A Systems Approach to the Torque Control of a Permanent Magnet Brushless Motor

Many approaches to force control have assumed the ability to command torques accurately. Concurrently, much research has been devoted to developing accurate torque actuation schemes. Often, torque sensors have been utilized to close a feedback loop around output torque. In this paper, the torque control of a brushless motor is investigated through: the design, construction, and utilization of a joint torque sensor for feedback control; and the development and implementation of techniques for phase current based feedforeward torque control. It is concluded that simply closing a torque loop is no longer necessarily the best alternative since reasonably accurate current based torque control is achievable.

Design and Control of a Closed-Loop Brushless Torque Actuator

This report explores the design and control issues associated with a brushless actuator capable of achieving extremely high torque accuracy. Models of several different motor - sensor configurations were studied to determine dynamic characteristics. A reaction torque sensor fixed to the motor stator was implemented to decouple the transmission dynamics from the sensor. This resulted in a compact actuator with higher bandwidth and precision than could be obtained with an inline or joint sensor. Testing demonstrated that closed-loop torque accuracy was within 0.1%, and the mechanical bandwidth approached 300 Hz.

The PHD: A Planar, Harmonic Drive Robot for Joint Torque Control

This thesis details the development of a model of a seven degree of freedom manipulator for position control. Then, it goes on to discuss the design and construction of a the PHD, a robot built to serve two purposes: first, to perform research on joint torque control schemes, and second, to determine the important dynamic characteristics of the Harmonic Drive. The PHD, is a planar, three degree of freedom arm with torque sensors integral to each joint. Preliminary testing has shown that a simple linear spring model of the Harmonic Drive's flexibility is suitable in many situations.

Torque in mooring chain. Part 1: Background and theory

Chain in both its forms - common (or stud-less) and stud-link - has many engineering applications. It is widely used as a component in the moorings of offshore floating systems, where its ruggedness and corrosion resistance make it an attractive choice. Chain exhibits some interesting behaviour in that when straight and subject to an axial load it does not twist or generate any torque, but if twisted or loaded when in a twisted condition it behaves in a highly non-linear manner, with the torque dependent upon the level of twist and axial load. Clearly an understanding of the way in which chains may behave and interact with other mooring components (such as wire rope, which also exhibits coupling between axial load and generated torque) when they are in service is essential. However, the sizes of chain that are in use in offshore moorings (typical bar diameters are 75 mm and greater) are too large to allow easy testing. This paper, which is in two parts, aims to address the issues and considerations relevant to torque in mooring chain. The first part introduces a frictionless theory that predicts the resultant torques and 'lift' in the links as non-dimensionalized functions of the angle of twist. Fortran code is presented in an Appendix, which allows the reader to make use of the analysis. The second part of the paper presents results from experimental work on both stud-less (41 mm) and stud-link (20.5 and 56 mm) chains. Torsional data are presented in both 'constant twist' and 'constant load' forms, as well as considering the lift between the links.

Torque in mooring chain. Part 2: Experimental investigation

Chain is a commonly used component in offshore moorings where its ruggedness and corrosion resistance make it an attractive choice. Another attractive property is that a straight chain is inherently torque balanced. Having said this, if a chain is loaded in a twisted condition, or twisted when under load, it exhibits highly non-linear torsional behaviour. The consequences of this behaviour can cause handling difficulties or may compromise the integrity of the mooring system, and care must be taken to avoid problems for both the chain and any components to which it is connected. Even with knowledge of the potential problems, there will always be occasions where, despite the utmost care, twist is unavoidable. Thus it is important for the engineer to be able to determine the effects. A frictionless theory has been developed in Part 1 of the paper that may be used to predict the resultant torques and movement or 'lift' in the links as non-dimensional functions of the angle of twist. The present part of the paper describes a series of experiments undertaken on both studless and stud-link chain to allow comparison of this theoretical model with experimental data. Results are presented for the torsional response and link lift for 'constant twist' and 'constant load' type tests on chains of three different link sizes.

Predictive computed-torque control of a PUMA 560 manipulator robot

This paper describes the integration of constrained predictive control and computed-torque control, and its application on a six degree-of-freedom PUMA 560 manipulator arm. The real-time implementation was based on SIMULINK, with the predictive controller and the computed-torque control law implemented in the C programming language. The constrained predictive controller solved a quadratic programming problem at every sampling interval, which was as short as 10 ms, using a prediction horizon of 150 steps and an 18th order state space model.

Assessing wind profile effects on the global atmospheric torque

The impact of a new approach to the evaluation of surface gravity wave drag (GWD) is assessed. This approach uses linear theory, but incorporates the effects of wind profile shear and curvature, by means of a second-order WKB approximation. While the theory predicts the possibility of either drag enhancement or reduction, depending on the wind profile, results obtained with the ERA-40 reanalysis data clearly indicate the predominance of local drag enhancement. However, the global impact of shear on the atmospheric axial GWD torque comes mostly from regions with predominantly easterly flow, contributing to a slight reduction of the bias found in different studies of the global angular momentum budget. The relative correction due to shear on linear GWD is found not to depend too strongly on the levels chosen for the computation of the low-level wind derivatives.

