Research On Modeling And Simulation Of Deformable Objects For Haptic Rendering In Virtual Environment

Through haptic device and computer-generated virtual environment, haptic rendering enables operators to touch, feel and operate virtual objects, which further improves the sense of realism and immersion of virtual reality system. Haptic rendering has a broad field of application, where virtual surgery simulation is an important one. In this thesis, research on deformable object modeling, model simulation and model validation are conducted.In haptic rendering, physical-based reality and real-time computation are two conflicting requirements of the system. After describing existing modeling methods for deformable objects and analyzing their advantages and disadvantages respectively, a cellular solids honeycomb structure based deformable model is presented. In this model, deformable object is constructed with honeycomb units, and the relationship between deformation and interacting force is developed with the standard beam theory of structural mechanics. The analytical expression of the relationship between deformation and force is used to physically simulate deformable objects. Based on FALCON haptic device and liver model, a haptic rendering prototype system is constructed. Simulation experiment verifies the real-time and realistic performance of the proposed method. Through tuning the parameters of elastic modulus, side length and inner angle of the honeycomb unit, various linear and non-linear deformation simulating can be achieved.To fulfill the requirements of parameter optimization and simulation verification for haptic rendering, a deformable model validating system is developed with a force measuring system and FALCON device. The force measurement system is designed with the CC2531SoC chip integrating2.4GHz wireless module, ADC module and USB interface, micro force sensor and signal conditioning and amplification module, etc. With force measuring of800Hz sampling rate,14-bit conversion resolution and wireless data transmission, and three-dimension position measuring with FALCON device, validating experiment is carried out to record the force and position data during the interaction between different tools and fresh porcine liver. The validating system and experiment data is of great value for optimizing and verifying haptic deformable models.Finally, the future research directions in this field is presented and discussed.