Active Actuators Research Articles

Implications of dragonfly's muscle control on flapping kinematics and aerodynamics

In this work, we designed and characterized a passive structural wing actuation setup that was able to realistically mimic the flapping and pitching kinematics of dragonflies. In this setup, an inelastic string limited the wing pitch that may be sufficiently simple for practical micro air vehicle applications. To further evaluate the dominance of inertial passive and active muscle-controlled pitch actuation in dragonfly flight, the flow fields and pitching angle variations of the naturally actuated wing of a tethered dragonfly were compared with that of the same wing artificially actuated via a proposed passive mechanism. We found that passive rotation characterizes most of the forewing flapping cycle except the upstroke reversal where the dragonfly uses its muscle movement to accelerate its forewing rotation. The measured flow fields show that accelerated wing rotation at the upstroke reversal will result in a stronger leading edge vortex during the downstroke, the additional force from which is estimated to account for 4.3% of the total cycle averaged force generated.

Design of a Compact Energy Storage with Rotary Series Elastic Actuator for Lumbar Support Exoskeleton

Lumbar support exoskeletons with active and passive actuators are currently the cutting-edge technology for preventing back injuries in workers while lifting heavy objects. However, many challenges still exist in both types of exoskeletons, including rigid actuators, risks of human–robot interaction, high battery consumption, bulky design, and limited assistance. In this paper, the design of a compact, lightweight energy storage device combined with a rotary series elastic actuator (ES-RSEA) is proposed for use in a lumbar support exoskeleton to increase the level of assistance and exploit the human bioenergy during the two stages of the lifting task. The energy storage device takes the responsibility to store and release passive mechanical energy while RSEA provides excellent compliance and prevents injury from the human body’s undesired movement. The experimental tests on the spiral spring show excellent linear characteristics (above 99%) with an actual spring stiffness of 9.96 Nm/rad. The results demonstrate that ES-RSEA can provide maximum torque assistance in the ascent phase with 66.6 Nm while generating nearly 21 Nm of spring torque during descent without turning on the DC motor. Ultimately, the proposed design can maximize the energy storage of human energy, exploit the biomechanics of lifting tasks, and reduce the burden on human effort to perform lifting tasks.

Sound transmission through a panel with a hybrid active and semi-active control system

Semi-active control systems require significantly less energy than active solutions, while still providing substantial performance. However, active and semi-active systems can be applied in conjunction as hybrid systems, exploiting both solutions and providing high performance and reduced energy consumption. This paper proposes the use of such a hybrid active/semi-active control system for noise reduction barriers. Accounting for time-varying narrow-band noise, active structural acoustic control (ASAC) guarantees enhanced transmission loss for a noise barrier. Simultaneously, a semi-active element with a tunable mass moment of inertia allows the system to adapt to noise with varying characteristics by altering the mechanical properties of the barrier. Obtained control results demonstrate that the addition of a semi-active element is more effective than an additional active control actuator for reducing sound power in targeted frequency bands. Moreover, the proposed hybrid system may operate in two modes, allowing to further reduce overall energy consumption.

Smart textiles using fluid-driven artificial muscle fibers

The marriage of textiles with artificial muscles to create smart textiles is attracting great attention from the scientific community and industry. Smart textiles offer many benefits including adaptive comfort and high conformity to objects while providing active actuation for desired motion and force. This paper introduces a new class of programmable smart textiles created from different methods of knitting, weaving, and sticking fluid-driven artificial muscle fibers. Mathematical models are developed to describe the elongation-force relationship of the knitting and weaving textile sheets, followed by experiments to validate the model effectiveness. The new smart textiles are highly flexible, conformable, and mechanically programmable, enabling multimodal motions and shape-shifting abilities for use in broader applications. Different prototypes of the smart textiles are created with experimental validations including various shape-changing instances such as elongation (up to 65%), area expansion (108%), radial expansion (25%), and bending motion. The concept of reconfiguring passive conventional fabrics into active structures for bio-inspired shape-morphing structures is also explored. The proposed smart textiles are expected to contribute to the progression of smart wearable devices, haptic systems, bio-inspired soft robotics, and wearable electronics.

