The term has its origins in the era of the American New Deal during the 1930s as a result of the policies initiated by modern liberals, when many classical liberals started calling themselves conservatives as they did not wish to be identified with what was passing for liberalism in the United States. In the United States, the term liberalism has become associated with the welfare state and expanded regulatory policies created as a result of the New Deal and its offshoots from the 1930s onwards.
Fiscal conservatives form one of the three legs of the traditional American conservative movement that emerged during the 1950s together with social conservatism and national defense conservatism. Many Americans who are classical liberals also tend to identify as libertarian, holding more cultural liberal views and advocating a non-interventionist foreign policy while supporting lower taxes and less government spending. As of 2020, 39% of Americans polled considered themselves "economically conservative".
Because of its close proximity to the United States, the term has entered the lexicon in Canada. In many other countries, economic liberalism or simply liberalism is used to describe what Americans call fiscal conservatism.
In his Reflections on the Revolution in France, Edmund Burke
argued that a government does not have the right to run up large debts
and then throw the burden on the taxpayer, writing "it is to the
property of the citizen, and not to the demands of the creditor of the
state, that the first and original faith of civil society is pledged.
The claim of the citizen is prior in time, paramount in title, superior
in equity. The fortunes of individuals, whether possessed by acquisition
or by descent or in virtue of a participation in the goods of some
community, were no part of the creditor's security, expressed or
implied. ... [T]he public, whether represented by a monarch or by a
senate, can pledge nothing but the public estate; and it can have no
public estate except in what it derives from a just and proportioned
imposition upon the citizens at large".
Factions or subgroups
Although
all fiscal conservatives agree generally on a smaller and less
expensive government, there are disagreements over priorities. There are three main factions or subgroups, each advocating for a particular emphasis. Deficit hawks
emphasize balancing government budgets and reducing the size of
government debt, viewing government debt as economically damaging and
morally dubious since it passes on obligations on to future generations
who have played no part in present-day tax and spending decisions.
Deficit hawks are willing to consider tax increases if the additional
revenue is used to reduce debt rather than increase spending.
A second group put their main emphasis on tax cuts rather than spending cuts or debt reduction. Many embrace supply-side economics,
arguing that as high taxes discourage economic activity and investment,
tax cuts would result in economic growth leading in turn to higher
government revenues.
According to them, these additional government revenues would reduce
the debt in the long term. They also argue for reducing taxes even if it
were to lead to short term increases in the deficit. Some supply-siders have advocated that the increases in revenue through tax cuts make drastic cuts in spending unnecessary. However, the Congressional Budget Office
has consistently reported that income tax cuts increase deficits and
debt and do not pay for themselves. For example, the CBO estimated that
the Bush tax cuts added about $1.5 trillion to deficits and debt from 2002 to 2011
and it would have added nearly $3 trillion to deficits and debt over
the 2010–2019 decade if fully extended at all income levels.
A third group makes little distinction between debt and taxes. This group emphasizes reduction in spending rather than tax policy or debt reduction. They argue that the true cost of government is the level of spending not how that spending is financed.
Every dollar that the government spends is a dollar taken from workers,
regardless of whether it is from debt or taxes. Taxes simply
redistribute purchasing power; it does so in a particularly inefficient
manner, reducing the incentives to produce or hire and borrowing simply
forces businesses and investors to anticipate higher taxes later on.
History
Classical liberalism
Classical liberalism in the United States
forms the historical foundation for modern fiscal conservatism.
Kathleen G. Donohue argues that classical liberalism in the 19th century
United States was distinct from its counterpart in Britain:
[A]t the center of classical liberal theory [in Europe] was the idea of laissez-faire. To the vast majority of American classical liberals, however, laissez-faire
did not mean no government intervention at all. On the contrary, they
were more than willing to see government provide tariffs, railroad
subsidies, and internal improvements, all of which benefited producers.
What they condemned was intervention in behalf of consumers.
In the early 20th century, fiscal conservatives were often at odds with progressives who desired economic reform. During the 1920s, RepublicanPresidentCalvin Coolidge's pro-business economic policies were credited for the successful period of economic growth known as the Roaring Twenties. However, his actions may have been due more to a sense of federalism than fiscal conservatism as Robert Sobel
notes: "As Governor of Massachusetts, Coolidge supported wages and
hours legislation, opposed child labor, imposed economic controls during
World War I, favored safety measures in factories, and even worker
representation on corporate boards".
Herbert Hoover addresses a large crowd in his 1932 presidential campaign.
Contrary to popular opinion, then-Republican President Herbert Hoover was not a fiscal conservative. He promoted government intervention during the early Great Depression, a policy that his successor, Democratic President Franklin D. Roosevelt, continued and increased despite campaigning to the contrary. Coolidge's economic policies are often popularly contrasted with the New Deal
deficit spending of Roosevelt and Republican Party opposition to
Roosevelt's government spending was a unifying cause for a significant
caucus of Republicans through even the presidencies of Harry S. Truman and Dwight D. Eisenhower. Barry Goldwater was a famous champion of both the socially and fiscally conservative Republicans.
In 1977, Democratic President Jimmy Carter appointed Alfred E. Kahn, a professor of economics at Cornell University, to be chair of the Civil Aeronautics Board (CAB). He was part of a push for deregulation
of the industry, supported by leading economists, leading think tanks
in Washington, a civil society coalition advocating the reform
(patterned on a coalition earlier developed for the
truck-and-rail-reform efforts), the head of the regulatory agency,
Senate leadership, the Carter administration and even some in the airline industry. This coalition swiftly gained legislative results in 1978.
