI) based H ∞ optimal control design is proposed, which finds the optimal controller parameters via convex optimization algorithm. The proposed controller for the SVC-HAPF achieves high steady-state accuracy, fast transient response, and fixed switching frequency simultaneously. Finally, simulation and experimental results are also provided to verify the effectiveness and performance of the optimal controller for the SVC-HAPF in comparison with the recent developed state-of-the-art multi-quasi-proportional-resonant (MQPR) controller, which shows superior control performances.

Improved Vsg Control Strategy Based on the Combined Power Generation System with Hydrogen Fuel Cells and Super Capacitors

Hydrogen fuel cells (HFCs) occupy a dominant position in the development of renewable energy due to their environmental protection and high power generation efficiency. The control technology of their connection to the microgrid has become a research hotspot. However, the lack of power cannot be compensated immediately by HFCs when they encounter peak demand or transient events. In order to overcome this shortcoming, supercapacitors (SCs) are introduced as auxiliary power sources. The virtual synchronous generator (VSG) control strategy based on this combined power generation system is proposed to introduce virtual inertia to alleviate the impact of load disturbance on the microgrid in this paper. Through the small signal model, the influence of the control strategy parameters of VSG based on the HFCs and SCs combined power generation system on the system stability is studied. In addition, the parameters of the combined system are designed. In the VSG controller, the voltage and current double closed-loop is improved to suppress the negative sequence component in the output voltage under unbalanced conditions, thereby reducing the unbalance of the output voltage. Finally, simulation results in MATLAB/Simulink environment verify that dynamic changes of the load can be quickly tracked by the proposed control strategy and sufficient power is provided. Compared with the droop control, the rate of the change of frequency and voltage is greatly reduced. This could be explained by the virtual inertia of frequency and voltage responses. At the same time, the three-phase voltage of the microgrid under the improved VSG control strategy in different operating conditions can maintain balanced outputs. Compared with the traditional VSG control, it has better dynamic characteristics of the output voltage and higher steady-state accuracy.

Implementation of Algorithm on MPPT

Solar energy is a potential energy source in India. A photovoltaic is a efficient way to cure the energy in a huge amount and keep to gather that kind of energy for future, and the PV must have good efficiency. The maximum power point tracking (MPPT) is a process that tracks one maximum power point from array input, in which the ratio varies between the voltage and current delivered to get the most power it can. Several algorithms have been developed for extracting maximum power. To increase its efficiency many MPPT techniques are used. Incremental conductance is one of the important techniques in this system and because of its higher steady-state accuracy and environmental adaptability it is a widely implemented tracked control strategy. This research was aimed to explore the performance of a maximum power point tracking system that implements the Incremental Conductance (IC) method. The IC algorithm was designed to control the duty cycle of the Buck-Boost converter and to ensure the MPPT work at its maximum efficiency. From the simulation, the IC method shows better performance and also has a lower oscillation.

Low-Latency, Three-Phase PMU Algorithms: Review and Performance Comparison

Phasor Measurement Units are the most advanced instruments for power network monitoring, since they allow phasors, frequency and rate of change of frequency (ROCOF) to be measured in predetermined time instants with respect to an absolute time reference. The employed estimation algorithm plays a key role in overall performance under off-nominal conditions; the challenge to be faced is combining high steady-state accuracy with fast responsiveness in dynamic conditions, small reporting latency and reduced computational burden. Under regular operation, AC power networks are weakly unbalanced three-phase systems. Based on this consideration, the recent literature has proposed native three-phase estimation algorithms that effectively exploit this property to accurately identify the positive sequence synchrophasor, frequency and ROCOF. In this respect, the present paper describes three among the most promising three-phase algorithms based on the Space Vector transformation. By means of numerical simulations, it compares the achieved performance in terms of response time and estimation error both under steady-state and dynamic conditions. All the considered approaches enable a flexible design that allows balancing accuracy and responsiveness. For this analysis, the reporting latency has been limited to about one and half nominal cycles, i.e., 30 ms at 50 Hz; the P-class algorithm suggested by IEC/IEEE Std 60255-118-1 has also been included as comparison benchmark.

