Electric Servo Research Articles

Mitigating Mode Switching Oscillation in a One-Motor-One-Pump Motor-Controlled Hydraulic Cylinder via System Pressure Control: Simulation Study

This study focuses on a hydraulic cylinder that is directly connected to a fixed-displacement hydraulic pump driven by an electric servo motor. This particular setup is referred to as a one-motor-one-pump motor-controlled hydraulic cylinder (MCC). This paper presents a new approach to address mode switching oscillation (MSO) in MCCs by incorporating system pressure control capabilities. It conducts a detailed investigation into the factors that contribute to MSO in standard MCCs and thoroughly evaluates the effectiveness of the proposed system in mitigating MSO. The simulation results demonstrate the successful suppression of MSO. In conclusion, the proposed MCC with system pressure control capabilities is validated and, furthermore, it shows great potential for practical applications involving small loads and rapid retraction.

Application of a Fractional Order PI Controller for a Speed Servo Drive Control

This paper deals with the tuning of the parameters of a fractional-order PI controller for the speed control of an electric servo drive in which the torque is set by a torque generator. The controller parameters are tuned using the multiple dominant pole method (MDPM), while the fractional order integrator is approximated by the Oustaloup method. The input parameters required for tuning the controller using MDPM are calculated using the optimization algorithm presented in this paper. This algorithm selects the optimal parameters from a set of points in three-dimensional space, based on the symmetry around a central point. The controller tuning is performed for the normalized control loop model. The obtained optimized normalized fractional order PI controller can then be applied to a real servo drive with specific parameters. The proposed tuning was also verified experimentally, comparing the obtained closed-loop responses with those of the integer-order PI controller. Both simulation and experimental results showed a significant reduction in the integral of the absolute error at the disturbance step compared to a control loop using an integer-order PI controller. This results in a faster output response to load torque steps and a smaller control error in a real servo drive.

Enhancing UAV elevator actuator model using multibody dynamics simulation

This paper proposes an improved actuator system model for UAV elevators using multibody dynamics simulation. The multibody dynamics simulation employs the Simscape Multibody, module in MATLAB coupled with Simulink to model the servo and hinge moment calculation. The actuator system comprises an electrical servo and mechanical components, including arms, push rods, horns, and the elevator. The electrical servo is modeled using a PID controller and a simplified motor model. The multibody dynamics simulation is employed to capture the dynamics of the mechanical components, coupled with the electrical servo through torque delivery to the mechanical components. The simulation is applied to the elevator of a medium altitude long endurance (MALE) UAV with a Maximum Take Off Weight of 1300 Kg. Generating these quantities provide a benefit in capturing the operational envelope of the servo to be compared to its limitations. Given the features of this simulation, it is proposed to extend the research by integrating this method with flight dynamics simulation.

Simulation of a Circular Interpolator Developed According to the Principle of Differential Analyzers on the Basis of Two Coordinate Electric Servo Drives with a Stepper Electric Motor

Simulation of a Circular Interpolator Developed According to the Principle of Differential Analyzers on the Basis of Two Coordinate Electric Servo Drives with a Stepper Electric Motor

Dynamic regulation of the thermal performance of the S–CO2 minichannel using a piezoelectric oscillating fin

