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To augment the stretching capabilities of servo presses, an optimal transmission mechanism design is imperative. Firstly, a kinematic model of the servo press transmission system was established by employing the closed-vector formulation. A normalized composite fitness function, integrating the mechanism’s mechanical advantage, transmission angle, and slider velocity fluctuation as optimization criteria, was constructed to quantify the overall performance. Subsequently, a genetic algorithm was implemented to execute the optimization design under geometric, kinematic, transmission angle, and stroke-speed ratio constraints. The findings indicate that the optimized transmission mechanism reduces the maximum speed during the working stroke by 54.40%, increases the slider displacement during the working stage by 2.27%, and increases the proportion of the working stroke by 96.01%, effectively improving the overall forging performance of the press.

Ag 2 Se shows significant potential for near-room-temperature thermoelectric applications, but its performance and device design are still evolving. In this work, we design a novel flexible Ag 2 Se thin-film-based thermoelectric device with optimized electrode materials and structure, achieving a high output power density of over 65 W m −2 and a normalized power density up to 3.68 μW cm −2 K −2 at a temperature difference of 42 K. By fine-tuning vapor selenization time, we strengthen the (013) orientation and carrier mobility of Ag 2 Se films, reducing excessive Ag interstitials and achieving a power factor of over 29 μW cm −1 K −2 at 393 K. A protective layer boosts flexibility of the thin film, retaining 90% performance after 1000 bends at 60°. Coupled with p-type Sb 2 Te 3 thin films and rational simulations, the device shows rapid human motion response and precise servo motor control, highlighting the potential of high-performance Ag 2 Se thin films in advanced applications. The authors design a flexible Ag 2 Se-based thermoelectric device with optimized electrode materials, structure, and selenization time, capable of various applications including rapid response to human motion signals as electronic skin.

Airspace surveillance is one of the classic applications of radar technology. Existing systems are focused on large-scale surveillance of commercial airspace. This research presents a prototype of a small, mobile, passive radar system that for example can be used to monitor aircraft and UAVs in the airspace over maritime borders. The system is based on a coherent, software defined receiving system for data acquisition. The signal processing is subsequently performed in the digital domain. The paper gives an introduction to all the required fundamentals and all the relevant steps of signal processing are shown, starting from digital beamforming, through the generation of the range Doppler matrices, all the way to the tracking of targets using Kalman filters. Furthermore, a novel system for the detection of transmitter locations is presented, which allows the use of such a system in previously unknown scenarios. Finally, measurements are presented to show what such a system can achieve under real world conditions.

Regarding the mechanical resonance problem caused by the coupling of flexible characteristics and transmission stiffness, this typical problem is faced by aircraft rudder servo systems under the requirement of lightweight design. A model of the aircraft rudder servo system considering flexible coupling links is established, and the influence of transmission stiffness on the open-loop transfer function of the rudder servo system is analyzed. Increasing the transmission stiffness increases both the anti-resonance frequency and the resonance frequency of the rudder servo system, and the system performance changes depending on the change in open-loop gain margin. When the load-motor rotational inertia and product are small, and the resonant frequency is still much lower than the natural frequency of the current loop after increasing the transmission stiffness, the system open-loop gain margin will decrease and mechanical resonance will intensify. When the load-motor rotational inertia and product are relatively large, increasing the transmission stiffness to make the resonant frequency close to or even greater than the natural frequency of the current loop will increase the system’s open-loop gain margin and weaken mechanical resonance. The correctness of the research conclusion was verified through system simulation and experimental validation.

In hydropower plants, the Pelton turbine is a commonly used hydraulic turbine where flow is regulated with a dual mechanism of needle and deflector. The needle is controlled by a servomotor and governor system, where the flow rate varies by adjusting the needle strokes. The needle is operated under the hydraulic force caused by the high-water pressure inside the injector acting on the needle surface. The objective of computing the force balance in a Pelton injector is to determine the force to be supplied by the servomotor. The closing trend is crucial to design the injector for safe operation during an emergency. In this study, the function of the needle and nozzle curve generalizes the variable needle surface area, allowing the geometric properties of the nozzle and needle to be suitable for the needle force evaluation. The single-axis force transducer, which is mounted on the needle rod, has been used in the experimental method for determining the needle forces. The experimental findings are compared to analytical calculations and serve as validation for the accuracy and reliability of the computed results obtained through the analytical approach.

