Kolmogorov-Chaitin Complexity of Digital Controller Implementations

The complexity of linear, fixed-point arithmetic digital controllers is investigated from a Kolmogorov-Chaitin perspective. Based on the idea of Kolmogorov-Chaitin complexity, practical measures of complexity are developed for statespace realizations, parallel and cascade realizations, and for a newly proposed generalized implicit state-space realization. The complexity of solutions to a restricted complexity controller benchmark problem is investigated using this measure. The results show that from a Kolmogorov-Chaitin viewpoint, higher-order controllers with a shorter word-length may have lower complexity and better performance, than lower-order controllers with longer word-length.

Solar Energy System with Digital Controller for Grid Connected Systems

The solar photovoltaic （PV） module output voltage changes according to the variation of light intensity and temperature. This paper presents the implementation of an automatic digital controller of a DC-DC boost converter without batteries for a solar cell module by using a peripheral interface controller, which forms a closed loop, to control the ON-OFF period of the switching pulse. The output of DC-DC converter is maintained by automatically increasing or decreasing the pulse width. To produce the pulse width modulation （PWM）, the microcontroller is programmed according to the required duty cycle for the power switch. The PWM ON period is increased with the decrease in the PV voltage and vice-versa. The input voltage to the inverter is maintained constantly and is converted into an AC signal by using the metal-oxide-semiconductor field effect transistor （MOSFET） H-bridge operated in the sinusoidal pulse width modulation mode by using a PIC （peripheral interface controller） microcontroller. The generated AC signal can be connected to the AC grid or to the AC load. The simulated results by using Proteus 8 and hardware implemented results verify the effectiveness of the proposed controller.

Real Time Implementation of Series Expansion Based Digital Controller for Magnetic Levitation System

This paper addresses a digital controller for a real time magnetic levitation system using series expansion of pulse transfer function, which achieves desired closed loop response. The proposed digital controller designed, based on series expansion of pulse transfer function by solving a linear equation using the method of least squares, which improves the transient performance and step tracking capability of the compensated system. The designed algorithm used for the control input is not iterative, so the calculation is very fast. The proposed control scheme has successfully applied on maglev system and also validated through the simulation and hardware experimental results.

Comparative Analysis of Analog and Digital Controllers for Negative Output Superlift Luo Converter (NOSLC)

This paper focuses on the comparative study of analog and digital control techniques for Negative Output Superlift Luo converter (NOSLC). NOSLC is a high gain converter in which the positive source voltage is converted into a negative load voltage. Though the negative load voltage is produced effectively, there is lot of non-linearities that affects the voltage level. To overcome this, analog controllers like Proportional-integral (PI), fuzzy PI and a sliding mode controller (SMC) were proposed for NOSLC. However PI controller does not respond to changes in operating point, fuzzy PI is based on the systematic approach and proved to be a trial and error oriented method and SMC brings an oscillation in the duty cycle. Therefore, to overcome these drawbacks, a digital control technique using PIC microcontroller is proposed in this paper which provides high versatility and programmability approach. Simulation studies are carried out in MATLAB and the performances of these controllers have been investigated for the proposed DC-DC converter. A prototype of the NOSLC converter is built by employing digital control and the results are verified experimentally.

Design of digital controller for HEPS corrector power supply

Purpose In order to realize the control of current closed loop in HEPS corrector power supply,a digital control board is designed.Methods The control board uses the latest FPGA to realize digital processing and uses two different AD chips to realize current and voltage sampling,respectively.In order to achieve high-precision closed-loop control,an effective closed-loop control program is designed.Results The controller has been widely used in HEPS projects,and its control effect has been proved.Conclusions In order to realize control and reduce power cost,the controller is designed.The testing experiments show that the controller has excellent performance,reliable operation and low cost.

Control Strategies for Digital Twin Systems

With the continuous breakthrough in information technology and its integration into practical applications, industrial digital twins are expected to accelerate their development in the near future. This paper studies various control strategies for digital twin systems from the viewpoint of practical applications.To make full use of advantages of digital twins for control systems, an architecture of digital twin control systems, adaptive model tracking scheme, performance prediction scheme, performance retention scheme, and fault tolerant control scheme are proposed. Those schemes are detailed to deal with different issues on model tracking, performance prediction, performance retention, and fault tolerant control of digital twin systems. Also, the stability of digital twin control systems is analysed. The proposed schemes for digital twin control systems are illustrated by examples.

Digital controller for hybrid filter in HVDC based on approximate inverse system

In order to eliminate the characteristic harmonics in high voltage direct current(HVDC)transmission systems and to simplify the analog controller structure,this paper proposes a new digital controller by adopting an approximate inverse system control strategy according to the frequency response characteristic of the hybrid power filter.The pro-posed digital controller is implemented with a TMS320C32 DSP,including a series of parallel digital band-pass filters,phase shifters and amplifiers.The results of both simulations based on PSCAD and experiments on a 30 kVA HVDC system prove that the proposed digital control system is sta-ble and efficient for eliminating the harmonics.

