Ikhwan Kim

An open-source development environment for industrial automation with EtherCAT and PLCopen motion control

Standards conformance and integrated development are key features of modern automation systems. This paper introduces an integrated development environment (IDE) that enables high-speed EtherCAT communication and standardized motion programming. On the basis of our previous work, we extended and customized open-source software components to provide a completely open architecture IDE, that is compliant with the relevant industrial standards. The major components of our IDE are IEC 61131-3 and PLCopen TC6 compliant editor, EtherCAT communication support, and PLCopen TC2 compliant motion control library. Since the whole procedures from the project setup to run-time monitoring are highly automated, the presented IDE allows developers to integrate coordinated motion with control logics seamlessly and efficiently.

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

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.

Xenomai-based Embedded Controller for High-Precision, Synchronized Motion Applications

Motion control systems are widely deployed in various industrial automation processes. The motion controller, which is a key element of motion control systems, has stringent real-time constraints. The controller must provide a short and deterministic control message transmission cycle, and minimize the actuation deviation among motor drives. To meet these requirements, hardware-based proprietary controllers have been prevalent. However, since it is becoming difficult for such an approach to meet increasing needs of system interoperability and scalability, nowadays, software-based universal motion controllers are regarded as their substitutes. Recently, embedded motion controller solutions are gaining attention due to low cost and relatively high performance. In this paper, we designed and implemented an embedded motion controller on an ARM-based evaluation board by using Xenomai real-time kernel and other open source software components. We also measured and analyzed the performance of our embedded controller under a realistic test-bed environment. The experimental results show that our embedded motion controller can provide relatively deterministic performance with synchronized control of three motor axis at 2 ms control cycle.

Improving TCP Goodput over Wireless Networks Using Kernel-Level Data Compression

Due to the rapid evolution of mobile processors and wireless networks, many personal mobile devices are able to support wide spectrum of Internet applications. In such systems, it is highly desirable to provide high-speed wireless communication while restraining the CPU from wasting its resources. Previous study has revealed that the bottlenecks of the communication on wireless devices are the data movements over not only the wireless link but also the bus between the memory and network controller. To overcome this performance limitation, we consider reducing the size of data traversing the bus and wireless link. In this paper, we suggest an efficient kernel-level TCP data compression scheme, which is transparent to the existing applications and can provide high-speed wireless communication. A challenging issue is that the performance gain should amortize the data compression overhead. The experimental results on realistic wireless Internet scenarios show that the modified Linux kernel can achieve better performance up to 60% and 72% than the original TCP over Wireless LAN and WiMAX, respectively. Moreover, we show that the suggested scheme can save more CPU resources in spite of data compression overhead.

Design and Implementation of a Flexible Application Permission Management Scheme on Android Platform

Google Android, which is one of the popular smart phone platforms, employs a security model based on application permissions. This model intends to reduce security threats by protecting inappropriate accesses to system resources from applications, but this model has a few problems. First, permission requested by an application cannot be granted selectively. Second, once the permission has been granted it is maintained until the application is uninstalled. Third, applications may acquire powerful permissions through user ID sharing without any notice to users. In order to overcome these limitations, we designed and implemented a flexible application permission management scheme. The goal of our scheme is to enhance security and user convenience while keeping compatibility to original platform. We also verified the operation of our scheme with real applications on Android emulator.