The Biomechanical Simulation Of Skiing Movement

With the increasingly fierce international competition, the effects of science and technology on competitive sports have become increasingly prominent. Domestic and foreign researchers have made a great deal of efforts on sports studies and have achieved fruitful results by sports biomechanical methods. Skiing is a highly skillful technical sport. Most of studies about skiing are based on experiments and a very few skiing models are presented. Furthermore, most of the models are too simple and unsuitable for different types of skiing movements. They cannot compute muscle force and so on. None article is for skiing pole. No software is for skiing simulation due to the complexity of skiing movement. Skiing sports achievements in China have been behind the international advanced level. The reasons are that the studies about skiing started late and lacked of research tools.Based on the factors influence skiing, this paper builds a biomechanical multibody skiing model and corresponding software. This study involves multibody system dynamics, sports biomechanics, robot dynamics and control, numerical optimization and so on. The main researches are:The second chapter of this paper builds and tests a multibody skiing model. The model includes: snow ground sub model, skier sub model, ski-snow sub model, air drag sub model. The snow is described by space surface. The skier is simplified as sixteen rigid bodies and connected by twenty-five joints. The human body inertial parameters are obtained by regression equations with body height and mass. The joint motions are approximated by functions. The outline of ski face and side view is described by one rectangle and seven arcs. The ski is discretized as small points but has only six rigid degrees of freedom. A three-element of penetration force, impact force and friction is used to compute the interactions between ski and snow. The pressure distribution function is used to approximate the effects of ski bending. The aerodynamic drag on skier segments is considered. At the end, the skiing model is used to simulate downhill, parallel turning, and aerials. The simulated results agree well with simple model, experimental movement.The third chapter mainly focuses on the disposal of skiing pole. Neglecting the contact process, the pole-snow is described by unilateral constraint of multibody system dynamics. The relationship of interstitial function and reaction for pole-snow is converted to linear complementary problem that is supplied for dynamics equations. A standard double poling process is simulated by the model at last. The fourth chapter introduces the famous Hill-type muscle model to the multibody skiing model for the sake of study muscle coordination rules. The muscle forces/neural excitation values are solved by a standard quadratic programming optimization problem, in which muscle force/neural excitation is taken as design variable, the minimal square sum of muscle force/neural excitation is objective function, the non-negative and upper limit muscle force/neural excitation is none-equality constraints, the sum of all muscle moment equaled to joint control torque as equality constraints. Therefore, the skiing model can be used to solve both macroscopical kinetic problems and microcosmic muscle force coordination rules. As applications, muscle force coordination rules for several basic skiing movements are computed.The fifth chapter presents three evaluation indexes for skiing movement. The indexes are energy evaluation index, turning evaluation index, and stability evaluation index. These indexes are used to discuss the effects of skier center of gravity position on snowplow turning, parallel turning, and arms swing on the take-off status of aerials.The sixth chapter mainly introduces the skiing movement simulative software and uses it to simulate different skiing techniques. The program includes both parts of pre-processing and post-processing. The pre-processing is for auto building skiing model, posture setting, integral solver. The post-processing is about output of skiing animation, kinematics, dynamics, energy, muscle force, and stability evaluation and so on. At the end, parallel downhill, snowplow downhill, snowplow turn, parallel turning, and aerial skiing are successfully simulated by the program.All the simulation results show that the skiing model and software can apply to a wide range of simulation: downhill, turning, poling, and aerials. Some skiing characteristics such as start-up, rotation, flying, and landing are shown. The computed kinematic, dynamic, biomechanical information are useful for the understanding and improvement of skiing technology. The software can explore new technologies and demonstrate the feasibility of innovative technology.This study is financed by the National Natural Science Foundation of China No.10472018 and 10721062. Preliminary exploration about skiing is carried out and hoped to be contributed to ski sports research and development.