During transport of hand-held objects, the grip force is modulated in parallel with the load force changes. The control scheme underlying this grip-load force coupling involves subtle interplay between feedforward and feedback mechanisms. Based on internal models of the motor system and object properties, the load force can be predicted and the GF motor command can be specified in a feedforward manner. Moreover, during the course of arm movement, the CNS is informed by sensory feedback about mechanical events such as the lift-off of the object, slippage or excessive grip force. This information is used to correct the motor commands and to update the internal model of the motor apparatus and object. In this thesis, three experiments were conducted to examine the relative contributions of sensory-driven and anticipatory control of GF adjustments during cyclic vertical movement with a hand-held load. The main point was to assess whether internal models underlying the grip-load force coupling are robust when the environmental context was changed or when the sensory feedback was suppressed. Two experiments in parabolic flight were conducted to study the effects of a change in gravity on the dynamics of prehension. The main perturbation was that the novice subjects applied unnecessarily high safety margins during their first trial at 0 and 1.8 g in order to secure the grasp insofar as the gravitational component of the load force was unpredictable. By contrast, the temporal coupling between GF and LF was maintained regardless of the gravity conditions because the inertial component of the load could be still predicted from the arm motor command (efference copy). In the second study performed during parabolic flight, we have observed that the subjects were able to exert the same grip force for equivalent load generated either by a change of mass, gravity or acceleration despite the fact that it requires different arm motor commands. These two experiments brought further evidence that the predictive mechanisms largely contribute to the GF adjustment. Static forces such gravity are taken into account in the motor plan allowing adequate motor command and precise prediction of the incoming load force change. The GF output would depend on the precision of this prediction that can be evaluatedonly after the movement onset through sensory information about the actual state of the system. The third experiment performed in this thesis studied the role of cutaneous afferents in object manipulation by anesthetizing the thumb and index finger. In addition to their phasic slip-detection function, the cutaneous afferents are required for setting the background level of the grip force. Actually, in absence of tactile feedback, the temporal coupling between the grip and load forces is maintained but the mean magnitude of GF progressively decreases leading to object slipping. It is hypothesized that accumulating error occurred in the LF prediction leading to inadequate level of GF. Cutaneous afferents are thus required to correct and maintain the internal model of the arm-hand object system.

During transport of hand-held objects, the grip force is modulated in parallel with the load force changes. The control scheme underlying this grip-load force coupling involves subtle interplay between feedforward and feedback mechanisms. Based on internal models of the motor system and object properties, the load force can be predicted and the GF motor command can be specified in a feedforward manner. Moreover, during the course of arm movement, the CNS is informed by sensory feedback about mechanical events such as the lift-off of the object, slippage or excessive grip force. This information is used to correct the motor commands and to update the internal model of the motor apparatus and object. In this thesis, three experiments were conducted to examine the relative contributions of sensory-driven and anticipatory control of GF adjustments during cyclic vertical movement with a hand-held load. The main point was to assess whether internal models underlying the grip-load force coupling are robust when the environmental context was changed or when the sensory feedback was suppressed. Two experiments in parabolic flight were conducted to study the effects of a change in gravity on the dynamics of prehension. The main perturbation was that the novice subjects applied unnecessarily high safety margins during their first trial at 0 and 1.8 g in order to secure the grasp insofar as the gravitational component of the load force was unpredictable. By contrast, the temporal coupling between GF and LF was maintained regardless of the gravity conditions because the inertial component of the load could be still predicted from the arm motor command (efference copy). In the second study performed during parabolic flight, we have observed that the subjects were able to exert the same grip force for equivalent load generated either by a change of mass, gravity or acceleration despite the fact that it requires different arm motor commands. These two experiments brought further evidence that the predictive mechanisms largely contribute to the GF adjustment. Static forces such gravity are taken into account in the motor plan allowing adequate motor command and precise prediction of the incoming load force change. The GF output would depend on the precision of this prediction that can be evaluatedonly after the movement onset through sensory information about the actual state of the system. The third experiment performed in this thesis studied the role of cutaneous afferents in object manipulation by anesthetizing the thumb and index finger. In addition to their phasic slip-detection function, the cutaneous afferents are required for setting the background level of the grip force. Actually, in absence of tactile feedback, the temporal coupling between the grip and load forces is maintained but the mean magnitude of GF progressively decreases leading to object slipping. It is hypothesized that accumulating error occurred in the LF prediction leading to inadequate level of GF. Cutaneous afferents are thus required to correct and maintain the internal model of the arm-hand object system.

No description available.

