Showing 8 results for Zareinejad
Sepehr Ramezani, Seyed Mehdi Rezaei, Mohammad Zareinejad, Kevani Baghestan,
Volume 15, Issue 1 (3-2015)
Abstract
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 needed. 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 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.
Zohreh Khodaee, Mohammad Zareinejad, Saeed Shiry Ghidary, Keivan Baghestan,
Volume 15, Issue 11 (1-2016)
Abstract
The electrohydraulic valves are commonly used in the engineering applications. These valves, as the medium elements, prepare the hydraulic systems for the electrical control applications. For the precise performance of these valves, disturbances in the valve elements dynamics will disturb the control process of the system. The electrohydraulic servo valves are greatly affected by the external acceleration, for instance in the aerospace applications. In a two stage flapper- nozzle electrohydraulic valve, the external acceleration changes the pressure of the fluid leaving the nozzles and it affects the flapper and spool of the valve like a virtual force. Thus, when the applied current is zero, the acceleration diverts the spool of the valve from the equilibrium point, and unwanted performance in the valve occurs. In this study the pilot pressures of the spool is modeled in unsteady state condition. The effects of the acceleration on the flapper and the spool of the two stage electrohydraulic valve are investigated. At the end, the obtained model is verified by use of the experimental data.
Ahsan Saeedzadeh, Seyed Mehdi Rezaei, Abdolreza Rahimi, Mohammad Zareinejad,
Volume 16, Issue 4 (6-2016)
Abstract
Hydraulic actuators are widely used where high-magnitude forces are exerted; however, they suffer from low energy-efficiency in many cases. To address this issue, there has been a surge in the volume of researches devoted to improving the efficiency of electro-hydraulic servo systems. Digital Hydraulics is the most recent method, proposed by many researchers to improve the efficiency of hydraulic actuators. Low cost and better energy efficiency are two major advantage of these systems that make them popular among researchers. This paper discusses the possibility of using a fast-switching on/off valve in a novel way, instead of servo valves to improve the efficiency of these systems. For this purpose the flow running through the fast-switching valve controlled, employing proper duty cycle. The excess pump flow is discharged to the tank directly instead of going through the relief valve when the valve is off. Thus the wasted energy, caused by the relief valve, is reduced significantly. A nonlinear backstepping controller is designed to control the duty cycle of the PWM signal of the on/off valve. The effectiveness of this method is tested after conducting experiments on a hydraulic test rig and presenting the experimental results.
Venus Pasandi, Mahyar Naraghi, Seyed Mehdi Rezaei, Mohammad Zareinejad, Keyvan Baghestan,
Volume 16, Issue 6 (8-2016)
Abstract
Stability and transparency are both very important conditions in bilateral teleoperation systems. For the design of such systems, different methods have been suggested. Among the approaches presented, passivity framework is widely utilized in which human and environment is considered passive. The operator does not make the closed-loop system unstable. In addition, it is passive against an external input. Thus the adoption of this assumption is correct for the human. Nevertheless it is a conservative presumption for the environment and according to some modern applications of teleoperation systems such as cardiac surgery, it is absolutely not acceptable. In this paper a novel control structure for nonlinear bilateral teleoperation systems interacting with active environments is addressed. In this approach, first a criterion for measuring activity of the environment is presented. Then by developing a PD controller, an algorithm that guarantees master-slave position coordination and static force reflection is introduced. The overall stability of closed loop system is proved using passivity concept and Lyapunov-Krasovskii technique. Simulations are performed to verify the performance of the proposed bilateral teleoperation systems in contact with passive and non-passive environments. Experimental results were carried out to validate the theoretical consequences.
Mohsen Asghari, Seyed Mehdi Rezaei, Mohammad Zareinejad,
Volume 16, Issue 8 (10-2016)
Abstract
Piezoelectric actuators (PA) are widely used in electromechanical system thank to interesting properties such as: high resolution, fast response, wide bandwidth, mechanical simplicity, high stiffness. Despite these unique desirable properties, they suffer from nonlinear behaviors which adversely affect the positioning accuracy. Among them, hysteresis between applied voltage , actuator position is the most important nonlinearity which can lead to significant error if not compensated. In this study, a sliding mode controller associated with an unknown input observer, which uses the position feedback provided by a selfsensing circuit, is suggested to use in micro positioning applications. The selfsensing technique is based on the linear relation between position , charge, which is measured by an active charge measurement circuit. The advantages of proposed scheme could be summarized as follows. It is a sensorless method which does not need an external position sensor. It does not need any operators to model hysteresis or its inverse. It has improved performance in comparison to traditional controllers like proportional integral (PI) controller. Obtained experimental results demonstrate the effectiveness of proposed method to use in micro-positioning applications.
H. Ghafarirad, S.m. Rezaei, M. Zareinejad,
Volume 19, Issue 5 (May 2019)
Abstract
Piezoelectric bending actuators have been extensively utilized in recent years. Two major modeling methods, lumped and continuous, have been generally proposed in previous researches for these actuators. The lumped method can only express the transverse vibration of one specified point on the actuator. In addition, the effect of higher vibrational modes has been ignored. Hence, continuous dynamic models have been proposed to rectify the mentioned drawbacks. In this method, linear constitutive equations for low voltage applications are usually applied. But, the main challenge in continuous modeling of piezoelectric actuators is the hysteresis nonlinear phenomenon caused by excitation voltages. In this paper, piezoelectric nonlinear constitutive equations have been employed to carry out the continuous dynamic model for two general types of bending actuators i.e. Series and Parallel. In addition, zero dynamic analysis for nonlinear systems has been applied to clarify the effect of higher vibrational modes the actuator dynamic behavior based on the location of Experimental results show the maximum error 1.44 and 1.2% in the identification of first and second modes, respectively, and the maximum error 2.89% in the modeling of actuator nonlinear behavior by two modes. These results validate the efficiency of the proposed dynamic model to express the actuator nonlinear behavior, dynamic analysis, and its superiority over conventional models with one mode.
Reza Nourizadeh, Mohammad Zareinejad, Seyed Mehdi Rezaei, Hamed Adibi,
Volume 22, Issue 8 (August 2022)
Abstract
Tool wear has a significant influence on the turning process. Investigations on tool wear monitoring through various methods and sensors have been widely conducted to determine and predict the tool wear. In this study sound generation mechanisms during turning process have been investigated comprehensively and three sound generation sources have been determined and distinguished. Sound generation mechanisms which originated from tool vibration, deformation in the workpiece and vibration at the contact zones (friction), have been investigated and frequency range of the sound generated through each mechanism has been determined. It has been shown that these mechanisms produce sound in 10s hertz, kilohertz and megahertz respectively. Then the mechanism which is appropriate for tool condition monitoring has been studied and suggested. Then the relation between the sound generation mechanisms and chip formation has been studied during machining. Hence, a deep understanding about the machining process has been brought out. Findings could lead to an effective approach to monitoring the machining process, not only using mathematical signal processing methods, but also through a physical comprehension background. Experimental studies have been conducted to evaluate developed theories and models. Experimental results have shown effectiveness of the proposed approach.
Amir Hossein Moradi, Hamed Ghafarirad, Seyed Mehdi Rezaei, Mohammad Zareinejad, Pouya Firuzy,
Volume 24, Issue 10 (October 2024)
Abstract
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