The Airline Deregulation Act (Pub.L.95–504) was signed into law by President Carter on October 24, 1978. The main purpose of the act was to remove government control over fares, routes and market entry of new airlines from commercial aviation.
The CAB's powers of regulation were to be phased out, eventually
allowing market forces to determine routes and fares. The Act did not
remove or diminish the Federal Aviation Administration's regulatory powers over all aspects of airline safety.
In 1979, Carter deregulated the American beer industry by making it legal to sell malt, hops and yeast to American home brewers for the first time since the effective 1920 beginning of Prohibition in the United States.
This Carter deregulation led to an increase in home brewing over the
1980s and 1990s that by the 2000s had developed into a strong craft microbrew
culture in the United States, with 3,418 micro breweries, brewpubs and
regional craft breweries in the United States by the end of 2014.
Ronald Reagan spent the most of any recent President (Carter to Obama) as measured by annual average percentage of the GDP.
Fiscal conservatism was rhetorically promoted during the presidency of Republican Ronald Reagan (1981–1989). During Reagan's tenure, the top personal income tax bracket dropped from 70% to 28% while payroll taxes and the effective tax rates on the lower two income quintiles increased.
Reagan cut the maximum capital gains tax from 28% to 20%, though in his
second term he raised it back up to 28%. He successfully increased
defense spending, but conversely liberal Democrats blocked his efforts
to cut domestic spending. Real GDP growth recovered strongly after the 1982 recession, growing at an annual rate of 3.4% for the rest of his time in office.
Unemployment dropped after peaking at over 10.7% percent in 1982, and
inflation decreased significantly. Federal tax receipts nearly doubled
from $517 billion in 1980 to $1,032 billion in 1990. Employment grew at
about the same rate as population.
According to a United States Department of the Treasury
nonpartisan economic study, the major tax bills enacted under Reagan
caused federal revenue to fall by an amount equal to roughly 1% of GDP.
Although Reagan did not offset the increase in federal government
spending or reduce the deficit, his accomplishments are more notable
when expressed as a percent of the gross domestic product. Federal
spending fell from 22.2% of the GDP to 21.2%.
By the end of Reagan's second term, the national debt held by the
public increased by almost 60% and the total debt equalled $2.6
trillion. In fewer than eight years, the United States went from being
the world's largest creditor nation to the world's largest debtor
nation.
In the 1992 presidential election, Ross Perot,
a successful American businessman, ran as a third-party candidate.
Despite significant campaign stumbles and the uphill struggles involved
in mounting a third-party candidacy, Perot received 18.9% of the popular
vote (the largest percentage of any third-party candidate in modern
history), largely on the basis of his central platform plank of
limited-government, balanced-budget fiscal conservatism.
While the mantle of fiscal conservatism is most commonly claimed by Republicans and libertarians, it is also claimed in some ways by many centrist or moderateDemocrats who often refer to themselves as New Democrats. Although not supportive of the wide range tax cut policies that were often enacted during the Reagan and Bush administrations,
the New Democrat coalition's primary economic agenda differed from the
traditional philosophy held by liberal Democrats and sided with the
fiscal conservative belief that a balanced federal budget should take
precedence over some spending programs.
Former President Bill Clinton, who was a New Democrat and part of the somewhat fiscally conservative Third Way advocating Democratic Leadership Council,
is a prime example of this as his administration along with the
Democratic-majority congress of 1993 passed on a party-line vote the Omnibus Budget Reconciliation Act of 1993
which cut government spending, created a 36% individual income tax
bracket, raised the top tax bracket which encompassed the top 1.2%
earning taxpayers from 31% to 39.6% and created a 35% income tax rate
for corporations.
The 1993 Budget Act also cut taxes for fifteen million low-income
families and 90% of small businesses. Additionally during the Clinton
years, the PAYGO (pay-as-you-go) system originally introduced with the passing of the Budget Enforcement Act of 1990
(which required that all increases in direct spending or revenue
decreases be offset by other spending decreases or revenue increases and
was very popular with deficit hawks) had gone into effect and was used regularly until the system's expiration in 2002.
After this combination of tax hikes and spending reductions, the United States was able to create budget surpluses from fiscal years 1998–2001 (the first time since 1969) and the longest period of sustained economic growth in United States history.
Modern fiscal conservatism
Comparison
of annual federal deficits (CBO 10-year forecast from prior to
inauguration vs. the actual amount) during the Obama and Bush
presidencies showcasing how George W. Bush added far more to the debt relative to the CBO 2001 forecast than Obama added relative to the CBO 2009 forecast
To me, fiscal conservatism means balancing budgets – not
running deficits that the next generation can't afford. It means
improving the efficiency of delivering services by finding innovative
ways to do more with less. It means cutting taxes when possible and
prudent to do so, raising them overall only when necessary to balance
the budget, and only in combination with spending cuts. It means when
you run a surplus, you save it; you don't squander it. And most
importantly, being a fiscal conservative means preparing for the
inevitable economic downturns – and by all indications, we've got one
coming.
While the term "fiscal conservatism" would imply budget deficits
would be lower under conservatives (i.e., Republicans), this has not
historically been the case. Economists Alan Blinder and Mark Watson reported
in 2016 that budget deficits since WW2 tended to be smaller under
Democratic Party presidents, at 2.1% potential GDP versus 2.8% potential
GDP for Republican presidents, a difference of about 0.7% GDP. They
wrote that higher budget deficits should theoretically have boosted the
economy more for Republicans, and therefore cannot explain the greater
GDP growth under Democrats.