This paper presents some of the most significant findings in the design of a hydraulic servomechanism for flight controls, which were primarily achieved by the first author during his activity in an aviation institute. These results are grouped into four main topics. The first one outlines a classical theory, from the 1950s–1970s, of the analysis of nonlinear automatic systems and namely the issue of absolute stability. The uninformed public may be misled by the adjective “absolute”. This is not a “maximalist” solution of stability but rather highlights in the system of equations a nonlinear function that describes, for the case of hydraulic servomechanisms, the flow-control dependence in the distributor spool. This function is odd, and it is therefore located in quadrants 1 and 3. The decision regarding stability is made within the so-called Lurie problem and is materialized by a matrix inequality, called the Lefschetz condition, which must be satisfied by the parameters of the electrohydraulic servomechanism and also by the components of the control feedback vector. Another approach starts from a classical theorem of V. M. Popov, extended in a stochastic framework by T. Morozan and I. Ursu, which ends with the description of the local and global spool valve flow-control characteristics that ensure stability in the large with respect to bounded perturbations for the mechano-hydraulic servomechanism. We add that a conjecture regarding the more pronounced flexibility of mathematical models in relation to mathematical instruments (theories) was used. Furthermore, the second topic concerns, the importance of the impedance characteristic of the mechano-hydraulic servomechanism in preventing flutter of the flight controls is emphasized. Impedance, also called dynamic stiffness, is defined as the ratio, in a dynamic regime, between the output exerted force (at the actuator rod of the servomechanism) and the displacement induced by this force under the assumption of a blocked input. It is demonstrated in the paper that there are two forms of the impedance function: one that favors the appearance of flutter and another that allows for flutter damping. It is interesting to note that these theoretical considerations were established in the institute’s reports some time before their introduction in the Aviation Regulation AvP.970. However, it was precisely the absence of the impedance criterion in the regulation at the appropriate time that ultimately led, by chance or not, to a disaster: the crash of a prototype due to tailplane flutter. A third topic shows how an important problem in the theory of automatic systems of the 1970s–1980s, namely the robust synthesis of the servomechanism, is formulated, applied and solved in the case of an electrohydraulic servomechanism. In general, the solution of a robust servomechanism problem consists of two distinct components: a servo-compensator, in fact an internal model of the exogenous dynamics, and a stabilizing compensator. These components are adapted in the case of an electrohydraulic servomechanism. In addition to the classical case mentioned above, a synthesis problem of an anti-windup (anti-saturation) compensator is formulated and solved. The fourth topic, and the last one presented in detail, is the synthesis of a fuzzy supervised neurocontrol (FSNC) for the position tracking of an electrohydraulic servomechanism, with experimental validation, in the laboratory, of this control law. The neurocontrol module is designed using a single-layered perceptron architecture. Neurocontrol is in principle optimal, but it is not free from saturation. To this end, in order to counteract saturation, a Mamdani-type fuzzy logic was developed, which takes control when neurocontrol has saturated. It returns to neurocontrol when it returns to normal, respectively, when saturation is eliminated. What distinguishes this FSNC law is its simplicity and efficiency and especially the fact that against quite a few opponents in the field, it still works very well on quite complicated physical systems. Finally, a brief section reviews some recent works by the authors, in which current approaches to hydraulic servomechanisms are presented: the backstepping control synthesis technique, input delay treated with Lyapunov–Krasovskii functionals, and critical stability treated with Lyapunov–Malkin theory.

The lower hook mechanism of the fishing net weaving machine has significant impact on its weaving velocity and net quality. This study incorporated a multi-motor based lower hook mechanism, which is driven by multi-motors instead of mechanical cams. Compared with the traditional lower hook mechanism, the multi-motor based lower hook mechanism has the advantages of fewer mechanical wear and faster running speed. However, the working condition of the lower hook mechanism places a very high demand on its following accuracy and resistance to disturbance, so the servo motor should be highly accurate and highly robust. The commonly used controller of the servo motor is three closed loop proportion-integral (PI) controller. In this paper, we modelled and experimentally verified the multi-motor based lower hook mechanism, and rebuilt the servo motor controller by replacing the position loop PI and speed loop PI of the three closed loop PI controller with position-velocity joint active disturbance rejection controller. Simulations suggest that the active disturbance rejection controller performs better on both following accuracy and resistance to disturbance compared with the traditional PI controller in the application of lower hook mechanism.

Aiming at the problem that the influence degree of static and dynamic accuracy of EMA pitch servo mechanism is not clear, this paper analyzes the influence degree of static and dynamic error of EMA pitch servo mechanism based on high-precision pointing system. In terms of static error, based on the static error kinematics model, by establishing the static error probability model and solving the static error model, it is pointed out that the geometric error is the largest factor affecting the static kinematics error. In terms of the influence degree of dynamic error, based on the dynamic error kinematics model, through the establishment of the dynamic error separation process, and based on the test and mechanical experiment platform, it is pointed out that the general trend error is the largest factor affecting the dynamic kinematics error. Through the analysis of the influence degree of static and dynamic kinematic errors, the accuracy improvement direction of the EMA pitch servo mechanism is defined.

This paper describes a new robotic manipulator with three fingers based on an origami twisted tower design. The design specifications, kinematic description, and results from the stiffness and durability tests for the selected origami design are presented. The robotic arm is made of a 10-layer twisted tower, actuated by four cables with pulleys driven by servo motors. Each finger is made of a smaller 11-layer tower and uses a single cable directly attached to a servo motor. The current hardware setup supports vision-based autonomous control and internet-based remote control in real time. For preliminary evaluation of the robot's object manipulation capabilities, arbitrary objects with varying weights, sizes, and shapes (i.e., a shuttlecock, an egg shell, a paper cub, and a cubic block) were selected and the rate of successful grasping and lifting for each object was measured. In addition, an experiment comparing a rigid gripper and the new origami-based manipulator revealed that the origami structure in the fingers absorbs the excessive force applied to the object through force distribution and structural deformation, demonstrating its potential applications for effective manipulation of fragile objects.

The aerodynamic interference forces and moments of different windward surfaces of a launch vehicle bundled with a common booster core in the face vary considerably. The servo mechanism is laid out to maximize the control capability of the rocket at a certain angle. The dominant surface of the rocket is determined by aerodynamic interference and control capability. For the problem of large interference and asymmetry during the flight of a nominal rocket, a rolling active load relief control law based on the optimization of the spatial interference vector is proposed. The direction with the largest spatial interference vector is obtained online by visual acceleration information. By adjusting the rolling program angle, the rocket will align the dominant face with the direction of the largest interference when flying through the windy area. And then, the rocket obtains a good control effect. The simulation results show that the control law proposed in this paper can effectively improve the adaptability of the rocket control in the case of sudden changes in wind direction. It achieves the purpose of reducing the static load of the rocket body structure during the flight.