Pitch Mechanism Research Articles

Complex pitch perception mechanisms are shared by humans and a New World monkey

The perception of the pitch of harmonic complex sounds is a crucial function of human audition, especially in music and speech processing. Whether the underlying mechanisms of pitch perception are unique to humans, however, is unknown. Based on estimates of frequency resolution at the level of the auditory periphery, psychoacoustic studies in humans have revealed several primary features of central pitch mechanisms. It has been shown that (i) pitch strength of a harmonic tone is dominated by resolved harmonics; (ii) pitch of resolved harmonics is sensitive to the quality of spectral harmonicity; and (iii) pitch of unresolved harmonics is sensitive to the salience of temporal envelope cues. Here we show, for a standard musical tuning fundamental frequency of 440 Hz, that the common marmoset (Callithrix jacchus), a New World monkey with a hearing range similar to that of humans, exhibits all of the primary features of central pitch mechanisms demonstrated in humans. Thus, marmosets and humans may share similar pitch perception mechanisms, suggesting that these mechanisms may have emerged early in primate evolution.

Fluid–structure interaction analysis of a morphing vertical axis wind turbine

There has been much recent interest in the development of Vertical Axis Wind Turbines (VAWTs), especially for use in off-grid or off-shore electricity generation, due to inherent advantages over the more popular horizontal axis types. Although there have been a number of recent attempts to increase efficiency of VAWTs using active and passive blade pitch control strategies, these designs come at an increased upfront cost, detracting from the simplistic allure of the VAWT design. This study investigates the feasibility of a flexible bladed (or morphing) VAWT, wherein individual blades are able to passively adapt to local flow conditions and serve as a pitch control mechanism to increase rotor efficiency. Using a finite volume fluid–structure interaction algorithm, a rigid VAWT is simulated with good agreement with existing experimental data, then compared to several other geometrically identical morphing designs with varying material flexibility. All simulated flexible rotors achieved higher efficiency than the standard (rigid) one, with efficiency gains up to 9.6% for the VAWT geometry investigated herein. The results suggest that the morphing rotor design can have significant advantages over the rigid design particularly in part-load scenarios, and is also likely to increase the self-starting abilities of the VAWT.

The Performance of Controlling Cannon Barrel Position on the Moving Platform Using Neural Network Control and Sliding Mode Control

One of the gunboat weapons that need to stay stable is the cannon. Its unbalance position that caused by pitch and roll disturbance will influence the target accuracy, target detection, tracking system, object identification and the ability to counter the threat. In order to determine this disturbance, the balancing control on the movement platform can be solved by using neural network control and sliding mode control methods. To make an approach, the cannon movement system can be modeled in training and elevation movements and the disturbances are modeled through pitch and roll mechanisms. The variations in obtained parameters of training and elevation (moment of inertia) are the non-linearity result of the moving cannon. The system is simulated to verify the error in the controller's output processed using the neural network coordination system control and sliding mode control. The learning process in the neural network is made using back propagation method in order to get the weight value at the different disturbances which their results are given in the simulation of coordination models. On the other hand, the free chattering of sliding mode control is implemented in order to make the movement of training and elevation can be controlled for having the desired angle position in the disturbance of pitch and roll. This paper is based on the study to compare the performance of neural network control and sliding mode control on the moving platform.

Reliability of an electromagnetic tracking system in describing pitching mechanics

AbstractThe availability of various motion capture systems provides researchers and clinicians options in collecting kinematic data. However, with electromagnetic tracking systems, it is imperative to determine the reliability of the system with regard to the specific movement of interest to ensure the collection of data that are reliable, interpretable and may be generalized to a broad spectrum of individuals. Thus, the purpose of this study was to establish the reliability of an electromagnetic tracking device (ETD) in analyzing young baseball pitchers. Two data collection sessions in which throwing kinematics were recorded were conducted across a five-day span. Joint kinematics were calculated using the standards and conventions recommended by the International Shoulder Group. Correlation analyses examining inter-day reliability of the ETD showed that the system was within acceptable limits (R > .73). Throughout the selected instances of the pitch cycle, the ETD used in the current study was shown to b...

