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Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study introduces a decentralized control framework designed to improve energy efficiency in vehicle platooning by optimizing inter-vehicle gaps to minimize aerodynamic drag, a significant factor in energy consumption. The proposed framework integrates extremum seeking control (ESC), a proportional integral derivative controller with feedforward compensation (PIDFC), and an extended state observer for estimating aerodynamic drag coefficients. Through this integration, the ESC dynamically adjusts inter-vehicle gaps to minimize the drag force based on the estimated aerodynamic drag coefficients, while the PIDFC ensures precise tracking of the optimized gaps and effectively addresses disturbances arising from aerodynamic variations. The results show that the proposed ESC with PIDFC converged to the optimal distance gaps 37.14% faster than the ESC with PPC, within a steady-state error of ± 1 % . Additionally, it improved the computational efficiency by 70.6%, compared to the ESC with PPC. Furthermore, it reduced the energy consumption by 15.3%, compared to the fixed-gap approach. These findings demonstrate the framework's potential to enhance the energy efficiency, scalability, and practicality, advancing sustainable and autonomous transportation systems. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic decoupling and compensation approach to eliminate channel interaction for a multi-axis hydraulic road simulator. Misalignment of the concentrated moving mass centroid on the entire test bench with the control point and inconsistencies in actuator dynamics leads to dynamic coupling, which deteriorates the motion performance of the system. To solve the problem, an inverted decoupling and compensation network based on an identification model is proposed. Firstly, the system is modeled using the recursive extended least square (RELS) identification method. In the feedforward compensation modeling process, the steady-state inverse is obtained using zero-magnitude error technology control (ZMETC). In addition, a finite impulse response (FIR) filter with an adaptive algorithm is employed to reduce the adverse impact of the modeling error. The proposed decoupling strategy is validated by conducting experiments using a multi-axis hydraulic road simulator. The experimental results indicate that the designed compensator can effectively decrease the cross-coupling of multi-input and multi-output (MIMO) systems. The suggested approach is also applicable to applications that necessitate the elimination of interactions between different control variables. [ABSTRACT FROM AUTHOR]

This paper explores the cooperative control of unmanned surface vessels (USVs) and unmanned aerial vehicles (UAVs) in maritime rescue and coastal surveillance. The USV-UAV system faces challenges of disturbances and substantial inertia-induced overshooting during path following. A novel position prediction line of sight (LOS) guidance law is proposed to address these issues for USV path following control. Radial basis function-based neural networks (RBF-NNs) are used to estimate disturbances, and a high-order differentiator is used to design a velocity observer for unknown USV velocity. The UAV control system employs proportional–derivative (PD) control with feedforward compensation for quadrotor control design and utilizes a finite-time converging third-order differentiator to differentiate non-continuous functions. The simulation results demonstrate strong robustness in the proposed USV-UAV cooperative control algorithm. It achieves path following control in the presence of wind and wave disturbances and exhibits minimal overshoot. [ABSTRACT FROM AUTHOR]

Given the contradiction between compensating speed and compensating overshoot in traditional Proportional Integral (PI) control of Dynamic Voltage Restorer (DVR), A Feedforward compensation-active Disturbance Rejection Control (FC-ADRC) strategy based on Feedforward Compensation is proposed. ADRC control is used to improve the problem of compensating oversets existing in traditional PI control, and the voltage and current of the LC filter are introduced as the feedforward quantity to compensate the DVR controller to realize the rapid voltage compensation for the voltage dip on the user side and ensure the safety and stability of the voltage on the user side. The simulation results show that the proposed control strategy not only keeps the high dynamic response of the DVR device but also ensures the device’s adaptability to deal with uncertain disturbances.

Abstract A high‐order improved model free adaptive control method based on iterative learning is designed to address the problem that primary permanent magnet linear motor has poor control performance, susceptibilities to load disturbances and other nonlinear disturbances during operation. The proposed algorithm adopts an improved dynamic linearization model and high‐order pseudo partial derivative estimation algorithm, which improves the data utilization of the data‐driven control algorithm, makes the algorithm better to describe the dynamic behaviour of the primary permanent magnet linear motor direct thrust force control system and improves the speed tracking accuracy and anti‐interference ability of the system. In addition, iterative learning control was adopted as feedforward compensation to further improve the control performance of the system and the stability of the closed‐loop system was analysed analytically. The simulation results show that the proposed control algorithm can improve the control accuracy of the system and suppress load disturbances and other nonlinear disturbances.

