Dynamic Simulation and Control of a Roller Conveyor
Abstract Passive roller conveyors are frequently used in material handling applications to transport objects of various sizes and shapes. Passive systems cannot control unit flow, leading to queues and system jams. In this paper we analyze the performance of a gravity-driven roller conveyor with brakes selectively installed on rollers to control package flow in the load lanes of a transportation hub. Dynamics of the rollers and kinematic interaction with boxes on the conveyor were derived and fully modeled in MATLAB to simulate accurate conveyor behavior. Sensitivity analyses were performed to evaluate the effect of friction, box mass, roller inertia, and other factors. Using heuristic data to define boundary conditions (box weight, size, and input frequency), several control cases were evaluated. Performance was defined by buffering efficiency of the conveyor, or how effectively the conveyor “kept pace” with a person moving boxes from the load conveyor onto a waiting truck. Several dynamic control cases were simulated. It was found that the optimal number of installed brakes is 30% of the total rollers on the conveyor. Even rudimentary brake control schemes (applying a simple duty-cycle on/off to roller brakes) had the potential to increase the conveyor buffer efficiency by 10% over baseline, with the potential for much greater benefits from more “intelligent” closed-loop control schemes. The simulation and optimization of the active roller conveyor gave insights into the behavior of their truck loading system and identified several ways to increase loading efficiency.