Design and Validation of a Cable-Driven Asymmetric Back Exosuit

Lumbar spine injuries caused by repetitive lifting rank as the most prevalent workplace injury in the United States. While these injuries are caused by both symmetric and asymmetric lifting, asymmetric is often more damaging. Many back devices do not address asymmetry, so we present a new system called the Asymmetric Back Exosuit (ABX). The ABX addresses this important gap through unique design geometry and active cable-driven actuation. The suit allows the user to move in a wide range of lumbar trajectories while the “X” pattern cable routing allows variable assistance application for these trajectories. We also conducted a biomechanical analysis in OpenSim to map assistive cable force to effective lumbar torque assistance for a given trajectory, allowing for intuitive controller design in the lumbar joint space over the complex kinematic chain for varying lifting techniques. Human subject experiments illustrated that the ABX reduced lumbar erector spinae muscle activation during symmetric and asymmetric lifting by an average of 37.8% and 16.0%, respectively, compared to lifting without the exosuit. This result indicates the potential for our device to reduce lumbar injury risk.

Analysis and optimized design of an actively controlled two-dimensional delayed resonator

The absorption properties and active actuation of two-dimensional delayed resonators (2D-DR) are studied from various aspects. For a general 2D-DR, the actuation forces and energy supply needed for entire vibration absorption of a platform excited by a periodic force and torque are determined. For this purpose, a model describing the full absorber-platform dynamics is transformed into a form that allows to express the relevant design quantities as a function of the absorber’s parameters only. Subsequently, the parameters of the 2D-DR absorber, specifically the stiffness and damping of the connecting links, are optimized to turn the underlying three degree of freedom problem to a one degree of freedom problem. For this configuration, the stability and robustness in vibration absorption are studied. Based on the performed analysis, design rules are specified for the optimized 2D-DR design, including its positioning on the vibrating platform. A numerical case study demonstrates the 2D-DR absorber design and assessment of the operable frequency range for a specific set of voice-coil actuators.

Research and modeling of force fighting equalisation for aircraft rudder’s triple active actuation system

AbstractThis paper presents a new approach to force fighting equalisation in a redundant active-active-active rudder actuation system that is used for the primary flight control system of a turboprop regional aircraft. The related coupled problem of force fighting scenario, and the hydraulic architecture of electronic-hydrostatic actuator (EHA) are analysed, the mathematical model of the EHA system is built. The virtual test bench is designed to evaluate the performance of the force fighting equalisation strategy. The proposed methodology is tested on an iron bird test rig. The physical experiment shows that the fighting force is minimised under all flight conditions, meets the low cost requirement and can be a very reliable system. The proposed methodology can be applied to other types of aircraft’ flight actuation systems.

Active Load Sensitive Electro-Hydrostatic Actuator on More Electric Aircraft: Concept, Design, and Control

Electro-hydrostatic actuator (EHA) is a type of actuator in more electric aircraft, which is a highly integrated local volume control hydraulic actuator, and can improve the reliability and efficiency. However, the motor heating can hardly be taken out due to the feature of the local closed hydrostatic system, especially under heavy load. In order to solve the problem, direct load sensitive EHA is an effective way to reduce heat, but the dynamic performance is inevitably sacrificed. To achieve the targets of both low heat generation and high dynamic response, a novel active load sensitive EHA (ALS) is proposed in this article. The key characteristic of ALS is that a special pressure following valve (PFV) is added between the load sensitive pressure point and the actuator of the swash plate in the pump. Furthermore, the PFV is actively controlled to adjust the load sensitive pressure. Based on this concept, detailed analysis and design of the system are presented. Following, the load sensitivity is controlled based on the fuzzy algorithm and the main loop is controlled by traditional proportional−integral differential. Finally, compared with the results of simulation and experiments, ALS can effectively reduce motor heating and maintain high dynamic performance, simultaneously.

