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Guaranteeing Isochronous Control of Networked Motion Control Systems Using Phase Offset Adjustment.

Kim I, Kim T - Sensors (Basel) (2015)

Bottom Line: In realizing the idea, we performed a pre-runtime analysis to determine a safe and reliable phase offset and applied the phase offset to the runtime code of motion controller by customizing an open-source based integrated development environment (IDE).We also constructed an EtherCAT-based motion control system testbed and performed extensive experiments on the testbed to verify the effectiveness of our approach.The experimental results show that our heuristic is highly effective even for low-end embedded controller implemented in open-source software components under various configurations of control period and the number of motor drives.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Information Engineering, University of Seoul, 163 Seoulsiripdae-ro, Dongdaemun-gu, Seoul 130-743, Korea. ihkim@uos.ac.kr.

ABSTRACT
Guaranteeing isochronous transfer of control commands is an essential function for networked motion control systems. The adoption of real-time Ethernet (RTE) technologies may be profitable in guaranteeing deterministic transfer of control messages. However, unpredictable behavior of software in the motion controller often results in unexpectedly large deviation in control message transmission intervals, and thus leads to imprecise motion. This paper presents a simple and efficient heuristic to guarantee the end-to-end isochronous control with very small jitter. The key idea of our approach is to adjust the phase offset of control message transmission time in the motion controller by investigating the behavior of motion control task. In realizing the idea, we performed a pre-runtime analysis to determine a safe and reliable phase offset and applied the phase offset to the runtime code of motion controller by customizing an open-source based integrated development environment (IDE). We also constructed an EtherCAT-based motion control system testbed and performed extensive experiments on the testbed to verify the effectiveness of our approach. The experimental results show that our heuristic is highly effective even for low-end embedded controller implemented in open-source software components under various configurations of control period and the number of motor drives.

No MeSH data available.


Related in: MedlinePlus

Two synchronization modes in the EtherCAT slave.
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f2-sensors-15-13945: Two synchronization modes in the EtherCAT slave.

Mentions: EtherCAT also provides two kinds of synchronization events, i.e., frame events and clock events, for the coordinated operations of multiple slaves [9]. As shown in Figure 2, a local slave task, which is responsible for actuation or sensing, can be synchronized with these events. The frame-driven control process may often experience relatively large deviation due to the variation in in-controller processing time. When a slave task requires a higher-degree of cycle precision with low deviation, a globally synchronized clock should be used. The slave task may take actions based on the autonomous interrupt that is generated with the global clock, referred as the Distributed Clock (DC), and therefore, the deviation of control process can be reduced by up to a few nanoseconds [11].


Guaranteeing Isochronous Control of Networked Motion Control Systems Using Phase Offset Adjustment.

Kim I, Kim T - Sensors (Basel) (2015)

Two synchronization modes in the EtherCAT slave.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507583&req=5

f2-sensors-15-13945: Two synchronization modes in the EtherCAT slave.
Mentions: EtherCAT also provides two kinds of synchronization events, i.e., frame events and clock events, for the coordinated operations of multiple slaves [9]. As shown in Figure 2, a local slave task, which is responsible for actuation or sensing, can be synchronized with these events. The frame-driven control process may often experience relatively large deviation due to the variation in in-controller processing time. When a slave task requires a higher-degree of cycle precision with low deviation, a globally synchronized clock should be used. The slave task may take actions based on the autonomous interrupt that is generated with the global clock, referred as the Distributed Clock (DC), and therefore, the deviation of control process can be reduced by up to a few nanoseconds [11].

Bottom Line: In realizing the idea, we performed a pre-runtime analysis to determine a safe and reliable phase offset and applied the phase offset to the runtime code of motion controller by customizing an open-source based integrated development environment (IDE).We also constructed an EtherCAT-based motion control system testbed and performed extensive experiments on the testbed to verify the effectiveness of our approach.The experimental results show that our heuristic is highly effective even for low-end embedded controller implemented in open-source software components under various configurations of control period and the number of motor drives.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Information Engineering, University of Seoul, 163 Seoulsiripdae-ro, Dongdaemun-gu, Seoul 130-743, Korea. ihkim@uos.ac.kr.

ABSTRACT
Guaranteeing isochronous transfer of control commands is an essential function for networked motion control systems. The adoption of real-time Ethernet (RTE) technologies may be profitable in guaranteeing deterministic transfer of control messages. However, unpredictable behavior of software in the motion controller often results in unexpectedly large deviation in control message transmission intervals, and thus leads to imprecise motion. This paper presents a simple and efficient heuristic to guarantee the end-to-end isochronous control with very small jitter. The key idea of our approach is to adjust the phase offset of control message transmission time in the motion controller by investigating the behavior of motion control task. In realizing the idea, we performed a pre-runtime analysis to determine a safe and reliable phase offset and applied the phase offset to the runtime code of motion controller by customizing an open-source based integrated development environment (IDE). We also constructed an EtherCAT-based motion control system testbed and performed extensive experiments on the testbed to verify the effectiveness of our approach. The experimental results show that our heuristic is highly effective even for low-end embedded controller implemented in open-source software components under various configurations of control period and the number of motor drives.

No MeSH data available.


Related in: MedlinePlus