Inherent nonlinearities like Dead-band, stiction, and hysteresis in control valves degenerate plant performance. valve stiction standouts as a more widely recognized reason for poor execution in control loops. Measurement of valve stiction is essential to maintain scheduling. For industrial scenarios, loss of execution due to nonlinearity in control valves is an imperative issue that should be tackled. Thus, an intelligent technique is required for automated execution, observation, and enhancement. The paper shows the creative utilization of an intelligent controller for nonlinearity diagnosis in control valves. This is a Fuzzy Gain Scheduling (FGS) PID smart controller that tunes its gain parameters in real time to manage a control valve’ s inherent nonlinearities. The viability of the FGS PID controller is experimentally verified in a laboratory scale plant. An execution comparison between FGS PID and classical PID controllers are undertaken for their setpoint following and disturbance rejection at different operating points. Experimental results show that the FGS PID controller outperforms the classical PID controller for all explored cases effectively managing stiction based oscillation in the controller output.

Under a constant loading condition, use of a controller with constant coefficients can be acceptable for servo Pneumatic systems. However, in variable loads with widespread changes, more advanced control methods should be considered to achieve desirable performance. In this paper, an adaptive controller is designed and implemented to a variably loaded servo Pneumatic system with PWM driven switching valve. In the experimental setup, a Pneumatic circuit is used which consists of one PWM driven fast switching valve instead of an expensive servo or proportional valve. In the designed adaptive controller, real time identification of system parameters is performed using input-output data and controller parameters are adjusted instantaneously. “Self-tuning regulators” algorithm in which the desired closed loop poles and zeroes are predefined, is applied to design the proposed controller. The designed controller is applied to the Pneumatic actuator via an interface board and its results are compared to results of a PD and a multi model controller. Unlike the proposed method which varies the control parameters continuously according to load variations, in multi-model method the control law is selected among a number of fixed controllers. Experimental results demonstrate the high performance of the adaptive controller under variable loads.

In this paper, two position controllers have been developed for a double-acting Pneumatic cylinder with two 3/2 on/off solenoid valves, using PWM method. The first one is a PID controller, whose gains have been obtained by Zighler-Nicoltz method. The second one - a Sliding Mode controller (SMC) - has been designed based on a specific mathematical model, where an appropriate PWM method has been applied to overcome non-linearity’s such as time delay, during opening or closing of valves, and dead band due to station. The results of experimental tests on the closed loop system with the PID controller illustrate that the PWM method is suitable for servo control purposes with high accuracy. Furthermore, high accuracy was also achieved in experimental results in response to step inputs. Small values of maximum and Root Mean Square (RMS) positioning errors in response to sinusoidal inputs with various frequencies show better accuracy of SMC controller in comparison with the PID one. Good performance of the developed SMC is even more evident as frequency increases. These results also show considerable improvements in accuracy in comparison with the results of previous works on costly proportional valves.

This article focuses on the design, manufacturing, and dynamic modeling of a piezoelectric Pneumatic servo valve based on a compliant mechanism. The use of piezoelectric actuators in these valves, due to their fast dynamic response and high precision, significantly improves the speed of pressure control. To this end, the structure of the Pneumatic servo valve and the function of its components were initially investigated. To enhance the valve's orifice opening, a rhombus type compliant mechanism was designed to amplify the displacement range of the piezoelectric actuator. Subsequently, a comprehensive dynamic model of the system was presented. After identification and validating the proposed dynamics, the results of air pressure control for both steady and time-varying reference inputs were provided. Experimental results indicate that the proposed dynamic model for the manufactured valve has a maximum error of 25%. Additionally, frequency analysis results show that the valve has a dynamic bandwidth of 90 Hz and a natural frequency of 56 Hz, highlighting its applicability for high-frequency operations. The results of pressure control demonstrate a step response time of approximately 21 milliseconds at a pressure of 2 bar, indicating its capability to respond to rapid pressure changes. Furthermore, the ability to track input pressures with varying frequencies and amplitudes was also evaluated

Many industries including power-plants, refineries and so on are using high pressure control valves. Many of these valves have traditional geometries like butterfly valves. Unfortunately, because of the special design of these valves, cavitation causes very rapid corrosion. In the last decade, a next generation of control valves have been introduced which are designed to prevent cavitation. Because of the special fluid paths in the Labyrinth valves, the pressure drop is very graduated which prevents cavitation. In this article, the geometry of fluid path is optimized using Taguchi method. To this end, four parameters are considered including path's height, number of corners, corner radii and input area. For each parameter three levels are assumed and using a standard Taguchi array the optimum geometry is predicted. Then the pressure drop in optimum geometry is simulated using finite element method and the results validated the optimized geometry.

