Equivalent Torque Research Articles

Torque capacity of metal and polycarbonate brackets with and without a metal slot.

The aim of the present study was to investigate slot deformation and the equivalent torque capacity of polycarbonate brackets with and without a metal slot in comparison with those of a metal bracket. For this purpose, the expansion characteristics and, in a further investigation, the labial crown torque of an upper central incisor, were measured in a simulated intra-oral clinical situation, using the orthodontic measuring and simulation system (OMSS). Three types of bracket with a 0.018 inch slot were tested: polycarbonate Brillant without a metal slot, Elegance with a metal slot and the metal bracket, Mini-Mono. For testing purposes the brackets were torqued with 0.016 x 0.022 inch (0.41 x 0.56 mm) and 0.018 x 0.022 inch (0.46 x 0.56 mm) ideal stainless steel archwires. In the activating experiments, significantly higher torque losses and lower torquing moments were registered with both rectangular archwires with the polycarbonate brackets than with the metal bracket. In the simulation tests, significantly higher torquing moments were registered with the metal bracket than with the polycarbonate brackets. The values for the Elegance bracket were between those of the Mini-Mono and Brillant brackets. The OMSS model approximates the clinical situation, with the torque loss being notably higher than in the in vitro activating experiments. This is due to the adjacent teeth giving the archwire additional play. In addition, the torquing process may twist the archwire, resulting in subsidiary forces. On the basis of the present results, all three brackets can be recommended for torquing. However, in view of the high torque losses, the torques programmed in the straightwire technique must be seen as questionable. Data should be provided by the manufacturer on the bending to be expected in polycarbonate brackets, which has to be offset by additional torque, or the bracket torque should be omitted from the technical specifications.

Kinematics and dynamics of a 6 degree-of-freedom fully parallel manipulator with elastic joints

This paper deals with the kinematics and dynamics analysis of a 6 degree-of-freedom RTS fully parallel manipulator with elastic joints. The elastic joints are used to realize highly precise operation. Rotary input is applied to drive six groups of four-bar linkages in this system. Two displacement equations and velocity analysis of the active links and elastic joints are firstly addressed. The angular-velocity of the elastic joints in the motional state are described. In order to investigate the effect of the elastic moment in the dynamic analysis, the elastic bending and the torsional deformation of the elastic joints are presented by only using the vector operation. The standard dynamics formulation including the equivalent torque of the elastic moment with the generalized input is established by virtue of the principle of virtual work and the Lagrange’s method. A study through simulation is provided for a trajectory given in the task-space. Because of employing the kinematic influence coefficients, the dynamic modeling does become simply and the dynamics can readily be formulated in the simulation.

Torque magnetometry: investigation of the intergranular exchange interaction in longitudinal magnetic recording media

We demonstrate a new method for investigation of intergranular exchange coupling in longitudinal magnetic recording media by means of torque magnetometry. The technique we use is based on an analogy with the Δ M method where the analysis involves comparison of reversal processes in the sample with different initial magnetic states. We show that the Δ M curve has an equivalent torque representation Δ τ which can be similarly exploited for studies on the longitudinal media. To validate the method we involve micromagnetic modeling, results of which are compared with the experimental measurements on a model CoCrPtTa media sample.

Simulation of gait and gait initiation associated with body oscillating behavior in the gravity environment on the moon, mars and Phobos.

A double-inverted pendulum model of body oscillations in the frontal plane during stepping [Brenière and Ribreau (1998) Biol Cybern 79: 337-345] proposed an equivalent model for studying the body oscillating behavior induced by step frequency in the form of: (1) a kinetic body parameter, the natural body frequency (NBF), which contains gravity and which is invariable for humans, (2) a parametric function of frequency, whose parameter is the NBF, which explicates the amplitude ratio of center of mass to center of foot pressure oscillation, and (3) a function of frequency which simulates the equivalent torque necessary for the control of the head-arms-trunk segment oscillations. Here, this equivalent model is used to simulate the duration of gait initiation, i.e., the duration necessary to initiate and execute the first step of gait in subgravity, as well as to calculate the step frequencies that would impose the same minimum and maximum amplitudes of the oscillating responses of the body center of mass, whatever the gravity value. In particular, this simulation is tested under the subgravity conditions of the Moon, Mars, and Phobos, where gravity is 1/6, 3/8, and 1/1600 times that on the Earth, respectively. More generally, the simulation allows us to establish and discuss the conditions for gait adaptability that result from the biomechanical constraints particular to each gravity system.

