| Popis: |
An ideal upper-extremity prosthesis is expected to simultaneously decode users' intentions and deliver artificial somatosensory feedback. Among all the feasible feedback modalities, electrotactile stimulation remains the most promising solution due to its advantages of light weight, little noise and low power consumption. This thesis further enhances the existing electrotactile feedback strategies by proposing a haptics model, developing a portable electrotactile stimulation (ETS) system and establishing a virtual hand rehabilitation platform for implementation and evaluation. Firstly, a Gaussian distribution based haptics model is proposed to characterise the human fingertip's biomechanics, including a prediction model to estimate the contact force according to the fingertip deformation and a probabilistic model to describe force uncertainty. Experiments results reveal the non-linearity, dispersion and individual difference of the fingertip's mechanical behaviour. Secondly, a potable 16-channel ETS system with a wireless mode for transmission is developed to provide electrotactile feedback for clinical use. The proposed ETS system can generate stable current output with programmable stimulation parameters, including amplitude, frequency and pulse width. The ETS output waveforms and stability were evaluated by capability tests. Thirdly, a virtual hand rehabilitation platform is established to investigate the effect of electrotactile feedback on user training of hand grasping tasks. The platform consists of a surface electromyography (sEMG) acquisition module, a virtual grasping environment, and an ETS module. Experiments were conducted to evaluate the impact of electrotactile feedback on a closed-loop grasping control in comparison with the visual feedback and no feedback. The quantitative results show that the integration of electrotactile feedback can both reduce the duration of rehabilitation and improve the virtual grasping success rate in comparison with the no feedback condition while possessing a better practicality over visual feedback. In summary, the proposed electrotactile feedback centred research is validated in facilitating the user training and improving the rehabilitation performance. Despite the initial motivation of this thesis driven by the upper-extremity prostheses, the verified success of electrical stimulation is not confined to the hand rehabilitation scenarios but potentially applicable to a wider spectrum of applications, such as biomedical engineering and virtual reality. |
