Controlled Freezing of Nonideal Solutions With Application to Cryosurgical Processes

1991 ◽  
Vol 113 (4) ◽  
pp. 430-437 ◽  
Author(s):  
H. M. Budman ◽  
J. Dayan ◽  
A. Shitzer
Keyword(s):  
Cooling Rate ◽  
Freezing Process ◽  
Data Sets ◽  
Tracking Accuracy ◽  
Loop Control ◽  
Set Point ◽  
New Device ◽  
Loop Control System ◽  
The Stability ◽  
Controlled Freezing

Success of a cryosurgical procedure, i.e., maximal cell destruction, requires that the cooling rate be controlled during the freezing process. Standard cryosurgical devices are not usually designed to perform the required controlled process. In this study, a new cryosurgical device was developed which facilitates the achievement of a specified cooling rate during freezing by accurately controlling the probe temperature variation with time. The new device has been experimentally tested by applying it to an aqueous solution of mashed potatoes. The temperature field in the freezing medium, whose thermal properties are similar to those of biological tissue, was measured. The cryoprobe temperature was controlled according to a desired time varying profile which was assumed to maximize necrosis. The tracking accuracy and the stability of the closed loop control system were investigated. It was found that for most of the time the tracking accuracy was excellent and the error between the measured probe temperature and the desired set point is within ±0.4°C. However, noticeable deviations from the set point occurred due to the supercooling phenomenon or due to the instability of the liquid nitrogen boiling regime in the cryoprobe. The experimental results were compared to those obtained by a finite elements program and very good agreement was obtained. The deviation between the two data sets seems to be mainly due to errors in positioning of the thermocouple junctions in the medium.

Research on INS-Aided GNSS Carrier Tracking Loop in High Dynamic Circumstance

2013 ◽  
Vol 464 ◽  
pp. 215-221
Author(s):  
Xin Long Wang ◽  
Chuan Jun Li ◽  
Xing Cheng Li
Keyword(s):  
Dynamic Environment ◽  
Coupled System ◽  
Tracking Performance ◽  
Tracking Loop ◽  
Loop Control ◽  
Closed Loop Control System ◽  
Loop Control System ◽  
Tightly Coupled ◽  
High Dynamic ◽  
The Stability

GNSS receiver will produce a large Doppler shift in high dynamic environment, thus causing lock-lose of the tracking loop. INS-aided GNSS tightly coupled system can improve tracking performance in high dynamic environment by introducing the Doppler information estimated by INS. Through analyzing by the theory of closed loop control system theory and numerical simulation of the INS-aided carrier tracking loop, the results show that INS-aided carrier tracking loop can obviously improve the stability of carrier tracking performance and anti-jamming ability of the satellite navigation receiver in high dynamic circumstance.

scholarly journals Research on Discretization PI Control Technology of Single-Phase Grid-Connected Inverter with LCL Filter

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
Jianke Li ◽  
Jinquan Wang ◽  
Ye Xu ◽  
Jianting Li ◽  
Jingjing Chen ◽  
...  
Keyword(s):  
Dynamic Performance ◽  
Numerical Algorithms ◽  
Switching Frequency ◽  
Lcl Filter ◽  
Loop Control ◽  
Closed Loop Control System ◽  
Loop Control System ◽  
Grid Connected Inverter ◽  
The Stability ◽  
The Cost

Compared with L-type filter, LCL-type filter is more suitable for high-power low-switching frequency applications with reducing the inductance, improving dynamic performance. However, the parameter design for the LCL filter is more complex due to the influence of the controller response performance of the converter. If the harmonic current around switching frequency can be fully suppressed, it is possible for inverter to decrease the total inductance as well as the size and the cost. In this paper, the model of the LCL filter is analyzed and numerical algorithms are adopted to analyze the stability of the closed-loop control system and stable regions are deduced with different parameters of LCL filter. Then, the minimum sampling frequencies are deduced with different conditions. Simulation and experimental results are provided to validate the research on the generating mechanism for the unstable region of sampling frequency.

