This paper reports a study on the static and dynamic behavior of pneumatic actuation systems, resulting in a comprehensive view of the influence of the system parameters on the energy efficiency and dynamic performance. The operating point approach based on the steady-state analysis of a pneumatic actuation system is used for developing analytical expressions to describe the relationship between the piston diameter and the system performance, including displacement time, stroke end velocity, and energy efficiency. The validity of the proposed equations is demonstrated by comparison with results from a test rig. Sensitivity analysis using a nonlinear dynamic simulation model indicated that a specific operating region exists, where good energy efficiency and the maximum dynamic performance are achieved. Moreover, the results show that an oversized system becomes more inefficient in both energetic and dynamic aspects. The results obtained provide a very consistent foundation for developing a method for pneumatic system sizing.

This paper investigates the applicability of two state feedback controllers for a class of uniformly controllable and observable nonlinear systems. The first one is based on an appropriate high gain control principle that has been developed by duality from the high gain observer principle. The state feedback control gain is particularly provided by a synthesis function satisfying a well-defined condition, leading thereby to a unification of the high gain control designs. The second one is a backstepping controller that has been developed from a suitable combination of the backstepping control approach bearing in mind the high gain control principle pursued for the first controller design. A common engineering design feature that is worth to be mentioned consists in properly formulating their underlying control problems as a regulation problem involving a suitable reference model with respect to the structure of the system as well as the control design principle under consideration. Of fundamental interest, the involved reference model is systematically derived thanks to the flatness and backstepping principles using an appropriate Lyapunov approach. An experimental evaluation is carried out to illustrate the efficiency of the proposed nonlinear controllers.

The use of pneumatic devices is widespread among different industrial fields, in tasks like handling or assembly. Pneumatic systems are low-cost, reliable, and compact solutions. However, its use is typically restricted to simple tasks due to the poor performance achieved in applications where accurate motion control is required. One of the key elements required to achieve a good control performance is the model of the servopneumatic system. An accurate model may be of vital importance not only in the simulation steps needed to test the control strategy but also as a part of the controller itself. This work presents a new servopneumatic system model primarily developed for control tasks, namely, to predict pneumatic and friction forces in dynamic tests. The model can also be used in simulation tasks to predict the piston position and velocity. The performance on both applications is validated experimentally.

Air motors have often been utilized in industrial servo systems in the automation industry due to their advantages such as small volume, low cost, light weight, convenience of operation, and no overheating problems. Recently, the development of control technology has improved, making the requirements for control precision higher than ever before. Accurate control performance in pneumatic systems is facilitated by the implementation of nonlinear control techniques. The purpose of this study is to analyze the behavior of a biaxial pneumatic table motion system with a vane-type air motor, and to design a backstepping sliding mode controller for this system. A proportional integral derivative controller compared with this new backstepping design. The tracking circle error and tracking error of the two axes are noted. The experimental results show that accurate tracking circle trajectory performance can be achieved with the proposed controller.

This paper presents a new predictive greedy control law for the control of electropneumatic systems using solenoid valves. The method is based on a predictive model of the mass flow rate of the valves. For this strategy, a control vector, depending on the number of possible configurations for the solenoid valves, is defined. In order to evaluate the new approach, a comparison has been performed with a classical PWM control for a force tracking problem. The experimental results show that not only the accuracy in steady state but also the dynamic behavior of the pressures is better in the case of greedy control than PWM control.

Pressure reducing valve (PRV) is one of the critical components in high pressure pneumatic systems. Nowadays, manually operated PRVs have been widely used, but there is still no universal electronic PRV. Thus, we proposed a novel high pressure electronic pneumatic pressure reducing valve (EPPRV) whose inlet pressure ( p i ) is up to 31.5 MPa. The EPPRV mainly consists of a poppet structured pilot valve and a piston structured main valve. A proportional electromagnet was used as the command element, and a pressure closed loop, rather than a force closed loop controller, was designed. First, the mechanical design and functionality of the EPPRV are carefully analyzed. Then, a mathematical model is built up, and the working characteristics of pressure, flow rate, and frequency response are simulated. Finally, the test bench is introduced, and detailed experiments are carried out. Simulated and experimental results are highly consistent within output pressure ( p o ) ranging from 8 MPa to 25 MPa and load flow rate ( q ld ) ranging from 60 g/s to 650 g/s, which verifies the feasibility of the novel structure and the validity of the mathematic model.

Within the frame of industrial automation, the mechanical power related to pneumatic actuator systems involves air flows along with mechanical component, such as valves, connecting tubes, cylinder chambers and possible linkages in order to finally actuate a specific objective. Gas dynamic of the air flowing into connecting ducts plays a fundamental role in the description of the global dynamic phenomena of these systems. Several studies deal with the dynamics of such pneumatic systems but through streamlined analysis where the influence of pressure-waves propagating in ducts is neglected or poorly described. The related models are even more complex when finite volumes are placed at the ends of connecting lines. In this paper, two different mathematical models describing transient pressure-waves propagating through lines closed by finite volumes are presented. The investigation regards pressure and velocity ranges normally operating in industrial pneumatic systems. Besides the value of new system modeling of different complexity, these models are compared from an analytical and numerical point of view; advantages, disadvantages, weakness, abilities, and inabilities are highlighted and, finally, the relevant analysis is corroborated through experimental validations of wave propagating pressure at fixed positions of ducts. This study results both in the presentation of models of practical interest, as well as in an attempt to provide an elucidation on the need to resort to an accurate model rather than a streamlined one with respect to the geometric and/or operative characteristics of industrial pneumatic systems.

