Actuation Efficiency Research Articles

Micromechanics Study on Actuation Efficiency of Hard-Magnetic Soft Active Materials

Abstract Hard-magnetic soft active materials have drawn significant research interest in recent years due to their advantages of untethered, rapid and reversible actuation, and large shape change. These materials are typically fabricated by embedding hard-magnetic particles in a soft matrix. Since the actuation is achieved by transferring the microtorques generated on the magnetic particles by the applied magnetic field to the soft matrix, the actuation depends on the interactions between the magnetic particles and the soft matrix. In this paper, we investigate how such interactions can affect the actuation efficiency by using a micromechanics approach through the representative volume element simulations. The micromechanics reveals that particle rotations play an essential role in determining the actuation efficiency, i.e., the torque transmission efficiency. In particular, a larger local particle rotation in the matrix would reduce the effective actuation efficiency. Micromechanics simulations further show that the efficiency of the torque transmission from the particles to the matrix depends on the particle volume fraction, the matrix modulus, the applied magnetic field strength, as well as the particle shape. Based on the micromechanics simulations, a simple theoretical model is developed to correlate the torque transmission efficiency with the particle volume fraction, the matrix modulus, as well as the applied magnetic field strength. We anticipate this study on the actuation efficiency of hard-magnetic soft active materials would provide optimization and design guidance to the parameter determination for the material fabrication for different applications.

Presentation, Modeling and Experiments of an Electrostatic Actuator Based Catom for Programmable Matter

Nowadays, the concept of programmable matter paves the way for promising applications such as reshaping an object to test different configurations, modeling or rapid prototyping. Based on elementary modules, such matter can be arranged and disassembled easily according to the needs of the designers. Several solutions have been proposed to implement this concept. Most of them are based on modular self-reconfigurable robotics (SMR) that can work together and move relatively to one another in order to change their configuration. Achieving such behavior requires to solve some technological challenges in particular module’s geometry and actuation. In this paper, we build and develop a proof of concept for a catom based on electrostatic actuation. The modeling and analysis of the actuator functioning as catom is given after a comparison of various possible actuation. Simulations as well as experiments validations are afterwards carried out to confirm and demonstrate the efficiency of electrostatic actuation to achieve latching capabilities of the proposed catom.

An Inertial Piezoelectric Drive with an Electrodynamic Actuator

In this paper, we study the performance of inertial linear-rotary piezoelectric drives under conditions that impede starting: lowered voltage, long idle time, high axial load, and the use of polymer materials. The application of an electrodynamic actuator for solving this problem is considered. The design of the passive actuator consisting of a magnet and a metal rod, as well as the actuator alignment procedure, is presented. Based on a system of electromechanical analogies, a model of an inertial drive with an electrodynamic actuator is described. This model was used to study a drive with an actuator, and the results of the study are presented. The actuator is shown to have two operation modes depending on the rotation direction of the drive. The features of the drive operation in these modes are described. In addition, the model showed that the actuator efficiency significantly decreases at small deformations of the piezoelectric element. In an active electrodynamic actuator, a magnet and a solenoidal coil are used to additionally affect the piezoelectric elements of the drive. The operation features of the active actuator are considered. A prototype of an inertial piezoelectric linear-rotary drive with an electrodynamic actuator is described, and the results of its tests and recommendations on the use of active and passive actuators are provided.

Drag reduction on a three-dimensional model vehicle using a wire-to-plate DBD plasma actuator

In this paper, we apply a wire-to-plate DBD plasma actuator to a three-dimensional model vehicle (called Ahmed body) for drag reduction at the free-stream velocities of $$U_\infty = 10{-}20\ \hbox {m}/\hbox {s}$$. An actuator with a thin wire of 11 µm diameter as an exposed electrode is located at the front edge of the slanted surface of the Ahmed body, and its spanwise length and applied voltage are varied. The induced mean velocity by the actuator reaches up to about 4.2 m/s at the applied voltage of 9 kV. With actuation, the drag is reduced by the amount of maximum 10% at $$U_{\infty } = 10\ \hbox {m}/\hbox {s}$$. The maximum efficiency of the present actuator is 0.1–0.12 depending on the spanwise length of the actuator, applied voltage, and free-stream velocity. The present drag reduction and efficiency are higher than those of a conventional plate-to-plate DBD plasma actuator. With surface-pressure and PIV measurements, it is shown that the flow above the slanted surface is significantly affected by the spanwise length of the actuator, and the streamwise momentum induced by the actuator suppresses the flow separation at the front edge of the slanted surface and recovers the pressure on the slanted and vertical base surfaces, resulting in drag reduction.

