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There has been significant interest in the field of bio-inspired robotics, particularly in the development of flapping-wing robots from micro to bird size. Most flapping robots use lever-crank mechanisms or servomotors as wing flapping mechanisms. Servomotor-based flapping has the advantage of being able to generate various flapping patterns according to amplitude, offset, frequency, waveform, and other factors. However, it is not clear how these factors affect thrust generation. Therefore, this study focuses on the force generation and power consumption in different flapping patterns as well as the wing deformation during the flapping motion to provide some insights into the performance improvement. The results showed that the response characteristics of the actuators caused the thrust to saturate at high frequencies, and that sinusoidal pattern could generally achieve good performance and efficiency. [ABSTRACT FROM AUTHOR]

Designing actuators that can modulate power, achieve high energy efficiency, and ensure safe collision remains a challenge, especially for dynamic energy robot systems (DERS) with high‐performance requirements. Herein, a novel multi‐configuration elastic actuator (MCEA) is proposed based on a controllable planetary differential mechanism (PDM) with one power port from three springs. These springs, positioned between the inner gear ring and the fixed housing shell, are regulated by a single servo motor through a ratchet–pawl mechanism. This setup enables the springs to absorb energy during collisions, reducing impact and subsequently releasing this energy to boost power output. The inner gear ring functions as a controllable one‐way rotating element, acting either as an input or output for power. The MCEA's ability to manage power modulation and energy flow is demonstrated through experiments that highlight its potential for safe collision management, energy recycling, and power modulation. Experiment results indicate that the maximum output power of the MCEA in the proposed hybrid elastic actuation (HEA) mode is 8.05 times higher than that in the traditional actuation (TA) mode. A single‐legged robot with a four‐link mechanism is also built to validate the considerable performance in the application of legged robots, showing considerable adaptability and prospects for DERS. [ABSTRACT FROM AUTHOR]

This paper reviews the process of research, development and production of a system for the active orientation of small screws. The parts feature two different shapes on each side, which is suitable for machine vision inspection and not for classical vibratory bowl traps. When a part enters the jig, it is rotated at an angle of 90° for inspection. Based on the orientation, it may stay in this position or be rotated at 180°. This allows for active orientation; regardless of how the screw is presented to the camera, it is always positioned in the correct orientation by a servo mechanism. The main challenges are related to the small dimensions of the part. First of all, it has a diameter of only 3 mm and a length of 7 mm. A vibratory bowl feeder is used only for feeding and there is no orientation functionality in it. Afterwards, a vibratory linear feeder is placed so the ready parts are stacked and, thus, some buffer is created. This is important because vibratory bowl feeders are known for having unequal productivity in time and this could be solved by the linear feeder. Another key difficulty is the quality of the source parts. They are produced by several suppliers and sometimes there are chips and other remnants alongside the packages with screws. This imposes the need for a cleaning system as part of the servo actuator's mechanism. Cleaning does not occur on every cycle; it is based on a timer that is predefined. [ABSTRACT FROM AUTHOR]

This work presents a strategy to improve the control of robot manipulators actuated by servomotors controlled in position. The improvement consisted on using artificial vision in order to implement a second control loop that guarantees the joint position tracking of the desired values. The visual feedback algorithm is robust upon rotations and translations of the camera, which is its main advantage against other similar approaches reported in the literature. The proposed technique was tested on a 3 DOF robot with position actuators, to which different desired joint positions were commanded and regulated through a PID controller. The experiments were performed with different rotation angles of the camera, obtaining successful results by reducing the joint position errors with respect to the position regulation without visual feedback. [ABSTRACT FROM AUTHOR]

Whenever additional states of a plant can be measured, closing nested feedback loops can be exploited in a variety of ways. The goal here is to reduce the bandwidth of feedback controllers and thus reduce the amplification of sensor noise that can otherwise spoil the expected performance when the actuator saturates. This can be particularly relevant for demanding tracking specifications and large plant uncertainties. In this context, the current work proposes a novel model-matching control architecture with a feedforward controller and two feedback controllers, which is accompanied by a new robust design method in the frequency domain of Quantitative Feedback Theory (QFT). The use of a feedforward controller reduces the amount of feedback to the minimum necessary to constrain the spread of the tracking error responses as specified. Furthermore, this amount of feedback is quantitatively distributed along the frequency between the inner and outer loops to reduce the total sensor noise at the control input as much as possible. A theoretical example illustrates the method and highlights the advantages of the new architecture over two other previously feasible QFT solutions: one with double feedback and another with single feedback plus feedforward. The importance of choosing the correct switching frequency between loops is also demonstrated. Finally, the angle of rotation of a commercial servo motor is successfully controlled using the motor speed as an internal measure. [ABSTRACT FROM AUTHOR]