Rest of the world
As
a result of the expansion of the welfare state and increased regulatory
policies by the Roosevelt administration beginning in the 1930s, in the
United States the term liberalism has today become associated with
modern rather than classical liberalism. In Western Europe, the expanded welfare states created after World War II were created by socialist or social-democratic parties such as the British Labour Party rather than liberal parties. Many liberal parties in Western Europe tend to adhere to classical liberalism, with the Free Democratic Party in Germany being one example. The Liberal Democrats in the United Kingdom have a classical liberal and a social liberal wing of the party. In many countries, liberalism or economic liberalism is used to describe what Americans call fiscal conservatism.
Fiscal conservatism in the United Kingdom was arguably most popular during the premiership of ConservativeMargaret Thatcher.
After a number of years of deficit spending under the previous Labour
government, Thatcher advocated spending cuts and selective tax increases
to balance the budget. As a result of the deterioration in the United
Kingdom's public finances—according to fiscal conservatives caused by
another spate of deficit spending under the previous Labour government,
the late-2000s recession and by the European sovereign debt crisis—the Cameron–Clegg coalition (Conservative–Liberal Democrats) embarked on an austerity programme featuring a combination of spending cuts and tax rises in an attempt to halve the deficit and eliminate the structural deficit over the five-year parliament.
The term is sometimes used in South Korea, where left-liberal Democratic Party of Korea (DPK) and conservative People Power Party (PPP) are the two main parties. Fiscal conservatism is mainly represented by PPP. South Korea's current president, Yoon Suk-yeol, is known as a "fiscal conservative".
A plutocracy (from Ancient Greekπλοῦτος (ploûtos) 'wealth', and κράτος (krátos) 'power') or plutarchy is a society that is ruled or controlled by people of great wealth or income. The first known use of the term in English dates from 1631. Unlike most political systems, plutocracy is not rooted in any established political philosophy.
Usage
The term plutocracy is generally used as a pejorative to describe or warn against an undesirable condition. Throughout history, political thinkers and philosophers have condemned plutocrats for ignoring their social responsibilities, using their power to serve their own purposes and thereby increasing poverty and nurturing class conflict and corrupting societies with greed and hedonism.
One modern, formal example of a plutocracy, according to some critics, is the City of London. The City (also called the Square Mile of ancient London, corresponding to the modern financial district, an area of about 2.5 km2) has a unique electoral system for its local administration,
separate from the rest of London. More than two-thirds of voters are
not residents, but rather representatives of businesses and other bodies
that occupy premises in the City, with votes distributed according to
their numbers of employees. The principal justification for this
arrangement is that most of the services provided by the City of London
Corporation are used by the businesses in the City. Around 450,000
non-residents constitute the city's day-time population, far
outnumbering the City's 7,000 residents.
Some modern historians, politicians, and economists argue that the U.S. was effectively plutocratic for at least part of the Gilded Age and Progressive Era periods between the end of the Civil War until the beginning of the Great Depression. President Theodore Roosevelt became known as the "trust-buster" for his aggressive use of antitrust law, through which he managed to break up such major combinations as the largest railroad and Standard Oil, the largest oil company. According to historian David Burton, "When it came to domestic political concerns, TR's bête noire was the plutocracy." In his autobiographical account of taking on monopolistic corporations as president, Roosevelt recounted:
...we had come to the stage where for our people what was needed was a
real democracy; and of all forms of tyranny the least attractive and
the most vulgar is the tyranny of mere wealth, the tyranny of a
plutocracy.
The Sherman Antitrust Act had been enacted in 1890, when large industries reaching monopolistic or near-monopolistic levels of market concentration and financial capital
increasingly integrating corporations and a handful of very wealthy
heads of large corporations began to exert increasing influence over
industry, public opinion and politics after the Civil War. Money,
according to contemporary progressive and journalist Walter Weyl, was "the mortar of this edifice", with ideological differences among politicians fading and the political realm becoming "a mere branch
in a still larger, integrated business. The state, which through the
party formally sold favors to the large corporations, became one of
their departments."
In "The Politics of Plutocracy" section of his book, The Conscience of a Liberal, economist Paul Krugman
says plutocracy took hold because of three factors: at that time, the
poorest quarter of American residents (African-Americans and
non-naturalized immigrants) were ineligible to vote, the wealthy funded
the campaigns of politicians they preferred, and vote buying was "feasible, easy and widespread", as were other forms of electoral fraud such as ballot-box stuffing and intimidation of the other party's voters.
The U.S. instituted progressive taxation in 1913, but according to Shamus Khan,
in the 1970s, elites used their increasing political power to lower
their taxes, and today successfully employ what political scientist
Jeffrey Winters calls "the income defense industry" to greatly reduce
their taxes.
In 1998, Bob Herbert of The New York Times referred to modern American plutocrats as "The Donor Class" (list of top donors) and defined the class, for the first time,
as "a tiny group – just one-quarter of 1 percent of the population –
and it is not representative of the rest of the nation. But its money
buys plenty of access."
Post-World War II
In
modern times, the term is sometimes used pejoratively to refer to
societies rooted in state-corporate capitalism or which prioritize the
accumulation of wealth over other interests. According to Kevin Phillips, author and political strategist to Richard Nixon, the United States is a plutocracy in which there is a "fusion of money and government."
Chrystia Freeland, author of Plutocrats, says that the present trend towards plutocracy occurs because the rich feel that their interests are shared by society:
You don't do this in a kind of
chortling, smoking your cigar, conspiratorial thinking way. You do it by
persuading yourself that what is in your own personal self-interest is
in the interests of everybody else. So you persuade yourself that,
actually, government services, things like spending on education, which
is what created that social mobility in the first place, need to be cut
so that the deficit will shrink, so that your tax bill doesn't go up.
And what I really worry about is, there is so much money and so much
power at the very top, and the gap between those people at the very top
and everybody else is so great, that we are going to see social mobility
choked off and society transformed.
