ASSESSMENT OF LOWER LIMB MUSCLE STRENGTH IN ATHLETES BY USING HAND-HELD DYNAMOMETER: A RELIABILITY STUDY

Background and Aims: Muscle strength is the key area to measure the functional status of an individual. Different tools and techniques has been used to detect strength differences and deficits. Hand- held dynamometer is one of the most affordable and handy tools used for this purpose. This study was designed to determine intra-rater reliability of hand- held dynamometer to measure muscle strength in different muscle groups of lower extremity of young athletes. It will further explore the reliability of hand- held dynamometer. Methodology: In this cross- sectional study young players of squash and badminton in the age group of 18-26 years were selected. The participants were recruited by non- probability convenience sampling technique. The strength of major muscle groups of lower limb was measured by a single male tester twice with gap through isometric make test of dynamometer. The intra-class correlation coefficient was then calculated for two readings of each muscle group by using SPSS version 21. Results: The intra- class correlation coefficient showed good to excellent reliability. The hip abductors, hip adductors, hip extensors of left side, knee flexors and knee extensors showed excellent reliability. Whereas, hip flexors, ankle plantar- flexors and dorsi-flexors of both sides showed excellent reliability at 95 % confidence interval. Conclusion: The isometric make test of dynamometer is a reliable tool for the objectification of strength of lower limb in   young players participating in squash and badminton.

Application of Sliding Mode Theory to Guidance and Control of Unmanned Aerial Vehicles

The main objective of the lateral guidance algorithm is to keep the vehicle on preplanned desired path by controlling the lateral track errors during flight and to keep them as small as possible by generating suitable reference commands. Cross track (lateral) error control of unmanned aerial vehicles (UAVs) in the presence of uncertainties and disturbances with bounded control input (φref ) is a challenging task. The path following guidance law needs to be devised using generalized kinematic model and by explicitly considering the UAV autopilot dynamics. However, the inclusion of these dynamics into guidance design further complicates the problem by increasing the relative degree, and stability, and control boundedness becomes difficult to analyze. To address these challenges, several studies for inclusion of autopilot dynamics into guidance design are presented in this thesis for lateral path following applications. Firstly, the guidance and control framework based on sliding mode theory is presented to solve the two dimensional path-following problem. Limitations of the existing nonlinear sliding surface for lateral guidance are indicated and thus two novel stable nonlinear sliding manifolds are proposed for the guidance problem. The two surfaces are then employed to generate two new nonlinear guidance laws for UAV path following. The proposed guidance schemes rely on First Order Sliding Mode Control (FOSMC) algorithm derived at the kinematic level generating reference bank commands. The autopilot based on super twisting algorithm using linear sliding surface forms the inner control loop for control actuation. The autopilot is involved in the feedback nonlinear sliding mode based guidance law design for path following of UAVs. The major contribution of this work is the dynamics of the autopilot taken into account for guidance law design, along-with saturation constraints on guidance commands for high performance in all scenarios. To solve relative degree two problem, a nonlinear sliding manifold is used with real twisting algorithm for guidance design, the guidance loop generates bank angle commands for executing roll maneuvers. The strategy provides a framework to implement the developed controller on the experimental vehicle without modifying the key structure of the original autopilot controller. viii Moreover, an innovative sliding mode based partially integrated lateral guidance and control scheme for UAVs is proposed. Guidance and control framework based on second order sliding modes is presented to solve the problem of two dimensional path-following. The main contribution of the technique presented here is the partial integration of the two loops i.e., a guidance and control system via series interconnection of two stable sliding manifolds. The proposed guidance scheme relies on a nonlinear switching surface with the real twisting algorithm derived at the kinematic level, generating roll error commands. The autopilot based on the super-twisting algorithm using a linear sliding surface forms the autopilot loop. Finally, a new guidance law for accurate following of flight path to observe tight ground track control is presented. The unique feature is to explicitly account for autopilot constraints by defining a 3-D sliding manifold. The guidance solution described is based on state stabilization of kinematics-dynamics trajectories i.e., the guidance law is evolved based on the knowledge of dynamical characteristics of the UAV. A robust FOSMC guidance algorithm is derived using the nonlinear 3-D sliding manifold to develop the guidance law. For the proposed schemes, proof of existence of sliding mode, actuation boundedness and performance of the path-following closed-loop system is analyzed. Flight results validate the performance and effectiveness of the proposed framework for guidance and control design. Keywords: Sliding Mode Control, Unmanned Aerial Vehicles (UAVs), Guidance & Control, Sliding Surface, Cross Track Error, Lateral Guidance.