Research on an Electromagnetic Actuator for Vibration Suppression and Energy Regeneration

This paper proposes an electromagnetic actuator that concurrently realizes two working functions of vibration suppression and energy regeneration. The actuator consists of four permanent magnetic rings, three soft iron rings, three coils, and three springs. The design of the electromagnetic actuator is based on finite element method (FEM) analysis, and the prototype is based on this analysis. Based on the prototype, the characteristics of the electromagnetic actuator, which has an output force–current coefficient of 39.49 N/A, are explored. A control algorithm with a position controller and an acceleration controller are applied to the actuator. When an impulse excitation is input to the electromagnetic actuator, the acceleration of the controlled object decreases from 114.26 m/s2 to 3.14 m/s2 here. Moreover, when the sinusoidal excitation with a 3 mm amplitude and 5 Hz frequency is input to the electromagnetic actuator, the vibration amplitude of the controlled object is 0.045 mm, suppressed within 1.46% when compared with the input signal. The peak value of the regenerated electromotive force is 1.97 V here, and the actuator efficiency for regenerating energy is 11.59%. The experimental results with multiple frequencies and amplitudes also show that the amplitude of the controlled object can be suppressed within 5.5%, and that the ratio of the electromotive force (EMF) to the input amplitude is 0.13. The results indicate that this electromagnetic actuator can suppress vibrations effectively and regenerate energy from vibrations.

DESIGN AND SIMULATION OF TWO-JOINT PRESSURE-DRIVEN SOFT BIONIC FISH

In order to study and design a new type of bionic robotic fish with high softness and strong environmental adaptability, imitating the shape of shark and the swimming posture of tuna fish, a bionic robotic fish with hydraulic flexible driving structure is designed. In view of the problem that the single-joint hydraulically driven flexible robotic fish has a C-shaped swing posture that does not conform to the swing rule of tuna fish, a two-joint hydraulic flexible drive is used to simulate the S-shaped swing of the fish, and the internal structure of the bionic fish is designed according to the principle of the hydraulic flexible actuator. According to the theoretical wave equation, the swing amplitude of the robotic fish is determined, the magnitude of the pressure load applied inside the flexible actuator is calculated by numerical simulation, and the driving efficiency of the hydraulic flexible actuator is analyzed and calculated. The software of finite element analysis is used to simulate the autonomous swimming process of the robotic fish in the fluid. And the autonomous cruise process of the two-joint robotic fish and the one-joint roboic fish are simulated and compared to obtain the movement postures, swimming velocity and flow field of the two robotic fishes when they autonomously cruised in the fluid. The results show that at the same frequency and tail-fin swing, the average velocity of the two-joint soft roboic fish cruising is 0.29 BL/s, which is higher than the average velocity of the the one-joint roboic fish 0.15 BL/s. And frome the velocity vector diagram, it can be concluded that the S-type swing of the two-joint roboic fish is closer to the real fish swing attitude, and a series of discrete reverse Karman Vortex Streets will be generated during the movement, so the two-joint bionic fish has a higher propulsion efficiency.

Sliding discharge plasma actuation for forebody vortex control on a slender body at high angles of attack

Two innovative kinds of sliding discharge plasma actuators based on different formation hypotheses of forebody asymmetric vortices are designed using a slender body model. Particle image velocimetry and surface pressure measurements are synchronously used to compare the control effect of antiflow and along-flow sliding discharge actuators for a forebody asymmetric vortex at high angles of attack. The experimental results show that the two kinds of sliding discharge plasma actuators can effectively change the random lateral force caused by the asymmetric vortices, and a better control effect is manifested using the along-flow sliding discharge plasma actuator, which contributes to the approximately linear proportional control of the lateral force. This finding suggests that the convective instability of the forebody vortex system in the leeward region of the slender body has a significant influence on the random lateral forces and moments. Through improving the spatial stability of forebody vortices, the flow control efficiency can be effectively improved. An optimal pulse frequency exists in each of the three actuation modes, but it may vary due to the different geometry configuration of the plasma actuator. In this regard, the research findings will potentially provide technical guidance for improving the efficiency of plasma actuators and understanding the formation mechanism of asymmetric vortices.

