Showing 4 results for Electric Actuator
Abbas Shafiee, Peiman Mosadegh, Saeid Bashash, Nader Jalili,
Volume 14, Issue 2 (5-2014)
Abstract
Parallel piezo-flexural nanopositioning stages are extensively used in advanced nano-scale imaging and manipulation applications such as scanning probe microscopy systems. One of the major deficiencies of these devices is the coupled motion between their different axes. That is, the motion of stage in one direction interferes with motions in the other directions, leading to undesirable disturbances. In this paper, analytical, dynamic, experimental, and finite element analyses are carried out to investigate the major root cause of the cross-coupling effect. Using ABAQUS FEA software, a 3D model of the stage has been developed. Model consists of a central elastic body connected to the fixed frame through four flexural hinges. A cylindrical stack of multiple piezoelectric layers is placed between the moving central body and the fixed frame. Simulations are carried out for two different friction coefficients in the contact surfaces of the piezoelectric layers, and for different frame materials. It is observed that the main cause of the cross-coupling effect is the rotation of piezoelectric stack due to its friction with the stage moving in the tangential direction, concurrent with a change in the geometry of the stage.
Rouhollah Talebi, Javad Marzban, Mehdi Haddadi,
Volume 14, Issue 10 (1-2015)
Abstract
In this paper, a control system is designed to reduce roll angle which consequently leads into increasing vehicle roll threshold during high lateral accelerations. Accordingly, the two same rotation-electric actuators are mounted on front and rear suspension system anti-roll bars. This control system turns by applying an opposite couple that is acted upon the chassis, as time varying, reduce the lateral acceleration as it possible and improves lateral stability and roll threshold during extreme maneuvers. In order to find out the effects of the performance of this active system on vehicle stability, firstly based on a nonlinear eight degrees of freedom model of the lateral dynamics of the vehicle and by taking Steering angle as an input, the kinematic parameters and finally roll threshold that is defined lateral load transfer, is estimated. Then, the optimized second order control theory with three degrees of freedom of the vehicle model is used to design the controller. Finally, with the aid of comprehensive model of the vehicle, the lateral dynamics of the vehicle as well as the effects of the controller during path of standard Fish hook maneuver are investigated.
S.f. Alem, E. Sabooni, F. Sheikholeslam, I. Izadi,
Volume 20, Issue 6 (6-2020)
Abstract
Piezoelectric actuators are the most common choice for position control with ultra-high precision. Despite the significant advantages, the linear and nonlinear dynamics of these actuators, such as hysteresis, could decrease the precision of the control system. In this research, a controller based on the sliding mode method is proposed for position control of piezoelectric actuator. Sliding mode control is a model-based and useful method in nanopositioning systems. In this research, Bouc-Wen model is used for description of the actuator’s behavior. In this model, the linear dynamic is modeled with mass, stiffness and damping terms, and the hysteresis is modeled by its nonlinear dynamics. Usually, there are mismatch and uncertainty between the physical system and mathematical model. For stability analysis of the prevalent sliding mode control, the upper bound of uncertainty must be known. But, in practical systems, this is not possible, simply. On the other hand, selecting the large values for this bound, increases the controller gain and distances it from the optimum value. The proposed adaptive robust control eliminates the dependency to the upper bound of uncertainty. This is done by introducing an online adaptive law for estimating this bound. Proposing this law, asymptotic stability of the closed-loop control system is proven. Implementing the presented method on the laboratory setup and simulator software, its effectiveness is shown by simulation and experimental results.
A. Sadri Koupaei, D. Soleymanzadeh, H. Ghafarirad,
Volume 20, Issue 6 (6-2020)
Abstract
Today, piezoelectric actuators are widely used in micro-positioning applications due to unique features such as high precision, fast response and high natural frequency. Despite the aforementioned characteristics, nonlinear characteristics such as hysteresis deteriorate the precision of piezoelectric actuators. In order to reduce the effect of hysteresis in control applications, external sensors are used for feedback control schemes. But, high costs and space limitations are prohibitive factors which limit the application of external sensors. Hence, an alternative is using self-sensing methods that is based on electromechanical characteristics of piezoelectric materials which eventually eliminate external sensors. In this research, self-sensing method is applied for position estimation in piezoelectric actuators. The most conventional method is based on the linear relation of electrical charge and actuator position which the position can be estimated by measuring the actuator charge. But this method is faced with serious challenges due to charge drift, especially at low frequencies. For this purpose, a method for modeling and compensating of charge drift is proposed. Then, by linearization of the electric charge-position relation, the self-sensing method is implemented based on the compensated electric charge measurement. Experiments have confirmed that this method can effectively estimate the actuator position with 1.5% estimation error in the presence of charge leakage.
