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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

Performance comparison between embedded SBC and commercial controller.
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f11-sensors-15-13945: Performance comparison between embedded SBC and commercial controller.

Mentions: We also compared the performance of embedded SBC and that of a commercial EtherCAT master controller, which has similar hardware specification. All experimental configurations are the same as previous experiments, except for the implementation of motion control task. We used TwinCAT-2 NC PTP runtime to implement a motion application for the commercial controller. Figure 11 shows the performance evaluation results. The results demonstrate that embedded SBC with our heuristic outperforms the commercial controller for all the test configurations used. For Tcycle = 1000 μs, the commercial controller has good performance in average because the 99% of measured samples are located in 24.9 μs, 29.4 μs, and 35.7 μs, which amount to 2%–3% with respect to Tcycle for varying N. However, for a smaller control cycle Tcycle = 500 μs, the performance degradation of the commercial controller is noticeable with increasing N in terms of absolute difference Δ. By contrast, the evaluation results of our approach show quite stable distribution for all the test configurations. Although the commercial controller used in the experiment may not be fully optimized, the results imply that our approach can achieve performance comparable to a commercial solution.


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

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

Performance comparison between embedded SBC and commercial controller.
© Copyright Policy
Related In: Results  -  Collection

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

f11-sensors-15-13945: Performance comparison between embedded SBC and commercial controller.
Mentions: We also compared the performance of embedded SBC and that of a commercial EtherCAT master controller, which has similar hardware specification. All experimental configurations are the same as previous experiments, except for the implementation of motion control task. We used TwinCAT-2 NC PTP runtime to implement a motion application for the commercial controller. Figure 11 shows the performance evaluation results. The results demonstrate that embedded SBC with our heuristic outperforms the commercial controller for all the test configurations used. For Tcycle = 1000 μs, the commercial controller has good performance in average because the 99% of measured samples are located in 24.9 μs, 29.4 μs, and 35.7 μs, which amount to 2%–3% with respect to Tcycle for varying N. However, for a smaller control cycle Tcycle = 500 μs, the performance degradation of the commercial controller is noticeable with increasing N in terms of absolute difference Δ. By contrast, the evaluation results of our approach show quite stable distribution for all the test configurations. Although the commercial controller used in the experiment may not be fully optimized, the results imply that our approach can achieve performance comparable to a commercial solution.

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