Based on the design concept of dynamic and static isolation, disturbance-free payload (DFP) satellites can isolate the effects of interference on sensitive payloads, and can realize the high-precision control of the payload better than a traditional spacecraft. Among these, non-contact annular electromagnetic stabilized spacecraft (NCAESS) can effectively alleviate control output problems such as the six-degree-of-freedom coupling and nonlinear effects found in traditional non-contact spacecraft. As a key actuator, the driving current control of the non-contact annular electromagnetic actuator (NCAEA) will have a direct impact on the attitude performance of NCAESS. However, there are multiple interference effects present in the actual driving current control. Therefore, this paper proposes a composite control scheme to improve the driving accuracy by suppressing these multiple disturbances. Firstly, the variable-switching-frequency pulse-width modulation is used to adjust the switching frequency adaptively to reduce switch ripple. Secondly, feedforward compensation is employed to mitigate the back electromotive force. Thirdly, the robust Smith predictor is utilized to compensate for the digital control delay. Finally, an internal model proportional–integral controller with fuzzy rule is applied to adjust the parameters adaptively. The numerical simulation results demonstrate that the proposed approach can be adopted to enhance the robustness and dynamic response of the driving current effectively, which leads to precise control of the non-contact annular electromagnetic stabilized spacecraft. [ABSTRACT FROM AUTHOR]

A high‐order improved model free adaptive control method based on iterative learning is designed to address the problem that primary permanent magnet linear motor has poor control performance, susceptibilities to load disturbances and other nonlinear disturbances during operation. The proposed algorithm adopts an improved dynamic linearization model and high‐order pseudo partial derivative estimation algorithm, which improves the data utilization of the data‐driven control algorithm, makes the algorithm better to describe the dynamic behaviour of the primary permanent magnet linear motor direct thrust force control system and improves the speed tracking accuracy and anti‐interference ability of the system. In addition, iterative learning control was adopted as feedforward compensation to further improve the control performance of the system and the stability of the closed‐loop system was analysed analytically. The simulation results show that the proposed control algorithm can improve the control accuracy of the system and suppress load disturbances and other nonlinear disturbances. [ABSTRACT FROM AUTHOR]

Normal-stressed electromagnetic actuator (NSEA) has been demonstrated promising for nanopositioning stages running in hundreds of micrometers. However, system nonlinearities and their influences on the actuation behavior in NSEA have not been well revealed, blocking the in-depth understanding and high-performance application of the NSEAs. This paper developed an intrinsic electromagnetic actuation model by systematically including the nonlinear position-varying flux leakages, nonlinear flux density related to the field strength (B-H curve), and magnetic saturation. Based on the model, the influences of those nonlinear factors on the actuation were characterized theoretically. Experiments well verified the theoretical model and further characterized the dynamic hysteresis in the actuation. Finally, a phenomenological Wiener model cascading linear system dynamics with a least-squares support-vector machine (LS-SVM) model was developed for the feedforward compensation for system nonlinearities. The maximum modeling error was less than ± 4 % for the excitation with frequency ranging from 25 Hz to 200 Hz. Tracking of a complex trajectory combining multiple harmonics with various frequencies and randomly chosen amplitudes exhibited a maximum tracking error of ± 0. 7 μ m , which was only 28% of that without compensations. The results demonstrated the effectiveness of the proposed nonlinear compensation strategy for NSEAs. [Display omitted] • Intrinsic factors dominating the actuation nonlinearity are investigated for NSEAs. • Effect of the system nonlinearity on its actuation is theoretically investigated. • The nonlinearity for a NSEA stage is demonstrated experimentally. • A phenomenological model was developed for describing the system nonlinearity. [ABSTRACT FROM AUTHOR]

