Browsing by Author "Cakmakci, Melih"

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Open Access
Improving the dimensional accuracy of micro parts 3D printed with projection-based continuous vat photopolymerization using a model-based grayscale optimization method
(Elsevier, 2022-09) Guven, Ege; Karpat, Yigit; Cakmakci, Melih
Micro-scale additive manufacturing has seen significant growth over the past years, where improving the accuracy of complex micro-scale geometries is seen as an important challenge. Using grayscale images rather than black and white images during production is an effective method to improve the fabrication quality. This paper presents a model-based optimization method for improving the dimensional accuracy of parts using voxel-based grayscale dynamic optimization during continuous 3D printing. A detailed solidification model has been developed and used to estimate the curing dynamics of the resin used in 3D printing. The irradiance of the light beam projected for each pixel influences a larger volume on the resin than the targeted voxel. The proposed model-based method optimizes the images considering the light distribution from all closely related pixels to maintain the accuracy of the micro part. The results of this method have been applied to the printing of a complex 3D part to show that optimized grayscale images improve the areas with overcuring significantly. It is shown that the number of overcured voxels was reduced by 24.7% compared to the original images. Actual printing results from our experimental setup confirm the improvements in the accuracy and precision of the printing method.
Open Access
Physics-informed disturbance estimation and nonlinear controller design for a multi-axis gimbal system
(Elsevier, 2022-11-22) Leblebicioglu, Damla; Atesoglu, Ozgur; Cakmakci, Melih
The increasing demand for target tracking, environmental surveys, surveillance and mapping requires multi-axis gimbal systems with high tracking and stabilization performance. In this study, a new torque estimation structure is proposed to compute the complex disturbances negatively affecting the performance of the system. Two different control strategies based on Active Disturbance Rejection Control (ADRC) and Estimated Torque Model are implemented on a two-axis gimbal system. In the first strategy, the purpose is to improve the robustness, environmental adaptability and tracking accuracy of the system. The tuning effort of the ADRC is reduced by integrating a Neural Network (NN) based disturbance compensator (NN assisted ADRC). In the second strategy, NN is replaced with an Estimated Torque Model (ETM assisted ADRC), whose inputs come from plant outputs. The simulation results show that, both NN and ETM assisted control structures decrease the tracking errors. However, the improvements achieved by the physics-informed neural network-based estimator are more significant.