A Linear VCO Using Single CFA and Analog Multipliers: Quadrature Oscillator Implementation

A new linear voltage-controlled oscillator (LVCO) implementation using single AD-844 CFA with a pair of AD-835 multiplier devices and a pair of grounded capacitors is proposed. The open-loop transfer function of the topology is analyzed wherein the concept of Short-Circuit Natural Frequency (SCNF) is applied to derive the sinusoid oscillator implementation. The proposed oscillator circuit is then restructured to yield a linear voltage-controlled quadrature oscillator (LVCQO) after appropriate cascade with a CFA-based active integrator. The oscillation frequency is linearly tunable ([Formula: see text][Formula: see text]MHz) by the multiplier control voltage ([Formula: see text]. Subsequently, a high-[Formula: see text] selective band-pass (BP) filter is derived. Effects of the CFA port roll-off parameters and its parasitic capacitors ([Formula: see text] had been analyzed to be negligible. Measured oscillator response exhibited a THD [Formula: see text]%, a linearity error ([Formula: see text]% and a phase noise figure of ([Formula: see text]104 dBc/Hz at 24-kHz offset.

Modeling of Average Current in Ideal and Non-Ideal Boost and Synchronous Boost Converters

This paper provides a modeling approach for average current control (ACC) operating in open-loop configuration. The converters chosen are non-ideal boost and synchronous boost converters operating in continuous conduction mode (CCM). Initially, these converters are mathematically modeled considering all the non-idealities using volt-sec and amp-sec balance equations and simulated using MATLAB and Simulink. The open-loop transfer function of the switch current or inductor current (Gid) to the duty ratio is derived using the state space averaging (SSA) technique and analyzed using MATLAB/Simulink. It is observed that the Gid of the converters is highly stable in open loop. A larger magnitude resonance is observed in ideal boost and synchronous boost converters than the non-ideal converters. However, the low frequency gain and the crossover frequency remained the same. With the increase in the load resistance, higher resonance and lower low frequency gain is observed in non-ideal boost and non-ideal boost synchronous boost converters. The derived transfer function is validated against the standard switch model using LTSpice software.

Optimizing the Control System of Clinker Cooling: Process Modeling and Controller Tuning

This paper aims to present efficient efforts to optimize the proportional-integral-differential (PID) controller of clinker cooling in grate coolers, which have a fixed grate and at least two moving ones. The process model contains three transfer functions between the speed of the moving grate and the pressures of the static and moving grates. The developed software achieves the identification of the model parameters using industrial data and by implementing non-linear regression methods. The design of the PID controller follows a loop-shaping technique, imposing as a constraint the maximum sensitivity, Ms, of the open-loop transfer function and providing a set of PIDs that satisfy a range of Ms. A simulator determines the optimal PID sets among those calculated at the design step using the integral of absolute error (IAE) as a performance criterion. The combination of a robustness constraint with a performance criterion, Ms and IAE respectively, leads to an area of controllers with Ms belonging to the range of 1.2 to 1.35. The IAE is between 4.2% and 4.8%, depending on the set-point value. PID sets located near the middle of this area can be chosen and implemented in the cooler’s routine operation.

Interaction Phenomena to Be Accounted for Human-Induced Vibration Control of Lightweight Structures

Inertial mass controllers, including passive, semi-active and active strategies, have been extensively used for canceling human-induced vibrations in lightweight pedestrian structures. Codes to check the vibration serviceability and current controller design approaches assume that both excitation forces and controller forces are the same on a flexible structure and on a rigid structure. However, this fact may not be assumable since interaction phenomena arise even for moderately lightweight structures. Analyzing two case studies in this paper, interaction phenomena involved in the frequency-domain-based design of passive and active inertial mass dampers are discussed. Thus, a general vibration control problem including the interaction phenomena is set hereby. Concretely, this paper deeply discusses the following issues: (i) how the structure to be controlled is affected when human-structure interaction is presented for deterministic and stochastic conditions, (ii) the closed-loop transfer function of the controlled structure including a passive inertial mass damper, and (iii) the closed-loop transfer function of the controlled structure including an active inertial mass damper. In addition, the performed analysis considers the actuator dynamics and the actuator-structure interaction.