Synchronous vibration caused by rotor eccentricity is an important obstacle to the development of an active magnetic bearing (AMB) system. To solve this problem, a novel autobalancing control strategy has been proposed, which includes a static learning process and dynamic feedforward current injection process. In this algorithm, a dynamic response process under unbalanced force is simulated by a static learning process. Then, a transfer function containing amplitude and phase information is obtained. According to the obtained transfer function information, a specific feedforward current is constructed to eliminate the synchronous component in the control current and realize the autobalancing of vibration displacement. Computational complexity compared with conventional control strategies is further investigated. Moreover, the velocity sensor is no longer needed in the proposed control strategy. The simulation and experimental results of the AMB system show that the synchronous component of the control current and the amplitude of the rotor vibration displacement can be significantly reduced. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a low-voltage CMOS four-stage amplifier operating in the subthreshold region. The first design technique includes the cross-feedforward positive feedback frequency compensation (CFPFC) for obtaining better bandwidth efficiency in a low-voltage multi-stage amplifier. The second design technique incorporates both the bulk-drain-driven input stage topology in conjunction with a low-voltage attenuator to permit operation at a low voltage, and improves the input common-mode range (ICMR). The proposed circuit is implemented using TSMC-40 nm process technology. It consumes 0.866 μW at a supply voltage of 0.5 V. With a capacitive load of 50 pF, this four-stage amplifier can achieve 84.59 dB in gain, 161.00 kHz in unity-gain bandwidth, 96 deg in phase margin, and 5.7 dB in gain margin whilst offering an input-referred noise of 213.63 n V / H z @1 kHz, small-signal power-bandwidth FoMss of 9.31 (MHz∙pF/μW), and noise-power per bandwidth-based FoMnpb of 1.15 × 10−6 (( µ V / H z )·µW/Hz). Compared to the conventional bulk-driven input stage design technique, it offers improved multi-parameter performance metrics in terms of noise, power, and bandwidth at a compromising tradeoff on ICMR with respect to bulk-driven amplifier design. Compared with conventional gate-source input stage design, it offers improved ICMR. The amplifier is useful for low-voltage analog signal-processing applications. [ABSTRACT FROM AUTHOR]

This paper presents a low-voltage CMOS four-stage amplifier operating in the subthreshold region. The first design technique includes the cross-feedforward positive feedback frequency compensation (CFPFC) for obtaining better bandwidth efficiency in a low-voltage multi-stage amplifier. The second design technique incorporates both the bulk-drain-driven input stage topology in conjunction with a low-voltage attenuator to permit operation at a low voltage, and improves the input common-mode range (ICMR). The proposed circuit is implemented using TSMC-40 nm process technology. It consumes 0.866 μW at a supply voltage of 0.5 V. With a capacitive load of 50 pF, this four-stage amplifier can achieve 84.59 dB in gain, 161.00 kHz in unity-gain bandwidth, 96 deg in phase margin, and 5.7 dB in gain margin whilst offering an input-referred noise of 213.63 nV/Hz @1 kHz, small-signal power-bandwidth FoMss of 9.31 (MHz∙pF/μW), and noise-power per bandwidth-based FoMnpb of 1.15 × 10−6 ((µV/Hz)·µW/Hz). Compared to the conventional bulk-driven input stage design technique, it offers improved multi-parameter performance metrics in terms of noise, power, and bandwidth at a compromising tradeoff on ICMR with respect to bulk-driven amplifier design. Compared with conventional gate-source input stage design, it offers improved ICMR. The amplifier is useful for low-voltage analog signal-processing applications.

This paper explores the cooperative control of unmanned surface vessels (USVs) and unmanned aerial vehicles (UAVs) in maritime rescue and coastal surveillance. The USV-UAV system faces challenges of disturbances and substantial inertia-induced overshooting during path following. A novel position prediction line of sight (LOS) guidance law is proposed to address these issues for USV path following control. Radial basis function-based neural networks (RBF-NNs) are used to estimate disturbances, and a high-order differentiator is used to design a velocity observer for unknown USV velocity. The UAV control system employs proportional–derivative (PD) control with feedforward compensation for quadrotor control design and utilizes a finite-time converging third-order differentiator to differentiate non-continuous functions. The simulation results demonstrate strong robustness in the proposed USV-UAV cooperative control algorithm. It achieves path following control in the presence of wind and wave disturbances and exhibits minimal overshoot.

