Kinematic requirement of the multi-DOF haptic devices with passive actuators

Haptic interfaces are categorized as either active or passive depending on the nature of the force reflecting actuators. Active haptic interface uses active motors, to actively restrict his or her motion against virtual environments. Passive haptic interface, on the other hand, uses brakes or dampers that dissipate the energy from the system to make the system passive. Thus passive actuators may contribute to improve the stability of the haptic interface. However, they are hard to display virtual damping force or friction for even simple constraints such as circle or triangle. Thus, to apply passive actuators to multi-DOF haptic device, it requires design consideration of the mechanism. This paper provides a design guideline of multi-DOF haptic device comprising passive actuators through the mathematical description of its kinematic requirement. As a consequence of analysis, the damping display is possible if and only if multi-DOF haptic device comprising only passive actuators has its orthogonal kinematic configuration over all workspace such as Cartesian manipulators. Case study is illustrated via a kinematically coupled 5 bar linkage mechanism.