Abstract
In this paper, wireless feedback control of multiple machines over a beacon-enabled IEEE 802.15.4 network is considered. In the beacon-enabled IEEE 802.15.4 network, beacons periodically structure superframes on the time axis, and each superframe consists of a contention access period (CAP) and a contention free period (CFP). In the CAP, a carrier sense multiple access/collision avoidance (CSMA/CA) is used; in the CFP, a guaranteed time slot (GTS)-based time division multiple access is used. Because of collision and backoff periods of packet transmission, the probability of communication failure in the CAP is greater than that in the CFP; however, the number of available GTSs is limited to seven by the standard. In order to improve the control performance of wireless feedback control, the controller must effectively allocate GTSs to transmit control input and state feedback of controlled machines. We provide a simple but efficient idea that takes both the feedback control mechanism and packet transmission mechanism of the CAP and CFP into consideration to better allocate GTSs. We propose a superior GTS allocation method that fully conforms to the IEEE 802.15.4 standard and show that the proposed method can further improve control performance.
Highlights
Wireless feedback control systems are a type of feedback control system whose control loop between the controller and controlled machines is connected via wireless communication
In the beacon-enabled IEEE 802.15.4 network, beacons periodically structure superframes on the time axis and each superframe consists of a contention access period (CAP) and contention free period (CFP)
We have shown that the proposed method can effectively improve the control performance compared to the conventional method and without guaranteed time slot (GTS), especially for a larger number of controlled machines
Summary
Wireless feedback control systems are a type of feedback control system whose control loop between the controller and controlled machines is connected via wireless communication. In order to improve the control performance of wireless feedback control over the beacon-enabled IEEE 802.15.4 network, the controller must effectively allocate GTSs to transmit control input and state feedback of controlled machines. Another study proposed a GTS allocation method based on a deadline time of communication and control tasks [17]; packet collision and packet loss in the network were not taken into account. The beacon-enabled mode is suitable for synchronized periodic control systems because the beacons periodically structure superframes on the time axis and allow the synchronization of controlled machines From this view point, in this paper, wireless feedback control of multiple machines over the beacon-enabled IEEE 802.15.4 network is focused.
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