Model Of Actuator Research Articles

Modeling and Identification of Electromechanical Actuators for the ILR-33 AMBER Rocket

The aim of the work was to develop a method for modeling, testing, and identifying electromechanical actuators for rocket applications. Works were performed using a prototype solution designed for the ILR-33 AMBER suborbital rocket, developed by Łukasiewicz Research Network – Institute of Aviation. A set of physical relationships was used to create system’s mathematical model, including Kirchhoff’s laws, Newton’s laws, and nonlinear friction models. System’s tests were then performed. A new method of results analysis was applied herein to gather unknown parameters for the model and to confirm an elevated level of convergence between both model and experiment in all cases analyzed. The identification approach proved itself to be effective and useful. A complex approach concerning modeling, testing and identification of such actuators was explained for the first time in this paper. The methods presented herein can be applied in other disciplines, wherever electromechanical actuator systems are used, and where their proper identification is necessary to ensure system reliability and safety. Presented solutions are simple to implement, and the test stands do not require expensive measurement equipment. The results obtained permit to create a high fidelity model at a reasonably low computational cost.

Active Disturbance Rejection Control of Hydraulic Quadruped Robots Rotary Joints for Improved Impact Resistance

Hydraulic actuated quadruped robots have bright application prospects and significant research values in unmanned area investigation, disaster rescue and other scenarios, due to the advantages of high payload and high power to weight ratio. Among these fields, inevitable collision of robots may occur when contact with unknown objects, step on empty objects, or collapse, all of which have an impact on the working hydraulic system. To overcome the unknown external disturbances, this paper proposes an active disturbance rejection control (ADRC) strategy of double vane hydraulic rotary actuators for the hip joints of the quadruped robots. Considering the order of the valve-controlled actuator model, a three-stage tracking differentiator, a four-stage extended state observer, and a state error feedback controller are designed relatively, and the extended state observer is adopted to observe and compensate the uncertainty of external load torque of the system. The effectiveness of the ADRC method is verified in simulation environment and a single joint experimental platform. Moreover, the impact experiments of the limb leg unit are carried out after introducing the proposed ADRC strategy into hip joint, the limb leg unit of quadruped robots presents better impact resistance ability.

Compound Model of Twisted and Coiled Polymer Actuators Describing Relationship Between Output Force and Excitation Current

Compound Model of Twisted and Coiled Polymer Actuators Describing Relationship Between Output Force and Excitation Current

Clamping Force Control of Electromechanical Brake Actuator Considering Contact Point between Friction Lining and Brake Disc

Currently, most electromechanical brake (EMB) schemes are only suitable for passenger cars, and their maximum clamping force is insufficient to satisfy the braking demands of commercial vehicles. Additionally, previous studies on clamping force control are largely based on an EMB equipped with sensors. Due to constraints in installation space and cost, sensorless EMBs are gradually gaining attention. Furthermore, accurately identifying the contact point between the friction lining and the brake disc is the promise of clamping force control for sensorless EMBs. Hence, a sensorless EMB scheme suitable for commercial vehicles is proposed in this study. Secondly, a dynamics model of the EMB actuator is established. After a comprehensive analysis of the proposed EMB actuator, a clamping force control strategy considering the contact points between the friction lining and the brake disc is proposed. Finally, simulation analyses of the strategy are carried out. The results show that the axial length of the proposed EMB actuator is shortened by 17.6% compared with a mainstream pneumatic disc brake. Furthermore, the proposed method can accurately identify the contact points between the friction lining and the brake disc, and the proposed control strategy enables the EMB actuator to achieve the fast response, accurate tracking, and stable maintenance of the target clamping force.

