Along with combining precision, speed and strength, the hand's hydraulic actuators are also claimed to offer better longevity, impact resistance and heat management than traditional cables and motors

Sanctuary AI's Phoenix robot is certainly an impressive beast, with hydraulically actuated hands that are incredibly dextrous. Well, those hands have recently become even more useful, as each one is now capable of simultaneously holding and manipulating an object.

Ordinarily, the fingers of a robotic hand are moved by cables connected to electric motors. It's a reasonably simple, effective and inexpensive setup, as long as the hand is only required to perform certain types of tasks.

Sanctuary AI wanted its Phoenix humanoid robot to be as versatile as possible, however, which is why the Canadian company went with miniature hydraulic valve actuators for the bot's hands. According to former CTO Suzanne Gildert, who our own Loz Blain interviewed back in April, hydraulic tech is the only option for combining precision, speed and strength.

"If you see a robot doing something really dexterous, like threading a needle, or doing a button or something, you have to ask yourself, could that hand also lift a 50-pound suitcase? And could it also move fast enough to, say, type on a keyboard?" she asked. "Usually people only show one of these three factors, but the ultimate hand needs to have all three. Currently, the hydraulic technology's the only one that can get you all three of those."

You can see the previous incarnation of the hand(s) in meticulous action, in the following video.

While that footage may indeed be quite impressive, last week Sanctuary AI announced that its 21-DOF (degrees of freedom) robotic hand is now also capable of in-hand manipulation. In a nutshell, this means that just one of the hands can both hold and manipulate an object at the same time.

As you can see in the video below, this additional dexterity allows the hand to perform tasks like turning over a gaming die and even reducing the jaw width of an adjustable wrench. Such precision is partially made possible by a force feedback system, which is integrated into each actuator.

"You control the hydraulic system by varying the line pressure of the hydraulic fluid," said Gildert. "So if there's a force coming back on the finger, it modulates the control signal that you're seeing on that line pressure. So you can actually detect forces by monitoring how the pressure minutely changes."

Importantly, the hydraulic valve actuators have reportedly been run through over two billion testing cycles without any signs of degradation or leakage, the latter being a common problem with hydraulic systems. It is now hoped that the added functionality will ultimately make robots such as Phoenix more feasible for widespread real-world use.

"Demonstrating in-hand manipulation with a scalable and reliable system is a key milestone towards demonstrating the breadth and viability of capable general purpose robots," says interim Sanctuary AI CEO James Wells. "Dexterous capability is directly proportional to the size of the addressable market for general-purpose humanoid robots."