Reciprocating Chemical Muscle
Encyclopedia
The Reciprocating Chemical Muscle (RCM) is a mechanism that takes advantage of the superior energy density
of chemical reactions. It is a regenerative device that converts chemical energy into motion through a direct noncombustive chemical reaction.
wing beating from a chemical energy source. It can also be used to provide a small amount of electricity to the onboard control systems. It further helps in differential lift enhancement on the wings to achieve roll, pitch, and hence, steered flight. The RCM technique is particularly useful in the manufacturing of insect-like MAVs
. The first generation of RCM was large and had a reciprocating frequency of approximately 10 Hz. The later generations developed were very much smaller and lighter. Also the reciprocating frequency of this generation RCM was as high as 60 Hz. The Reciprocating Chemical Muscle was invented by Prof. Robert C. Michelson
of the Georgia Tech Research Institute
and implemented up through its fourth generation by Nino Amarena of ETS Laboratories.
s in the presence of specific catalysts to create gas from a liquid without combustion
. This gas is used to drive reciprocating opposing cylinders (in the 4th generation device) to produce sufficient motion (throw) with sufficient force
and frequency
to allow flapping wing flight. As of 2004, the RCM had been demonstrated in the Georgia Tech Research Institute
laboratory to achieve sufficient throw, force, and frequency for operation of a 50 gram Entomopter
while using high concentration (> 90%) hydrogen peroxide
in the presence of a proprietary catalyst developed by ETS Laboratories.
. The RCM reuses energy many times before releasing it into its surroundings. First of all, it converts mainly heat energy into flapping wing motion in the Entomopter. Then heat is scavenged for thermoelectric generation in support of ancillary systems. Waste gas from the chemical decomposition of the fuel is then used to create an FMCW
(frequency modulated continuous wave) acoustic ranging signal that is Doppler
insensitive (used for obstacle avoidance). Waste gas is then passed through an ejector to entrain external atmospheric gases in order to increase mass flow and decrease waste gas temperature so that lower temperature components can be used down stream. Some waste gas is diverted into gas bearings for rotational and linear moving components. Finally remaining waste gas is vectored into the wings where it is used for circulation-controlled lift augmentation (Coanda Effect
). Any remaining gas can be used for vectored thrust, however if the gas budgets are correctly designed, there should be no extra gas beyond the circulation control points. The features of the RCM are tailored to the Entomopter
in order to conserve energy.
Energy density
Energy density is a term used for the amount of energy stored in a given system or region of space per unit volume. Often only the useful or extractable energy is quantified, which is to say that chemically inaccessible energy such as rest mass energy is ignored...
of chemical reactions. It is a regenerative device that converts chemical energy into motion through a direct noncombustive chemical reaction.
Function
RCM is capable of generating autonomicAutonomic Computing
Autonomic Computing refers to the self-managing characteristics of distributed computing resources, adapting to unpredictable changes whilst hiding intrinsic complexity to operators and users...
wing beating from a chemical energy source. It can also be used to provide a small amount of electricity to the onboard control systems. It further helps in differential lift enhancement on the wings to achieve roll, pitch, and hence, steered flight. The RCM technique is particularly useful in the manufacturing of insect-like MAVs
Micro air vehicle
A micro air vehicle , or micro aerial vehicle , is a class of unmanned aerial vehicles that has a size restriction and may be autonomous. Modern craft can be as small as 15 centimetres...
. The first generation of RCM was large and had a reciprocating frequency of approximately 10 Hz. The later generations developed were very much smaller and lighter. Also the reciprocating frequency of this generation RCM was as high as 60 Hz. The Reciprocating Chemical Muscle was invented by Prof. Robert C. Michelson
Robert C. Michelson
Robert C. Michelson is an American engineer and academic widely known for inventing the entomopter, a biologically inspired flapping-winged aerial robot, and for having established the International Aerial Robotics Competition. He has received degrees in electrical engineering from the Virginia...
of the Georgia Tech Research Institute
Georgia Tech Research Institute
The Georgia Tech Research Institute is the nonprofit applied research arm of the Georgia Institute of Technology in Atlanta, Georgia, United States...
and implemented up through its fourth generation by Nino Amarena of ETS Laboratories.