A Robust Fuzzy-PI Pitch Angle Controller for Wind Turbine Systems

This paper presents a robust Fuzzy-PI controller to adjust the pitch angle of a grid integrated wind turbine. The pitch angle mechanism of a turbine blade allows it rotate on its own axis so that it can protect itself from high wind gust and release excessive stress from the mechanical structure. Although a classical PI controller has been widely used for this purpose, they cannot assure generator stability. The proposed Fuzzy-PI control system uses three control inputs and nine membership functions to make decision on pitch angle output. A wind speed model is devised to simulate real life turbulent wind condition. The simulation results show that the Fuzzy-PI controller is more suitable for turbine operation if it is subjected to heavy turbulence.

Factors related to injury in youth and adolescent baseball pitching, with an eye toward prevention.

The baseball and medical communities have recognized injuries of the upper extremity associated with the overhead throwing motion and have examined manners in which to reduce risk. The authors examine special features of the adolescent pitcher as compared with skeletally mature pitchers and characteristics of pitch mechanics, type, velocity, fatigue, and overuse. A summary is presented on previously identified risk factors as they relate to pitching injuries. Development, use, and compliance with the most current pitching guidelines in youth baseball, based on the available evidence, will be presented and examined. In an increasingly competitive environment, identifying known risk factors and potential signs of pathology as well as implementing the current best evidence in a consistent manner are important steps in decreasing injury risk of youth baseball pitchers. More research is needed to evaluate the effectiveness of pitching guidelines in the short and long term and to focus on manners in which to increase compliance with best practice procedures throughout youth baseball organizations.

Lateral Trunk Lean in Pitchers Affects Both Ball Velocity and Upper Extremity Joint Moments

Background: The incidence of upper extremity injuries in baseball pitchers is increasing. Over the past decade there has been a great deal of research attempting to elucidate the cause of these injuries, focusing mainly on the mechanics of the pitching arm with no examination of other key segments, such as the trunk. This is surprising, as coaches will often comment on trunk position in an effort to improve pitching outcomes. Purpose: To determine the association between contralateral trunk lean and ball velocity and the moments about the elbow and glenohumeral joint. Study Design: Descriptive laboratory study. Methods: A total of 99 pitchers were recruited for this study and underwent a pitching analysis using 3-dimensional motion analysis techniques. A random intercept mixed-effects regression model was used to determine if statistically significant associations existed between contralateral trunk lean (away from the pitching arm side) and ball velocity, as well as the elbow varus moment and glenohumeral internal rotation moment. Results: The results demonstrated that the greatest contralateral trunk lean occurs around the time of the peak elbow varus moment. Statistically significant associations were found between contralateral trunk lean and increased ball velocity (P = .003) indicating that for every 10° increase in contralateral lean, ball velocity increased 0.5 m/s. Results also indicated that for every 10° increase in contralateral lean, elbow varus moments increased by 3.7 N·m and glenohumeral internal rotation moments increased by 2.5 N·m (P < .001 for both). Conclusion: Study findings indicate that the positioning of the trunk plays a substantial role in pitching performance and pitcher injury potential. This work helps to demonstrate the importance of proper trunk mechanics in pitching and highlights the need for future research to understand the contribution of the trunk to pitching mechanics. Clinical Relevance: Pitching coaches and trainers can use the results of this study to stress the importance of proper trunk mechanics in pitching. Specifically, improving core strength and trunk control in an effort to maintain a more upright posture through the pitching cycle can reduce upper extremity joint stresses.

Correlation of Shoulder and Elbow Kinetics With Ball Velocity in Collegiate Baseball Pitchers.