Comparison the Hydraulic Harvested Energy with the Electromagnetic Systems and the Spent Energy on the Active System

An energy-harvesting hydraulic regeneration suspension system is described in this article, which includes a hydraulic motor, a spool valves, and a hydraulic cylinder. Regenerative actuators are built using a hydraulic transmission system as their inspiration. The proposed regenerative actuator is implemented in the vehicle's non-linear suspension system for a complete model. MATLAB Simulink is utilized to generate and simulate the entire vehicle's regenerative suspension system, which has force properties which are nonlinear with hydraulic actuators equations with energy harvesting from regenerative actuators. During the mathematical simulation, the effect of pressure differential on the spool valve's operation is also taken into account. The quantity of captured energy is compared to the energy expended on the active actuator and the energy generated with the electromagnetic actuator at three distinct input signals at three different pressure level (10, 30 and 50 bars) (random, sinusoidal, and square). The energy generated in the regenerative hydraulic actuator at three pressure levels behaves the same as the active actuator in terms of response, plus the highest pressure of 50 bar is closely comparable to the active system in terms of energy harvest and gradually decreases as the output pressure drops in addition to the behavior of the electromagnetic and its comparison with the wasted energy of the active system.

Displacement Sensing of an Active String Actuator Using a Step-Index Multimode Optical Fiber Sensor.

A thin McKibben artificial muscle is a pneumatic actuator with an outer diameter of only 1.8 mm. We fabricated a string-shaped actuator called an “active string actuator,” which achieves a high contractile displacement by accumulating thin McKibben artificial muscles. To control the displacement, the length of the active string actuator should be estimated. However, this is difficult because bulky and rigid sensors are unsuitable for the sensor element of the active string actuator. Therefore, in this study, we propose a new sensing method for estimating the length of an active string actuator. The proposed sensing system is simple and comprises only three components: a step-index multimode optical fiber, a light emitter, and a light receiver. A step-index multimode optical fiber was combined with the active string actuator, and the length was estimated from the change in the amount of light propagating in the optical fiber when the active string actuator was driven. Fundamental experiments were conducted in this study, and the results demonstrated that the optical fiber sensor value changed with the actuator length. This suggests that it is possible to estimate the displacement of an active string actuator using an optical fiber sensor.

Open-channel microfluidics via resonant wireless power transfer

Open-channel microfluidics enables precise positioning and confinement of liquid volume to interface with tightly integrated optics, sensors, and circuit elements. Active actuation via electric fields can offer a reduced footprint compared to passive microfluidic ensembles and removes the burden of intricate mechanical assembly of enclosed systems. Typical systems actuate via manipulating surface wettability (i.e., electrowetting), which can render low-voltage but forfeits open-microchannel confinement. The dielectric polarization force is an alternative which can generate open liquid microchannels (sub-100 µm) but requires large operating voltages (50–200 VRMS) and low conductivity solutions. Here we show actuation of microchannels as narrow as 1 µm using voltages as low as 0.5 VRMS for both deionized water and physiological buffer. This was achieved using resonant, nanoscale focusing of radio frequency power and an electrode geometry designed to abate surface tension. We demonstrate practical fluidic applications including open mixing, lateral-flow protein labeling, filtration, and viral transport for infrared biosensing—known to suffer strong absorption losses from enclosed channel material and water. This tube-free system is coupled with resonant wireless power transfer to remove all obstructing hardware — ideal for high-numerical-aperture microscopy. Wireless, smartphone-driven fluidics is presented to fully showcase the practical application of this technology.

ИССЛЕДОВАНИЕ АЛГОРИТМА СНИЖЕНИЯ ВЗАИМОНАГРУЖЕНИЯ ДВУХ ПРИВОДОВ, ОДНОВРЕМЕННО УПРАВЛЯЮЩИХ АЭРОДИНАМИЧЕСКИМ РУЛЕМ МАГИСТРАЛЬНОГО САМОЛЕТА