When the Nobel Prize–winning economist Joseph Stiglitz wrote the 2011 Vanity Fair
magazine article entitled "Of the 1%, by the 1%, for the 1%", the title
and content supported Stiglitz's claim that the U.S. is increasingly
ruled by the wealthiest 1%. Some researchers have said the U.S. may be drifting towards a form of oligarchy, as individual citizens have less impact than economic elites and organized interest groups upon public policy. A study conducted by political scientists Martin Gilens of Princeton University and Benjamin Page of Northwestern University, which was released in April 2014,
stated that their "analyses suggest that majorities of the American
public actually have little influence over the policies our government
adopts". Gilens and Page do not characterize the U.S. as an "oligarchy"
or "plutocracy" per se; however, they do apply the concept of "civil
oligarchy" as used by Jeffrey A. Winters with respect to the U.S.
The investor, billionaire, and philanthropistWarren Buffett, one of the wealthiest people in the world,
voiced in 2005 and once more in 2006 his view that his class, the "rich
class", is waging class warfare on the rest of society. In 2005 Buffet
said to CNN: "It's class warfare, my class is winning, but they
shouldn't be." In a November 2006 interview in The New York Times,
Buffett stated that "[t]here's class warfare all right, but it's my
class, the rich class, that's making war, and we're winning."
Causation
Reasons why a plutocracy develops are complex. In a nation that is experiencing rapid economic growth, income inequality will tend to increase as the rate of return on innovation increases. In other scenarios, plutocracy may develop when a country is collapsing due to resource depletion as the elites attempt to hoard the diminishing wealth or expand debts to maintain stability, which will tend to enrich creditors and financiers.
Economists have also suggested that free market economies tend to drift
into monopolies and oligopolies because of the greater efficiency of
larger businesses (see economies of scale).
Modular self-reconfiguring robotic systems or self-reconfigurable modular robots are autonomous kinematic machines
with variable morphology. Beyond conventional actuation, sensing and
control typically found in fixed-morphology robots, self-reconfiguring
robots are also able to deliberately change their own shape by
rearranging the connectivity of their parts, in order to adapt to new
circumstances, perform new tasks, or recover from damage.
For example, a robot made of such components could assume a worm-like shape to move through a narrow pipe, reassemble into something with spider-like
legs to cross uneven terrain, then form a third arbitrary object (like a
ball or wheel that can spin itself) to move quickly over a fairly flat
terrain; it can also be used for making "fixed" objects, such as walls,
shelters, or buildings.
In some cases this involves each module having 2 or more connectors for connecting several together. They can contain electronics, sensors, computer processors, memory and power supplies; they can also contain actuators
that are used for manipulating their location in the environment and in
relation with each other. A feature found in some cases is the ability
of the modules to automatically connect and disconnect themselves to and
from each other, and to form into many objects or perform many tasks
moving or manipulating the environment.
By saying "self-reconfiguring" or "self-reconfigurable" it means
that the mechanism or device is capable of utilizing its own system of
control such as with actuators or stochastic
means to change its overall structural shape. Having the quality of
being "modular" in "self-reconfiguring modular robotics" is to say that
the same module or set of modules can be added to or removed from the
system, as opposed to being generically "modularized" in the broader
sense. The underlying intent is to have an indefinite number of
identical modules, or a finite and relatively small set of identical
modules, in a mesh or matrix structure of self-reconfigurable modules.
Self-reconfiguration is different from the concept of self-replication,
which is not a quality that a self-reconfigurable module or collection
of modules needs to possess. A matrix of modules does not need to be
able to increase the quantity of modules in its matrix to be considered
self-reconfigurable. It is sufficient for self-reconfigurable modules to
be produced at a conventional factory, where dedicated machines stamp
or mold components that are then assembled
into a module, and added to an existing matrix in order to supplement
it to increase the quantity or to replace worn out modules.
A matrix made up of many modules can separate to form multiple
matrices with fewer modules, or they can combine, or recombine, to form a
larger matrix. Some advantages of separating into multiple matrices
include the ability to tackle multiple and simpler tasks at locations
that are remote from each other simultaneously, transferring through
barriers with openings that are too small for a single larger matrix to
fit through but not too small for smaller matrix fragments or individual
modules, and energy saving purposes by only utilizing enough modules to
accomplish a given task. Some advantages of combining multiple
matrices into a single matrix is ability to form larger structures such
as an elongated bridge, more complex structures such as a robot with
many arms or an arm with more degrees of freedom, and increasing
strength. Increasing strength, in this sense, can be in the form of
increasing the rigidity of a fixed or static structure, increasing the
net or collective amount of force for raising, lowering, pushing, or
pulling another object, or another part of the matrix, or any
combination of these features.
There are two basic methods of segment articulation that
self-reconfigurable mechanisms can utilize to reshape their structures:
chain reconfiguration and lattice reconfiguration.
Structure and control
Modular
robots are usually composed of multiple building blocks of a relatively
small repertoire, with uniform docking interfaces that allow transfer
of mechanical forces and moments, electrical power and communication
throughout the robot.
The modular building blocks usually consist of some primary
structural actuated unit, and potentially additional specialized units
such as grippers, feet, wheels, cameras, payload and energy storage and
generation.
A taxonomy of architectures
Modular
self-reconfiguring robotic systems can be generally classified into
several architectural groups by the geometric arrangement of their unit
(lattice vs. chain). Several systems exhibit hybrid properties, and
modular robots have also been classified into the two categories of
Mobile Configuration Change (MCC) and Whole Body Locomotion (WBL).
Lattice
architecture: 12 modules of the homogeneous lattice system Micro Unit
assembled together shown with corresponding grid and docking points
network
Lattice architecture have their units connecting their
docking interfaces at points into virtual cells of some regular grid.