The effect of weightbearing and external loading on anterior cruciate ligament strain

A force balance between the ligaments, articular contact, muscles and body weight maintains knee joint stability. Thus, it is important to study anterior cruciate ligament (ACL) biomechanics, in vivo, under weightbearing conditions. Our objective was to compare the ACL strain response under weightbearing and non-weightbearing conditions and in combination with three externally applied loadings: (1) anterior–posterior shear forces, (2) internal–external torques, and (3) varus–valgus moments. A strain transducer was implanted on the ACL of 11 subjects. All joint loadings were performed with the knee at 20° of flexion. A significant increase in ACL strain was observed as the knee made the transition from non-weightbearing to weightbearing. During anterior shear loading, the strain values produced during weightbearing were greater than those of the non-weightbearing knee (shear loads <40 N). At higher shear loads, the strain values became equal. During axial torsion, an internal torque of 10 Nm strained the ACL when the knee was non-weightbearing while an equivalent external torque did not. Weightbearing significantly increased ACL strain values in comparison to non-weightbearing with the application of external torques and low internal torques (<3 Nm). The strains became equal for higher internal torques. For V–V loading, the ACL was not strained in the non-weightbearing knee. However, weightbearing increased the ACL strain values over the range of moments tested. These data have important clinical ramifications in the development of rehabilitation protocols following ACL reconstruction since weightbearing has been previously thought to provide a protective mechanism to the healing graft.

等価外乱トルクオブザーバの推定誤差をファジィ推論により同定したDCサーボモータのロバスト位置制御

等価外乱トルクオブザーバの推定誤差をファジィ推論により同定したDCサーボモータのロバスト位置制御

ANALYSIS OF A SERIES-DELTA CONNECTED TANDEM INDUCTION MOTOR

Abstract A tandem induction motor comprised of two independently housed stator windings, one housing stationary and the other able to be physically rotated, and a squirrel-cage rotor common to both stators is described. When the motor is fed from a single source, altering the position of the moveable stator changes shaft speed in a similar manner to operating a normal induction motor at variable terminal voltage This paper presents an equivalent circuit model of the tandem induction motor for series-delta connected stator windings. Using the equivalent circuit stator current, power factor, and torque are calculated and then compared to laboratory test results obtained from a 3 kW tandem motor test rig

Modeling of the influence of coil winding pattern on tooth forces in brushless DC motors

The use of neodymium and other rare earth magnets in brushless DC motors increases their torque, but also magnetically induced vibration due to rotating stator tooth force. This paper investigates the influence of the stator coil winding pattern on stator tooth force and torque from three common winding patterns, e.g., center-tapped-wye (CTY), wye (Y) and delta (/spl Delta/), with equivalent torque output. Stator tooth forces and torque in a 6-pole, 9-tooth, 3-phase motor were calculated from the flux density using finite element analysis and the Maxwell stress tensor. Their frequency spectra were analyzed through multi-dimensional spectral analysis. The analyses show that the driving frequencies of tooth forces appear at the integer multiple of rotor speed multiplied by the number of pole. The driving frequencies of forces have larger amplitudes at the leading edge than at the trailing edge of the tooth. At low frequencies, CTY and /spl Delta/ windings produce larger amplitudes at the leading edge and smaller amplitudes at the trailing edge than those of Y winding. Y windings may produce higher torque ripple than the other winding patterns. >

An inherent stability problem in Cartesian compliance and an alternative structure of compliance control

Active compliance is often used in the control of the legs of a walking machine to allow a vehicle to adapt to terrain irregularity. This technique balances force and position errors in Cartesian space to achieve the operation of a damped spring. It is shown that, when decomposed into individual actuator systems, Cartesian compliance may require positive feedback of the equivalent joint torque error to a certain joint. Thus, such a joint can be locally unstable if the environment which the leg system contacts is not passively compliant enough. An inherent stability problem associated with this Cartesian-space compliance control is investigated, and an alternative structure of compliance control that eliminates the inherent source of instability and still permits adaptability to terrain irregularity is introduced. The new algorithm was implemented on the Ohio State University Hexapod vehicle and experimentally verified as giving better performance in system stability than the existing Cartesian compliance algorithm. >

A New Usable Propeller Series

The Combatant Craft Engineering Department began, in the early 1980's, to evaluate a systematic series of propellers representing those available in the commercial market. The primary goal of the program was to generate "open-water" equivalent thrust and torque data, from full-scale trials, to improve propeller selection techniques for small craft and small ships, particularly at high speeds. The first phase of the program investigated three-bladed propellers with systematic variations in pitch ratio as well as propeller blade "cupping." Cupping has been a long-practiced, but ill-defined, art for fine-tuning propeller performance. The second phase, in 1987, expanded the series to include four-bladed propellers. In addition, the propulsion system of the test craft has been changed to achieve higher speeds, and therefore lower cavitation numbers.

