*4.2.1 Mind-controlled prostheses*

The mind-controlled prostheses (also called brain-controlled prostheses) sense the signal from brain, i.e., electroencephalogram (EEG) [13]. The controller extracts the information from the EEG signals after amplification and filtration in the form of features. These features are then used by the pretrained classifier to classify the desired movement of the prostheses.

#### *4.2.2 Myoelectric prostheses*

The myoelectric prostheses use the same mechanism as of mind-controlled prostheses. The only difference is the sensing or input signal. In myoelectric prostheses, the signal is sensed from the muscle level instead of the brain. These signals are named as electromyogram (EMG). The EMG signal is usually sensed at the residual muscle of the amputated limb. Therefore, the EMG signals are easy to predict the intentions of the user as compared with the EEG signals. On the other hand, EMG signals are likely to be dissimilar if the position of the sensor is slightly changed or the contraction of the muscle changes [14].

The myoelectric prostheses are the most commonly used prostheses due to onsite EMG signal acquisition and relatively simpler control scheme. The state-ofthe-art prostheses [15] for the upper limb will be discussed in this section with the open source 3D printing counter prostheses [16].