Experimental study of multi-stable morphing structures actuated by pneumatic actuation

In this paper, we proposed a new pneumatic actuation method inspired from a soft robot, which could drive the multi-stable carbon fiber-reinforced polymer (CFRP) structure transition among five stable configurations under air pressure. Multi-stable structure was manufactured by the carbon fiber prepreg laid in asymmetrical and anti-symmetric layup methods and stacked at the joint during the preparation process according to the designed scheme. In experiments, multi-stable structures with two different fibers layups were prepared to study the snap-through behaviors. The snap-through process of two kinds of multi-stable structures was investigated by experiment. The parameters used to characterize efficiency of the pneumatic actuator actuating the multi-stable structures, including air pressure and snap time, were measured. The influence of the pneumatic actuator on the curvature of multi-stable structures was discussed by comparing the shape characteristic of multi-stable structures with or without pneumatic actuation, and it showed pneumatic actuator has little effect to the structure. The results demonstrated that the proposed pneumatic actuation could be used to drive multi-stable morphing structure flexibly. The combination of multi-stable laminates develops the function of multiple point bending and shape retention of pneumatic actuation.

Energy Efficiency of Linear Electromagnetic Actuators for Flapping Wing Micro Aerial Vehicles

The development of flapping wing systems has been restricted by high power density requirements, comparatively large forces and the requirement for light weight. The use of linear electromagnetic actuators has had a small presence in the flapping wing literature when compared to other actuator types. This has been due to the high power consumption and low power output of this system when compared to resonant systems. This work assesses linear electromagnetic actuators presented in the literature and demonstrates the performance improvements achieved when the mechanism natural frequency is appropriately tuned. This process shows a reduction of input power consumption to 13% of the original power consumption. This improvement, combined with appropriate power electronic design, can reduce the perceived gap between linear electromagnetic actuators and solid-state actuators.

IoT Utilized Gas-Leakage Monitoring System with Adaptive Controls Applicable to Dual Fuel Powered Naval Vessels/Ships: Development & Implementation

Abstract Leakage of Liquefied Petroleum Gas and Liquified Natural Gas (LPG/LNG) produces hazardous and toxic impact on humans and other living creatures. The authors developed a system to monitor and control the gas leakage concentration. MQ-6 gas sensor is used for sensing the level of gas concentration in a closed volume. To monitor the consequences of environmental changes an IoT platform hosted by “Thingspeak” platform has been introduced. Both robust and cloud-forwarded controls have been applied to prevent uncontrolled leakage of those gases and auto-ignition. This type of system can be directly applied to the engine chamber/ fuel chamber of the modern marine vessels using dual fuel power cycle with LPG/LNG as secondary fuel-flamer. The results from the experiments clearly indicate satisfactory actuation speed and accuracy. The trials performed by the authors showed about 99% efficiency of signal transmission and actuation.

Enhanced Efficiency of Electrostatically Actuated Bistable Microswitches Using Bow-Like Operation

To induce snap-through (ST) switching in an electrostatically actuated bistable latchable curved microbeam, a close gap electrode facing the concave surface of the beam is commonly used. In the framework of an alternative architecture considered here, the electrode is placed in front of the convex (backward), rather than concave (forward) side of a beam. The initially curved stress free beam is activated by an electrostatic force pulling it quasistatically in the backward direction, away from the desired buckled configuration. Once the voltage is turned off , the accumulated strain energy is released, and the beam is catapulted toward the buckled state, similarly to an arrow fired by a bow. In the case where the beam exhibits latching, the device may remain in its buckled state indefinitely under zero voltage. The beam can also be snapped back (released), by applying a voltage to the same electrode. In this article, the efficiency of this bow-like actuation is estimated. By means of a reduced order model, it is shown that due to the nonlinearity of the electrostatic force, the suggested operation scenario may lead to a 54 ${\%}$ reduction in the ST switching voltage, when compared to the traditional forward actuation. As a result, the device allows bidirectional switching by using a single electrode, and can be viewed as a micromechanical realization of a toggle flip-flop element.

