N -module permanent magnet synchronous motor (PMSM) drive systems are receiving increasing attention in wheel motor applications with high-reliability requirements. The torque ripple introduced by ...pulsewidth modulated voltage excitation, which is difficult to be eliminated by the current loop design, seriously affects the system performance. An adaptive optimal carrier phase shift method is designed in this article. Compared with the traditional average carrier phase shift method, the proposed method achieves optimal suppression of torque sideband harmonics even in subhealth submodule derating operation. Especially, a novel mathematical model of the torque sideband harmonics is developed for the N -module PMSM drive system. Then, two carrier phase shift methods are designed to optimize the carrier phase by combining structural characteristics to reduce the dimensionality of the optimization search. Furthermore, two optimization objectives are set: minimizing the peak value of the torque sideband harmonics and the amplitude of the torque sideband harmonics at a specific frequency. Based on the designed parallel grid search method, the best solution can be obtained with less computational stress. Finally, the proposed method's torque sideband harmonic suppression performance based on the optimal objective at different fundamental frequencies and output current is verified in a 5.6 kW four-module in-wheel motor drive system.
This text explores the evolution of the notion of trauma in Freud's work and of its decisive import for the organization of psychic functioning through a two-stage process called the après-coup. By ...following the three steps of Freud's theory of the drives, the author shows that the conception of the traumatic is gradually internalized to become a basic quality of all drives as a tendency to return to an earlier state, and ultimately an organic, inanimate state. An open question remains in Freud about this tendency's relation to Eros, and therefore to the links between Eros and the traumatic state. This question has remained latent within the psychoanalytic community. The author proposes to conceive of Eros as an infinitely extensible tendency that needs containing in order for it to contribute to evolving inscriptions. Thus is outlined one traumatic state as a return to the inorganic and another traumatic state as an infinite extensibility, both being transformed by the superego and its imperatives in order to generate all life forms.
Improving tractor traction efficiency is greatly important in increasing energy efficiency and reducing fossil fuel consumption. However, the wheeled tractors have problems with low traction energy ...efficiency and severe energy consumption due to excessive wheel slip in ploughing. This paper proposed a joint control method considering the travel speed and slip based on the active torque distribution, which is applied to the independent drive electric tractors. Considering the influence factors of time-varying resistance and terrain elevation in ploughing, a time-varying dynamical model for the tractor-implement combination was established to reveal the load transfer rules. Then the optimal slip values of the driving wheels were solved in real-time, and a sliding mode algorithm was used to control the motor torque for efficient tractor operation. Moreover, a hardware-in-the-loop platform was built, and ploughing tests were performed. The results indicated that the tractor slip, traction energy efficiency and motor energy consumption of the tractor were optimal in the torque active distribution mode. Compared to the torque average distribution mode, the proposed method reduced the tractor slip by 14.1%, the motor energy consumption by 6.8% and increased the traction energy efficiency by 6.8%. This study provided technical support for reducing energy dissipation in ploughing.
•A joint control method of travel speed and slip based on active torque control.•Accurate calculation of dynamic wheel load for tractor-implement combination.•Comparative analysis of hardware-in-the-loop tests in three control modes.•The tractor slip in the torque active distribution mode was reduced by 14.1%.•The driving motor energy consumption under ploughing was reduced by 7.3%.
High-performance actuators are crucial to enable mechanical versatility of wearable robots, which are required to be lightweight, highly backdrivable, and with high bandwidth. State-of-the-art ...actuators, e.g., series elastic actuators, have to compromise bandwidth to improve compliance (i.e., backdrivability). In this article, we describe the design and human-robot interaction modeling of a portable hip exoskeleton based on our custom quasi-direct drive actuation (i.e., a high torque density motor with low ratio gear). We also present a model-based performance benchmark comparison of representative actuators in terms of torque capability, control bandwidth, backdrivability, and force tracking accuracy. This article aims to corroborate the underlying philosophy of "design for control," namely meticulous robot design can simplify control algorithms while ensuring high performance. Following this idea, we create a lightweight bilateral hip exoskeleton to reduce joint loadings during normal activities, including walking and squatting. Experiments indicate that the exoskeleton is able to produce high nominal torque (17.5 Nm), high backdrivability (0.4 Nm backdrive torque), high bandwidth (62.4 Hz), and high control accuracy (1.09 Nm root mean square tracking error, 5.4% of the desired peak torque). Its controller is versatile to assist walking at different speeds and squatting. This article demonstrates performance improvement compared with state-of-the-art exoskeletons.
•Novel Operating Deflection Shape Ratio (ODSR) concept for drive-by bridge monitoring.•ODSR eliminates challenges associated with normalisation of traditional mode shapes.•Bridge damage quantified by ...measuring changes in ODSR.•Damage detected at high vehicle speeds and on smooth or rough pavement surfaces.•Laboratory experiments verify that the concept can be used to monitor changes in structural behaviour.
Large scale monitoring of bridge structures poses a significant challenge for infrastructure managers. This challenge could be overcome by using passing vehicles to monitor bridge condition. The operating deflection shapes of a bridge can theoretically be detected from in-vehicle measurements. This paper proposes a novel approach which introduces the concept of operating deflection shape ratios (ODSRs) from the responses measured on two following axles on a bridge. Unlike operating deflection shapes derived from drive-by measurements, ODSRs are non-dimensional values and are not a function of the bridge excitation level. This means that ODSRs are always constant for various vehicles passages. It is theoretically demonstrated in this study that ODSRs corresponding to each mode of bridge vibration can be approximately extracted from the responses of two following axles. Finite element modelling is employed to validate the feasibility of using ODSRs for bridge monitoring. The sensitivity of the ODSRs to damage is demonstrated numerically for damage at various locations, different vehicle speeds and different pavement roughness values. Laboratory experiments are then used to verify the theory in a practical environment. It is confirmed that the ODSR can be calculated from in-vehicle vibration measurements and can be used to detect changes in the structural behaviour of the bridge. The results of the study indicate that the ODSR represents a useful feature for drive-by bridge monitoring.
