April 10, 2013

Japanese DARPA Grand Robotics Challenge Competitor SCHAFT Looks To Showcase Its Powerful Motor Technology

Japanese DARPA Grand Robotics Challenge Competitor SCHAFT Looks To Showcase Its Powerful Motor Technology

 Robotics
Japanese DARPA Robotics Challenge entrant, SCHAFT Inc., has just announced a breakthrough in their motor technology that may bypass the limitations of existing servo-motor systems. The company is a spin-off of the University of Tokyo's Jouhou System Kougaku (JSK) Laboratory. They hope that this development will make their humanoid robot a top contender for the DARPA prize.
W ith the DARPA Grand Robotics Challenge getting closer and closer, the competitors are releasing more and more details about their projects.

Japanese entrant, SCHAFT Inc., is entering the competition and has just announced a breakthrough in their motor technology that may bypass the limitations of existing servo-motor systems.  The company is a spin-off of the University of Tokyo's Jouhou System Kougaku (JSK) Laboratory.  They hope that this development will make their humanoid robot a top contender for the DARPA prize.

Existing electric motors used to power most contemporary robots and equipment actually are not very powerful or responsive. For example Honda's ASIMO is only capable of lifting a few kilograms, and most other adult-size robots could be described as having one-tenth the strength of the average person.

This fact does not measure up to the traditional Hollywood portrayal of robot dominance, such as in the Terminator movies, but SCHAFT's new motor technology promises to dramatically turn the existing drive system paradigm on it's head.

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servo motor
Contempory servo motor
SCHAFT's system is a high-voltage and high-current liquid-cooled motor driver that gets its power from a capacitor, not a battery. The capacitor can supply lots of current very fast and reliably, something that batteries are not good at. This in turn delivers high speed to the electric motor and high torque to the system, something that is hard to do with conventional motors.

In servo-motor use, the list of issues includes (besides high relative cost):
1) Require "tuning" to stabilize feedback loops.
2) Motors "runs away" when something breaks. Safety circuits required.
3) Complex. Require encoder.
4) Brush wear limits life. Service is then required. This system causes friction between the brush and commutator, which requires replacing and maintenance
5) Peak torque is limited to a ~1% duty cycle.
6) Motors can be damaged by sustained overload.
7) There is a bewildering choice of motors, encoders, servo drives.
8) Power supply current 10 times average to use peak torque. See (5).
9) Motor develops peak power at higher speeds. Expensive and large gearing often required which are often as big or bigger than the drive unit.
10) Poor motor cooling. Ventilated motors are easily contaminated.
Based on the preliminary reports, it looks like SCHAFT's system may address many of these drawbacks with servo motors.

Along with robotics, SCHAFT motors may have huge impacts in other industrial areas.  For instance in Computer Numeric Control (CNC) manufacturing systems, corner rounding issues are common for machining systems.  In large heavy machines moving with precision and speeed particularly in corner situations is not achievable with most servo-motor driven systems.  Commonly speed is achievable in straight motions, but in corner rounding or 3D cutting, the motion control requires complex compensation factors.  3D printers could also conceivably be impacted by this development.

cnc corner rounding
SCHAFT has now completed a prototype robot you see pictured above. Rugged looking and boxy compared to some of its competitors it may be, but the mechanical factors may outweigh a lot of other considerations in final contest outcome. The robot is already walking and practicing for the challenge.

A good performance at the DARPA competition will undoubtely raise the profile of SCHAFT, in Japan and elsewhere, and promote adoption of their motor technology. The company says it will begin to market the robot's arms, which are small, highly articulated, and powerful, as a stand-alone part for use in mobile robots and manipulation research, however as we have mentioned here, look for a lot of other electrical motor-driven application developers to sit up and take notice too.
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