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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.

This paper proposes the use of the integral sliding mode control (ISMC) based on the barrier function to control the servo actuator system with friction. Based on the barrier function, the main features of the ISMC design were preserved, additionally, the proposed control design is done without the need to know the bound on the system model uncertainty, accordingly, the overestimation of the control gain doesn’t take place and the chattering is eliminated. Moreover, the steady-state error can be adjusted via selecting the barrier function parameter only. The simulation results demonstrate the performance of the proposed ISMC based on the barrier function where the system angle successfully follows the desired angular position with a small pre-adjusted steady-state error. Additionally, the obtained results clarify superior features compared with a traditional ISMC designed to the same actuator.

The technical, economic, and performance indicators of hydromechanical servo actuators with throttle control (HMSA/T) can be radically improved by structurally correcting the actuator initial configuration followed by parametrically optimizing the found solution. The conventional solution boils down to an analysis of partial correction problems. However, this adds difficulty to comparison of the results and entails a significant scope of refinement and adjustment works. The article presents a unified algorithm for settling matters concerned with structural and parametric correction of an HMSA/T as applied to the most efficient ways of changing the actuator initial structure: damping the hydraulic amplifier sliding valve and introducing additional feedbacks for the output section motion speed and derivative of pressure difference in the hydraulic amplifier outlet hydraulic lines. An integrated HMSA/T model is constructed on the basis of standard structural correction schemes and partial mathematical models of actuators, and the scheme of an algorithm for combined structural and parametric correction of the actuator is presented. It is shown that the algorithm can be implemented using limited computation resources with a quickly running application software.

A hydraulic servo actuator with passive compliance (HPCA) is designed for hydraulic actuated quadruped robots, aiming to solve the response discrepancy of the low-bandwidth servo valve to impact forces between robot's feet and the ground. This paper focuses on the performance of this passive compliance method combined with an active compliance control strategy when used on quadruped robots. First, the frequency-response characteristics of the HPCA are further discussed. Then, combined with the requirements of the quadruped robot, a compliant method characterized by incorporating dynamic feedforward control and joint angle feedback control items into the virtual model is proposed. Finally, both the new algorithm and the performance of the HPCA are verified by simulation and experiment. The results demonstrate that, compared with the original actuator, the frequency-response characteristics of the HPCA have better adaptability for the quadruped robot, while the efficiency of the active compliance control is also improved by this novel passive compliance strategy.

Actuator performance is an important factor limiting the dynamic characteristics of the robot. In this paper, the energy transfer capability of the hydraulic servo actuator is improved by adding a miniature accumulator. We established the dynamic model of the system and obtained the optimal inflation pressure of the gas in the accumulator by numerical method. Both numerical analysis and virtual prototype simulation show this design can enlarge the work of the actuator to about 1.66 times the original. It allows the actuator to maintain high performance while reducing mass and volume.

A new motor-driven lever-based servo actuator is proposed for automatic manipulation of dry clutches. The dynamic model considering the negative stiffness of the diaphragm spring is built. The characteristics of torque-saving and power-saving are analyzed. Moreover, the stability addressing the negative stiffness is analyzed. The simulation results are verified by the experimental results. The results from quasi-steady experiments show the proposed actuator reduces the motor torque up to 23.9%, the motor power loss up to 38.7%, and the motor output power up to 21.9% compared to the ordinary lever-based actuator. As a whole, the energy consumption during a usual clutch engagement is reduced by 30.1%. In addition, the proposed actuator can track the desired displacement well under the negative stiffness case, and thus overcomes the weakness of the “Luk-like” actuator.

점적률 Key Words: Servo Actuator(서보 액추에이터), Response Characteristic(응답 특성), Design Parameter(설계 파라미터), FEM Analysis(유한요소 해석), Performance Test(성능 시험) 초록: 유압밸브 구동용 서보 액추에이터는 항공기, 자동차의 유압시스템 그리고 산업용 유압시스템의 정밀한 작동에 중요한 장치이다. 서보 액추에이터의 신뢰성 있는 동작은 전체 유압시스템의 정밀한 제어에 큰 영향을 미친다. 서보 액추에이터의 주파수 응답특성, 스텝 응답특성과 같은 응답특성은 액추에이터의 성능을 판단하는 중요한 기준이 된다. 본 논문에서는 신뢰성해석을 통해 신뢰성 있는 동작과 응답특성을 만족시키기 위한 구성 부품에 대한 분석을 실시하였다. 또한 신뢰성 있는 동작과 빠른 응답성을 구현하기 위해 현장의 경험적 지식과 문헌 및 전문가의 전자기 이론을 통해 유압밸브 구동용 서보 액추에이터의 설계 파라미터를 도출하였다. 보빈, 요크, 플런저의 설계값, 그리고 코일의 감긴 수와 같은 서보 액추에이터의 설계값들을 결정하는 설계 파라미터를 제안하고, 설계방정식을 통해 산출한 설계값을 유한요소해석을 통해 타당성을 검증하였다. 또한 서보 액추에이터가 장착된 유압밸브의 성능시험을 통해 제안한 설계 방안의 타당성을 검증하였다. Abstract: The precision hydraulic valve is widely used in various industrial field like aircraft, automobile, and general machinery. Servo actuator is the most important device for driving the precise hydraulic valve. The reliable operation of servo actuator effects on the overall hydraulic system. The performance of servo actuator relies on frequency response and step response according to arbitrary input signal. In this paper, we performed the analysis for the components of servo actuator to satisfy the reliable operation and response characteristics through the reliability analysis, and also induced the design parameters to realize the reliable operation and fast response characteristics of servo actuator for hydraulic valve operation through the empirical knowledge of experts and electromagnetic theories. We suggested the design equations to determine the values of design parameters of servo actuator as like bobbin size, length of yoke and plunger and turn number of coil, and verified the achieved design values through FEM analysis and performance tests using some prototypes of servo actuators adapted in hydraulic valve.

