Nonlinear factors in the industrial servo press currently, including mechanisms for force amplification, installed clearances, gears backlash, and variations in rotational inertia, are commonly not ...considered during the control process. They would impact the control accuracy of the actuator's crank and slide and even affect the quality of material forming. So, the conventional linear control method, field-oriented control based on the miniclosed loop of the electrical machine position utilizing kinematics, cannot follow the trajectory smoothly and accurately. This study proposes a solution to address these issues by introducing a semiclosed loop control approach. This method fully accounts for the Lagrangian approach for the dynamic model of the servo press. The torque reference of the computed torque algorithm is implemented by model predictive current control. A comprehensive and comparative trial and analysis of the impacts of critical parameters are conducted. The proposed method is practically tested on a 1600-kN press equipped with a dual-core DSP servo drive. Experimental results demonstrate the effectiveness of this control approach, which significantly enhances the control accuracy of crank position and speed while also reducing the switching frequency and losses of the servo press drive.
Press pack power devices serve as critical components in various high-power applications. However, the closed structure of these devices poses challenges in sensing their internal current ...distribution. This letter addresses this issue by proposing a noninvasive current distribution sensing method based on magnetic field analysis. By strategically placing a limited number of magnetic field sensors near the devices, the proposed method enables the estimation of various forms of nonuniform current distribution. After developing a custom four-point magnetic field measurement setup based on Hall sensors, the current distribution measurement of a commercial insulate gate bipolar transistor (IGBT) under different pressure excursion conditions was performed. Experimental results demonstrate the effectiveness and reliability of the proposed method.
