Rong Tyai Wang

TRACKING AND BALANCE CONTROL OF BALL AND PLATE SYSTEM

Abstract An extension of the traditional ball and beam system into a ball and plate system is constructed using two magnetic suspension actuators for two degree of freedom control. System characteristics of the mathematical model with control configuration are developed. For control performance, a single‐chip microprocessor, serving as control kernel with basic electronic components, is designed and implemented. According to the backstepping control design procedure, the proposed controller is fabricated and tested. Several scenarios of dynamic operation, including oscillatory stabilization and circular trajectory tracking are tested to verify the system performance and capability.

Vibration of multispan mindlin plates to a moving load

Abstract The component method is proposed to study the free vibration of a multispan Mindlin plate. The orthogonality of any two distinct sets of the mode shape functions is shown. A method of modal analysis is then presented to study the dynamic responses of the plates. A line load moving on the plate is used as an example. The effects of span number, rotatory intertia and transverse shear deformation on the critical velocity, the maximum displacement and the maximum moment of plates are discussed. Furthermore, the effect of the thickness‐length ratio on the critical velocity is also investigated. The results of a Mindlin plate are compared with those of a classical plate.

Change in Pitching Biomechanics in the Late-inning in Taiwanese High School Baseball Pitchers

Abstract Pei-Hsi Chou, P, Huang, Y-P, Gu, Y-H, Liu, C, Chen, S-K, Hsu, K-C, Wang, R-T, Huang, M-J, and Lin, H-T. Change in pitching biomechanics in the late-inning in Taiwanese high school baseball pitchers. J Strength Cond Res 29(6): 1500–1508, 2015—Repetitive overhead throwing may result in overuse injuries and a change in the pitching mechanics of a baseball pitcher. Accordingly, the purpose of this study is to quantify the changes in the muscle strength and pitching motion kinematics in the late-innings stage of a baseball game. Sixteen healthy baseball pitchers (16.77 ± 0.73 years) recruited from a high school, which won the National High School Baseball Championship in Taiwan in 2011; each performed 100 pitches in a bullpen throwing session. Isometric muscle strength measurements and joint kinematic data were obtained before and after the throwing session. The mean Borgs Rating of Perceived Exertion index was found to have a value of 14.14, indicating a medium-to-large degree of perceived tiredness. The results showed that the ball velocity and horizontal abduction angle decreased significantly as the pitchers became tired. Moreover, the upper torso forward tilt and knee flexion angle both increased significantly at the moment of ball release. Finally, the muscle strength of the upper extremity remained decreased 2 days after the bullpen throwing session. Overall, the results suggest that an adequate amount of rest and specific strengthening programs for the shoulder external rotator, shoulder internal rotator, shoulder flexor, shoulder extensor, shoulder adductor, and shoulder abductor muscles are recommended to the coaches and for adolescent baseball pitchers. In addition, the changes in pitching mechanics noted in this study should be carefully monitored during the course of a baseball game to minimize the risk for overuse injuries.

A new ball and beam system using magnetic suspension actuator

This paper presents a ball & beam system using a pair of magnetic suspension actuators by applying precision position control in performance. System characteristics including magnetic actuator, linear position sensor, load current control and feedback loop are discussed. To achieve the control, a single chip microprocessor with basic level electronics is designed and implemented. The designed system model is derived from Lagrangian function for system controller implementation. Oscillatory stable operation and sinusoidal tracking operation are tested to verify the system performance and functional capability.

A ball and beam tracking and balance control using magnetic suspension actuators

A new ball and beam system is constructed using a pair of magnetic suspension actuators in this paper. The proposed system can be used not only as a control theory verification and practice platform, but also as an educational demonstration and training tool for system integration of electrics, mechanics and cybernetics. The proposed control system activates two magnetic suspension actuators on either side of the beam. The magnetic force, as a function of position and coil current, was measured and modelled by a quadratic function. The system mathematical model is derived by the Lagrangian function. For control performance, a single chip microprocessor as control kernel with basic electronic components is designed and implemented. The ball and beam system hardware as well as microprocessor-based control circuit is implemented and tested. The static and dynamic performance of the ball and beam system is tested with several different scenarios. The system operation on oscillatory stabilization and sinusoidal tracking is verified with excellent operational characteristics.