Fast and Accurate Motion Tracking of a Linear Motor System Under Kinematic and Dynamic Constraints: An Integrated Planning and Control Approach

Achieving a fast transient response and high steady-state tracking accuracy simultaneously has been a challenging issue for the linear motor system in the presence of kinematic and dynamic constraints, various parametric uncertainties, and uncertain nonlinearities. To this end, a two-loop control structure is developed to maximize the converging speed of the transient response and achieve high steady-state accuracy. Specifically, in the outer loop, an online trajectory replanning algorithm is devised to force the replanned trajectory to merge into the desired trajectory in minimum time under the system’s kinematic and dynamic constraints. In the inner loop, an adaptive robust controller is synthesized to handle the parametric uncertainties and uncertain nonlinearities effectively so that high steady-state tracking accuracy is guaranteed. Particularly, the interaction between the two loops is intuitive since a feedforward term is optimized in the outer loop and then fed into the inner loop to make the model compensation. Comparative experiments are carried out on a linear-motor-driven system. Experimental results confirm that the proposed control structure can achieve a minimum-time transient response without violating the kinematic and dynamic constraints and also guarantee the excellent steady-state tracking accuracy.

An Improved Specific Harmonic Detection Method Based on Adaptive Cancellation Principle

When the active power filter (APF) and the tunable filter are used for specific harmonic suppression, the accurate single harmonic current detection module is one of the key links to ensure its harmonic suppression effect. An improved single harmonic detection method based on the principle of adaptive cancellation has been proposed, which does not have some of the problems of traditional algorithms, for instance the feedback error is not accurate enough, and the contradiction between tracking speed and steady-state accuracy. This method can accurately and quickly detect the harmonic amplitude and phase angle, and can be flexibly applied to the harmonic detection of three-phase and single-phase systems. Through theoretical analysis and MATLAB simulation, it is proved that the method can guarantee a higher steady-state accuracy and a faster tracking speed.

Adaptive Repetitive Learning Control of PMSM Servo Systems with Bounded Nonparametric Uncertainties: Theory and Experiments

In this article, an adaptive repetitive learning control (ARLC) scheme is proposed for permanent magnet synchronous motor (PMSM) servo systems with bounded nonparametric uncertainties, which are divided into two separated parts. The periodically nonparametric part is involved in an unknown desired control input, and a fully saturated repetitive learning law with a continuous switching function is developed to ensure that the estimate of the unknown desired control input is continuous and confined with a prespecified region. The nonperiodically nonparametric part is transformed into the parametric form and compensated by designing the adaptive updating laws, such that a prior knowledge on the bounds of uncertainties is not required in the controller design. With the proposed ARLC scheme, a high steady-state tracking accuracy is guaranteed, and comparative experiments are provided to demonstrate the effectiveness and superiority of the proposed method.

A New Three-Motor Drive System Using Fuzzy Active Disturbance Rejection Control

Three-motor synchronous drive system is a multi-input multi-output, nonlinear and strongly coupled system, which is widely used in the driving field of high precision coordinated control such as paper-making, printing, electric locomotive, etc. A mathematical model of three-motor drive system is analyzed and a new control strategy is proposed for the decoupling control of speed and tension of three-motor drive system, in which the core is fuzzy first-order active disturbance rejection controller (ADRC). Various disturbances from the outside and the inner model are observed and compensated by an extended state observer. As the parameters of the active disturbance rejection controller are adjusted online by a fuzzy controller, the performance of the controller is thus effectively improved. The anti-interference performance, decoupling performance and tracking characteristics were tested based on laboratory-developed multi-motor experimental platform. The experimental results demonstrate that the proposed strategy can effectively decouple speed and tension. The system has fast dynamic response, low overshoot, high steady-state accuracy and good tracking performance.

Research on Modeling of a Micro Variable-Pitch Turboprop Engine Based on Rig Test Data

Exact component characteristics are required for establishing an accurate component level aeroengine model. When component characteristics is lacking, the dynamic coefficient method based on test data, is suitable for establishing a single-input and single-output aeroengine model. When it is applied to build multiple-input, multiple-output aeroengine models, some parameters are assumed to be unchanged, which causes large error. An improved modeling method based on rig data is proposed to establish a double-input, double-output model for a micro variable-pitch turboprop engine. The input variables are fuel flow and pitch angle, and the output variables are rotational speeds of the core engine and the propeller. First, in order to gather modeling data, a test bench is designed and rig tests are carried out. Then, two conclusions are obtained by analyzing the rig data, based on which, the power turbine output is taken as the function of the core speed and the propeller speed. The established model has the property that the input variables can vary arbitrarily within the defined domain, without any restriction to the output variables. Simulation results showed that the model has a high dynamic and steady-state accuracy. The maximum error was less than 8%. The real-time performance was greatly improved, compared to the component level model.

