We spent some time with Carlos Hoefken, CTO & Co-Founder, and asked him questions regarding the Motus CAM and CAM Generator™ software. In the video, Carlos uses the ML100 as an example, but the same CAM concept applies to the ML1000 series.
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.
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.
Although strain wave, or “harmonic,” gearing can deliver high reduction ratios in a relatively small form factor, it is well known that the technology also impairs the dynamic performance of robot arms due to elastic deformation that occurs even well below the drive’s rated torque.
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.