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We have derived a new performance measure, product of minors of the Jacobian matrix, that tells how far kinematically redundant manipulators are from singularity. It was demonstrated that previously used performance measures, namely condition number and manipulability measure allowed to change configurations, caused repeatability problems and discontinuity effects. The new measure, on the other hand, assures that the arm solution remains in the same configuration, thus effectively preventing these problems.

This thesis presents an evolutionarily design change for the Delta parallel robot. The proposed design change increases the useful workspace of the robot and aids in permanently avoiding singularities in the workspace. This is accomplished by means of a new intermediate link parallel to the 4 bar linkage. The addition of the new link simultaneously increases the total workspace volume and decreases the dexterity without significantly affecting the stiffness. The design is analyzed and the inverse kinematics, Jacobian, sti ness and dexterity relations are formulated. The relations are then converted into a form that is usable by MATLAB to calculate di erent workspaces that illustrate the advantages of the new design. Subsequently, an optimization problem is formulated that aims to take advantage of the new attributes to create a balanced robot that further illustrates the benefits of the new design. The results are clearly illustrated by comparing plotted sections of workspace from both the optimized and unoptimized workspace. Lastly, the design is developed into a 3D model which is then fabricated into a working prototype to test and verify functionality. / UOIT

This thesis presents a skillful robotic wrist system using a visual servo control technique to demonstrate dexterity of the mechanical wrist from the viewpoint of the table tennis. A ball and plate system is chosen as the first stage of this long-term project. A two degrees-of-freedom robotic wrist with an acrylic plate attached as the end effector is developed. A visual feedback control system is implemented with a web cam and a personal computer to acquire the ball's position. In order to implement decision making for changing orientation of the plate, a Linear Quadratic Regulator (LQR) is designed. As a result, the ball can be balanced at specific positions. Experimental results exhibit preliminary and promising achievement. Based on this progress, further improvement and deeper exploration can be carried on in the future.

Humanoid robots have proven to be very useful and could revolutionize the way humans live. Knowing human anatomy and behaviour helps improve a robotic mechanisms ability to perform human tasks. The following thesis introduces the concept of a threefingered robot hand and its driving mechanism. The hand includes two fingers and a thumb. Using the concept of “an under actuated system”, each finger consists of three revolute joints which are driven by two actuators and tooth belt transmission system. The thumb has two joints but only one joint is active and actuated by one motor. The passive joint is designed to set the initial position of the thumb on the piano key if necessary. Required angle of rotation for each joint has been calculated through Inverse Kinematics. Once the fingertip presses the piano key, it should apply 1N force to play a note. Force Sensing Resistors at each finger tip, as a control method, are introduced to the system to accurately measure the amount of applied force from the finger tip on the key and increase the angle of rotation of the motor if needed. Stress and deformation of the joints have been studied through Finite Element Analysis. A prototype model, consisting of a single finger was built to better understanding the functionality of the concept. Analysis of this model, led to necessary modification of the transmission system and some design revisions to each link. Genetic Algorithm using MATLAB was used to optimize the performance Index of a finger. Finally the hand assembly including all the components and driving mechanism was constructed and experimented in the playing mode. / UOIT