A Control Strategy for Two-stage PV Grid-connected Inverter Based on Voltage Oriented Control

For the design of three-phase two-stage grid-connected PV inverter, the topology and control strategy of two-stage grid-connected inverter are analyzed. For the DC/DC converter control strategy, the shortcoming of conventional perturbation and observation method are analyzed, which is difficult to obtain high response speed and steady-state tracking accuracy due to its fixed disturbance step size. A duty cycle self-optimizing MPPT method is adopted and effectively alleviates the contradiction between tracking speed and accuracy. For the DC/AC converter control strategy, the grid voltage oriented vector control is adopted based on the analysis of the mathematical model of rotating coordinate. The current decoupling and grid voltage feedforward control in dq coordinate system are carried out. The control system parameters are designed and verified to be feasible.

Phase-Locked Loop Combined With Chained Trigger Mode Used for Impedance Matching in Wireless High Power Transfer

In a wireless power transfer system (WPTS), the control technique of the active rectifier is vital for improving the transfer efficiency of the resonant network, expanding the operating range of the load, and increasing the power density. An indispensable component of such control technique is the accurate and reliable phase-locked method for the resonant current. However, the traditional phase-locked method based on the DSP controller tends to lose driver pulses, which might cause damage to the safe operation of the WPTS. This article illustrates the essential reason why the driver pulses lose and proposes a phase-locked loop combined with the chained trigger mode (PLL-CTM) that can lock the phase of the resonant current accurately and produce the driver pulses reliably. With the proposed PLL-CTM applied, the reliability of the WPTS can be enhanced tremendously. Furthermore, based on the PLL-CTM, this article also presents a double-side phase shift control (DPSC) strategy to achieve constant-current constant-voltage charging and minimize the power loss of the resonant network simultaneously. Finally, a 500-W WPT prototype is built to verify the feasibility of the DPSC with PLL-CTM. Benefiting from the DPSC with PLL-CTM, the WPTS not only obtains a high accuracy in steady state, but also achieves a good dynamic performance with the step change of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> and R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Eref</sub> .

Passive force control of multimodal astronaut training robot

For the purpose of solving the problem of astronaut training in weightlessness environment, this article proposes a multimodal astronaut training robot to enable astronauts to perform running, bench press and deep squat training in the weightless environment, so as to help them mitigate the adverse effects brought by the space adaptation syndrome. Taking the modularized wire driving unit as the research object, the dynamic model of the passive force servo system was established; and the passive force control strategy was designed. The experimental results show that the system is of good stability, high steady-state accuracy, and excellent dynamic quality after correction. When the given signal frequency is 10 Hz, the system phase lag is about 9°, and the loading error is about 5%. The passive force servo control strategy can effectively reduce the surplus force. When the speed disturbance frequency of carrying unit is within 3 Hz, the elimination rate of the surplus force can reach 90%.

An Integrated Dual Voltage Loop Control for Capacitance Reduction in CHB-Based Regenerative Motor Drive Systems

The inherent second-harmonic ripple power in a cascaded H-bridge (CHB)-based motor drive system poses the demand of large capacitors in the dc link of each cell. In this paper, an active power decoupling method based on negative sequence current injection and its corresponding dual voltage closed-loop control are proposed to solve this problem without adding any extra components. The proposed dual voltage closed-loop control system consists of a conventional active power control loop and a frequency-adaptive ripple power control loop. The ripple power control loop aims at injecting a set of negative sequence decoupling currents into the front ends of the cells to remove the ripple powers with variable frequency. Higher steady-state accuracy and robustness are, therefore, achieved compared to the open-loop control. Moreover, to simplify the control system, the ripple power control loop can be integrated into the active power control loop without introducing a harmonic reference frame transformation. By adopting the proposed control, the dc capacitance can be reduced to less than 10% of the conventional case. The effectiveness and practicability of this method are verified by simulation and experimental results.