This network of docking points can be compared to atoms in a crystal and
the grid to the lattice of that crystal. Therefore, the kinematical
features of lattice robots can be characterized by their corresponding
crystallographic displacement groups (chiral space groups).
Usually few units are sufficient to accomplish a reconfiguration step.
Lattice architectures allows a simpler mechanical design and a simpler
computational representation and reconfiguration planning that can be
more easily scaled to complex systems.
Chain architecture do not use a virtual network of docking
points for their units. The units are able to reach any point in the
space and are therefore more versatile, but a chain of many units may be
necessary to reach a point making it usually more difficult to
accomplish a reconfiguration step. Such systems are also more
computationally difficult to represent and analyze.
Hybrid architecture takes advantages of both previous
architectures. Control and mechanism are designed for lattice
reconfiguration but also allow to reach any point in the space.
Modular robotic systems can also be classified according to the way by which units are reconfigured (moved) into place.
Deterministic reconfiguration relies on units moving or
being directly manipulated into their target location during
reconfiguration. The exact location of each unit is known at all times.
Reconfiguration times can be guaranteed, but sophisticated feedback
control is necessary to assure precise manipulation. Macro-scale systems
are usually deterministic.
Stochastic reconfiguration relies on units moving around
using statistical processes (like Brownian motion). The exact location
of each unit only known when it is connected to the main structure, but
it may take unknown paths to move between locations. Reconfiguration
times can be guaranteed only statistically. Stochastic architectures are
more favorable at micro scales.
Modular robotic systems are also generally classified depending on the design of the modules.
Homogeneous modular robot systems have many modules of
the same design forming a structure suitable to perform the required
task. An advantage over other systems is that they are simple to scale
in size (and possibly function), by adding more units. A commonly
described disadvantage is limits to functionality - these systems often
require more modules to achieve a given function, than heterogeneous
systems.
Heterogeneous modular robot systems have different modules,
each of which do specialized functions, forming a structure suitable to
perform a task. An advantage is compactness, and the versatility to
design and add units to perform any task. A commonly described
disadvantage is an increase in complexity of design, manufacturing, and
simulation methods.Conceptual representation for intra-, inter- and nested-reconfiguration under taxonomy of reconfigurable robots
Other modular robotic systems exist which are not
self-reconfigurable, and thus do not formally belong to this family of
robots though they may have similar appearance. For example, self-assembling
systems may be composed of multiple modules but cannot dynamically
control their target shape. Similarly, tensegrity robotics may be
composed of multiple interchangeable modules but cannot
self-reconfigure. Self-reconfigurable robotic systems feature
reconfigurability compared to their fixed-morphology counterparts and it
can be defined as the extent/degree to which a self-reconfigurable
robot or robotic systems can transform and evolve to another meaningful
configuration with a certain degree of autonomy or human intervention. The reconfigurable system can also be classified according to the mechanism reconfigurability.
Intra-reconfigurability for robots is referred as a
system that is a single entity while having ability to change morphology
without the assembly/disassembly.
Inter-reconfigurability is defined as to what extent a
robotic system can change its morphology through assembling or
disassembling its components or modules.
Nested-reconfigurability for robotic system is a set of
modular robots with individual reconfiguration characteristics
(intra-reconfigurability) that combine with other homogeneous or
heterogeneous robot modules (inter-reconfigurability).
Motivation and inspiration
There are two key motivations for designing modular self-reconfiguring robotic systems.
Functional advantage: Self reconfiguring robotic systems are potentially more robust and more adaptive
than conventional systems. The reconfiguration ability allows a robot
or a group of robots to disassemble and reassemble machines to form new
morphologies that are better suitable for new tasks, such as changing
from a legged robot to a snake robot (snakebot)
and then to a rolling robot. Since robot parts are interchangeable
(within a robot and between different robots), machines can also replace
faulty parts autonomously, leading to self-repair.
Autonomous modular robotics in space
Economic advantage: Self reconfiguring robotic systems
can potentially lower overall robot cost by making a range of complex
machines out of a single (or relatively few) types of mass-produced
modules.
Both these advantages have not yet been fully realized. A modular
robot is likely to be inferior in performance to any single custom robot
tailored for a specific task. However, the advantage of modular
robotics is only apparent when considering multiple tasks that would
normally require a set of different robots.
The added degrees of freedom make modular robots more versatile
in their potential capabilities, but also incur a performance tradeoff
and increased mechanical and computational complexities.
The quest for self-reconfiguring robotic structures is to some
extent inspired by envisioned applications such as long-term space
missions, that require long-term self-sustaining robotic ecology that
can handle unforeseen situations and may require self repair. A second
source of inspiration are biological systems that are self-constructed
out of a relatively small repertoire of lower-level building blocks
(cells or amino acids, depending on scale of interest). This
architecture underlies biological systems' ability to physically adapt,
grow, heal, and even self replicate – capabilities that would be
desirable in many engineered systems.
Application areas
Given
these advantages, where would a modular self-reconfigurable system be
used? While the system has the promise of being capable of doing a wide
variety of things, finding the "killer application" has been somewhat elusive. Here are several examples:
Space exploration
One application that highlights the advantages of self-reconfigurable systems is long-term space missions.
These require long-term self-sustaining robotic ecology that can handle
unforeseen situations and may require self repair. Self-reconfigurable
systems have the ability to handle tasks that are not known a priori,
especially compared to fixed configuration systems. In addition, space
missions are highly volume- and mass-constrained. Sending a robot system
that can reconfigure to achieve many tasks may be more effective than
sending many robots that each can do one task.
