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 and his colleagues
Future robots will likely be modelled after humans, allowing the elderly to feel more comfortable when assisted by the robots. Wouldn’t you be intimidated by a large robotic hand that turns 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 reinforced with Kevlar fibres encase the ‘bones’ to form the individual fingers.
Source: Dr. Nagase
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 grasping an object with the fingers and thumb
- Pinching an object using the index finger and thumb
- Supporting an object using the fingers as a platform and the thumb to hold the object
***Watch the robotic hand in action on Dr. Nagase’s website: Robotic hand holds 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 the hand to perform different motions, including turning a page or smoothly petting a dog.
A robotic hand operating with compressed air already exists. But the design by Dr. Nagase and his colleagues has some unique advantages. Their robotic finger actively changes the finger’s frictional force by changing the stiffness of the finger. The active design allows the finger to move smoothly to pet a dog. On the other hand a passive design requires constant pressure and finger posture, which could result in jerky movements or an uncomfortable feeling for the dog while it’s being pet.
We have yet to see a robotic hand that can mimic all the complexities of the human hand, but Dr. Nagase and his colleagues have created a robotic hand that is one step closer to that ideal.
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