Analysis and hypothesis of Chang Heng Seismograph
Art and Science of Control Feedback
Jiaming Lu
Great inventions of science emerged from of old including varied scientific fields. Most of
them, for instance, contain principles and mechanism of Feedback Control. Invention of
many apparatus in the ancient contributed the development of those fields improvably.
An eximious device which was invented thousand years ago at about A.D.132 during the
Han dynasty in China is one of them. This earliest Seismograph invented in Ancient China
which is named by the inventor Chang Heng. It is the earliest instrument which could
detect the earthquake. The instrument staff could record the time and direction of an
earthquake immediately.
In 2PM May 12th, 2008, an unforeseen disaster was happened in a series of province in
china. Modern earthquake detecting device cannot still forecast the terrible earthquake
happened from the center of Si chuan province. Although this is developing subject, many
different device of earthquake including Electronic feedback short cycle seismograph
could research on Chang Heng Seismograph which was a mechanical system and
sensors combined control system as reference.
The mechanical device using the principles of inertia and pendency was made of fine
copper in the shape of a wine pot. There were eight dragons that mounted on the surface.
Heads of these dragons pointed out the eight directions of east, south, west, north,
northeast, southeast, northwest and southwest. Each dragon had a copper ball inside its
mouth and a frog squatting under its head. When an earthquake occurred, the mouth of
the dragon pointing in the direction of the earthquake would open automatically, and the
copper ball would fall into the mouth of the corresponding frog.
The detailed time and direction could be record when it detects the earthquake. The wave
signal which produced by the earthquake can be received and the instrument can give the
scientist a feedback to notice that which and when is the earthquake. In the ancient which
the information communication tech was really not advanced like it today, an apparatus
which has the ability of detecting the earthquake was need to provide the information of
the disaster to the court or government for the emergency policy to the disaster.
In A.D. 138, this seismograph accurately detected an earthquake that occurred in the
Longxi Shire. The seismograph Chang Heng invented was the first apparatus in the world
that could measure the direction of an earthquake, and this was 1700 years earlier than
the European seismograph.
In 2005. A Group in China Earthquake Networks Center (CENC) set by many professors
in different science areas including Mechanical Engineering ,Earthquake ,Dynamics ,etc.
rebuild the apparatus to prove the principle and made it a real scientific earthquake
detecting instrument. Scientists are discovering much more useful information from
Chang Heng seismograph which about Sensors, Control and feedback short cycle to
research and improve the earthquake detecting device today.
It was completely a complex system inside under the research of CENC. For one of them,
there was an inverse pillar which has high center of gravity inside. For it was unstable
while the wave signal of the earthquake came, the bottom of device probably pointed to
the center of the earthquake and in the inverse direction. Under the force of inertia，the
pillar came down to that direction. Lever inside could be spring and also drive the dragon
mouth.
Also, Seismographs are sensors and control based science devices. The 1st modern
seismograph was invented by Italian scientist pamela in 1855 which was a complex
electromagnetism instrument. The 1st accurate seismograph contained a small heavy
stick which will move when is shake came out in Japan,1880 by Great Britain Geography
Scientist John Millen. The instrument set an aperture to let the light come in the equipment
on a piece of special paper. After several improvement , most of the modern seismograph
will use the Electromagnetism and feedback short cycle as the research key.
Reference
1. Richter, C.F. (1958). Elementary Seismology. San Francisco: W.H. Freeman.
2. Sleeswyk AW, Sivin N (1983). "Dragons and toads: the Chinese seismoscope of BC.
132". Chinese Science 6: 1–19.
3. Needham, Joseph (1959). Science and Civilization in China, Volume 3: Mathematics
and the Sciences of the Heavens and the Earth. Cambridge: Cambridge University
Press. pp. 626–635.