Made available in DSpace on 2016-12-12T17:32:55Z (GMT). No. of bitstreams: 1 MARCELO ANDERSON BRACHT.pdf: 528517 bytes, checksum: fda430f0ee52869b14f2380311059025 (MD5) Previous issue date: 2013-05-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neck pain is a highly prevalent disease that leads to disability; individuals with neck pain experience changes in pressure pain threshold, latency activation of the neck muscles and in grip force control. However, there are few studies investigating the effectiveness of physiotherapy interventions on these changes, for example, cervical manipulation. The aim of this study was to investigate the effects of cervical manipulation on pain and upper limb motor control in subjects with neck pain. Thirty subjects with neck pain were instructed to grasp an object that was placed on a table, pre and post intervention, which consisted of or cervical manipulation (n = 15) or sham manipulation (n = 15). The data of the pain threshold, grip force and electrical activity of the upper limb muscles were collected during the task. A blinded evaluator assessed the variables of grip force control and latency of muscles in relation to the object lifting. The analysis of covariance (ANCOVA) identified a statistically significant difference (F = 7.46, P = 0.01) between groups for pressure pain threshold in the upper trapezius region, no significant differences were found for the other variables. The results of this study showed that cervical manipulation causes immediate local hypoalgesia, without however, change the motor control of the upper limb muscles. These results encourage future studies to investigate the cervical manipulation effects on motor control, in the medium and long term, using this and other dynamic tasks. / A cervicalgia é uma doença de alta prevalência que leva a incapacidade funcional; indivíduos com cervicalgia apresentam alterações no limiar de dor à pressão, na latência de ativação dos músculos cervicais e no controle da força de preensão manual. No entanto, são escassos os estudos que investigam a efetividade de intervenções fisioterapêuticas sobre essas alterações, por exemplo, a manipulação cervical. O objetivo do presente estudo foi investigar os efeitos da manipulação cervical sobre a dor e o controle motor do membro superior em indivíduos com cervicalgia. Trinta sujeitos com cervicalgia foram instruídos a pegar e levantar um objeto que foi posicionado sobre uma mesa, pré e pós intervenção, que consistiu de ou manipulação cervical (n=15) ou manipulação placebo (n=15). Os dados do limiar de dor, da força de preensão e da atividade elétrica dos músculos do membro superior foram coletados durante a tarefa. Um avaliador cego analisou as variáveis de controle de força de preensão e a latência dos músculos em relação ao levantamento do objeto. Através da análise de covariância (ANCOVA) identificou-se uma diferença estatisticamente significativa (F= 7.46, p=0.01) entre os grupos para o limiar de dor à pressão na região do trapézio superior; não foram encontradas diferenças significativas para as demais variáveis estudadas. Os resultados desse estudo mostraram que a manipulação cervical provoca hipoalgesia imediata local, sem no entanto, alterar o controle motor dos músculos do membro superior. Esses resultados incentivam futuros estudos a investigar os efeitos da manipulação cervical a médio e longo prazo sobre o controle motor, mediante essa e outras tarefas dinâmicas.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objective of this work is to apply a heuristic method to optimize the choice of parameters of unbalanced input voltages of a linear induction motor at low speeds.The mathematical model developed for the linear induction motor considers his linor blocked, aiming applications at low speeds. Applying a genetic algorithm program the magnitude of unbalance of the input voltage of the linear motor can be determine.The experimental results are compared satisfactorily with practical tests conducted with a prototype of the linear machine. / O objetivo deste trabalho é aplicar um método heurístico para otimizar a escolha dos parâmetros de desbalanceamento das tensões de entrada de um motor de indução linear em baixas velocidades. O modelo matemático desenvolvido para o motor de indução linear considera o seu linor bloqueado, visando aplicações em baixas velocidades. Através da aplicação de um programa de algoritmo genético é possível determinar a magnitude dos desbalanceamentos das tensões de entrada do motor linear. Os resultados experimentais obtidos são confrontados de forma satisfatória com os testes práticos realizados com um protótipo da máquina linear. / Mestre em Ciências