It is difficult to alter the thermal performance of a minichannel heat sink with a fixed structure under constant operating conditions. In particular, if the local heat transfer of the substrate cannot be regulated in real time, the dynamic heat dissipation needs of high-power electronic components cannot be met in the electrical servo systems of flight vehicles. In this paper, a new minichannel heat sink structure based on the classical rectangular channel is proposed and a piezoelectric oscillating fin (POF) is introduced to replace the fixed fin. The thermal performance of the heat sink can then be regulated using the swing of the POF, with supercritical carbon dioxide (S–CO2) as the coolant. Transient numerical simulations are applied to investigate the influence of various POF operating parameters on the heat transfer of the channel, such as the oscillation amplitude and frequency. The results demonstrate that a channel with a POF can allow for dynamic and rapid adjustment of the thermal performance through control of the oscillation frequency and amplitude of the POF, with a constant channel configuration, coolant, and operating conditions. The heat transfer can be enhanced significantly by the swing of the POF, with the local Nusselt number growing up to 8.3 times and the overall one up to 1.14 times. Both the oscillation frequency and amplitude have a positive correlation with the intensity of heat transfer. The POF also contributes to a greater pressure drop and fluctuation in pumping power. A comprehensive evaluation coefficient shows that the POF is effective at improving the overall thermal performance with a low-frequency swing, while high-frequency operation enhances the local heat transfer and decreases the local temperature near the tail end of the POF. Finally, considering the effects of the frequency and amplitude of the POF, as well as the variable thermophysical properties of the supercritical coolant, a heat transfer correlation based on the Dittus–Boelter equation is established to predict the thermal performance of the channel with a POF. This prediction has a maximum error of ±0.56%.

Study on the uneven flow distribution and non-uniform heat transfer in microchannels

The power module is one of the main heating sources with non-uniform heat flux in high-power electrical servo systems used for flight vehicles. Faults in the power module are usually caused by a high or a non-uniform temperature. Given the environment of heat dissipation during flight, a regenerative cooling method is typically used, and the cooling system is designed as a microchannel heat sink with supercritical fuel. This is an effective means of solving thermal problems in the flight vehicles. However, because of the high heating power and non-uniform heat distribution of the power module, it is necessary to optimize its heat sink to restrict the high temperature rise and suppress the non-uniform distribution of temperature. In light of these considerations, a 3D numerical model of the microchannel heat sink of a power module with non-uniform heat flux was established in this study to examine the heat transfer and the thermal performance of the cooling channels. Based on the validation of the mesh and numerical method, the simulations of the flow distributions of the channels were performed to assess the thermal performance of the heat sink. It included investigating the effects of the inlet location of the manifold and its injection angle on the flow distribution in the channels, and the influences of the flow distribution and the operational parameters on the thermal performance of the heat sink. The results revealed that the Z30 configuration provided the best location and injection angle of the inlet to match the non-uniform heat flux of the power module. In this case, the values of Stanton number and buoyancy parameter of channel 4 yielded the minimum values of all channels owing to its higher flow rate and gradual rise in temperature. The deviation in the rate of mass flow Φ changed slightly corresponding to the various operational parameters, only the total heat flux would bring a bigger fluctuation. The tiny difference in temperatures among the observation areas on the substrate verified the positive influence of the flow distribution in matching the non-uniform heat flux.

A robust performance evaluation method based on interval evidential reasoning approach under uncertainty

Performance evaluation (PE) is an important part of equipment health management. If the monitoring information of the equipment is interfered, the evaluation results may be erroneous. A robust performance evaluation (RPE) method is proposed to solve this problem. The performance evaluation results are obtained by distinguishing the cases of single evidence with interference and two evidence with interference, and a robustness measurement based on interval similarity is proposed. To improve the accuracy of the evaluation results, the referential values in the IER evaluation model are optimized. The robustness thresholds of the input indexes are obtained under the satisfaction of the robustness constraints. If the interference value of the input index is within the thresholds, the deviation between the evaluation results using monitoring information with interference and those using monitoring information without interference is small. Finally, the proposed method is applied to a type of electric servo mechanism performance evaluation, and the case shows the validity of the RPE method.

A New Type of Electric Servo Actuator with an Energy Recovery Link and Its Dynamic and Energy Consumption Characteristics Analysis

A New Type of Electric Servo Actuator with an Energy Recovery Link and Its Dynamic and Energy Consumption Characteristics Analysis

Experimental Study on the Optimal-Based Vibration Control of a Wind Turbine Tower Using a Small-Scale Electric Drive with MR Damper Support

