GoldFinger: human-machine interface
GoldFinger is a wireless human-machine interface with dedicated software and a biomechanical energy harvesting system.
GoldFinger is the result of a cooperation work with the Massachusetts Institute of Technology (USA).
Hand motions are used to communicate with the machine via a LED tracking system. Then, information is digitalized with dedicated software that also provides the machine microcontroller programming in the C language.
The battery discharge time is reduced due to the power harvested from integrated piezoelectric transducers, which generate power from finger motions.
The importance of hands
Natural evolution provided human beings with one of the most efficient mechanical interfaces with the outer environment: hands. People use their hands to interact with tools and other people every day. Almost continuously, we send messages and commands by hand, and through our hands, we perceive the world around us.
Thus, it is not surprising that the most natural way to interact with machines is through the direct use of hands without intermediate peripherals, such as keyboards, buttons, mice or joysticks. When personal computers (PC) were born, the only way to provide input to them was through hardware interfaces, and the only way to perceive outputs from PCs was through monitors or displays. Similar conditions are present in many machines, systems and plants that contribute to everyday life.
In many interfacing actions, the user has to modify his natural behavior and his spontaneous posture to start a dialogue with the machine; thus, the machine is perceived as a foreign body by humans, and people must conform to the machine to achieve the full potential. GoldFinger aims to overcome these limits.
Data transmission by light
The human gesture is composed of hand motions, light switching, and a combination of them. The hand analog command sequence is sent to the receiver through the light emitter installed on the fingertip. The optical receiver is a camera and works as analog-to-digital converter (ADC). Through the software interface, the light path and light on/off flashing sequence is tracked and converted into Cartesian coordinates through the mathematical coding of gestures.
Another function of the software associates the light commands to their meanings (as previously codified) and provides the relative microcontroller programming.
Biomechanical energy harvesting
The energy harvesting system integrated into the GoldFinger glove is made with piezoelectric transducers composed of active foils with metalized surfaces and insulated with a polymeric package. The energy harvester output has a random shape. A diode bridge provides the first voltage rectification, and the following capacitor imposes the desired voltage level for battery charge. An operational control regulates the battery operations by allowing the current to flow towards the main battery only when the charge voltage threshold is achieved. Below is the power produced by each proximal interphalangeal (PIP) joint of the fingers 1 to 4.