De nos jours, les systèmes intègrent de plus en plus de fonctionnalités dans des volumes de plus en plus petits grâce aux microcomposants intégrés. L'assemblage de ces microcomposants nécessite des systèmes de manipulation précis et reproductibles. Un nombre considérable de recherches ont été menées afin de mettre au point des actionneurs et des microrobots capables d'effectuer des tâches de positionnement ou de manipulation avec des précisions microniques voire submicroniques. Les technologies piézoélectriques jouent un rôle fondamental dans les applications de positionnement à résolution nanométrique ou même inférieure. Ces matériaux permettent la conception et le développement de systèmes de positionnement avec résolution et bande passante élevées. Cependant, des effets non linéaires tels que l'hystérésis et la dérive lente affectent la précision de la position des systèmes à base piézoélectrique s'ils ne sont pas contrôlés. Souvent, des capteurs de position sont montés sur ces systèmes pour permettre un contrôle en boucle fermée et l'élimination des effets d'hystérésis et de dérive lente. Néanmoins, l'intégration de capteurs permettant un asservissement robuste et de qualité pose des problèmes spécifiques aux microrobots. Cela est particulièrement vrai lorsque le nombre de degrés de liberté augmente. En effet, les capteurs de position qui jouissent d'une bonne résolution et précision sont généralement très volumineux et coûteux. Les solutions alternatives à l’intégration de capteurs de position externes peuvent être regroupées en deux catégories: soit par contrôle en boucle ouverte, également appelé schémas de contrôle prédictifs, soit par des techniques basées sur le contrôle par auto-détection (Self-Sensing Actuation - SSA), c’est-à-dire un contrôle en boucle fermée utilisant l'actionneur piézoélectrique comme son propre capteur.Dans cette thèse, l'objectif est de concevoir et de contrôler un système de positionnement basé sur la technologie piézoélectrique avec une méthode de mesure intégrée par SSA et ayant plusieurs degrés de liberté. À cette fin, les deux classes de SSA, à savoir le SSA basé sur l’effet direct piézoélectrique et le SSA basé sur la modification des propriétés électriques de l'actionneur piézoélectrique (PEA), sont étudiées en profondeur afin de déterminer celle qui convient le mieux au contrôle de la force et de la position dans les actionneurs piézoélectriques caractérisés par le fluage et non-linéarités d'hystérésis et consacrés à des opérations précises. De plus, cette étude présente un modèle constitutif et une technique d’identification de paramètres améliorés, qui prend en compte l’effet de couplage électromécanique et les non linéarités sur les propriétés du matériau piézoélectrique (constantes élastiques et diélectriques).Une nouvelle technique d'évaluation en temps réel des propriétés électriques du PEA est développée. Cette évaluation est basée sur la mesure de l’amplitude du courant de détection résultant de l’application d’une tension d’entrée haute fréquence de faible amplitude superposée à la tension d’entrée de commande qui actionne le PEA. Ensuite, un estimateur qui utilise le courant de détection pour estimer la position du PEA est conçu. Enfin, une plate-forme microrobotique pour le positionnement planaire à haute résolution avec la mesure intégrée par SSA développée est présentée. / Currently, systems integrate more and more functionalities into smaller volumes thanks to embedded micro-components. The assembly of those components requires precise and repeatable systems of manipulation. Substantial amounts of research have been carried out for developing actuators and microrobots to perform positioning or manipulation with micron- or even submicron accuracies. Piezoelectric technologies play a fundamental role in positioning applications with nanoscale or even lower resolution. These materials make possible the design and development of positioning systems with high resolution and bandwidth. However, nonlinear effects such as hysteresis and creep affect the position accuracy of piezoelectric-based systems if not controlled. Often, position sensors are mounted to these systems to permit a feedback control and the elimination of the hysteresis and creep effects. Nonetheless, the integration of sensors to enable quality and robust servo control poses specific problems for microrobots. This is especially true when the number of degrees of freedom (DOF) increases. Precision position sensors are usually very bulky and expensive. Alternative solutions to the integration of external position sensors can be grouped into two categories: either by open-loop control, also called feedforward control schemes or by Self-Sensing Actuation (SSA) control-based techniques, that is, a feedback control that uses the piezoelectric actuator as its own sensor.In this thesis, the objective is to design and control a