Cascade Compensation Research Articles

Distributed Leader-Following Consensus of Feedforward Nonlinear Delayed Multiagent Systems via General Switched Compensation Control.

This work examines the distributed leader-following consensus problem of feedforward nonlinear delayed multiagent systems involving directed switching topologies. In contrast to the existing studies, we focus on time delays acting on the outputs of feedforward nonlinear systems, and we permit that the partial topology dissatisfy the directed spanning tree condition. In the cases, we present a novel output feedback-based general switched cascade compensation control method that addresses the above-mentioned problem. First, we put forward a distributed switched cascade compensator by introducing multiple equations, and we design the delay-dependent distributed output feedback controller with the compensator. Subsequently, when the control parameters-dependent linear matrix inequality is met and the switching signal of the topologies obeys a general switching law, we prove that the established controller can render that the follower's state asymptotically tracks the leader's state by employing an appropriate Lyapunov-Krasovskii functional. The given algorithm allows output delays to be arbitrarily large and increases the switching frequency of the topologies. A numerical simulation is presented to demonstrate the practicability of our proposed strategy.

Self-Position Awareness Based on Cascade Direct Localization Over Multiple Source Data

The global positioning system (GPS), which provides ubiquitous location-awareness with a constellation of satellites, has become an instrumental function of multiple mass-market applications. Satellite signals, however, may not be capable of penetrating obstacles in harsh environments (e.g., urban canyons, tree canopies, and flyovers). Hence, GPS may not provide adequate localization accuracy for applications like autonomous vehicles. Resorting to data fusion of heterogeneous signals emanating from multiple anchors, we advocate a self-localization method that provides accurate estimates of the vehicle position. To be more specific, several heterogenous emitters whose positions are known are used as anchors to determine the vehicle's position based on the weighted direct position determination (DPD) method that eliminates nonhomogeneity among different emitters. However, the weighted DPD method requires an exhaustive search of the parameter search space and is thus time-consuming. To reduce the computational burden, we propose a weighted cascade compensation estimator (WCCE) that is tailored for real-time tracking and self-localization. The proposed WCCE outperforms traditional DPD methods in terms of computational complexity while achieving nearly comparable localization accuracy. The effectiveness of the proposed method is corroborated by extensive simulated examples.

Active disturbance rejection control for non-minimum phase systems under plant reconstruction

Active disturbance rejection control (ADRC) for non-minimum phase (NMP) systems is a challenging problem due to the conflict between stability and feedback tuning. The key point on this issue is to avoid heavy feedback tuning for robustness enhancement. We perform plant reconstruction to obtain an explicit expression of internal disturbance, such that it can be reduced by cascade compensation. Then, a new ADRC scheme is developed based on plant reconstruction and the internal stability criterion for ADRC system is derived. The stability conditions provide guidelines on the design of the cascade compensator and disturbance observer. It also indicates that the cascade compensation contributes to the robust stability of NMP systems. Simulation results of two typical NMP systems are provided to show the efficacy of the proposed ADRC scheme. Physical realizability is also demonstrated through experiments on a motion NMP system.

23 × 12 μm three‐stage amplifier using sub‐threshold active cascode compensation capable of driving very‐large‐load with no‐upper‐limit

An ultra-area-efficient three-stage amplifier is proposed by using sub-threshold active cascade compensation, which is able to drive very-large or ultra-large capacitive loads without sacrificing stability and power. Besides, external feed-forward path and slew-rate enhancer can significantly improve the large-signal transient response of the circuit. Designed and verified in 28 nm CMOS technology, the proposed amplifier occupies die area of 0.00028 mm 2 and consumes a power of 16.5 μW from 1.05 V supply. In addition, it can provide over 85 dB DC gain and is stable for any load larger than 4 nF, while the size of the entailed compensation capacitance is only 40 fF.