The current farming platform has been widely equipped with unmanned four-wheel independent driving and fourwheel independent steering (4WID-4WIS). However, the control system of path tracking is required for high accuracy and sufficient stability under complex working conditions. There were also complex working conditions under crop ridge cultivation, such as Π type target path, curves, initial pose deviation, various soil moisture, and bumpy ground landscapes. In this study, a control strategy of path tracking was proposed using a nonlinear disturbance observer (NOB). A mathematical insitu steering model was introduced for the relatively low tracking errors in the turn area of the Π type path, compared with the traditional Ackerman steering model. Two steering methods were then used to realize the turn path tracking. Meanwhile, a switch control strategy was designed between yaw angle proportional integral control and pure pursuit control using in-situ steering. Furthermore, the curve and initial pose deviation shared a relatively significant impact on the accuracy of working path tracking. Moreover, the distance traveled by the 4WID-4WIS farming platform was reduced to reach the working path and the maximum lateral deviation. The tracking accuracy of the work paths was improved to design a pure pursuit control using a lookahead distance function, and a fuzzy proportional compensator using the lateral deviation, as well as the curvature of the foresight area in the work path. Besides, the feedforward compensator with NOB was designed to avoid the relatively large yaw speed disturbances from the complex soil moisture, bumpy ground landscapes, kinematic models, and measurement errors. The NOB was also constructed to achieve the precise observation of disturbance for the expected path of farming platforms. The steering compensation angle was then calculated for the feedforward compensator to counteract the disturbance. Finally, the simulation was carried out in the Ubuntu/ROS environment. The NOB strategy of path tracking effectively reduced the distance traveled by farming platforms to reach the working paths, the maximum lateral deviation, and curve tracking errors. The accuracy and stability of path tracking were achieved in the anti-interference performance, where the disturbance momentum was observed accurately. And, the outdoor experiments show that the switch control strategy performed a smaller error of turn tracking on Π type target path, compared with the traditional pure pursuit control. The tracking performance was also effectively improved. The pure pursuit with the look-ahead distance function and fuzzy proportional compensator under different initial pose deviation states reduced the distance traveled by farming platforms to reach the working paths by 32.2%- 43.4%. The maximum lateral deviation, mean absolute errors of the whole line and curved area were reduced by 0-42.4%, 27.7%-49.5%, and 33.7%-39.5%, respectively, indicating the high accuracy of working paths tracking. The NOB-based feedforward compensator was reduced by 6.25% mean absolute error in the steady area under hard slate condition, 33.3% under grassland condition, and 41.7% under farmland condition. This control strategy of path-tracking effectively improved the system's robustness and path-tracking accuracy. The finding can also provide innovative ideas and technical references for the navigation system of unmanned four-wheel drive and four-rotation agricultural machinery in ridge tillage. [ABSTRACT FROM AUTHOR]

The motion process of legged robots contains not only rigid-body motion but also flexible motion with elastic deformation of the legs, especially for heavy loads. Hence, the characteristics of the flexible components and their interactions with the rigid components need to be considered. In this paper, a hierarchical control strategy for robots with rigid–flexible coupling characteristics is proposed. This strategy involves (1) leg force prediction based on real-time motion trajectories and feedforward compensation for the error caused by flexible components; (2) building upon the centroid dynamics model of the rigid-body chassis, the centroid trajectories (centroid angular momentum (CAM) and centroid linear momentum (CLM)) and the body trajectory are taken into account to derive the optimal drive torque for maintaining body stability; (3) finally, the precise force control of the hydraulic drive units is achieved through the sliding mode control algorithm, integrating the dynamic model of the flexible legs. The proposed methods are validated on a giant hexapod robot weighing 3.5 tons, demonstrating that the introduced approach can reduce the robot's vibrations. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

One of the most popular power management regulators is the low drop-out voltage regulator (LDO). LDOs have different specifications such as the power supply rejection (PSR) over different frequencies, stability over different load ranges, inrush current spike flows through the input supply, and power consumption. In this work, we present a low power low inrush current LDO design with different techniques for PSR and stability improvement across different frequencies. The LDO presented in this work is a low-power and small area LDO but achieves a high PSR over a wide range of frequencies. The LDO is designed in 65 nm CMOS technology and achieves a PSR better than 80 dB up to 30 MHz for an output load current of 25 mA using an output load capacitor of 4 µF. The design can be used in capless/capped LDOs with wide load current ranges as high as 200 mA and load capacitor range from 1 nF to 12 µF with inrush current improvement by more than 2×. The presented LDO consumes a zero-load quiescent current of 10 µA and its area of 180 µm × 180 µm.