In this article, the problem of high precision motion control for motor servo systems with modeling uncertainties and unknown actuator backlash is addressed. The combination of synthesized adaptive laws and continuous nonlinear robust term handles parameter uncertainties and system disturbances. The adaptive technique updates the unknown parameters of actuator backlash in real time and the backlash inverse function eliminates the backlash effect. Meanwhile, the designed controller without knowing the range of the disturbance upper bound but automatically estimates through the adaptive law, which improves the engineering practicability. Finally, the theoretical analysis proves the perfect asymptotic stability of the presented controller even with unmodeled disturbances and unknown actuator backlash. Extensive comparative experiments reveal the superiority of the presented method. • A nonlinear robust adaptive controller is proposed for motor servo system with unknown actuator backlash. • The unknown upper bound of unmodeled disturbances can be updated by adaptive laws online. • Excellent asymptotic output tracking performance is achieved with the proposed controller. • The effectiveness of the proposed controller is verified by comparative experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a static anti-windup compensator (AWC) design methodology for the locally Lipschitz nonlinear systems, containing time-varying interval delays in input and output of the system in the presence of actuator saturation. Static AWC design is proposed for the systems by considering a delay-range-dependent methodology to consider less conservative delay bounds. The approach has been developed by utilizing an improved Lyapunov-Krasovskii functional, locally Lipschitz nonlinearity property, delay-interval, delay derivative upper bound, local sector condition, L2 gain reduction from exogenous input to exogenous output, improved Wirtinger inequality, additive time-varying delays, and convex optimization algorithms to obtain convex conditions for AWC gain calculations. In contrast to the existing results, the present work considers both input and output delays for the AWC design (along with their combined additive effect) and deals with a more generic locally Lipschitz class of nonlinear systems. The effectiveness of the proposed methodology is demonstrated via simulations for a nonlinear DC servo motor system, possessing multiple time-delays, dynamic nonlinearity and actuator constraints. [ABSTRACT FROM AUTHOR]

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This brief introduces a novel bioinspired motor neuron dynamical unit where the neural dynamics, responsible for the generation of the action potentials, is embedded into the actuator dynamics, which here plays the role of, and substitutes, the recovery variable into the classical neuron equations. A recently introduced nullcline-based control strategy, over servomotors embedded into piecewise linearly approximated FitzHugh–Nagumo neuron models, is here applied to the synchronization of two embodied motor-neuron units in the form of either a continuously active proportional gain or an event-driven strategy. In view of the application to such problems as the generation of adaptive control laws for distributed oscillatory networks, at the basis of bioinspired walking machines, the advantages in terms of the reduced-order dynamical equations and ease of synchronization are presented both through simulations and with experiments devoted to control networked Dynamixel MX-28AT servomotors via an microcontroller unit (MCU) board. [ABSTRACT FROM AUTHOR]

The hydraulic servo actuators (HSA) are often used in the industry in tasks that request great powers, high accuracy and dynamic motion. It is well known that HSA is a highly complex nonlinear system, and that the system parameters cannot be accurately determined due to various uncertainties, inability to measure some parameters, and disturbances. This paper considers control problem of the HSA with unknown dynamics, based on adaptive dynamic programming via output feedback. Due to increasing practical application of the control algorithm, a linear discrete model of HSA is considered and an online learning data-driven controller is used, which is based on measured input and output data instead of unmeasurable states and unknown system parameters. Hence, the ADP based data-driven controller in this paper requires neither the knowledge of the HSA dynamics nor exosystem dynamics. The convergence of the ADP based control algorithm is also theoretically shown. Simulation results verify the feasibility and effectiveness of the proposed approach in solving the optimal control problem of HSA. [ABSTRACT FROM AUTHOR]

We discuss the problem of rolling without slipping for a spherical shell with a pendulum actuator (spherical robot) installed in the geometric center of the sphere. The motion of the spherical robot is controlled by the Bilimovich servo-constraint. To implement the servo-constraint, the pendulum actuator creates a control torque. because the physical implementation of the Bilimovich constraint as a nonholonomic constraint is somewhat difficult, it can be implemented as a servo-constraint. Based on the general equations of motion, the kinematic constraints, and the servo-constraint, the equations of motion for this mechanical system are obtained. When the pendulum moves in the vertical plane at fixed levels of the first integrals, the resulting system of the equations of motion reduces to a non-Hamiltonian system with one degree of freedom. We find the conditions for the implementation of the motion program specified by the servo-constraint. The dynamics analysis is based on the study of phase portraits of the system, period maps, and plots of the desired mechanical parameters. [ABSTRACT FROM AUTHOR]