Telepario
Another
example of an application has been coined "telepario" by CMU professors
Todd Mowry and Seth Goldstein. What the researchers propose to make are
moving, physical,
three-dimensional replicas of people or objects, so lifelike that human
senses would accept them as real. This would eliminate the need for
cumbersome virtual reality gear and overcome the viewing angle
limitations of modern 3D approaches. The replicas would mimic the shape
and appearance of a person or object being imaged in real time, and as
the originals moved, so would their replicas. One aspect of this
application is that the main development thrust is geometric
representation rather than applying forces to the environment as in a
typical robotic manipulation task. This project is widely known as
claytronics or Programmable matter (noting that programmable matter is a much more general term, encompassing functional programmable materials, as well).
Bucket of stuff
A
third long-term vision for these systems has been called "bucket of
stuff", which would be a container filled with modular robots that can
accept user commands and adopt an appropriate form in order to complete
household chores.
History and state of the art
The
roots of the concept of modular self-reconfigurable robots can be
traced back to the "quick change" end effector and automatic tool
changers in computer numerical controlled machining centers in the
1970s. Here, special modules each with a common connection mechanism
could be automatically swapped out on the end of a robotic arm. However,
taking the basic concept of the common connection mechanism and
applying it to the whole robot was introduced by Toshio Fukuda with the
CEBOT (short for cellular robot) in the late 1980s.
The early 1990s saw further development from Gregory S. Chirikjian,
Mark Yim, Joseph Michael, and Satoshi Murata. Chirikjian, Michael, and
Murata developed lattice reconfiguration systems and Yim developed a
chain based system. While these researchers started with a mechanical
engineering emphasis, designing and building modules then developing
code to program them, the work of Daniela Rus and Wei-min Shen developed
hardware but had a greater impact on the programming aspects. They
started a trend towards provable or verifiable distributed algorithms
for the control of large numbers of modules.
One of the more interesting hardware platforms recently has been
the MTRAN II and III systems developed by Satoshi Murata et al. This
system is a hybrid chain and lattice system. It has the advantage of
being able to achieve tasks more easily like chain systems, yet
reconfigure like a lattice system.
More recently new efforts in stochastic self-assembly have been pursued by Hod Lipson and Eric Klavins. A large effort at Carnegie Mellon University headed by Seth Goldstein and Todd Mowry has started looking at issues in developing millions of modules.
Many tasks have been shown to be achievable, especially with
chain reconfiguration modules. This demonstrates the versatility of
these systems however, the other two advantages, robustness and low cost
have not been demonstrated. In general the prototype systems developed
in the labs have been fragile and expensive as would be expected during
any initial development.
There is a growing number of research groups actively involved in
modular robotics research. To date, about 30 systems have been designed
and constructed, some of which are shown below.
A chain self-reconfiguration system. Each module is about 50 mm on a
side, and has 1 rotational DOF. It is part of the PolyBot modular robot
family that has demonstrated many modes of locomotion including walking:
biped, 14 legged, slinky-like, snake-like: concertina in a gopher hole,
inchworm gaits, rectilinear undulation and sidewinding gaits, rolling
like a tread at up to 1.4 m/s, riding a tricycle, climbing: stairs,
poles pipes, ramps etc. More information can be found at the polybot
webpage at PARC.
Metamorphosis by a self-reconfigurable robot, M-TRAN III
M-TRAN III (2005)
A hybrid type self-reconfigurable system. Each module is two cube
size (65 mm side), and has 2 rotational DOF and 6 flat surfaces for
connection. It is the 3rd M-TRAN prototypes. Compared with the former
(M-TRAN II), speed and reliability of connection is largely improved. As
a chain type system, locomotion by CPG (Central Pattern Generator)
controller in various shapes has been demonstrated by M-TRAN II. As a
lattice type system, it can change its configuration, e.g., between a 4
legged walker to a caterpillar like robot. See the M-TRAN webpage at
AIST.
AMOEBA-I (2005)
AMOEBA-I, a three-module reconfigurable mobile robot was developed in
Shenyang Institute of Automation (SIA), Chinese Academy of Sciences
(CAS) by Liu J G et al. AMOEBA-I
has nine kinds of non-isomorphic configurations and high mobility under
unstructured environments. Four generations of its platform have been
developed and a series of researches have been carried out on their
reconfiguration mechanism, non-isomorphic configurations, tipover
stability, and reconfiguration planning. Experiments have demonstrated
that such kind structure permits good mobility and high flexibility to
uneven terrain. Being hyper-redundant, modularized and reconfigurable,
AMOEBA-I has many possible applications such as Urban Search and Rescue
(USAR) and space exploration.
Stochastic-3D (2005)
High spatial resolution for arbitrary three-dimensional shape
formation with modular robots can be accomplished using lattice system
with large quantities of very small, prospectively microscopic modules.
At small scales, and with large quantities of modules, deterministic
control over reconfiguration of individual modules will become
unfeasible, while stochastic mechanisms will naturally prevail.
Microscopic size of modules will make the use of electromagnetic
actuation and interconnection prohibitive, as well, as the use of
on-board power storage.
Three large scale prototypes were built in attempt to demonstrate
dynamically programmable three-dimensional stochastic reconfiguration
in a neutral-buoyancy environment. The first prototype used
electromagnets for module reconfiguration and interconnection. The
modules were 100 mm cubes and weighed 0.81 kg. The second prototype used
stochastic fluidic reconfiguration and interconnection mechanism. Its
130 mm cubic modules weighed 1.78 kg each and made reconfiguration
experiments excessively slow. The current third implementation inherits
the fluidic reconfiguration principle. The lattice grid size is 80 mm,
and the reconfiguration experiments are under way.
