Pneumatic Servo Research Articles

Model-based and model-free position control of a servo pneumatic system in the presence of uncertainties and disturbances

Trajectory tracking in electro-pneumatic systems poses a significant challenge due to the nonlinearity of their dynamics. This research aims to analyze the performance of various types of controllers for a laboratory-scale pneumatic system in terms of energy consumption and control efforts. By considering the mathematical relationships among system components, a precise gray-box mathematical model is developed based on experimental data. Subsequently, different linear model-free and nonlinear model-based controllers, is designed and their performances are compared by measuring tracking error, control effort, maximum overshoot, settling time, robustness against disturbances, and energy efficiency in the presence of severe disturbances. The effectiveness of these control methods is assessed through experimental tests and compared.

Modelling and Transmission Characteristics Analysis of APU Pneumatic Servo System

The auxiliary power unit (APU), which is a compact gas turbine engine, is employed to provide a stable compressed air supply to the aircraft. This compressed air is introduced into the various aircraft components via the pneumatic servo system, thereby ensuring the normal operation of the aircraft’s systems. The objective of this study is to examine the impact of parameter variation on the transmission characteristics of an APU pneumatic servo system, with a particular focus on the aerodynamic moment associated with the operating process of a butterfly valve. To this end, a mathematical model of the pneumatic servo system has been developed. The accuracy of the mathematical model was verified by means of numerical simulation and comparative analysis of experiments. The simulation model was established in the Matlab/Simulink environment. Furthermore, the effects of throttling area ratio, fixed throttling hole diameter, rodless chamber volume of actuator cylinder and gas supply temperature on the transmission characteristics of the system were discussed in greater detail. The findings of the research indicate that the throttle area ratio is insufficiently sized, which results in a deterioration of the system’s linearity. Conversely, an excessively large throttle area ratio leads to a reduction in the controllable range of the load axis and is therefore detrimental to the servo mechanism of the flow control. An increase in the diameter of the fixed throttling hole or a decrease in the volume of the rodless cavity of the actuator cylinder facilitates a rapid change in flow rate within the rodless cavity and an increase in the response speed of the load-rotating shaft of the servomechanism. An increase in the temperature of the gas supply from 30 °C to 230 °C results in a reduction in the response time of the system by a mere 0.2 s, which has a negligible impact on the transmission characteristics of the system.

Precision polishing force control technology of abrasive belt-wheel polishing servo control system based on HGO-SMC

Due to cylinder friction, valve dead zone effect, flow nonlinearity, and measurement noise exist in pneumatic system. In the actual machining, it is difficult to achieve precise control of the pneumatic servo polishing system using the traditional PID algorithm, so the machining accuracy of the blades cannot be guaranteed. A sliding mode control (SMC) method based on high gain observer (HGO) is proposed. The HGO observes the output signal of the system and feeds the estimated signal back to the SMC to ensure that the observation error is uniform ultimate boundedness. Simulation and experiments show that compared with the PID algorithm, the steady-state error of HGO-SMC can be reduced by 66.4%. Compared with SMC(sgn), the high-frequency chattering of HGO-SMC can be reduced by 72.5%. Moreover, the polishing processing experiment shows that HGO-SMC can improve the form and position accuracy by 52.6% and reduce the surface roughness by 55.6%, compared with the original PID control algorithm of the polishing machine tool.

Position Tracking Control for Pneumatic Servo System Subject to State Constraints and Voltage Saturation

Position Tracking Control for Pneumatic Servo System Subject to State Constraints and Voltage Saturation

Pneumatic servo position control optimization using adaptive-domain prescribed performance control with evolutionary mating algorithm

Pneumatic servo systems face challenges such as friction, compressibility, and nonlinear dynamics, necessitating advanced control techniques. Research suggests model-based, model-free, hybrid, and optimization-based methods have their strengths. Therefore, this study presents an optimal control strategy using Adaptive Domain Prescribed Performance Control (AD-PPC) cascaded with PID and optimized using the Evolutionary Mating Algorithm (EMA) for a pneumatic servo system (PSS). The goal is to achieve faster transient control and stable rod-piston positioning with minimal friction through the hysteresis phenomenon of the targeted proportional valve-controlled double-acting pneumatic cylinder (PPVDC) representing the PSS. The novel EMA optimizes the cascaded controller based on the tracking error as its objective function. Simulation studies verify the proposed AD-PPC-PID controller with the PPVDC model plant, iteratively optimized by the EMA. The analytical study compares this setup's control system and optimization model with the same control system model using alternative optimization methods. The testing employs step and multi-step signals for PPVDC's rod-piston position input. Results show that the EMA-tuned AD-PPC-PID outperforms AD-PPC-PID controller with other optimizers. For both input trajectory tests, EMA-tuned AD-PPC-PID shows faster response times, with average improvements of 30 % in settling times and 70 % in tracking performance metrics compared to other optimizers, making it robust for nonlinear system applications like PPVDC rod-piston positioning.