In this paper, winding topologies for one- and two-pole-pair rotors are analyzed and compared for a slotless bearingless disk drive with toroidal windings. The basis of the studies is a six-phase ...motor with a diametrically magnetized one-pole-pair rotor. Due to the absence of mechanical bearings and the significantly large air-gap capability, the motor is suitable for applications with high purity and special chemical demands. Its slotless design results in low losses even at high rotational speeds. To improve the operational behavior of the rotor in different applications, the influence of higher pole pair numbers on the passive bearing stiffness is examined. A possible winding configuration for these rotors is proposed and evaluated for their bearing and motor performance. Based on the results, a further prototype was built and is presented in this paper.
In European industry, such as metallurgical, mining and processing, construction, food, and chemical, vibration exciters are used, which indicates their wide and, in some cases, unique technological ...capabilities. The most common are electromagnetic and unbalanced vibration exciters. The advantages of electromagnetic vibration exciters include the ability to control the amplitude of the vibration by changing the electrical power supplied; the disadvantages are high material consumption. However, unbalanced vibration exciters have low energy efficiency, which is associated with difficult start-up conditions and with an overestimated mechanical power of the vibration exciter in relation to the power required by the technology itself, which is due to the need to minimize the effect of the technological load on the operating mode of the vibrating unit. Adjusting the amplitude of the disturbing force of unbalanced vibration exciters, regardless of the vibration frequency, will make it possible to reduce the installed power of the unit by passing the resonant frequency with a minimum disturbing force and compensating for the effect of the process load by means of a closed-loop electric drive. In the course of the study, an analytical description of the interaction of the rotating unbalances located on a common movable platform was obtained. On the basis of these analytical dependencies, a mathematical model was developed that takes into account the dynamic characteristics of a frequency-controlled asynchronous electric drive of a closed-loop control system for the mutual arrangement of rotating unbalances. The simulation results confirmed the possibility of using the specified electric drive to control the oscillation amplitude directly in the process of operation of a four-unbalanced vibration exciter. A physical experiment was carried out to determine the transient processes of changing the angular velocity of an induction motor with an abrupt change in the frequency converter setting. On the basis of this experiment, the previously created mathematical model was refined in terms of describing the dynamic parameters of the electric drive. The proposed structure of the control system, the performance of which has been confirmed by mathematical modeling, makes it possible to implement an adjustable four-unbalanced vibration exciter using single commercially available asynchronous vibrators.
This article presents the design and development of a 7-kV dc bus, 1-MVA, 0-1000 Hz modular multilevel converter (MMC) prototype for high speed medium-voltage variable frequency drives. The system is ...designed based on 1.7-kV silicon carbide (SiC) mosfet s. First, the full in-depth design of the prototype is provided, including the submodules, arm inductors, and system integration. Then, the unique control scheme and the control hardware design are presented to achieve the full-frequency range operation. The power loss based on Si and SiC devices is analyzed. Finally, experimental results are presented to demonstrate the performance of both the SiC-based submodule and the full-scale MMC system. Compared with the traditional Si-based solution, the established SiC MMC can reduce the drive system volume by 75% and achieve 325% power density, and the peak energy efficiency reaches around 99.35%.
This paper proposes a novel power-fed permanent magnet adjustable speed drive (PF-PMASD) to regulate the speeds of pumps and fans for energy saving. The drive features that the slip power induced in ...the wound rotor of the drive can be fed to the power grid by a power electronic converter. The structure, operation principle, and control strategy of the drive are introduced and investigated. The mathematical model of the PF-PMASD is built by referring to the models of the traditional permanent magnet synchronous machine and wound rotor induction motor, based on which the power-size equation for the drive is deduced. The losses and efficiencies of the drive under different slips are also calculated and evaluated. The relationships between the slip and the duty cycle of the insulated-gate bipolar transistor in the boost chopper are revealed by the mathematical model of the control unit. The steady characteristics including electromotive forces, phase currents, and torques under different operation states are computed and analyzed comprehensively by finite-element analysis. The speed regulation characteristics, the power factor, and the energy-saving capabilities of the drive are investigated by experimental test. The analysis results indicate that the proposed PF-PMASD possesses a remarkable speed regulation capability with high efficiency.
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•Anti-CRISPR proteins inhibit CRISPR-Cas systems and have been developed for many biotechnological uses.•Anti-CRISPRs have been used to control genome editing strategies to reduce ...unwanted outcomes and potentially improve safety.•Diverse subfields including gene drive development and synthetic biology have used anti-CRISPRs for their inhibitory properties.
In the ten years since the discovery of the first anti-CRISPR (Acr) proteins, the number of validated Acrs has expanded rapidly, as has our understanding of the diverse mechanisms they employ to suppress natural CRISPR-Cas immunity. Many, though not all, function via direct, specific interaction with Cas protein effectors. The abilities of Acr proteins to modulate the activities and properties of CRISPR-Cas effectors have been exploited for an ever-increasing spectrum of biotechnological uses, most of which involve the establishment of control over genome editing systems. This control can be used to minimize off-target editing, restrict editing based on spatial, temporal, or conditional cues, limit the spread of gene drive systems, and select for genome-edited bacteriophages. Anti-CRISPRs have also been developed to overcome bacterial immunity, facilitate viral vector production, control synthetic gene circuits, and other purposes. The impressive and ever-growing diversity of Acr inhibitory mechanisms will continue to allow the tailored applications of Acrs.
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