piezoelectric-based positioning system with an embedded measurement by SSA method and having several degrees of freedom. To this end, the two classes of SSA, namely SSA based on the piezoelectric direct effect and the SSA based on the change of electrical properties of the piezoelectric actuator (PEAs), are studied in depth to determine the more adequate for force and position control in piezoelectric actuators typified by creep and hysteresis nonlinearities and devoted to precise operations. Additionally, from this study, an improved constitutive model and parameter identification technique are presented which includes the electromechanical coupling effect on the piezoelectric material properties (elastic and dielectric constants).A novel technique for real-time evaluation of the PEA's electrical properties is developed. This evaluation is based on the measurement of the amplitude of the detection current that results from the application of high-frequency low amplitude input voltage that is superimposed to the control input voltage which actuates the PEA. Then an estimator that uses the detection current to estimate the PEA's position is designed. Finally, a microrobotics platform for planar positioning with high resolution and the developed embedded measurement by SSA is presented.

No description available.

In some industrial fields, such as aerospace, electro-hydrostatic actuators (EHAs) are increasingly used to replace conventional standard hydraulic actuators due to their better energy performance. Moreover, implementing different type or technology of actuators in redundant actuation systems working on the same moving part introduced some new challenges. This paper presents a force-tracking controller for an asymmetric electro-hydrostatic actuator that is submitted to an external motion generated by an external source. In this case, the rod displacement is considered as an external disturbance for the hydraulic cylinder, but it is assumed that this disturbance can be easily measured using sensors. The theoretical motivation of this work is discussed along and a variable gain state feedback control based on Linear Parameter Varying control (LPV) theory is proposed to achieve stability, disturbance rejection and tracking performance. The Linear Matrix Inequalities (LMI) framework is used to determine a control law including an augmented state feedback with an integral action that reduces trajectory-tracking errors. Simulation results of the control law are finally given to verify the global performance of this control design.

Manufacturing industry works on Overall Equipment Effectiveness (OEE) to increase the yield and speed of machining. A good knowledge of the machine properties is important to increase the speed while still maintaining stable cutting with low tool usage.To make models of the machine is therefore important and in machining a common way to extract the dynamic properties is frequency response measurement. One way is to use an impact hammer to excite the machine tool and measure the response. The problem is that a hammer can only be used on a non running machine. At Manufacturing and Metrology Systems division at KTH (MMS) a test method for contactless excitation has been developed that uses electromagnets to excite the machine tool. By using contactless testing it can be used on rotating machine tools without real cutting in materials. In this thesis a new test system for the contact less testing method has been designed and constructed to test if it is possible to do test on a bigger variety of rotating cutting machine tools. The results for the prototype is presented and evaluated. / Dagens tillverkningsindustri arbetar för att utrsutningens totala effiktivitet ska höjas genomatt öka hastigheten och minska material- och verktygsanvändningen vid bearbetningen utan att minska kvalitén på slutprodukten. För att öka hastigheten krävs en god kännedom om maskinens egenskaper för att maskinen ska arbeta under stabila förhållanden där också verktygets slitage minskas. Att ta fram modeller över maskinen är därför viktigt och inom skärande bearbetning är frekvensresponsmätning ett sätt att få ut de dynamiska egenskaperna av det skärandeverktyget. En vanlig testmetod är att med en hammare exitera verktyget och mäta responsen. Problemet är dock att hammaren bara kan mäta vid stillastående maskin. Vid MMS har en testmetod för kontaktlös exitering tagits fram där elektromagneter användsför exiteringen. På så sätt kan testet utföras på roterande verktyg utan att man behöver förbruka material. I detta arbete har ett nytt testsystem för denna testmetod designats och konstruerats för att testa om det är möjligt med testning på flera storlekar på maskiner för skärandebearbetning. Resultaten för prototypen presenteras och utvärderas.