Based on the design concept of dynamic and static isolation, disturbance-free payload (DFP) satellites can isolate the effects of interference on sensitive payloads, and can realize the high-precision control of the payload better than a traditional spacecraft. Among these, non-contact annular electromagnetic stabilized spacecraft (NCAESS) can effectively alleviate control output problems such as the six-degree-of-freedom coupling and nonlinear effects found in traditional non-contact spacecraft. As a key actuator, the driving current control of the non-contact annular electromagnetic actuator (NCAEA) will have a direct impact on the attitude performance of NCAESS. However, there are multiple interference effects present in the actual driving current control. Therefore, this paper proposes a composite control scheme to improve the driving accuracy by suppressing these multiple disturbances. Firstly, the variable-switching-frequency pulse-width modulation is used to adjust the switching frequency adaptively to reduce switch ripple. Secondly, feedforward compensation is employed to mitigate the back electromotive force. Thirdly, the robust Smith predictor is utilized to compensate for the digital control delay. Finally, an internal model proportional–integral controller with fuzzy rule is applied to adjust the parameters adaptively. The numerical simulation results demonstrate that the proposed approach can be adopted to enhance the robustness and dynamic response of the driving current effectively, which leads to precise control of the non-contact annular electromagnetic stabilized spacecraft.

Electromagnetic linear load simulator (ELLS) is a device that simulates the load force on the load bearing object. This paper proposes a new compound control method based on the combination of neural network algorithm and feedforward compensation principle to improve force loading performance of ELLS. First, the mathematical model of the force loading system and the problem formulation is introduced. Then, radial basis function (RBF) neural network algorithm, single neuron proportional–integral–derivative (PID) control algorithm, and feedforward compensation principle are presented. Based on these control theories, a compound controller is designed and the block diagram of the proposed method for force loading system is presented. In order to verify the superiority of compound control, different control methods are compared in simulation and experiment under different operating conditions. It is clearly demonstrated that the proposed compound control method has better dynamic and static characteristics, and meet the established control requirements. [ABSTRACT FROM AUTHOR]

One of the most popular power management regulators is the low drop-out voltage regulator (LDO). LDOs have different specifications such as the power supply rejection (PSR) over different frequencies, stability over different load ranges, inrush current spike flows through the input supply, and power consumption. In this work, we present a low power low inrush current LDO design with different techniques for PSR and stability improvement across different frequencies. The LDO presented in this work is a low-power and small area LDO but achieves a high PSR over a wide range of frequencies. The LDO is designed in 65 nm CMOS technology and achieves a PSR better than 80 dB up to 30 MHz for an output load current of 25 mA using an output load capacitor of 4 µF. The design can be used in capless/capped LDOs with wide load current ranges as high as 200 mA and load capacitor range from 1 nF to 12 µF with inrush current improvement by more than 2×. The presented LDO consumes a zero-load quiescent current of 10 µA and its area of 180 µm × 180 µm. [ABSTRACT FROM AUTHOR]

Aiming at the difficulty of temperature control and disturbance rejection control in wave rotor refrigeration process (WRRP), a novel whale optimization two‐degree‐of‐freedom (2DOF) Smith predictor based on feedforward compensation method (WO‐2DOFSP‐FC) is proposed. Firstly, the obtained test data of the WRRP are used for system identification and the approximate second‐order model with time‐delay is obtained by using the suboptimal reduction algorithm. This procedure also yields a first‐order model of the disturbance. Then, the whale optimization 2DOF Smith predictor based on feedforward compensation (2DOFSP‐FC) method is proposed. This proposed method improves the 2DOFSP and introduces feedforward compensation control to reduce the influence of the measurable disturbance on the temperature control system. In addition, the Whale Optimization Algorithm (WOA) is proposed to optimally tune the 2DOFSP‐FC controller parameters. Finally, the simulation results show that the proposed WO‐2DOFSP‐FC method can make the controlled system have good characteristics of both set value tracking and disturbance rejection. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For the spherical robot, an efficient and precise velocity controller suitable for different terrains is crucial. In this paper, a new Riccati controller with feedforward compensation based on Kalman observer (FKO-Riccati controller) with better control performance and stronger robustness is proposed for velocity control of the spherical robot. An accurate dynamic model of the robot is established. Based on the model, a Riccati controller with velocity tracking performance and a Kalman velocity observer are proposed, and the output is feedforward compensated. To verify the effectiveness of the proposed controller, a series of experiments were conducted using a spherical robot named Rotunbot. The simulations and experimental results show that no matter what terrain the robot was in, compared with the traditional PID controller, the FKO-Riccati controller had better control performance and stronger robustness, whether it was going straight or turning. [ABSTRACT FROM AUTHOR]

