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Aiming at the problems of large torque fluctuation of drill bit and low weight-on-bit(WOB) transmission efficiency during the drilling process, a novel drilling tool generating constant torque and reducing stick-slip is proposed. For investigating the further dynamics behavior of drill string system, the mathematic models are established based on the new tool output characteristics. Also, compared with field test and application, the drilling tool effects on increasing ROP (rate of penetration) and reducing drill bit wear are verified. The research results show that the peak value of drill bit angular velocity increases gradually with the bigger value of the pre-compression of disk spring system, so as the rotary table inputting speed, during drill bit downward movement. About the drill string influence, the larger the length of drill string, the longer response time is the rotating angular velocity of drill bit. Another one, the shorter the steady time of drill bit angular velocity, the bigger ratio is the stick-slip within one period. This new drilling tool can effectively improve the drill bit force conditions, and reduce the stick-slip stage, which can also profitably increase drilling efficiency and the service life of downhole tools, especially in ultra-deep or long distance horizontal wells. [ABSTRACT FROM AUTHOR]

This paper investigates the properties and design of energy conversion in an electric vehicle (EV) powertrain. Here, we combined the dynamics of vehicle motion with controlled electric propulsion, which is an EV powertrain. The control of two types of permanent magnet synchronous motors (PMSMs) was considered. An algorithm was developed for the determination of the static characteristics of two-region motor torque control. A constant torque and a constant power region were used in the powertrain of the EV. The design of the control system for the PMSM was considered in the d , q reference frame. A precise mechanical model of the EV and the determination of road loads is shown. The main results of this study were the selection of the PI controller parameters (in analytical form), which was carried out for the simplified motor model and then extended for the d , q model, and energy consumption during the WLTP standard driving cycle. The presented simulation results of the proposed control system with synchronous motors in the EV (Fisker Karma as an example) confirmed the approach taken for the selection of the controller. The presentation of the EV's acceleration for an optimized powertrain, and hence its performance, is a novelty not found in other articles. [ABSTRACT FROM AUTHOR]

An electrohydrostatic actuator (EHA) system is one of the key components of electric aircraft flight controls. The EHA system with fixed pump displacement and variable motor (EHA-FPVM) is widely used because of its simple structure, but the power weight ratio of EHA-FPVM is small, although it is very important to an aircraft. A novel EHA with a constant-torque variable-displacement pump (CTVDP) is proposed and simulated; it can substantially decrease the maximum motor-rated torque while reducing the servo-motor volume and weight. First, the CTVDP structure of the EHA system is proposed and a constant-torque variable-displacement pump is designed. Second, mathematical models of the EHA system structure are developed and simplified according to the constant-torque displacement–pressure law. Third, an adaptive backstepping control algorithm is proposed to improve position-tracking performance in the presence of the uncertain viscous damping coefficient. Finally, numerical simulations prove that the EHA system with CTVDP structure can further decrease motor maximum torque by approximately 37.5% and is robust against load impact, pump displacement variation, and parameters uncertainty. The results of this study can serve as the foundation for future application. [ABSTRACT FROM AUTHOR]

In this work, we obtain an approximate analytical solution to a damped pendulum equation with constant torque. We also compare this solution both graphically and numerically with Runge-Kutta numerical solution. [ABSTRACT FROM AUTHOR]

In this paper, two cost functions are presented which are minimized to provide the optimized reference currents for the controlled drive of the synchronous reluctance motor. Since the synchronous reluctance motor operation is divided into two operating regions: one up to rated speed (0–1740 rpm), known as constant torque region and variable power, and other above this speed, called field weakening region (1740-2000 rpm), each of the cost functions proposals is appropriate for a specific region. The optimization problem is solved by the method of Lagrange Multiplier which allows finding the minimum value of a function with one or more constraints. The tests show a reduction in the motor current value of around 2%. [ABSTRACT FROM AUTHOR]

This paper investigates the properties and design of energy conversion in an electric vehicle (EV) powertrain. Here, we combined the dynamics of vehicle motion with controlled electric propulsion, which is an EV powertrain. The control of two types of permanent magnet synchronous motors (PMSMs) was considered. An algorithm was developed for the determination of the static characteristics of two-region motor torque control. A constant torque and a constant power region were used in the powertrain of the EV. The design of the control system for the PMSM was considered in the d,q reference frame. A precise mechanical model of the EV and the determination of road loads is shown. The main results of this study were the selection of the PI controller parameters (in analytical form), which was carried out for the simplified motor model and then extended for the d,q model, and energy consumption during the WLTP standard driving cycle. The presented simulation results of the proposed control system with synchronous motors in the EV (Fisker Karma as an example) confirmed the approach taken for the selection of the controller. The presentation of the EV’s acceleration for an optimized powertrain, and hence its performance, is a novelty not found in other articles.

