Motus Blog

Humans know intuitively or from experience that if we put weights on our wrists or elbows, it becomes more difficult to move our arms.  If we apply the same force we used without any weights, our arm will move more slowly.

It’s no surprise, then, that we see the same result in robots:  as joints get heavier, the arm moves more slowly when the same force (or torque) is applied.  Conversely, removing weight from the wrist or elbow actuator using a lighter weight transmission/gear drive results in higher speeds for the same applied torque.
What does a 10-15% increase in robot speed imply for robot owners?

As we mentioned in the last post, we will be looking at how torque density influences different robot parameters, including reach, speed, and lifetime.  Each of these in turn has a direct and important impact on the economic value of a robot to the end-user.

In the context of robotic actuators, the term torque density refers to how much torque the actuator is able to produce per unit weight or unit volume.  The term can be applied to the actuator as a whole or separately to the motor or gearbox that is contained within the actuator. Why should we be interested in torque density?  Because the torque densities of a robot’s components can limit nearly every facet of a robot’s performance.