Die prozessaktuelle Messung von Kräften und Momenten zwischen Werkzeug und Werkstück ist zunehmend Voraussetzung für viele fertigungstechnische Anwendungen. Neben der Verwendung der Daten zur Prozessdiagnose und -überwachung sowie für Qualitätssicherung und -nachweis, werden durch geregelte bzw. adaptive Prozessführung bestimmte Prozesse oder Qualitäten überhaupt erst möglich oder wirtschaftlich. Mit dem erweiterten Bewegungsvermögen moderner Fertigungseinrichtungen wächst dabei auch der Bedarf zur Erfassung räumlicher Kräfte und Momente in bis zu 6 Freiheitsgraden. Großes Potenzial besteht in der Integration mehrerer einachsiger Kraftsensoren direkt in die Maschinenstruktur und der intelligenten Verarbeitung der Messsignale zu räumlichen Kräften und Momenten an der Wirkstelle. Insbesondere für parallele Stabstrukturen und Parallelkinematiken -- und für die Messung mit 6 Freiheitsgraden speziell für Hexapodstrukturen und Hexapoden -- ist der Ansatz aufgrund der nahezu reibungsfreien Messung vielversprechend. Gleichzeitig wirken jedoch prozess- und strukturbedingte Einflüsse auf die Kraftsensoren, die in Abhängigkeit der Sensorposition durch ein Messmodell kompensiert werden müssen. Für dynamische Messungen während der Maschinenbewegung müssen diese Messmodelle zwingend in Echtzeit im Steuerungskern berechnet werden und weiterhin durch ein Verfahren zur Parameteridentifikation schnell und einfach an der betriebsbereiten Maschine aktualisiert werden können. Diese Arbeit erforscht Möglichkeiten und Grenzen integrierter Kraftsensorik in starren Hexapodstrukturen und Hexapodkinematiken zur räumliche Prozesskraftmessung und -regelung an der Wirkstelle sowie die dazu notwendigen Messmodelle und Verfahren zur Parameteridentifikation. Für den Lösungsansatz kommen ausschließlich kostengünstige einachsige Standard-Kraftsensoren zum Einsatz, und die Validierung erfolgt auf Versuchsträgern mit kommerzieller Werkzeugmaschinensteuerung. Es werden systematisch mögliche Konfigurationen und Einbaupositionen identifiziert, die zugehörigen Messmodelle aufgestellt und Verfahren zur Auslegung und Berechnung aussagekräftiger Kenngrößen entwickelt. Anhand definierter Bewertungskriterien werden die Varianten in umfangreichen experimentellen Untersuchungen untereinander verglichen sowie zu den Standardlösungen der 6-Achs-Kraftmessplattform und der Kraftschätzung aus Antriebsströmen eingeordnet. Einen Schwerpunkt bildet die Messung während der Maschinenbewegung, bei der synchron zur Messung und abhängig von der Sensorplatzierung maschinen- und prozessbedingte Einflüsse online kompensiert werden müssen. Auf dieser Basis erfolgt anschließend die Entwicklung von Identifikationsverfahren zur schnellen und einfachen Parametrierung der Messmodelle an der betriebsbereiten Maschine durch automatisierbare Messzyklen. Schließlich werden mit den entwickelten Messsystemvarianten verschiedene Formen der Kraftregelung umgesetzt und die Ansätze so anwendungsnah validiert. Im Ergebnis liegen Methoden und Verfahren zur Aufstellung der Messmodelle, zur Auslegung der Kraftmesssysteme sowie zur Berechnung aussagekräftiger Kenngrößen vor. Zusammen mit der Validierung anhand verschiedener Anwendungsfälle wird ein Beitrag geleistet zur Qualifizierung der Unsicherheiten der räumlichen Kraftmessung mit integrierten Sensoren sowie der Auswirkung der Sensorintegration auf die Maschineneigenschaften. Die zwei entwickelten Verfahren zur Parameteridentifikation erlauben anhand der Kraftsignale aus quasi-statischen und dynamischen Eigenbewegungen der Maschine die schnelle Rekalibrierung der Messmodelle ohne Vorwissen oder Versuchsaufbauten in Bearbeitungspausen. Schließlich zeigen die zwei umgesetzten Varianten der räumlichen Kraftregelung die Eignung der strukturintegrierten Kraftmessung sowohl für das kraftgeregelte Teachen als auch für die Kontaktkraftregelung. / Today, in-process force measurement is required by many manufacturing applications. Beside process monitoring and diagnosis as well as quality assurance and validation, force controlled or adapted process management allows producing higher qualities or even enables new processes. With the extended movability of modern machine tools, such as five-axis kinematics or hexapods, the measurement of spatial forces and moments in up to 6 degrees of freedom is requested in particular. A new promising approach bases on the integration of multiple single-axis force sensors into the machine structure and the smart control-integrated signal transformation to forces and moments at the tool centre point. Especially for bar structures and kinematics, and for a measurement in 6 degrees of freedom for hexapod structures and kinematics, the approach is particularly suitable, as no friction is involved. At the same time, process and dynamic influences affect the force measurements and must be included into a real-time capable measurement model within the control kernel. As the model parameters can change during machine usage, a fast and simple calibration procedure is requested. This contribution explores capabilities and limits of integrated force sensors in rigid hexapod structures and hexapod kinematics for the