Closed-loop Digital Control Research Articles

A Digital Closed-Loop Control System for MEMS Resonant Pressure Sensors Based on a Quadrature Phase-Locked Loop

A Digital Closed-Loop Control System for MEMS Resonant Pressure Sensors Based on a Quadrature Phase-Locked Loop

Development of DSP-based TPS fully digital correction magnet power supply

The Taiwan Photon Source (TPS) is a third-generation 3 GeV synchrotron accelerator light source. After successfully operating for ten years since its first light in 2013, various subsystems are undergoing updates. In the context of magnet power supply upgrades, the trend toward digitization and high-precision modulation control is driving advancements worldwide. This study focuses on developing a fully digital correction magnet power supply (FDCMPS) based on a digital signal processor (DSP). The prototype utilizes a low-power, floating-point DSP with multiple communication functionalities as the core control unit. The output current is converted into digital values using current sensors and high-precision analog-to-digital converters. Discrete PI compensator algorithms are implemented within the DSP to generate pulse-width modulation (PWM) waveforms, driving a full-bridge (H-bridge) converter configuration with metal-oxide-semiconductor field-effect transistors (MOSFET). This forms a complete, fully digital closed-loop current control system. A virtual control interface is designed to operate the FDCMPS state. The control loop design of the prototype has been validated and demonstrates stable output bipolar current performance. When tested with a 0.1 V input reference signal, the prototype achieves a -3 dB bandwidth of 2.03 kHz. Finally, a hardware prototype circuit was constructed in the power supply laboratory, with an input voltage of 48 V, an output current of 10 A, and a maximum power of 400 W. Overall, the developed fully digital correction magnet power supply prototype showcases stable and high-performance output bipolar current performance. The system achieves total harmonic distortion of output current ripple within 0.3 mA peak to peak and long-term stability within ± 15 ppm. The successful implementation of the prototype establishes a solid foundation for advancing magnet power supply technology at the TPS.

Inductive Power Transfer Battery Charger with IR-Based Closed-Loop Control

A wireless battery charger with inductive power transfer (IPT) was proposed in this paper. The commonly used constant-current constant-voltage (CC-CV) charging method is accomplished by a closed-loop controlled IPT with a hybrid resonant circuit on the secondary side. A smooth transition between the CC stage and the CV stage can be made simply by swapping exactly the associated switches on resonant capacitors. The required charging voltage and current are regulated by controlling the phase-shifted angle of the high-frequency inverter on the primary side. To stabilize the charging current and voltage, a closed-loop digital controller was introduced with infrared (IR) transmission feedback. Precise regulation of the resonant inverter on a relative small ranged phase-shifted angle can be realized by two 16-bit microcontroller units (MCUs) with compact encoding and decoding techniques. A hybrid resonant inverter was designed for a 600 W prototype of the proposed IPT battery charger. Experimental results from exemplar cases have demonstrated that the battery charger can provide a stable charging current at the CC stage and then transit smoothly into the CV stage.

Design of the digital interface circuit system for MEMS gyroscope

In this paper, a digital closed-loop measurement and control system of MEMS vibrating silicon gyro is proposed, which includes the sensitive structure model of gyro and the design of interface circuit. Because of the high sensitivity and precision of the MEMS gyroscope under the condition of modal matching, the measurement and control circuit is established under the condition of modal matching. The system uses automatic gain control (AGC) to control the amplitude of self-excited oscillation of the driving loop, which has the characteristics of simple and quick start. First, the working principle of gyro sensitive structure is introduced and an interface circuit with digital drive and detection mode is designed. Second, a high precision one-bit sigma-Delta ([Formula: see text] analog-to-digital converter (ADC) is designed, and the signal-to-noise ratio (SNR) of the modulator is 102.5 dB at 10 kHz bandwidth. Third, a nonlinear multiplier is used in the driving loop to realize fast self-excited start-up of gyro, and a proportional integral (PI) controller is used in the self-excited loop to realize stable oscillation. Finally, Simulink is used to simulate and verify the sensitive structure model and the measurement and control system. The nonlinearity of the gyroscope is tested by experiment, and the well measurement and control precision of the gyro interface circuit is verified.

An Isolated Dual-Input Half-Bridge DC–DC Boost Converter With Reduced Circulating Power Between Input Ports

This article addresses a dual-input half-bridge DC–DC converter for proper utilization of renewable energy sources (RESs). The proposed system includes two different variable sources to examine the power distribution in each module, two high-frequency transformers (HFTs), and a three-leg converter (TLC) at secondary. The TLC is connected in parallel structure to gain reduced circulating power between input modules. This results in obtaining a compact design with a minimum number of switches. Complete steady-state analysis and control strategy of the proposed system have been analyzed. Digital closed-loop control has been implemented using the field programmable gate array (FPGA) controller to minimize the complexity of the control strategy. A laboratory prototype has been developed to justify the feasible operation of the proposed converter. Extensive tests result demonstrates the enhanced performance of the proposed system in effective utilization of power from different sources to feed the telecom load.

