An Improved Haptic Interface for Virtual Assembly Operations

Heavy computational load and the contradiction between workspace dimension and position resolution are some of the main problems in haptically enabled virtual assembly systems based on PHANToMreg and OpenHapticsreg toolkit. According to the characteristics of a virtual assembly system, two problems are analyzed, and their respective solution methods are proposed. In the computational load optimization method based on collision detection, the oriented bounding box (OBB) of the point-based haptic proxy is constructed dynamically according to the principle of the proxy´s motion law, and the improved OBB collision detection method is used to prune the triangles far away from the proxy. Only triangles, which are close to the current position of the proxy, are put into the haptic rendering list for the next graphics frame. All the above-mentioned tasks are completed in the graphics thread. A variable parameter workspace mapping method is also presented to solve the contradiction between the workspace dimension and the position resolution. This method includes two phases. In the first phase, the proxy position is obtained using the workspace mapping method provided by the OpenHaptics toolkit, and in the second phase, the position of the proxy is relocated according to the vertical distance from the proxy to the viewpoint. This method makes full use of the PHANToM workspace. It can provide the proxy with a higher position resolution when the proxy lies near to the viewpoint, and a large motion scope when the proxy is far away from the viewpoint. Experiments have shown that the presented methods are effective and useful for a haptic-based virtual assembly system.