Aims and objectives: The general aim of this study was to determine the personal respiratory exposure and biological monitoring of manganese (Mn) present in welding fumes as well as its neurological influence on welders. The objectives of this study were: (i) to assess the respiratory exposure of welders to Mn present in welding fumes; (ii) to assess the biological Mn load of welders via the use of nail clippings; (iii) to establish possible correlations between respiratory exposure to Mn and its presence in nail clippings, and (iv) to determine the possible difference in finger dexterity and coordination between Mn exposed welders and a control group. Methods: A gravimetrical method was used to determine the respiratory exposure of welders. A cassette containing a 0.8-μm, cellulose ester membrane filter, attached to the side of a welding helmet provided, was connected via a stainless steel fitting to the inside (respiratory zone) of the helmet. Chemical analysis (metal content) of the welding fumes was done according to the NIOSH 7300 method, using Inductively Coupled Argon Plasma, Atomic Emission Spectroscopy (ICP-AES). Nail clippings were collected at the beginning and end of the study to determine the Mn level in the nails in both welders as well as paired controls. The nails were deposited into small, plastic vials and also analysed according to the NIOSH 7300 method. A Perdue pegboard and mirror drawing test was also conducted to determine the influence of Mn exposure on finger dexterity and hand-eye coordination of welders. Results: Mn exposure in the welding fumes did not exceed the occupational exposure limit – recommended limit (OEL-RL) (1 mg/m3) of the Regulations for Hazardous Chemical Substances (RHCS), although two of these exposures exceeded the action level (0.5 mg/m3). No statistical significant correlations were found between the Mn respiratory exposure and the Mn found in the nails of the welders. Mn in the nails of exposed welders was statistical significantly higher (p = 0.003) than that of controls. The only statistical significant differences found in the motor function tests between the controls and welders were the test which was done by using their non-dominant hand in the beginning of the study (p = 0.016) and when the non-dominant hand values were pooled (p = 0.012). The usage of both hands simultaneously showed results that leaned toward statistical significant decrease of the welders compared to the control subjects (p = 0.090). In all these cases the controls inserted more pins than the welders. Only one moderately positive correlation (r = 0.612; p = 0.02) was found between Mn in the welding fumes and the number of errors made in the mirror drawing coordination test done by the welders. Discussion and Conclusions: The Mn in the nails of the control group was significantly lower than the Mn in the nails of the welders. This indicates that Mn respiratory exposure may influence Mn body burden although no correlation between Mn in welding fumes and Mn in nails were found. Nail Mn may serve as a biomarker to determine Mn body burden. Only the use of the non-dominant hand of the control subjects compared to the welders showed a significant decrease in finger dexterity of the welders. The moderately positive association between the Mn in the welding fumes and the number of errors made in the mirror drawing coordination test done by the welders indicates that with an increase in Mn in welding fumes, a decrease in hand-eye coordination will occur. It can be concluded that welders’ finger dexterity and hand-eye coordination may be influenced by the exposure to Mn in the welding fumes. / Thesis (MSc (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2013

Aims and objectives: The general aim of this study was to determine the personal respiratory exposure and biological monitoring of manganese (Mn) present in welding fumes as well as its neurological influence on welders. The objectives of this study were: (i) to assess the respiratory exposure of welders to Mn present in welding fumes; (ii) to assess the biological Mn load of welders via the use of nail clippings; (iii) to establish possible correlations between respiratory exposure to Mn and its presence in nail clippings, and (iv) to determine the possible difference in finger dexterity and coordination between Mn exposed welders and a control group. Methods: A gravimetrical method was used to determine the respiratory exposure of welders. A cassette containing a 0.8-μm, cellulose ester membrane filter, attached to the side of a welding helmet provided, was connected via a stainless steel fitting to the inside (respiratory zone) of the helmet. Chemical analysis (metal content) of the welding fumes was done according to the NIOSH 7300 method, using Inductively Coupled Argon Plasma, Atomic Emission Spectroscopy (ICP-AES). Nail clippings were collected at the beginning and end of the study to determine the Mn level in the nails in both welders as well as paired controls. The nails were deposited into small, plastic vials and also analysed according to the NIOSH 7300 method. A Perdue pegboard and mirror drawing test was also conducted to determine the influence of Mn exposure on finger dexterity and hand-eye coordination of welders. Results: Mn exposure in the welding fumes did not exceed the occupational exposure limit – recommended limit (OEL-RL) (1 mg/m3) of the Regulations for Hazardous Chemical Substances (RHCS), although two of these exposures exceeded the action level (0.5 mg/m3). No statistical significant correlations were found between the Mn respiratory exposure and the Mn found in the nails of the welders. Mn in the nails of exposed welders was statistical significantly higher (p = 0.003) than that of controls. The only statistical significant differences found in the motor function tests between the controls and welders were the test which was done by using their non-dominant hand in the beginning of the study (p = 0.016) and when the non-dominant hand values were pooled (p = 0.012). The usage of both hands simultaneously showed results that leaned toward statistical significant decrease of the welders compared to the control subjects (p = 0.090). In all these cases the controls inserted more pins than the welders. Only one moderately positive correlation (r = 0.612; p = 0.02) was found between Mn in the welding fumes and the number of errors made in the mirror drawing coordination test done by the welders. Discussion and Conclusions: The Mn in the nails of the control group was significantly lower than the Mn in the nails of the welders. This indicates that Mn respiratory exposure may influence Mn body burden although no correlation between Mn in welding fumes and Mn in nails were found. Nail Mn may serve as a biomarker to determine Mn body burden. Only the use of the non-dominant hand of the control subjects compared to the welders showed a significant decrease in finger dexterity of the welders. The moderately positive association between the Mn in the welding fumes and the number of errors made in the mirror drawing coordination test done by the welders indicates that with an increase in Mn in welding fumes, a decrease in hand-eye coordination will occur. It can be concluded that welders’ finger dexterity and hand-eye coordination may be influenced by the exposure to Mn in the welding fumes. / Thesis (MSc (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2013

