Maximum Average Torque Research Articles

Outcomes following quadriceps tendon ruptures

Complete rupture of the quadriceps femoris tendon is a well-described injury. There is a scarcity of literature relating to the outcome of patients with this injury after surgery. We undertook a retrospective analysis of patients who had surgical repair of their ruptured quadriceps tendon at our institution over a seven year period-totalling 27 patients. Males were more commonly affected with a M:F ratio of 8:1. The peak incidence was in the sixth decade of life. The non-dominant limb was twice as likely to be affected. Assessment consisted of completion of a functional knee questionnaire, clinical examination and isokinetic testing on a Biodex dynanometer. Symptomatic outcome following surgical repair was excellent with a mean symptom score generated of 22.7 out of a maximum of 25. 18/19 patients returned to their premorbid level of activity on average 18.1 weeks following injury. There was no difference in quadriceps girth comparing affected and unaffected limbs. Less than 5° deficit in range of motion existed between affected and unaffected limbs. Approximately two-thirds of patients were the same or better when comparing peak torque/body weight, average power, maximum average peak torque and total work/body weight in affected and unaffected limbs.

Technique for finding the optimum geometry of electrostatic micromotors

This paper presents a computer-based method for finding the optimum geometry of very small electrostatic motors based on the variable capacitance principle. Not only is the geometry taken into account, but different excitation schemes are studied, in order to find the maximum average output torque and/or the minimum vibration component in the output torque. Different combinations of stator and rotor poles are treated. The most important part of this optimization is automation of the procedure. For the actual calculation of the electrostatic field distribution, the finite-element method is used. The mesh generation for the machine as a function of the rotor position and the design parameters is automated. The extraction of the torque and capacitance values is done in batch procedure, constructed around a commercial finite-element CAD package. This automation makes the system an optimization tool of an otherwise very tedious technique.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Reliability of dynamic and isometric testing of shoulder external and internal rotators.

Advances in isokinetic technology allow the physical therapist to assess concentric, eccentric, and isometric muscle performance at the shoulder in various positions. Research is limited, however, on the reliability of isokinetic measurements. The purposes of this study were: 1) to determine the test-retest reliability of concentric, eccentric, and isometric muscle performance measurements of shoulder external and internal rotation in the scapular plane test position and 2) to compare this reliability between the involved and uninvolved limb of subjects with a history of unilateral shoulder pathology. Fourteen males and 10 females (17-58 years) were tested on two occasions at 1-week intervals with the Biodex isokinetic dynamometer. Peak torque, total work, and average power were recorded for concentric tests at angular velocities of 60 and 120 degrees/sec and for eccentric tests at 60 degrees/sec. Maximum average isometric torque was recorded in two positions. Means, standard deviations, and mean differences between sessions with 95% confidence intervals were calculated. Intraclass correlation coefficients (ICCs) were used to determine test-retest reliability. Isometric tests were generally most reliable (ICC = .81-.93), followed by concentric (ICC = .60-.95) and eccentric tests (ICC = .44-.92). Isokinetic and isometric reliability were usually higher for involved than uninvolved shoulders. The implication of these findings is that there appears to be greater variability with eccentric than concentric or isometric testing of shoulder rotation. Factors that possibly contributed to variability are discussed. Clinicians should recognize potential sources of testing error when obtaining isokinetic measurements for use in clinical decision-making. Further refinement of isokinetic testing protocols at the shoulder is recommended.

Minor-Closed-Loop Control of a Single Stack Variable Reluctance Stepping Motor for High Speed Positionning

This paper presents a viable minor-closed-loop control system for a typical stepping motor. Maximization of the stepping motor's average output torque is achieved by control of the switching angle in a high resolution discrete manner. This approximates an experimentally determined optimum relationship between switching angle and maximum average output torque. The control function is identical during acceleration and deceleration and the control scheme is therefore suited to high speed positioning applications. A simple form of constant speed control is provided without resorting to the use of switching angle manipulation. The switching angle relationship is stored in read-only memories as a look-up table and is keyed to the motor speed through a feedback pulse period measurement. The switching angle is optimized in real time in response to overall system requirements. A load-independent control scheme is thus obtained. By storing the switching angle data in reprogrammable read-only memories, stepping motors of similar design philosophy having different performance characteristics can be accommodated by simply reprogramming these memories. One control system can thus be used for a large number of stepping motors.

