Actuators, Volume 9, Issue 3 (September 2020) – 46 articles

Minimally invasive surgery (MIS) is a surgical technique that facilitates access to the internal tissues and organs of a patient’s body via a limited number of small incisions or natural orifice of the patients. Such a technique requires specialized slender surgical instruments with a high levels of dexterity and functionality. However, the currently available MIS instruments are rigid and could offer only limited degrees of freedom (DOFs) that hampers the surgeon’s effort to perform the required operation accurately. In this study, we have developed a hybrid electromagnetic and tendon-driven actuator as an integral part of MIS surgical instruments to provide them with optimum angulation. The design uses a novel electromagnetic structure to lock the position of individual joints, and a tendon-driven structure for the articulation of the surgical instrument. The finite element method (FEM) was utilized to predict the performance of the actuator, which was experimentally validated. Subsequently, a prototype was assembled, and corresponding kinematics analysis was presented to visualize the improvement of the developed mechanism on the functional workspace of the MIS instruments. It was concluded that the developed mechanism could offer three additional DOFs for the surgical instrument and angulation of 180° for each articulated joint. Full article

Therapy with robotic tools is a promising way to help improve verbal and nonverbal communication in children. The robotic tools are able to increase aspects such as eye contact and the ability to follow instructions and to empathize with others. This work presents the design methodology, development, and experimental validation of a novel social robot based on CompliAnt SofT Robotics called the CASTOR robot, which intends to be used as an open-source platform for the long-term therapy of children with autism spectrum disorder (CwASD). CASTOR integrates the concepts of soft actuators and compliant mechanisms to create a replicable robotic platform aimed at real therapy scenarios involving physical interaction between the children and the robot. The validation shows promising results in terms of robustness and the safety of the user and robot. Likewise, mechanical tests assess the robot’s response to blocking conditions for two critical modules (i.e., neck and arm) in interaction scenarios. Future works should focus on the validation of the robot’s effectiveness in the therapy of CwASD. Full article

This article describes a mathematical model simplification, designed to automate the iterative process of non-circular drilling with a precise shape. This model has been optimized for systems that already have experimental data for processing and analysis. Additionally, using optimization steps, the model can be used for systems with insufficient experimental data with a self-learning opportunity. The high-end model can be used for drilling systems represented as a “black box” without knowing of any parameters of the system. The simplification and assumptions algorithm is based on controlling the input signal for non-circular drilling in the cylinders of internal combustion engines using a drilling machine controlled by 8 piezoelectric actuators. The total dynamics of this system is unknown and consists of the dynamics of electrical converters, piezo-kinematics, and mechanics. Simplification is carried out starting from the methods of diacoptics for a complex system with different process-flow rates, and ending with one or the sum of linear models valid for a given system of assumptions. Full article

In this paper, static characteristics of a tilting five-pad rocker-backed journal bearing with an asymmetric geometry, i.e., different clearance for each pad, are investigated. A thermo-elasto-hydrodynamic (TEHD) model considering the elasticity of the pad and pivot is used for the simulation. The pivot stiffness of each pad obtained by experiment is also introduced in the model. The experimental tests were carried out on a tilting pad journal bearing (TPJB) with a nominal diameter of 100 mm and a length-to-diameter (L/D) ratio of 0.7 with load-between-pad (LBP) and load-on-pad (LOP) arrangements. Several analyses, including numerical simulations and experimental measurements, are implemented in order to obtain the static behaviors of the tilting-pad bearing under variations of rotational speed, amplitude and direction of applied static load, such as clearance distribution profile, static eccentricity, temperature and pressure distribution. The results show that the effect of asymmetric geometry on the static characteristics is not negligible. Full article

