Research On Motion Generation And Control Techniques For Virtual Human

With the in-depth development of virtual reality technology and the increasing requirement for it, the modeling and simulation of virtual human in the virtual environment have attracted more and more attention, gradually forming a new hot research field.Virtual human, as the vivid expression of human's geometrical feature and behavior characteristic in computer generated space, is the essential topic for the research of human-fit virtual space and highly immersive virtual environment. It provides a new way for human when dealing with crucial problems, such as safety and healthiness, education and entertainment, product design, etc al.The motion generation and control techniques are one of the most significant aspects of virtual human technology. The representation of the virtual human's skeleton structure, the motion control of the limbs and trunk, and a series of related problems are systemically and deeply studied in the thesis. The main work and contributions are summarized as follows:1. A minimal human model is presented which can be widely used to express the virtual human's basic movement. After thorough study of the skeleton structure of human body, a simplified virtual human model with 16 joints & 39 degrees of freedom is presented in the thesis. This is based on reasonable simplification and assumption, and only those key joints and degrees of freedom which can mostly represent the low-frequency characteristic of human motion are kept. The simulation results show that our model could help to decrease the complexity of the research work, increase the real-time performance, and make it possible for studying the motion generation and control techniques on PC platform without much loss of fidelity.2. A skeleton modeling method based on multi-rigid-body system theory is proposed in the thesis. Firstly virtual human is abstracted as a multi-rigid-body system whose limbs and trunk are coupled with mechanical revolute joints. Then tree model and lower body array are introduced to represent the skeleton structure. Compared with traditional DH method, our model could naturally exhibit the complex branched characteristic of virtual human and could easily realized arbitrary resolution extension for the minimal human model.3. A motion trajectory constructing method based on Bezier spline curve is put forward. Bezier spline curve is adopted to form the motion track of the body center of mass and the foot of swing leg. Compared withtrigonometric function approximation algorithm, our method has stronger representation and interactive control capability for complex space curves. It is also much more intuitive for motion curve construction and adjustment than Hermite spline curve.4. A walking model for virtual human based on time-critical gradient projection method is presented. Unlike the traditional Jacobian matrix method, we first convert the inverse kinematics problem to a constraint nonlinear programming problem. Then by changing the programming time of every frame, local linearization of the nonlinear function and time-critical computing can be achieved simultaneously. The multi-solution and singularity problems can be avoided because there is no need to compute the pseudoinverse any longer. Compared with variable metric method and conjugate gradient method, our algorithm could assure linear convergence, and near real-time performance could be obtained on PC.5. A generalized walking model and the interactive control method are presented. In order to show the diversity of complex motion for virtual human, a generalized walking model is proposed. Then four different kinds of motion based on the walking model is described and realized by interactively controlling and adjusting the regular walking model. Compared with motion capture method, our method is simpler and cheaper. It also promotes the reusability of the waling model.