Fully-integrated DCDC buck converter based on PID algorithm

With the continuous development of power supply technology, the application of power management chips becomes more extensive, and the requirements for fully integrated power management chips are getting higher. This paper designs a buck converter with a fully integrated digital control circuit and power circuit with an output voltage of 2V. In voltage mode, digital pulse width modulation (DPWM) technology and PID algorithm are used, and a digital closed-loop control buck circuit system is designed by cadence tools. The performance of analog and digital closed-loop control circuits is compared at the same buck power stage. Under rated load conditions, the lock-up time of the digital control buck circuit is 826us, the output voltage ripple is 14.75mV, the response time of load sudden change at light load is about 900us, and the response time of load sudden change at heavy load is about 2ms.

Experimental implementation of a smart battery charger for electric vehicles charging station

In this paper, an implementation of a DC/DC buck converter for electric vehicles charging station and a DSP based closed-loop digital controller design are presented and analyzed. The aim of this work is to achieve an improved control strategy for a Li-ion battery charger implemented on a Real-time test platform. The test platform consists of a popular power pole board (MPCA75136) dedicated to studying the DC/DC converters, and a DSP development kit (TMS320F28379D) that is used to drive the DC/DC buck converter. The control strategy is based on a digital control system containing the closed-loop current controller followed by a pulse width modulation block, and on a real time state of charge estimation technique for a Li-ion battery. However, the overall control design is modeled on Simulink via block diagrams, and automatically generated code that is targeted into the DSP processor. Simulation and experimental results have shown the effectiveness of the proposed test bench and its external digital control strategy via a charging scenario for electric vehicles batteries.

An Adaptive Digital Neural Network-Like-PID Control Law Design for Fuel Cell System Based on FPGA Technique

This paper proposes an on-line adaptive digital Proportional Integral Derivative (PID) control algorithm based on Field Programmable Gate Array (FPGA) for Proton Exchange Membrane Fuel Cell (PEMFC) Model. This research aims to design and implement Neural Network like a digital PID using FPGA in order to generate the best value of the hydrogen partial pressure action (PH2) to control the stack terminal output voltage of the (PEMFC) model during a variable load current applied. The on-line Particle Swarm Optimization (PSO) algorithm is used for finding and tuning the optimal value of the digital PID-NN controller (kp, ki, and kd) parameters that improve the dynamic behavior of the closed-loop digital control fuel cell system and to achieve the stability of the desired output voltage of fuel cell. The numerical simulation results (MATLAB) package along with the schematic design experimental work using Spartan-3E xc3s500e-4fg320 board with the Xilinx development tool Integrated Software Environment (ISE) version 14.7 and using Verilog hardware description language for design testing are illustrated the performance enhancement of the proposed an adaptive intelligent FPGA-PID-NN controller in terms of error voltage reduction and generating optimal value of the hydrogen partial pressure action (PH2) without oscillation in the output and no saturation state when these results are compared with other controllers.

Digital PID Control Law Design for Fuel Cell Model Based on FPGA Emulator System

This paper proposes an off-line adaptive digital Proportional Integral Derivative (PID) control algorithm based on Field Programmable Gate Array (FPGA) for Proton Exchange Membrane Fuel Cell (PEMFC) Model. The aim of this research is to obtain the best hydrogen partial pressure (PH2) value using FPGA emulator to design and implement a digital PID controller that track the fuel cell output voltage during a variable load current applied. The off-line Particle Swarm Optimization (PSO) algorithm is used for finding and tuning the optimal value of the digital PID controller parameters that improve the dynamic behavior of the closed loop digital control fuel cell system and to achieve the stability of the desired output voltage of fuel cell. The numerical simulation results (MATLAB) package and FPGA emulator experimental work show the performance of the proposed FPGA-PID controller in terms of voltage error reduction and generating optimal value of the (PH2) control action without oscillation in the output and no saturation state when these results are compared with other control methodology.