To improve the stealth capability of a military aircraft, the reduction in core length is essential to reduce the heat signature and the noise characteristics of the engine exhaust. The efficacy of rectangular vortex generators in achieving these objectives has been demonstrated by several researchers, owing to their simplicity. One way of producing the mixed-size vortices is by providing corrugations on the edge of the tab (actuator). Therefore, in the current study, two tabs of aspect ratio 1.5, mounted diametrically opposite to each other at the outlet of a Mach 1.73 circular nozzle, are examined at varying levels of expansions, ranging from overexpanded to underexpanded jet states. In addition, to generate the mixed-size vortices, three corrugation geometries, i.e., rectangular, triangular, and semicircular, are configured along the tab edges. Both quantitative and qualitative investigations are carried out by using the pitot probe to measure the stagnation pressures and by utilizing a shadowgraph technique to visualize the flow field. The corrugated tabs generated a significant mixing, and among them, the tabs with triangular corrugations are found to be most effective. A maximum reduction of about 99.7% in the supersonic core is obtained with triangular corrugated tabs at near-correct-expansion, corresponding to nozzle pressure ratio (NPR) 5. Interestingly, the semicircular corrugated tab significantly reduces the asymmetry near the nozzle exit plane. The shadowgraph images confirm the efficacy of different corrugated tabs in reducing the strength of the waves, prevalent in the supersonic core. Full article

Machine-induced vibrations represent, for several reasons, a crucial design issue for industrial buildings. At the early design stage, special attention is thus required for the static and dynamic performance assessment of the load-bearing members, given that they should optimally withstand ordinary design loads but also potentially severe machinery operations. The knowledge and reliable description of the input vibration source is a key step, similarly to a reliable description of the structural system, to verify. However, such a kind of detailing is often unavailable and results in a series of simplified calculation assumptions. In this paper, a case-study eyewear factory built in 2019 is investigated. Its layout takes the form of a two-story, two-span (2 × 14.6 m) precast concrete frame (poor customer/designer communication on the final equipment resulted in various non-isolated computer numerical control (CNC) vertical machines mounted on the inter-story floor, that started to suffer from pronounced resonance issues. Following past experience, this paper investigates the validity of a coupled experimental–numerical method that could be used for efficient assessment predictive studies. Based on on-site experiments with Micro Electro-Mechanical Systems (MEMS) accelerometers mounted on the floor and on the machine (spindle included), the most unfavorable machine-induced vibration sources and operational conditions are first characterized. The experimental outcomes are thus used to derive a synthetized signal that is integrated in efficient one-bay finite element (FE) numerical model of the floor, in which the machine–structure interaction can be taken into account. The predictability of marked resonance issues is thus emphasized, with a focus on potential and possible limits of FE methods characterized by an increasing level of detailing and computational cost. Full article

Hybrid pneumatic–electric actuators (HPEAs) are redundant actuators that combine the large force, low bandwidth characteristics of pneumatic actuators with the large bandwidth, small force characteristics of electric actuators. It has been shown that HPEAs can provide both accurate position control and high inherent safety, due to their low mechanical impedance, making them a suitable choice for driving the joints of assistive, collaborative, and service robots. If these characteristics are mathematically modeled, input allocation techniques can improve the HPEA’s performance by distributing the required input (force or torque) between the redundant actuators in accordance with each actuator’s advantages and limitations. In this paper, after developing a model for a HPEA-driven system, three novel model-predictive control (MPC) approaches are designed that solve the position tracking and input allocation problem using convex optimization. MPC is utilized since the input allocation can be embedded within the motion controller design as a single optimization problem. A fourth approach based on conventional linear controllers is included as a comparison benchmark. The first MPC approach uses a model that includes the dynamics of the payload and pneumatics; and performs the motion control using a single loop. The latter methods simplify the MPC law by separating the position and pressure controllers. Although the linear controller was the most computationally efficient, it was inferior to the MPC-based controllers in position tracking and force allocation performance. The third MPC-based controller design demonstrated the best position tracking with RMSE of 46%, 20%, and 55% smaller than the other three approaches. It also demonstrated sufficient speed for real-time operation. Full article