A multimode digital controller IC for flyback converter with high accuracy primary-side feedback

A digital controller IC for the flyback converter with primary-side feedback is proposed. The controller is used for adapter charger or LED driver applications. To obtain high accuracy for the primary-side feedback, a digital primary-side sensing technology is adopted, which can auto-track the knee point of the primary auxiliary winding voltage. Furthermore, an internal digital compensator eliminates the need for external loop compensation components while achieving excellent line and load regulation. The controller could output both constant voltage and constant current depending on the load current. Pulse width modulation and pulse frequency modulation are used in constant voltage mode while quasi-resonant control is used in constant current mode. The digital controller is validated by using FPGA.

Systematic design method for PI controller with Virtual Resistor-based Active Damping of LCL filter

The Virtual Resistor based Active Damping(VR-AD) is widely employed in converters connected to the grid via LCL filters in order to mitigate the inherent resonance of the filters. Nevertheless, in digitally controlled systems, the PWM and the calculating delays modify the system characteristics in terms of frequency and phase, thus destabilizing the system and degrading the VR-AD performances, mainly in low switching frequencies. Moreover, the stability of the system is greatly affected under weak grid operation characterized by large grid impedance variation. This paper solves these problems by proposing a systematic, robust and optimized design procedure of voltage oriented PI control(VOC) with VRAD. The considered design procedure ensures robust control(sufficient stability margins) and high quality of grid current(reduced steady-state error and minimized THD value) despite the negative impact of digital time delay, grid impedance variation and filter parameters change. Simulation and experimental results are presented to show robustness and efficiency of the suggested design procedure.

2D DIGITAL SIMPLIFIED FLOW VALVE

The 2D digital simplified flow valve is composed of a pilot-operated valvedesigned with both rotary and linear motions of a single spool, and a stepper motor under continualcontrol. How the structural parameters affect the static and dynamic characteristics of the valve isfirst clarified and a criterion for stability is presented. Experiments are designed to test theperformance of the valve. It is necessary to establish a balance between the static and dynamiccharacteristics in deciding the structural parameters. Nevertheless, it is possible to maintain thedynamic response at a fairly high level, while keeping the leakage of the pilot stage at anacceptable level. One of the features of the digital valve is stage control. In stage control thenonlinearities, such as electromagnetic saturation and hysteresis, are greatly reduced. To a largeextent the dynamic response of the valve is decided by the executing cycle of the control algorithm.

Digital Servo Control of a Robotic Excavator

An electro-hydraulic control system is designed and implemented for a robotic excavator known as the Lancaster University Computerised and Intelligent Excavator （LUCIE）. The excavator is being developed to autonomously dig trenches without human intervention. Since the behavior of the excavator arm is dominated by the nonlinear dynamics of the hydraulic actuators and by the large and unpredictable external disturbances when digging, it is difficult to provide adequate accurate, quick and smooth movement under traditional control methodology, e.g., PI/PID, which is comparable with that of an average human operator. The data-based dynamic models are developed utilizing the simplified refined instrumental variable （SRIV） identification algorithm to precisely describe the nonlinear dynamical behaviour of the electro-hydraulic actuation system. Based on data-based model and proportional-integral-plus （PIP） methodology, which is a non-minimal state space method of control system design based on the true digital control （TDC） system design philosophy, a novel control system is introduced to drive the excavator arm accurately, quickly and smoothly along the desired path. The performance of simulation and field tests which drive the bucket along straight lines both demonstrate the feasibility and validity of the proposed control scheme.

A comparative study of digital low dropout regulators

Granular power management in a power-efficient system on a chip(SoC)requires multiple integrated voltage regulators with a small area,process scalability,and low supply voltage.Conventional on-chip analog low-dropout regulators(ALDOs)can hardly meet these requirements,while digital LDOs(DLDOs)are good alternatives.However,the conventional DLDO,with synchronous control,has inherently slow transient response limited by the power-speed trade-off.Meanwhile,it has a poor power supply rejection(PSR),because the fully turned-on power switches in DLDO are vulnerable to power supply ripples.In this comparative study on DLDOs,first,we compare the pros and cons between ALDO and DLDO in general.Then,we summarize the recent DLDO advanced techniques for fast transient response and PSR enhancement.Finally,we discuss the design trends and possible directions of DLDO.

Digital control of pulsed gas metal arc welding inverter using TMS320LF2407A

A digital control of pulsed gas metal arc welding inverter was proposed. A control system consisting of analogue parts was replaced with a new digital control implemented in a TMS320LF2407A DSP chip. The design and constructional features of the whole digital control were presented. The resources of the DSP chip were efficiently utilized and the circuits are very concise, which can enhance the stability and reliability of welding inverter. Experimental results demonstrate that the developed digital control has the ability to accomplish the excellent pulsed gas metal arc welding process and the merits of the developed digital control are stable welding process, little spatter and perfect weld appearance.

