haptic wrist device

While our design process was largely collaborative, I focused mainly on integrating and programming the motor motion with gear rotations so that both flywheels would rotate in opposite directions with the appropriate speed. I also designed the base plates and user bracelets using Solidworks. 

Assembly is composed of base plates on the left and right, gears press fitted onto the right plate, center plates for flywheels, and a bracelet structure below. The two center plates can rotate and are attachment points for our flywheels. The rotation of these plates is controlled by the gears on the right. While the motor is not shown, one gear is powered and this configuration allows both plates to rotate in opposite directions. This entire assembly is mounted atop a rigid bracelet structure to stabilize and strengthen the force feedback of the device on the user. The device is then mounted on a user’s wrist by weaving a band through the holes on the bracelet.

The final assembly is pictured on the left, 3d printed and assembled with press-fit parts and screws. The motor, located in the back under the wrist, is then connected via pulley mechanism to the gears above.

In terms of our code and graphic use interface, we programmed several 3d visual renders using OpenGL and coded the device with C++ to impart force feedback based on our visual simulations. Our first simulation contained two parallel walls with a haptic device in the middle. As the user moved their hand and approached a wall, the device would impart force feedback to imitate hitting the wall. Our second and slightly more developed simulation was a matching game where a user was instructed to match the orientation of a rectangle with the orientation of their haptic device. For users with wrist proprioception issues, the device provided force cues to guide the wrist to the proper orientation. The greater the angle difference between the two rectangles, the greater force imparted by the device.

The center yellow rectangle changes angles to match physical orientation of the haptic device. When the device’s orientation is within 5 degrees of the orientation of the purple rectangle, a new purple rectangle is randomly generated at a new angle. The simulation then continues with the user trying to match the new orientations until completion.