•The adaptive control of metal working process is a logic extension of numerical control and computer control. In NC process as described so far, the cutting speed and feeds are prescribed by the path programmer. The determination of these parameter depends on his knowledge and experience about the work piece and tool materials, coolant condition and other factors.
•The main idea of Adaptive Control is the improvement of the cutting process by automatic on line determination of speed and/or cutting.
•It is basically a feedback system in which cutting speed and feed automatically adapt themselves to the actual condition of the process and are varied accordingly to the changes in the work conditions as work progresses.
•That is done by performing of the process output variables and calculating either a performance level or machine constrains.
•In practice the Adaptive Control system of machine tools can be classified into two types:
o Adaptive Control with Optimization (ACO)
o Adaptive Control with Constraints (ACC)
•Benefits of Adaptive Control :
o Increased production rate
o Increased tool life
o Greater part protection
o Less operator intervention
Types of Adaptive control in Manufacturing.
a)Adaptive control Optimization.
The ACO Systems for N/C machine tools is a control system that optimizes performance index subjects to various constraints. It is basically a sophisticated closed loop control system, which automatically works in optimum conditions, even in the presences of work piece and tools materials variations.
The sensor measures the torque, temperature and vibration. These measurements are used by the adaptive controller to obtain feed and speed values for obtaining optimum cutting conditions.
b)Adaptive control Constraint.
The system developed for actual production was somewhat less sophisticated than the research ACO systems. The production AC systems utilize constraint limits imposed on certain measured process variables. Accordingly, these are called adaptive control constraint (ACC) systems.
When the cutting force and torque are too high, the cutter may break in bending or in twist. On the other hand, for maximum productivity, the maximum allowable feeds and cutting speed must be used.
The principle of ACC system is to sense the constraint variable and to adjust the cutting speed and feed according to this measurement and a programmed strategy. In a case where two constraints are used simultaneously, the system must consider the variable which to its maximum permissible value.
The advantage of this ACC system is that the cutting tool is protected against catastrophic failure simultaneously with keeping highest possible feed rate.
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