System construction of a four-side primary permanent-magnet linear motor drive mechanical press
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RESEARCH ARTICLE
Jintao LIANG, Zhengfeng MING, Peida LI
System construction of a four-side primary permanent-magnet linear motor drive mechanical press
© Higher Education Press 2020
Abstract A primary permanent-magnet linear motor (PPMLM) has a robust secondary structure and high force density and is appropriate for direct-drive mechanical press. The structure of a four-side PPMLM drive press is presented based on our previous research. The entire press control system is constructed to realize various flexible forming processes. The control system scheme is determined in accordance with the mathematical model of PPMLM, and active disturbance rejection control is implemented in the servo controller. Field-circuit coupling simulation is applied to estimate the system’s performance. Then, a press prototype with 6 kN nominal force is fabricated, and the hardware platform of the control system is constructed for experimental study. Punch strokes with 0.06 m displacement are implemented at trapezoidal speeds of 0.1 and 0.2 m/s; the dynamic position tracking errors are less than 0.45 and 0.82 mm, respectively. Afterward, continuous reciprocating strokes are performed, and the positioning errors at the bottom dead center are less than 0.015 mm. Complex pulse trajectories are also achieved. The proposed PPMLM drive press exhibits a fast dynamic response and favorable tracking precision and is suitable for various forming processes. Keywords mechanical press, direct drive, primary permanent-magnet linear motor (PPMLM), servo system, active disturbance rejection control (ADRC), prototype experiment
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Introduction
Mechanical press is a widely used equipment in metal forming [1]. Owing to the elimination of linear motion Received November 2, 2019; accepted June 8, 2020
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Jintao LIANG ( ), Zhengfeng MING, Peida LI School of Mechano-Electronic Engineering, Xidian University, Xi’an 710071, China E-mail: [email protected]
conversion mechanisms, such as crank link and ball screw, a press that is directly driven by a permanent-magnet linear motor (PMLM) exhibits a compact structure, high transmission efficiency, high positioning precision, and fast dynamic response. Reference [2] summarized several linear drive applications of metal-forming machines. The drawback of traditional PMLM drive is that either the permanent magnets (PMs) or the coils are installed on the slider (mover) [3,4]; thus, good protection and heat dissipation are required, and the fabrication cost is high. Primary permanent-magnet linear motor (PPMLM) is a novel PMLM wherein the PMs and coils are arranged on the primary side, and the secondary side contains only the salient pole core [5–8]; it is robust against impact loading. Our research group has developed several PPMLM directdrive apparatuses in recent years [9]. A linear-drive mechanical press features controllable force in the entire punching stroke, and various punch trajectories can be achieved for a flexible forming process [10–12]. However, various parameter variations and external disturbances
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