The paper presents an experimental implementation of an optimal-based vibration control for a scaled wind turbine tower-nacelle structure. A laboratory model of the approximate power scale of 340 W, equipped with a nonlinear tuned vibration absorber (TVA), is analysed. For control purposes, a combined operation of a small-scale electric servo drive and a magnetorheological (MR) damper is used in the TVA system. Nonlinearities of both the electric drive and the MR damper are intrinsic parts of the adopted nonlinear control concept. The aim of the research is the simple-hardware real-time implementation and the experimental investigation of the simultaneous actuator and damper control, including the analysis of the influence of optimal control law parameters and quality function weights on the vibration attenuation efficiency and actuator energy demand. As a reference, an optimal-based, modified ground-hook control with the single goal of the primary structure deflection minimisation is used along with the passive system with zero MR damper current and idling electric actuator, proving the advantages of the proposed method. The regarded solutions guarantee 57% maximum structure deflection reduction concerning the passive TVA configuration, using an MR damper of 32 N maximum force and an electric drive of 12.5 N nominal force and 0.76 W nominal power. An interesting alternative is the optimal control concept tuned with regard to the actuator power minimisation—it provides 30% maximum structure deflection attenuation (concerning the passive TVA configuration) while using a passive damper of 3.3 N maximum force and an actuator of 0.17 W nominal power only. It makes evident the advantage of the properly tuned optimal control algorithm over the modified ground-hook law—it requires 51% less actuator energy than the latter parametrised to exhibit the same vibration attenuation properties.

Improving the dependability of the servo drives of unmanned aerial vehicles through optimized operating modes

Aim. Improving the reliability of servo drives through partial redundancy of structural components. Methods. The paper uses methods of harmonic analysis, technical system dependability theory. Results. The mean times to failure of servo drives that differ in terms of the level of redundancy of structural elements (external connectors, feedback sensors, control boards, electric motors and load gears) were compared. It was shown that structural element redundancy along with the capability to switch to still-operable elements in the course of servo drive operation enable a triple increase of the failure tolerance. The authors suggested criteria for identifying the moment of time for decision-making regarding an electric servo’s structure modification before the moment of failure of the redundant element of such servo. Conclusion. The method suggested in the paper allows formalizing the process of electric servo structure modification for the purpose of ensuring the required level of failure tolerance.

Analysis of Switched Reluctance Motor Performance with Different Slot Pole Combinations

Abstract: The Switched Reluctance Motors are getting popularity among different applications like electric vehicles and traction due to their simple construction, lower cost and better efficiency. It also have the advantages of low rotor inertia, small size, high pickup, effective and easy cooling etc. Due to its simple structure, switch reluctance motors are mainly used in electric vehicles, vacuum cleaners, washing machines, servo types and variable speed applications. The switch reluctance motor has a rugged structure and is suitable for vibration and high temperature zones. The torque generated by the switch reluctance motor does not depend on the polarity of the phase current. As a result, fewer semiconductor switches are used in power converters. In addition, the losses incurred by SRM motors come only from the stator. Therefore, it can be easily cooled. In this work, the performance of different slot pole combination of SRM is analysed and compared. The Slot poles combinations taken for Analysis are : 6/4, 8/6 and 12/10. The main parameters on which the performance of SRM is compared are Electromagnetic Torque, Torque Ripple and Inductance in Transient Analysis and Output Torque and Power in Steady State Analysis. It is found that with increasing slot pole combination of SRM, the torque ripple decreases and average torque increases.

METALLOGRAPHIC EXAMINATION OF SURFACE LAYER AFTER ELECTRICAL DISCHARGE MACHINING

This paper presents analysis of the influence of selected electrical parameters of hollowing on the state of the surface layer after electrical discharge machining (EDM). Namely, paper focuses on the analysis of the EDM cutting process, in terms of the influence of individual parameters on the number of occurrences and sizes of erosion craters on the machined surface. The basic parameters include electrical pulse discharge time, electrical discharge pause time, voltage, current amplitude and servo voltage. The initial values of the mentioned parameters were selected based on technology tables provided by the machine manufacturer and on the basis of own empirical tests. The tests were carried out according to static determined poliselective experimental plan (Hartley plan). Analysis of the machined surface was carried out using a scanning microscope (SEM) and an optical microscope. Quantitative metallographic analysis was used to determine the stereological features of erosion craters occurring on the surface of the machined material. The results were illustrated by means of three-dimensional graphs. The presented studies show a significant effect of electrical parameters of EDM on the quality of the machined surface, i.e. the number of occurrences and diameter of erosion craters. The research presents an approach based on mathematical modelling of electrical discharge machining. This approach can form the basis for developing methods of modeling technological processes and optimizing their parameters.