The gain values that can be imposed in pneumatic system controllers are bounded to the restricted actuator bandwidth. That limitation, with low damping and stiffness due to the air compressibility, seriously affects accuracy and repeatability when varying payloads or supply pressures. For modeling and control intents, a correct characterization of the pneumatic actuator natural frequency is indispensable. The aim of the paper is to evaluate how heat exchange process affects the proper characteristics of pneumatic drivers and, in particular, their pneumatic stiffness. To this purpose dynamic stiffness had been studied both by imposing in the cylinder’s chambers a polytrophic transformation of the fluid with a prefixed index and by employing energy equations. Numerical results obtained by implementing the two formulations for different working conditions are reported and compared in order to point out the ranges in which they overlap, and hence both approaches produce accurate results, or the ones in which there is a difference, and then it is necessary to consider the temperature dynamics.

An increase of the deceleration in high-speed and high-density train operations degrades riding comfort and frequently causes wheel skids. This requires an introduction of the control technology to upgrade the control performance of brake systems on railway vehicles. We are now studying control methods for a mechanical brake that uses friction and pneumatic pressure, including nonlinear elements as the basis of a brake force. Furthermore, the system itself has certain “dead time,” which is not negligible and makes control difficult. One of our targets is to develop a brake control device that can control the deceleration in accordance with a decelerating pattern that optimizes the riding comfort of trains and prevents wheel skids. In this paper, a design method of the controller for the deceleration tracking control and the system compensating the dead time are proposed. Finally, the effects of them are confirmed through computer simulations and experimental results on a dynamo test stand.

The force and position of pneumatic actuators are difficult to control, since their nonlinear model includes unknown variables such as temperature and the discharge coefficient. This paper presents a specific sliding-mode observer to estimate these unknown time-variant quantities. The stability of the estimation error is studied, and real-time results show that the proposed approach combined with a feedback linearization controller performs better than a standard sliding-mode controller.

This paper presents a control design methodology that provides a prescribed degree of stability robustness for plants characterized by discontinuous (i.e., switching) dynamics. The proposed control methodology transforms a discontinuous switching model into a linear continuous equivalent model, so that loop-shaping methods may be utilized to provide a prescribed degree of stability robustness. The approach is specifically targeted at pneumatically actuated servo systems that are controlled by solenoid valves and do not incorporate pressure sensors. Experimental demonstration of the approach validates model equivalence and demonstrates good tracking performance.

In this article we present two nonlinear force controllers based on the sliding mode control theory. For this purpose we use the detailed mathematical model of the pneumatic system developed in the first part of the paper. The first controller is based on the complete model, and exhibits superior performance both in the numerical simulation and experiments, but requires complex online computations for the control law. The second controller neglects the valve dynamics and the time delay due to connecting tubes. The performance of this controller exhibits slight degradation for configurations with relatively short tubes, and at frequencies up to 20 Hz. At higher frequencies or when long connecting tubes are used, however, the performance exhibits significant degradation compared to the one provided by the full order controller. [S0022-0434(00)00703-6]

In an effort to overcome the nonlinerities associated with a pneumatic system the variable structure control (VSC) technique has been employed to control the position of a pneumatic actuator. To accomplish this a model of a pneumatic actuator was developed to allow the control systems to be studied via simulations. The results from the simulations indicated that the VSC technique can position the actuator rapidly, via first-order trajectory, in response to a step input. An experimental study of the VSC control system was then performed. These experiments verified the simulation work, and demonstrated that inherent system delays and the quantisation of the control signals can cause and uncontrollable oscillatory behaviour; stability limits were established for three of the system parameters. It was also found, that the actuator could be placed within ±5 mm of the desired position.

Pneumatic actuators are capable of providing high power output levels at a relatively low cost. In addition, they are clean, lightweight, and can be easily serviced. The difficulty of achieving a high-bandwidth, stable, pneumatic control system has limited its use in robotic position control applications. For open-loop control applications, such as many robot grippers, pneumatic actuators are often used. In this paper, direct-drive pneumatic servo-actuators are examined for their potential use in robotic applications. A complete mathematical model of the actuator is derived, and several control algorithms are tested numerically and experimentally. Our analysis shows that pneumatic systems are practical for use in servo-control applications. The main limitation is that of the system response time, which is determined by the valve flow characteristics and supply pressure. Large output forces can be obtained and accurately controlled with the servo-valve and differential pressure transducer used in the experiments.