Modeling and compensation of a hollow XY stage based on hybrid reluctance actuators

In the field of beam pointing and optoelectronic imaging, there is a growing demand for control mechanisms that offer large stroke, and high bandwidth. These are precisely the characteristics of hybrid reluctance actuator, which therefore is increasingly being used in XY stage to replace piezo-actuator and voice coil motor. This study presents a hollow XY stage utilizing hybrid resistance actuators, aiming to adapt to optical applications with inherent nonlinearity and biaxial coupling, which are further modeled and compensated to mitigate their impacts. Firstly, the basic composition and working principle of the hollow XY stage are described, and the impact of its nonlinearity and biaxial coupling characteristics is elucidated. Secondly, the sources of nonlinearity and biaxial coupling are analyzed, and an analytical model of hybrid reluctance actuators is established. The magnetic leakage coefficient of the model is determined, and the accuracy of the model is verified by Finite Element Method (FEM) and experiment, demonstrating consistency with the analytical model's results. Furthermore, based on the nonlinear and biaxial coupling model, a compensator based on feedback linearization method is established, and verified through experiment. The results show that this method has a significant suppression effect on nonlinear and biaxial coupling, and the tracking error and cross-talk is obviously reduced, which proves the effectiveness of this compensation method.

Thermal effect on the flow induced by a single-dielectric-barrier-discharge plasma actuator under steady actuation

The thermal effect of a single-dielectric-barrier-discharge plasma actuator under steady actuation is numerically investigated. A new actuator model is proposed and validated using experimental data. A discrete Galerkin method based on high-order flux reconstruction schemes is employed to solve the flow governing equations and the actuator model equations on unstructured quadrilateral grids. By comparing the induced heated and cold flow fields of the actuator with and without a plasma thermal source, its thermal effect is revealed. The actuator generates a thermal wall jet with rich vorticity, forming a monopolar starting vortex with a high-temperature and low-density core. Over time, the starting vortex becomes unstable and transforms into a dipole. Actuator heating enhances jet velocity and width, as well as vortex stability, while slowing down vorticity generation. The relative change in density and temperature fields due to actuator heating is four orders of magnitude greater than that without actuator heating. Additionally, the actuator heating causes the background thermodynamic fields to increase approximately linearly with time. Two stages in the actuator's thermal effect are distinguished due to time accumulation. Initially, the actuator heating minimally affects the monopolar starting vortex motion, and the temperature and density fields are treated as passive variables driven by the velocity field. During this stage, the momentum and thermal effects of the actuator can be studied separately. However, after the starting vortex becomes unstable, the actuator heating significantly impacts its motion and morphology, and these two effects are coupled with each other.

Variable stiffness performance analysis of layer jamming actuator based on bionic adhesive flaps

Soft actuators made of soft materials cannot generate precisely efficient output forces compared to rigid actuators. It is a promising strategy to equip soft actuators with variable stiffness modules of layer jamming mechanism, which could increase their stiffness as needed. Inspired by the gecko's the array of setae, bionic adhesive flaps with inclined micropillars are applied in layer jamming mechanism. In this paper, after the manufacturing process of the layer jamming actuator based on the bionic adhesive flaps is described, the equivalent stiffness models of the whole actuator are established in the unjammed and jammed states. And the shear adhesive force of a single micropillar is calculated based on the Kendall viscoelastic band model. The finite element simulation results of two bionic adhesive flaps show that the interlaminar shear stress and stiffness increase with the increase of pressure. The measurement of shear adhesive force show that the critical shear adhesive force of the bionic adhesive material is 3.2 times that of polyethylene terephthalate (PET) material, and exhibit the ability of anisotropic adhesion behavior. The variable stiffness performance of the layer jamming actuator based on bionic adhesive flaps is evaluated by three test methods, and the max stiffness reaches 8.027 N mm-1, which is 1.5 times higher than the stiffness of the layer jamming actuator based on the PET flaps. All results of simulation and experiment effectively verify the validity and superiority of applying the bionic adhesive flaps to the layer jamming mechanism to enhance the stiffness.

