**2. Materials and methods**

inserted. The *Osaka Hand* is attached to the other tip of the socket via a screw. This socket is expensive to produce and requires weeks to manufacture after measurements are taken

An additional initial problem is that shortly after an amputation atrophy of the remnant muscles occurs, and their EMG signal becomes very weak. As that EMG signals are used to control the prosthesis, users wanting to wear the *Osaka Hand* (or any other myoelectric hand) must undergo a training phase in which their remnant muscles are strengthened and at the same time they re-learn how to perform fine, detailed muscles contractions, which are needed

In order to solve the two problems mentioned above, we developed a graphic simulator system for the *Osaka Hand* that eliminates the need of a socket for attachment of that prosthetic hand

A number of works on prosthesis simulators have been already described, each of them fitting the specific requirements of a given prosthesis. Yamada *et al.* (1983) employed six different bidimensional (2D), fix images appearing on the screen depending on the frequency and amplitude pattern of three EMG signals in order to evaluate their proposed control method for a theoretical prosthetic hand. Daley *et al.* (1990) developed a simple 2D graphical simulator for operator performance comparison when using different myoelectric control strategies. Abul-Haj and Hogan (1987) performed an emulation with a combination of software and hardware for elbow-prosthesis prototypes evaluation. Perlin *et al.* (1989) developed a simula‐

Several works describe simulators operated by shoulder movement; Zahedi and Farahani (1995), for example, used a graphical simulator for a fuzzy EMG classifier; Durfee *et al.* (1991) created a 2D graphic simulator to evaluate command channels trough which control an upper limb neural prosthesis; and Zafar and Van Doren (2000) employed a videobased simulator for a shoulder-activated neuroprosthesis for spinal cord injured persons. Lin and Huang (1997) made a computer simulation of a robotic hand to test its potential

There are already some commercially available systems such as *MyoBoy* –from OTTO BOCK HealthCare GmbH (Duderstadt, Germany)- that is a software tool used for the evaluation, selection, training, and documentation of myoelectric patients. MOTION CONTROL Inc. (Utah, USA) has developed an EMG tester and trainer (*Myolab II*) that is used to locate intact

However, all the abovementioned simulators can be used only with prosthetic hands with a switched or single proportional mode, not for those with a more complex control mode as the

The goal of the present work was to develop an upper limb and hand graphic simulator system that solves the abovementioned problems, allowing amputee subjects to try virtually the myoelectric hand without needing the socket, and to perform the physical training required prior to use the real one. This simulator allows us also to easily identify the optimal electrode

to the stump and it is also used for physical training of myoelectric patients.

tion program for their Utah/MIT 16-joint, four-finger *Dextrous Hand*.

muscle activity and to help patients in strengthening and relaxation tasks.

(Sears, 1991).

use as a prosthesis.

one of the *Osaka Hand*.

for a precise control of the prosthetic hand.

270 Electrodiagnosis in New Frontiers of Clinical Research