Benefits
Particular benefits of the RCM are that it:- requires no ignition source (thereby allowing it to work in explosive atmospheres),
- is anaerobicAnaerobic respirationAnaerobic respiration is a form of respiration using electron acceptors other than oxygen. Although oxygen is not used as the final electron acceptor, the process still uses a respiratory electron transport chain; it is respiration without oxygen...
(thereby allowing it to operate underwater or in oxygen-free environments such as the lower atmosphere of the planet MarsMarsMars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
), - thermoelectrically generates electrical energy from its own exothermic metabolism, and
- converts chemically-bound potential energy directly into kinetic energyKinetic energyThe kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
with greater energy densityEnergy densityEnergy density is a term used for the amount of energy stored in a given system or region of space per unit volume. Often only the useful or extractable energy is quantified, which is to say that chemically inaccessible energy such as rest mass energy is ignored...
than batteries.
Mechanism
The Reciprocating Chemical Muscle uses various monopropellantMonopropellant
Monopropellants are propellants composed of chemicals or mixtures of chemicals which can be stored in a single container with some degree of safety. While stable under defined storage conditions, they react very rapidly under certain other conditions to produce a large volume of energetic gases...
s in the presence of specific catalysts to create gas from a liquid without combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...
. This gas is used to drive reciprocating opposing cylinders (in the 4th generation device) to produce sufficient motion (throw) with sufficient force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
and frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
to allow flapping wing flight. As of 2004, the RCM had been demonstrated in the Georgia Tech Research Institute
Georgia Tech Research Institute
The Georgia Tech Research Institute is the nonprofit applied research arm of the Georgia Institute of Technology in Atlanta, Georgia, United States...
laboratory to achieve sufficient throw, force, and frequency for operation of a 50 gram Entomopter
Entomopter
The Entomopter is a multimode insect-like robot developed by Prof. Robert C. Michelson and his design team from the Georgia Tech Research Institute , University of Cambridge , ETS Labs and others. The name 'Entomopter' is derived from entomo + pteron...
while using high concentration (> 90%) hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
in the presence of a proprietary catalyst developed by ETS Laboratories.
Specific Uses
The Reciprocating Chemical Muscle was developed as a drive mechanism for the flapping wings of the EntomopterEntomopter
The Entomopter is a multimode insect-like robot developed by Prof. Robert C. Michelson and his design team from the Georgia Tech Research Institute , University of Cambridge , ETS Labs and others. The name 'Entomopter' is derived from entomo + pteron...
. The RCM reuses energy many times before releasing it into its surroundings. First of all, it converts mainly heat energy into flapping wing motion in the Entomopter. Then heat is scavenged for thermoelectric generation in support of ancillary systems. Waste gas from the chemical decomposition of the fuel is then used to create an FMCW
FMCW
Frequency Modulated Continuous-wave radar is a short range measuring radar set. This kind of radar is often used as “radar altimeter” to measure the exact height during the landing procedure of aircraft.- Technical introduction :...
(frequency modulated continuous wave) acoustic ranging signal that is Doppler
Doppler effect
The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...
insensitive (used for obstacle avoidance). Waste gas is then passed through an ejector to entrain external atmospheric gases in order to increase mass flow and decrease waste gas temperature so that lower temperature components can be used down stream. Some waste gas is diverted into gas bearings for rotational and linear moving components. Finally remaining waste gas is vectored into the wings where it is used for circulation-controlled lift augmentation (Coanda Effect
Coanda effect
The Coandă effect is the tendency of a fluid jet to be attracted to a nearby surface. The principle was named after Romanian aerodynamics pioneer Henri Coandă, who was the first to recognize the practical application of the phenomenon in aircraft development....
). Any remaining gas can be used for vectored thrust, however if the gas budgets are correctly designed, there should be no extra gas beyond the circulation control points. The features of the RCM are tailored to the Entomopter
Entomopter
The Entomopter is a multimode insect-like robot developed by Prof. Robert C. Michelson and his design team from the Georgia Tech Research Institute , University of Cambridge , ETS Labs and others. The name 'Entomopter' is derived from entomo + pteron...
in order to conserve energy.
External references
- Robert C. Michelson: Entomopter Project
- "Reciprocating Chemical Muscle (RCM) and Method for Using Same", U.S. Patent No. 6,446,909, September 10, 2002