Fuzzy Adaptive Controller for Uncertain Multivariable Nonlinear Systems with Both Sector Nonlinearities and Dead-Zones

2015 ◽  
pp. 334-363
Author(s):  
Abdesselem Boulkroune
Keyword(s):  
Nonlinear Systems ◽  
Positive Definite ◽  
Loop Control ◽  
Dead Zones ◽  
Gain Matrix ◽  
Control Gain ◽  
Loop Control System ◽  
The Stability ◽  
Sector Nonlinearities ◽  
Fuzzy Adaptive

This chapter presents two fuzzy adaptive variable structure controllers for a class of uncertain multi-input multi-output nonlinear systems with actuator nonlinearities (i.e. with sector nonlinearities and dead-zones). The design of the first controller concerns systems with symmetric and positive definite control-gain matrix, while the design of the second one is extended to the case of non-symmetric control-gain matrix thanks to an appropriate matrix decomposition, namely the product of a symmetric positive-definite matrix, a diagonal matrix with diagonal entries +1 or -1, and a unity upper triangular matrix. An appropriate adaptive fuzzy-logic system is used to reasonably approximate the uncertain functions. A Lyapunov approach is adopted to derive the parameter adaptation laws and prove the stability of the closed-loop control system. Finally, some simulation results are carried out to show the effectiveness of the proposed controllers.

scholarly journals The research of the pulse oxygen supply based on the fuzzy control technology

2018 ◽  
Vol 189 ◽  
pp. 06012
Author(s):  
Faling Hu ◽  
Tongfeng Niu ◽  
Jun Yao ◽  
Bingyan Cui ◽  
Haoxing Xu ◽  
...  
Keyword(s):  
Control System ◽  
Fuzzy Control ◽  
Open Loop ◽  
Open Loop Control ◽  
Loop Control ◽  
Fuzzy Control System ◽  
Loop Control System ◽  
Working Principle ◽  
The Stability ◽  
Close Loop Control

According to the working principle of pulse oxygen supplies, we analyze how to realize the control of the oxygen flow by double different valves. a two-dimensional fuzzy control system is proposed to solve the unstable problem, which is brought by the shortcomings of the open-loop control system. We add a new parameter, the rate of the differential pressure signal changes, which contributes to a close –loop control system and increases the stability of the system. The experiments and the data show that the fuzzy control system make the process of breathing much more comfortable and solve the hysteresis and overshoot caused by the open-loop control system. The product reliability has been greatly improved.

The role of walking surface in enhancing the stability of the simplest passive dynamic biped

Robotica ◽  
2014 ◽  
Vol 33 (1) ◽  
pp. 195-207 ◽  
Author(s):  
Ali Tehrani Safa ◽  
Mahyar Naraghi
Keyword(s):  
Gait Stability ◽  
Loop Control ◽  
Contact Points ◽  
Closed Loop Control System ◽  
Bipedal Gait ◽  
Loop Control System ◽  
The Stability ◽  
Straight Lines ◽  
Inclined Surface

SUMMARYEmploying passive dynamics of the simplest point-foot walker, we have shown that the walking surface could have a great role in promoting the gait stability. In this regard, the stabilization of the simplest walking model,3 between the range of slopes greater than 0.0151 rad. and less than 0.26 rad., has been achieved. The walker like other passive dynamic walking models has no open or closed-loop control system; so, is only actuated by the gravity field. Moreover, no damper or spring is used. Obviously, according to the model's unstable behavior, it is unable to walk on an even flat ramp between the mentioned intervals.3 Here, instead of restraining the model, we let it explore other smooth surfaces, walking on which, will end in an equally inclined surface. To reach the objective, we employ a parallel series of fixed straight lines (local slopes) passing through contact points of an unstable cycling gait, which is generated by an ordinary ramp. To categorize, we have nicknamed those local slopes that guide the biped to a stable cyclic walking, “Ground Attractors,” and the other, leading it to a fall, “Repulsive Directions.” Our results reveal that for the slope <0.26 rad., a closed interval of ground attractors could be found. Stabilization of those unstable limit cycles by this technique makes obvious the key role of walking surface on bipedal gait. Furthermore, following our previous work,13 the results confirm that the two thoroughly similar walking trajectories can have different stability. All of these results strongly demonstrate that without considering the effects of a walking surface, we cannot establish any explicit relationship between the walker's speed and its stability.

Application of Back-to-Back Circuit in the Intelligent Wheelchair Charging Technology

2014 ◽  
Vol 631-632 ◽  
pp. 654-659
Author(s):  
Li Wang ◽  
Rong Yang ◽  
Xiu Feng Zhang ◽  
Yan Ma
Keyword(s):  
Design Method ◽  
Voltage Source ◽  
Super Capacitor ◽  
Loop Control ◽  
Intelligent Wheelchair ◽  
Closed Loop Control System ◽  
Loop Control System ◽  
Pwm Rectifiers ◽  
Bus Voltage ◽  
The Stability

Intelligent wheelchair charging technology put forward a very high request to the stability of the DC bus voltage. This paper describes the three phase principles and topology with Back-to-Back, SVPWM is used to the voltage-source PWM rectifiers, the principle of voltage and current double closed loop control system design the system. According to the principle of super-capacitor store energy for the load and construct their simulation model with SIMULINK. Simulation results demonstrate the feasibility of the above design method.