A modified approach to earthquake resistant design of torsionally coupled buildings

All major building codes employ empirical procedures to account for modal coupling between the lateral and torsional responses of a structure. These procedures are implemented using expressions defining an equivalent static design torque. The provisions are based largely on the results of parametric investigations of the earthquake response of simple single-storey building models, which are found to be representative of regular multi-storey structures. This paper presents results obtained by the analysis of the time-history earth- quake response of a single storey mono-symmetric building model, leading to the development of an alternative approach for defining the design torque for torsionally coupled buildings. The procedure is based on the concept of effective eccentricity, in which the design lateral displacements of key structural members on the edge of the building are matched to the results of a dynamic analysis. A close approximation to the dynamic responses is derived over the relevant ranges of the important parameters. These parameters include the ratio of torsional to translational natural frequencies, which strongly influences the magnitude of torsional coupling effects in asymmetric buildings.

High-Performance Vector-Controlled AC Motor Drives: Applications and New Technologies

A high-performance ac motor control has been developed by employing the vector control concept. Its versatility has been proven through the six years of experience in applications to pinch roll drives of continuous casting plants, machine tool spindle drives, and other drive systems in industry. Equivalent torque characteristics are achieved with ac motors compared to dc motors without direct detection of the magnetic flux. The effect of rotor temperature on the torque characteristics has been compensated to a satisfactory level in actual industrial use by various means. Servo drives, both synchronous motor and induction motor types, have been introduced. The test results show that the performance of ac servo drives is equivalent or superior to that of the PWM-controlled dc servo drives. Furthermore, an example of the direct-drive servo is described, where an ultra-low speed high-torque motor and an ultra-high resolution position sensor play key roles. In addition, the possibility of a more sophisticated servo drive exploiting modern control theory is suggested.

Rotating Field Magnetometer for Measurement of Anisotropic Magnetic Materials

A new technique is discussed for the measurement of the properties of anisotropic magnetic materials. The basis of the technique is the harmonic analysis of the signal induced in a pick-up loop when the anisotropic material is immersed in a spatially rotating magnetic field. It is shown that the harmonics which are generated are related in a simple way to the Fourier coefficients of the anisotropy energy. High sensitivity is achieved through use of a lock-in detector for the harmonic analysis. Apparatus is described in which the magnetic field rotates at 500 Hz with an amplitude up to 50 Oe. This apparatus can detect a magnetic moment of 10−7 emu and equivalent torque of 10−6 dyne·cm. Illustrative data obtained from a thin Permalloy film (moment of 5×10−3 emu) are given, in which the first three Fourier coefficients of the anisotropy energy are 817, &amp;lt;18, and &amp;lt;1.5 erg/cm3. The absolute accuracy of the first coefficient is about 2%, while the reproducibility of this measurement is better than ½%.

Water-turbine-driven induction generators

The paper outlines the main differences between motor and generator operation and considers the excitation of generators, in particular when provided by system capacitance. Results are given of tests on machines to ascertain the practical effects of uncontrolled excitation and switch-in currents. Information is given about some advantages arising from the absorption of reactive current produced by long transmission lines and the reduction in voltage drop on lines delivering power.The equipment necessary for control, protection, starting and synchronizing is described, as well as technical matters concerned with drying out windings and checking phase rotation.Three typical schemes are described and a list of existing and planned installations is given.An Appendix deals in more detail with the theoretical values of the equivalent circuit, torque and power factor, as well as circle diagrams.

Note on the Minimum-Weight Design of Thin-Walled Cells in Combined Bending and Torsion

In a recent paper the authors suggested that the minimum weight design of thin-walled cells in combined bending and torsion could be tackled by using the well-known concept of equivalent bending moment and torque. It is now felt that a more rational approach would be to base the analysis on the buckling behaviour of the walls of the cell under combined compression and shear and choose the dimensions such that the cell will just resist buckling. The second criterion for design is taken as a limit on the twist as adapted in the case of pure torsion. Two types of sections, rectangular and circular, are discussed in this note.