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Fixed-Time Control of the Lifting Axis of a CNC Machine Using a Permanent Magnet Synchronous Motor and a Fixed-Time Nonlinear Observer
(2026-07-01)
Cholahan, Varin
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Tangsrirat, Worapong
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Pukkalanun, Tattaya
This paper introduces an adaptive fixed-time position controller (AFxTPC) designed for the lifting axis servo mechanism of a computer numerical control (CNC) plasma machine. It integrates a permanent magnet synchronous motor, gearbox, and ball screw into a unified electromechanical model. The proposed AFxTPC combines a fixed-time terminal sliding surface function with adaptive fixed-time sliding mode control to achieve fixed-time convergence, precise tracking, and robustness in the presence of parameter uncertainties. A specially designed reaching law guarantees accurate trajectory tracking, while the fixed-time terminal sliding surface function effectively minimizes chattering near the sliding manifold. Importantly, a novel fixed-time nonlinear disturbance observer is developed to simultaneously estimate the unmeasured system states and lumped disturbances in real time within a guaranteed initial-state-independent settling time. These estimated values are explicitly fed back into controller for active disturbance compensation. The stability of the overall closed-loop system is rigorously established using Lyapunov stability theory. Simulation results demonstrate that the proposed observer-based controller achieves superior performance compared with conventional proportional–integral–derivative (PID) and standard sliding mode controllers. It exhibits zero steady-state error, reduced overshoot, minimal chattering, and strong robustness over a wide range of operating conditions.
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VDTA-Based Mixed-Mode Inverse Filter and Its Application to Mixed-Mode PID Controller
(2026-04-01)
Roongmuanpha, Natchanai
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Pukkalanun, Tattaya
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Faseehuddin, Mohammad
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Tangsrirat, Worapong
This paper presents a novel voltage differencing transconductance amplifier (VDTA)-based mixed-mode inverse filter capable of operating in voltage mode, transadmittance mode, transimpedance mode, and current mode using a single topology. The proposed configuration employs only three VDTAs with two resistors and three capacitors, offering low component count, high input/output impedance flexibility, and no requirement for component matching. It simultaneously realizes first-order inverse lowpass and highpass, as well as second-order inverse bandpass responses. A comprehensive non-ideal analysis, which includes the effects of VDTA parasitic impedances, determines the practical operating frequency range. The design is validated through PSPICE simulations using 0.18 μm CMOS technology, showing close alignment between theoretical predictions and simulation results, with cutoff frequencies of approximately 1.60 MHz and low power consumption of 0.972 mW. Further analyses confirm orthogonal tuning capability, acceptable temperature stability, and robustness against component tolerances. In a practical application, the proposed inverse filter is employed to implement a mixed-mode PID controller, which significantly improves transient response characteristics by reducing rise time, settling time, and steady-state error. These findings highlight the effectiveness and versatility of the proposed design for analog signal processing and control system applications.
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Single VDCC-Based Mixed-Mode First-Order Universal Filter and Applications in Bio-Signal Processing Systems
(2026-02-01)
Moonmuang, Pitchayanin
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Roongmuanpha, Natchanai
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Tangsrirat, Worapong
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Pukkalanun, Tattaya
This paper presents a compact mixed-mode first-order universal filter based on a single voltage differencing current conveyor (VDCC), which can function in all four possible operation modes, i.e., voltage mode (VM), trans-admittance mode (TAM), current mode (CM), and trans-impedance mode (TIM). The proposed configuration requires only two grounded resistors and one floating capacitor, which contributes to a low component count, facilitates integration, and allows for the electronic tunability of the pole frequency through the transconductance gain of the VDCC. This work also demonstrates two practical biomedical applications: an electrocardiogram (ECG) acquisition system utilizing the VM low-pass filter for noise suppression and a bioimpedance (BioZ) measurement system employing the proposed configuration-based CM oscillator circuit as a sinusoidal excitation source. The performance validation confirms the accuracy of impedance extraction and the preservation of waveforms using tissue-equivalent models. The results demonstrate that the proposed VDCC-based filter offers a compact, power-efficient, and versatile analog signal-processing solution suitable for modern biomedical instrumentation.
