Abstract
AbstractIn this paper, discrete time model reference control schemes for practical milling using different discretization of the continuous-time plant are presented. First, a basic controller scheme is addressed where a fractional order hold with pre-fixed value of the gain is used. Secondly, a multi-model scheme, which outputs different discretization in parallel with the continuous-time milling system transfer function under a fractional order hold (FROH) of correcting β ∈ [−1, 1], is dealt with. Then, an intelligent design framework is designed as a supervisory scheme with two hierarchical levels in order to find the most appropriate value for the gain β. For choosing the value of β, a tracking performance index is designed. It evaluates each pre-defined discretization of the continuous time milling transfer function and the scheme chooses the one with the smallest value of the index in order to generate the real control input to the plant. Two different methods of adjusting this value are presented and discussed. The first one selects a β-value among a fixed pre-defined set of possible values, while the second one the value of β is updated by adding or subtracting a small quantity.
Highlights
Milling, the cutting process widely used in the manufacturing of mechanical components, consists of the relative movement between clamped workpiece and rotating multi-tooth cutting tool
Strategies for controlling the milling system are based on the use of fractional order holds of the correcting gain β ∈ [−1, 1], (β-FROH)
It shows the influence of the gain β when using a fixed β-FROH in the closed loop behavior and, it investigates the performance of two different multi-model schemes
Summary
The cutting process widely used in the manufacturing of mechanical components, consists of the relative movement between clamped workpiece and rotating multi-tooth cutting tool. Different kinds of holds are increasingly being used due to their enhanced properties.[16,17] In this work, strategies for controlling the milling system are based on the use of fractional order holds of the correcting gain β ∈ [−1, 1], (β-FROH) It shows the influence of the gain β when using a fixed β-FROH in the closed loop behavior and, it investigates the performance of two different multi-model schemes. The tracking performance of the continuous -time output signal is studied It is carried out by means of a cost function and applied to the basic control scheme when just ZOH and β-FROH fixed gain devices and when the two different structures of the multi-model scheme are applied. The design of a discrete time control of milling forces is presented considering high volume operations, where the milling system model is perfectly characterized and the plant parameters are known or varied in a known way, even though sudden changes in the tool-part combinations happen
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