Knowing different kinds of structural systems is among the necessities and prime needs for students, architects and civil engineers. The variety of structural designs and construction methods, and access to the new technologies could help architects to create modern as wall as beneficial buildings. One of the most special types of structures, which is suitable for constructing temporary buildings (that must be built as fast as possible), is Pneumatic structures. After designing and building such structures, they could be easily transferred to different places and immediately aired. Therefore, they can be used many times in several cases. The most familiar inflated membrane structures are airships, from non-rigid blimps to giant vessels such as the proposed 1, 300-foot-long (307-meter) ATC SkyCat cargo lifter with a payload of 2, 200 tons. The new technology had consequences in the building industry. The English aeronautical engineer, Frederick W. Lanchester, first proposed an air-supported structure in 1917. Immediately after the World War II, Walter Bird designed and built prototypes of Pneumatic domes to house large radar antennae for the U.S. Air Force, known as radomes. They included many civilian commercial applications and paved the way for a new kind of architecture. Pneumatic or air-supported structures have their form sustained by creating, with the aid of fans, an air pressure differential between the interior of the building and outside atmospheric conditions. The increased air pressure-about the difference between the lobby of high-rise building and the top floor-is as slight as to be virtually undetectable and the causes are no discomfort. The structural system enables achieving large spans without columns and beams, providing totally flexible interior spaces. Made from laminated membranes such as fiber glass, nylon, or polyester, coated with polyvinyl chloride (PVC) for weather protection, the electronically welded components are tailored to define the building shapes. The durability and heat -and light- filtering properties of the membrane are determined by careful choice of surface finishes and inner lining. Because of its lightness, the air-supported structure in among the most efficient structural forms, combining high-tensile strength materials with the shell form. In this article, the authors intend to discuss the different capabilities and forms of the two categories Compact Air Structures: Air-supported structures; and Air-Inflated ones. The loads which affect these structures are: dead live and air pressure loads, which will be discussed thoroughly, and the construction methods of these structures have been stated. In other parts, “entrances”, “pressure drop control “, “expenses through operation period” and “designing relying points and supports” have been explained. Air-inflated structures are devised into major groups of inflated panel structures and inflated frame structures. In the structural-seismic part of the article, the different types of air structures in terms of forces and geometric shapes, their strong point against earthquake and lateral forces have been discussed. At the end some real examples of these structure systems have been illustrated. The conclusion of the article includes advantages and disadvantages and usage of the air structures compare to other types of structures. All effort has been made to use different sources such as books and articles (published in this field since 70s) and the data from different companies (Iranian and non-Iranian), the professional ones in the mentioned field.

In this paper design and manufacture of an experimental setup of rehabilitation device for isokinetic exercises, using Pneumatic actuator, is presented. In isokinetic exercises, limb’ s movement must be provided at a constant speed. For this type of movements, the actuator should provide an accommodating resistance against patient effort. Therefor the main challenge is speed controller design for actuator in the presence of disturbances logged by patient. This goal is achieved by using electrical actuators at the commercial levels. But beside the high cost of this instruments, low softness of electrical actuators is the main problem of using them in rehabilitation devices. Using Pneumatic actuators decrease the final price and benefits the system by Pneumatic advantages such softness and high power to weight ratio. This requires overcoming speed control problems in presence of the considered challenges. In this research modeling and speed control of Pneumatic actuator has been studied for contraction and expansion mode of muscle. Experimental results take advantages of servo Pneumatic actuator for providing isokinetic trainings in leg rehabilitation as well.

In this paper, control position of a Pneumatic actuator with the PWM solenoid on/off valves using two different Pneumatic circuits performed. After deriving the governing dynamic equations, to investigate the circuit effect on system performance, mentioned two Pneumatic circuits are introduced. Then in order to control the position of the Pneumatic actuator, for both circuits, sliding mode and proportional-integral-derivative controllers are designed. In proceeding, optimum controller parameters are determined by genetic algorithm to achieve minimum control energy and position error. Finally, by performing simulations in Matlab Simulink, performance of designed controllers with optimal parameters is evaluated and compared in the presence of disturbance. According to the obtained results, by comparing the performance of two circuits, it is observed that the first Pneumatic circuit with two solenoid valves can track the high-frequency sine reference input better and more precisely in the presence of a nonlinear sliding mode controller. The position tracking error in low-frequency sine reference input using a classic proportional-integral-derivative controller, for a single-valve Pneumatic circuit is considerably less than that of a Pneumatic circuit of two valves. This indicates the input-output quasi linear behavior of the Pneumatic actuator in a single-valve circuit.

Nonlinear factors such as air compressibility, leakage and friction make the control of Pneumatic systems complex. Model-based robust control strategies are appropriate candidates for Pneumatic systems, however, in such controllers the measurement of state variables of the system are necessary. In a Pneumatic system the state variables are position and velocity of the actuator, and pressure in both sides of the cylinder. Pressure measurement is usually obtained by means of costly and low response sensors. A better way to deal with the measurement problem is to use observers to reconstruct the missing velocity and pressure signals. However, the problem in a Pneumatic system is that the system is not observable and pressure signals could not be observed by means of position signals only. To deal with this problem, in this paper, the Pneumatic actuator is modeled as two separate chambers and the resulting subsystems are observable independently. High gain observers are designed for the mentioned subsystems and for each chamber the pressure of the other chamber is considered as a disturbance. The input signal for each observer is the actuator position signal only. Finally, a sliding-mode control strategy is designed for position tracking and experimental results verify that both controller and observer objectives are satisfied.