Throwing a baseball is a dynamic and violent act that places large magnitudes of stress on the shoulder and elbow. Specific injuries at the elbow and glenohumeral joints have been linked to several kinetic variables throughout the throwing motion. However, very little research has directly examined the relationship between these kinetic variables and ball velocity. To examine the correlation of peak ball velocity with elbow-valgus torque, shoulder external-rotation torque, and shoulder-distraction force in a group of collegiate baseball pitchers. Cross-sectional study. Motion-analysis laboratory. Sixty-seven asymptomatic National Collegiate Athletic Association Division I baseball pitchers (age = 19.5 ± 1.2 years, height = 186.2 ± 5.7 cm, mass = 86.7 ± 7.0 kg; 48 right handed, 19 left handed). We measured peak ball velocity using a radar gun and shoulder and elbow kinetics of the throwing arm using 8 electronically synchronized, high-speed digital cameras. We placed 26 reflective markers on anatomical landmarks of each participant to track 3-dimensional coordinate data. The average data from the 3 highest-velocity fastballs thrown for strikes were used for data analysis. We calculated a Pearson correlation coefficient to determine the associations between ball velocity and peak elbow-valgus torque, shoulder-distraction force, and shoulder external-rotation torque (P < .05). A weak positive correlation was found between ball velocity and shoulder-distraction force (r = 0.257; 95% confidence interval [CI] = 0.02, 0.47; r(2) = 0.066; P = .018). However, no significant correlations were noted between ball velocity and elbow-valgus torque (r = 0.199; 95% CI = -0.043, 0.419; r(2) = 0.040; P = .053) or shoulder external-rotation torque (r = 0.097; 95% CI = -0.147, 0.329; r(2) = 0.009; P = .217). Although a weak positive correlation was present between ball velocity and shoulder-distraction force, no significant association was seen between ball velocity and elbow-valgus torque or shoulder external-rotation torque. Therefore, other factors, such as improper pitching mechanics, may contribute more to increases in joint kinetics than peak ball velocity.

Absolute Pitch: Evidence for Early Cognitive Facilitation during Passive Listening as Revealed by Reduced P3a Amplitudes

Absolute pitch (AP) is the rare ability to identify or produce different pitches without using reference tones. At least two sequential processing stages are assumed to contribute to this phenomenon. The first recruits a pitch memory mechanism at an early stage of auditory processing, whereas the second is driven by a later cognitive mechanism (pitch labeling). Several investigations have used active tasks, but it is unclear how these two mechanisms contribute to AP during passive listening. The present work investigated the temporal dynamics of tone processing in AP and non-AP (NAP) participants by using EEG. We applied a passive oddball paradigm with between- and within-tone category manipulations and analyzed the MMN reflecting the early stage of auditory processing and the P3a response reflecting the later cognitive mechanism during the second processing stage. Results did not reveal between-group differences in MMN waveforms. By contrast, the P3a response was specifically associated with AP and sensitive to the processing of different pitch types. Specifically, AP participants exhibited smaller P3a amplitudes, especially in between-tone category conditions, and P3a responses correlated significantly with the age of commencement of musical training, suggesting an influence of early musical exposure on AP. Our results reinforce the current opinion that the representation of pitches at the processing level of the auditory-related cortex is comparable among AP and NAP participants, whereas the later processing stage is critical for AP. Results are interpreted as reflecting cognitive facilitation in AP participants, possibly driven by the availability of multiple codes for tones.

Failure of an Aero Engine Ball Bearing Due to Axial Loading

During a flight of an aircraft, the rpm of one engine dropped to 96% with frequency 390 cycles per second (CPS). The pilot tried to stabilize the rpm of the engine using standard procedures but failed and soon the rpm further dropped to 95%. The engine was switched off and a safe landing was made with remaining three engines. During initial investigation, cage of one of the rear bearing of governor in the valve housing was found broken, whereas second bearing of this set was found unserviceable due to abnormal play. Valve housing was a part of propeller control assembly. It controls flow of pressurized hydraulic fluid toward pitch changing mechanism in the dome assembly through cams, valves, and switches, to change the propeller blades angle. The ball bearing under consideration was supposed to run for indefinitely long period it was to be replaced mandatorily during overhaul of the valve housing after 6000 h of its life. In this particular case, failed ball bearing had consumed only 1938.4 h. The failure analysis of the bearing was carried out, and the factors found to be contributing in the failure of bearing were (a) Improper mounting and/or excessive axial load, (b) Entrapment of the foreign particles leading to wear and stresses at localized regions, (c) Contact fatigue under excessive axial loads leading to formation of spalling; the formation of debris during spalling might also enhance the wear.