Optimum multiplierless compensators for sharpened cascaded‐integrator‐comb decimation filters

Folding band sharpening of the cascaded-integrator-comb filter results in a high passband droop. In applications requiring low passband deviation, the droop is reduced by connecting a low-order FIR compensator in cascade with the filter. In this Letter, the authors present a method for optimum design of compensators whose coefficients are expressed as sums of signed-power-of-two terms. The method is based on the minimisation of passband deviation, with specified total number of terms.

Control and Optimization of a Variable-Pitch Quadrotor with Minimum Power Consumption

Recently, there has been a rapid growth of interest in quadrotors with electric variable-pitch propellers. The control and optimization of such propellers are important factors for improving the flight performance of the vehicles. Therefore, the steady-state identification method to estimate the parameters of the mathematical model of the electric variable-pitch propeller is developed. The steady-state control and optimization scheme with minimum power consumption and the adaptive compensation scheme for the variable-pitch propeller are then proposed, based on which the response performance of the lift force produced by the variable-pitch propeller can be greatly improved by using a cascade compensation scheme. Furthermore, the direct lift-based flight control strategy is presented, which can significantly contribute to the improvement of the flight performance, precisely because the roll, pitch, yaw and vertical channels of the variable-pitch quadrotor are approximately linearized and completely decoupled from each other in this case. The experimental results demonstrate that both the endurance performance and the positioning accuracy of the variable-pitch quadrotor are improved simultaneously by using the proposed method with minimum power consumption.

Analysis of car-following model with cascade compensation strategy

Cascade compensation mechanism was designed to improve the dynamical performance of traffic flow system. Two compensation methods were used to study unit step response in time domain and frequency characteristics with different parameters. The overshoot and phase margins are proportional to the compensation parameter in an underdamped condition. Through the comparison we choose the phase-lead compensation method as the main strategy in suppressing the traffic jam. The simulations were conducted under two boundary conditions to verify the validity of the compensator. The conclusion can be drawn that the stability of the system is strengthened with increased phase-lead compensation parameter. Moreover, the numerical simulation results are in good agreement with analytical results.

Suppression of resonance in hard disk drive servo system with feedback resonant controller: a benchmark model study

In order to achieve the precision desired, the bandwidth of the read-write head positioning servomechanism of hard disk drive (HDD) is required to be very high to minimise the effects of external disturbances. However, any attempt to increase the bandwidth is hindered by increased gain in frequencies of mechanical resonances leading to oscillatory response. If not compensated properly, excessive or unbounded oscillation may even lead to instability. Cascade compensation is the popular method for compensating multiple resonant modes. However, this method requires a very precisely identified plant model. On the contrary, feedback controller works better in such situation which does not require a very accurate plant model. This paper presents a feedback resonant controller designed in a simple way to suppress the resonant modes of voice coil motor (VCM) actuator used in HDD servo system. Simulation results substantiate the effectiveness of the proposed design methodology.

Experiment Research on Control Method and Mathematic Models during Energy Storage to the Double Function Flywheel System

The mathematical models of the double function flywheel system were built based on experimental tests and theoretical analysis in the course of energy storage and attitude control. Due to significant changes of the system model parameters in the experiment, the difference between the up and down flywheel-electrical machinery unit are compensated through the cascade compensation, and then the PID compound control algorithm with integral separation and formula partition is put forward. Experiments show that overshoot is restrained effectively and stable control is realized in high speed and wide range synchronously. The angel of the platform can be stabilized within 1°, namely the attitude affection should be controlled less than 1.2′ according to the flywheels in satellite.

Cascade Compensation Algorithm for Strapdown Inertial Navigation System

The cascade compensation algorithm for no damp strapdown inertial navigation system (SINS) is designed based on control model and error characteristic of SINS level-loop. According to stability and frequency characteristic analysis for SINS level-loop, a compensation network, which is chosen to alter either the roots location or the frequency response of the system, is cascaded with the SINS level-loop to damp the oscillatory or accumulated errors. The network parameters are attained by designing the frequency characteristic using frequency domain performance indexes, which are transformed from the expected time domain indexes. The algorithm implementation of the compensator is competed by solving the first-order differential equations set, which is derived from Laplace transform of the compensation network using intermediate variables. Results of digital simulation and test on sea proved that the system attitude accuracy improved 1 order and the system position accuracy improved 1 time when the compensation network was cascaded into SINS.