An electrohydrostatic actuator (EHA) system is one of the key components of electric aircraft flight controls. The EHA system with fixed pump displacement and variable motor (EHA-FPVM) is widely used because of its simple structure, but the power weight ratio of EHA-FPVM is small, although it is very important to an aircraft. A novel EHA with a constant-torque variable-displacement pump (CTVDP) is proposed and simulated; it can substantially decrease the maximum motor-rated torque while reducing the servo-motor volume and weight. First, the CTVDP structure of the EHA system is proposed and a constant-torque variable-displacement pump is designed. Second, mathematical models of the EHA system structure are developed and simplified according to the constant-torque displacement–pressure law. Third, an adaptive backstepping control algorithm is proposed to improve position-tracking performance in the presence of the uncertain viscous damping coefficient. Finally, numerical simulations prove that the EHA system with CTVDP structure can further decrease motor maximum torque by approximately 37.5% and is robust against load impact, pump displacement variation, and parameters uncertainty. The results of this study can serve as the foundation for future application. [ABSTRACT FROM AUTHOR]

One of the main concerns associated with diagnosis, prognosis, and health management (DPHM) of engineering systems is the accuracy of estimates that are derived from Bayesian tracking methods. Estimating the exiting degradation based on stochastic models and evaluating the remaining useful life (RUL) of the system is inherently associated with variances that characterize the inaccuracy of estimation techniques. Furthermore, there are scenarios where a single measurement does not necessarily generate sufficient information regarding the system states, leading one to require multiple readings (and, hence, multidimensional analysis) to deduce diagnostic and/or prognostic decisions. This article introduces a novel approach for solving complex nonlinear multivariable Bayesian models that are utilized for estimation and prediction problems that would be, otherwise, challenging or impractical to solve through available methods, such as particle filters (PFs). Theoretical derivation and strategies that are developed in this article are verified through numerical case study simulations for electrohydraulic servo valves (EHSVs) that constitute a core component of many hydraulic actuators, such as multifunctional spoilers (MFSs), which are widely utilized in aircraft flight control systems. Our developed results are compared with those that are derived through PF in order to illustrate and demonstrate the advantages, benefits, and improvements that are accomplished by applying our proposed methodologies. [ABSTRACT FROM AUTHOR]

Compact geared servo drives are a common part of modern industrial automation; thus, their proper modelling is a necessary part for the application and control design. The presented paper focuses on the mathematical model of the cycloidal gearbox, which is used in the compact actuator with a permanent magnet synchronous motor. A measurement procedure to obtain the necessary gearbox parameters is presented along with its mathematical model. A new approach was used to model the stiction and nonlinear gearbox friction behaviour in all four quadrants. A simulation of the actuator with the modelled gearbox is described and its results are compared with the real system measurement. Obtained results show a high match between simulation and experimental results and confirm the correctness of the simulation model. [ABSTRACT FROM AUTHOR]

To solve the problem of transient control design with uncertainties and degradation in the life cycle, a design method for a turbofan engine's transient controller based on reinforcement learning is proposed. The method adopts an actor–critic framework and deep deterministic policy gradient (DDPG) algorithm with the ability to train an agent with continuous action policy for the continuous and violent turbofan engine state change. Combined with a symmetrical acceleration and deceleration transient control plan, a reward function with the aim of servo tracking is proposed. Simulations under different conditions were carried out with a controller designed via the proposed method. The simulation results show that during the acceleration process of the engine from idle to an intermediate state, the controlled variables have no overshoot, and the settling time does not exceed 3.8 s. During the deceleration process of the engine from an intermediate state to idle, the corrected speed of high-pressure rotor has no overshoot, the corrected-speed overshoot of the low-pressure rotor does not exceed 1.5%, and the settling time does not exceed 3.3 s. A system with the designed transient controller can maintain the performance when uncertainties and degradation are considered. [ABSTRACT FROM AUTHOR]

Light electric vehicles are alternative solutions to passenger cars in terms their lower costs and space saving in city traffic. Narrow tilting vehicles (NTV), known also as three–wheeled vehicles, can be equipped with an active tilting stability controller that tilts the vehicle automatically during cornering to enable lateral stability. There are mainly direct tilt control (DTC), steering tilt control (STC), and combined DTC–STC methods described in the literature. The DTC method is typically applied up to 10 km/h vehicle speeds. Considering city traffic and frequent start–stop cycles, the DTC method needs to be improved in terms of lower actuator torque and energy consumption. DTC can be designed by using either hydraulic or servo motor actuators. In state of the art, the servo motor actuator has not been studied in detail considering its integration and application aspects. Mostly, the actuator has been considered as a black box model. Proposed control method in this study enables improvements in the direct tilt control system (DTC) in terms of reducing the actuator peak torque and enables the application of DTC at higher vehicle speeds. Regarding the modeling of the electric actuator, a permanent magnet synchronous motor and field-oriented control model are also included in the simulation model. Modelling of the electric actuator enables accurate representation of actuator dynamics. In this way, battery Ah capacity can be sized and energy consumption of the electric actuator can be calculated for a given drive cycle. To this end, objective of this study is to design a direct tilt control method including the electrical drives and motion control concepts. In this way, an application methodology of the servo motor actuator is developed and implemented on a narrow tilting three-wheeled electric vehicle. Interactions between tilt control system and the servo motor actuator system are described from practical aspects. [ABSTRACT FROM AUTHOR]

