Model Reference Based Sliding Mode Control for an Inventory System With a Novel Demand Profile

This paper presents a new approach to the inventory management problem. The work considers control design for a single product warehouse with multiple suppliers with different delivery times. The demand is divided into two parts: the a priori known time-variant contractual demand and the unknown but bounded random demand. The controller’s task is to generate an order sequence, such that the stock always satisfies the contractual demand and some spare products for the random buyers are stored. Therefore, we design a reference system with one supplier and one lead time only. To such a reference model we apply a sliding mode controller, which generates the appropriate order values to satisfy the contractual demand at each time instant. The model is designed so that at each time instant the warehouse receives the exact amount of goods to match the demand, consequently minimizing the required warehouse capacity. As a result, the warehouse is emptied by the end of each day. Next, we treat these values as a reference trajectory for the multiple supplier system and design a trajectory following control law. The paper proves that with appropriate compensation of the random sales, such a control strategy ensures satisfaction of the contractual demand at all time instants.