Dynamics identification and implementation for enhanced haptic display

Abstract

This thesis introduces a new approach for dynamics identification and implements the identified models for enhanced haptic display. The thesis also derives an adaptive virtual coupling design approach for improving the control performance in haptic displays. Realistic dynamics models are important for haptic display for Virtual Reality systems. Such dynamic models are desirably obtained via experimental identifications. However, traditional dynamics identification methods normally require large sized training data sets, which maybe difficult to meet in many practical applications. To obtain reality based models, we present in this thesis an identification method using Support Vector Machines (SVM) regression algorithm that is more effective than traditional methods for sparse training data. This method has not been previously studied experimentally in the dynamics identification literature. SVM can be used as a generic learning machine or as a special learning technique that can make full use of the available knowledge about the dynamics structure. This distinguishes our approach from the work in the literature on dynamics modeling. Using the identified dynamics model in a virtual environment, the operator can experience a more realistic operating feel. Another issue for high performance haptic display is the nonlinear joint friction phenomenon of mechanical haptic interface that affects accurate haptic control. To reduce these effects as much as possible, a new strategy: ESVM (Extended SVM) based friction model identification method is derived according to the characteristics of the friction function. It is experimentally demonstrated that the ESVM can achieve satisfactory friction compensation for enhanced haptic display. Conventional virtual coupling is designed mainly for stabilizing the virtual environment (VE) and usually has poor performance. This thesis proposes a novel adaptive virtual coupling design approach. According to the performance errors, the virtual coupling can be adaptively tuned through a fuzzy logic based law. The designed haptic controller can improve the "operating feel" in a virtual environment, while the system's stability condition can be satisfied. Both simulation and experimental results demonstrate the effectiveness of this novel virtual coupling design approach. Finally, some haptic display experiments are conducted. The identified friction models are incorporated into the corresponding virtual environments. The enhanced operator’s feel via the haptic display is shown through the experimental verification.

Date of Award	15 Jul 2004
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	You Fu LI (Supervisor)