PSO-based robust H.INF. controller design using cascade compensation network

This paper proposes a method for robust controller design using cascade compensation network. The method uses particle swarm optimization (PSO) to tune the controller and performance weighting function parameters by minimizing a cost function subject to H∞-norm specifications. Levy's curve fitting method is used to accurately express the multiplicative uncertainty function. The proposed method is applied to pneumatic servo actuator with system uncertainty and wide range of load variations as an example to illustrate the design procedure of the proposed controller. It is shown that the proposed controller presents robustness over a wide range of parameters change. A comparison with conventional H∞ controller is presented.

PERFORMANCE IMPROVEMENT OF POWER SYSTEM STABILIZERS USING PRONY ANALYSIS

The Prony technique is used to improve the performance of power system stabilizers (PSS). A method for evaluating the performance of the PSS is discussed. This method also helps in identifying the dominant modes. Two methods for improving PSS performance are discussed: (i) retuning the complete PSS and (ii) adding an additional phase compensator in cascade with an existing PSS to improve damping of specific modes. The latter method is chosen because of its inherent advantages. The proposed method is tested on two systems namely, a 2-area system and the WSCC 3-machine system.

Decentralized control of a kinetically controlled ideal reactive distillation column

Two-point and three-point temperature control structures are proposed for a kinetically controlled ideal reactive distillation (RD) column. The control structures maintain stable column operation for large throughput changes. However, large deviations in the final product purities are seen with three-point control giving comparatively lower deviations. The large product purity deviations are due to the kinetic regime so that two temperature set-points are adjusted in a cascade arrangement to maintain the distillate and bottoms purity. The proposed two-point and three-point structures with cascade compensation of the temperature set-points effectively maintain the distillate and bottoms purity for a large throughput decrease. However, the two-point structures fail for a large throughput increase. This is because in the kinetically controlled regime, maintaining the distillate purity requires an increase in the effective reflux ratio to internally recycle the escaping reactants back into the reactive zone. The two-point structures that use the fixed reflux ratio policy thus fail as an infeasible steady state is sought. The three-point structures effectively maintain the product purities as the reflux ratio is indirectly adjusted through the manipulation of the reflux rate. The work highlights the need for understanding the interaction between the reaction and separation sections for effective RD control system design.

Lateral Control of Autonomous Electric Cars for Relocation of Public Urban Mobility Fleet

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This brief deals with lateral dynamic control of electric vehicles in an urban environment, motivated by individual public transportation issues, aimed to contribute to reduce metropolitan areas pollution. The framework in which the control strategy is developed is the so-called “look-down reference,” in which the lateral displacement is obtained from a onboard sensor, interacting with a road infrastructure. In this framework, the designed control algorithm is made up of a combined feedback– feedforward structure. The feedback action is given by three nested closed loops with cascade compensators, where the outer one is nonlinear. The feedforward action is based on the knowledge of the road curvature, corrected by the measure of the car lateral displacement. Results from experimental tests performed on an actual circuit show the effectiveness of the considered control strategy. </para>

Double loop active vibration control of pneumatic isolator with two separate chambers

A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation: (1)The low frequency resonances introduced into the system; (2)Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke; (3) Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation (MFRC) are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions: one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.

Output feedback control for nonlinearly perturbed systems via cascade compensation with logic switching

A robust output feedback tracking strategy for uncertain nonlinear systems with output measurement noise is presented by using a passivity approach. The control algorithm guarantees boundedness of all the signals in the whole closed-loop system. Tracking accuracy can be reduced to a desirable bound. A simulation example is included to demonstrate effectiveness of the proposed algorithm.