The current state of the art in compliant actuation has already good performance, but this is still insufficient to provide a decent autonomy for the next generation of robots. In this paper, a next step is taken to improve the efficiency of actuators by tackling and enhancing the Series-Parallel Elastic Constant Torque Actuation (SPECTA) concept, which has previously been analyzed in simulations. In this work, the efficiency is increased further by decoupling the springs and their driving parts through the use of locking mechanisms, such that the motors are not always loaded and the springs can easily store energy from both input or output. Simulations have been performed to confirm this and they also showed that, in the SPECTA concept, it is always better to use high-speed motors instead of high-torque motors, even with non-efficient gearing. In this paper, the SPECTA concept is also validated experimentally with the use of a newly built test setup. In light of the obtained results, showing an increase in efficiency for almost all working points, it can be stated that SPECTA is a promising new actuation technology that allows for an increase in energy recuperation, efficiency, and autonomy.

This paper presents a study of control strategies for 5-phase permanent magnet synchronous motors (PMSMs) supplied by a five-leg voltage source inverter. Based on the vectorial decomposition of the multi-phase machine, fictitious machines, magnetically decoupled, allow a more adequate control. In this paper, our study focuses on the vector control of a multi-phase machine using a linear proportional-integral-derivative (PID) current regulator in the cases of sinusoidal and trapezoidal back-electromotive force (EMF) waveforms. In order to determine currents’ references, two strategies are adopted. First one aims to minimize copper losses under constant torque, while the second one targets to increase torque for a given copper losses. These techniques are tested under a variable speed control strategy based on a proportional-integral (PI) regulator and experimentally validated.

This paper presents a study of control strategies for 5-phase permanent magnet synchronous motors (PMSMs) supplied by a five-leg voltage source inverter. Based on the vectorial decomposition of the multi-phase machine, fictitious machines, magnetically decoupled, allow a more adequate control. In this paper, our study focuses on the vector control of a multi-phase machine using a linear proportional-integral-derivative (PID) current regulator in the cases of sinusoidal and trapezoidal back-electromotive force (EMF) waveforms. In order to determine currents' references, two strategies are adopted. First one aims to minimize copper losses under constant torque, while the second one targets to increase torque for a given copper losses. These techniques are tested under a variable speed control strategy based on a proportional-integral (PI) regulator and experimentally validated. [ABSTRACT FROM AUTHOR]

The commutation torque ripple in the six‐step square‐wave driving mode of the brushless DC motor affects the motor performance and generates mechanical vibrations and noise when used for industrial applications. The cause of commutation torque ripple is analysed in this study and a non‐linear transient model of the phase current during the commutation interval is developed. According to the transient‐current model, the commutation voltage and the time required to produce a constant torque can be calculated without current sampling; this makes the control system easier to realise in industrial applications, and reduces the need for a high performance controller. Based on the pulse‐with modulated chopping method and quasi‐Z‐source net, the proposed control system can adjust the motor speed using a constant‐voltage power supply and reduce the commutation torque ripple over the entire speed‐adjustable range. A torque transducer is used to measure the dynamic torque ripple in the experiment. The results show that the proposed commutation torque‐ripple reduction strategy can reduce the dynamic torque ripple by about 70% in both simulation and experiment compared with the traditional driving methods. [ABSTRACT FROM AUTHOR]

This paper is devoted to the vibration of rotating flexible spacecraft. The maneuver of the spacecraft is modeled by a constant torque input acting on the hub. For the first time in this paper the equations of motion of flexible spacecraft are derived based on higher order sandwich panel theory (HSAPT). Hamilton's principle is used for driving the governing partial differential equations of motion. The generalized differential quadrature method (GDQ) is utilized to solve the partial differential equations of motion. The effect of different parameters on vibration of rotating flexible spacecraft appendage is investigated. It is also investigated the effect of these parameters on natural frequencies. The result of HSAPT and Euler Bernoulli theory is compared with each other. To show the accuracy the natural frequencies of recent paper are compared with the literature. [ABSTRACT FROM AUTHOR]