Multi-Point Suspension Design and Stability Analysis of a Scaled Hoop Truss Antenna Structure

This paper proposes a scaled model to investigate the dynamic characteristics and stability of a hoop truss antenna on the ground. First, the statically indeterminate equation for the multi-point suspension is established, along with the voltage of the suspension motor calculated. Then the transfer function of the system is theoretically established. The scaled model is established before and after suspension, and the static deformation and natural frequency of the system are obtained by calculation and measurement. There exist the shaking mode and nodding mode. Also, a vibration experiment is conducted for the system to obtain the vibration response. With this, the transfer function is identified by the system identification method, which appears to be of the second order, and the stability is analyzed through the zero pole diagram. The experiment results show that the first two frequencies are close before and after suspension. Moreover, the stability of the system can be judged by the open-loop transfer function. It is concluded that the vibration experimental data of the scaled model can be used as a reference for the large hoop truss antenna structure.

Analytical design of the fractional order controller and robustness verification

<div data-canvas-width="397.2227827050999">This paper proposes a fractional order controller (FOC) for the level control problem of the coupled tank system, using the desired time domain specifications. The coupled tank system is used in the chemical industries for the storage and mixing of liquids. The FOC is designed analytically using the direct synthesis method. In the direct synthesis method, the Bode's ideal loop transfer function is chosen as the desired transfer function. Bode's loop transfer function has the advantages like robustness to system gain variations, constant phase and very high gain margin. Performance of the proposed controller is compared with the state of the art literature. Simulation results showed that the proposed controller has the least peak overshoot. The robust performance of the proposed controller is also the best. Robust stability of the system with the proposed controller is verified, and the system is found to be robustly stable.</div>

Relative Stability of Electrical into Mechanical Conversion with BLDC Motor-Cascade Control

The conversion of the electrical energy into the mechanical is usually realized by a motor, power electronics and cascade control. The relative stability (Θ-stability), i.e., the displacement of its eigenvalues of this system is analyzed for a drive with a BLDC motor. The influence of changing the basic parameters of the motor and power supply system on the drive operation is considered. 4th order closed-loop transfer-function of the cascade control is presented, where boundaries of the transfer-function coefficients are used. The cascade system which uncertainty of the resistance, inductance, flux and gain parameters is analyzed. Theoretical calculations for the cascade control, simulations and laboratory tests are included in the article.

Analytical Multiloop Control for Multivariable Systems with Time Delays

In this paper, a new design method with performance improvements of multiloop controllers for multivariable systems is proposed. Precise expression is developed to show the relationship between the dynamic- and steady-state characteristics of the multiloop control system and its parameters. First, an equivalent transfer function (ETF) is introduced to decompose the multivariable system, based on which the multiloop controller parameters are calculated. According to the ETF matrix property, an analytical expression for the PI controller for multivariable systems is derived in terms of substituting the ETF matrix for the inverse open-loop transfer function. In the proposed controller design method, no approximation of the inverse of the process model is needed, implying that this method can be applied to some multivariable systems with high dimensions. The simulation results obtained from several examples demonstrate the effectiveness of the proposed method.

U-Model and U-Control Methodology for Nonlinear Dynamic Systems

This study presents the fundamental concepts and technical details of a U-model-based control (U-control for short) system design framework, including U-model realisation from classic model sets, control system design procedures, and simulated showcase examples. Consequently, the framework provides readers with clear understandings and practical skills for further research expansion and applications. In contrast to the classic model-based design and model-free design methodologies, this model-independent design takes two parallel formations: (1) it designs an invariant virtual controller with a specified closed-loop transfer function in a feedback control loop and (2) it determines the real controller output by resolving the inverse of the plant U-model. It should be noted that (1) this U-control provides a universal control system design platform for many existing linear/nonlinear and polynomial/state-space models and (2) it complements many existing design approaches. Simulation studies are used as examples to demonstrate the analytically developed formulations and guideline for potential applications.