Browsing by Subject "Real-time communication"

Now showing 1 - 2 of 2

Open Access
The Universal robot bus : a local communication infrastructure for small robots
(2008-12) Avcı, Akın
Design and construction of small autonomous mobile robots is a challenging task that involves the selection, interfacing and programming of a large number of sensor and actuator components. Facilitating this tedious process requires modularity and extensibility in both hardware and software components. This thesis concerns the development of a real-time infrastructural architecture called the Universal Robot Bus (URB), based on the popular Inter-Integrated Circuit (I 2C) bus standard. The main purpose of the URB is the rapid development and realtime interfacing of local nodes controlling small sensor and actuator components distributed on a mobile robot platform. It is designed to be very lightweight and efficient, with real-time support for RS232 or USB connections to a central computer. The URB infrastructure is inspired from the RiSEBus architecture, which is also an internal communication protocol for mobile robots, and developed to fit our requirements. URB offers a modular and extensible architecture for rapid and frequent changes to the platform design. Mobile robots also need to perform accurate sensory processing and estimation in order to operate in unstructured environments. Hence, the URB also supports real-time operations with reliable hardware and software components. The first novel contribution of this thesis is the design and implementation of automatic synchronization of data acquisition across multiple nodes. Our synchronization algorithm ensures that each node completes data acquisition tasks simultaneously well before read operations. Our experiments also prove that each individual node acquires data at approximately the same time instant. The second major contribution of this thesis is the incorporation of automated and unsupervised data acquisition across multiple nodes into the URB protocol. Autonomous data acquisition helps acquire periodic and frequently needed data over nodes. This enhancement reduces the computational load on the central processing unit and reduces bandwidth costs over the communication medium. This thesis also servers a survey on network architectures and protocols, network applications in robotics, synchronization algorithms, and applications of synchronization in robotics besides implementation details of the URB.
Open Access
An USB-based real-time communication infrastructure for robotic platforms
(2009) Öztürk, Cihan
A typical robot operates by carrying out a sequence of tasks, usually consisting of acquisition of sensory data, interpretation of sensory inputs for making decisions, and application of commands on appropriate actuators. Since this cycle involves transmission of data among electro-mechanical components of the robot, high quality communication is a fundamental requirement. Besides being reliable, robust, extensible, and efficient, a high quality communication infrastructure should satisfy all additional communication requirements that are specific to the robot it is used within. To give an example, for a rapid moving autonomous robot with a reactive controller which is intended to be used in time critical situations, a real-time communication infrastructure which guarantees demanded response times is required. The Universal Robot Bus (URB) is a distributed communication framework based on the widely used I2C standard, intended to be used specifically within rapid autonomous robots. Real-time operation guarantees are provided by defining upper bounds in response times. URB facilitates exchange of information between a central controller and distributed sensory and actuator units. Adoption of a centralized topology by connecting distributed units directly to a central controller creates a bottleneck around the central unit, causing problems in scalability, noise and cabling. In order to overcome this problem, URB is physically realized such that gateways (bridges) are incorporated between the central and distributed units which offload the work of the central unit and master the underlying I2C bus. Connection between the central unit and the gateway, the uplink channel, can be established using any high bandwidth communication alternative which successfully satisfies communication requirements of the system. The main contribution of this thesis is the design and implementation of the URB uplink channel using the well known Universal Serial Bus (USB) protocol. Although true real-time operation is not feasible with USB due to its polling mechanism, USB frame scheduling of 1ms is acceptable for our application domain. In this thesis, hardware components used in the USB uplink implementation as well as our software implementation are covered in detail. These details include the firmware running on the gateway, a Linux based device driver and a client control software that uses a USB library running on central controller, and finally sub-protocols between the application-driver and driver-firmware layers. The thesis also includes our experiments to estimate the performance of the USB uplink in terms of its roundtrip latency, bandwidth, scalability, robustness, and reliability. Finally, this thesis also serves as a reference on distributed systems, device driver development, Linux kernel programming, communication protocols, USB and its usage in real-time applications.