Suite à un accident vasculaire cérébral (AVC), des déficits au membre controlatéral et ipsilatéral à la lésion cérébrale sont observés chez les personnes avec un AVC. La performance du membre ipsilatéral est déterminée par l’importance de la sévérité clinique du membre controlatéral ainsi que par l’adéquation du traitement bihémisphérique des informations sensori-motrices. L’objectif de la présente étude est de comparer la performance motrice de la main ipsilatérale lors de diverses tâches nécessitant un niveau plus ou moins complexe de traitement de l’information chez une clientèle hémiplégique ayant une faible sévérité clinique. Les résultats démontrent que les forces de pinces entre le pouce et l’index du membre ipsilatéral sont modulées et anticipées adéquatement chez les personnes avec un AVC ayant une faible sévérité clinique tel que démontré par des scores de cinq ou plus au Chedoke-McMaster Stroke Assessment (modules bras et main). La performance motrice du membre ipsilatéral lors de l’exécution d’une tâche de coordination bilatérale est comparable à celle du membre dominant des sujets sains lorsque la tâche est réalisée sans interaction entre les membres supérieurs (deux objets) et elle est perturbée lorsqu’elle implique une action coordonnée et réciproque des membres supérieurs sur un même objet. Ces personnes, ayant une bonne récupération motrice, ont donc une problématique centrale d’intégration et de traitement de l’information sensori-motrice lorsqu’il y a une complexification de la tâche à réaliser. Ces résultats suggèrent donc que les cliniciens devraient porter une attention plus particulière aux activités unilatérales et de coordination bilatérales lors le l’exécution de tâches complexes nécessitant un niveau d’intégration sensori-motrice élevé. / As a result of a cerebrovascular accident (CVA), deficits in the controlateral and ipsilateral limb of the brain lesion are observed in person who had had a CVA. The performance of the ipsilateral limb is determined by the clinical severity of the contralateral limb and by the adequacy of bi-hemispheral processing of information. The objective of the present study is to compare the motor performance of the ipsilateral hand during tasks implying different level of sensori-motor integration in patients with low clinical impairments. The results demonstrated that the pinch strengths between the thumb and the index finger of the ipsilateral limb are modulated and anticipated adequately in stroke persons who have a good motor recovery such as demonstrated by scores of five or more in the Chedoke-McMaster Stroke Assessment (arm and hand parts). The motor performance of the ipsilateral limb of stroke persons during the execution of a bilateral coordination task is comparable to the motor performance of the dominant limb of healthy subjects when the task is realized without interaction between upper limbs (two objects) and it is perturbed when it implies a coordinated and reciprocal action of upper limbs on the same object. Consequently, these stroke persons with a good motor recovery have a central problem of integration and processing of sensori-motor informations when a more complex task has to be realized. These results suggest that the clinicians should pay more attention during unilateral tasks and during tasks with bilateral coordination that require a higher level of sensori-motor integration.

Suite à un accident vasculaire cérébral (AVC), des déficits au membre controlatéral et ipsilatéral à la lésion cérébrale sont observés chez les personnes avec un AVC. La performance du membre ipsilatéral est déterminée par l’importance de la sévérité clinique du membre controlatéral ainsi que par l’adéquation du traitement bihémisphérique des informations sensori-motrices. L’objectif de la présente étude est de comparer la performance motrice de la main ipsilatérale lors de diverses tâches nécessitant un niveau plus ou moins complexe de traitement de l’information chez une clientèle hémiplégique ayant une faible sévérité clinique. Les résultats démontrent que les forces de pinces entre le pouce et l’index du membre ipsilatéral sont modulées et anticipées adéquatement chez les personnes avec un AVC ayant une faible sévérité clinique tel que démontré par des scores de cinq ou plus au Chedoke-McMaster Stroke Assessment (modules bras et main). La performance motrice du membre ipsilatéral lors de l’exécution d’une tâche de coordination bilatérale est comparable à celle du membre dominant des sujets sains lorsque la tâche est réalisée sans interaction entre les membres supérieurs (deux objets) et elle est perturbée lorsqu’elle implique une action coordonnée et réciproque des membres supérieurs sur un même objet. Ces personnes, ayant une bonne récupération motrice, ont donc une problématique centrale d’intégration et de traitement de l’information sensori-motrice lorsqu’il y a une complexification de la tâche à réaliser. Ces résultats suggèrent donc que les cliniciens devraient porter une attention plus particulière aux activités unilatérales et de coordination bilatérales lors le l’exécution de tâches complexes nécessitant un niveau d’intégration sensori-motrice élevé. / As a result of a cerebrovascular accident (CVA), deficits in the controlateral and ipsilateral limb of the brain lesion are observed in person who had had a CVA. The performance of the ipsilateral limb is determined by the clinical severity of the contralateral limb and by the adequacy of bi-hemispheral processing of information. The objective of the present study is to compare the motor performance of the ipsilateral hand during tasks implying different level of sensori-motor integration in patients with low clinical impairments. The results demonstrated that the pinch strengths between the thumb and the index finger of the ipsilateral limb are modulated and anticipated adequately in stroke persons who have a good motor recovery such as demonstrated by scores of five or more in the Chedoke-McMaster Stroke Assessment (arm and hand parts). The motor performance of the ipsilateral limb of stroke persons during the execution of a bilateral coordination task is comparable to the motor performance of the dominant limb of healthy subjects when the task is realized without interaction between upper limbs (two objects) and it is perturbed when it implies a coordinated and reciprocal action of upper limbs on the same object. Consequently, these stroke persons with a good motor recovery have a central problem of integration and processing of sensori-motor informations when a more complex task has to be realized. These results suggest that the clinicians should pay more attention during unilateral tasks and during tasks with bilateral coordination that require a higher level of sensori-motor integration.