Series elastic actuators (SEAs) have had sound contributions in the robotics field, and significant breakthroughs have been achieved. Despite this fact, there are still drawbacks to their performance. The elastic spring, which provides compliance, limits the SEA’s performance by lowering the bandwidth of force/torque generation, and this bandwidth decreases even further when the SEA has to render large torques. This problem originates from the constraints in motor and motor driver, such as torque and velocity limits. In this brief, the mathematical tools to analyze how these limitations influence the force control performance of SEA are proposed. To this end, a novel criterion called maximum torque transmissibility (MTT) is defined to assess the ability of SEA by fully utilizing the SEA dynamics, a maximum continuous torque, and permissible velocity of the servo motor. Further, based on MTT, a new concept called the maximum torque bandwidth that can indicate the frequency limit in which SEA can generate the maximum torque is proposed. Various design parameters, including the load condition and mechanical and controller design parameters of SEA, are evaluated. Experimental results verify that MTT can indicate the limitation of the performance of SEA precisely. [ABSTRACT FROM AUTHOR]

The most important function of a prosthetic hand is their ability to perform tasks in a manner similar to a natural hand, so it is necessary to perform kinematic analysis to determine the performance and the ability of the prosthetic human finger design to work normally and smoothly when it's drive by two sets of links that embedded in its structure and pulled by a servomotor, so the Denvit-Hartenberg method was used to analyse the forward kinematics for the prosthetic finger joints to deduction the trajectory of the fingertip and the velocity of the joints was computed by using the Jacobian matrix. The prosthetic finger was modelled by the Solidwork - 2018 program and the results of kinematics were verified using MATLAB. The analyses that were conducted on the design showed that the designed prosthetic finger has the ability to perform movements and meets the functional requirements for which it is designed. [ABSTRACT FROM AUTHOR]

Hydraulic servo actuator always suffers from various disturbance and uncertainties, which makes it difficult to design a higher performance controller. In this paper, an integral nonsingular terminal sliding mode controller based on extended state observer (ESO-INTSM) is proposed to improve the robust performance of hydraulic servo actuator. The ESO is designed to estimate not only the parametric uncertainties but also the model disturbance. Based on the observed states of ESO, the proposed controllers could enable hydraulic servo actuator to track the desired motion trajectories. The stability of the synthesized controller is proved via Lyapunov analysis, which is very important for high-accuracy tracking control of hydraulic servo actuator. Simulation and experimental results demonstrate that the proposed control strategy can effectively attenuate the adverse influence caused by the uncertainties and apparently improve the tracking accuracy. [ABSTRACT FROM AUTHOR]

In this article, an adaptive conditional servocompensator is proposed to achieve precise tracking control of systems with hysteresis without requiring explicit inversion of the hysteresis. Motivated by a range of applications, such as the piezoelectric-actuated nanopositioning, the system considered in this work consists of a chain of integrators preceded by a hysteresis nonlinearity modeled by a modified Prandtl–Ishlinskii (MPI) operator with uncertainty. To facilitate the proposed control design, the MPI operator is rearranged into a form comprised of three parts: a linear term, a nominal hysteretic term represented by a classical Prandtl–Ishlinskii (PI) operator, and a hysteretic perturbation. The bound on the hysteretic perturbation is further derived based on the parameter uncertainty of the MPI operator. The controller consists of two major elements. The first is a continuously implemented sliding mode controller (SMC), which exploits the bound on hysteretic perturbation and drives the system states to a bounded set in finite time. To properly “cancel” the nominal hysteresis effect without inversion, a technique involving a low-pass filter is introduced. The second element of the proposed controller is an adaptive conditional servocompensator that aims to eliminate periodic components in the tracking error. We show that, with persistent excitation, the closed-loop variables are ultimately bounded and the tracking error approaches a neighborhood of zero, where the neighborhood can be made arbitrarily small via the choice of the SMC boundary-layer width parameter and the servocompensator order. The proposed approach is implemented experimentally on a commercial nanopositioner under different types of periodic references, and it shows superior tracking performance over the traditional proportional–integral control, as well as several hysteresis inversion-based approaches reported in the literature. [ABSTRACT FROM AUTHOR]