Velocity and position are the most important signals used in industrial controllers such as proportional–integral–derivative controllers. While in some real-time applications like structural control, acceleration measurements are easily accessible via accelerometers. The velocity and position have to be estimated from the measured acceleration. In this paper, offset cancellation and high-pass filtering techniques are combined effectively to solve common problems in numerical integration of acceleration signals in real-time applications. The integration accuracy is improved compared with other numerical integrators. Experimental results on a linear servo actuator and a shake table illustrate the effectiveness of the proposed method.

To resolve the complexity and uncertainty between the fault portent and the causes of electric and hydraulic actuator, a fault diagnosis model base on neural network arithmetic for actuator is designed. The genetic optimization arithmetic is used to initialize the value of weight and bias to improve the search efficiency and global convergence of the network. The simulation result indicate the feasibility and validity of the method based on genetic neural network model to diagnose the faults of electric and hydraulic servo actuator.

In this paper, a particle swarm optimization (PSO) method is proposed to design Quantitative Feedback Theory (QFT) control. This method minimizes a proposed cost function subject to appropriate robust stability and performance QFT constraints. The PSO algorithm is simple and easy to implement, and can be used to automate the loop shaping procedures of the standard QFT. The proposed method is applied to the high uncertainty pneumatic servo actuator system as an example to illustrate the design procedure of the proposed algorithm. The proposed method is compared with the standard QFT control. The results show that the superiority of the proposed method in that it can achieve the same robustness requirements of standard QFT control with simple structure and low order controller.

This paper addresses the experimental identification of a servo actuator which is used in many industrial applications. Because the system consisted of electrical and mechanical components, the behavior of the system was nonlinear. In addition, the under load behavior of this servo was different. The load torque was considered as the input and a two input-one output model was presented for this servo actuator. Special focus was given in order to present a simple model for this servo actuator. The comparison between simulation and experimental results showed the effectiveness of the propose model. The model can be applied as a reference for characterizing different designs and future control strategies.

This paper is dedicated to investigate the static and dynamic behavior of a pilot operated pressure reducing valve (PRV). The valve is the main component in an Anti-skid braking system of a vehicle. This system is fed by the hydraulic power from a constant pressure source. A mathematical model is deduced for the valve. A simulation program is developed usingthe MATLAB-SIMULINK where the mathematical model is implemented in the program. The developed program is used to study the dynamic valve response due to different input displacement values and effect of varying different design parameters on the overall performance of valve. A conclusion is made to evaluate the valve response and recommendations are suggested to improve valve performance.

In model based fault detection is very important to analyze how the effect of model uncertainty is considered when determining the optimal threshold to be used in residual evaluation. In case of model uncertainty is located in parameters (interval model), an interval observer has been shown to be a suitable strategy to generate this adaptive threshold. However, interval observers can be affected by the wrapping effect when low computational algorithms, such as region-based approaches coming from the interval community, are used to determine the predicted output interval. This paper shows that the wrapping effect might be avoided forcing the observer gain to satisfy the isotonicity condition. Then, the effect of this observer condition on the time evolution of the residual sensitivity to a fault and the minimum detectable fault is analyzed in order to see whether the fault detection performance is enhanced or not. Finally, an example based on an industrial servo actuator will be used to illustrate the derived results.

In case of model uncertainty is located in parameters (interval model), an interval observer has been shown to be a suitable strategy to generate an adaptive threshold to be used in residual evaluation. In interval observer-based fault detection methods, the observer gain plays an important role. First, it determines the minimum detectable fault for a given type of fault. Second, it allows avoiding the wrapping effect when low computational algorithms such as region-based approaches coming from the interval community are used to determine the predicted output interval. In this paper, the effect of the observer gain on the time evolution of the residual sensitivity to a fault and the minimum detectable fault while avoiding the wrapping effect is analyzed. Finally, an example based on an industrial servo actuator will be used to illustrate the derived results.

One major difficulty in nursing the bedridden is moving their body. This includes lifting and carrying them from one place to another, as well as changing their body posture. Because they are lifting a heavy solid weight while in an unstable posture, the caregiver usually suffers hack pain due to this work. We propose a solution by replacing this labor with robotics technology to lift and/or carry a person. The robot is designed with the smooth, high torque hydraulic actuation, and the bilateral servo system for the control to meet the necessity of the service. The superiority of this robotic device is in its interface and output torque. The bilateral servo system allows the robot to he directly operated (holding the end of the arm) and to control an average weight of a Japanese adult (e.g. 60 kgf) with little effort (e.g. 1 kgf).