Filter devices are central elements of radio units utilized for modern-day telecommunication. Leakages of radio waves and passive intermodulation are evolving more prominent as the frequency bands become crowded. The study in this thesis investigates the screw joints in the filter assembly to determine the influential parameters on the connection between the filter lid and its chassis. The clamp and release torque are vital factors in the resulting pre-load force. Besides the geometrical characteristics of the chassis andthe self-threading screw, the friction and surface roughness on the filter lid are significant contributors. Extensive testing revealed that increasing the countersink in the lead holeand applying the lubricant Molykote 1000 Paste increase the consequent clamp torque. After numerous cycles of thermal shock testing, the release torque does not show significant dissimilarities between the tested parameter combinations. A surface roughness test shows that applying a silver coating to the filter lid increases its surface roughness and thereby the friction of the screw head on the surface. In conclusion, the pre-load force will increase by changing the parameters as mentioned above, while it requires further testing to make a suggestion regarding the effect of the silver coating on the filter lid. / Filteranordningar är centrala delar i radioenheter vilka används vid nutida telekommunikation. Läckage av radiovågor och passiv intermodulation blir mer framträdande när frekvensbanden blir trånga. Studien i denna avhandling undersöker skruvförbanden i filtermonteringen för att bestämma de parametrar som har störst inverkan på anslutningen mellan filterlocket och dess chassi. Klämvrid- och lossdragningsmomentet är avgörande faktorer i den resulterande förspänningskraften. Förutom de geometriska egenskaperna hos chassit och den självgängande skruven, är friktionen och ytfinheten på filterlocket starktbidragande orsaker. Omfattande tester visade att en ökning av försänkningen i pilothålet och applicering av smörjmedlet Molykote 1000 Paste ökar det efterföljande klämvridmomentet. Efter talrika cykler av termisk chocktestning visar lossdragningsmomentet inga signifikanta skillnader mellan de testade parameterkombinationerna. Ett ytjämnhetstestvisar att applicering av en silverbeläggning på filterlocket ökar ytans strävhet och därmedfriktionen av skruvhuvudet på ytan. Sammanfattningsvis kommer förspänningskraften att öka genom att parametrarna ändras som nämnts ovan, samtidigt som det krävs ytterligare tester för att komma med ett förslag angående effekten av silverbeläggningen på filterlocket.

Diploma project is aimed to load force vector decomposition to x, y and z direction for complicated Skoda car parts. The methodology of decomposition is based on measuring of car parts deformation by strain gauges and mathematical identifation of force compoments by neural network (ANN). ANN will be trained by results of FE model simulations or by calibration on real car parts.

Master’s thesis, „Optimization of hanger design in petrochemical industry heaters”, describes a procedure and means, leading to better hanger design in various cases. The thesis describes several problems which are necessary to be solved in hanger design. Technical expertise is executed on hangers of various designs. The procedure of optimization is shown on one chosen hanger design.

This master thesis aims to develop a test methodology for electromechanical linear actuators. A linear actuator acts as a linear motor, converting a power source to linear motion. The electromechanical linear actuator in this project has an electric motor as its power source and uses a rack and pinion system to transfer that power to linear motion.  The test methodology is to impose a force onto the rack of the actuator, to ensure that operation under a load scenario is within specification. To accomplish this, the design of a test rig implementation is analyzed. The test rig consists of the test unit, which is to be tested, the load unit, which is to provide the load force, and a control system for the load unit. The load unit is another linear actuator and is controlled via a load cell. The load cell gives out the load force being applied, and the controller gives out the corresponding appropriate motor command to the load unit to ensure the load force is as desired. This analysis is done through simulation of the setup. Viable options for the setup were first analyzed in order to implement the deemed promising options for a setup into a simulation environment. The simulation environment in this project was Simscape, an extension of MATLAB’s Simulink. In simulation the parameters for the test rig were rigorously analyzed, in order to determine acceptable thresholds. The primary load unit tested was another electromechanical linear actuator from Cascade Drives, the model A-100-8P. Two secondary setups, one using the same model as being tested, and another setup using two of the models being tested. Simulation found that the suggested options’ applied load force have a poor rise time, large overshoot and substantial oscillation errors. The primary source for this was determined to be the latency between load cell input, and motor command output in the controller. The poor metrics from the result could lead to problems when emergency braking, and with a long honing period, which would render most test data unusable.