The modern world is facing critical issues such as water, energy, health, wasteland and climate change, and most importantly, food for all. In arid lands, the challenges are in securing local sources of food and water. The aim of this paper is to contribute to mitigating these problems by demonstrating a system that integrates food production using aquaponics with desalination to produce drinking water, renewable energy to generate electricity and power the system, recycling food waste as a raw material and fertilizers, tiered flowerbeds to reduce land use and automation to ensure an adaptive and sustainable process and contribute to the health of the community by promoting the production of high quality locally produced organic products. In this proposed solution, the system has sensors to monitor the temperature, humidity, and water levels in the different components of the aquaponics system. It has pumps, solenoid valves, and servomotors as actuators. The renewable energy system is an off-grid solar PV system with battery that powers a microcontroller and data logger with connections to the sensors and actuators. [ABSTRACT FROM AUTHOR]

Large-capacity optical storage materials have reached a stage of relative maturity, but progress in the design of optical pickup actuators is currently slow. To improve the reading and writing capabilities of optical recording systems, we propose a design for a four-sided magnetic circuit for an optical pickup actuator for multilayer high-density optical disks that make full use of the space around the actuator. The basic magnetic circuit model in this design, which is derived by the equivalent magnetic charge method, can be applied to the design of all such actuators. The static and dynamic magnetic circuit evaluation parameters established in this paper can be used conveniently and directly to improve the magnetic circuit performance of the actuator. The design was verified by finite element simulation, and linear working ranges of ±2.6 mm, ±0.6 mm, and ± 16 ° were found in the focusing, tracking, and tilting degrees of freedom. This is sufficient to compensate for errors in phase-change optical disks with more than 50 layers in high-speed rotation. The theoretical servo accuracy of the actuator can reach tens of nanometers. This can be used with a dual-objective-lens layout that can support layer-skip reading and writing of optical disks with an effective working bandwidth greater than 10 000 Hz. [ABSTRACT FROM AUTHOR]

To study the electric actuator, a model is established with backlash nonlinearity and equivalent rigidity considered. Applying the describing function, the limit cycle of the actuator system is analyzed, and the characteristics of the limit cycle's frequency and amplitude are also analyzed. A method adding negative feedback moment to the load is proposed. The feedback moment can suppress the limit cycle of the actuator by changing the motion state of the load. The effect of the feedback moment to the servo system is analyzed and the principle of the feedback coefficient is given. The simulation results show the effectiveness of the describing function in predicting the limit cycle in the nonlinear system, and the proposed method does not affect the servo performance of the system and the negative feedback moment is valid in suppressing the limit cycle of the electric actuator with the backlash nonlinearity. [ABSTRACT FROM AUTHOR]

Self-sensing actuators use a single piezoelectric element as actuators and sensors simultaneously. This paper proposes the asymmetric indirect-driven self-sensing actuation (AIDSSA) circuit to realize the concept of self-sensing in piezoelectric-actuated systems. Unlike traditional circuits relying on differential amplifiers, the AIDSSA circuit is constructed with only op-amps and uses negative feedback to reject the common-mode interferences from the control command. The new circuit requires simpler conditions of component matching and is able to sense the mechanical responses with a uniform gain and without a phase lag. The actuator is able to achieve full-stroke actuation while sensing is performed, because AIDSSA introduces no undesirable dynamics into the control loop. For the first time, the sensing and actuation transfer functions in self-sensing actuators have become fully decoupled at all frequencies. The investigation takes the form of an industrial application of hard disk drives, and demonstrates the usefulness the circuit in complex positioning systems. Experimental results show that the position error variance, a measure of disturbance rejection capability, has been improved by about 15% in the track-following mode relative to the same servo before modifications. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive neural network (NN) controller is proposed for a class of nonlinear active suspension systems (ASSs) with hydraulic actuator. To eliminate the problem of “explosion of complexity” inherently in the traditional backstepping design for the hydraulic actuator, a dynamic surface control technique is developed to stabilize the attitude of the vehicle by introducing a first-order filter. Meanwhile, the presented scheme improves the ride comfort even when the uncertain parameter exists. Due to the existence of uncertain terms, the NNs are used to approximate unknown functions in the ASSs. Finally, a simulation for a servo system with hydraulic actuator is shown to verify the effectiveness and reliability of the proposed approach. [ABSTRACT FROM AUTHOR]

This study devises a variable-performance control law for rover vehicles servoing velocity and pitch angle commands. This considers both vehicle and actuator dynamics as well as load and parameter variations. The main merits are summarized as follows. First, the proposed auto-tuning law magnifies the feedback gain for desired systems to achieve transient performance improvement with the convergence property guarantee. Second, the collaboration of pole-zero cancellation controller and disturbance observers eliminates over/undershoots through closed-loop order reduction by a special form of feedback gain. Beneficial closed-loop properties are also derived from the closed-loop analysis. The prototype rover vehicle built with TETRIX and MyRIO-1900 experimentally validates the closed-loop performance and robustness improvement. [ABSTRACT FROM AUTHOR]

