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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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On the Design of Differential Difference Transconductance Amplifier (DDTA) and Its Applications
(2026-03-01)
Channumsin, Orapin
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Yaruan, Panurut
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Tangsrirat, Worapong
This paper presents the design and implementation of a novel active building block termed the Differential Difference Transconductance Amplifier (DDTA). The proposed DDTA integrates the characteristics of the Differential Difference Amplifier (DDA) and the Transconductance Amplifier (TA) to enhance flexibility in analog signal processing. It comprises three TA stages—two forming a DDA structure and one functioning as a TA—allowing independent electronic tuning of transconductance gain (gm). The DDTA features a simple architecture, wide input capability, extremely high input impedance, and high output resistance at both intermediate and output current terminals, enabling accurate current-mode signal processing with minimal loading effects. To demonstrate its versatility, a voltage-mode universal biquadratic filter and dual-mode quadrature oscillator, both based on a single DDTA and utilizing only two capacitors, have been designed and simulated. PSPICE simulation results confirm wide linear voltage-to-current conversion, wideband transconductance performance, and robust impedance characteristics, all in excellent agreement with theoretical predictions. These features validate the effectiveness and practicability of the proposed approach for modern analog circuit designs.
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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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Low-Cost Smartphone-Controlled Exercise Machine for Arm and Leg Muscles
(2026-01-01)
Pimpol, Jirapun
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Channumsin, Orapin
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Pattoom, Pongwat
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Weawthaisong, Wipakpong
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Singusaha, Orathai
This work proposes the design of a smart exercise machine for arm and leg muscles. The designed muscle arm and leg exercise machine can be controlled wirelessly through a smartphone application, which features a 3-level speed adjustment function. The motor speeds for arm muscle exercises are defined as 180, 210, and 240 rpm, while the speeds for leg muscles are set as 240, 270, and 300 rpm, respectively. In addition, the proposed machine incorporates a time function for muscle exercise and it can control the spin direction to rotate either forward or backward, depending on the requirement, using a microcontroller. Furthermore, it can display the distance traveled by an application on a smartphone. The experimental operation of the automatic arm and leg exercise machine revealed that it could accomplish its intended functionality.
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Design and Synthesis of Capacitance Multiplier Using LT1228s and a Grounded Capacitor
(2026-01-01)
Channumsin, Orapin
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Roongmuanpha, Natchanai
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Likhitkitwoerakul, Nutcha
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Tangsrirat, Worapong
In this study, the design and synthesis of a grounded capacitance multiplier is discussed. The proposed circuit consists of two commercially available integrated circuits (ICs) named LT1228, together with a single grounded capacitor as a passive element. The transconductance gain of LT1228 allows for electronic control of the simulated equivalent capacitance value. The LT1228 transconductance gain is easily adjusted through the external bias current, which has a wide adjustable range of 1 µA to 1 mA. No component matching is required for the designed simulator. A non-ideal analysis of the proposed circuit has been investigated in detail. The workability of the proposed circuit and its application example as a first-order lowpass filter has been confirmed with the theoretical findings through PSPICE software. The results indicate that the proposed simulator has excellent performance and matches the theory.
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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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2D-CNN Based Classification on Water Leakage Identification in Automatic Pump
(2026-01-01)
Satthamsakul, Sutham
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Rattanakun, Kritsana
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Khummongkol, Rojanee
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Tangsrirat, Worapong
This study proposes an approach for classification of unusual in automatic water pump systems, especially on a water leakage, one of the key issues that can significantly affect system efficiency and cause serious damage. The method utilizes motor current signals, which are transformed into 2D spectrograms using the Short-Time Fourier Transform (STFT). These spectrograms are then classified by a 2D Convolutional Neural Network (2D-CNN) Designed to determine between usual and unusual operating conditions with high accuracy. Experimental results indicate that the model can effectively detect unusual and leakage events when trained with appropriate parameters, such as a learning rate of 0.001 and 60 training epochs. This model serves as an efficient tool for preventing system failures and reducing maintenance costs in automatic water pump systems.
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Grounded Immittance Simulation and PID Control Application
(2026-01-01)
Channumsin, Orapin
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Unhavanich, Sumalee
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Roongmuanpha, Natchanai
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Tangsrirat, Worapong
This communication introduces a grounded immittance function simulator. The circuit employs a single differential voltage to current converter (DVTC) in association with three passive elements. The grounded series type RL and RC simulator can be realized by selecting the proper position of all passive elements. The equivalent resistance, inductance, and capacitance accomplished from the proposed circuit can be adjusted with a passive resistor. DVTC non-idealities on the proposed simulator are also discussed in detail. The voltage mode PID controller has been suggested as an application using the proposed simulator. The performance of the proposed simulator and controller applications have been carried out through PSPICE simulation. The results are certified by the theoretical prediction.
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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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