Conversion of a Coaxial Rotorcraft to a UAV—Lessons Learned

A coaxial helicopter with a maximum take-off weight of 600 kg was converted to an unmanned aerial vehicle. A minimally invasive robotic actuator system was developed, which can be retrofitted onto the copilot seat of the rotorcraft in a short period of time to enable automatic flight. The automatic flight control robot includes electromechanical actuators, which are connected to the cockpit inceptors and control the helicopter. Most of the sensors and avionic components were integrated into the modular robotic system for faster integration into the rotorcraft. The mechanical design of the control system, the development of the robot control software, and the control system architecture are described in this paper. Furthermore, the multi-body simulation of the robotic system and the estimation of the linear low-order actuator models from hover-frame flight test data are discussed. The developed technologies in this study are not specific to a coaxial helicopter and can be applied to the conversion of any crewed flight vehicle with mechanical controls to unmanned or fly-by-wire. This agile development of a full-size flying test-bed can accelerate the testing of advanced flight control laws, as well as advanced air mobility-related functions.

Modeling and Control of a Road Wheel Actuation Module in Steer-by-Wire System

Since the steer-by-wire system removes the mechanical connection and uses electrical signals to drive the system, it has the disadvantage of being less stable in the failure of parts or systems. Therefore, in this paper, we present a methodology for developing a digital model of the road wheel actuator of the steer-by-wire system. First, the detailed dynamics of the road wheel actuator are analyzed and simplified, and the friction model is estimated and compensated to obtain the equilibrium inertia and damping coefficient of the motor and the road wheel actuator. And to verify the accuracy of the digital model developed based on these parameters, the outputs are compared by giving the same inputs under open-loop control. Furthermore, to solve the problem caused by nonlinear disturbance and model uncertainty, a disturbance observer-based position controller is proposed. The validity of the proposed controller and the validity of the digital model development methodology are confirmed by the results of the position control experiment.

Stability of Single-Channel Homing Rolling Aerospace Vehicle

This paper aims to analyze the stability of a special class of single-channel slow-rotating homing missiles using the Frank–Wall stability criterion. To achieve this, starting from the model of a slow-rolling missile with six degrees of freedom (6 DOFs) in the body frame, a 6-DOFs model in the Resal frame is obtained, which is used to linearize the coupled commanded motion. Based on the linearized model, we obtain the structural scheme of the commanded object and define the flight quality parameters. The obtained linear model has a complex representation (with real and imaginary parts) due to the coupling between longitudinal channels for the rolling missile. Then, the kinematic guidance equations, the seeker equations and the actuator relations using a switching function, specific to the slow-rolling single-channel missile, are defined. The guidance kinematic equations, the seeker equations and the actuator model are linearized in the Resal frame, and the structural diagram of the homing missile is constructed. Starting from this, the characteristic polynomial having complex coefficients is determined and then analyzed with the Frank–Wall stability criterion. Based on the analysis, a stability range is determined for the navigation constant (k), and a minimum and possibly a maximum limit for the time to hit the target tgo is obtained. The stability range defined for the navigation constant in the linear model is finally validated in the nonlinear model in the body frame.

A bionic robotic ankle driven by the multiple pneumatic muscle actuators

The traditional pneumatic muscle robot joint has weak load capacity and low control precision. This paper proposes a bionic robotic ankle driven by multiple pneumatic muscle actuators. The structural design of the bionic robotic ankle and the drive mechanism that imitates human muscle recruitment are introduced. A dynamic model of the ankle and a static model of the pneumatic muscle actuator are established to analyze the driving characteristics. The multi-muscle recruiting strategy and load matching control method are optimized, and the output characteristics are simulated, including the robotic ankle driven by a single pneumatic muscle actuator, the robotic ankle driven by dual pneumatic muscle actuators, and the bionic ankle driven by multiple pneumatic muscle actuators. A prototype and testing platform are developed, and experimental research is carried out to validate the theoretical analysis and simulation. The results show that the bionic robotic ankle driven by multiple pneumatic muscle actuators can match varied loads, effectively reducing angle error and increasing output force.

