Monopropellant-Powered Actuator


This proportional actuator developed at Vanderbilt University is a superior source of controllable power for mobile robots. It utilizes monopropellant or hypergolic bipropellant fuel sources in a controlled manner for more efficient and effective untethered mobile robots performing human mechanical tasks over a prolonged period of time.

Addressed Need

• Electrochemical batteries, typically used to power electric motors in mobile robots, are limited by insufficient mass specific energy density to perform human scale work for a long time. For example the Honda P-3 Humanoid robot only operates for 15-25 minutes depending on its work load.

• Electric motors are energetically expensive and require a bulky speed reducing gearbox, adding weight.

• Hydraulic actuators require pumps that are too heavy for human scale robots

• Internal combustion engines cannot be force or motion controlled over bandwidths of human-scale robots. They must be used to drive more complex, low energy-density systems.

• Monopropellants have been used as fuel sources but never with proportional force or motion control of robotic actuators.

Technology Description

The invention uses a monopropellant powered actuator to increase the energetic performance of the system to ten times that of the state-of-the-art battery/servomotor combination. The system uses monopropellant or hypergolic liquids (H2O2 or HAN based fuels) to power any fluid-powered actuator. The increase in energetic performance of the system leads to extended run time and efficiency, increasing the usefulness of machines such as self-powered robots. Although a variety of configurations are possible, the system commonly consists of a blow down fuel tank that delivers fuel to a catalyst producing a gaseous product. Proportional valves control the gas flow to the actuator, actuating the piston and powering the system in a highly controlled manner.

Commercial Applications

• Powering untethered mobile robotic actuators

• Creating controllable forces on actuators with centralized or distributed monopropellant actuator systems

• Any self-powered application with a high energy and power density control actuator

Unique Properties and Competitive Advantages

• No pre-mixing, pre-compression or ignition

• Flow control occurs within the liquid state reducing energy loss

• Direct chemical to mechanical energy with 10x more energy and power densities than a battery

• In the application of untethered mobile robots it provides extended run time when performing human mechanical tasks, making the robot more efficient and effective

• Potential to be increased further with modification of the monopropellant fuel

Intellectual Property Status

US Patent 6,935,109 issued Aug 30, 2005.

For more information, demonstration videos, and related publications visit:

Michael GoldfarbJoseph WehrmeyerAlvin StraussEric Barth
Licensing manager: 
Ashok Choudhury

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