Development of a Versatile Test-Bed "Twin-Burger" toward Realization of Intelligent Behaviors of Autonomous Underwater Vehicles


III. ONBOARD COMPUTER SYSTEM

The onboard computer system must be able to control the hardwares as well as to execute the software modules for high level processes. The Twin-Burger has many sensors, actuators and communication systems. The input and output signals from these instruments should be handled simultaneously through the hardware interfaces in real time because they are closely related to the vehicle control problems.

Multi-processor and parallel processing architecture is suitable for keeping these processes in real time while executing the high level softwares. In order to realize this kind of architecture, a multi-processor system based on INMOS Transputers[9] is adopted as the computer system for the Twin-Burger.

************Fig.4 A Block Diagram of the Twin-Burger Computer System*******

Fig.4 shows the block diagram of the Twin-Burger computer system. The main Transputer array consists of ten T800 TRAMs (TRAnsputer Modules) mounted on a Double Extended Eurocard size mother board:

  1. a video image processing TRAM,
  2. a TRAM with 8 Mbyte RAM as a data storage, and
  3. eight TRAMs with 1 Mbyte RAM.

In addition, four T425 Transputers manage the hardware interfaces, such as A/D converters, pulse counters, etc. These fourteen Transputers are wired as a Transputer network with high speed serial links called the Transputer links[9]. The configuration of the network can be partly arranged by using software wiring capability. The host PC and the onboard computer system can be connected with the Transputer link by converting its signals to RS422 differential signals for long distance data transmission.


**************Fig. 5 Structure of the Basic Software System*************

Fig.5 shows a structure of the Twin-Burger parallel distributed software system which is implemented onto the onboard computer system for basic operations of the vehicle. The system consists of several software modules, which are categorized into two groups:

  1. hardware control modules that run on T425 Transputers for direct handling of the hardware interfaces and
  2. software modules to realize necessary functions for the vehicle as a test bed, such as monitoring the vehicle's status, checking the actuators' movement, collecting data from the onboard data storage and passing them to the host PC, etc.

All these software modules are executed parallel on the configured Transputer network while communicating with each other. It should be noted that this system is not for mission execution but for smooth vehicle operation in experiments. The mission execution software is developed according to the Distributed Vehicle Management Architecture, which is proposed by the authors[4, 10], by using this basic software system as a harness to the vehicle hardware system.


Last modified: Thur July 6 1995