Some civil aircraft assume two actuators simultaneously turning aside the flight control surface(rudder, in some cases aileron or elevator). Thus resulting in onset of the force fighting (mutualloading force). There are several ways to reduce the mutual loading force. One of them is to insertspecific force equalization algorithm in actuators steering. This article deals with effectiveness offorce equalization algorithm as well as its influence on system “2 active actuators - elevator”. Mathematic model of two actuators on elevator has been formed and tested by the developed testing methodthat reproduces the most severe operation conditions. There are several nonlinearities which iscontained in mathematic model: sleeve-travel physical limits, nonlinear effects of fluid foil, rod-travelphysical limits and attachment rigidity. Force equalization algorithm comprises a pressure differentialfeedback loop with PID regulator. The results show that force equalization algorithm is highlyefficient (mutual loading force has been reduced over than 90%) in mode test without external load.However, in test mode with external load it is necessary to introduce a limitation on the magnitude ofthe corrective signal so as decrease the rod drop to level specified in terms of reference. Algorithmhas no effect on stability margin of the system. In conclusion, results of this study could also be usefulto expand the test program for two actuators simultaneously turning aside the flight control surfacesto further simplify the implementation of the force equalization algorithm.

Study on a Fault Mitigation Scheme for Rub-Impact of an Aero-Engine Based on NiTi Wires.

The aim of this study was to solve the frequently occurring rotor-stator rub-impact fault in aero-engines without causing a significant reduction in efficiency. We proposed a fault mitigation scheme, using shape memory alloy (SMA) wire, whereby the tip clearance between the rotor and the stator is adjusted. In this scheme, an acoustic emission (AE) sensor is utilized to monitor the rub-impact fault. An active control actuator is designed with pre-strained two-way SMA wires, driven by an electric current via an Arduino control board, to mitigate the rub-impact fault once it occurs. In order to investigate the feasibility of the proposed scheme, a series of tests on the material properties of NiTi wires, including heating response rate, ultimate strain, free recovery rate, and restoring force, were carried out. A prototype of the actuator was designed, manufactured, and tested under various conditions. The experimental result verifies that the proposed scheme has the potential to mitigate or eliminate the rotor-stator rub-impact fault in aero-engines.

Multicyclic Vibration Control of a Helicopter Rotor with Active Twist Actuation

Multicyclic Vibration Control of a Helicopter Rotor with Active Twist Actuation

Design, Parameter Optimisation, and Performance Analysis of Active Tuned Inerter Damper (TID) Suspension for Vehicle

The inherent inertia of active actuators can adversely affect the performance of vehicle suspension systems, which has been a long-standing problem in suspension design. To overcome this problem, an active tuned inerter damper (TID) suspension is designed based on a combination of an active actuator and an inerter, merging the inherent inertia of the former into the inertia of the latter. However, several parameters are involved in active TID suspension, requiring much time and resource to optimise via numerical method. Based on the H2-norm of a quarter-car model, an analytical-solution-based parameter optimisation method that simplifies the process of obtaining the optimal suspension parameters is proposed. Stability analysis is performed algebraically using the Hurwitz criterion, verifying that the parameters obtained using this method can ensure the stability of the suspension. The advantages of active TID suspensions are demonstrated via performance comparison against a variety of suspensions. The results show that the active TID suspension can change the actuator inertia from a harmful to a favourable factor, greatly improve the ultimate capacity of the suspension, and improve vehicle comfort without changing the tire load.

Fault-tolerant control for nonlinear offshore steel jacket platforms based on reinforcement learning

In this article, reinforcement learning based fault-tolerant control for the nonlinear offshore platform is studied. First, the dynamic model of the nonlinear steel-jacket offshore platform with active mass damper and actuator fault is investigated then an affine nonlinear representation for the offshore platform is obtained. By estimating actuator fault and irregular wave force and inserting their estimation into the cost function, the disturbance control and fault-tolerant control problem (FTC) are converted into optimal control problem. Online policy iteration is used to minimize the performance index. Finally, simulation results show the effectiveness of our method.

Ionically Active MXene Nanopore Actuators.