Simulation and study of power quality issues in a fixed speed wind farm substation.

Power quality issues associated with the fixed speed wind farm substation located at Coimbatore district are investigated as the wind generators are tripping frequently. The investigations are carried out using two power quality analyzers, Fluke 435 and Dranetz PX5.8, with one of them connected at group control breaker of the 110 kV feeder and the other at the selected 0.69 kV generator busbar during the period of maximum power generation. From the analysis of the recorded data it is found that sag, swell, and transients are the major events which are responsible for the tripping of the generators. In the present study, simulation models for wind, turbine, shaft, pitch mechanism, induction generator, and grid are developed using DIgSILENT. Using the turbine characteristics, a two-dimensional lookup table is designed to generate a reference pitch angle necessary to simulate the power curve of the passive stall controlled wind turbine. Various scenarios and their effects on the performance of the wind farm are studied and validated with the recorded data and waveforms. The simulation model will be useful for the designers for planning and development of the wind farm before implementation.

Significant variations in Weber fraction for changes in inter-onset interval of a click train over the range of intervals between 5 and 300 ms.

It is a common psychophysical experience that a train of clicks faster than ca. 30/s is heard as one steady sound, whereas temporal patterns occurring on a slower time scale are perceptually resolved as individual auditory events. This phenomenon suggests the existence of two different neural mechanisms for processing of auditory sequences with fast and slow repetition rates. To test this hypothesis we used Weber’s law, which is known to be valid for perception of time intervals. Discrimination thresholds and Weber fractions (WFs) for 12 base inter-click intervals (ICIs) between 5 and 300 ms were measured from 10 normal hearing subjects by using an “up–down staircase” algorithm. The mean WF, which is supposed to be constant for any perceptual mechanism according to Weber’s law, displayed significant variation with click rate. WFs decreased sharply from an average value of around 5% at repetition rates below 20 Hz to about 0.5% at rates above 67 Hz. Parallel to this steep transition, subjects reported that at rates below 20 Hz they perceived periodicity as a fast tapping rhythm, whereas at rates above 50 Hz the perceived quality was a pitch. Such a dramatic change in WF indicated the existence of two separate mechanisms for processing the click rate for long and short ICIs, based on temporal and spectral features, respectively. A range of rates between 20 and 33 Hz, in which the rate discrimination threshold was maximum, appears to be a region where both of the presumed time and pitch mechanisms are relatively insensitive to rate alterations. Based on this finding, we speculate that the interval-based perception mechanism ceases to function at around 20 Hz and the spectrum-based mechanism takes over at around 33 Hz; leaving a transitional gap in between, where neither of the two mechanisms is as sensitive. Another notable finding was a significant drop in WF for ICI = 100 ms, suggesting a connection of time perception to the electroencephalography alpha rhythm.

Pitch and Roll Control Mechanism for a Hovering Flapping Wing MAV

Hovering flapping flight is inherently unstable and needs to be stabilized actively. We present a control mechanism that modulates independently the wing flapping amplitude and offset by displacing joints of a flapping linkage mechanism. We demonstrate its performance by high speed camera recordings of the wing motion as well as by direct measurements of pitch moment and lift force. While flapping at 17 Hz the prototype produces 90 mN of lift and generates pitch moments from −0.7 N.mm to 1.1 N.mm. The mechanism shows low level of cross-coupling in combined pitch and roll commands.

The physics of musical instruments with performance illustrations and a concert

Musical Instruments generally rely on the following elements for tone production: a power supply, an oscillator, a resonator, an amplifier, and a pitch control mechanism. The physical basis of these elements will be discussed for each instrument family with performance illustrations by the orchestra. Wave shapes and spectra will be shown for representative instruments. A pamphlet illustrating important elements for each instrument group will be distributed to the audience. The Science presentation with orchestral performance illustrations will be followed by a concert of the New World Youth Symphony Orchestra. This orchestra is one of three performing groups of the New World Youth Orchestras, an organization founded by Susan Kitterman in 1982. Members of the Symphony are chosen from the greater Indianapolis and Central Indiana area by audition.

