Miniature Valves Help to Make Robotic Hand Realistic

Imagine the essential requirements for the components used within a humanoid robot hand which is designed to replicate all the joints and movements of a human hand? Now imagine these components, for example over 100 touch sensors, must be even smaller if the design is to be successful. When robotics get the human touch, size really does matter, and in this case the smaller the better. The North London based Shadow Robot Company is a small team of enthusiasts developing advanced robotic systems used in applications such as medical research but ultimately with the potential for manufacturing the first humanoid domestic robots.

The systems developed by Shadow use compliant pneumatic actuators, otherwise known as air muscles and these offer important advantages for robotic systems.

The design of the hand demands large quantities of air muscles, 36 in all to control a total of 25 separate hand movements, resulting in the need for 72 valves to control the flow of air into and out of each air muscle. An essential requirement for good air muscle control is the need for the valves to be located as close as possible to the muscles, in this case inside the elbow of the arm.

A major problem which Shadow had to overcome was that such a large quantity of valves were proving to be too large to pack within the form factor of the robot and consequently many types of valves were tested. Lee Products were able to provide the solution, thanks to the ultra-compact size of their face-mount HDI solenoid valves.

The design of these valves enables Shadow to pack 72 valves into 1/30th of the space available and embed them directly into the dextrous hand itself, making a significant improvement in the quality and performance of the system. In fact, Shadow also tried fitting an even smaller Lee plug-in HDI valve into the hand. However, this would require the design of a more intricate manifold to accommodate these even smaller valves.

Hugo Elias, Technical Director at Shadow Robots commented, “Most of the valves we tried were described as ‘miniature’ although these were still at least as big as my thumb, however, the Lee valves were small enough to fit into a cylinder 120mm in diameter and 65mm long”. He continued, “All of the other valves we tried were simply too bulky, the previous valve rig occupied a cubic foot of space and had to be mounted under a table and this made the robot arm non-portable, also reliability of valves had been a factor”.

Summing up, Hugo said, “We particularly appreciate the small size of the Lee valves, now the robot hand is self-contained, needing only an air supply and 24v power and can be easily carried around an exhibition”.

Lee HDI (LHD) series solenoid valves are designed on the 3-way HDI (High Density Interface) valve platform and can respond as fast as 1.0mSec. They consume only 550 or 750mW of power, depending on the model selected. They are available in a flexible plug-in configuration, so they are ideal for compact manifold applications.

A one place ported adapter for use with 1/16” tubing is available in addition to a variety of standard manifolds. The valves, which are available in 5,12 and 24 volt versions, have a flow capacity of 10 SLPM and a pressure range of 0-15 psig.