Reversible electrochemical intercalation of cations into the interlayer space of 2D materials induces tunable physical and chemical properties in them. In MXenes, a large class of recently developed 2D carbides and nitrides, low intercalation energy, high storage capacitance, and reversible intercalation of various cations have led to their improved performance in sensing and energy storage applications. Herein, a coupled nanopore-actuator system where an ultrathin free-standing MXene film serves as a nanopore support membrane and ionically active actuator is reported. In this system, the contactless MXene membrane in the electric field affects the cation movement in the field through their (de)intercalation between individual MXene flakes. This results in reversible swelling and contraction of the membrane monitored by ionic conductance through the nanopore. This unique nanopore coupled to a mechanical actuation system could provide new insights into designing single-molecule biosensing platforms at the nanoscale.

Coordinated Compensation Between Active and Semi-Active Actuators for Suspension Control System

This paper presents coordinated compensation schemes between active and semi-active actuators in suspension control system. Generally in active suspension systems, active actuators have been adopted to generate a control force calculated by a controller. However, active actuators adopted in actual vehicles have physical constraints such as maximum force, bandwidth and force-velocity limitation. On the other hand, a semi-active actuator can be a good alternative to active one in view of maximum force and bandwidth despite it cannot generate an active control force. However, the performance of semi-active actuators is limited by half of active ones. Hence, it is necessary to compensate the control force of semi-active actuators by active ones. In this paper, it is assumed that a vehicle has both of active and semi-active actuators. A control force needed to enhance ride comfort is generated by linear quadratic regulator (LQR). The controller is designed with 2-DOF quarter-car model and applied into 7-DOF full-car one. To generate the control force with active and semi-active actuators, several coordinated compensation schemes are proposed. A simulation on a simulation package show that the proposed coordinated compensation schemes are effective in reducing the control force of the active actuator over the wider range of frequencies.

Study and design of an active magnetorquer actuator model for nanosatellites

This paper focuses on the study and the design of an air core magnetorquer model dedicated to the 1U CubeSat (10×10×10 cm3). The objective is to obtain a solution which is able to provide accurate attitude control while having the smallest possible dimensions, electrical power, and total mass. To this end, the first part will provide theoretical mathematical knowledge on the laws of the coil to design an electromagnetic air core actuator. Then, this paper presents comparisons of the performances obtained by varying the type of material and the shape of the coil. Towards the end, the effect of temperature variation in LEO orbit is taken into consideration to predict the generated magnetic moment.

Pseudo‐active actuators: A concept analysis

AbstractThe superior performance of active vibration control systems largely depends on the four‐quadrant controllable execution capability in the available force‐velocity diagram of active actuators. Although semi‐active vibration control systems have the advantages of low energy consumption, simple structure, and high reliability, the system performance is not comparable to active control systems, due to the partial capability in only the first and third quadrants. On the basis of the comprehensive advantages of active and semi‐active actuators, to reform the design philosophy of semi‐active actuators to realize pseudo‐active actuators that have both mechanical properties of active actuators and energy consumption advantages of semi‐active actuators, that is, new semi‐active actuators with four‐quadrant controllable execution capability, will very likely cause a revolution in the related fields of mechanical design and system control. The basic design principle of pseudo‐active actuators that use semi‐active controllable actuators to achieve active actuator performance in the way of conceptual analysis is proposed. The proposed pseudo‐active actuators should consist of two half‐four‐quadrant actuators, that is, one is for the first and third quadrants and the other one for the second and fourth quadrants. This study employs two semi‐active controllable damping actuators and one mechanical compensation mechanism. One of the actuators provides the damping force in the first and third quadrants, and the other one combining with the mechanical compensation mechanism is for the second and fourth quadrants. A global mathematical model of the proposed actuator is established to describe the four different operational modes of the proposed actuator. It is proved that the two operational modes of the proposed actuator can realize active vibration control, and a case study of realizing active control is presented. The other two operational modes are compared with the conventional two‐degree‐of‐freedom model. More specifically, the application cases of the pseudo‐active operational mode of the proposed actuator in the quarter‐car/body‐powertrain suspension system are given, a pseudo‐active suspension named dual‐hook automobile suspension is presented. Furthermore, an equivalent expression of the electrical network is given for the mechanical network under different operational modes of the proposed actuator.