Haptic Master is Desktop Force Display
Force sensation plays important roles in the recognition of virtual objects. In this display,users can feel the rigidity or weight of virtual objects with a compact force-feedback device(force display) for desktop use.
A six-degree-of-freedom manipulator employs a parallel mechanism to apply reaction forces to the fingers of the operator.The manipulator's handle is supported with three sets of pantographs.
Most of robotic manipulators have large-scale and high-cost hardware,which inhibits their application to human-computer interaction.This innovative force-feedback device was specifically developed for desktop use. It provides haptic and force feedback,which strongly enhances human capabilities in the major application areas of virtual reality,such as scientific visualization and 3D shape modeling.

The basis of the force display is a six-degree-of-freedom manipulator that employs a parallel mechanism.The typical design feature of parallel manipulators is an octahedron called "Stewart Platform",in which a top triangular platform are connected by six length-controllable cylinders.This hardware design is compact,and it has the ability to carry a relatively large payload.but the structure has some practical disadvantages in its small working volume and the mechanism's lack of backdrivability(reduction of friction).

Haptic master system employs three set of parallelogram linkages(pantographs) instead of linear actuators. Each pantographs is driven by three DC motors,which powered by PWM(Pulse Width Modulation) amplifiers.The top end of the pantograph is connected to a vertex of the top platform by a spherical joint.This pantograph mechanism has the same advantages as an octahedron mechanism,and it improves the working volume and backdrivability of the parallel manipulator. The inertia of the manipulator's moving parts is so small that compensation is not needed.

The working space of the center of top platform is a spherical volume whose diameter is approximately 40 cm.Each joint angle of the manipulator is measured by potentiometers.THe maximum payload
Haptic Master can represent arbitrary direction and strength force. With this compact hardware,the operator can feel the physical characteristics of three types of virtual objects.

1.Hard surface
Reaction force from the virtual surface is applied to the user's hand.The user cannot penetrate the surface.This function shows large payloads of the force display.

2.Elastic surface
The user can push and deform the surface.Reaction force increases in proportion to the deformation.This function can be applied to 3D shape modeling.

Fluid velocity is represented by force,and vorticity is represented by torque. When the user places a hand in the fluid, resistance from the flow can be felt. If the user's hand comes to vortex,it is twisted.This function can be applied to scientific visualization.

Detailed explanation