For expanding the driving mode of the piezoelectric motor, a novel piezoelectric motor modulated by a magnetic field is proposed. This driving system combines piezoelectric driving and magnetic modulation together and can transform the reciprocating swing of the stator into step running of the rotor via the intermittent magnetic clamping between the rotor and stator. For investigating the inherent character of dynamics, the dynamic equations of key parts of the driving system are established. The natural frequencies and mode functions of the driving system are solved. A prototype was fabricated to prove the dynamic analysis and measure the output characteristic. The results show that the nature of the frequency measured from the test is coincident with theoretical analysis. In addition, by applying the driving frequency of 3 Hz, the voltage of the modulating signal of 4.5 V, the phase difference α between driving signal and modulating signal of 30°, the ideal outputs are 0.1046 rad/min for velocity and 0.405 Nmm for torque. Full article

This paper shows the construction of a low-cost, open-source mechanical ventilator. The motivation for constructing this kind of ventilator comes from the worldwide shortage of mechanical ventilators for treating COVID-19 patients—the COVID-19 pandemic has been striking hard in some regions, especially the deprived ones. Constructing a low-cost, open-source mechanical ventilator aims to mitigate the effects of this shortage on those regions. The equipment documented here employs commercial spare parts only. This paper also shows a numerical method for monitoring the patients’ pulmonary condition. The method considers pressure measurements from the inspiratory limb and alerts clinicians in real-time whether the patient is under a healthy or unhealthy situation. Experiments carried out in the laboratory that had emulated healthy and unhealthy patients illustrate the potential benefits of the derived mechanical ventilator. Full article

Inherent hysteresis behaviour of pressurized artificial muscles is complicated to understand and handle, calling for experimental research that allows the modelling of this phenomenon. The paper presents the results of the experimental study of the hysteretic behaviour of a small-size pneumatic muscle. The specific hysteresis loops were revealed by isotonic and isometric tests. Starting from hypothesis according to that the tube used for the pneumatic muscle is made entirely of aramid fibres enveloped by an elastomer material that merely ensures their airtightness, the paper presents the hysteresis curves that describe the radial and axial dimensional modifications as well as the variation of the developed forces for different feed pressures. The obtained third-degree polynomial equations underlie the configuration of high-performance positioning systems. Full article

In this paper, a new analytical method using Lagrange equations for the analysis of magnetic levitation (MagLev) systems is proposed, using Thomson’s jumping ring experiment. The method establishes the dependence of the primary and induced currents, and also the equilibrium height of the levitating object on the input voltage through the mutual inductance of the system. The mutual inductance is calculated in two ways: (i) by employing analytical formula; (ii) through an improved semi-empirical formula based on both measurements and analytical results. The obtained MagLev model was analyzed both analytically and numerically. Analytical solutions to the resulting equations were found for the case of a dynamic equilibrium. The numerical results obtained for the dynamical model under transient operation show a close correspondence with the experimental results. The good precision of the analytical and numerical results demonstrates that the developed method can be effectively implemented. Full article

Magnetostrictive materials are a group of smart materials with comparable properties to piezoelectric materials regarding strain and operating frequency. In contrast, the Curie temperature is much higher and the principle effect allows different actuator designs. Especially in the case of rotating actuators in ultrasonic assisted machining, a high potential is seen for a simplified energy transmission. In the study, a test stand for a rotating actuator with simultaneous vibration in longitudinal direction was designed to show the proof of principle for this idea. It was shown that the current inducing the magnetic field as well as its frequency influence the amplitude of the rotating actuator. This is a first step to developing a rotating actuator for ultrasonic machining. Full article

The lack of suitable actuators has hampered the development of high-performance machines or robots that can compete with living organisms in terms of motion, safety, and energy efficiency. The adaptation properties of biological systems to environmental variables—for example, the control performance of biological muscle with variable stiffness properties—exceeds the performance of mechanical devices. The variable stiffness characteristics of elastic actuators are different from the operating principle of conventional solids. Although there has been a lot of work on the design of elastic actuators in recent years, a low-cost and compact elastic actuator that can be used in place of standard rigid servo actuators is not yet available. In this study, a standard servo motor has been transformed into an elastic actuator by an elastic coupling attached to the gear system. The elastic coupling consists of four small steel beams with a cylindrical cross section placed on the circular disk, and the stiffness of the actuator is adjusted by varying the clutch length of the cylindrical beams. In this study, this innovative design is explained, then the equations expressing the variation of the torsional stiffness of the cylindrical beams with the coupling length and solutions of these equations are given. The experimental results are presented to show the ability of the proposed actuator to control position and regulate the stiffness independently. Full article

