Initial design concept for the glove:

For a glove exoskeleton, ideally we would like to be able to separate the finger into two links and give actuation for both links. However since I need to make a wearable, using the current set of commonly and cheaply available actuators, I will only be providing a single link to apply the force on the index finger.

Since I want to be able to apply a variable impedance at various points in the coordinate space for the finger. I am currently working along the lines of a motor and spring combination.

The reason why I am using the spring is because of time response and ease of control. One of the main use-cases in VR is currently gaming. Gaming interactions are very quick. This means we need to be able to apply forces on the hand very quickly. If I use only a servo and combine it with a force or pressure sensor at the finger tip(or something along those lines) then there will be a time lag between when the force or movement is detected by the sensor, this information is sent to Micro-controller, then either processed by VR device then sent back to controller and then actuated by the motor.

However with the spring device, when the finger is trying to move, the physics of the spring will automatically apply a force on the finger. I will sense this change in force and then control the motor to change the deformation of the torsional spring. This will ensure a responsive actuator with fast feedback and at the same time allow for generation of impedance in a more natural way.

I am thinking of using a rotation sensor to sense the deformation in the spring. It looks like some mechanical encoders are available cheaply however these encoders have only 24 pulses per revolution. I think this is a somewhat low resolution. I am thinking of either using a gear between the shaft and encoder to give me a higher effective resolution OR to use an optical encoder.

Do let me know if you have any suggestions on cheap,compact rotation sensor with atleast 4 degrees resolution.