MULTI-DIGIT HUMAN PREHENSION

The current dissertation addresses the central nervous system (CNS) strategies to solve kinetic redundancy in multi-digit static prehension under different geometries of hand-held objects and systematically varied mechanical constraints such as translation and rotation of the hand-held object. A series of experiments conducted for this dissertation tested the following hypotheses suggested in the current literatures for multi-digit human static prehension: Hierarchical organization hypothesis, principle of superposition hypothesis, proximity hypothesis, and mechanical advantage hypothesis. (1) Forces and moments produced by fingers during circular object prehension were grouped into two independent subsets: one subset related to grasping stability control and the other associated with rotational equilibrium control. This result supports the principle of superposition hypothesis. Individual fingers acted synergistically to compensate each other's errors. This result confirms the hierarchical organization hypothesis in circular object prehension. (2) During fixed object prehension of a rectangular object, the closer the non-task fingers positioned to the task finger, the greater the forces produced by the non-task fingers. However, during free object prehension, the non-task fingers with longer moment arms produced greater forces. The former and latter results support the proximity hypothesis and the mechanical advantage hypothesis, respectively. (3) The grasping stability control and rotational equilibrium control were decoupled during fixed object prehension as well as free object prehension. This result supports the principle of superposition hypothesis regardless of the mechanical constraints provided for these two prehension types. (4) During torque production, the fingers with longer moment arms produced greater forces when the fingers acted as agonists for the torque production. Therefore, the mechanical advantage hypothesis was supported for agonist fingers. (5) Coupling of thumb normal force and virtual finger normal force was not necessitated when horizontal translation of hand-held object was mechanically fixed. However, the coupling of two normal forces was always observed regardless of given translational constraints, and these two normal forces were independent to other mechanical variables such as tangential forces and moments. This result supports the principle of superposition hypothesis in static prehension under varied combinations of translational constraints

Multi-Finger Interaction and Synergies in Finger Flexion and Extension Force Production

The aim of this study was to discover finger interaction indices during single-finger ramp tasks and multi-finger coordination during a steady state force production in two directions, flexion, and extension. Furthermore, the indices of anticipatory adjustment of elemental variables (i.e., finger forces) prior to a quick pulse force production were quantified. It is currently unknown whether the organization and anticipatory modulation of stability properties are affected by force directions and strengths of in multi-finger actions. We expected to observe a smaller finger independency and larger indices of multi-finger coordination during extension than during flexion due to both neural and peripheral differences between the finger flexion and extension actions. We also examined the indices of the anticipatory adjustment between different force direction conditions. The anticipatory adjustment could be a neural process, which may be affected by the properties of the muscles and by the direction of the motions. The maximal voluntary contraction (MVC) force was larger for flexion than for extension, which confirmed the fact that the strength of finger flexor muscles (e.g., flexor digitorum profundus) was larger than that of finger extensor (e.g., extensor digitorum). The analysis within the uncontrolled manifold (UCM) hypothesis was used to quantify the motor synergy of elemental variables by decomposing two sources of variances across repetitive trials, which identifies the variances in the uncontrolled manifold (VUCM) and that are orthogonal to the UCM (VORT). The presence of motor synergy and its strength were quantified by the relative amount of VUCM and VORT. The strength of motor synergies at the steady state was larger in the extension condition, which suggests that the stability property (i.e., multi-finger synergies) may be a direction specific quantity. However, the results for the existence of anticipatory adjustment; however, no difference between the directional conditions suggests that feed-forward synergy adjustment (changes in the stability property) may be at least independent of the magnitude of the task-specific apparent performance variables and its direction (e.g., flexion and extension forces)

SCUBA DIVING FIN TYPES AND CHARACTERISTICS OF DIVER'S PROPULSIVE MOTION

The purpose of this study was to analyze quantitative evaluation of propulsive motion as different fin types and degree of skill that affected motion. Three skilled dive masters and three unskilled sUbjects participated in the study. The types of fin are paddle style and propller style which have different functional systems for propulsion each other. Two video cameras (Panasonic 0-5100, frame rate: 60 Hz) are used for motion analysis, and two load cells are used for measuring propulsion force. The measuring system for propulsion force was designed to acquire the pulling force. Matlab (Mathwork, Inc.) was used for separating each direction force and calculate the impulse. Kwon3D (Visol, Inc) was used to analyze the fin kick motion. Digitizing points were hip, knee and ankle joint. The subjects were tied with a rope but they could move on all direction a litte bit. Three-way ANOVA was used for analyzing significance of difference between groups, stroke rates (30-60-maximun stroke/min) and fin-types. The results of this work indicate that stroke rate was controlled by the range of knee angle, and the adequate fin style was different according to the diVing skill