This paper mainly focuses on the design of a novel type of intelligent DDV actuator system for aeroplane. The function, structure principle and redundancy management of the intelligent DDV (Direct-Drive-Valve) servo actuator system for aeroplane is described in detail. The intelligent DDV servo actuator which is the important part of the system is also described in the paper, including the structure and performance characteristic, the key technique, and so on. An experiment is conducted to verify the dynamic performance and fault monitoring function of the new system. The hardware-in-loop experimental results prove that the design and application of the intelligent DDV servo actuator system on some aeroplane could solve the technical problems in real world. Also, the control precision, stability, and fault monitoring of the system can perfectly satisfy the aeroplane control system design requirements.

Servo actuator is one most important section of flying control system, and faults also often happen to it. The fault detection and diagnosis technology is seriously important to improve the reliability of servo actuator. The paper proposes a method of fault diagnosis based on Elman neural network, using its non-linear distributed processing and dynamic feature reflecting ability to detect servo actuator fault. Then, neural network algorithm is applied to simulation. The result indicated that the method could accurately identify the servo actuator fault. Meanwhile, compared with BP neural network, the advantage of Elman neural network in fault diagnosis is confirmed.

The aims of this paper, are to obtain for an electro-hydrostatic servo-actuator, good performances, (time response and frequency characteristics), making it usable on aircraft, and a more simple configuration of the regulator, with a short computing time and a more simple program, in order to obtain a cheaper and more simple implementation. The strategy is to reduce the membership functions number of the fuzzy regulator keeping in the same time the requested performances of the servo-actuator.

It is not easy to processing piston ring contour because of its complicating shape. From view of time-domain analysis, in order to trace the curve of piston ring, servo actuator must have high speed and acceleration to complete movement of back and forth. From view of frequency -domain analysis, the order of harmonic of the piston ring contour is very high, so the control system bandwidth also should be wide enough. It’s hard to satisfy these requirements for the traditional drive methods by using rotate serve and Lead screw. In this paper, a new method of direct drive by linear motor is provided, And achieve good results.

This paper deals with the application of the H/sub /spl infin//-approach to robustly control the force exerted by a hydraulic servo-actuator on its environment. In order to evaluate the system stability and the performance, large environmental uncertainties and disturbances are introduced by use of a particular workpiece. The major nonlinearities of the system are pointed out through experimental tests and parameters estimation results. Then, a linear time-invariant model for control is defined with respect to both system dynamics and application requirements. Experimental and simulation control results are presented and the achievement of a stability/performance trade-off is discussed.

The development of a machine that supports the movement of the upper limbs has not proceeded for paraplegics. This is because a large output power is necessary in order to move a robot arm while supporting the paralysed body. We propose a new actuator system, called the Hydraulic Bilateral-Servo Actuator (HBSA) system, which has been developed in our laboratory to be applied to powered orthosis with seven degrees of freedom.

In this paper, an iron core type LOA is designed and analyzed electro-magnetically for the application to the active control of structural vibration as an active mass driver. Structural vibration is sensored by the accelerometer attached to the structure and reduced by the optimally controlled motion of active mass of LOA giving anti-phase inertia force to the structure. As a result, LOA is confirmed to be applied to the active control of the structural vibration as an servo actuator by controlling the position of armature accurately.

Control system analysts are frequently called upon to include a hydraulic servo actuator as part of the loop in a complex closed-loop system simulation. This article presents a general description of several common types of hydraulic servo actuators and several methods for inclusion of the effects of load on the simulation of the actuator in the control loop. These methods are pre sented in block diagram form and are suitable for inclu sion in a larger simulation loop. The block diagrams themselves may be somewhat condensed and modified before inclusion in a larger simulation, but are presented here with all the details shown explicitly for clarity.

Problem of the poorly damped electrohydraulic servo actuator stabilisation is analysed. Possibilities of closed-loop transfer function poles shifting are studied, using root locus and pole shifting methods. It is shown that position and velocity feedback are not suitable for stabilisation of the system. A solution of the stability problem by means of state feedback is proposed.

Interval observers can be described by an ARMA model while l-order interval predictors by a MA model. Since an ARMA model can be approximated by a MA model, this allows establishing the equivalence between interval observers and interval predictors. This paper deals with the fault detection application and focuses on the equivalence between the l-order predictor and the interval observer with the same fault detection performance. The predictor approach is developed to obviate the wrapping effect commonly encountered with interval observer approaches. Given a particular linear interval observer, a l-order interval predictor can be found such that its behaviour is equivalent regarding fault detection and besides, it does not suffer from the wrapping effect. Thus, if the interval observer fulfils the isotonicity property, this l-order interval predictor can be computed using two point-wise trajectories corresponding to the upper and lower bound of each uncertain parameter. Finally, an example based on an industrial servo actuator will be used to illustrate the derived results.