sake of spatial process force measurement and control at the tool centre point as well as the required measurement models and parameter identification procedures. For practical relevant results, only commercial cost-efficient single-axis standard force sensors are used for this approach, and implementation as well as validation are performed on commercial machine tool controls. At first, possible configurations and sensor placements are evaluated systematically, measurement models are implemented, and methods for framework design as well as the calculation of meaningful criteria are investigated. Next, multiple variants of the new sensor systems are evaluated and classified in extensive experimental studies with regard to the state of the art, which is represented by force/torque sensors at the end-effector and force measurement from drive currents. A focal point is the measurement during machine movement, which requires a synchronous measurement of force and drive values to compensate dynamic influences in real-time. On that basis, different parameter identification procedures are investigated to update the measurement models with fast and simple procedures in an operational machine state by automatable measurement cycles. Finally, multiple variants of force control are implemented that use and validate the developed integrated force measuring systems. In conclusion, methods and procedures to design structure-integrated force sensor systems, to implement the required measurement models, and to calculate meaningful characteristics are available. By the evaluation and validation of the systems regarding to multiple use cases and with respect to the state of the art, this work qualifies capabilities, uncertainties, and limits of spatial structure-integrated force measurement as well as effects upon the machine characteristics. The two developed parameter identification procedures allow a fast and simple recalibration of the measurement models in operational machine state without requiring external knowledge or test setups. Finally, two realised methods of force control prove the capability of structure-integrated force measurement for force-controlled teaching as well as for contact control.

Linear switched reluctance motor (LSRM) drives are investigated and proved as an alternative actuator for vertical linear transportation applications such as a linear elevator. A one-tenth scaled prototype elevator focused on a home elevator with LSRMs is designed and extensive experimental correlation is presented for the first time. The proposed LSRM has twin stators and a set of translator poles without back-iron. The translators are placed between the two stators. The design procedures and features of the LSRM and the prototype elevator are described. The designed LSRM is validated through a finite element analysis (FEA) and experimental measurements. Furthermore, a control strategy for the prototype elevator is introduced consisting of four control loops, viz., current, force, velocity, and position feedback control loops. For force control, a novel force distribution function (FDF) is proposed and compared with conventional FDFs. A trapezoidal velocity profile is introduced to control vertical travel position smoothly during the elevator's ascent, descent, and halt operations. Conventional proportional plus integral (PI) controller is used for the current and velocity control loops and their designs are described. The proposed control strategy is dynamically simulated and experimentally correlated. Analytical and experimental results of this research prove that LSRMs are one of the strong candidates for ropeless linear elevator applications. However, the proposed FDF is assuming that the feedback current signals are ideal currents indicating actual phase currents without any measurement disturbances mainly arising from sensor noise, DC-link voltage ripple, measurement offset, and variations in the plant model. Meanwhile, real control systems in industry have measurement disturbance problems. Phase current corrupted by measurement disturbances increases torque or force ripple, acoustic noise and EMI. Therefore, this dissertation also presents a novel current control method to suppress measurement disturbances without extra hardware. The controller is based on an extended state observer (ESO) and a nonlinear P controller (NLP). The proposed method does not require an accurate mathematical model of system and can be implemented on a low-cost DSP controller. The proposed ESO is exploited to estimate the measurement disturbances on measured phase currents, and the proposed NLP compensates for the measurement disturbances estimated by the ESO. The performance of the proposed current control is validated through extensive dynamic simulations and experiments. Moreover, this rejection of measurement disturbances results in a reduction of force ripple and acoustic noise. Due to superior and robust current control performance, it is believed that the proposed method can be successfully applied into other motor drive systems to suppress measurement disturbances with the same promising results without extra hardware. / Ph. D.

