Model Reference-Based Sliding Mode Control of Supply Chains With Defined Suppliers’ Delivery Capabilities

This paper features a novel approach to modelling an inventory management system. The work takes into account a single product warehouse with multiple suppliers. Each supplier delivers its product with a certain lead time. Furthermore, the amount of product each supplier can deliver at a single time instant is limited by the supplier’s maximum order quantity. The system prioritizes faster suppliers (i.e. suppliers with shorter lead times), which can result in them delivering large portions of the full resupply orders at time instants with low enough values of the control signal. The warehouse is subject to a demand of dual nature: the first type of demand is contractual, resulting froma prioriknown obligations to its customers. The second type is a random, unknown term, bounded by a maximum value, realized by selling product leftover from trading with contracted customers. The controller’s goal is to ensure full demand satisfaction. We begin by employing a reference model with just one supplier and no random demand. Then, a sliding mode controller is applied to generate a desired resupply order profile capable of fulfilling the contractual demand at any time instant. This control scheme is designed to keep the amount of goods in the warehouse at its absolute minimum - in other words, the effect of the demand will always empty the warehouse at each time instant. We then continue by using this resupply order profile as a desired trajectory in a sliding mode controller for the real system. Finally, it is proven that with appropriate compensation for the random demand present in the system, this approach can achieve full demand satisfaction at all time instants in a system with multiple suppliers with varying lead times.