The motion about the center of mass of a nearly dynamically spherical rigid body with a cavity filled with a fluid of high viscosity and subjected to constant body-fixed torques is considered. The torque of forces acting on the rigid body by the viscous fluid in the cavity is determined by the technique developed in the works of F.L. Chernousko. Obtained asymptotic and numerical solutions describe the evolution of body motion under the action of small internal and external torques. [ABSTRACT FROM AUTHOR]

Driving system is the power unit that ensures smooth running of the web on web-forming machine. It is mainly composed of driving motor, decelerator, tensioner, deviation rectifying device and various rollers. [ABSTRACT FROM AUTHOR]

In the process of starting, the electro motive force (EMF) of doubly salient electrical motor (DSEM) can be maintained for the constant power control by the flux weakening in theory as the flexible flux. However, the nonlinear magnetic characteristics of DSEM cause EMF to be anomalous square-wave. It is difficult to control the excitation current by the close-loop of EMF as DC motor. In this paper, the excitation current of DSEM is constantly controlled in the process of constant torque. The flux weakening control method with the feed back of the rectified voltage for three terminal phases is given. The switch process from the state of constant torque to constant power is smooth and the maxim output of DSEM is maintained in the process of constant power. Simulation and experimental results confirm the theory of the flux weakening method. [ABSTRACT FROM AUTHOR]

Aiming at the status of shortage of high quality coking coal resources and disordered supply of coal, and less understanding of coal property, taking double furnace design and constant torque as the core technology, the MJS-1 giesler fluidity testing machine with duble furnace was developed, which included many parts, such as transmission and mixing system of coal retort, detecting system of constant torque, convert heating system, automatic counting print and control system, intelligent control system. This testing machine improved the accuracy of coal retort system and optoelectronic S5'stem, and could realize the coal quality analysis detection function. Compared with the existing instrument and import instrument, the results showed the good repeatability of characteristic temperature and the maximum fluidity, the precision met the requirements that the characteristics of temperature average was not more than 8 °C, and average value of the maximum fluidity was not more than 20%, which were completely conform with the industrial standard of MT/T 1015--2006. [ABSTRACT FROM AUTHOR]

Modular multilevel converters are shown to have a great potential in the area of medium-voltage drives. Low-distortion output quantities combined with low average switching frequencies for the semiconductor devices create an ideal combination for very high-efficiency drives. However, the large number of devices and capacitors that have to conduct the fundamental-frequency current require more complex converter control techniques than its two-level counterpart. Special care needs to be taken for starting and operation at low speeds, where the low-frequency current may cause significant unbalance between the submodule capacitor voltages and disturb the output waveforms. In this paper, principles for converter operation with high torque in the whole speed range are investigated. Experimental results from a down-scaled 12-kVA prototype converter running a loaded motor at various speeds between standstill and the rated speed are also provided. [ABSTRACT FROM PUBLISHER]

Abstract: Background: Plantar fascia stretch plays an important role in the treatment of plantar fasciitis. Existing stretch splints mostly provide stretch to Achilles tendon but not to the plantar fascia. The ones that do are inefficient and uncomfortable because of their static nature. In this paper a dynamic stretch splint featured both ankle and metatarsophalangeal joint stretch was designed and developed. This splint should provide continuous stable stretch and be able to monitor the load of stretch during clinical application. To validate the design, twenty volunteers were tested under two stretch conditions, static and dynamic. Forces generated between the splint and the foot across 30-min testing were registered. Level of comfort and joint range-of-motion changes after splint application were evaluated. Statistical results demonstrated significant differences in load of stretch and in level of comfort between the static and dynamic conditions, but not in joint range-of-motion. The findings indicated that the designed splint could provide a continuous load of stretch, eliminate discomfort and increase user compliance comparing to static splint. Its long term effect onto joint angle improvement needs further investigation. Potentially it may be used on subjects with plantar fasciitis, and subjects with foot problems accompanying plantar tissue contracture. [Copyright &y& Elsevier]

The present study examined the viscoelastic creep responses in vivo during repeated constant-torque stretches in human skeletal muscle. Twelve healthy participants completed four consecutive 30-s constant-torque passive stretches of the right plantar flexor muscles. Position and surface electromyographic (EMG) amplitude values were quantified at every 5-s period and the percent change in position was quantified for each 5-s epoch relative to the total increase in ankle joint position for each stretch. In addition, the absolute changes in position were plotted on a logarithmic time scale and fit with a linear regression line to examine both the rate of increase (slope) and the overall increase in position over the entire stretch ( y-intercept). The percent change and slope were similar ( P>0.05) over all four stretches, with the majority of increases in position occurring within the initial 15-20 s of each stretch (84%). Absolute ankle joint position and the y-intercept increased ( P<0.05) following both the first and second stretch but plateaued ( P>0.05) after the third stretch. In addition, EMG amplitude values did not change ( P>0.05) during or between each 30-s stretch. These data indicate that the amount and rate of viscoelastic creep were similar during practical durations of constant-torque stretching despite no change in ankle joint position following three 30-s stretches. [ABSTRACT FROM AUTHOR]