Random vibration of multi-span Mindlin plate due to moving load

Abstract In this paper, the method of modal analysis is presented to study the random vibration of multi‐span Mindlin plates due to a load moving at a constant velocity. The moving load is considered to be a stationary process with a constant mean value and a variance. Four types of variances are considered in this study: white noise, exponential, exponential cosine, and cosine. The effect of both velocity and statistical characteristics of the load, and the effect of the span number of the multi‐span plate on the mean value, variance of deflection and moment of the structure are investigated. The results of the multi‐span Mindlin plate are compared with those of a multi‐span classical plate.

Dynamic analysis of a t-type timoshenko frame to a moving load using finite element method

Abstract The finite element technique is adopted for calculating the modal frequencies of a T‐type Timoshenko frame. The axially inertia effect of each branch is included. The ratio of the radius of gyration of a cross‐sectional area to length is defined as r. Both the effects of r and the element number of each branch on the relative error of the first modal frequency are studied. A concentrated load moving on the frame is treated as an example. The velocity effect of load on both maximum displacement and moment of the frame is also investigated. These results are compared with those of a Bernoulli‐Euler frame.

Effects of glenohumeral internal rotation deficit on baseball pitching among pitchers of different ages

BACKGROUND Previous studies have reported that glenohumeral internal rotation deficit (GIRD) may increase the risk of shoulder injury. However, the effects of GIRD on baseball pitching among pitchers of different age groups are still unclear. METHODS The study participants were 24 high school and 24 university pitchers. For each age group, the pitchers were evenly divided into a GIRD group and a normal group. The pitching motion of each participant was captured using a motion analysis system at a sampling frequency of 300 Hz. The kinematics and kinetics of the throwing shoulder and trunk were quantified, and statistical differences between the groups were examined by 2-sample t tests. RESULTS For both age groups, significant differences were observed in shoulder external rotations of the GIRD and normal groups. Compared with the university pitchers in the normal group, the university pitchers with GIRD exhibited a greater shoulder loading and did more internal rotation work in the acceleration phase. The high school pitchers with GIRD showed a larger trunk tilt and less trunk rotation than the university pitchers with GIRD. However, the university pitchers with GIRD exhibited a larger shoulder posterior force and horizontal adduction torque than the high school pitchers with GIRD. CONCLUSION Pitchers with GIRD do change their pitching motions, and the greater resulting shoulder joint loading predisposes them to a greater risk of shoulder injury, especially among university pitchers.

Out‐of‐plane vibration of a multi‐span Timoshenko curved beam due to a moving load including the warping inertia of the beam

Abstract The governing equations for the out‐of‐plane motion of a multi‐span Timoshenko curved beam are derived. The warping inertia and flexural moment of the cross‐section of the curved beam are included. An analytical method is presented to calculate the modal frequencies and their corresponding sets of mode shape functions for the out‐of‐plane motion of the curved beam. Further, the orthogonality of two sets of mode shape functions corresponding to any two distinct modal frequencies for the out‐of‐plane motion of the curved beam is derived. The basic characteristics of strain energy density of the curved beam due to a moving load are investigated.

Optimum design of dynamic absorber for a random-excited machine mounted on a platelike structure foundation

Abstract The optimum design of a dynamic absorber for a machine mounted on a floor system is presented. The floor is considered to be a platelike structure. The transfer function is derived in closed-form. Based on the band-limited white-noise excitation, the optimum tuning and damping ratios of the absorber are determined by minimising the variance of response of the machine. Since the variance cannot be calculated directly by integrating the transfer function over the band-limited frequency range, the steepest descent method is used for determining these optimum parameters by iteration. The same procedure can be extended to deal with the cases of other multi degrees-of-freedom systems. The effects of mass ratios (i.e. absorber/machine and machine/floor), primary damping, frequency ratio and the thickness of plate on the design parameters are examined. The results show that the values of optimum tuning are much different from those of the rigid foundation case. To have a small variance, it is better to keep the frequency ratio ω 1 (defined as the frequency of primary system divided by half of the lowest natural frequency of the floor) in the range 1 1 , and have the mass ratio μ and the primary damping ratio ζ 1 are both greater than 0.1.