The issue of resilient reliable dissipativity performance index for systems including actuator faults and probabilistic time-delay signals via sampled-data control approach is investigated. Specifically, random variables governed by the Bernoulli distribution are examined in detail for the random time-delay signals. By using the Lyapunov–Krasovskii functionals together with the Wirtinger double integral inequality approach and reciprocally convex combination technique, which reflects complete information on the certain random sampling; as a result, a new set of sufficient criterion is launched to ensure that the proposed closed-loop system is strictly ${(\mathbb {Q},\mathbb {S},\mathbb {R})}$ - ${\gamma }$ -dissipative. The proposed criterion for dissipativity-based resilient reliable controller is expressed in the form of linear matrix inequalities. The major contributions of this paper is ${(\mathbb {Q},\mathbb {S},\mathbb {R})}$ - ${\gamma }$ -dissipativity concept can be adopted to analyze more dynamical performances simultaneously, such as ${\mathcal {H}_\infty }$ , passivity, mixed ${\mathcal {H}_\infty }$ , and passivity performance for the proposed system model by choosing the weighting matrices ${(\mathbb {Q},\mathbb {S},\mathbb {R})}$. Finally, an interesting simulation example is demonstrated to showing the applicability and effectiveness of the theoretical results together with proposed control law by taking the experimental values of the high-incidence research model and rotary servo system. [ABSTRACT FROM AUTHOR]

Hydraulic servo actuator is used as the core actuator in tensile compression fatigue life test equipment as it operates the micro displacement very precisely at a high frequency and can be used continuously for a long period of time. Recently, the life expectancy of automobiles has been extended, the load conditions of accelerated life testing on auto parts have been increased, and the life test time and number of tests have increased significantly in order to secure the reliability of the guaranteed life of produced vehicles. Therefore, hydraulic servo actuators mounted on accelerated life testing equipment for automotive parts are essential for much higher performance and a longer life than those tested. However, small- and medium-sized companies that supply test equipment for the fatigue life of auto often fail to develop technology due to a lack of research personnel and the development budget compared to the capabilities of large automobile manufacturers, resulting in frequent breakdowns due to the technical overload of test equipment. In this study, servo actuators were used to test automotive parts, with a maximum output of 2 ton, a maximum frequency of 3.3 Hz and a maximum displacement of 50 mm. The hydraulic servo actuator, which was installed in the tensile compression fatigue life test equipment, failed to operate normally at the site, and by analyzing it, we realized this resulted from the heat generation of insulation compression due to the accumulation of air and gas into the hydraulic oil and the increase in friction due to the deterioration of flow. A static pressure bearing was adopted as a design change to improve the root cause for this failure mode, and a very high level of geometric concentricity was secured by inserting concentric tubes outside the labyrinth seal type piston. The newly designed and manufactured actuator is the result of research that has achieved a semi-permanent long life and improved performance up to 100 Hz by non-contact operation. [ABSTRACT FROM AUTHOR]

An integrated Matlab model comprising of an electro-mechanical actuator (EMA) model, load model and state model has been constructed to investigate the cargo door actuator motion control, operation and working states, of which, a Simulink® servomotor system model is adopted to mimic the EMA actuator, a SimMechanics® model is used to compute the actuator's load, a Stateflow® state transition model is employed to simulate the working process. The results indicated that the motion is well controlled, generated load force is valid, working states and their transition logics are reasonable. The simulation verified the effectiveness and easiness of the integrated modelling method. [ABSTRACT FROM AUTHOR]

This brief addresses the problem of collision avoidance by robotic fish that have a single caudal fin. The fish is hybrid-tailed in that the caudal fin is driven by a double-jointed mechanism. One joint is driven by a servomotor and the second joint is driven by an ionic polymer–metal composite (IPMC) actuator, which is often called an artificial muscle. For this type of robotic fish, collision avoidance is performed by employing a collision cone approach. Within the framework of the collision cone approach, Lyapunov-based methods are employed to determine analytical expressions of nonlinear guidance laws with which cooperative collision avoidance can be achieved. It is shown how these cooperative collision avoidance laws can be made optimal in the sense of minimizing an energy-like performance index. The conditions under which the developed guidance laws are robust to sensor measurement errors are determined. Simulations and experiments are performed to validate the guidance laws. [ABSTRACT FROM AUTHOR]

