Grabity: a virtual reality haptic controller for creating gravity and stiffness during grasping motions through asymmetric vibrations
A device to simulate kinesthetic pad opposition grip forces and weight for grasping virtual objects in a virtual reality is provided. The device includes a base, a sliding part, a braking mechanism and a swinging part with linear resonant actuators (e.g. voice coil actuators). The sliding part is connected with the base through a first prismatic joint which allows for single degree of freedom pinching motions for grasping an object. The swinging part connected to the sliding part and the base through revolute joints. The brake mechanism is used to create a grasping force. The linear resonant actuators provide both touch sensation at initial contact and sensation of weight when lifting the object.
1. A device to simulate kinesthetic pad opposition grip forces and weight for grasping virtual objects in a virtual reality, comprising:
(a) a base, wherein the base has a thumb pad;
(b) a sliding part connected with the base through a first prismatic joint, wherein the sliding part has a finger pad, wherein the prismatic joint allows for single degree of freedom pinching motions between the thumb pad and the finger pad for grasping an object,
(c) a brake mechanism on the sliding part as a first actuator, wherein the brake mechanism is used to create a grasping force; and
(c) a swinging part connected to the sliding part and the base through revolute joints, wherein the swinging part comprises two linear resonant actuators as second actuators connected through a second prismatic joint, wherein one linear resonant actuator is placed closely to the finger pad and the other linear resonant actuator is placed closely to the thumb pad for transmission of vibration signals, and wherein the linear resonant actuators provide both touch sensation at initial contact and sensation of weight when lifting the object.
2. The device as set forth in claim 1 , wherein the base has retroreflective markers to be captured by an external optical motion capture system for tracking the thumb's position and orientation.
3. The device as set forth in claim 1 , wherein the first and the second prismatic joints are made of carbon fiber tubes.
4. The device as set forth in claim 1 , wherein the finger pad is an index finger pad.
5. The device as set forth in claim 1 , wherein the brake mechanism contains a brake lever, a tendon, and a motor.
6. The device as set forth in claim 1 , wherein an offset distance between the revolute joint and center of mass of the swinging part ensures that the direction of the linear resonant actuators is always passively directed to be normal to ground.
7. The device as set forth in claim 1 , wherein linear resonant actuators are voice coil actuators.
8. The device as set forth in claim 1 , wherein the second prismatic joint on the swinging part constrains two angles of linear resonant actuators to be the same while allowing them to slide relative to one another.