Healthy aging influences peripheral and central levels of the neuromotor system. These age-related changes contribute to the decline in dexterous manual behavior. Difficulty in performing activities of daily living increases reliance on external assistance. Understanding specific mechanisms leading to the decline in fine manual performance is crucial for their rehabilitation. In this thesis, we have attempted to increase our awareness of the causes underlying manual disability in old age. The first study investigated how old adults apply forces and moments on a freely-movable object using a precision grip (thumb and index finger) during functionally-relevant tasks. During the grasp-lift task old adults misaligned their thumb and finger contacts and produced greater grip force, greater external moments on the object around its roll axis, and oriented force vectors differently compared with young adults. During a precision-orientation task of inserting a slot on the object over a bar (`key-slot' task), old adults were more variable in digit-tip force directions and performed the key-slot task more slowly. With practice old adults aligned their digits, reduced their grip force, and minimized external moments on the object. We conclude that with old age comes with a reduced ability to control the forces and moments applied to objects during precision grasp and manipulation. This may contribute to the ubiquitous slowing and deteriorating manual dexterity in healthy aging. Another study investigated the effects of transcranial direct current stimulation (tDCS) to the contralateral M1 combined with motor training (MP) on changes in the forces applied to the object during grasp and manipulation. We also measured performances on functional tasks in healthy elderly individuals. Our results indicate that anodal tDCS+MP facilitates retention of learning on a skillful manual task in healthy old adults. Furthermore, improved retention on the pegboard test was associated with reduced force variability on the key-slot task that demanded similar precise control over the forces applied to the object. These findings suggest that the improvement in force steadiness is one of the potential mechanisms through which short-term anodal tDCS during motor training improved performance on a functional task that outlasted the intervention period. Furthermore, anodal tDCS over M1 in combination with motor practice also influenced motor response to tasks that critically depend on sensory signals in healthy old adults. Finally, we found that, in healthy elderly individuals, the memory representations scaling the lift force for the grip and lift task generalized, while the training-based learning on the ballistic task showed an incomplete transfer to the contralateral hand. These differences may indicate task-dependent interhemispheric transfer of learning in old age. Collectively, the work presented in this thesis demonstrates that the performance on dexterous manual tasks in healthy old adults may depend on how they configure their grasp, and control their finger forces (both linear and rotational) applied to the grasped object, specifically how smooth is the applied force.

Work in many environments with chemical or biological agents requires the use of personal protective equipment such as gloves and respirators. It is well established that glove thickness affects finger dexterity. There is further evidence that visual constraints (e.g., visual acuity) and gender may also impede finger dexterity. Therefore, the personal protection may place a barrier to the agent, but performance or productivity will decrease. The purpose of this study is to examine the potential effects of gloves and visual acuity as well as gender and first order interactions on task performance using standard dexterity tests. Five men and five women volunteered as participants in the study. There were four levels of gloves: None (as control), 9 mil, 18 mil, and 28 mil unlined latext gloves were used. There were five levels of visual acuity: None as a negative control, masked goggles as a positive control, and masked goggles with occlusion foils of 20/50, 20/100 and <20/300. A full factorial design was used and the combinations were randomly assigned. Three platforms were used for this study: Prudue Pegboard, Grooved Pegboard and the placing task of the Minnesota Dexterity Test. These results showed that the main factors of Glove and Goggle were significant for all platforms and Gender was significant for the Purdue Pegboard and Grooved Pegboard. There were significant interactions among the main effects but these did not demonstrate a consistent pattern. The largest differences in performance were associated with the gloves, even at the last thickness of 9 mil. The increased thickness to 18 and 28 mil resulted in significant and large losses of performance. It was most marked with the smallerpieces of the pegboard tasks. Generally women performed better than men for the pegboard tasks as expected and there were no differences for the larger pieces of the Minnesota tasks. Except for the greatest decrement in visual acuity, the differences among the levels of visual acuity were not significant. The expectedinteraction between gloves and acuity was not observed.