For valve‐controlled hydraulic servo system, the suppression of mechanical dynamics uncertainties and the analysis of internal pressure dynamics stability (i.e. the pressure into the two chambers of the actuator) are still the widespread concern issues. This study presents an easy‐to‐implement observer‐based output feedback control scheme for hydraulic valve‐controlled single‐rod actuator system with addressing mismatched mechanical dynamic uncertainties and proving internal pressure dynamics stability analysis. The singular value perturbation approach is used to simplify the system model, and then a practical output feedback controller augmented with extended‐state observer is developed through back‐stepping design approach. The main contribution of this study is two‐fold. First, a practical reduced‐order model‐based back‐stepping controller is developed. Second, the stability issue of internal pressure dynamics is analysed. Besides giving theoretical analysis, extensive comparative co‐simulations and experiments are carried out to illustrate the effectiveness of the proposed method. The present method can guarantee prescribed tracking transient performance in the presence of uncertain disturbances. Also, the stability of internal dynamics is proved. [ABSTRACT FROM AUTHOR]

In this paper, a strategy is proposed to deal with the total pitch actuator failure in the modern wind turbines. The fault is firstly detected using a suitable proportional residual which rises when the measured rotor dynamics match the pure wind turbulence driven dynamics of the reference model. The fault tolerant control method relies on the distribution of the control signal on the remaining actuators, namely the generator torque and the yaw actuator. The pseudo inverse is applied on the residual between the measured and the nominal dynamics of the tower and the rotor. The distributed control signal is then suitably filtered in order to match the production and the safety objectives. Firstly, the generator torque filter comes to minimize the high frequencies on the rotor speed for a stable production to the grid. Secondly, the band pass yaw angle filter comes to minimize the mean yaw misalignment between the yaw nacelle and the wind direction. The method shows good dynamics reconstruction capabilities while keeping a stable production within a safe environment. [ABSTRACT FROM AUTHOR]

The demand of more powerful and high-dynamic hydraulic actuators gives the servo valve as a control member an increasingly important role. The valve should provide the hydraulic actuator with sufficient volume flow over wide frequency range to achieve large strains at high operating frequencies. Here, the electrorheological effect as an electrohydraulic valve drive offers great potential. It converts the electrical input signal directly into a controlling mechanical quantity within a few milliseconds and provides theoretically unlimited strain. Thus, the electrorheological effect has the ability to increase the performance of conventional hydraulic systems. This work presents a two-stage servo valve with an electrorheological pilot stage. Furthermore, it introduces a model to describe the static and dynamic properties of the system. The model is validated on the basis of measurement results. [ABSTRACT FROM AUTHOR]

Electromechanical actuator (EMA) exhibits advanced performance in industry, but its dynamic servo responses are constrained by parametric perturbations, load torque variations, and measurement noise. A strong disturbance rejection ability is necessary for EMAs. However, this usually makes them more sensitive to the measurement noise, reducing the steady-state precision. In this article, an adaptive linear active disturbance rejection control (LADRC) controller is proposed to achieve strong antidisturbance performance and reduce noise sensitivity for EMAs. A novel parallel structure is proposed to improve dynamic responses, which replaces the traditional cascade structure of position and speed loops. Aiming to improve the antidisturbance performance, a linear full-order-extended state observer is integrated with the parallel controller, called the LADRC controller. To reduce the difficulty of parameter tuning, the number of tuning parameters of LADRC is reduced to two by a pole placement design. And these two parameters of LADRC can be adjusted adaptively by the hyperbolic tangent function. Finally, the simulation and experimental results are provided to verify the effectiveness of the proposed strategy for EMAs. [ABSTRACT FROM AUTHOR]

Demand for generating functional micro patterns on a curved surface such as molds has increased in various industrial sectors. In order to meet the demand, it is important to develop advanced micro machining technology to generate curved form and fine patterns, simultaneously and efficiently. This paper presents a newly developed machining system equipped with a fast tool servo mechanism for milling process driven by a giant magnetostrictive actuator and evaluation of its basic machining performance. The results confirmed that the developed system has capability to position the end mill precisely during machining and to generate patterned curved surface. [ABSTRACT FROM AUTHOR]

The hydraulic servo actuator with passive compliance (HPCA) is designed for hydraulically-driven quadruped robots. It is characterized by an accumulator that connects to the piston chamber of the hydraulic cylinder to buffer impact forces between a robot's feet and the ground. This paper studies the energy efficiency of this actuator in the dynamic locomotion of a quadruped robot. Different from the traditional methods of storing potentially recyclable energy using accumulators, the energy-saving principle of HPCA is to utilize the pressure-transition characteristics of the asymmetric hydraulic cylinder with control of the symmetrical valve. The accumulator can store and release oil during the switching of the transition point in each gait cycle of the robot, thereby improving the energy efficiency of the actuator. The influence of the initial inflation pressure and working volume of the accumulator on the energy efficiency of the HPCA is studied by simulation and physical experiments. The results show that the HPCA has a higher energy efficiency that is independent of the physical parameters of the accumulator. [ABSTRACT FROM AUTHOR]

