A Dynamics and Stability Framework for Avian Jumping Take-off

Jumping take-off in birds is an explosive behaviour with the goal of providing a rapid transition from ground to airborne locomotion. An effective jump is predicated on the need to maintain dynamic stability through the acceleration phase. The present study concerns understanding how birds retain control of body attitude and trajectory during take-off. Cursory observation suggests that stability is achieved with relatively little cost. However, analysis of the problem shows that the stability margins during jumping are actually very small and that stability considerations play a significant role in selection of appropriate jumping kinematics. We use theoretical models to understand stability in prehensile take-off (from a perch) and also in non-prehensile take-off (from the ground). The primary instability is tipping, defined as rotation of the centre of gravity about the ground contact point. Tipping occurs when the centre of pressure falls outside the functional foot. A contribution of the paper is the development of graphical tipping stability margins for both centre of gravity location and acceleration angle. We show that the nose-up angular acceleration extends stability bounds forward and is hence helpful in achieving shallow take-offs. The stability margins are used to interrogate simulated take-offs of real birds using published experimental kinematic data from a guinea fowl (ground take-off) and a diamond dove (perch take-off). For the guinea fowl the initial part of the jump is stable, however simulations exhibit a stuttering instability not observed experimentally that is probably due to absence of compliance in the idealised joints. The diamond dove model confirms that the foot provides an active torque reaction during take-off, extending the range of stable jump angles by around 45{\deg}.Comment: 21 pages, 11 figures; supplementary material: https://figshare.com/s/86b12868d64828db0d5d; DOI: 10.6084/m9.figshare.721056

CAN FORWARD DYNAMIC SIMULATION MODELS BE USED TO IMPROVE THE PERFORMANCE OF TOP ATHLETES?

The question addressed in this study was whether the forward simulation approach can be used to improve the performance of top athletes. Using a musculoskeletal model we carried out a simulation experiment on vertical squat jumping, which involved (1) generation of target kinematics, (2) production of matching simulations with two different models, (3) finding optimal solutions for the two models and (4) implementation of optimal solutions. It was shown that the approach was only successful if the model used to match the target kinematics accurately represented the system that had generated these target kinematics. Since it is not possible to make accurate models of the musculoskeletal system of individual athletes, the goal of improving the performance of top athletes with a forward dynamic simulation approach seems too ambitious

Optimisation of performance in the triple jump using computer simulation

While experimental studies can provide information on what athletes are doing, they are not suited to determining what they should be doing in order to improve their performance. The aim of this study was to develop a realistic computer simulation model of triple jumping in order to investigate optimum technique. A 13-segment subject-specific torque-driven computer simulation model of triple jumping was developed, with wobbling masses within the shank, thigh, and torso. Torque generators were situated at each hip, shoulder, knee, ankle, and ball joint. Kinetic and kinematic data were collected from a triple jump using a force plate and a Vicon motion analysis system. Strength characteristics were measured using an isovelocity dynamometer from which torque-angle and torque-angular velocity relationships were calculated. Segmental inertia parameters were calculated from anthropometric measurements. Viscoelastic parameters were obtained by matching an angle-driven model to performance data for each phase, and a common set for the three contact phases was determined. The torque-driven model was matched to performance data for each phase individually by varying torque generator activation timings using a genetic algorithm. The matching produced a close agreement between simulation and performance, with differences of 3.8%, 2.7%, and 3.1% for the hop, step, and jump phases respectively. The model showed good correspondence with performance data, demonstrating sufficient complexity for subsequent optimisation of performance. Each phase was optimised for jump distance with penalties for excessive angular momentum at take-off. Optimisation of each phase produced an increase in jump distance from the matched simulations of 3.3%, 11.1%, and 8.2% for the hop, step, and jump respectively. The optimised technique showed a symmetrical shoulder flexion consistent with that employed by elite performers. The effects of increasing strength and neglecting angular momentum constraints were then investigated. Increasing strength was shown to improve performance, and angular momentum constraints were proven to be necessary in order to reproduce realistic performances

Moving Motion Control System On Developed Tripod Hopping Robot

This paper discussed on evaluation and validation of method in order to generate the moving motion control system of the developed tripod hopping robot. The proposed method to control the system is designed by using MATLAB&Simulink which consist of reference height control system and the networks of Central Pattern Generator (CPG) that can controlled the hopping height of each leg independently. By using this method, one of the legs of the tripod hopping robot is set to different value than the other leg in order to make the posture of hopping robot’s body incline ahead towards to the direction which it should move, respectively. As the result, the effectiveness of the approached method to generate moving motion of the hopping robot using CPG networks that including the reference height control system is confirmed while maintain the stability of developed tripod hopping robot from tumbled ahead

BIOMECHANICAL DIFFERENCES OF TWO COMMON FOOTBALL MOVEMENT TASKS IN STUDDED AND NON-STUDDED SHOE CONDITIONS ON INFILLED SYNTHETIC TURF

The purpose of this study was to examine kinematic and kinetic differences in three shoe conditions (traditional football shoes with natural and synthetic turf studs and a neutral running shoe) during two common football movements (a 180° cut and a land-cut movement) on infilled synthetic turf. Fourteen recreational male football players performed five trials in all three shoe conditions for a 180° cut as well as a land-cut maneuver. The kinematic and kinetic variables were analyzed with a 3 x 2 (shoe x movement) repeated measures analysis of variance (ANOVA, p\u3c0.05). Peak free moment was significantly greater for the land-cut trials (p\u3c0.001). Vertical GRFs were significantly greater for the land-cut trials (p\u3c0.001). A cleat x movement interaction was seen for time to vertical impact GRF (p=0.048). A cleat main effect was found for time to vertical impact between natural turf cleat and synthetic turf cleat (p=0.019). Vertical loading rate was significantly greater in land-cut trials. Peak medial GRFs showed a significant cleat x movement interaction (p=0.002). The results from this study suggest that land-cut movement elicit greater vertical GRF and vertical impact loadings rates. The running shoe had significantly less dorsiflexion range of motion (ROM) than the synthetic turf studs. A significant cleat main effect was found for peak eversion velocity (p=0.005). Post hoc comparisons showed that it was significantly smaller in shoe than that natural turf stud (p=0.016) and synthetic turf stud (p=0.002). In general, there was a lack of differences between the shoe conditions for GRFs and kinematic variables. For the 180° cut movement, natural turf studs produced lowest peak medial GRF compared to the synthetic turf studs and the shoe. The results from this study suggest that land-cut movement elicit greater vertical GRF and vertical impact loadings rates. In general, there was a lack of differences of GRFs and kinematic variables between the shoe conditions. For the 180° cut movement, natural turf studs produced lowest peak medial GRF compared to the synthetic turf studs and the shoe. Overall, increased GRFs, especially in combination with rapid change of direction and deceleration may increase the chance of injury