Multi-Dimensional Force Sensor Design for Haptic Human-Computer Interaction

Haptic human-computer interaction (HapHCI) is interaction between a human and a computer with realistic sense of touch. Haptic interaction between human and computer involves solving challenging problems in mechanical design, sensor, actuator, computer graphics, physical-based modelling and rendering algorithm, human capabilities, and other areas. With the increasing applications of HapHCI in virtual reality, teleoperation, rehabilitation, tele-surgery, entertainment, etc, the importance of the sense of touch for human-computer interaction has been widely acknowledged [Gabriel 2006]. For example, in virtual surgery training system, the surgeon controls the surgical tools and characterizes virtual tissues as normal or abnormal through the sense of touch provided by the HapHCI device. Another example is HapHCI based rehabilitation system for post-stroke patient exercise. During active rehabilitation exercise process, it requires accurate damping force control, and during passive rehabilitation exercise process, relatively accurate traction force is necessary. HapHCI technique usually consists of three fundamental parts: force/tactile measuring, haptic modelling, and haptic display device. Haptic modelling as well as haptic display hardware has been discussed a lot and exploited for ten years particularly in the area of virtual reality. However, so far little attention has been paid to the design of multidimensional force sensor for HapHCI, and the existing commercial six degree-of-freedom (DOF) force sensors are designed mainly for industrial robot control, which are too expensive and often over designed for HapHCI in axis and in bandwidth. As an important component in the HapHCI system, multi-dimensional force sensor not only measures the human hand force/torque acted on the interactive hardware device, such as handcontroller, master-manipulator, joystick etc, as a command input the computer, but also provides force/torque information for close-loop control of precise haptic display. A number of multi-dimensional force sensors have been developed during the past decades, which are intended for use at the end effector of a robot to monitor assembly or machine force. Most of them are six axes force/torque sensors [Watson, Drake, 1975] [Lord Corporation, 1985] [Nakamura et al., 1987] [Kaneko, Nishihara, 1993] [Kim, 2001], which measure three axes forces Fx, Fy, Fz, and three axes torques Mx, My, Mz. And some of them