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.
Recent technical paper contributed by Greg Zancewicz & Carlos Hoefken at the 5th International Conference on Control and Robotics Engineering. The paper discusses electric actuators adding weight along an articulated robot arm and how the torque and speed limitations impose additional dynamic constraints including useful life of a robot and the extent to which each actuator operates at or near its torque ratings.
Torque density is the ratio of the rated torque of a transmission to its weight. Torque density is an especially critical parameter in robot arm design since the weight of the robot arm actuators become part of a distributed load that needs to be moved and positioned along with the primary robot payload.