Soft robots and devices exploit deformable materials that are capable of changes in shape to allow conformable physical contact for controlled manipulation. While the use of embedded sensors in soft actuation systems is gaining increasing interest, there are limited examples where the body of the actuator or robot is able to act as the sensing element. In addition, the conventional feedforward control method is widely used for the design of a controller, resulting in imprecise position control from a sensory input. In this work, we fabricate a soft self-sensing finger actuator using flexible carbon fibre-based piezoresistive composites to achieve an inherent sensing functionality and design a dual-closed-loop control system for precise actuator position control. The resistance change of the actuator body was used to monitor deformation and fed back to the motion controller. The experimental and simulated results demonstrated the effectiveness, robustness and good controllability of the soft finger actuator. Our work explores the emerging influence of inherently piezoresistive soft actuators to address the challenges of self-sensing, actuation and control, which can benefit the design of next-generation soft robots. Full article

In the current clinical practice, the diagnosis of Rheumatoid Arthritis (RA) draws on the qualitative evaluation of pain sensitivity thresholds which is affected by several source of uncertainties, due to an operator-dependent diagnostic protocol. Taking our cue from the diagnostic shortcomings, we have explored the possibility of automating the measurement of mechanical nociceptive thresholds through the adoption of soft pneumatic actuators controlled by an embedded control unit. In this work, we want to show that a purpose-made biomechatronic device actuated by soft and pneumatic actuators is potentially a boon both for rheumatologists and biomedical researchers involved in nociception and physicophysical studies. In the full breadth and scope of the objective diagnosis of RA, the first prototype of a novel biomechatronic device for quantitative and automatic measurement of mechanical nociceptive thresholds has been designed and tested through nociception experiments on 10 subjects. The experimental results show that the designed device can reliably generate the controllable and repeatable nociceptive stimuli needed for the objective diagnosis of RA. Full article

Active suspension systems help to deliver superior ride comfort and can be used to resolve the objective conflict between ride comfort and road-holding. Currently, there exists no method for analyzing the influence of actuator limitations, such as maximum force and maximum rate of change, on the achievable ride comfort. This research paper presents a method that is capable of doing this. It uses model predictive control to eliminate the influence of feedback controller performance and to integrate both actuator limitations and necessary constraints on dynamic wheel-load variation and suspension travel. Various scenarios are simulated, such as driving over a speed bump and inner city driving, as well as driving on a country road and motorway driving, using a state-of-the-art quarter-car model, parameterized for a luxury class vehicle. It is analyzed how comfort, or in one scenario road-holding, can be improved with consideration for the actuator limitations. The results indicate that actuator rate limitation has a strong influence on vertical vehicle dynamics control system performance, and that relatively small maximum forces of around 1000 to $2000$ N are sufficient to successfully reject disturbances from road irregularities, provided the actuator is capable of supplying the forces at a sufficiently high rate of change. Full article

Pneumatic linear peristaltic actuators can offer some potential advantages when compared with conventional ones. Low cost, virtually unlimited stroke and easy implementation of curved motion profiles are among those benefits. On the downside, these actuators suffer high mechanical stress, which leads to short endurance and increased leakage between chambers during the actuator lifetime. This paper contributes to this field by experimentally characterizing the life behavior of a prototype of a linear pneumatic peristaltic actuator where force—instead of displacement—between rollers is imposed. It is shown that the use of an imposed force configuration has a significant impact in the actuator life time. In fact, the proposed actuator configuration has an average endurance of up to 250% higher than the one previously presented in the literature. This result was obtained while maintaining almost zero leakage between chambers, despite the hose wear throughout the service life. Finally, this paper explores the use of different hose geometries to increase the actuator life span. To this end, a preliminary study is presented where two different 3D printed hose cross sections are tested and compared with a circular one. Full article

