Multi-source Harvesting Systems for Electric Energy Generation on Smart Hip Prostheses - Biomedical Engineering Systems and Technologies - page 61

1.2 Method

Three vibration-based energy harvesting systems were designed to implement a reli-
able electric power supply of a smart hip prosthesis. Linear models were developed in
order to analyse their accuracy predicting the energy generation. Each generator was
independently tested. Voltage generation was acquired from different rotational and
translational movements.

1.3 Paper Contribution

This paper's main contribution is to validate the multi-source generation concept ap-
plied to smart hip prostheses. The main goal in the implementation of these harvesting
systems is to enable a multifunctional ability of the hip prosthesis, namely to monitor
and report failures, and carry out mechanical-based therapeutic prescriptions.

1.4 Main Conclusions

This study shows that it is possible to implement high reliability electric power supplies
for active hip prostheses. It was also concluded that linear models of the generators are
very inaccurate in this particular application. Experimental results show that they must
be optimized in order to maximize their performance during typical walking speeds
and to reduce their volume, which demands for accurate non-linear models to predict
the energy generation for multi-displacements of the hip prostheses.

1.5 Outline

The new concept of smart hip prosthesis is introduced in section 2. The design of the
three power generator prototypes is detailed in section 3. Experimental and simulation
results are presented in section 4. Discussion and conclusions are stated respectively in
sections 5 and 6.

2 The New Concept of Smart Hip Prosthesis

Passive prostheses are orthopaedic implants without active components implemented to
overcome failures that may occur over time. They are designed: (1) without information
about themselves, about the physiological environment that surrounds them and about
how to fix their own problems; (2) without resources to eliminate causes of failures;
(3) without a “true” connection with medical specialists. The ineffectiveness of this
method to overcome complications after primary joint replacement is caused by this
passivity, because a maximal interaction with the surrounding physiological environ-
ment is not taken into account. The concept of smart orthopaedic implant was proposed
to be based on a smartness-to-measure methodology [33], but is becoming obsolete as
the concept of individualized therapy evolves for accommodating patient physiologic
idiosyncrasies [34]. Several studies have contributed to identify the function of strain,