Active Disturbance-Rejection Controller (ADRC)-Based Torque Control for a Pneumatic Rotary Actuator with Positional Interference

The compressibility of air, the uncertainty of dynamic models, and the existence of friction make pneumatic servo systems exhibit strong nonlinearity. Furthermore, the confluence of pneumatic-system nonlinearity and interference from the position system induces oscillations within the system, thereby posing a formidable challenge for achieving precise torque control. This study ensures precise torque control in a pneumatic actuator amid interference from the position system and proposes a novel active disturbance-rejection controller integrated with a Kalman filter. Firstly, in response to the oscillation stemming from the inherent nonlinearity of the pneumatic system and interference from the position system, this paper designs an active disturbance-rejection controller (ADRC) with robust anti-interference capabilities aimed at mitigating system oscillations. Secondly, to address the issue of sensor noise interfering with the ADRC and causing system oscillation, a first-order Kalman filter is designed to provide real-time and more accurate state estimation, effectively reducing oscillations and improving the robustness of the system. Finally, using the Lyapunov stability theory, the effectiveness of both the nonlinear extended observer and the convergence of the nonlinear error-state controller in the ADRC is proven. Experimental results indicate that the proposed controller reduces system oscillations and improves control accuracy.

Fundamental Study on Force-Projecting Bilateral Control for Pneumatically Driven Follower Device

This paper proposes the application of force-projecting bilateral control to a master-follower teleoperation system with pneumatic drive on the follower side and evaluates its effectiveness. The proposed method directly projects the operating force on the master side to the driving force on the follower side, eliminating the need for both position control and external force detection on the follower side, thereby solving the problem of low rigidity and response delay of a pneumatic servo system and providing highly stable sensor-less force presentation against variable environments. In this study, dynamic response analyses of a 1-DOF master-follower system were performed by numerical simulation using a linear system model, followed by experimental verification by implementing an actual system with an external force estimator. The results showed that the proposed force-projecting bilateral control has significantly higher positioning rigidity and better force control stability than the conventional force-reflecting bilateral control. A theoretical consideration was also given using the equivalent transformation of force transfer functions to provide evidence of high stability.

Trajectory Tracking Control of Pneumatic Servo System: A Variable Gain ADRC Approach.

In this article, a novel error-driven variable gain active disturbance rejection control (ADRC) approach is developed for pneumatic servo system, and the desired performance of trajectory tracking and the disturbance rejection can be guaranteed. The proposed variable gain ADRC includes three parts: 1) variable gain tracking differentiator (TD); 2) variable gain extended state observer (ESO); and 3) variable gain error feedback controller (EFC). The proposed variable gain TD is noise tolerant and possesses a variable gain, which can be dynamically adjusted according to the tracking error, and the performance for tracking the reference signal and extracting its derivative is improved. The variable gain ESO is also equipped with a variable gain driven by estimation errors to improve the estimation performance. Then, the variable gain EFC is further designed to improve control accuracy. Finally, simulations and experimental results are presented to verify the efficiency of the proposed methods.

Development, modeling, and control of a syringe-based picoliter-scale microinjection system

Microinjection, which is widely employed in modern biology and medicine research, is a crucial method for transferring biomaterial in a single cell. Despite substantial research into microinjection automation technology, how to achieve high precision, which is crucial for quantitative analysis, has gotten scant attention. This paper offers a dual-loop control syringe-based picoliter-scale injection system, with the inner being a pneumatic servo loop with a baroreceptor providing pressure feedback and the outside being a position servo loop with a microscope providing visual feedback. Specifically, significant crawling phenomenon are found throughout the characteristic test trial, rendering the gas-liquid interface uncontrollable. To mathematically characterize this phenomenon, a theoretical model is developed that accounts for static friction, capillary force, capillary cone angle, and fluid viscous force. The genetic algorithm is used to identify difficult-to-measure and calibrate parameters. Based on the established model, an integral sliding-mode controller (ISMC) with saturation function and a PID controller for the inside loop control were established, both of which have a fast convergence rate and do not overshoot. Finally, experimentation is used to validate the designed cell injection system, demonstrating that the suggested system can regulate the smallest droplet in the tip of the needle to within 0.25 pL.