A learning-based nearly optimal control framework for trajectory tracking of a flexible-link manipulator system with actuator fault

In this paper, a learning-based nearly optimal control framework with fault-tolerant capability is designed to tackle the tracking control problem of a flexible-link manipulator in the presence of actuator fault and model uncertainties. Initially, the optimal control law is obtained by adopting the dynamic programming and a critic structure as the solution of Hamilton–Jacobi–Bellman equation for the nominal model. Then, by implementing an integral sliding mode control, the robustness against actuator fault and model uncertainty is guaranteed. The adaptive laws are constructed based on radial basis functions neural networks to estimate the upper bound of uncertainty and the actuator bias fault, satisfying both optimal performance and chattering reduction of the sliding surface. Furthermore, the actuator effectiveness loss is handled. The stability of the closed-loop system is analytically proven, and the performance of the proposed framework is investigated against several practical operating conditions. This incorporates the fidelity assessment of tracking precision and trackability of control signal using performance indices such as the integral absolute error and root-mean-square error. The results of extensive simulation studies confirm the effectiveness and robustness of the proposed control framework.

Hybrid dynamical modeling of shape memory alloy actuators with phase kinetic equations

Shape memory alloy morphing actuators are a type of composite soft actuator with many attractive properties such as large deformation, small form factor, self-sensing ability, and physical reservoir computing potential. These actuators are composed of active shape memory alloy wires and a passive material to magnify the overall deflection. However, the dynamic modeling of these actuators is difficult due to both shape memory alloy characteristics and the nonlinearity of the passive layer. Here, a hybrid dynamical model is proposed that couples the phase kinetics and thermal modeling for the shape memory alloy with a dynamic Cosserat beam model. This hybrid model is benchmarked against experimental linear and morphing actuators resulting in a root mean squared error of 0.87 mm for the linear actuator and root mean squared error of 1.34 and 1.42 mm for the two morphing actuator configurations evaluated in this work. This model applies continuous phase kinetic equations in a comprehensive hybrid dynamical model to accurately simulate the hysteretic transition of the alloy, which is then coupled to a high deformation beam model. This work can expand the capability and design of novel morphing actuators to achieve specified dynamic characteristics for increased application in robotic fields.

Structural Optimization of a Giant Magnetostrictive Actuator Based on BP-NSGA-II Algorithm

This study introduces an integrated structural optimization design method based on a BP neural network and NSGA-II multi-objective genetic algorithm. Initially, a two-dimensional axisymmetric finite element model of the Giant Magnetostrictive Actuator (GMA) was established, and the coupling simulation of the electromagnetic field, structural field, and temperature field was conducted to obtain the GMA’s performance parameters. Subsequently, the structural parameters of the GMA magnetic circuit, including the magnetic conducting ring, magnetic conducting sidewall, magnetic conducting body, and coil, were used as inputs, and the axial magnetic induction intensity, uniformity of axial magnetic induction intensity, and coil loss on the Giant Magnetostrictive Material (GMM) rod were used as outputs to establish a back propagation (BP) neural network model. This model delineated the nonlinear relationship between structural parameters and performance parameters. Then, the BP-NSGA-II algorithm was applied to perform multi-objective optimization on the actuator’s structural parameters, resulting in a set of Pareto optimal non-dominated solutions, from which a set of optimal solutions was obtained using the entropy weight method. Finally, simulation analysis of this optimal solution was conducted, indicating that under a 5 A power supply excitation, the maximum axial magnetic induction intensity on the optimized GMM rod increased from 0.87 T to 1.12 T; the uniformity of axial magnetic induction intensity improved from 93.1% to 96.5%; and the coil loss decreased from 7.79 × 104 W/m3 to 4.97 × 104 W/m3. Based on the optimization results, a prototype actuator was produced, and the test results of the prototype’s output characteristics proved the feasibility of this optimization design method.