Design of control algorithm for accelerator magnet power supply with large time constant load

High Energy Photon Source-Test Facility (HEPS-TF) is a pre-research project for the construction of high energy synchrotron radiation source in the 12th five-year plan period. The purpose is to research the key technology and develop the key equipment of high energy synchrotron radiation source. Superconducting 3W1 magnet is the first self-developed superconducting wiggler magnet in China, and it is also one of the key research topics of HEPS. The author has completed a new digital closed-loop control algorithm for the superconducting 3W1 magnet with large load time constant and the nonlinear characteristics of inductance increasing with current, namely three-branch structure algorithm. In the face of the rapid development of high energy accelerator technology, the application of intelligent technology has become an inevitable development trend in the field of accelerator magnet power supply technology. Although the digital control of accelerator magnet power supply has been widely used, it is the first time to apply the new closed-loop control algorithm to realize fast adjustment and precision tracking in accelerator superconducting magnet power supply in China. According to the nonlinear characteristics of inductance and output current of superconducting magnet, a new digital closed-loop control algorithm for the load of superconducting magnet power supply with large time constant is proposed. This algorithm is quite different from the traditional algorithm and can attain the independent tracking and adjustment of the control target. Finally, by testing the ripple, error and stability of superconducting 3W1 magnet power supply, the correctness, practicability and reliability of power supply system as well as the digital control algorithm are verified. The results provide a new idea for the control of accelerator magnet power supply.

Dynamic simulation model of Fiber Optical Current Transformer considering error factors

The paper studies and establishes the dynamic model of fiber optical current transformer by MATLAB. The equivalent model of FOCT’s digital closed loop control system is created by reasonably simplifying deviation and feedback of FOCT. By analyzing the four components of FOCT’s main sources of error, 10 factors that cause FOCT measurement errors are obtained. Then the variable 10 error parameters are introduced into the model to establish a dynamic model of fiber optical current transformer considering the error factor. The model can evaluate the performance of the fiber optical current transformer by using the variable FOCT’s error parameters, Also, model dynamically combines the FOCT’s related parameters and environmental factors with the transformer’s transfer characteristics and reflects the influence of FOCT error factors on FOCT performance.

Digital Closed-Loop Control Strategy to Maintain the Phase Shift of a Multi-Channel BCM Boost Converter for PFC Applications

This paper presents a novel closed-loop digital control scheme to maintain proper interleaving operation of a multi-channel boundary-conduction-mode boost converter used in power-factor-correction applications. The proposed control scheme is suitable for implementation on a low-cost microcontroller. This is made possible by executing the control scheme at a constant sampling rate that is much slower than the maximum switching frequency of the converter. The performance of the control scheme is further improved by using an adaptive gain that scales with the on -time of the converter, which provides optimal phase-shift control and stability under all operating conditions. The digital closed-loop control scheme is validated experimentally on a three-channel 1-kW prototype ac–dc converter. The converter has an output voltage of 400 V and a universal input voltage range of 85–265 V. The prototype converter uses a low-cost microcontroller while demonstrating correct interleaving operation.

The design and implementation of a broadband digital low-level RF control system for the cyclotron accelerators at iThemba LABS

iThemba LABS has successfully designed a new broadband digital low-level RF control system for cyclotrons, that operates over the wide frequency range of 2–100 MHz and can achieve peak–peak amplitude and phase stabilities of 0.01% and 0.01°, respectively.The presented system performs direct digital synthesis (DDS) to directly convert the digital RF signals to analog RF and local-oscillator (LO) signals with 16-bit amplitude accuracy, programmable in steps of 1μHz and 0.0001°. Down-conversion of the RF pick-up signals to an optimal intermediate frequency (IF) of 1 MHz and sampling of the IF channels by 16-bit, single sample-latency 10 MHz ADCs was implemented to allow digital high-speed low-latency in-phase/quadrature (I/Q) demodulation of the IF channels within the FPGA. This in turn allows efficient real-time digital closed-loop control of the amplitude and phase of the RF drive-signal to be achieved.The systems have been successfully integrated at iThemba LABS into the K=8 and K=10 injector cyclotrons (SPC1, and SPC2), the K=200 separated sector cyclotron (SSC), the SSC flat-topping system, the pulse-selector system and the AX,J, and K-line RF bunchers.The systems have led to a substantial improvement in the beam quality of the SSC at iThemba LABS with a reduction in beam losses by more than 90%. The design, implementation and performance is discussed.

Minimizing Torque Ripple of Highly Saturated Salient Pole Synchronous Machines by Applying DB-DTFC

Deadbeat-direct torque and flux control is a flux-observer-based high-bandwidth digital closed-loop torque control law that achieves the commanded torque at the end of each switching period. When flux estimation is accurate, instantaneous torque is fed back and undesirable pulsating torque is inherently minimized. This study presents real-time flux-observer-based torque ripple estimation of a highly nonlinear synchronous reluctance machine. Saturation and cross saturation are incorporated directly into the control law, and are considered in each switching period. Deadbeat torque response and torque ripple reduction is demonstrated experimentally. Finite element method simulations validate the torque ripple minimization.