Sistema eletro-eletrônico para medição direta de torque em dispositivos girantes utilizando extensômetros de resistência elétrica

Neste trabalho propõe-se um sistema para medição de torque em dispositivos girantes, que utiliza extensômetros de resistência elétrica colados nos próprios elementos constituintes do arranjo mecânico sob análise. Um conjunto de circuitos eletrônicos foi especialmente desenvolvido para o sensoreamento das pequenas deformações que ocorrem nos disposotivos girantes. O sistema opera sem contato eletro-mecânico entre a parte estacionária e a parte girante. Para tanto desenvolveu-se também uma metodologia de projeto e construção de transformadores rotativos que são utilizados para transferência da energia que alimenta os circuitos eletrônicos solidários ao elemento mecânico instrumentado. Também foi necessário utilizar um transmissor em freqüência modulada do sinal elétrico proporcional ao torque medido. Uma análise comparativa, dos resultados obtidos entre os sistemas existentes e aqueles alcançados com a técnica proposta neste trabalho, demonstra sua aplicabilidade em diversas situações práticas.

Influência da adaptação funcional nas relações torque-ângulo e torque-velocidade

O objetivo do presente estudo foi comparar as relações torque-ângulo (T-A) e torque-velocidade (T-V) de bailarinas clássicas (n=14) e atletas de voleibol (n=22). O torque máximo (Tmax) da musculatura flexora plantar (FP) do tornozelo foi avaliada durante contrações isométricas voluntárias máximas nos ângulos de -10°, 0°, 10°, 20°, 30°, 40° e 50° de FP, e durante contrações isocinéticas voluntárias máximas nas velocidades angulares de 60°/s, 120°/s, 180°/s, 240°/s, 300°/s, 360°/s e 420°/s. Além do Tmax, o torque produzido nos ângulos articulares de -10° (T-10°), 10° (T10°) e 30° (T30°) também foi avaliado nas mesmas velocidades angulares. A ativação elétrica dos músculos gastrocnêmio medial (GM) e sóleo (SOL) direitos de cada indivíduo foi monitorada com eletrodos de eletromiografia (EMG) de superfície em configuração bipolar. Uma relação linear foi observada entre o Tmax e o aumento dos ângulos de FP nas atletas de voleibol Um deslocamento dessa relação em direção a maiores ângulos de FP (menores comprimentos musculares) ocorreu no grupo das bailarinas, com o aparecimento de um platô em menores ângulos de FP (maiores comprimentos musculares). Durante as contrações isocinéticas, uma relação hiperbólica foi observada entre o Tmax, T-10° e T10° com o aumento da velocidade angular nos dois grupos. Entretanto, em T30° as atletas de voleibol produziram valores superiores de torque nas velocidades angulares mais elevadas. Os valores root mean square (RMS) dos músculos GM e SOL foram mais elevados nas bailarinas que nas atletas de voleibol, tanto nas contrações isométricas quanto nas isocinéticas. Uma diminuição na ativação do GM e do SOL ocorreu com a diminuição da FP nas atletas de voleibol, enquanto os valores RMS se mantiveram estáveis para as bailarinas ao longo de todos os ângulos testados. Os resultados apresentados nesse estudo suportam a hipótese de que a atividade física sistemática provoca alteração nas propriedades intrínsecas musculares e ativação muscular, modificando assim, as relações T-A e T-V.

Controle de força e torque isométrico em crianças com e sem desordem coordenativa desenvolvimental

Esta tese teve como objetivos investigar: (1) as mudanças relacionadas à idade no controle de força e torque isométrico em crianças de diferentes idades em três tarefas manipulativas distintas, e (2) as diferenças no controle de força e torque isométrico, assim como nas respostas neuromusculares, entre crianças com e sem DCD de idade relacionadas em três tarefas manipulativas distintas. Neste sentido, foi realizado um ensaio teórico sobre a criança com Desordem Coordenativa Desenvolvimental (DCD), além de dois estudos experimentais que têm em comum a análise da estrutura da resposta do sistema motor em relação à performance das crianças com e sem DCD, em três tarefas manipulativas distintas de controle de força e torque isométrico, contínuo e constante. No primeiro estudo, foram investigadas as mudanças desenvolvimentais no controle motor usando um delineamento transversal de pesquisa com crianças de 7, 9 e 11 anos de idade, as quais foram incentivadas a manter o controle de força e torque durante vinte segundos nas tarefas de pressão digital, preensão digital em pinça e torque em preensão digital. Os resultados demonstraram que a performance melhorou com o avanço da idade, devido à capacidade do sistema sensório-motor apresentar uma resposta mais irregular e com um perfil de freqüências mais distribuídas. No segundo estudo, o controle de força e torque entre crianças com e sem DCD, com nove anos de idade, foram investigadas. Os participantes realizaram as mesmas tarefas do estudo desenvolvimental e, além disso, respostas neuromusculares foram mapeadas Os resultados não revelaram uma variabilidade maior e irregularidade menor no grupo com DCD nas tarefas de pressão digital e preensão digital em pinça. No entanto, na tarefa de controle de torque em preensão digital, foi identificada uma maior variabilidade e menor irregularidade na resposta motora do grupo com DCD. Os resultados não revelaram uma variabilidade maior e irregularidade menor no grupo com DCD nas tarefas de pressão digital e preensão digital em pinça. No entanto, na tarefa de controle de torque em preensão digital, foi identificada uma maior variabilidade e menor irregularidade na resposta motora do grupo com DCD. Os resultados da análise das respostas neuromusculares sugerem o uso de estratégias distintas entre os grupos, todavia, tais achados não foram conclusivos.