Hydro-mechanical transmission (HMT) is one type of mechanical-hydraulic stepless transmission. There is a better tradeoff between the stepless speed regulation of hydraulic and efficient speed change of mechanical transmission. Clutch control is closely related to the appropriate timing of engagement and separation, due to the great influence of disturbance on the quality of the shifting process. It is necessary to clarify the shifting clutch for the higher quality of HMT during shifting. However, a strong nonlinear system is coupled with the HMT under modeling error and external load disturbance. In this study, the shifting clutch pressure control was proposed using disturbance feedforward compensation. The dynamical model of shifting and the mathematical model of the clutch in the sliding were also established using the composition and working principle of HMT. The optimal linear-quadratic model was achieved, where the jerk, sliding power, and shifting time were taken as the evaluation indexes during shifting, while the performance index of the quadratic function was the state control variable. The total disturbance during shifting was also estimated to rapidly respond to the disturbance using the first-order disturbance observer. The compensation gain of disturbance was introduced into the feedforward term of the controller, in order to realize the disturbance feedforward compensation. After that, the feedforward compensation gain was obtained, according to the disturbance estimate d and compensation coefficient kd . Then, the optimal controller was designed to suppress the disturbance of the shifting process for the optimization of the quadratic index. The functional weight coefficients were set as q = 1, and r =0.1, the equivalent moment of the inertia of the HMT input shaft, clutch C2 driven disc, quantitative motor output shaft, and HMT output shaft were set as 0.02, 0.04, 0.05, and 1 kg·m², respectively, while the equivalent damping coefficients were set as 0.015, 0.2, 0.018, and 0.016 N·m·rad/s, respectively. The co-simulation of HMT during shifting with disturbance was carried out in the AMEsim and Simulink software. The coefficients, kx, kh, and kd of the optimal control variables were calculated by the simulation model in real time. The simulation indicated that the improved control system reduced the maximum disturbance by 48.9%, the jerk by 27.8%, the sliding friction work by 29.6%, and the shifting time by 15.3%, compared with the control without disturbance feedforward compensation. Better control was achieved in the time-varying disturbance of the shifting process. The test of the hydraulic mechanical transmission was also carried out on the test bench, in order to verify the effectiveness of the control system for the better quality of HMT during shifting. Among them, the output load torque and input speed were set as 1000 N·m, and 1 500 r/min, respectively. Test results show that there was a consistent trend of experiment and simulation, although some error was under control. Consequently, the disturbance feedforward compensation greatly reduced the maximum jerk and shifting time, while suppressing the time-varying disturbance during shifting. The disturbance of the shifting was effectively estimated to better improve the shift quality of HMT under the disturbance working condition. The findings can provide a strong reference for the engineering application of hydraulic mechanical transmission. transmission. [ABSTRACT FROM AUTHOR]

For assisting the daily lives of the elderly or patients with abnormal walking by hemiplegia, wearable robots which are constructed with relatively soft materials such as cable-driven method are being actively developed and partially commercialized. The main advantage is that the flexible power transmission system could distribute the inertia of the distal area, which is essential for stabilizing the gait balance. However, in flexible power transmission system, it has disadvantage that it cannot directly measure the tension applied to the patients. Therefore, tension measurement device on the assisting point is required for generating precise assistance on the patients. But adding the tension measuring device is challenging because it increases complexity and inertia. The main factor for inaccurate force transmission is the unpredictable friction from the transmission cable's varying curvature in human motion. In this paper, a methodology of design and control of reaction force-based series elastic actuator is proposed to generate the precise assistive force at the actuating module while maintaining the overall weight small. The mechanical elements of Series Elastic Actuator are designed with the optimal specifications required for stroke patient assistance. The compactness and weight reduction are also guaranteed by designing the mechanical elements with optimal specifications, which enables assisting the patients with minimal gravitational load. Furthermore, periodic friction compensation is done through experiments by using feedforward compensator, which adjusts the corresponding loss, linked with the estimated gait phase. Therefore, even in the presence of friction loss in the cable, application of precise torque at the end-effector became possible. [ABSTRACT FROM AUTHOR]