The Analysis and Design of Closed-Loop Control System for MEMS Vibratory Gyroscopes

A digital closed-loop control system with all digital phase locked loop (ADPLL) is designed and optimized, in order to improve the bias stability and transient response of the gyroscope. The nonlinear mathematical models for the closed-loop amplitude and phase control system are established. The linearization method is applied to analyze the nonlinear models. The control parameters of the drive loop are optimized. The experimental results show that the phase deviation between the demodulation reference signal of the drive loop and the sense signal is less than 0.25° in the temperature range from-40°C to 60°C, within 0.15° of the variation. At room temperature, the overshoot amount of the gyroscope control system is 4.5% with setting time of 0.12s. The bias stability is 1.45°h. Compared to the analog control scheme, the digital control system has advantages of short setting time, small overshoot, short phase locked time, large locked range, high phase precision, etc.

On Automatic Resonant Frequency Tracking in LLC Series Resonant Converter Based on Zero-Current Duration Time of Secondary Diode

In order to achieve higher efficiency for the unregulated LLC series resonant converter, the switching frequency must be equal to the resonant frequency. However, since the converter works in open-loop condition, the switching frequency usually deviates from the resonant frequency in real converter. This paper proposed a new control method to track the resonant frequency of the unregulated LLC series resonant converter. Theoretically, the time of zero diode current in secondary is zero when the working frequency is equal or greater than the resonance frequency, and it is changed as the frequency varies when the working frequency is less than the resonance frequency. The proposed control algorithm is based on the time measurement of zero diode current to realize the resonance frequency tracking. A closed-loop digital controller is designed to realize the proposed tracking approach. The simulation and experiments are conducted to verify the proposed tracking approach. The simulation and experimental results show that (1) the switching frequency can be well controlled to track the resonant frequency, and (2) the tracking accuracy can be at least 96%.

A new digital control system based on the double closed-loop for the full-bridge inverter

The control system based on the primary current feedback mode can effectively suppress the magnetic bias and avoid the overcurrent for the full bridge inverter. But in the process of its digitalization, the magnetic bias signal can be missed easily and the control accuracy is low, resulting in poor system stability and reliability. First, a new double closed-loop digital control method is proposed, which has advantages of the magnetic bias suppression in the primary current feedback mode and fast fine current adjustment in the secondary current feedback mode. Second, results of theoretical analysis on system stability and simulation prove that the method is feasible. Third, a single-chip design idea based on analog-digital mixed field-programmable gate array (FPGA) is proposed, and the detailed design program is described for the submerged arc welding system, which has high integration and strong anti-interference. Experimental results show that the digital control system has high stability and reliability to produce high submerged arc welding quality.

An Approximate Dynamic Model of LCL- <formula formulatype="inline"><tex Notation="TeX">$T$</tex></formula>-Based Inductive Power Transfer Power Supplies

This paper analyzes the dynamics of an LCL-T-based inductive power transfer power supply, and aims to improve its reference tracking performance for dynamic roadway wireless powering applications using a digital PI controller. An approximate small-signal model of the power supply that describes how the power supply reacts to a perturbation in its input is derived using the generalized state-space averaging technique. The model is verified experimentally and shown to capture the supply dynamics. Limitations of the model and their implications are also discussed. Using the small-signal model, a closed-loop digital PI controller is designed to ensure a fast turn-on of a 20 kHz power supply at no-load in approximately 300 μs with no overshoot in the track current.

Circuit Design of Digital Closed Loop Control System for FOG

Fiber optic gyroscope (FOG) is a new angular rate sensor based on the Sagnac effect. It has been widely applied in the navigation control system of aircrafts, spacecrafts and ships. But its stability, reliability and miniaturization are always the research focuses and difficulties. This paper presented a circuit design method for the digital closed loop control system of FOG based on FPGA. Based on a large number of experiments, this paper summarized the parameter demands for each module of closed loop control circuit and designed a corresponding circuit using FPGA. The proposed dual closed loop technique improved the zero offset stability of FOG. The using of FPGA brought the digital signal processing by software, the system reliability and agility enhancement as well as the system miniaturization. Particularly, we discussed the problems of component selection and the anti-jamming measures for PCB design to improve the performances of the system. We also developed some samples of FOG using this design method. The experiments and tests show that the proposed method is efficient and valuable. The stabilities of zero-offsets of all samples are less than 0.075deg/h.

Circuit Design of Digital Closed Loop Control System for FOG

Circuit Design of Digital Closed Loop Control System for FOG