La dextérité, notamment la pince de précision (i.e., opposition pouce-index) est une fonction très développée chez l’homme. Elle est basée sur l’habileté à contrôler précisément et indépendamment les forces et mouvements des doigts en relation avec les contraintes de la tâche. Les muscles de la main responsables du mouvement des doigts sont gouvernés par le système corticospinal (CS) latéral. La principale source de ce système CS est l’aire motrice primaire (M1), laquelle possède des projections CS directes sur les motoneurones des muscles de la main. Cependant, d’autres projections CS en provenance des aires motrices non primaires ont été trouvées, notamment en provenance de l’aire motrice supplémentaire (SMA). Chez l’homme, la fonctionnalité de cette voie dans le contrôle habile des doigts a peu été étudiée. L’objectif de cette thèse est d’étudier, chez l’homme, l’implication des projections CS de la SMA lors de contrôle manuel précis de force. Pour ce faire, nous avons utilisé la stimulation magnétique transcrânienne (TMS) et l’électroencéphalographie (EEG).A travers différentes études, nous avons pu mettre en évidence l’importante implication de la SMA dans la dextérité. Il semblerait que cette aire puisse agir en parallèle à M1 en régulant directement l’excitabilité des motoneurones de la moelle épinière. En conclusion, nos résultats suggèrent que M1 et SMAp ont une influence directe et efficace sur la production de force pendant des tâches motrices manuelles fines. / Human dexterity is a highly developed function based on the ability to independently and precisely control forces and movements of the fingers related to the constraints of the task. Hand muscles for finger movements are steered by the lateral corticospinal (CS) system. The main source of this CS system is the primary motor area (M1), which has direct CS projections on motoneurons innervating hand muscles. Recently, CS projections from non-primary motor area have also been found, especially from the supplementary motor area (SMA). However, the functionality of this CS tract in human manual force control is little studied. The aim of this thesis was to study the implication of the CS projections from SMA in precision manual force control, using electroencephalography (EEG) and transcranial magnetic stimulation (TMS).Altogether, the results obtained in our different studies show the important implication of SMA in dexterity. It appears that this area can act in parallel with M1, directly influencing excitability of spinal motoneurons. We conclude that M1 and SMA both have direct and efficient influence on force production during fine manual motor tasks.