EFFECT OF THE MECHANICAL CONSTRAINTS ON MULTI-FINGER PREHENSION

INTRODUCTION: When a finger produces a force, other non-task fingers of the hand also produce an involuntary force. This phenomenon has been known as finger enslaving (Zatsiorsky et al. 1998). In the present study, we examined the characteristics of the enslaving matrices obtained by the fixed object prehension and the free object prehension. Previous studies showed that two innate constraints (i.e. peripheral and central constraints) affect the performance of finger force production during fixed object prehension. However, it is unknown how the mechanical constraints, which are imposed externally, play a role in grasping tasks. The purpose of the current study was to investigate the finger enslaving for the fixed and free object prehension during maximum finger force production tasks in statics. The central nervous system (CNS) is required to satisfy linear and rotational equilibrium during the free object prehension, while the CNS does not need to satisfy any external constraint

Multi-Phase Fault Tolerant PMSM Drive Systems

The drive to develop electric machines with a wide constant power-speed range (CPSR), high torque capabilities, excellent efficiency, superior reliability, and a reduced environmental footprint for EV traction and ship propulsion systems has led to research interest in various Permanent Magnet Synchronous Motors (PMSM). One particular area of interest is multi-phase fault tolerant PMSM drive systems, which are integral to the development of electric traction systems with all-inclusive motors that include sensors, inverter modules, and a cooling system, much like an automobile engine. Furthermore, these designs simplify fault condition maintenance because their independent single-phase structure allows them to be used with replaceable modular inverter units which have one H-bridge for each phase. In order to provide high reliability for the PMSM drive systems, even in a fault condition, simple but effective current control methods are necessary. An interior PMSM configuration with 5 independent phases is presented for electric vehicle (EV) traction and ship propulsion applications along with the proposed design procedure as well as an associated inverter design and current control methods. The proposed design process is verified using finite element analysis (FEA). An existing 5-phase 15-slot 4-pole Interior PMSM was modified to remove the neutral point, thus allowing for independent control of the 5 phases with 5 H-bridge inverters through a fabricated custom-made control board. Bipolar and unipolar switching methods were evaluated and an effective switching method was proposed to drive the motor. Closed loop speed control was implemented using Step VSI control, SPWM control, and hysteresis control methods. Finally, the 5-phase 10-lead PMSM systems were evaluated under the various control methods using simulated and experimental data after fabricating a new inverter interface board with TI floating point DSP, Delfino (F28335). The results suggest that multi-phase fault tolerant PMSM drive systems could play a key role in the future of EV traction and ship propulsion systems. An interior PMSM configuration with 5 independent phases is presented for electric vehicle (EV) traction and ship propulsion applications along with the proposed design procedure as well as an associated inverter design and current control methods. The proposed design process is verified using finite element analysis (FEA). An existing 5-phase 15-slot 4-pole Interior PMSM was modified to remove the neutral point, thus allowing for independent control of the 5 phases with 5 H-bridge inverters though a fabricated custom-made control board. Bipolar and unipolar switching methods were evaluated and an effective switching method was proposed to drive the motor. Closed loop speed control was implemented using Step VSI control, SPWM control, and hysteresis control methods. Finally, the 5-phase 10-lead PMSM systems were evaluated under the various control methods using simulated and experimental data after fabricating a new inverter interface board with TI floating point DSP, Delfino (F28335). The results suggest that multi-phase fault tolerant PMSM drive systems could play a key role in the future of EV traction and ship propulsion systems