Implementing a Precision Pneumatic Plug Tray Seeder with High Seeding Rates for Brassicaceae Seeds via Real-Time Trajectory Tracking Control

In recent years, the aging of the rural population worldwide has become a major concern, necessitating the development of agricultural automation. Pneumatic energy has emerged as a reliable and environmentally friendly option, aiding in the global effort to reduce carbon emissions. The purpose of this study is to reduce the amount of labor required for plug tray seeding by developing an automated seeder that employs a precision pneumatic servo system via the rod-less actuator with real-time trajectory tracking capabilities. The proposed seeder has a simple structure, is easy to maintain, and saves energy. It mainly consists of a rod-less pneumatic cylinder, a needle seeding mechanism, a soil drilling mechanism and a PC-based real-time controller. Mathematical models of the developed precision pneumatic plug tray seeder are analyzed and established, and an adaptive sliding mode controller is proposed. A PC-based real-time control system is developed using MATLAB/SIMULINK via an optical encoder with a sampling frequency of 1 kHz to enable the development of precise pneumatic plug tray seeder. An optical encoder is used to measure the displacement of the rod-less cylinder which represents real-time positions of the plug tray loading platform. Experiments are conducted using Brassicaceae seeds, and the rates of single seeding, multiple seeding, missed seeding and germination are carried out through manual measurement. The results indicate that the seeder exhibits satisfactory performance, with a root mean square error of less than 0.5 mm and a single-seeding rate of more than 97%. Overall, our findings provide new insights for nurseries and could contribute to the reduction in agricultural carbon emissions.

Design and Additive Manufacturing of a Continuous Servo Pneumatic Actuator.

Despite an emerging interest in soft and rigid pneumatic lightweight robots, the pneumatic rotary actuators available to date either are unsuitable for servo pneumatic applications or provide a limited angular range. This study describes the functional principle, design, and manufacturing of a servo pneumatic rotary actuator that is suitable for continuous rotary motion and positioning. It contains nine radially arranged linear bellows actuators with rollers that push forward a cam profile. Proportional valves and a rotary encoder are used to control the bellows pressures in relation to the rotation angle. Introducing freely programmable servo pneumatic commutation increases versatility and allows the number of mechanical components to be reduced in comparison to state-of-the-art designs. The actuator presented is designed to be manufacturable using a combination of standard components, selective laser sintering, elastomer molding with novel multi-part cores and basic tools. Having a diameter of 110 mm and a width of 41 mm, our prototype weighs less than 500 g, produces a torque of 0.53 Nm at 1 bar pressure and a static positioning accuracy of 0.31° with no limit of angular motion. By providing a description of design, basic kinematic equations, manufacturing techniques, and a proof of concept, we enable the reader to envision and explore future applications.

Optimal Pneumatic Actuator Positioning and Dynamic Stability using Prescribed Performance Control with Particle Swarm Optimization: A Simulation Study

This paper introduces an optimal control strategy for pneumatic servo systems (PSS) positioning using Finite-time Prescribed Performance Control (FT-PPC) with Particle Swarm Optimization (PSO). Pneumatic servo systems are widely used in industrial automation, as well as medical and cybernetics systems that involve robotics applications. Precision in pneumatic control is crucial not only for the sake of efficiency but also safety. The primary goal of the proposed control strategy is to optimize the convergence rate and finite time of the prescribed performance function in error transformation of the FT-PPC, as well as the Proportional, Integral and Derivative (PID) controller as the inner-loop controller for this system. The study utilizes a dynamic model of a pneumatic proportional valve with a double-acting cylinder (PPVDC) as the targeted plant and performs simulations with a multi-step input trajectory. This offline tuning method is essential for such nonlinear systems to be safely optimized, avoiding major damage to the real-time fine-tuned works on the controller. The results demonstrate that the proposed control strategy surpasses the performance of FT-PPC with a PID controller alone, significantly improving the system's performance, including suppressing overshoot and oscillation in the responses. Further validation through the actual system of PPVDC using the fine-tuned values of FT-PPC and PID with PSO is a future task and more challenging to come, as hardware constraints may vary with different environments such as temperatures.