Set-point tracking servo systems encounter the problem of the trade-off between the swiftness and smoothness in tracking task. To deal with this problem, the proximate time-optimal servomechanism based on transition process (PTSTP) is proposed in this paper. The PTSTP control scheme incorporates a transition process (TP) into the framework of proximate time-optimal servomechanism (PTOS) to eliminate the conservatism of the original PTOS without the controller changing. The target position signal amplitude and the ultimate ability of actuator are utilized to design the time-optimal TP to make the jumping target position signal turns to a smooth signal, which can significantly reduce system overshoot. Therefore, the system swiftness and smoothness performance are guaranteed by PTSTP. Then, the stability of the proposed method is analyzed theoretically. Finally, the experimental results show that the controlled system is able to track the target position signal with different amplitude fast and smoothly in an electro-optical set-point tracking servo system. [ABSTRACT FROM AUTHOR]

Highlights • Propose a simple but effective nonlinear proportional-derivative (PD) control faster and high-precision positioning of servomechanisms subject to actuator saturation. • Prove global asymptotic stability. • Demonstrate the effectiveness and improved performance through numerical simulations and real experiments. • The proposed control has simple intuitive structure with high computational efficiency and does not involve modelling parameter. • The proposed control has the ability to ensure that actuator constraint is not breached, and thus it completely avoids the performance degradation from excessive torque. Abstract This paper investigates the problem of high performance motion control for servomechanisms subject to actuator saturation. A very simple but quite effective nonlinear proportional-derivative (PD) control is proposed for faster and high-precision positioning of such systems. The particular reasoning behind our concern on nonlinear PD (NPD) control is that most of practical servomechanisms so far are still controlled by classic proportional-integral-derivative (PID)/PD or nonlinear PID (NPID)/NPD algorithms and these controls do not explicitly take into account actuator constraint. Lyapunov's direct method is employed to prove global asymptotic positioning stability. The appealing advantages of the proposed control are that it has simple intuitive structure with high computational efficiency and does not involve modelling parameter. An additive feature is that the proposed control has the ability to ensure that actuator constraint is not breached, and thus it completely avoids the instability and degraded or unpredictable motion and thermal or mechanical failure from excessive torque. Simulations and experimental results demonstrate that the proposed approach offers a comparable result over the existing model-dependent nonlinear controls and a much improved performance over the commonly-used model-independent linear PD control for servomechanisms with actuator constraint. [ABSTRACT FROM AUTHOR]

Pneumatic servo drives often demonstrate significant non-linearities and low natural frequency. This paper studies the feasibility in employing such drives to achieve simple motion profile following through adopting a high-gain control approach. A new design model is presented, which differs from previous research studies and provides the basis for formulating the control approach. A vane-type reciprocating actuator has been chosen for this study. The effects of various controller gain terms on dynamic responses and system stability are illustrated. A tuning procedure is thus identified on the basis of analytical and experimental observations. [ABSTRACT FROM AUTHOR]

Control of wind-induced flutter of a bridge deck is studied using static output feedback. Servomotor-actuated winglets provide the control forces. Deck and winglets are modeled as flat plates and their aerodynamic interaction is neglected. Self-excited wind forces acting on deck and winglets are modeled using the Scanlan-Tomko model, with flat plate flutter derivatives (FDs) obtained from Theodorsen functions. Rogers rational function approximation (RFA) is used for time domain representation of wind forces in order to simplify the stability and control analyses. Control input to servomotors is based on direct feedback of vertical and torsional displacements of deck. Feedback gains that are constant, or varying with wind speed, are considered. Winglet rotations being restricted, flutter and divergence behavior is studied using system eigenvalues as well as responses. Results show that variable gain output feedback (VGOF) control using servomotor driven winglets is very effective. It provides the maximum increase in critical speed and maximum attenuation of response, followed by control with gain scheduling, with the former requiring less input power. Control with constant gain is least effective. Control of deck rotation generally appears to improve with wind speed. [ABSTRACT FROM AUTHOR]

This paper presents the development of a graphical interface implemented in a 3-RRR planar parallel manipulator. The graphical interface allows the control, in open loop, of the position of the manipulator, allowing to locate in the plane the end actuator and define its pose. The graphical interface allows the visualization of variables such as angular position, torque, voltage of the servomotors that drive the input links. The theoretical and real comparison of the angular displacement and the torque in the motors during the chosen path is shown, obtaining very close results between both. [ABSTRACT FROM AUTHOR]