$H_{\infty }$ surge control in centrifugal compressors by using active magnetic bearings (AMBs) has been successfully designed and implemented. However, the structure and design process of $H_{\infty }$ surge control are quite complex. This paper reports on the design and implementation of fractional-order proportional-derivative control (FOPD) that results in the required specifications of surge control with a simple controller structure. To validate its effectiveness, the proposed FOPD surge controller has been implemented on a centrifugal compressor test rig equipped with AMBs. Simulation and experimental results show that the FOPD surge controller outperforms integer-order PD (IOPD) control in extending the surge limit in terms of the mass flow and provides similar performance as the $H_{\infty }$ controller. Full article

Specifications of actuators when interacting with biological systems such as the human body are entirely different from those used in industrial machines or robots. One important instance of such applications is assistive devices and prostheses. Among various approaches in designing prostheses, recently, semi-active systems attracted the interest of researchers. Even more, some commercial systems benefit from designs such as implementing an adjustable damper in the ankle prosthesis to increase range of motion. The main reason for adding damper is to assist amputees’ walking locomotion on slopes (especially downward). In this paper, we introduce a hydraulic damper design for use in the transtibial prosthetic foot. In the fabricated hydraulic prosthetic foot, two one-way flow control valves are exploited to tune the damping ratio in the plantar flexion and dorsiflexion, independently. Using the carbon prosthetic foot in series to a damper and spring could improve mimicking intact foot movement. First, we present the details of the damper and the prosthesis mechanical design. Then, we introduce experiment-based modeling for the damper’s conceptual design in the proposed prosthesis using SIM-Hydraulic and MATLAB. This device is fabricated and tested in a pilot experiment. The compact design with reduced weight and size of the prosthetic foot are additional advantages of the proposed prosthetic foot. Full article

This paper presents a self-contained micro-optical system that is magnification-controlled by adjusting the positions of the microlens in the device via pneumatic air pressure. Unlike conventional dynamic microlenses made from a liquid or polydimethylsiloxane (PDMS) that change their shapes via external actuation, this system combines a fixed-curvature glass microlens, an inflatable PDMS layer, and the external pneumatic air pressure supply as an actuator. This device showed several advantages, including stable inflation, firm structure, and light weight; it achieved a larger displacement using the glass microlens structure than has been reported before. This fixed-curvature microlens was made from 120 µm-thick flat thin glass slides, and the system magnification was manipulated by the deflection of a 100 µm-thick PDMS layer to alter the distance from the microlens to the microfluidic channel. The system magnification power was proportional to the air pressure applied to the device, and with a 2.5 mbar air pressure supply, a 2.2X magnification was achieved. This optical system is ideal for combining with high resolving power microscopy for various short working distance observation tasks, and it is especially beneficial for various chip-based analyses. Full article

This work explores the extent of jet mixing for a supersonic jet coming out of a Mach 1.8 convergent-divergent nozzle, controlled with two short rectangular vortex-generating actuators located diametrically opposite to each other with an emphasis on numerical methodology. The blockage ratio offered by the tabs is around 0.05. The numerical investigations were carried out by using a commercial computational fluid dynamics (CFD) package and all the simulations were performed by employing steady Reynolds-averaged Navier–Stokes equations and shear-stress transport $k-\omega$ turbulence model on a three-dimensional computational space for more accuracy. The numerical calculations are administered at nozzle pressure ratios (NPRs) of 4, 5, 6, 7 and 8, covering the overexpanded, the correctly expanded and the underexpanded conditions. The centerline pressure decay and the pressure profiles are plotted for both uncontrolled and the controlled jets. Numerical schlieren images are used to capture the barrel shock, the expansion fans and the Mach waves present in the flow field. Mach contours are also delineated at varying NPRs indicating the number of shock cells, their length and the variation of the shock cell structure and strength, to substantiate the prominent findings. The outcomes of this research are observed to be in sensible concurrence with the demonstrated exploratory findings. A reduction in the jet core length of 75% is attained with small vortex-generating actuators, compared to an uncontrolled jet, corresponding to nozzle pressure ratio 5. It was also seen that the controlled jet gets bifurcated downstream of the nozzle exit at a distance of about 5 D, where D is the nozzle exit diameter. Furthermore, it was fascinating to observe that the jet spread increases downstream of the nozzle exit for the controlled jet, as compared to the uncontrolled jet at any given NPR. Full article