This hybrid self-reconfiguring system was built by the Cornell
Computational Synthesis Lab to physically demonstrate artificial
kinematic self-reproduction. Each module is a 0.65 kg cube with 100 mm
long edges and one rotational degree of freedom. The axis of rotation is
aligned with the cube's longest diagonal. Physical self-reproduction of
both a three- and a four-module robot was demonstrated.
It was also shown that, disregarding the gravity constraints, an
infinite number of self-reproducing chain meta-structures can be built
from Molecubes. More information can be found at the Creative Machines Labself-replication page.
The Programmable Parts (2005)
The programmable parts are stirred randomly on an air-hockey
table by randomly actuated air jets. When they collide and stick, they
can communicate and decide whether to stay stuck, or if and when to
detach. Local interaction rules can be devised and optimized to guide
the robots to make any desired global shape. More information can be
found at the programmable parts web page.
The SuperBot modules fall into the hybrid architecture. The
modules have three degrees of freedom each. The design is based on two
previous systems: Conro (by the same research group) and MTRAN
(by Murata et al.). Each module can connect to another module through
one of its six dock connectors. They can communicate and share power
through their dock connectors. Several locomotion gaits have been
developed for different arrangements of modules. For high-level
communication the modules use hormone-based control, a distributed,
scalable protocol that does not require the modules to have unique ID's.
Miche (2006)
The Miche system is a modular lattice system capable of arbitrary
shape formation. Each module is an autonomous robot module capable of
connecting to and communicating with its immediate neighbors. When
assembled into a structure, the modules form a system that can be
virtually sculpted using a computer interface and a distributed process.
The group of modules collectively decide who is on the final shape and
who is not using algorithms that minimize the information transmission
and storage. Finally, the modules not in the structure let go and fall
off under the control of an external force, in this case gravity.
More details at Miche (Rus et al.).
A 10-module configuration of the Distributed Flight Array in flight
The Distributed Flight Array is a modular robot consisting of
hexagonal-shaped single-rotor units that can take on just about any
shape or form. Although each unit is capable of generating enough thrust
to lift itself off the ground, on its own it is incapable of flight
much like a helicopter cannot fly without its tail rotor. However, when
joined, these units evolve into a sophisticated multi-rotor system
capable of coordinated flight and much more. More information can be
found at DFA.
Roombots (2009)
Roombots
have a hybrid architecture. Each module has three degrees of freedom,
two of them using the diametrical axis within a regular cube, and a
third (center) axis of rotation connecting the two spherical parts. All
three axes are continuously rotatory. The outer Roombots DOF is using
the same axis-orientation as Molecubes, the third, central Roombots axis
enables the module to rotate its two outer DOF against each other. This
novel feature enables a single Roombots module to locomote on flat
terrain, but also to climb a wall, or to cross a concave, perpendicular
edge. Convex edges require the assembly of at least two modules into a
Roombots "Metamodule". Each module has ten available connector slots,
currently two of them are equipped with an active connection mechanism
based on mechanical latches.
Roombots are designed for two tasks: to eventually shape objects of
daily life, e.g. furniture, and to locomote, e.g. as a quadruped or a
tripod robot made from multiple modules.
More information can be found at Roombots webpage.
Sambot (2010)
Being inspired from social insects, multicellular organism and morphogenetic robots, the aim of the Sambot is to develop swarm robotics and conduct research on the swarm intelligence,
self-assembly and co-evolution of the body and brain for autonomous
morphogeneous. Differing from swarm robot, self-reconfigurable robot and
morphogenetic robot, the research focuses on self-assembly swarm
modular robots that interact and dock as an autonomous mobile module
with others to achieve swarm intelligence and furtherly discuss the
autonomous construction in space station and exploratory tools and
artificial complex structures. Each Sambot robot can run as an
autonomous individual in wheel and besides, using combination of the
sensors and docking mechanism, the robot can interact and dock with the
environments and other robots. By the advantage of motion and
connection, Sambot swarms can aggregate into a symbiotic or whole
organism and generate locomotion as the bionic articular robots. In this
case, some self-assembling, self-organizing, self-reconfiguring, and
self-repairing function and research are available in design and
application view. Inside the modular robot whose size is
80(W)X80(L)X102(H) mm, MCU (ARM and AVR), communication (Zigbee),
sensors, power, IMU, positioning modules are embedded.
More information can be found at "Self-assembly Swarm Modular Robots".
Motein
Moteins (2011)
It is mathematically proven that physical strings or chains of simple
shapes can be folded into any continuous area or volumetric shape.
Moteins employ such shape-universal folding strategies, with as few as
one (for 2D shapes) or two (for 3D shapes) degrees of freedom and simple
actuators with as few as two (for 2D shapes) or three (for 3D shapes)
states per unit.
Symbrion (2013)
Symbrion
(Symbiotic Evolutionary Robot Organisms) was a project funded by the
European Commission between 2008 and 2013 to develop a framework in
which a homogeneous swarm of miniature interdependent robots can
co-assemble into a larger robotic organism to gain problem-solving
momentum. One of the key aspects of Symbrion is inspired by the
biological world: an artificial genome that allows storing and evolution
of suboptimal configurations in order to increase the speed of
adaptation. A large part of the developments within Symbrion is
open-source and open-hardware.
Space Engine
is an autonomous kinematic platform with variable morphology, capable
of creating or manipulating the physical space (living space, work
space, recreation space). Generating its own multi-directional kinetic
force to manipulate objects and perform tasks.
At least 3 or more locks for each module, able the automatically
attach or detach to its immediate modules to form rigid structures.
Modules propel in a linear motion forward or backward alone X, Y or Z
spacial planes, while creates their own momentum forces, able to propel
itself by the controlled pressure variation created between one or more
of its immediate modules.
