Contents 1. Introduction
Force feedback interfaces are humane-machine interaction systems that provide the kinesthetic or tactile information of the environments to the human operator by manipulating them. The environments are classified into two types in according to theirs applications. In teleoperation applications, they are real environments directly contacting the slave robot. In haptic applications, they are virtual environments realized by the computer. This paper primarily focuses on haptic interfaces for virtual reality. Haptic interface lets the user touch, feel and manipulate virtual environments. Generally, haptic interface consists of a real-time simulation of a virtual environment and a mechanical device, which serves as the interface between the human operator and the simulation (Fig. 1). Based on information from various sensors, the simulation calculates forces to output with the actuators. Without actuators, the interface can only function as an input device to the computer. These forces are felt by the operator through the actuators, making it seem to the operator as if he/she is actually interacting with the virtual environment.