Process optimization of WEDM D2 steel based on orthogonal test and response surface method

Abstract D2 steel can be used to manufacture cold working molds with large cross sections, complex shapes, high impact forces and high wear resistance requirements. Cutting speed is an important process index of WEDM. In order to study the influence of WEDM process parameters on the cutting speed of D2 die steel and explore the process parameters at the maximum cutting speed, In this experiment, the electrical parameters pulse width, pulse interval and servo voltage were selected as test factors, and the cutting speed process indexes were analyzed and optimized by orthogonal test and response surface analysis method. Experimental results show that: the influence of main electrical parameters on cutting speed is consistent; the effects of pulse width, pulse interval and servo voltage on cutting speed decrease successively; the optimum process parameters obtained after optimization are consistent, pulse width 8μs, pulse interval 10μs, servo voltage 38V.

Effect of stator height change on bearing life in aircraft autopilot servos

PurposeThe purpose of this paper is to make a more precise prediction of the life of servo motors used in aircraft. The variation of the axial load created by the wave washer for bearing, which is one of the factors affecting the bearing life of the electric motors and servo motors used in aircraft, was analyzed.Design/methodology/approachIn electric motors and servo motors that body as stator, the height of the stator stack affects the compression amount of the wave washer spring. Working with electric motor and servo manufacturers, production-related variations in stator height were determined by making multiple measurements. The reaction forces resulting from these compression amounts were simulated by mathematical modeling with the finite element method, and also experimentally measured on real parts.FindingsResults obtained with finite element method and real experiments were compared. By adding the force differences to the general operating conditions, the effect on the bearing life was theoretically determined. In a servo motor with this type of construction, the difference in stator height created different axial loads on the motor shaft. The difference of these loads affected the motor bearing life.Research limitations/implicationsThe results implicated in terms of flight safety, maintenance operation and resource efficiency.Practical implicationsThe results of this study are effective in determining the maintenance intervals more clearly. This study can be used for the design criteria of aircraft servo motors. These servos, which are especially used to move the flight control surfaces, contribute to flight safety as the life expectancy will be clearer.Social implicationsThis study may be effective in preventing aviation accidents caused by servo motors. It can make maintenance management more efficient.Originality/valueThis study investigated the effect of aircraft servo motor design inputs on servo motor life, considering the production.

A modified Sage-Husa adaptive Kalman filter for state estimation of electric vehicle servo control system

Kalman filter algorithm is widely used in state estimation of electric vehicles (EV) servo system as dynamic estimation of power system. In order to improve the estimation effect of noise interference in engineering practice, a scheme of Modified Sage-Husa adaptive Kalman filter (MSHAKF) combined with fuzzy clustering algorithm is proposed. The scheme processes the experimental data in a robust and adaptive way through the combination of constantly changing fuzzy clustering and MSHAKF, so as to better represent the dynamic characteristics of EV. The simulation results show that this method has higher estimation accuracy than the traditional method on the premise of unknown disturbance and noise characteristics in the system, and is more in line with the practical application of EV.

Characteristics of Hydraulic and Electric Servo Motors

Until the 1970s, hydraulic actuators were widely used in many mechanical systems; however, recently, electric motors have become mainstream by virtue of their improved performance, and hydraulic motors have largely been replaced by electric motors in many applications. Although this trend is expected to continue into the future, it is important to comprehensively evaluate which motor is most suitable when designing mechanical systems. This paper presents the results of a survey of the performance of electric and hydraulic servo motors and aims to provide quantitative data that can be used as a reference for selecting appropriate motors. We surveyed AC, AC direct, brushless DC, and brushed DC electric motors and swash plate-type axial piston, bent axis-type axial piston, crank-type radial piston, and multistroke-type radial piston hydraulic motors. Performance data were collected from catalogs and nonpublic data. We compared and evaluated the characteristics of these diverse servo motors using indexes such as torque, rotating speed, output power, power density, and power rate.

