Minh-Quyen Le

Enhanced magnetoelectric effect for flexible current sensor applications

This article focuses on the magnetoelectric (ME) effect that could be obtained in a bilayered structure consisting of the Cytop polymer and a magnetic tape filled with magnetically soft particles. The ME behavior was characterized by measuring the amplitude of the magnetoelectric current versus various input parameters that appear in theoretical expressions, i.e., the bias magnetic field, the alternative magnetic field, and the applied frequency. Experimental results were investigated together with theoretical models in order to determine the ME coupling value. It was found that the laminate material of a transversely charging electret along with bias magnetic tape could attain significant magnetoelectric properties, which were the result of the mechanical contacts between the layers and the electric-mechanical and magnetic-mechanical coupling in each phase. All the results demonstrated a possibility to realize a low-cost flexible current sensor while achieving an improved magnetoelectric response.

Sliding mode control of a pneumatic haptic teleoperation system with on/off solenoid valves

This paper presents a novel bilateral control scheme for pneumatic teleoperation systems that are actuated by low-cost solenoid valves. A sliding mode control is incorporated into a two-channel, bilateral teleoperation architecture involving position-position, force-force, or force-position schemes. An analysis of stability and transparency of the closed-loop teleoperation system is carried out. The proposed control design is verified on a single-degree-of-freedom pneumatic teleoperation system with four on/off solenoid valves. Moreover, simulation results demonstrate high accuracies in terms of position and force tracking in the teleoperation system.

Comparison of a PWM and a hybrid force control for a pneumatic actuator using on/off solenoid valves

This paper presents a new predictive hybrid control law for the control of electro-pneumatic systems using solenoid valves. The method is based on a predictive model of the mass flow rate of the valves. In order to evaluate this strategy, a comparison study in simulation has been performed with a classical PWM control for a force tracking problem. The results show that the accuracy in steady state but also the dynamic behavior of the pressures are better in the case of the hybrid control than the PWM control. The validity of the theory has been verified through simulations.

Development of a hybrid control for a pneumatic teleoperation system using on/off solenoid valves

This paper presents a new predictive hybrid control law for a pneumatic teleoperation system using solenoid valves. Based on a predictive model of the mass flow rate of the valves, this method is used within a four-channel (4CH) bilateral control architecture for haptic teleoperation. An analysis of the controller parameters is carried out in order to achieve acceptable performances. The results show that a good accuracy in position and force tracking of the teleoperation system is obtained.

An enhanced sliding-mode control for a pneumatic-actuated teleoperation system

This paper presents an enhanced sliding mode control for pneumatic master-slave teleoperation systems that are actuated by low-cost solenoid valves. A five-mode sliding control is incorporated into position-position, force-force, and force-position teleoperation architectures. While on/off valve pneumatic actuators have previously been modeled as having three discrete operating modes, an extension to five discrete control levels as proposed here helps to improve the actuator dynamic performance and reduce the switching activities of the valves. Stability and transparency analyses of the closed-loop teleoperation system are carried out. The proposed control design is experimentally tested on a single-degree-of-freedom pneumatic teleoperation system. Experimental results demonstrate high accuracies in terms of position and force tracking in the teleoperation system.

Enhanced Figures of Merit for a High-Performing Actuator in Electrostrictive Materials

The overall performance of an electrostrictive polymer is rated by characteristic numbers, such as its transverse strain, blocking force, and energy density, which are clearly limited by several parameters. Besides the geometrical impact, intrinsic material parameters, such as the permittivity coefficient as well as the Young’s modulus and the breakdown electric field, have strong influences on the actuation properties of an electroactive polymer and thus on the device’s overall behavior. As a result, an analysis of the figures of merit (FOMs) involving all relevant material parameters for the transverse strain, the blocking force, and the energy density was carried out, making it possible to determine the choice of polymer matrix in order to achieve a high actuator performance. Another purpose of this work was to demonstrate the possibility of accurately measuring the free deflection without the application of an external force and inversely measuring the blocking force under quasi-static displacement. The experimental results show good electrostrictive characteristics of the plasticized terpolymer under relatively low electric fields.

Controlling dielectric loss and ionic conductivity through processing optimization of electrostrictive polymers

Electro-active polymers (EAPs) such as P(VDF-TrFE-CTFE) was demonstrated to be greatly promising in the field of flexible sensors and actuators[1], but their low dielectric strength driven by ionic conductivity is main concern for achieving high electrostrictive performance. The well-known quadratic dependence of applied electric field on strain response as well as mechanical energy density highlights the importance of improving EAPs electrical breakdown while reducing the leakage current. This paper demonstrates that by controlling processing parameters of polymer synthesis and fabrication procedure, it is possible to drastically increase the electrical breakdown and decrease the ionic conductivity, giving rise to an enhancement in breakdown voltage of around 64% and a reduction in leakage current intensity of 73% at 30V/μm. Effect of polymer crystallinity, molecular mass, as well as crystallization temperature on leakage current were also investigated..

Strain in ferroelectric polymers under low-frequency electric fields: Experiments and modeling

The study of the electric field–induced thickness strain of ferroelectric polymers is very interesting because of the high actuating capabilities and various applications of these materials, such as electroactive materials for artificial muscles or as the active materials of membranes, due to their flexibility. This article reports on the effect on the strain properties of uniaxially and biaxially stretched β-form polyvinylidene fluoride when applying a low quasi-static triangular electric field E (100 mHz, E < 16 MV/m). For an applied electrical field at this level, the strain was proportional to the square of the electric field. The strain depended mainly on the electrostriction effect, linked to the induced reversal polarization and to interlaminar charges. The dielectric constant of the biaxially stretched polyvinylidene fluoride at 100 mHz was higher than for its uniaxially stretched counterpart. As a consequence, the induced charges and microscopic polarization for the first film exceeded those of the second one, and the electroactive strain for the biaxially stretched sample was more significant than for the uniaxially stretched film. This article first offers a description of the strain phenomenon through the polyvinylidene fluoride material during electrical excitation, after which a new model is presented. This model was developed to evaluate the induced electric current and strain phenomenon. A good agreement between simulations and experimental results was obtained.