Modelling and Identification of a Digital Feed Drive

In many cases, the cutting method is usually adopted for the efficient machining of non-circular body of revolution and a feed drive is needed to actuate the cutting tool to and fro according to input signal wave. The feed drive for the purpose is required of fast response and accurate positioning. Both of these are highly dependent upon the actuating elements. Several schemes of actuation are specially interested. One is the introduction of piezoelectric actuation. However, the tiny working stroke of the piezoelectric material limits its application to a narrow range. Another is the application of electro-magnetic actuator. An innovative feed drive actuated by the stepper motor is introduced for the purpose. For a conventional step operating mode, a stepper motor can only be controlled to position at finite discrete points. Thus, when it is applied as an actuator of the feed drive, it is very difficult to maintain high accuracy and fast response. To eliminate quantitative error, the stepper motor is controlled under the continual mode. It is achieved with a micro-controller system and a built-in control algorithm program, called "tracking algorithm". Within each sampling cycle, the micro-controller will sample the input signal and the time interval will be divided into two parts according to the relative position between two adjacent stepping points. The phase coils correspondent to the two adjacent stepping points are energized respectively with calculated time duration. In the way, the motion of the tool frame smoothly tracks the input signal. This paper presents modeling and identification of frequency response of the proposed drive. The dynamic response of the feed drive is manly decided by the natural frequency of the stepper motor. For the conventional small-size stepper motors, the natural frequency is within the range 200～400 Hz. Experimental results show that the stepper motor actuated tool frame can smoothly keep in track of the input signal wave under "tracking control". The bandwidth of frequency of the feed drive exceeds 310 Hz.

A digital controlled alternating electromagnetic stirring generator based on dual inverter structure

A digital controlled alternating electromagnetic stirring generator is proposed in this paper. The main circuit of the generator makes use of dual inverter structure among which the former inverter uses full bridge zero voltage switching topology and the latter inverter uses full bridge inverter circuit. To improve the dynamic response performance, the inverting frequency of the former inverter is as high us 100 kHz. The Cortex-M3 kernel based ARM microcontroller LM3S818 is adopted as the cybernetics core of the digital control system to achieve accurate, stable and flexible control of the generator. All the PWM signals for the former and latter inverters are generated by the LM3S818 directly. The constant current characteristic of the former inverter is obtained through current close-loop feedback control, and can ensure the operation safety when the output current waveform is at zero crossing point. Both simulation and experiment results show that the proposed generator is with such advantages as wide soft-switching range, perfect control accuracy and flexible waveform modulation, and can fulfill the requirements of electromagnetic stirring process.

Software Development for Digital Control of WDW Series Testing Machine and Measurement of K_(IC)

Software has been developed for digital control of WDW series testing machine and the measurement of fracture toughness by modularized design. Development of the software makes use of multi-thread and serial communication techniques, which can accurately control the testing machine and measure the fracture toughness in real-time. Three-point bending specimens were used in the measurement. The software operates stably and reliably, expanding the function of WDW series testing machine.

Digital close loop control system for current-programmed mode arc welding inverter

A small-signal model of current programmed mode pulse width modulation converter including the equivalent sampling effect is introduced and analyzed. In this model, an addition pole is brought out by the sampling effect in the current loop gain, and it affects dynamic bandwidth and stability of the inner current loop. By selecting the appropriate stability parameter which determines the additional pole and describes the degree of peaking in closed loop transfer function, a control model of current programmed full bridge arc welding inverter with maximum frequency bandwidth and stability can be obtained. Small and large amplitude pulse current outputs are employed in simulations and experiments and results validate the design method.

Design of low-power high-frequency digital controlled DC-DC switching power converter

This paper models a low-power high-frequency digitally controlled synchronous rectifier （SR） OUCK converter. The converter is a hybrid system with three operation modes. Digital PID controler is used. Key problems such as quantization resolution of digital pulse-width modulation （DPWM） and steady-state limit cycles of digital control switching model power supply （SMPS） are discussed, with corresponding solutions presented. Simulation of a digital control synchronous buck is performed with a fixed-point algorithm. The results show that the described approach enables high-speed dynamic performance.

THE FEEDBACK DELAY IN DIGITAL CONTROL

It is a fact that the feedback delay actually arises in digital control systems. It is necessary to modify the structure of digital control systems and develop new control algorithms, which is done in this paper. A great number of digital computer simulation experiments have shown the obvious advantage of the new algorithms.

Research on a 50 kW digital inverter type plasma cutting power supply

To improve energy transfer efficiency and quality controllability of plasma cutting process of thick plate, a 50 kW digital inverter type plasma cutting power supply is developed. The power supply main circuit is composed of two similar power electronic building blocks, using full-bridge high frequency inverter topology to achieve efficient energy transformation. To realize accurate digital control of the plasma cutting power supply and cooperative work of the two power electronic building blocks, the Cortex-M4 type ARM microprocessor-TM4C123GH6PGE is used as the cybernetic core of the control system. To improve the response performance and reliability of the power system, close-loop control and peak current feedback control modes are adopted. In the end, the experimental study of the performance testing and cutting of the developed prototype is carried out. The results indicate that the design is rational and feasible, and the developed high power plnsma cutting power supply works reliably with excellent performance.