Submitted by Aelson Maciera (aelsoncm@terra.com.br) on 2017-06-26T17:29:17Z No. of bitstreams: 1 TeseLFR.pdf: 6988870 bytes, checksum: dcf57a96d147df7a30bfe07d7b5469c6 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-06-28T19:38:51Z (GMT) No. of bitstreams: 1 TeseLFR.pdf: 6988870 bytes, checksum: dcf57a96d147df7a30bfe07d7b5469c6 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-06-28T19:38:57Z (GMT) No. of bitstreams: 1 TeseLFR.pdf: 6988870 bytes, checksum: dcf57a96d147df7a30bfe07d7b5469c6 (MD5) / Made available in DSpace on 2017-06-28T19:44:06Z (GMT). No. of bitstreams: 1 TeseLFR.pdf: 6988870 bytes, checksum: dcf57a96d147df7a30bfe07d7b5469c6 (MD5) Previous issue date: 2017-03-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / This study aims to answer the following question: why do the arduous working conditions continue to exist in the agricultural work process of the Agroindustrial Complex (CAI) of sugarcane in the State of São Paulo, Brazil, even with predominance of mechanized operations of every production process? The hypothesis pursued is: to remunerate the productive capital inserted in the logic of the Flexible Accumulation Regime, the Sugarcane CAI of São Paulo state must raise productivity to extremely high levels, either by creating relative or absolute surplus value, forming conditions of hazardous work. To verify this hypothesis, we used two data collection methods: a) a qualitative one, with semi-structured interviews and field observations, and b) a quantitative one, through application of questionnaires to managers of the Human Resources Management of the sugarcane CAI, and data obtained from secondary databases of public agencies and private consulting companies. The results indicate that, with the mechanization of the sugarcane production, technological innovations were implemented to increase the productivity of all operations, which influenced the concrete work. In this process of productive modernization, there was a combination between predominant mechanized operations, and remaining manual activities, both with high productivity and hazardous working conditions. The manual activities became important to improve the quality of the production process, while the machines operation became central in the valorization of the capital in the CAI. This strategy imposes exploitation of labor at degrading levels, lowering wages, causing illness, and making workers extremely vulnerable to labor force control mechanisms. Payment based on production continues to play a central role among these mechanisms, but in a modern way with the inclusion of personal performance indicators, that is also the basis for selection and training strategies. The arduous working conditions is a characteristic of the Sugarcane Complex modernization process, because it is necessary to the productive capital valorization in this complex, reproducing the Flexible Accumulation contradictions in this complex. / Este estudo tem como objetivo responder a seguinte questão: por que as condições de trabalho penosas continuam a existir no processo de trabalho agrícola do Complexo Agroindustrial Canavieiro do Estado de São Paulo, mesmo com predominância de operações mecanizadas em todas etapas da produção? A hipótese que guia esta pesquisa é: para remunerar o capital produtivo inserido na lógica do Regime de Acumulação Flexível, o CAI Canavieiro paulista deve elevar a produtividade a níveis extremamente altos, seja pela criação de mais-valia relativa ou absoluta, formando condições penosas de trabalho. Para verificar esta hipótese utilizamos dois métodos de coleta de dados: a) qualitativo, com entrevistas semi-estruturadas e observações de campo, e b) quantitativo, pela aplicação de questionário a gerentes de Recursos Humanos de usinas do CAI Canavieiro paulista, além da análise de dados obtidos em bases secundárias de órgãos públicos e de consultorias privadas. Os resultados apontam que, com a mecanização do corte de cana, diversas inovações tecnológicas foram implementadas no processo de trabalho agrícola para elevar a produtividade desta operação, influenciando o trabalho concreto em todas as etapas do cultivo da cana-de-açúcar. Neste processo de modernização produtiva é formada uma combinação entre operações mecanizadas predominantes e atividades manuais remanescentes, ambas com elevada produtividade, que é obtida pela intensificação e extensão da jornada de trabalho. As atividades manuais passam a ter a função secundária de aperfeiçoar a qualidade do trabalho, sem serem eliminadas, enquanto a operação de máquinas se torna central na valorização do capital no complexo. Esta combinação é mais uma estratégia empresarial para aumentar a exploração do trabalho a níveis degradantes, rebaixando os salários, causando adoecimentos e tornando os trabalhadores mais vulneráveis às estratégias gerenciais de controle da força-de-trabalho. O pagamento por produção continua tendo papel central dentre estes mecanismos, mas sob uma forma moderna, cujo cálculo é baseado em indicadores de desempenho, método que também é base para a seleção e o treinamento. Neste sentido, a reprodução do trabalho penoso se configura como uma característica do processo de modernização no CAI Canavieiro paulista, pois é necessário à remuneração do capital produtivo neste complexo produtor de commodities.