The Ach Library: A New Framework for Real-Time Communication

Dantam, Neil T.; Lofaro, Daniel M.; Hereid, Ayonga; Oh, Paul; Ames, Aaron D.; Stilman, Mike

doi:10.1109/mra.2014.2356937

Cited by 33 publications

(23 citation statements)

References 12 publications

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“…This is the Head of Line (HOL) Blocking problem. The specific issues of each POSIX communication mechanism are discussed in Dantam et al (2015). It was this HOL blocking challenge that motivated the initial development of Ach (Dantam and Stilman, 2012), which always provides access to the most recent data sample.…”

Section: Real-time Communicationmentioning

confidence: 99%

“…Xenomai runs the real-time Adeos hypervisor alongside a standard Linux kernel (Gerum, 2004). It typically offers better latency than PREEMPT_RT but is less polished (Brown, 2010;Dantam et al, 2015) and its dual kernel approach complicates development. Because of the maturity, positive roadmap, and open source code base of Linux PREEMPT_RT (Fayyad-Kazan et al, 2013), we initially implement multiplexable Ach channels within this kernel.…”

Section: Real-time Kernelsmentioning

confidence: 99%

“…In contrast, real-time control requires low latency access to the newest data. Dantam et al (2015) discusses the challenges of POSIX communication in detail. This gap has made it difficult to develop real-time applications in the multiprocess POSIX style.…”

Section: Extending Linux Communicationmentioning

confidence: 99%

“…Failures encountered while developing and testing the new controller did not affect the other running control processes. In contrast, combining multiple controllers in a single process as was necessary for the user space Ach systems presented in Dantam et al (2015) means that errors encountered while prototyping a new controller will not interfere with existing control modes. In research applications on robot control, easing controller development and testing is a key advantage.…”

Section: Case Study: Baxter Robotmentioning

confidence: 99%

“…Instead, Ach is a mechanism that integrates and builds upon the vast useful features of the POSIX and Linux ecosystem. In previous work, we presented an implementation of the Ach data structure in the POSIX user space (Dantam and Stilman, 2012;Dantam et al, 2015). User space Ach was limited in the ability to receive data from multiple sources.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Unix Philosophy and the Real World: Control Software for Humanoid Robots

Dantam

Bøndergaard²,

Johansson

et al. 2016

Front. Robot. AI

Self Cite

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Robot software combines the challenges of general purpose and real-time software, requiring complex logic and bounded resource use. Physical safety, particularly for dynamic systems such as humanoid robots, depends on correct software. General purpose computation has converged on unix-like operating systems -standardized as POSIX, the Portable Operating System Interface -for devices from cellular phones to supercomputers. The modular, multi-process design typical of POSIX applications is effective for building complex and reliable software. Absent from POSIX, however, is an interproccess communication mechanism that prioritizes newer data as typically desired for control of physical systems. We address this need in the Ach communication library which provides suitable semantics and performance for real-time robot control. Although initially designed for humanoid robots, Ach has broader applicability to complex mechatronic devices -humanoid and otherwise -that require real-time coupling of sensors, control, planning, and actuation. The initial user space implementation of Ach was limited in the ability to receive data from multiple sources. We remove this limitation by implementing Ach as a Linux kernel module, enabling Ach's high performance and latest-message-favored semantics within conventional POSIX communication pipelines. We discuss how these POSIX interfaces and design principles apply to robot software, and we present a case study using the Ach kernel module for communication on the Baxter robot.

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Section: Real-time Communicationmentioning

confidence: 99%

Section: Real-time Kernelsmentioning

confidence: 99%

Section: Extending Linux Communicationmentioning

confidence: 99%

Section: Case Study: Baxter Robotmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Unix Philosophy and the Real World: Control Software for Humanoid Robots

Dantam

Bøndergaard²,

Johansson

et al. 2016

Front. Robot. AI

Self Cite

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show abstract

Development and control of a military rescue robot for casualty extraction task

Choi

Lee

Park

et al. 2018

Journal of Field Robotics

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This paper presents the development and control methodology of a military rescue robot for a casualty extraction task. The new rescue robot (HURCULES) equipped with electric actuators for the casualty extraction task on the battle field is introduced. In this paper, mechanical designs of the HURCULES are described in detail. One of the noticeable features in the mechanical design is to use the worm gear in the joint to maintain the safety of the casualty even with power‐off and to reduce the energy through a selected operating mode. Moreover, unlike the upper body of a conventional humanoid robot, the chest plate is installed and used to properly distribute the casualty’s weight to the dual‐arm manipulator and the chest plate when carrying the wounded person. The HURCULES is valuable because the rescue robots for use on the battle field are very rare. And, the HURCULES is the first rescue robot for use on the battle field in South Korea. Primarily, a semiautonomous control strategy is applied to the HURCULES. The maneuvering stability of the HURCULES is needed when approaching and escaping a casualty while maneuvering on uneven terrain, and it maintains autonomously by the HURCULES. A variety of maneuvering experiments on various terrains were conducted, and satisfactory results for the casualty extraction task were obtained. In particular, the field experiments in this paper were performed at an accredited test site. Besides, additional experiments were conducted to enhance the field applicability.

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Distributed Robotic Computing

Natale

2020

Encyclopedia of Robotics

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The Ach Library: A New Framework for Real-Time Communication

Cited by 33 publications

References 12 publications

Unix Philosophy and the Real World: Control Software for Humanoid Robots

Unix Philosophy and the Real World: Control Software for Humanoid Robots

Development and control of a military rescue robot for casualty extraction task

Distributed Robotic Computing

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