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Grounded Series and Parallel RL/RC Immittance Simulators Using a Single Second-Generation Voltage Conveyor
(2026-01-01)
Roongmuanpha, Natchanai
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Tangjit, Jetwara
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Pukkalanun, Tattaya
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Faseehuddin, Mohammad
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Tangsrirat, Worapong
This work proposes the active simulation of grounded series and parallel resistive-inductive (RL) and resistive-capacitive (RC) immittance functions employing a single second-generation voltage conveyor (VCII) and three passive components. The two configurations are designed for series RL and RC immittance simulation and RL and parallel RC immittance simulation, respectively. All of the simulated immittance functions can be realized without any specific component matching or cancellation limitations. The proposed series and parallel RL and RC immittance function simulators have been simulated with PSPICE program based on 0.18 µm CMOS process parameters to validate the theoretical study. The first-order inverse filters, biquadratic filter, and synthetic lossless inductor applications, constructed with the proposed simulator circuits, are designed and evaluated to further demonstrate the practical usefulness of the designed simulators.
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Automated Elderly-Tracking Robot Prototype Using an AI-Based Vision Camera
(2026-01-01)
Pimpol, Jirapun
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Mongkolwai, Pratya
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Pukkalanun, Tattaya
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Tangsrirat, Worapong
This paper presents the design and implementation of an automated elderly-tracking robot prototype that integrates an AI-based HuskyLens vision sensor with ultrasonic sensors for target detection, tracking, and obstacle avoidance. Sensor data are processed by an Arduino UNO microcontroller, which controls TorqueNADO motors to achieve autonomous navigation and real-time motion control. The system also incorporates an ESP32-CAM module to provide live video streaming of the elderly user via the Blynk smartphone application, enabling remote monitoring over the Internet. In addition, the prototype supports a maximum payload of 3 kg for carrying essential lightweight items for elderly users. Experimental results demonstrate that the proposed robot meets the intended design objectives and validates the practical feasibility of the system.
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All-Grounded Passive Component Mixed-Mode Multifunction Biquadratic Filter and Dual-Mode Quadrature Oscillator Employing a Single Active Element
(2025-09-01)
Roongmuanpha, Natchanai
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Tangjit, Jetwara
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Faseehuddin, Mohammad
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Tangsrirat, Worapong
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Pukkalanun, Tattaya
This paper introduces a compact analog configuration that concurrently realizes a mixed-mode biquadratic filter and a dual-mode quadrature oscillator (QO) by employing a single differential differencing gain amplifier (DDGA) and all-grounded passive components. The proposed design supports four fundamental operation modes—voltage-mode (VM), current-mode (CM), trans-impedance-mode (TIM), and trans-admittance-mode (TAM)—utilizing the same circuit topology without structural modifications. In filter operation, it offers low-pass, high-pass, band-pass, band-stop, and all-pass responses with orthogonal and electronic pole frequency and quality factor. In oscillator operation, it delivers simultaneous voltage and current quadrature outputs with independent tuning of oscillator frequency and condition. The grounded-component configuration simplifies layout and enhances its suitability for monolithic integration. Numerical simulations in a 0.18-μm CMOS process with ±0.9 V supply confirm theoretical predictions, demonstrating precise gain-phase characteristics, low total harmonic distortion (<7%), modest sensitivity to 5% component variations, and stable operation from −40 °C to 120 °C. These results, combined with the circuit’s low component count and integration suitability, suggest strong potential for future development in low-power IoT devices, adaptive communication front-ends, and integrated biomedical systems.