Review of Compressed Air Receiver Tanks for Improved Energy Efficiency of Various Pneumatic Systems

This review examines compressed air receiver tanks (CARTs) for the improved energy efficiency of various pneumatic systems such as compressed air systems (CAS), compressed air energy storage systems (CAESs), pneumatic propulsion systems (PPSs), pneumatic drive systems (PDSs), pneumatic servo drives (PSDs), pneumatic brake systems (PBSs), and compressed air vehicles (CAVs). The basic formulas and energy efficiency indicators used in a CART calculation and selection are included. New scientific research by the authors on measurements based on tank methods, numerical solutions in the process of charging and discharging, the valve-to-tank-to-valve system and pneumatic propulsion system was presented. The numerical model of the valve-tank-valve system takes into account CART polytropic charging and discharging processes, the mass flow balance equation, and the sound (choked) and subsonic mass flow rate in the inlet and outlet valves. Future research directions to improve the energy efficiency of a CART charging and discharge are highlighted. The effective density of energy storage in CART was compared to that of other renewable energy sources and other fuels. Economic and environmental issues were also considered by adopting various energy performance indicators. The discussion also focused on the design concept and computational model of the hybrid tricycle bike (HTB) pneumatic propulsion system.

A composite adaptive robust control for pneumatic servo systems with time-varying inertia

This article proposes a composite adaptive robust control for a pneumatic servo system with time-varying inertia to achieve a good tracking performance. The proposed design not only preserves the merits of both direct adaptive robust control and indirect adaptive robust control but also obtains a better performance of the working condition with time-varying inertias. Firstly, prescribed tracking performance is guaranteed without knowing the bounds of parametric and non-parametric uncertainties by leveraging a discontinuous projection and deterministic robust control technique. And a nonlinear tracking differentiator is used to obviate differential signal in backstepping. Secondly, the online parametric estimation algorithm is developed by intelligently integrating tracking error dynamics and physical plant dynamics. By effectively using the information of both tracking error and prediction error, a high adaptation gain can be used for achieving a faster parameter convergence and smaller tracking error. Moreover, exponential convergence of both tracking error and prediction error can be obtained under certain conditions. Lastly, comparative experiments on different conditions are carried out for a single-rod pneumatic cylinder driven by a proportional directional valve to demonstrate the superiority of the proposed method.

Adjustable Convergence Rate Prescribed Performance with Fractional-Order PID Controller for Servo Pneumatic Actuated Robot Positioning

Adjustable Convergence Rate Prescribed Performance with Fractional-Order PID Controller for Servo Pneumatic Actuated Robot Positioning

Design of hydraulic pneumatic control system for rail grinding car

This paper comprehensively uses the knowledge of mechatronics, mechanical structure, etc. The grinding wheel and cradle frame of the rail grinding car is studied and designed. The grinding wheel is controlled by a pneumatic servo, and the cradle frame is controlled by a hydraulic system. According to the accuracy requirements of the rail grinding car, the pneumatic servo schematic diagram of the grinding wheel to achieve precise grinding, the schematic diagram of the hydraulic control system in which the cradle frame can turn accurately, the AMESim software working interface model is established, the actual working parameters of the system components are set. After the hydraulic profiling system is designed, simulation, test, and analysis are carried out.

Constant Force Control of Centrifugal Pump Housing Robot Grinding Based on Pneumatic Servo System

In order to solve the problem of constant force control in the robot grinding process of a centrifugal pump housing a circular inner surface, this study used the force–position hybrid control mode based on a pneumatic servo system to realize the constant control of grinding force. In this process, the manipulator realizes the position and pose control of the end grinding device, and the end grinding device realizes the constant force control in the grinding process. The mathematical model of the pneumatic system is established and linearized by using the gas balance state equation, the adiabatic equation of the isentropic process, and the Sanville flow equation. The balance equation of the cylinder piston was established by using Newton’s second law, the transfer function of the contact force between the grinding device and workpiece was obtained, and the stability of the pneumatic control system was determined by the Hurwitz criterion. The PID algorithm was used to improve the displacement response speed of the system and eliminate the impact and oscillation in the force response. The feasibility, stability, and robustness of the system were verified by simulation experiments. This method has the advantages of simple control, a small amount of calculation, and a fast response, as well as providing a feasible scheme for the popularization and application of robot grinding technology.

