Research On System Stability For Haptic Rendering

Haptic rendering leads to a more realistic virtual reality system and it is a promisinghuman-computer interaction technology that has broad application prospects. The system stability is aprerequisite for the improvement of system performance for haptic rendering. In this thesis, researchon improving system stability through the force refresh rate, the control method of haptic system andthe influence of the human operator are carried out.The force refresh rate has a deep influence on stability of haptic rendering system. In this thesis，performance of the different loop control algorithm is analyzed and multi-thread based parallelcomputing algorithm through system time query is used to improve the system stability. The forcerefresh time in each thread is compared while using different number of threads. This thesis alsostudies the maximum achieve stiffness when using different number of thread. The experiment resultsshow that more threads could enlarge the maximum achieve stiffness.Improving control method is another important way to improve system stability. To reduce thetime delay in force computing, this thesis proposes a force-precomputed based haptic renderingmethod. By precomputing force in the former force refresh cycle, this method could reduce the errorcaused by force computing delay. A series of experiments are conducted and verifies the validity ofthe method. The experiment results show that the proposed method enlarges the maximum achievablestiffness of the virtual wall by nearly40%.The human operator is the key part of haptic rendering system and has an important impact onthe stability of the system. It is of great value to improve the system stability for haptic rendering bytuning the mechanical impedance of human arm. In this thesis the mechanical characteristics of thehuman operator is studied and detailed experiments are carried out to study the mechanical impedanceof human arm and its effects in increasing the stability of haptic rendering. The experiment resultshows that back ground force can obvious tune the mechanical impedance of human arm, especiallywhen parallel to the interference force, which leads to a more stable haptic sytem.This thesis studies the stability of haptic rendering system from different aspects and it is of greatsignificance for improving sytem performance and fidelity for haptic rendering.