A vertical axis hydrodynamic turbine with flexible foils, passive pitching, and low tip speed ratio achieves near constant RPM

A full-scale vertical axis turbine with flexible foil blades and a passive spring-loaded pitching mechanism was tested in the Glomma River in Norway, demonstrating a maximum turbine efficiency of 37% (0.79 m/s, 3.7 RPM), 25% (1.18 m/s, 4.2 RPM), and 20% (1.55 m/s, 4.7 RPM). The turbine rotational speed showed a limited revolutions per minute (RPM) variation (increasing by only a factor of 1.3) with a doubling of inflow speed. The turbine RPM and load variations were controlled using five wings, double-cambered morphing blades with a relatively high blade lift/drag ratio over a wide range of angle of attacks, and passive spring-controlled blade pitching. The inherent passive blade pitching demonstrated a distinct flopping motion around the nominal (non-pitched) position at ∼0° azimuth angle and a less distinct motion at ∼180° for each revolution around the axis. The turbine's high solidity design, morphing blades, and Knoller-Betz effect limited the RPM variations over a wide range of water velocities. The flex foil turbine had higher power coefficients at lower tip speed ratios compared to typical lower solidity turbines with fixed blades, higher tip speed ratios, and no blade pitching and/or flopping.

Evaluation of wrist and forearm motion in college-aged baseball pitchers

Current pitching literature focuses primarily on the elbow and glenohumeral joints. This has led to a paucity of information regarding the forearm and wrist, and the limited data available are inconsistent. Therefore, this article seeks to provide a comprehensive description of the kinematics and kinetics of the wrist and forearm for the fastball, curveball, slider/cutter, and change-up for college-level baseball pitchers. Thirty-six collegiate pitchers were evaluated using motion analysis techniques. Results indicated that pitching the curveball generated the greatest forearm supination (16 ± 13°) compared with the other three pitch types (p < 0.05). The curveball and slider/cutter were pitched with less wrist extension and greater ulnar deviation compared with the fastball and change-up. The curveball was found to produce the greatest ulnar moment (7.3 ± 2.2 Nm) and was significantly different from the moments noted when pitching the fastball and change-up (5.1 ± 1.9 and 4.9 ± 1.9 Nm, respectively; p < 0.05). These results indicate that it may be possible to objectively determine pitch type from kinematic data of the wrist and forearm. It may also be possible that coaches may be able to identify abnormal pitching mechanics from more proximal segments by understanding the motion of the wrist.

Experimental research on tidal current vertical axis turbine with variable-pitch blades

Due to the limited storage and ever-increasing dependence on fossil fuel, the world is in the phase of shifting toward renewable energy. Tidal current energy is one of the most predictable forms of renewable energy, which is harnessed by utilizing a tidal current turbine. To study the performance of the tidal current turbine relating to the ability of energy absorption and exchanging, experimental tests play an important role which can not only validate the numerical results but also provide a reference for the prototype design. In this study, a series of experiments related to vertical-axis turbines (VAT) were carried out at Harbin Engineering University and a large quantity of experimental data to study the hydrodynamic performance of turbines was presented. Based on the different techniques used to control the pitch mechanism, the experiments can be classified as the cycloid type controllable-pitch, spring-control pitch and passive variable-pitch VAT experiment. The influences of the different parameters on the hydrodynamic performance of turbines were discussed. Finally, some control strategies for the blade for different turbines were given.

Research and Design of a Novel Pitch Mechanism for Supersonic Wind Tunnel

Developing the high attack angle mechanism with good dynamic characteristics is among the key technologies for researching the advanced and highly flexible aircraft weapons. The main test device of the high attack angle mechanism is the pitch mechanism. The pitch mechanism with good dynamic and static characteristics is the key to successful wind tunnel tests. According to the design requirements of the high angle of attack in supersonic tunnel, a new structure and a new working principle of the pitch mechanism are put forward based on the study of the oversea and domestic pitch mechanism. And the error analysis of the pitch mechanism is completed by way of total differentiation method. As a result, the machining accuracy of components is determined after comprehensive analysis. According to the structure and characteristics of the new pitch mechanism in supersonic wind tunnel, the static structure strength and stiffness have been analyzed by using ANSYS system, and so does modal analysis. Computation results show that the pitch mechanism has agreed well with the agreements of the supersonic wind tunnel, and it proves that the structure form of the pitch mechanism is reasonable and reliable.