Under the effects of uncertain parameters and external disturbances, the attitude and trajectory tracking accuracy will be reduced and the response will be slowed down in the flight control of quadrotor unmanned air vehicles (UAVs). To solve this problem, the extended Kalman filter method was used given its excellent adaptability and noise suppression ability for nonlinear systems, to preliminarily estimate the quadrotor state information and suppress the high-frequency signal disturbance to reduce the estimation burden on the extended state observer. Moreover, the extended Kalman filter combined with the expanded state observer was applied to estimate the total disturbance composed of the system uncertainty parameters and external disturbances to reduce system reliance on precise models, and the differential values of the perturbation estimates were used for feedforward compensation to improve the tracking accuracy under abrupt disturbances and to overcome the phase lag caused by abrupt disturbances. The joint state observer, the linear extended state observer with feedforward compensation and the PD controller with error compensation were integrated to form an improved active disturbance rejection controller to jointly observe disturbances while suppressing high-frequency noises and abrupt disturbances to a relatively large extent, by means of the extended Kalman filter and the extended state observer with feedforward compensation. Simulation and experiment results show that, the joint observer can effectively reduce the observation error amplitude, correct the observation phase lag in advance and obtain more accurate state information, and the improved active disturbance rejection controller can better meet requirements of quadrotor UAVs for fast responses and stable control, and accurately and efficiently fulfill complex trajectory tracking tasks. [ABSTRACT FROM AUTHOR]

Copyright of Electric Drive is the property of Electric Drive Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, a fault-tolerant three-phase induction drive based on field-oriented control is studied, and an analytical approach is proposed to elucidate the limitations of FOC in flux-torque regulation from the controller perspective. With an open-phase fault, the disturbance terms appear in the controller reference frame and degrade the controller performance when operating in a d-q plane with DC quantities. In addition, the hardware reconfiguration, which is essential to operate faulted three-phase drives, causes substantial change in the way the control parameters vd, vq are reflected onto the machine terminals. An accurate understanding of the feedforward term, by considering the open-phase fault and the hardware modifications, is provided to re-enable the FOC in presence of an open-phase fault. Furthermore, the concept of feedforward term derivation is generically extended to cover multiphase induction drives encountering an open-phase fault whereby no hardware reconfiguration is intended. The proposed method is explained based on a symmetrical six-phase induction and can be extended to drives with a higher number of phases. The effectiveness of the proposed derivation method, which is required to form a feedforward fault-tolerant controller, is verified and compared through the simulation and experiment, ensuring smooth operation in postfault mode. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract In this paper, double PWM converter AC excitation system of the variable speed constant frequency doubly fed induction generator (DFIG) for wind power generation is taken as the research object. At present, most vector control systems of rotor‐side PWM converter adopt feedforward compensation to realize the purpose of power decoupling control. The decoupling effect is greatly affected by the power changes. A power decoupling control strategy based on auto‐disturbance rejection control (ADRC) is proposed. The decoupling control between active power and reactive power is realized by observing the coupling term and the total disturbance of the d‐axis and q‐axis components of the stator current and the stator voltage with the extended state observer and compensating. Simulation analysis and experimental test show that, on the basis of vector transformation, the rotor‐side PWM converter power decoupling control based on ADRC has a small overshoot and fast dynamic response when tracking the change of wind turbine input power, which can achieve the decoupling control between active power and reactive power well. The system has strong robustness and adaptability.

To meet the progressively stringent demands for trajectory tracking performance in precision/ ultra-precision industry, multiple advanced feedforward compensation strategies have been reported in recent years. However, there is no fair and comprehensive performance comparison of advantages and drawbacks of various methods under different industrial working conditions. In this paper, a comparative study of several performance-oriented feedforward strategies represented by standard iterative learning control (ILC), cascaded ILC (CILC), gated recurrent units based feedforward compensation (GRU-FFC), and real-time iterative compensation (RIC) has been systematically conducted by theoretical clarification and experimental verification. Various trajectory tracking tasks are accomplished on a precision mechatronic motion stage, and the tracking performances to be examined include (i) tracking accuracy; (ii) extrapolation capability for non-repetitive trajectories; (iii) disturbance rejection ability. Experimental results are sufficiently summarized with the combination of underlying control mechanism analysis, which can provide a comprehensive and reliable selection guidance of feedforward compensation strategies in different practical industrial scenarios.