Fuzzy Adaptive Controller for Uncertain Multivariable Nonlinear Systems with Both Sector Nonlinearities and Dead-Zones

2017 ◽  
pp. 1127-1155
Author(s):  
Abdesselem Boulkroune
Keyword(s):  
Nonlinear Systems ◽  
Positive Definite ◽  
Loop Control ◽  
Dead Zones ◽  
Gain Matrix ◽  
Control Gain ◽  
Loop Control System ◽  
The Stability ◽  
Sector Nonlinearities ◽  
Fuzzy Adaptive

This chapter presents two fuzzy adaptive variable structure controllers for a class of uncertain multi-input multi-output nonlinear systems with actuator nonlinearities (i.e. with sector nonlinearities and dead-zones). The design of the first controller concerns systems with symmetric and positive definite control-gain matrix, while the design of the second one is extended to the case of non-symmetric control-gain matrix thanks to an appropriate matrix decomposition, namely the product of a symmetric positive-definite matrix, a diagonal matrix with diagonal entries +1 or -1, and a unity upper triangular matrix. An appropriate adaptive fuzzy-logic system is used to reasonably approximate the uncertain functions. A Lyapunov approach is adopted to derive the parameter adaptation laws and prove the stability of the closed-loop control system. Finally, some simulation results are carried out to show the effectiveness of the proposed controllers.

Robust Control Techniques Applied to the Hot-Dip Galvanizing Process

2013 ◽  
Vol 459 ◽  
pp. 212-221 ◽  
Author(s):  
G. Romero ◽  
A. Palacios ◽  
J. Rivera ◽  
I. Pérez ◽  
D. Lara ◽  
...  
Keyword(s):  
Control System ◽  
Time Delay ◽  
Stability Property ◽  
Steel Strip ◽  
Property A ◽  
Hurwitz Matrix ◽  
Loop Control ◽  
Loop Control System ◽  
The Stability ◽  
Close Loop Control

This paper presents new results to compute the time-delay margin of the hot-dip galvanizing control system. Compared to previous works on this issue, this paper considers a mathematical model of the plant with two inputs and one output. The inputs are used to regulate the output, which represents the Zinc mass coating of steel strip. To achieve this objective, a multivariable PI controller is used, this controller is tuned applying the well known Ziegler and Nichols method, and then the maximum time-delay is computed in order to guarantee the stability property of the close loop control system. The work bases its results on a transformation of the time-delay operator and it is performed in order to get a two variable polynomial; after this, to obtain the robust stability property, a result based on the Hurwitz matrix is applied.

New approach to control of robotic manipulators interacting with dynamic environment

Robotica ◽  
1996 ◽  
Vol 14 (1) ◽  
pp. 31-39 ◽  
Author(s):  
Miomir K. Vukobratović ◽  
Yuri Ekalo
Keyword(s):  
Dynamic Environment ◽  
Interaction Force ◽  
Robot Motion ◽  
Control Procedure ◽  
Control Laws ◽  
Loop Control ◽  
Closed Loop Control System ◽  
Control Concept ◽  
Loop Control System ◽  
The Stability

SummaryThe fundamentals of an approach to solving the control task of robots interaction with a dynamic environment based on the stability of a closed-loop control system are given in this paper. The task is set and solved in its general form. The traditional control concept of compliant robot motion—the hybrid position/force control is discussed. In the paper the proposed control laws ensure simultaneous stabilization of both the desired robot motion and the desired interaction force, as well as their required quality of transient responses. In order to emphasize the fundamental point of this approach in controlling the contact tasks in robotics, the authors have assumed ideal parameters of interacting dynamic systems. The proposed control procedure is demonstrated by one simple example.

scholarly journals Adaptive Barrier Control for Nonlinear Servomechanisms with Friction Compensation

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Shubo Wang ◽  
Haisheng Yu ◽  
Xuehui Gao ◽  
Na Wang
Keyword(s):  
Control Method ◽  
Design Procedure ◽  
Lyapunov Stability Theory ◽  
Friction Compensation ◽  
Loop Control ◽  
Closed Loop Control System ◽  
Full State ◽  
Loop Control System ◽  
The Stability ◽  
The Given

This paper proposes an adaptive barrier controller for servomechanisms with friction compensation. A modified LuGre model is used to capture friction dynamics of servomechanisms. This model is incorporated into an augmented neural network (NN) to account for the unknown nonlinearities. Moreover, a barrier Lyapunov function (BLF) is utilized to each step in a backstepping design procedure. Then, a novel adaptive control method is well suggested to ensure that the full-state constraints are within the given boundary. The stability of the closed-loop control system is proved using Lyapunov stability theory. Comparative experiments on a turntable servomechanism confirm the effectiveness of the devised control method.

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