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Two-Quadrant Current-Mode Logarithmic and Anti-logarithmic Amplifiers with Temperature Compensation
(2025-09-01)
Pukkalanun, Tattaya
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Roongmuanpha, Natchanai
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Tangsrirat, Worapong
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Suesut, Taweepol
This paper proposes circuit topologies for realizing two-quadrant current-mode logarithmic and anti logarithmic amplifier configurations with temperature compensation. The design approach employs the translinear approach to generate the output currents that directly correspond to the absolute values of the logarithmic and anti logarithmic functions. The proposed circuits can operate at a low-level supply voltage of 2V with both input and output current signals. A detailed examination of the non-ideal circuit performance has also been considered. To validate their functionality and illustrate their superior thermal stability, the developed circuits have been simulated. All simulations were conducted via PSPICE for a real bipolar transistor model of the HFA3096 technology.
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Differential Difference Gain Amplifier (DDGA) and Its Applications
(2025-07-01)
Satansup, Jetsdaporn
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Pukkalanun, Tattaya
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Tangsrirat, Worapong
This article introduces a CMOS circuit realization of the fully balanced differential difference gain amplifier (DDGA). The proposed DDGA is realized using four floating current sources operating under dual supply voltages of approximately ∓0.9 V. The proposed circuit can function as a differential difference gain amplifier with electronically adjustable gain both in voltage and current-modes. The application designs of the DDGA to implement a single-input three-output universal biquad filter and voltage-mode quadrature oscillator circuit are also suggested. PSPICE simulation results for the proposed DDGA and its applications are provided using 0.18-μm CMOS technology from TSMC.
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VDGA-Based Resistorless Mixed-Mode Universal Filter and Dual-Mode Quadrature Oscillator
(2025-05-01)
Channumsin, Orapin
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Tangjit, Jetwara
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Pukkalanun, Tattaya
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Tangsrirat, Worapong
This study introduces an electronically tunable resistorless mixed-mode universal filter and dual-mode quadrature oscillator configuration utilizing merely two voltage differencing gain amplifiers and two grounded capacitors. The suggested filter can perform all generic biquadratic filter functions in all four modes: voltage mode, trans-admittance mode, current mode, and trans-impedance mode, while utilizing the same design. The pole frequency and the quality factor can be tuned electronically and orthogonally by means of the transconductances of the voltage differencing gain amplifier. The dual-mode quadrature oscillator featuring both voltage and current outputs can also be obtained from the proposed filter core. It additionally provides separate electronic control of the oscillation condition and frequency. Several PSPICE simulations with the TSMC 0.18 μm CMOS model confirm the feasibility of the proposed configurations. Both proposed circuits were experimentally evaluated using commercially available integrated circuit LM13600s. Both simulation and experimental results have validated the performance of the design.
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Cascadable First-Order and Second-Order Inverse Filters Based on Second-Generation Voltage Conveyors
(2025-02-01)
Roongmuanpha, Natchanai
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Likhitkitwoerakul, Nutcha
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Pukkalanun, Tattaya
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Faseehuddin, Mohammad
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Tangsrirat, Worapong
This study introduces four novel configurations of first-order and second-order multifunction inverse filters in both voltage-mode (VM) and current-mode (CM) using second-generation voltage conveyors (VCIIs). The first-order VM and CM inverse filters utilize only three passive components together with one VCII for VM and two VCIIs for CM realizations, which can provide lowpass and highpass inverse filter responses. The latter, second-order VM and CM multifunction inverse filters, can be constructed using the corresponding first-order inverse filters as their core circuits. These filters offer all the basic inverse filter functions, including lowpass, bandpass, and highpass inverse responses with all gains obtained from the same design. All the inverse filter realizations are cascadable. No component matching requirements are necessary for all filter responses. The non-ideal effects of the VCII on the performance of the proposed inverse filters are thoroughly examined. To prove the feasibility of the designs, the PSPICE program performed several simulations, utilizing model parameters of 0.18 µm CMOS technology. Some testing experiments were conducted using the commercially available IC-type AD844s for evaluating the practical performance of the designed inverse filters.

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