Adaptive Neural Fault-Tolerant Control for the Yaw Control of UAV Helicopters with Input Saturation and Full-State Constraints

In this paper, an adaptive neural fault-tolerant tracking control scheme is presented for the yaw control of an unmanned-aerial-vehicle helicopter. The scheme incorporates a non-affine nonlinear system that manages actuator faults, input saturation, full-state constraints, and external disturbances. Firstly, by using a Taylor series expansion technique, the non-affine nonlinear system is transformed into an affine-form expression to facilitate the desired control design. In comparison with previous techniques, the actuator efficiency is explicit. Then, a neural network is considered to approximate unknown nonlinear functions, and a time-varying barrier Lyapunov function is employed to prevent transgression of the full-state variables using a backstepping technique. Robust adaptive control laws are designed to handle parameter uncertainties and unknown bounded disturbances to cut down the number of learning parameters and simplify the computational burden. Moreover, an auxiliary system is constructed to guarantee the pitch angle of the UAV helicopter yaw control system to satisfy the input constraint. Uniform boundedness of all signals in a closed-loop system is ensured via Lyapunov theory; the tracking error converges to a small neighborhood near zero. Finally, when the numerical simulations are applied to a yaw control of helicopter, the adaptive neural controller demonstrates the effectiveness of the proposed technique.

Optimal Fault Tolerant Control of Large-Scale Wind Turbines in the Case of the Pitch Actuator Partial Faults

In this paper, an adaptive fault tolerant control strategy is proposed to deal with the three pitch actuator faults in the large-scale wind turbines. Firstly, a simultaneous state and fault estimation was performed through a suitable LMI (linear matrix inequality) based optimal strategy. Hereafter, the new control law is designed using the previously estimated fault information. The actuator efficiency estimator uses as design parameters, respectively, the performance index γ against the wind and the learning rate Ξ. of the fault estimation algorithm. The study shows that the choice of the previous two parameters impacts the response time of the fault estimation and the correlation of the tracking error with the wind. The aim is to choose a small fault estimation response time while keeping a weak correlation between the tracking error and the wind turbulence noise. Finally, a tuning strategy is elaborated to choose the suitable γ and Ξ to match the reconfiguration objective.

Varying mechanical compliance benefits energy efficiency of a knee joint actuator

In the field of wearable robots, actuator efficiency and user safety are frequently addressed by intentionally adding compliance to the actuation unit. However, the implications compliance has on the actuator’s overall performance in different conditions and activities are not fully understood, largely due to single task-focused experimental evaluations of these devices. To overcome this, our paper analyzes the effects that changing mechanical compliance has on the actuator’s overall performance in different ideal conditions in an experimental test setup. The torque performance and electrical energy consumption of an orthotic, adjustable-compliance knee joint actuator are evaluated during emulated walking and sit-to-stand-to-sit movements. Furthermore, the feasibility of combined operation of a dual mechanical compliance configuration during walking is investigated, and its outcomes reported in this work. The results demonstrate that varying mechanical compliance can lead up to 50% energy savings compared to a no-compliance configuration and show that, in general, changing compliance level leads to either energy-optimal or power-optimal actuator performance, but not both.

Driving Conditions for Improving Jet Induction Efficiency of Plasma Actuator

Driving Conditions for Improving Jet Induction Efficiency of Plasma Actuator

Evaluation of the energy efficiency of a plasma actuator based on an arc discharge in air under the influenceof an external magnetic field

Evaluation of the energy efficiency of a plasma actuator based on an arc discharge in air under the influenceof an external magnetic field

Increase of efficiency of actuators of spacecraft thermal control system in outer space

The article deals with the methods of transfer of thermal energy of electric heaters to the nodes and devices of non-pressurized spacecraft, which are part of the spacecraft in the target orbits in the conditions of regular use. The basic technical characteristics of perspective electric heaters for operating conditions are developed, the model of regular position of electric heaters allowing to define ways of increase of efficiency and efficiency of electric heaters is developed. The main results of the development of flexible film electric heaters various design using materials produced by the domestic industry and manufactured using a new method based on the method of photolithography and etching the resistive layer, allowing to implement new functionality and improve efficiency of electric heaters, the experiments confirming the calculations in conditions simulating operational influences on electric heaters. The using of flexible film electric heaters increased efficiency in the existing and future spacecraft can improve the efficiency of the thermal control system as a whole, improves manufacturability.

