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Samples of AZ80Mg alloy were multi-directionally forged (MDFed) at various strain rates in the rage from 3.0 × 10 −3 s −1 to 3.0 × 10under decreasing temperature conditions. The MDFing pass temperatures employed were 653 K, 605 K and 553 K. These passes, each of 0.5 strain, were applied up to a cumulative strain of ΣΔε = 1.5 at maximum. The average grain size decreased with increasing cumulative strain and depended only weakly on the strain rate. Microstructures with average grain sizes of 0.84 μm, 0.88 μm and 1.2 μm were attained when MDFed at strain rates of 3.0 × 10 −1 s −1 , 3.0 × 10 −2 s −1 and 3.0 × 10 −3 s −1. The microstructure evolved at 3.0 × 10 −1 s −1 was less homogeneous. This difference is interpreted as being due to the higher stored energy causing static recrystallization in the latter MDFing condition. As a result, the best balance of the mechanical properties was attained by MDFing at 3.0 × 10 −2 s −1. In this case, ultimate tensile strength (UTS) of 445 MPa was achieved together with a fracture strain of 22%. By comparison, MDFing at 3.0 × 10 −1 s −1 led to lower UTS and ductility of 410 MPa and 15% while the yield stresses were comparable.

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This paper introduces a level control system using a fuzzy I-PD controller. The proposed controller composes of Mamdani fuzzy I and Mamdani fuzzy PD controllers and is adjusted to meet the desired control system performances both in transient state and steady state. The simulation results in controlling the level processes by using the fuzzy I-PD controller with the same parameters (proportional gain, integral gain and derivative gain) as the conventional I-PD controller are shown in this paper.

A second-order level process controlled by PI controller designed from coefficient diagram method (CDM) will meet the desired performances both in transient and steady-sate response [ 11. However, the transient response generally still has long rise time [2]. This paper presents an additional idea to improve the speed of the system response by including a feedforward controller (FFC) in the closed-loop system [3]. The structure of the FFC is a phase lead structure with a parameter that can be varied greater than one. The faster step response of the controlled system can be obtained while the rejection speed of the effect due to constant output disturbance is not affected by the proposed FFC. ReywordsLevel process, CDM, feedforward controller.