The purpose of this study was to determine how to improve the energy-harvesting properties of polymer electrolyte membranes by varying their porosity. We achieved this by applying microcellular foaming process (MCP) to Nafion-based ionic polymer–metal composites (IPMCs). We manufactured an IPMC by forming a Pt electrode through an electroless plating method on the Nafion film, to which porosity was imparted by varying the foaming ratio and inducing deformation by vibrating the specimen using a prototype device that we developed ourselves. We attempted to harvest energy via fluid flow that occurred owing to displacement movement. When the Nafion film was foamed at a temperature of 140 °C or higher, it was observed that cells with size of approximately 1 µm or more were formed, and when the saturation temperature was lowered, a denser and larger number of cells were formed. Moreover, the cells formed on the electrolyte membrane allowed the retention of more water. Water retention generated charges contributed to the operational stability of IPMC. This was attributed to the difference in the amount of charge generated by changing only the internal morphology of the electrolyte membrane, without changing the substrate or the electrode material. Full article

In this paper, a two-loop fault-tolerant attitude control scheme is proposed for flying-wing aircraft with actuator faults. A regular nonlinear dynamic inversion (NDI) control is used in the outer attitude loop, and a finite time convergence incremental nonlinear dynamic inversion (FINDI) control combined with control allocation strategy is used in the inner angular rate loop. Prescribed performance bound (PPB) is designed to constrain the tracking errors within a residual set, so the prescribed system performance can be guaranteed. An optimal anti-windup (AW) compensator is introduced to solve the actuator saturation problem. Simulation results demonstrate the effectiveness of the proposed approach. Full article

This paper explores the new control strategy of an actively actuated eccentric mass system (AAEMS) for cancelling the rotor imbalance vibration. The AAEMS consists of an eccentric mass with an actuator that actively moves around the circular guided track attached to the rotating rotor thus can generate an effective centrifugal force perpendicular to any tangential direction of the guided circular trajectory. Therefore, once the magnitude and angular position of the inherited static imbalance of the rotor are identified, this actively controlled system can be dispatched to the target angular position(s) where the effective centrifugal force due to rotor imbalance is completely or partially removed. This novel device is currently available and widely used in the vibration isolation problem. However, the study of its control strategy is quite limited, thus, herein, we proposed a new possible control technique, guaranteeing both the robust vibration isolation performance and less control power consumption. To meet such needs, three primary functions of AAEMS are addressed here. First, two (Extended) Kalman filters were employed to sequentially estimate the unknown imbalance of the rotor and the unknown coulomb friction induced between the contact surface of the circular track and the counter-contacted parts of AAEMS. Second, the position control of the AAEMS is achieved by a linear quadratic regulator (LQR)-based optimal control law, simultaneously minimizing the imbalance vibration of the rotor as well as the power consumption of its own actuator. Third, for the situation where the estimation and control errors are presented, thus causing the failure to an acceptable threshold for imbalance vibration, the trial-error-based fine-tuning angular position control was proposed. The effectiveness of the proposed control strategy was evaluated via the simulations and this study shows the practical potential for addressing the AAEMS-based imbalance vibration elimination. Full article

Mobile robots that are required to climb inclined ferromagnetic surfaces typically employ magnetic wheels. In order to design magnetic wheels and to properly size the permanent magnet as magnetizing source without the need for finite element analyses, a model that predicts the attractive magnetic force is necessary. In this paper, an analytical force model is derived by estimating the reluctance between the wheel and the surface. A magnetic circuit is constructed, incorporating the leakage flux from the side of the wheel. The model is validated against the results from finite element analyses and measurements from a test rig and a wheel prototype. Within the limitations of the model, it can adequately predict the force and can be used for initial design of magnetic wheels. Full article