ANCF-based dynamic modeling of variable curvature soft pneumatic actuators with experimental verifications

Accurate and computationally efficient models of soft pneumatic actuators are crucial for utilizing their compliance in various fields. However, existing research primarily relies on the piecewise constant curvature assumption or the quasi-static assumption, only valid in limited situations. In this paper, we present a dynamic model based on absolute nodal coordinate formulation (ANCF) that simultaneously accounts for variable curvature deformation and dynamic properties. To this end, deformed configurations of soft pneumatic actuators are firstly discretized into ANCF-based beam elements. Based on this parameterization method, the dynamic model is derived by the principle of virtual work. After identifying model parameters, Newmark algorithm is utilized to solve the dynamic model in real-time, averagely consuming 6.76 s of a 10 s simulation. The derived dynamic model is experimental verified using a soft pneumatic actuator. The experimental results demonstrate that the maximum simulation errors of the tip remain below 2.5% of the actuator’s length when the actuator is subjected to various pressure and tip loads. In addition, the overshoot behavior and period of vibration in the oscillations are also predicted by the dynamic model. Moreover, the dynamic model exhibits an average 46.53% reduction in simulation error compared with the static ANCF-based model. Overall, this work paves the way to a deeper insight to dynamic motion analysis of soft pneumatic actuators.

Efficient computation of horizontal stabilizer incidence angle for low pitching moments based on actuator model

Efficient computation of horizontal stabilizer incidence angle for low pitching moments based on actuator model

Hysteresis modeling of piezoelectric actuators based on neural network considering load and environmental stiffness

Hysteresis modeling of piezoelectric actuators based on neural network considering load and environmental stiffness

Development and testing of a discrete coil magnetostrictive actuator

Active combustion control (ACC) technology is an effective measure for suppressing the combustion oscillation of aero-engines. The magnetostrictive actuator is the most suitable choice for the ACC actuator due to its excellent high-frequency characteristics and high-temperature resistance. In order for the magnetostrictive actuator to produce high-frequency displacement, the constant current driver must have sufficient power, which results in a larger mass of the driver. A solution is to use multi-channel and low-power constant current driver. Therefore, the coil of the magnetostrictive actuator is axially dispersed and driven by two four-channel servo amplifiers. The driver’s mass is significantly reduced while maintaining the same electromagnetic conversion effect. In addition, an analytical model of a discrete coil magnetostrictive actuator is established, and a series of experiments are conducted. The maximum hysteresis error of output displacement at 200 Hz is reduced by 15.2%. Furthermore, under PID closed-loop control, the root mean square (RMS) error is less than 2% when tracking a 10 Hz sinusoidal displacement with coil switching drive.

Tear Fracture Analysis of Fiber-Reinforced Conducting Polymer-based Soft Actuator

Conducting polymer (CP) is an electroactive polymer that displays specific electronic properties, including conductivity. The utility of CP-based soft actuators in various biomedical applications has recently been motivated due to their low voltage-driven specialty compared to the widely used high voltage-driven dielectric elastomers. In some biomedical applications, highly delicate CP actuators may be torn or damaged for unknown reasons. In this regard, this study develops a tear fracture model for fiber-reinforced CP actuators to investigate a specific fracture test of mode III, namely, the trousers test, which involves pulling two legs of a cut specimen horizontally apart. The development of the tear fracture model adopts a well-known Griffith criterion along with the thermodynamically consistent continuum mechanics approach. Additionally, prominent strain energy capturing elastomer strain-stiffening at a moderate strain range is used in conjunction with an empirically established correlation to couple the two internal phenomena, ion diffusion and mechanical deformation of the CP actuators. Later, the effects of various electrical and geometrical parameters on the tearing of the actuator are also addressed.

Research on DSP-based data model identification and triple-loop PID control of electro-hydraulic actuators

This paper focuses on the electro-hydraulic actuator of a certain type of aircraft, detailing the DSP-based hardware structure and principles. The study utilizes data acquisition and data model identification to establish a second-order model for the electro-hydraulic actuator. Verification sets and mean squared error (MSE) calculations, with an MSE value of 0.0110, indicate a reasonable identification model. Subsequently, a controller design structure is proposed based on the identified model. Finally, simulations validate the identified model and the triple-loop PID control. Experimental results show that the system's sine response output amplification factor is 0.9242.