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2005 - Fluidhand 8

The Fluidhand 8 has 8 drives that are controlled via 5 valves. The bellows in the index finger and middle finger are each hydraulically coupled with each other, and the drives of the ring and little fingers are also connected with each other via a common valve. The special feature of this further development is that the metacarpus has been replaced by a hermetically sealed pressure body. Inside the metacarpus is an elastic tank in the form of a diaphragm, in which both the drive medium (vegetable oil) and the control electronics, valves and pump are integrated; all system components "float" permanently in the drive medium. Between the pressure body shell and the diaphragm there is again a two-phase gas with a constant pressure of 2 bar.

The integrated design allows any space reserves in the metacarpus to be used as a fluid reservoir, while at the same time forming a maximum gas volume for preloading the hydraulic tank. The pump can draw directly from the environment and the pump, valves and electronics are optimally cooled by the surrounding liquid. The design makes the hand very compact and at the same time extremely stable. Due to the very flat metacarpus of 30 mm and the short design, the hand achieves an anatomical shape and with only 410 g it is particularly light. The Quicksnap wrist closure makes the prosthesis compatible with all stem systems and their power supply. The prosthesis is controlled by two EMG electrodes integrated in the prosthesis socket. Simple trigger switching signals can be used to switch between pre-programmed grips and the grips can then be controlled proportionally. For the first time, a sense of touch has also been integrated into the prosthesis. The grasping force measured on the index finger via a sensor is transmitted to the system controller, which activates a vibration motor on the hand that transmits coded information to the prosthesis wearer about the force applied. In addition, the Fluidhand 8 serves as a test platform for new prosthesis controls such as grip pattern recognition or motion control using 3D sensors, research areas on which the research center has been working intensively as part of the Fluidhand development.

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