An active mass damper (AMD) was developed that uses a linear motor and coil spring to reduce the vertical vibration of a long-period cable-stayed bridge subjected to wind and earthquake loads. A scaled-down bridge model and AMD were fabricated, and the control effect of the AMD was investigated experimentally and analytically. The AMD was controlled via a linear quadratic Gaussian algorithm, which combines a linear quadratic regulator and Kalman filter. The dynamic properties were investigated using a 1/10 scale indoor experimental model, and the results confirmed that the measured and analytical accelerations were consistent. A vibrator was used to simulate the wind-induced vibration, and the experimental and analytical results were consistent. The proposed AMD was confirmed to damp the free vibration and harmonic load and increase the damping ratio of the bridge model from 0.17% to 9.2%. Finally, the control performance of the proposed AMD was numerically investigated with the scaled-down bridge model subjected to the El Centro and Imperial Valley-02 earthquakes. These results were compared with those of a TMD, and they confirmed that the proposed AMD could reduce excessive vertical vibrations of long-period cable-stayed bridges subjected to wind and earthquakes. Full article

This paper presents the design of a new flexure-based xy micropositioning stage with a large hollow platform, which is suitable for practical use with a microscope. The designed mechanism has a parallel-kinematic structure and is actuated by two voice coil motors. By employing multistage compound parallelogram flexures, the stage is designed as a four-layer structure, which produces a motion output platform with a large hollow space and large range of motion. Analytical modeling was carried out for parametric design of the stage. Evaluation results show that the designed xy stage exhibits a large safety factor and high natural frequency. Moreover, the large hollow platform is well-suited for practical applications with a microscope. Full article

Active flow control of surface dielectric barrier discharge (SDBD) plasma is a technology that converts electrical energy into kinetic energy to achieve flow control. Its main application areas are concentrated in the aviation field. Undoubtedly, few studies have applied it in the field of automobile flow control. Meanwhile, during high-speed driving, there is a serious airflow separation phenomenon at the rear of notch-back cars, which brings a large area of negative pressure to the back of the cars. Due to the huge pressure difference between the front and end of the cars, it will increase the driving drag and fuel cost of the car. In this context, we seek to discuss the control effect on the airflow separation at the rear of the notch-back by using the phenomenological numerical simulation method of plasma flow control. Firstly, the plasma actuator is arranged separately on the rear end of the roof, c-pillar, upper and side of the trunk to study the control effect of airflow separation. After that, the plasma actuators at each position are combined and actuated simultaneously. We try to observe the control effect of airflow separation and select the combination with the best drag reduction effect. In the third stage, an efficient global optimization (EGO) algorithm based on kriging response surface is applied to optimize the supply voltage of the best combination that has been obtained before and obtain the driving voltage parameter of each actuator optimized under this combination. The results show that when plasma actuation is applied at four locations, only the actuation applied to the side of the luggage compartment has a significant drag reduction effect, while in other cases, the drag coefficient will increase. Specifically, drag reduction is better when the actuation is applied at four positions simultaneously. The maximum drag reduction coefficient of the car is reduced by 13.17%. Full article

Pneumatic linear peristaltic actuators can offer some potential advantages when compared with conventional ones. The low cost, virtually unlimited stroke and easy implementation of curved motion profiles are among those benefits. On the downside, these actuators suffer high mechanical stress that can lead to short service life and increased leakage among chambers during the actuator lifetime. One way to cope with this problem is to impose the force—instead of the displacement—between rollers, as this has been shown to improve the endurance of the hose while reducing leakage during the actuator lifetime. This paper presents closed control loop results using such a setup. Previous studies with linear peristaltic actuators have revealed that, although it is possible to reach zero steady state error to constant references with closed loop control, the dynamic response obtained is very slow. This paper is mainly focused on this topic, namely on the development of several control laws to improve the dynamic performance of the system while avoiding limit cycles. The new developed control law leads to an average time of 1.67 s to reach a 0.1 mm error band in an experiment consisting of a series of 16 steps ranging from 0.02 to 0.32 m in amplitude. Full article