Grasping a new reality

Need an extra hand?

Mindful of the ageing population in Japan, engineers are motivated to develop robots that could one day assist the elderly in their daily tasks. Developing a robotic hand that shows dexterity and variable pressure capabilities is the first step in creating robots that will be able to perform everyday tasks.

In the October issue of Smart Materials and Synthesis (doi:10.1088/0964-1726/20/10/105015), Dr. Nagase of Kwansei Gakuin University in Sanda, Japan and his colleagues describe their design for a new robotic hand that mimics the dexterity and grasping abilities of a human hand. Not only does the hand perform similarly to a human hand, its size and weight are almost identical to the average adult hand.

Robotic hand developed by Dr. Nagase at Kwansei Gakuin University and his colleagues

Perhaps future robots will be modelled after humans so that it will be more comfortable when the robots assist the elderly.  Wouldn’t you think it is intimidating to have a large robotic hand turn the page for you as you read?

The robotic hand has four fingers attached to a palm, and each finger consists of three joints that allow the fingers to bend and flex.  The palm and the ‘bones’ that make up the fingers are made of ABS resin. Silicone rubber tubes with Kevlar fibres inside as reinforcement encase the ‘bones’ and form individual fingers.

http://ist.ksc.kwansei.ac.jp/~nagase/index_e.html 

A balloon actuator causes the hand to open and close. The balloon actuator consists of a silicone tube that is sealed at one end and expands to produce a balloon when compressed air is supplied through the opened end. A metal ‘tendon’ is wrapped around the balloon and expands when the balloon expands. This forms a pulley system and acts as the joints in each finger.

The balloon actuators allow individual fingers to be controlled, so the hand can hold objects in different ways:

• Fully grasp an object with the fingers and thumb
• Pinch an object using the thumb and index finger
• Support an object using the fingers as a platform and the thumb to hold an object

***Watch the robotic hand in action on Dr. Nagase’s website: Robot handic holding a paper cup 

The amount of compressed air supplied to the hand regulates the pressure of the fingers. This enables the hand to show variable finger pressure/hardness and allows it to perform different motions including turning a page or smoothly pet a dog.

A robotic hand operating on compressed air does exist already. But for Dr. Nagase and his colleagues, their design has shown some unique advantages. Their robotic finger actively changes the finger’s frictional force by changing the stiffness of the finger. Consequently the finger can move smoothly to pet a dog, and avoid the uncomfortable feeling caused by a constant pressure and finger posture as required by other passive approaches. 

We have yet to create an ideal robotic hand that can mimic the complexities of the human hand, but what Dr. Nagase and his colleagues have achieved with their robotic hand has proven to be a big step towards achieving that goal.

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Nagase, J., Wakimoto, S., Satoh, T., Saga, N., & Suzumori, K. (2011). Design of a variable-stiffness robotic hand using pneumatic soft rubber actuators Smart Materials and Structures, 20 (10) DOI: 10.1088/0964-1726/20/10/105015

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