A STUDY ON THE OPTIMAL DEFENSE POSITION OF HANDBALL GOALKEEPER: FACING A FORWARD JUMP SHOT MADE FROM 9M

The purpose of the study was to derive an optimal defense position for goalkeepers through calculating ideal defense area and actual defense area when blocking forward jump shots from 9 m distance. A total of 9 men's handball matches were captured with 4 digital video cameras from the 94th Korea National Sports Festival with consent from the Korea Handball Federation. Video clips with 78 forward jump shots from 9 m distance which included the whole movements of goalkeeper were analyzed. The ball's speed in the forward jump shot, release point of the ball, goalkeeper's defensive stance, and defensive position were analyzed. The actual defense position of goalkeeper was 1.10*0.37 m and the optimal defense position calculated through the movements of goalkeeper was 1.45 m from the goal line

EFFECTS OF CONTACT SURFACE PROPERTIES ON MULTI-FINGER FORCE PRODUCTION TASKS IN HUMANS

The purpose of the current study was to investigate the effect of contact surface properties, which presumably determine the level of stimulation on the cutaneous receptors, on multifinger force production and synergic actions of finger forces. The framework of the uncontrolled manifold (UCM) hypothesis was used to quantify indices of multi-finger synergies stabilizing total force in normal and tangent directions as well as the direction of resultant force (i.e., force angle) during steady-state force production. There was significant effect of contact surface on the magnitude of maximal voluntary contraction force. Also, there was a significant effect of the contact surface on the indices of force-direction (i.e., force angle) stabilizing synergies meaning that the stimulation on the cutaneous receptors could be an effective way to enhance the abili to organize the direction of finger forces

Comparative Analysis of Lunge Techniques: Forward, Reverse, Walking Lunge

The study aims to find the basis for the efficiency of lunge and risk of injury by comparing mechanical variables in various lunges (forward lunge, reverse lunge, and walking lunge). Four participants who were familiar with the three lunge movements were recruited to achieve the purpose of the study. The resultant hip joint moment, resultant knee joint moment, and resultant knee joint force were analyzed during the three lunge movements. Eight muscle of lower extremity were also analyzed using EMG. In conclusion, reverse lunge movement was found to be favorable in achieving the primary goal of lunge exercise, which is the development of gluteus maximus and quadriceps femoris, as it resulted in higher agonist muscle activities with relatively low momentary maximum knee shearing force compared to the other lunge techniques

Effect of Anticipatory Shooting Strategy on Performance Consistency in Skilled Elite Archer

PURPOSE This study examined the effect of anticipatory control strategies on stable upright posture and consistency in archery performance among skilled elite archers. METHODS Nine skilled archery players participated in this study and performed repeated shooting trials under two different shooting conditions: clicker and non-clicker. In the clicker condition, archers shot in response to clicker signals, whereas in the non-clicker condition, they used an anticipatory strategy to determine shooting time in a self-paced manner without using the clicker. A motion capture system with six infrared cameras was used to measure the coordinates of the bow and archers’ hands, which were then used to calculate the aiming precision index and draw-related variables. Electromyography of the lower leg muscles and the center of pressure (COP) were also analyzed for a short period immediately before release to determine the differences in anticipatory postural adjustments (APAs) between the two shooting conditions. RESULTS The non-clicker condition resulted in a relatively short drawing duration and better precision index. The COP speed rapidly increased immediately before the release (i.e., APAs), and the rate of increase was lower in the non-clicker condition than in the clicker shooting condition. Furthermore, smaller APAs were significantly correlated with better-aiming precision in the non-clicker condition. CONCLUSION These findings suggest that using an anticipatory strategy rather than reacting to a clicker can improve archery performance consistency by reducing APA and ensuring a stable shooting posture. This strategy can be used in archery training to predict clicker signals during the aim-release stage

DIFFERENCES OF POSTURE ON PUSH-OFF PHASE BETWEEN ACTUAL SPEED SKATING AND SLIDE-BOARD TRAINING

The slide-board training is a feasible technology to exercise skating during the off-season. While slide-board is much different from ice surface of the actual skating situation, it may distort actual skating posture. The purpose of this study was to analyze the differences in posture during push-off phase between an actual speed skating condition and on slideboard. The result showed that on the slide-board distance between two feet were shorter, so were the rotation angles of both feet, the hip angle was lower during the whole phase, while knee and ankle angles were higher. In conclusion, the restriction of the space on slide-board affected the position and rotation of both stable and push-off feet as well as the joint extension of the stable leg. Hence, the structural design of slide-board needs to be improved to facilitate the extension of knee and ankle in the medial-lateral direction