SBIR-STTR Award

Hydraulic actuation systems for mobile robotics are characterized by high bandwidth, high power density, robust operation, flexible power transmission but also by low efficiency, high rejected heat, and high noise levels. The undesirable characteristics of hydraulic power systems are not inherent to fluid power transmission; they are the result of the highly inefficient techniques used to control the power delivered to individual actuators. The spool valve architecture that dominates hydraulic servo systems has roots in gasoline powered heavy equipment where efficiency and noise are not primary concerns; this architecture is not appropriate for modern mobile robotics. Berkeley Bionics has been a leader in innovating novel hydraulic systems for mobile robotics from our roots working with hydraulic servo systems on the DARPA exoskeletons program at the University of California, Berkeley. Our current third generation HULC exoskeleton, under development with Lockheed Martin, uses proprietary hydraulic components and non-standard servo controls. Currently our electro-hydraulic actuation systems have overall efficiencies nearing 50%. The proposed project builds on our industry leading technology to design an electro-hydraulic actuation system that will rival the overall efficiency of an electro-mechanical actuation system, while maintaining an extremely low audible signature and the intrinsic benefits of hydraulic actuation.

Keywords:
Mobile Hydraulics, Exoskeleton, High Efficiency, Low Noise, Regeneration, Walking Robots, Electro-Hydraulic

One of the current limitations for mobile robotics walking is efficient actuation. The standard actuation technologies that have been used in mobile robotic platforms are servo-hydraulics, electro-hydraulics and electro-mechanical actuation. The hydraulic options have a high power density and pack well but are very inefficient leading to carrying extra batteries in mobile applications. The electro mechanical options improve on efficiency but require the actuation to be located at the point of actuation, leading to large masses on the legs and significant increases in power consumption. On top of that, these designs have limited success addressing the large ranges of power output found in legged locomotion in particular the range between walking and running. This work intends to develop a new method of actuation that is uniquely capable to meet the needs of mobile legged robotic applications. The proposed solution is a hydraulic based design that uses active control of pump displacement to manipulate its performance characteristics. The proposed solution will allow many joints to operate off a single motor without losses from valves. The proposed active displacement hydraulic power unit will provide system bandwidth comparable to servo-hydraulics and efficiencies better than electro-mechanical systems in an easy to package quite design.