Multi-source Harvesting Systems for Electric Energy Generation on Smart Hip Prostheses - Biomedical Engineering Systems and Technologies - page 63

Fig. 2. Multiple Energy harvesting systems for a hip prosthesis prototype

Fig. 3. (Left) Scheme of the TEEH generator; (Right) CAD of the PEH generator

3.2 Translation-Based Electromagnetic Power Generator (TEEH)

Power Generator Prototype Design. An electromagnetic power transducer was de-
signed in the body of the hip prosthesis, as shown in Fig. 3 (left). It transduces mechan-
ical movements, from the abduction-adduction and flexion-extension axes, into electric
energy. The generator prototype comprises an extension coil spring ( K =2 . 45 N/m,
5 mm of diameter and 0 . 2 mm 2 of wire section) and 2 neodymium disc magnets N35
( 6 mm of diameter, 6 mm of height and 1 . 22 T of magnetic field). These magnets are
suspended inside a Teflon tube ( c m =0 . 04 ) where enamelled copper wire ( 0 . 1 mm of
diameter, 27 mm of length and 1 . 72

10 − 8 Ω m of electrical resistivity) was wound
( N = 2000 turns, 124 . 4Ω of total wire resistance), which in turn was attached to the
hip prosthesis fixture. The coil and the prosthesis make up the body frame. A relative
displacement z ( t ) between the magnets and the frame comes up due to the hip displace-
ments y ( t ) , which are transmitted by the body frame.

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