Desenvolvimento e avaliação de padrão de torque para calibração de torquímetros em três faixas de medição

The continuous development of instruments and equipment used as tools or torque measurement in the industry is demanding more accurate techniques in the use of this kind instrumentation, including development of metrological characteristics in torque measurement. The same happens with the needs in calibration services. There is a diversity of methods of hand torque tools in the market with different measuring range but without complaining with technical standards in terms of requirements of quality and reliability. However, actually there is no choice of a torque measuring standard that fulfils, with low cost, the needs for the calibration of hand torque tools in a large number of ranges. The objective of this thesis is to show the development and evaluation of a torque measuring standard device with a conception to allow the calibration of hand torque tools with three levels of torque with an single instrument, promoting reduction of costs and time in the calibration, also offering reliability for the evaluation of torque measuring instrument. To attend the demand in the calibration of hand torque tools it is necessary that the calibration laboratories have a big collection of torque measuring standards, to fulfills the needs of the costumer, what is very costly. The development of this type of torque measuring standard revealed a viable technique and economically making possible the calibration of hand torque tools in different nominal ranges through a single measurement system versatile, efficient and of easy operation

Correlação entre torque, equlíbrio e função do joelho após reconstrução do LCA

Background: Several studies emphasize the importance of assessing the knee function after anterior cruciate ligament (ACL) reconstruction. The influence of several variables on the function of these patients has been analyzed, but there is no consensus in the science literature. Purpose: To evaluate the correlation between the torque and balance on the knee function after ACL reconstruction. Methods: 23 males patients with ACL reconstruction were tested. The procedures of the study included analysis of concentric peak torque at 60o/s and 180o/s of quadriceps femoris and hamstring muscle with a isokinetic dynamometer. The balance in single-limb stance was measured with stabilometry. The functional performance were performed by two hop tests. To estimate the subjective function of the patients was applied Lysholm Knee Scoring Scale and a Global Rating scale. Results: The analysis of data showed a moderate positive correlation between knee extensor torque and functional performance tests (r= 0,48; p=0,02). A moderate negative correlation was found between the two variables of the stabilometry center of pressure and average speed of centre of pressure and the Global Rating scale (r = -0.4, p = 0,04 and r = -0,49, p = 0 ,02, respectively). No correlation was found between peak torque and balance in single-limb stance. Conclusion: The results of the present study suggest that knee extensor strength and postural balance have some influence on knee function in patients after ACL reconstruction

Efeito de três tecnicas de alongamento muscular sobre o torque e atividade eletromiográfica

PURPOSE: To examine the acute effects caused by three techniques for stretching the hamstrings muscle on the active concentric peak torque (PT), passive PT and electromyographic activity (EMG). METHODS: Sixty volunteers (mean ± SD age, 22.6 ± 3 years), height 1.64 ± 0.07m and body weight of 58 ± 8.6kg, were randomly allocated into 4 groups of 15 subjects: Control Group (CG) - 5 minutes at rest, Static Stretching Group (SG) - 2 x 30s; Hold-Relax Group (HRG) - 3 x 6s of isometric contraction of hamstrings interspersed by 10s of hamstrings stretching and agonist Hold-Relax Group (AHRG) - 3 x 6s of isometric contraction of the quadriceps interspersed by 10s of hamstrings stretching. Evaluation has been conducted preand post-intervention, which verified the active concentric PT, passive PT EMG activity of IT. The statistical inference was performed by testing intra and inter, significance level at 5%. RESULTS: After intervention, there was a reduction in passive PT on CG, accompanied by a reduction of EMG activity, and an increase in passive PT on SG and AHRG. There was no change in the active concentric PT, or change in EMG activity. CG showed an increase in angle of the PT active, while the other groups showed no change. CONCLUSION: The results suggest that the shortterm stretching: 1) causes acute increase in passive torque, since the muscle does not perform sub-maximal contraction, 2) does not change in electromyographic activity and active torque, ind ependent of the technique