Electron trapping noise in SOS MOS field-effect transistors operated in the linear region : S. T. Hsu. RCA Rev.38, 226 (June 1977)

This paper presents a viable minor-closed-loop control system for a typical stepping motor. Maximization of the stepping motor's average output torque is achieved by control of the switching angle in a high resolution discrete manner. This approximates an experimentally determined optimum relationship between switching angle and maximum average output torque. The control function is identical during acceleration and deceleration and the control scheme is therefore suited to high speed positioning applications. A simple form of constant speed control is provided without resorting to the use of switching angle manipulation.The switching angle relationship is stored in read-only memories as a look-up table and is keyed to the motor speed through a feedback pulse period measurement. The switching angle is optimized in real time in response to overall system requirements. A load-independent control scheme is thus obtained.By storing the switching angle data in reprogrammable read-only memories, stepping motors of similar design philosophy having different performance characteristics can be accommodated by simply reprogramming these memories. One control system can thus be used for a large number of stepping motors.

Ionizing radiation effects on NMOS microprocessors : David K. Myers. Proc. Electron. Components Conf., Arlington, Va. (May 16–18 1977). p. 521

This paper presents a viable minor-closed-loop control system for a typical stepping motor. Maximization of the stepping motor's average output torque is achieved by control of the switching angle in a high resolution discrete manner. This approximates an experimentally determined optimum relationship between switching angle and maximum average output torque. The control function is identical during acceleration and deceleration and the control scheme is therefore suited to high speed positioning applications. A simple form of constant speed control is provided without resorting to the use of switching angle manipulation.The switching angle relationship is stored in read-only memories as a look-up table and is keyed to the motor speed through a feedback pulse period measurement. The switching angle is optimized in real time in response to overall system requirements. A load-independent control scheme is thus obtained.By storing the switching angle data in reprogrammable read-only memories, stepping motors of similar design philosophy having different performance characteristics can be accommodated by simply reprogramming these memories. One control system can thus be used for a large number of stepping motors.

Liquid crystal technique for field detection in microwave integrated circuitry : F. Giannini, P. Maltese and R. Sorrentino. Alta Frequenza p. 170 (April 1977)

This paper presents a viable minor-closed-loop control system for a typical stepping motor. Maximization of the stepping motor's average output torque is achieved by control of the switching angle in a high resolution discrete manner. This approximates an experimentally determined optimum relationship between switching angle and maximum average output torque. The control function is identical during acceleration and deceleration and the control scheme is therefore suited to high speed positioning applications. A simple form of constant speed control is provided without resorting to the use of switching angle manipulation.The switching angle relationship is stored in read-only memories as a look-up table and is keyed to the motor speed through a feedback pulse period measurement. The switching angle is optimized in real time in response to overall system requirements. A load-independent control scheme is thus obtained.By storing the switching angle data in reprogrammable read-only memories, stepping motors of similar design philosophy having different performance characteristics can be accommodated by simply reprogramming these memories. One control system can thus be used for a large number of stepping motors.

Biomechanical analysis of knee flexion and extension

For the knee, mathematical analyses for the sagittal plane were performed on data obtained from roentgenograms and a load cell incorporated in a specially constructed force table. Normal knees from 26 subjects were examined. Some of the results were: (1) the axis of rotation for the knee displaced 3·2 cm through a 90° range and is located at the level of the lateral femoral epicondyle, (2) the moment arm is greater for knee extensors than the flexors, (3) the maximum average torque values of nearly 1200 kg-cm result from eccentric (lengthening) and isometric (static) muscle contractions while the isometric (static) flexor contraction near complete extension produced a maximum average torque of 636 kg-cm. and (4) during muscular efforts against external load the contact forces at the patello-femoral and tibialfemoral joints varied from 0·38 to 3·40 times body weight.

Asynchronous reluctance motor using ferroresonance

This paper shows how asynchronous operation of a reluctance motor may be obtained by taking advantage of one of the properties of a series LCRcircuit, in which the inductance is a function of current. Parametric variation of the machine inductance is accomplished by variation of the rotor iron-circuit reluctance, instead of the more conventional change in air gap. These changes in reluctance are utilised in such a way that the circuit alternates between resonant and nonresonant states, with consequent variation in current amplitude. When the resonant state coincides with a positive rate of change of air-gap inductance with rotor position, and hence the nonresonant state with a negative rate of change, the net average torque developed is positive. The speed/torque characteristics are dependent upon applied voltage, series resistance and series capacitance, as well as the rotor geometry. Thus a simple variable-speed a.c. motor having no windings on the rotor is possible. Maximum average torque obtainable from such a machine at very low speeds is of the same order as that obtainable from the same machine running synchronously. A mathematical model is proposed for the machine, from which expressions for torque in terms of the machine and circuit parameters can be obtained. These lead to an equivalent circuit and the differential equations of motion, which are nonlinear with time-dependent coefficients, so requiring solution by numerical or analogue methods. Assumptions made when setting up the model and in subsequent simplifications have been tested experimentally and the results presented. These suggest that the proposed model will provide at least a qualitative indication of dynamic behaviour. All discussion and analysis applies equally well to linear motion provided the appropriate change is made in the `rotor' geometry. The problems of self starting and line-current fluctuation are briefly discussed, and possible solutions are suggested.