The article discusses research which was conducted to examine musculotendinous stiffness (MTS) and ankle joint range of motion (ROM) in men and women after passive stretching and to determine if there were gender differences in stiffness and range of motion. Researchers evaluated 13 men and 19 women. They found that MTS was higher in men than in women and that stretching increased stretch tolerance in women only. They also found that ROM increased with stretching in women but not men.

The purposes of the present study were to (1) characterize viscoelastic creep in vivo in the human skeletal muscle-tendon unit and (2) to examine the consistency of these responses during a single 30-s stretch. Twelve volunteers (mean +/- SD = 22 +/- 3 years; height = 169 +/- 11 cm; mass = 70 +/- 17 kg) participated in two separate experimental trials. Each trial consisted of a 30-s constant-torque stretch of the plantar flexor muscles. Position (degrees) values were quantified at every 5-s period (0, 5, 10, 15, 20, 25, and 30 s) and the percent change in position was quantified for each 5-s epoch (0-5, 5-10, 10-15, 15-20, 20-25, and 25-30 s) relative to the total increase in the range of motion. In addition, the intraclass correlation coefficient (ICC) and standard errors of the measurement (SEM) were calculated for test-retest reliability. These results indicated that position increased over the entire 30-s stretch (P < 0.05), while the majority of the increases in position (73-85%) occurred during the first 15-20 s. ICC values were >or = 0.994 and SEM values (expressed as percentage of the mean) were

In this study, we examined the minimum number of constant-torque passive stretches necessary to reduce musculotendinous stiffness. Thirteen healthy individuals (mean age 22 years, s = 3; stature 1.67 m, s = 0.1; mass 66 kg, s = 13 kg) volunteered to participate in the investigation and underwent four 30-s constant-torque passive stretches of the plantar flexor muscles. Musculotendinous stiffness was examined from the angle-torque curves generated prior to the passive stretches, at the beginning of each 30-s stretch, and immediately following the four 30-s passive stretches. The results indicated that musculotendinous stiffness of the plantar flexors was reduced following two 30-s constant-torque passive stretches (P < 0.05) compared with the pre- musculotendinous stiffness assessment. Musculotendinous stiffness remained depressed following the third and fourth stretches, but did not decrease further. These findings suggest that two 30-s bouts of constant-torque passive stretching may be necessary to cause a significant decrease in musculotendinous stiffness of the plantar flexor muscles. [ABSTRACT FROM AUTHOR]

The current state of the art in compliant actuation has already good performance, but this is still insufficient to provide a decent autonomy for the next generation of robots. In this paper, a next step is taken to improve the efficiency of actuators by tackling and enhancing the Series-Parallel Elastic Constant Torque Actuation (SPECTA) concept, which has previously been analyzed in simulations. In this work, the efficiency is increased further by decoupling the springs and their driving parts through the use of locking mechanisms, such that the motors are not always loaded and the springs can easily store energy from both input or output. Simulations have been performed to confirm this and they also showed that, in the SPECTA concept, it is always better to use high-speed motors instead of high-torque motors, even with non-efficient gearing. In this paper, the SPECTA concept is also validated experimentally with the use of a newly built test setup. In light of the obtained results, showing an increase in efficiency for almost all working points, it can be stated that SPECTA is a promising new actuation technology that allows for an increase in energy recuperation, efficiency, and autonomy. [ABSTRACT FROM AUTHOR]

This paper lists various factors that define the continuous rating of an adjustable-speed drive (ASD). Operating scenarios are discussed that lead to requirements for temporary overload capability. Specification of ASD overloads is addressed along with methods that can be employed to avoid overloads. Common industrial machines are categorized according to their overload requirements, and application exception examples are provided. General requirements for ASD overload capability, as defined in National Electrical Manufacturers Association (NEMA) and International Electrotechnical Commission (IEC) standards, are reviewed and compared, and recommendations are given for additional user specifications that are appropriate for ac-motor-drive applications. [ABSTRACT FROM AUTHOR]