Construction of a three–dimensional, large–scale shaking table and development of core technology

Summary Nonlinear signal‐based control (NSBC) is very powerful for controlling structural systems with parameter variations and has the advantage that the controllers can be designed using classical control theory and expressed by transfer functions. This report describes the first application of NSBC to shake table tests with nonlinear specimens and compares the performance of NSBC with that of a basic control approach that relies on the inverse transfer function of the controlled system. NSBC and the basic approach were numerically applied to shake table tests to excite a nonlinear single‐degree‐of‐freedom system with earthquake acceleration motion, considering the nonlinear specimen characteristics and estimation errors associated with the table dynamics. NSBC achieved excellent control with near 100% accuracy, whereas the basic approach provided insufficient control. Although inaccurate estimation of the pure time delay in the controlled system causes instability at the practice of NSBC, proper design of the nonlinear signal feedback controller prevented instability. In experimental examinations, controllers for the two approaches were designed on the basis of the table dynamics with/without a specimen, which were preliminarily identified by performing tests using a random wave with small amplitude excitations. With no specimen present, both approaches yielded the expected acceleration motion on the table with high accuracy. However, with the specimen present, only NSBC successfully achieved excellent control of the shake table with near 100% accuracy, whereas the basic approach did not because of the specimen nonlinearity. These results numerically and experimentally demonstrate the efficiency and practicality of NSBC for shake tables supporting nonlinear structures.

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“…which is the open-loop characteristic equation of Equation (9). When the suitable controller transfer functions in Equation (5)…”

Section: Stability Analysismentioning

confidence: 99%

“…E‐Defense is currently the largest three‐dimensional shake table in the world (size: 20 m × 15 m, maximum loading capacity: 12,000 kN). Over 80 full‐ or large‐scale experiments have been implemented since its commencement in 2005 .…”

Section: Introductionmentioning

confidence: 99%

Nonlinear signal‐based control for single‐axis shake tables supporting nonlinear structural systems

Enokida

Kajiwara

2019

Struct Control Health Monit

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“…Second, it is generally impossible to introduce realistic detail into a structural model, making it particularly dangerous to accept any non-linear effects as being relevant to the prototype; this, the fact that theoretical treatments of non-linearities are equally suspect, was one justification for the recent construction of the world's largest shaking table (1200T testpiece capacity and 0-15 Hz frequency range) at Miki City in Japan [4].…”

Section: Scale Effectsmentioning

confidence: 99%

The development of shaking tables–A historical note

Severn

2011

Earthq Engng Struct Dyn

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The earliest known shaking table, driven by hand-power, was constructed in Japan at the end of the 19th century. At the beginning of the 20th century developments had moved to the Stanford University in the U.S. with the introduction of an electric motor to produce a more refined oscillatory motion in one direction, the response of the testpiece being recorded mechanically by pens on a rotating drum. Major earthquakes in the 1920s prompted renewed interest at Stanford resulting in a uni-directional table moving on rails, activated either by a pendulum striking at one end-the other being resisted by springs-or by a wheel with an eccentric-mass attached to the table. A valuable feature here was that the size of the eccentric mass could be varied as the harmonic motion continued, thereby providing a method of control. In the 1950s, a similar pendulum input was used on a table constructed at the University of California, but instead of rails, it was supported by a group of vertical bars flexible in one direction only, and the 1939-1945 war had resulted in the availability of electrical devices for measuring response. Also, in Italy at this time the use of pendulums was augmented by contra-rotating mass input devices giving better frequency control; arrays of several electrodynamic exciters were also used. In Japan, motion was induced by the release of compressed springs.The idea of producing input by an oil-filled piston was introduced at MIT after the 1933 Long Beach earthquake to a table suspended from above by wires. Two other innovations here were of the greatest significance. First was an analogue device for using an actual earthquake record as input, and the second was control of the motion by an error-driven electrically controlled feedback loop. The development of these ideas into the shaking tables, which we use today, had to wait upon the general development of control engineering during the 1939-1945 war, followed by progressively greater speeds in digital computation. This history ends (c.1985) after the continuation of these advances made possible full 6-DOF control using many oil-filled actuators, but before they became able to give us real-time control with the attendant abilities of multi-support input and the experimental study of inelastic behaviour. Figure 15. A diagram indicating the essential features of the 20×20 ft UCB shaking table.the central rib, and were positioned such that any yawing motion of the table could be resisted by the control system. The four vertical actuators, each of 25 kips, were attached to the table at the locations shown in Figure 15 by means of prestressing rods in 2 in diameter pipes running vertically through the table on a 3 ft square grid. The pipes also served as attachment points for the structure being tested. The actuators had a swivel joint at each end, of such a length that they made a significant contribution to de-coupling the vertical and the horizontal motions of the table, with further de-coupling provided by the electronic control system.Although these ve...

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“…Kajiwara et al [8] and Ji et al [9] used IDCS on the world's largest three-dimensional shaking table, based in Japan, known as E-Defense (e.g. references [10] and [11]). These studies resulted in the generation of accurate, large-amplitude vibration responses.…”

Section: Introductionmentioning

confidence: 99%

Inverse dynamics compensation via ‘simulation of feedback control systems'

Tagawa

Stoten

2011

Proceedings of the Institution of Mechanical Engineers, Part I:

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In many applications within the fields of science, engineering, mathematics, and socio-economics, the 'inverse problem' (i.e. the problem of determining a system's input from its output) is commonplace. The current paper presents a new concept for solving the inverse problem, which the authors call inverse dynamics compensation via 'simulation of feedback control systems' (IDCS). IDCS is a numerical method that obtains an approximate inverse dynamic solution via a feedback control simulation, using only the forward dynamic model of the linear or non-linear system. Simulations are ideal environments for feedback control, in the sense that they can be completely noise-free and precisely known, so that the IDCS method can be tuned for the best possible performance. It is seen that IDCS can use the advantages of such ideal control simulation performance in the real world of physical implementations.This paper first introduces the basic idea of IDCS. Then, the effectiveness of the proposed method is demonstrated via three illustrative examples, in which the systems to be controlled have continuous and discontinuous non-linearities. IDCS performance is also investigated via physical experimentation on a non-linear servohydraulic test rig. Finally, extensions of the basic IDCS formulation are introduced which are potentially useful for the solution of additional practical problems.

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Construction of a three–dimensional, large–scale shaking table and development of core technology

Cited by 50 publications

References 2 publications

Nonlinear signal‐based control for single‐axis shake tables supporting nonlinear structural systems

Nonlinear signal‐based control for single‐axis shake tables supporting nonlinear structural systems

The development of shaking tables–A historical note

Inverse dynamics compensation via ‘simulation of feedback control systems'

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