Design of a new integrated controller (braking and steering) to maintain the stability of a long articulated vehicle

As demands increase for goods transportation services, long articulated vehicles are introduced as a viable alternative to conventional heavy-duty vehicles. Nowadays, steering control systems are commonly used for enhancing the stability and handling of articulated vehicles. As situations become more difficult for the movement of a vehicle, the ability of the steering actuators decreases and it will not be possible to use this controller alone in critical maneuvers. Another effective way to adjust the directional dynamics of a long articulated vehicle is the simultaneous application of the braking and steering systems. In a situation where the vehicle is close to the ultimate steering limit, it is desirable to reduce the speed, and the steering system can be strengthened through the intervention of the braking system. In this article, a 23 degree of freedom dynamic model of the long articulated vehicle has been developed in MATLAB software. After determining the reference control variables, we will design a sliding mode controller to steer the tractor’s front axle and the semi-trailer’s rear axles. After defining and setting the weight coefficients using a performance indicator, we will design an integrated controller in a way that if maneuvers become more difficult to perform and the efficiency of the steering actuators decreases, the braking forces exerted on the tractor’s rear axle and the semi-trailer’s rear axles will take a share in regulating the vehicle’s movement. The main achievement of this article is the introduction of a new method to integrate braking and steering control systems in long articulated vehicles. The paper aims to prove that only if manoeuvres become more difficult to perform and the performance of steering actuators decreases, then braking forces can take part in regulating the vehicle’s movement.

Bending mechanics of cylindrical skins for morphing aerospace applications

Shape-changing aerospace structures explore the trade-offs between aerodynamic performance and actuation efficiency. Herein, a morphing cylinder is optimized to minimize both its work to actuate in bending as well as radial deviations. Based on derived linear elastic mechanics of a cylindrical shell in bending, it was determined that favorable designs have high circumferential and low axial stiffnesses. We investigate circumferentially reinforced composites that limit radial displacement and allow for out-of-plane bending. Designs of flexible skins with embedded or underlying reinforcement were modeled, fabricated, and compared to unreinforced skins. Finite element analyses predicted the bending kinematics and structural responses. Digital image correlation used during the bending of physical prototypes generated strain contour plots of cylinder surfaces. Strong agreement between model predictions and experimental measurements was observed. The dimensions of each archetype were systematically varied via finite element modeling to obtain a set of nondominated designs capable of 25° of bending without buckling or large radial displacements. For the examined designs, it was determined that flexible skins reinforced with embedded rings were optimal at low (8–15 N·m) and high (>250 N·m) values for the work to articulate while flexible skins reinforced with underlying helical springs were optimal at moderate values (15–250 N·m).

Locking–unlocking mechanism actuated by SMA springs to improve the energy efficiency of fabric-type soft actuators

Wearable robots use batteries as a power source; therefore, the efficiency of the actuation mechanism must be improved to increase their operation time. Soft wearable robots using fabric-type soft actuators (FSA) have attracted much interest recently. In FSAs, the actuator itself is soft, flexible, and lightweight, and energy must be continuously supplied to support the load and hold the actuation state. In particular, when maintaining a particular posture, such as holding an object, constant energy supply is needed to enable the actuator to support the load. To reduce the energy consumption of the holding motion in FSAs, this study proposes a locking–unlocking mechanism (LUM) that can maintain the FSA’s contraction state without sustained energy supply. The LUM is fixed to the FSA’s upper end; it consists of a ratchet-pawl mechanism, pawl rotating actuators (PRA) with shape memory alloy springs, and a wire encoder. The PRA enables the pawl to lock and unlock the ratchet. One end of the wire encoder connected to the ratchet’s rotary shaft is fixed at the bottom part of the FSA, thereby maintaining the FSA contraction state and measuring the contraction length. The LUM’s displacement controller can control the FSA to a specific displacement length. This paper presents the design procedure, operating test, and performance evaluation for energy efficiency improvement of the LUM. When the LUM is applied, FSA can maintain the contraction state while supporting the load, making energy consumption unnecessary. As a result, we expect that applying the LUM with FSAs to soft wearable robots can improve the operation time by at least two times.