Overview and Design of self-acting pitch control mechanism for vertical axis wind turbine using multi body simulation approach

Awareness about wind energy is constantly growing in the world. Especially a demand for small scale wind turbine is increasing and various products are available in market. There are mainly two types of wind turbines, horizontal axis wind turbine and vertical axis wind turbines. Horizontal axis wind turbines are suitable for high wind speed whereas vertical axis wind turbines operate relatively low wind speed area. Vertical axis wind turbines are cost effective and simple in construction as compared to the horizontal axis wind turbine. However, vertical axis wind turbines have inherent problem of self-start inability and has low power coefficient as compare to the horizontal axis wind turbine. These two problems can be eliminated by incorporating the blade pitching mechanism. So, in this paper overview of various pitch control systems is discussed and design of self-acting pitch mechanism is given. A pitch control linkage mechanism for vertical axis wind turbine is modeled by multi-body approach using MSC Software. Aerodynamic loads are predicted from a mathematical model based on double multiple stream tube method. An appropriate airfoil which works at low Reynolds number is selected for blade design. It is also focused on commercialization of the vertical axis wind turbine which incorporates the self-acting pitch control system. These aerodynamic load model will be coupled with the multi-body model in future work for optimization of the pitch control linkage mechanism. A 500 Watt vertical axis wind turbine is designed and it is planned to implement the self-acting pitch control mechanism in real model.

Relationship Between Tightness of the Hip Joint and Elbow Pain in Adolescent Baseball Players.

Background:Repetitive tensile stresses from valgus torque can induce elbow injury in adolescent baseball players. Insufficient hip range of motion (ROM) can change throwing mechanics, reducing the transfer of energy from the lower to the upper extremities. Thus, hip ROM limitations may force the upper extremities to bear the burden of a strong throw. Improper pitching mechanics caused by insufficient hip ROM are thought to increase valgus torque on the elbow when throwing, increasing the risk of elbow injury.Purpose:To investigate the relationship between elbow pain and hip ROM in adolescent baseball players.Study Design:Cross-sectional study; Level of evidence, 3.Methods:A total of 122 adolescent baseball players with a mean age of 12.0 years (range, 6-14 years) participated in this study. Elbow pain, hip flexion angle, and the internal rotation angles of the hip at 0° and 90° of flexion were assessed. Participants were divided into a pain group and a normal group based on the pain assessment, and each hip angle was compared between groups using Student t tests. P values <.05 were considered statistically significant.Results:Thirty-one of 122 players had elbow pain. The hip flexion angle of the trail leg was 121.9° ± 12.3° for the normal group and 111.2° ± 11.3° for the pain group (P = .0001). The plant leg hip flexion angles were 122.0° ± 12.4° and 113.6° ± 11.3° (P = .0014) for the normal and pain groups, respectively. The internal rotation angle at 0° of hip flexion of the trail leg was 49.4° ± 12.6° and 45.6° ± 8.8° (not significant), and of the plant leg was 49.1° ± 12.5° and 48.7° ± 11.5° (not significant), for the normal and pain groups, respectively. The internal rotation of the trail leg at 90° of hip flexion was 46.9° ± 13.3° in the normal group and 36.1° ± 15.7° in the pain group (P = .0005). In the plant leg, the internal rotation angle at 90° of hip flexion was 46.9° ± 12.2° and 36.4° ± 18.1° for the normal and pain groups, respectively (P = .0013).Conclusion:Limitations to hip flexion and internal rotation at 90° of hip flexion were risk factors for elbow injury. Differences in internal rotation angles between 0° and 90° of hip flexion may be important criteria for identifying adolescent baseball players at risk of elbow pain.