A method to improve the motion trajectory tracking accuracy of pneumatic servo system—by exciting longitudinal resonance

A method to improve the motion trajectory tracking accuracy of pneumatic servo system—by exciting longitudinal resonance

DYNAMICS OF PNEUMATIC DRIVE. LECTURE CYCLE.MATHEMATICAL MODEL OF THE SERVO PNEUMATIC ACTUATOR

The paper considers the basic concepts of a mathematical model. The connection between the model and reality and its place and relevance in the modern world is shown. The developed mathematical model of a servo pneumatic device, which includes an actuator and a proportional or discrete pneumatic valve, is presented. The basic equations describing the dynamics of the servo pneumatic device, boundary and initial conditions are given, which make it possible to analyze the stability of the drive. A non-linear object-oriented computer model of a pneumatic servo device is presented. The model is built in the form of block diagrams of equations that describe the relationship between the original physical quantities. The influence of the nature of the inductance of the electromagnet coil on the dynamic properties of the system is shown. The developed method for identifying the transfer function of pneumatic devices and its application in the preparation of mathematical models is presented. A technique for studying the stability of pneumatic systems has been created, based on establishing an unambiguous relationship between the experimentally obtained frequency characteristics of the pneumatic apparatus included in the system and the type of its transfer function. The form of transfer functions for the pneumatic devices under consideration is obtained. For the proportional pneumatic valves presented in the work, the quality indicators of transient processes in the time domain are formulated and determined, and the phase and amplitude margins are found. The criteria for the performance of pneumatic systems are formulated. The ratios for determining the described criteria are given. The boundaries of the operability of systems with a pneumatic drive have been established. The scientific novelty of the results presented in the work is that a non-linear object-oriented computer model of a servo pneumatic device has been created, unlike the existing ones, it is built in the form of block diagrams of equations that describe the relationship between the initial physical quantities, and has the principle of modularity. The model includes the transfer function of the control devices obtained using the developed method for identifying the parameters of the transfer function. This work is based and is implemented as a course of lectures of the course “Dynamics of Pneumatic drive”, is red by the author at the Bauman Moscow State Technical University at the Department of “Hydromechanics, Hydraulic Machines and Hydropneumoautomatics” (E10), as part of the preparation of masters in the specialty 05.04.13 – Hydraulic machines and hydropneumatic drives.

DYNAMICS OF PNEUMATIC DRIVE. LECTURE CYCLE.MATHEMATICAL MODEL OF THE SERVO PNEUMATIC ACTUATOR

The paper considers the basic concepts of a mathematical model. The connection between the model and reality and its place and relevance in the modern world is shown. The developed mathematical model of a servo pneumatic device, which includes an actuator and a proportional or discrete pneumatic valve, is presented. The basic equations describing the dynamics of the servo pneumatic device, boundary and initial conditions are given, which make it possible to analyze the stability of the drive. A non-linear object-oriented computer model of a pneumatic servo device is presented. The model is built in the form of block diagrams of equations that describe the relationship between the original physical quantities. The influence of the nature of the inductance of the electromagnet coil on the dynamic properties of the system is shown. The developed method for identifying the transfer function of pneumatic devices and its application in the preparation of mathematical models is presented. A technique for studying the stability of pneumatic systems has been created, based on establishing an unambiguous relationship between the experimentally obtained frequency characteristics of the pneumatic apparatus included in the system and the type of its transfer function. The form of transfer functions for the pneumatic devices under consideration is obtained. For the proportional pneumatic valves presented in the work, the quality indicators of transient processes in the time domain are formulated and determined, and the phase and amplitude margins are found. The criteria for the performance of pneumatic systems are formulated. The ratios for determining the described criteria are given. The boundaries of the operability of systems with a pneumatic drive have been established. The scientific novelty of the results presented in the work is that a non-linear object-oriented computer model of a servo pneumatic device has been created, unlike the existing ones, it is built in the form of block diagrams of equations that describe the elationship between the initial physical quantities, and has the principle of modularity. The model includes the transfer function of the control devices obtained using the developed method for identifying the parameters of the transfer function. This work is based and is implemented as a course of lectures of the course “Dynamics of Pneumatic drive”, is red by the author at the Bauman Moscow State Technical University at the Department of “Hydromechanics, Hydraulic Machines and Hydropneumoautomatics” (E10), as part of the preparation of masters in the specialty 05.04.13 – Hydraulic machines and hydropneumatic drives.