Smart Prosthetic Hand with Object Slippage Detection, Measurement, and Control

Problem Statement

More than 2 million Americans live with a lost limb (ACA News, 2011). That number is slated to grow drastically each year. The main causes for amputations on the United States of America are vascular diseases, trauma, cancer, diabetes and injuries. With the wars in Afghanistan and Iraq coming to an end the number of soldiers with amputations will reduce drastically. The advent of diabetes and other debilitating diseases which cause cardio-vascular problems will drastically increase amputations in The United States of America. For the people with limb loss, to regain mobility, increasingly capable prostheses are being developed by the day to improve the quality of their lives, regardless of whether the loss of limbs were from war, accidents, diseases or birth defects.

With the advancements in technology, the latest prosthetic hands come with electrodes which are invasive in nature and require surgery to place the prosthetic hand in the human arm and replacement of it is difficult. With the advent of newer surface electromyography (sEMG) based prosthetic devices, (C. Potluri, M. Anugolu, A. Jensen, G.Sriram, S. Liu, S. Chiu, A. Urfer, 2012) the problem with invasive procedures are reduced for the potential user.

Slippage Control

According to the dictionary (Merriam Webster 2014) slippage is defined as an act, instance or process of slipping. In the context of hand prostheses slippage can therefore be interpreted as an act of slipping, of an object which has been gripped. Slippage control is the act of holding/griping the object under slippage.

Generally arm movements are done involuntarily by humans as they grow up and learn. Slippage control in a human hand is done involuntarily by the muscles with feedback from the various skin receptors in the somatosensory system (Wikipedia 2014) in our bodies. Slippage control in the human hand is accomplished via the feedback from the glabrous skin receptors, which include mechanoreceptors, thermo receptors, chemo receptors and photoreceptors. These skin receptors along with the spinal cord and the brain make up the somatosensory system of the human body. Slippage control in humans involves mostly involuntary hand movements, but it can also be voluntary based on feedback from these receptors.

Tactile perception (touch) is considered one of the five primary senses of the human body. The other senses include sight, hearing, smell, and taste. Thus tactile sensing is the most important part for an effective slippage control system. Tactile sensing in humans starts with haptic perception (Wikipedia 2014) which is the recognition of objects through touch. Then the information is transferred/fed back to the brain through the spinal cord for analysis of the information, to make a corrective motion of the hand.