Using Magnetic pressures to attract and/or repel with its
immediate modules. While the propelling module use its electromagnets to
pull or push forward along the roadway created by The statistic
modules, the statistic modules pull or push the propelling modules
forward. Increasing the number of modular for displacement also
increases the total momentum or push/pull forces. The number of
Electromagnets on each module can change according to requirements of
the design.
The modules on the exterior of the matrices can't displace independently
on their own, due to lack of one or more reaction face from immediate
modules. They are moved by attaching to modules in the interior of the
matrices, that can form complete roadway for displacement.
Space Engine Displacement
Space Engine Displacement
Space Engine Zero-gravity cell design
Space Engine gravity cell design
Quantitative accomplishment
The robot with most active modules has 56 units <polybot centipede, PARC>
The smallest actuated modular unit has a size of 12 mm
The largest actuated modular unit (by volume) has the size of 8 m^3 <(GHFC)giant helium filled catoms, CMU>
The strongest actuation modules are able to lift 5 identical horizontally cantilevered units.<PolyBot g1v5, PARC>
The fastest modular robot can move at 23 unit-sizes/second.<CKbot, dynamic rolling, ISER'06>
The largest simulated system contained many hundreds of thousands of units.
Challenges, solutions, and opportunities
Since
the early demonstrations of early modular self-reconfiguring systems,
the size, robustness and performance has been continuously improving. In
parallel, planning and control algorithms have been progressing to
handle thousands of units. There are, however, several key steps that
are necessary for these systems to realize their promise of adaptability, robustness and low cost.
These steps can be broken down into challenges in the hardware design,
in planning and control algorithms and in application. These challenges
are often intertwined.
Hardware design challenges
The
extent to which the promise of self-reconfiguring robotic systems can
be realized depends critically on the numbers of modules in the system.
To date, only systems with up to about 50 units have been demonstrated,
with this number stagnating over almost a decade. There are a number of
fundamental limiting factors that govern this number:
Limits on strength, precision, and field robustness (both
mechanical and electrical) of bonding/docking interfaces between modules
Limits on motor power, motion precision and energetic efficiency of units, (i.e. specific power, specific torque)
Hardware/software design. Hardware that is designed to make the
software problem easier. Self-reconfiguring systems have more tightly
coupled hardware and software than any other existing system.
Planning and control challenges
Though
algorithms have been developed for handling thousands of units in ideal
conditions, challenges to scalability remain both in low-level control
and high-level planning to overcome realistic constraints:
Algorithms for parallel-motion for large scale manipulation and locomotion
Algorithms for robustly handling a variety of failure modes, from
misalignments, dead-units (not responding, not releasing) to units that
behave erratically.
Algorithms that determine the optimal configuration for a given task
Algorithms for optimal (time, energy) reconfiguration plan
Efficient and scalable (asynchronous) communication among multiple units
Application challenges
Though
the advantages of Modular self-reconfiguring robotic systems is largely
recognized, it has been difficult to identify specific application
domains where benefits can be demonstrated in the short term. Some
suggested applications are
Rapid construction of arbitrary tools under space/weight constraints
Disaster relief shelters for displaced peoples
Shelters for impoverished areas which require little on-the-ground expertise to assemble
Grand Challenges
Several robotic fields have identified Grand Challenges that act as a catalyst for development and serve as a short-term goal in absence of immediate killer apps.
The Grand Challenge is not in itself a research agenda or milestone,
but a means to stimulate and evaluate coordinated progress across
multiple technical frontiers. Several Grand Challenges have been
proposed for the modular self-reconfiguring robotics field:
Demonstration of a system with >1000 units. Physical
demonstration of such a system will inevitably require rethinking key
hardware and algorithmic issues, as well as handling noise and error.
Robosphere. A self-sustaining robotic ecology, isolated for a
long period of time (1 year) that needs to sustain operation and
accomplish unforeseen tasks without any human presence.
Self replication A system with many units capable of self
replication by collecting scattered building blocks will require solving
many of the hardware and algorithmic challenges.
Ultimate Construction A system capable of making objects out of the components of, say, a wall.
Biofilter analogy If the system is ever made small enough to
be injected into a mammal, one task may be to monitor molecules in the
blood stream and allow some to pass and others not to, somewhat like the
blood–brain barrier. As a challenge, an analogy may be made where system must be able to:
be inserted into a hole one module's diameter.
travel some specified distance in a channel that is say roughly 40 x 40 module diameters in area.
form a barrier fully conforming to the channel (whose shape is non-regular, and unknown beforehand).
allow some objects to pass and others not to (not based on size).
Since sensing is not the emphasis of this work, the actual detection of the passable objects should be made trivial.
Inductive transducers
A
unique potential solution that can be exploited is the use of inductors
as transducers. This could be useful for dealing with docking and
bonding problems. At the same time it could also be beneficial for its
capabilities of docking detection (alignment and finding distance),
power transmission, and (data signal) communication. A proof-of-concept
video can be seen
here.
The rather limited exploration down this avenue is probably a
consequence of the historical lack of need in any applications for such
an approach.
Modular Robotics Google Group
is an open public forum dedicated to announcements of events in the
field of Modular Robotics. This medium is used to disseminate calls to
workshops, special issues and other academic activities of interest to
modular robotics researchers. The founders of this Google group intend
it to facilitate the exchange of information and ideas within the
community of modular robotics researchers around the world and thus
promote acceleration of advancements in modular robotics. Anybody who is
interested in objectives and progress of Modular Robotics can join this
Google group and learn about the new developments in this field.
Websites dedicated specifically to exploring this technology
.jpg)