ON/OFF型セミアクティブダンパの分散型制御手法に関する研究

This paper discusses a control algorithm for a simple and robust structural control system utilizing on/off type semi-active dampers. In order to build a decentralized control algorithm based on each inter-story velocity, we designed a cascade compensation filter. The dynamic characteristics of this filter are nearly equivalent to those of an ideal signal process realized by the modal separation method. The control effects of the proposed algorithm using the filter are verified through numerical seismic response analyses using an MDOF structural model. Finally, a concept of a simple control system utilizing a semi-active oil damper is proposed. Because of the nature of the decentralized control algorithm, each device can be equipped with all the necessary control equipment such as sensors and a controller. This simple semi-active oil damper system with a built-in control circuit, a decentralized autonomous control system, has several advantages in application.

98/00377 Design of reactive current and voltage controller of static condenser

The STATic CONdenser (STATCON) is a shunt connected voltage source converter using self-commutating devices like GTOs which can be used for reactive power control. Their principle of operation is similar to that of a synchronous condenser. A typical application of a STATCON is for voltage regulation at the midpoint of a long transmission line. In this paper, a two stage structure for the control of voltage is investigated. This uses a closed loop reactive current controller whose reference is set by an outer voltage controller. For reactive current current control, the use of a PI controller and a fuzzy logic PI controller is investigated. It is found that the fuzzy logic controller overcomes the problem of oscillatory instability encountered when a conventional PI controller is used. An important observation is that the plant transfer function for voltage control (by reactive current injection) is generally of the nonminimum phase type. This precludes the use of large gains in a PI controller as there is a risk of instability of an oscillatory mode. Eigenvalue analysis using a linearized model is carried out to design a compensator in cascade with an integral controller to overcome this problem.

Design of reactive current and voltage controller of static condenser

The STATic CONdenser (STATCON) is a shunt connected voltage source converter using self-commutating devices like GTOs which can be used for reactive power control. Their principle of operation is similar to that of a synchronous condenser. A typical application of a STATCON is for voltage regulation at the midpoint of a long transmission line. In this paper, a two stage structure for the control of voltage is investigated. This uses a closed loop reactive current controller whose reference is set by an outer voltage controller. For reactive current current control, the use of a PI controller and a fuzzy logic PI controller is investigated. It is found that the fuzzy logic controller overcomes the problem of oscillatory instability encountered when a conventional PI controller is used. An important observation is that the plant transfer function for voltage control (by reactive current injection) is generally of the nonminimum phase type. This precludes the use of large gains in a PI controller as there is a risk of instability of an oscillatory mode. Eigenvalue analysis using a linearized model is carried out to design a compensator in cascade with an integral controller to overcome this problem.

Control of multi-axis robots with elastic joints via cascade compensation using the method of exact linearization

This paper presents a new method for the position control of industrial robots with elastic joints and where the dynamic of each actuator is described by a simplified model. The inverse dynamic of the system is computed and used to compensate the nonlinear terms and decouple the system through a coordinate transformation and nonlinear feedback (exact linearization). To simplify the algorithm for the inverse dynamic and hence reduce its computation, each actuator-link pair of the robot is considered as a 2-input 2-output nonlinear system, a link subsystem and an actuator subsystem. A cascade compensation using the exact linearization is then applied to each subsystem, thereby avoiding the computation of the first and second partial derivatives of the inverse of the inertia matrix and the vector of the coriolis and centrifugal forces. This gives a formalism that is relatively simple and efficient for symbolical computation, which is very important for the maintenance of accuracy. Similarly, a cascade linear controller is constructed for each subsystem of the resulting linear decoupled 2-input 2-output system. The basis vector functions for the coordinate transformation are so chosen that only one state of the link subsystem can theoretically not be measured directly or indirectly. To estimate this state, an observer with linear error dynamic is constructed. The applicability of this observer to this general case is also proved. Simulation results using the first three links of Puma 560 are finally presented.