Design Team Co-ordinators:
The artificial hand described here was started as a project with initial funding by the Ministry of Social Justice and Empowerment in 1999, following a suggestion from the All India Institute for Physical Medicine and Rehabilitation, Haji Ali, Mumbai. The project was executed at the Indian Institute of Technology, Bombay (IIT-Bombay). The first version was completed around 2000-2001, and clinical trials were conducted at the Christian Medical College, Vellore (CMC-Vellore). Subsequently, considerable improvements have been made at CMC-Vellore. The trial versions and now the commercial versions of the artificial hand are manufactured by WORTH Trust, Katpadi, Vellore. For the sake of convenience we call it the Bombay-Vellore hand.
Continuous improvements are being made on the design, and the three collaborating institutes now are: (1) Christian Medical College, Vellore, (2) Indian Institute of Technology - Bombay, and (3) WORTH Trust, Katpadi, Vellore. All three institutions continue to invest monetary and other resources.
In designing an artificial hand it is useful to consider the functions of a normal hand.
The following schematic shows the main blocks of normal motor control. It is important to note
that in addition to the motor function there are also sensory feedback
mechanisms, proprioceptive feedback mechanisms, etc., which are imporant
and integral parts of the hand.
In this design we have focussed on the motor action and no real sensory feedback mechanism is incorporated. (However, indirect feedback is provided).
The main movements of a normal hand can be noted as follows:
A Schematic diagram of the hand mechanism is shown below. Three motors are used: one for the hand fingers, one for for forearm supination/pronation, and one for elbow flexion/extension.
The following diagram shows the block schematic. The battery is a 7-12V Li-Ion (or other) battery, and
supplies power to the microcontroller as well as the motor drivers.
The Bombay-Vellore hand is modular in design, and various subsets of it can be used depending on the needs of individual users. Many users need only hand function (finger grasp/prehension) and use a single motor artificial hand. Only a few users require a full three motor hand with elbow articulation.
For more details on fitting, training and use of the Bombay-Vellore hand, please see the other sections.
The following two pictures show two views of the three motor hand for above elbow amputees:
The present design demands a lot of visual attention from the user when doing tasks with the hand. Clearly, some feedback is desirable. The question right now is what is the order of importance for the different sensory inputs:
