The first primitive electric motors weren’t developed until the early 19th century, and machinery before then relied on purely mechanical ingenuity. Then electromechanical machines changed the world, but even then clever mechanisms were needed to implement any kind of logic. The digital revolution dramatically altered the way machines were controlled and we haven’t really looked back since. But it is still possible for machines like robots to “think” mechanically, though it is something of a lost art. Engineers from the University of California San Diego are reviving that art to build pneumatic robots that operate without any electronic components at all.
Robot-like machines were being built as early as 270 BC when Greek engineer Ctesibius used hydraulics and pneumatics to build water clocks with moving figures. Leonardo da Vinci also devised a mechanical knight robot that would have been at to sit up and move its hands and arms. Even early machine tools could follow complex mechanical guides to accomplish results similar to modern CNC machines. These days we use computers, microcontrollers, and PLCs (Programmable Logic Controllers) to operate our robots and machines, because they’re relatively affordable and offer a tremendous amount of flexibility and computing power. But there are situations when those electronic components are not ideal, such as in harsh environments where they could easily be damaged. These pneumatic robots can continue to operate as long as they have air pressure and retain their structural integrity.
Pneumatic actuation certainly isn’t a new idea in robotics, but the way it is being used here is very unique. Pressurized air is pumped into the robot from an external source and fills a series of bladders in sequence. Those bladders are strategically located in each of the robot’s four legs. Internal valve systems ensure that each bladder is inflated before the next in the sequence, so the legs move in a coordinate fashion. That lets the robot walk along, but a robot that can only walk in one direction wouldn’t be particularly useful. That’s why this robot has a special pneumatic “trigger” that acts like a sensor in a more conventional robot. When that button-like trigger collides with an object like a wall, it briefly opens a valve. That valve throws a sort of air switch, which alters the bladder inflation sequence so that the robot will walk in a direction perpendicular to its original trajectory. In the future, the team hopes to improve their “pneumatic circuits” to increase the complexity of the robots they build. The hope is that they’ll eventually be able to replace electronically-controlled robots for some applications.