A Performance Evaluation Method Based on Interval Evidential Reasoning Approach With Function Monotonicity

The performance of complex systems is closely related to their security and reliability. Accurate performance evaluation is critical for timely system maintenance. Since the system monitoring information obtained usually contains noise, using this information to evaluate the performance of the device may result in inaccurate results. Interval values are used to represent the uncertainty of the monitoring information containing noise in the case of small samples. The uncertainty in the evaluation results is divided into two categories: the uncertainty of the evaluation model and the uncertainty of the monitoring information. The effects of the two categories on the evaluation results and the monotonicity of the output results on the monitoring information and model parameters are quantitatively analyzed. To avoid the problem of interval expansion during model optimization, an IER optimization model based on the belief degrees of monitoring information is built, and the whole evaluation process is solved and optimized uniformly. The monotonicity analysis results simplify the solving process of the IER optimization model, which reduces the difficulty and complexity. Validity and normalization tests are performed on the belief structure of the evaluation results, eliminating the invalid and redundant parts, and obtaining the best interval range of the evaluation results. The effectiveness of the proposed method is verified by its application in an electric servo mechanism.

A New Adaptive Interpretable Fault Diagnosis Model for Complex System Based on Belief Rule Base

This paper develops a new adaptive interpretable fault detection and diagnosis model (AIFD ) based on belief rule base (BRB) for complex system. The developed AIFD model aims to solve three problems in engineering practice: few fault samples, complex system mechanism and loss of interpretability in modeling process. The first two problems can be addressed by fusing expert knowledge and observation data in the BRB expert system. Moreover, to address the problem of loss of interpretability of AIFD model in its modeling process, a new belief rule weight adjustment method is proposed based on its sensitivity coefficient. The new adjustment method can improve the confidence degree of the users to the FDD output. The developed adjustment method can guarantee the fault diagnosis accuracy and the model interpretability. Then, to further address the influence of uncertain expert knowledge, a new optimization model is developed for the BRB based fault diagnosis model. To illustrate the effectiveness of the developed model, a case study of electric servo mechanism is conducted in this paper.

Fault Identification in Electric Servo Actuators of Robot Manipulators Described by Nonstationary Nonlinear Dynamic Models Using Sliding Mode Observers.

The problem of fault identification in electric servo actuators of robot manipulators described by nonstationary nonlinear dynamic models under disturbances is considered. To solve the problem, sliding mode observers are used. The suggested approach is based on the reduced order model of the original system having different sensitivity to faults and disturbances. This model is realized in canonical form that enables relaxing the limitation imposed on the original system. Theoretical results are illustrated by practical example.

Application of two-phase hybrid stepping motor based on three-phase inverter chopping control strategy in aircraft electric drive servo valve

With the development of multi-/all-electric technology, more and more aircraft platforms use electrically driven servo valves as the driving source to realize real-time adjustments of flow, pressure and temperature in the area network. The new generation of aircraft applies a stepper motor to drive the servo valve as the drive source, and utilizes the holding torque and open-loop control characteristics of the stepper motor when the stepper motor could not meet aircraft’s requirements of the reliability of the servo valve, the controllability of the opening and closing angle, and the environmental resistance. This paper develops a set of stepper motor drive servo valve control system. The system is mainly composed of flight tube bus, electromechanical management computer, remote actuation unit, remote interface unit and motor-driven servo valve. The stepper motor driver is integrated in the remote execution unit and is used to control the two-phase hybrid stepper motor to drive the servo valve. The topology of a three-phase inverter bridge drive is used to achieve the two-phase double four-shot drive, which saves about 25% power drive hardware. By controlling the two-phases motor, the direction and amplitude of the current one can realize micro-step control. The test and simulation result show that the system has higher control accuracy and better acceleration. The deceleration characteristics in two-phase full step and micro step working modes can expand the application of electric servo valve and improve aircraft performance.