Erdem Özdemir - 4th Week Definitions - Part 2

Iterative Learning Control (ILC)
Control


New – Better Definition

Iterative Learning Control (ILC) is one of the more recent control theo¬ries. ILC, which can be categorized as an intelligent control methodology,1 is an approach for improving the transient performance of systems that oper¬ate repetitively over a fixed time interval. Although control theory provides numerous tools for improving the performance of a dynamic system, it is not always possible to achieve a desired level of performance. This may be due to the presence of unmodeled dynamics, parametric uncertainties, or distur¬bances and measurement noise exhibited during actual system operation. The inability to achieve a desired performance may also be due to the lack of suit¬able design techniques [298). hi particular, when the system is nonlinear, it is not easy to achieve perfect tracking using traditional control theory. However, for a specific class of systems - those that operate repetitively - ILC is a de¬sign tool that can help overcome the shortcomings of traditional controllers, making it possible to achieve perfect tracking or performance when there is model uncertainty or when wc have a "blind" system.

Various definitions of ILC have been given in the literature. Some of them *e quoted here.
-The learning control concept stands for the repeatability of operating a given objective system and the possibility of improving the control input on the basis of previous actual operation data." Arimoto, Kawamura, and Miyazaki [29].
ILC is a "... recursive online control method that relies on less calculation and requires less a priori knowledge about the system dynamics. The idea is to apply a simple algorithm repetitively to an unknown plant, until perfect tracking is achieved." Bien and Huh |43|.
-Iterative learning control is an approach to improving the transient re-sponse performance of a system that operates repetitively over a fixed time interval." Moore [298].
-Iterative learning control considers systems that repetitively perform the same task with a view to sequentially improving accuracy." Amaiin, Owens, and Rogers [10].
-ILC is to utilize the system repetitions as experience to improve the sys¬tem control performance even under incomplete knowledge of the system to be controlled." Chen and Wen [66].
ILC is a "... controller that learns to produce zero tracking error during repetitions of a command, or learns to eliminate the effects of a repeating disturbance on a control system output." Phan, Longman, and Moore [363].
-The main idea behind ILC is to iteratively find an input sequence such that the output of the system is as close as possible to a desired output. Although ILC is directly associated with control, it is important to note that the end result is that the system has been inverted." Markusson [287].

(Iterative learning control: robustness and monotonic convergence for interval systems, 2007, P 4-5 Hyo-Sung Ahn,Kevin L. Moore,Yangquan Chen, )


Previous:

Iterative learning control (ILC), a relatively a new technique within the arsenal of the control engineer, is a technique for improving the transient response and tracking performance of any physical system that is required to execute a particular operation repeatedly (such as a manipulator that might be programmed to do spot welding in an automobile manufacturing assembly line). By observing the error in the output response after each operation and using the error to modify the input signal to the system, ILC attempts to improve the system performance. In other words, ILC is a technique for systems with repetitive or iterative operations, which are modified based on the observed error (or are programmed to learn) to control the input signal at each repetitive operation

(Modeling, Sensing and Control of Gas Metal Arc Welding,Desineni Subbaram Naidu, S. Ozcelik, K. Moore D. S. Naidu-1st edition, (2003),P.179)

Incoming Material Control
Production System


There is no previous definition for this term.

Quality control begins on the receipt of raw materials such as adhesives and catalysts. The purchase order ordinarily defines the required quality proper¬ties of this material. This is accomplished by an actual statement of require¬ments, or by what is called out in the material specifications. The inspection requirements are normally specified in the material specifications as Qual¬ity Acceptance Tests or as Receiving Inspection Requirements.'3'

Containers: The first inspection requirement is normally the condition of the container. The following items should be checked when inspecting the container.131

Damage: Physical damage to a container of film adhesive can rupture its sealed wrapper, allowing moisture, dirt, etc., to reach and contaminate the adhesive. Damage can render a pail of liquid measure unusable in auto¬matic measuring equipment.

Leakage: Leakage of liquid adhesive components can change the ratio of the catalyst to the base resin if premeasured kits are involved. It can also result in the receipt of less material than the purchaser needs and is paying for.

Identification: Identification of a container should include:
• product number
• shelf life
• manufacturer's name
• recommended storage conditions
• date of manufacture
• manufacturer's instructions for use
• batch or lot number
• safety precautions
(Adhesives Technology Handbook, 2008, Sina Ebnesajjad, P292)