This article focuses on the design and implementation of model-based control strategies for real time control of crystal size distribution (CSD) in semi batch crystallization processes. The objective of the feedback controller is to reach a desired particle mean size while the standard deviation is controlled in a feed-forward fashion. Alternative model-based control strategies are formulated and implemented for a target mean size. An image processing technique based on wavelet-fractal and energy signature analysis is employed to determine online CSD status for the controller's corrective actions. To validate the proposed model-based control strategies, unseeded crystallization of sodium chloride in water using ethanol as antisolvent is performed in an experimental bench-scale semi-batch crystallizer. (C) 2018 Elsevier Ltd. All rights reserved.