Distributed control of industrial robot systems using Petri net based multitask processing
In this paper, the methods of the modeling of the discrete event robotic manufacturing systems using Petri nets are considered, and a methodology of decomposition and coordination is presented for hierarchical and distributed control, where the cooperation of each controller is implemented so that the behavior of the overall system is the same as the centralized control system and the task specification is completely satisfied. First, a task specification is defined as a Petri net model at the conceptual level, and then transformed to the detailed Petri net representation of the subtasks. Finally, the overall Petri net is decomposed and the constituent subnets are assigned to local Petri net based controllers. The controllers are coordinated so that the decomposed transitions fire at the same time by the coordinator. System coordination algorithm through communication between the coordinator and the controllers, is presented. By the proposed method, modeling, simulation and control of large and complex manufacturing systems can be performed consistently using Petri nets.
Experimental study on wind-based vehicle speedometer applying the whistle principle
It is important to consider the effect of wind when driving a vehicle at high speeds since the rate of fuel consumption may change according to wind direction in relation to vehicle driving direction. In order to minimize fuel consumption when driving at high speeds, it is necessary to control the relative vehicle speed against the wind. This paper proposes a new type of speedometer that is based on wind speed instead of conventional ground speed. For the detection of wind speed, we focus on the whistle principle where the frequency of the whistle sound is proportional to the airflow rate. To measure the wind speed as airflow rate, we developed a special whistle suitable for a wind-based vehicle speedometer by using CAD software for three-dimensional modeling. Characteristics of the developed wind-based vehicle speedometer were tested in both indoor experiments and actual-vehicle outdoor experiments. The validity of the proposed method was confirmed by the experiments.
Frequency selective surface design for blinds applications
In this paper, the reconfigurable blind structure with frequency selective surfaces(FSS) for the building applications are presented. Frequency transmission characteristics for different angles of the proposed blind-FSSs are investigated and verified through simulation and measurement. The simulation results show that we can implement the reconfigurable blind-FSS for multiband wireless applications. To verify the proposed paper, two kinds of blind-FSSs, crossed dipole FSS and circular ring FSS are fabricated and measurements are performed for different angles. The proposed structure in this paper which is very simple, can be easily applied to any planar surface for wireless security applications at low cost.