In order to optimize the performance of permanent magnet synchronous motor (PMSM) drives, a fractional-order sliding mode (FOSM) control scheme combining generalized proportional integral observer (GPIO) is adopted in this paper. A FOSM controller is firstly employed to reduce the negative effects of the load torque and parameter variations in the PMSM system. However, the FOSM control method mostly needs high control gain to moderate the unfavorable effects of the total disturbance, which will inevitably lead to large chattering phenomenon. Therefore, the unknown lumped disturbance is effectively estimated by using a GPIO, and the estimated value is synchronously compensated to the FOSM speed controller. Even if a smaller control gain is chosen, the robustness of the proposed composite GPIO-based FOSM controller is better than that of the FOSM controller. Finally, the effectiveness of the proposed control strategy is verified by comprehensive simulation and experimental results. [ABSTRACT FROM AUTHOR]

Wastewater Treatment Plants (WWTPs) are industrial facilities, which are important for the protection of the environment, because they remove pollutants from wastewater, before it reaches natural bodies of water. WWTPs consist of complex physical, chemical, and biological energy-intensive processes, which are subject to significant disturbances and uncertainties, due to large variations in the load and quality of the influent. Rising energy prices and increasingly stringent effluent requirements have amplified the need of developing more efficient control schemes for WWTPs. In this paper a novel Economic Dynamic Matrix Control (EDMC) configuration is proposed for WWTPs, where the objective is to minimize the plant's operating costs in terms of energy savings, while maintaining the effluent quality within acceptable regulatory limits. The novelty of the proposed scheme lies in the combination of the standard Dynamic Matrix Control (DMC) methodology, with economic oriented control strategies. The EDMC predictive models are derived from the application of step tests on the COST/IWA Benchmark Simulation Model No. 1 (BSM1). Based on the BSM1 model, the proposed method is compared to standard Multiple Input–Multiple Output (MIMO) DMC controllers, to the default BSM1 control strategy and to other economic control methods, which have been proposed in the literature. The results illustrate that the proposed EDMC scheme is superior to alternative control strategies in terms of minimizing the energy consumption while, the effluent quality of the plant is maintained at acceptable levels. • We propose a novel control method combining conventional DMC with concepts from Economic MPC. • The method is particularly tailored to the control of Waste Water Treatment Plants. • The method is based on data-driven models derived from step tests, so it can be applied easily in real-life scenarios. • Feasibility is tested on a benchmark model and compared to several other control methods proposed in the literature. [ABSTRACT FROM AUTHOR]

We propose a new method of image contour detection, considering the close relationship between binocular parallax in the biological vision system and the hierarchical transmission of visual channel information flow. Firstly, we present the dynamic adjustment mechanism of different opponent cell connection weights in a color channel to obtain the initial contour response diagram. Subsequently, we introduce the binocular parallax energy model to separate the image feature information to receive the response of position and phase differences; we then construct the end-stopped cells with different phases to extract the primary contour of the image to a significant extent. At the same time, we propose a multi-scale receptive field fusion strategy to suppress the local texture with multi-intensity. Finally, we use the feedforward mechanism across the hierarchy to refine the textured background and improve the primary contour contrast to obtain the final contour response. Our image processing method based on binocular parallax compensation can provide a new idea for subsequent studies on the higher visual cortex's image understanding and visual cognition. [ABSTRACT FROM AUTHOR]

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Conventional sensorless drives usually suffer from an unsatisfactory dynamic response to the varying speed reference or load disturbance due to the design only for the speed estimator. In this paper, an improved adaptive law based model reference adaptive system (IAL-MRAS) algorithm is proposed to enhance the dynamic performance of a surface-mounted permanent magnet synchronous motor (SPMSM) sensorless drives, in which both a speed/position estimator and composite speed controller are designed by a systematic way. This improved adaptive law (IAL) incorporates both the mechanical and electromagnetic model to account for the mechanical factors on the speed variation, which can estimate the rotor position and load torque simultaneously. To further strengthen the disturbance rejection ability, a composite speed controller is designed based on the feedforward compensation scheme and IAL-MRAS. Meanwhile, a hybrid control strategy combining IAL-MRAS and $I$ - $f$ starting method is adopted to realize sensorless control in the full speed range. Comprehensive numerical simulation and experimental results have fully demonstrated that the proposed sensorless control strategy can achieve smaller settling time, stronger disturbance rejection ability, and less parameter tuning workload than those of the conventional methods.