BionicCobot: Mimics Human Arm with Air-Powered Safety

How Does the BionicCobot Work?

This cobot functions in a similar way to a human arm - seven joints that function like those in a human shoulder, elbow, and wrist. Inside each joint, there is a rotary vane with two air chambers. Think of these as being the artificial muscles that help the robot move.

More specifically, here's how it works: when air is pumped into the chambers, the vanes rotate, causing the joints of the robot to move. The pressure level of the compressed air can be adjusted; hence affecting the amount of force or stiffness exercised by the cobot to perform a particular task. This ability not only enables the cobot to move flexibly and safely but also allows it to carry out lighter tasks such as lifting a light object, as well as tasks that require more force or precision (by increasing the stiffness of the cobot). This is somewhat similar to how humans use different amounts of muscle strength to lift a light book or a heavy box.

To operate the BionicCobot, a tablet is used where the user can set up the cobot's movements in a sequence. The programming or user interface is designed to be intuitive and straightforward.

Complexities of Pneumatic Design for a Cobot

A major complexity in the design of the BionicCobot revolves around the routing of the cables and hoses. There are two hoses for each joint and 16 hoses in total. Having all these hoses and routing them such that they don't restrict the motion and reachability of the cobot is challenging. The team has therefore decided to route the hoses outside of the joints with plastic covers to protect them.

Other design aspects may also become challenging due to the pneumatic structure of the cobot. For example, pneumatic systems generally offer less precision compared to electric motors; hence, making it hard to achieve high positioning accuracy (1mm for this cobot) using such cobots.

Why Consider a Pneumatic Design for a Cobot

There are numerous advantages to using a pneumatic design. But when it comes to cobots, the inherent safety, simplicity, and lightweight design are particularly attractive.

A pneumatic system in a cobot uses compressed air to move its parts. This setup allows the robot to move in ways that feel natural. Because the pressure of the air can be controlled, then the cobot can be operated more strongly or gently with varying degrees of rigidity, depending on what's needed.

The air can also act as a spring making the cobot inherently safe. For example, if the cobot is working next to humans and accidentally bumps into someone, it will automatically soften its movement upon impact, thus preventing injury. This behavior is similar to how a person's reflex would cause a quick pullback of the arm when the arm unexpectedly bumps into something. Additionally, pneumatic drives are generally lighter and not as complex (require fewer complex parts like servo motors and gears).

Why Aren't Pneumatic Designs Popular for Cobots

Pneumatic actuators generally offer less precision and accuracy than electric actuators, hence such cobots may not be suitable for tasks that require complex or highly meticulous positioning and movements.

In addition, there are complexities involving the air supply. Not only does this aspect add complexities in terms of installation and maintenance, but the facilities also need to have appropriate compressed air infrastructure which can be costly or space-consuming.

Although this may not apply to the BionicCobot, there are other concerns generally associated with pneumatic systems. For example, these systems may cause the cobot to be slower, noisier, or sensitive to environmental conditions such as temperature and humidity.