A Comparative Experimental Analysis of PMSM between Deadbeat Prediction Current Control and Field-oriented Control

Traditional field-oriented control (FOC) exists two disadvantages: 1) the PI parameters are difficult to set, 2) the current dynamic response is slow. Compared with FOC, deadbeat predictive current control (DPCC) will result in better dynamic performance and debugging. This paper intends to compare the advantages and disadvantages of DPCC against FOC with simulation and experiment. Two approaches are newly used in the simulation to compare the current-tracking performance, and then the algorithms of DPCC and FOC are experimentally verified based on a 2.6kW permanent magnet synchronous motor (PMSM) control platform. The simulation and experiment results demonstrate that DPCC is suitable for occasions where the PMSM of electric vehicles (EVs) require high dynamic performance, while FOC is more suitable for occasions with high steady-state accuracy.

A comprehensive multimodality heart motion prediction algorithm for robotic-assisted beating heart surgery.

An essential requirement for performing robotic-assisted surgery on a freely beating heart is a prediction algorithm that can estimate the future heart trajectory. Heart motion, respiratory volume (RV) and electrocardiogram (ECG) signal were measured from two dogs during thoracotomy surgery. A comprehensive multimodality prediction algorithm was developed based on the multivariate autoregressive model to incorporate the heart trajectory and cardiorespiratory data with multiple inherent measurement rates explicitly. Experimental results indicated strong relationships between the dominant frequencies of heart motion with RV and ECG. The prediction algorithm revealed a high steady state accuracy, with the root mean square (RMS) errors in the range of 82 to 162μm for a 300-second interval, less than half of that of the best competitor. The proposed multimodality prediction algorithm is promising for practical use in robotic assisted beating heart surgery, considering its capability of providing highly accurate predictions in long horizons.

DESIGN AND IMPLEMENTATION OF HIGH POWER DENSITY MOTOR DRIVE

Based on the demand of low-voltage, small-size and high-current motor drive in the vehicle-mounted servo system, the low-voltage and high power density motor drive, which used TMS320F2812 of TI as the control unit, Incremental encoder and small-value, high-power sensor resistor as motor speed and current acquisition unit, low-voltage and high power density MOSFET as driving unit, was designed and implemented. The hardware of driving system was introduced in details, and then the designs of high-density PCB, structure and technology, with relevant speed control of nested segment and parameters testing procedures, were employed to improve the driver integration and reliability. A DC servo motor with a rated current of 20 amps is used as a test motor. The experimental results indicate that the driving system has the advantages of high steady-state accuracy and stable load response.

A novel dual closed-loop control scheme based on repetitive control for grid-connected inverters with an LCL filter

Grid-connected inverters with LCL filters need high steady-state control accuracy, fast dynamic response performance, and strong robustness to guarantee the power quality. However, there are many problems in traditional control strategies that restrict improvements to control system performance, such as poor dynamic performance of traditional single-repetitive control, large ripples, low steady-state accuracy of inverter current feedback based repetitive dual-loop control or grid-current feedback based single-loop proportional-integral control. In this paper, a novel dual closed-loop repetitive control strategy based on grid current feedback is proposed for single-phase grid-connected inverters with LCL filters. The proportional-integral inner loop is stabilized by using an inherent one-beat delay achieved by digital controller. Based on the inner loop system, a detailed design scheme of a repetitive controller is presented, through which direct control of the grid current is realized, the reference is tracked perfectly to a zero phase shift, and high-attenuation gain is achieved in the high frequency range. In particular, the gird-voltage feed forward control and current reference feedforward control are adopted to suppress grid-voltage disturbance and increase dynamic tracking performance. Finally, the simulation and experimental results show that the proposed method has the advantages of high steady-state accuracy, fast dynamic response, and anti-disturbance ability.

Coordinated Standoff Target Tracking Guidance Method for UAVs

We need a coordinated control method to continuously track a moving target using a group of UAVs. In this paper, we study the predicted reference point guidance method, where the target is considered to move with a constant velocity in a very short time window and the trajectories of the UAVs are designed as several tiny arcs around the target. The control law of the UAV is divided into roll angle control and velocity control. Simulations are used to verify that the proposed control laws have smaller standoff distances and phase angle control errors than the Lyapunov vector field guidance and model-based predictive control, and the wind is considered in the simulation, too. Therefore, we show that our proposed method has higher steady state accuracy among existing techniques.