In this paper, the application of transputers to improve the performance of navigation and positioning systems is considered. The development of increasingly complicated navigation and positioning systems is examined to highlight common features such as high data capture rates, sensor diversity and high processing loads. It is these factors which make tranputer technologies particularly appropriate for such systems.
Transputers are a new generation of microprocessors which extend the speed and flexibility of parallel processing beyond the capacity of currently available chips. An overview of their capabilities in relationship to two commonly used microprocessors is presented.
Finally, in order to demonstrate how transputer technology can, indeed, handle the requirements of navigation systems, a specific example of their appropriateness for an advanced Doppler sonar navigation system is considered. Their performance is compared with two alternative systems built up from conventional microprocessors. It is shown that the transputer-based design can indeed satisfy the requirements for fast parallel processing coupled with fast data read-in, whilst offering low power, low development costs and flexibility in design.
In the offshore industry, there is a continuing demand to improve the performance of navigation and positioning systems. These systems provide the operator with the information necessary to minimize the risk of the operation in hand. Risks involved in offshore operations range from an expensive failure to complete the task to encountering unforeseen problems which inevitably cause time-scales and costs to increase rapidly.
As the demands made throughout the industry continue to become more exacting, these systems must perform more reliably, with improved flexibility and increased accuracy. For example, positioning installations (whether they are cables, pipelines or production platforms) to a given degree of accuracy is less time-consuming in continental shelf water depths than if an identical operation were performed in deeper continental slope waters. Indeed, it may well be that entirely new modes of operation have to be invoked in deep water situations where a much higher proportion of the tasks have to be performed by sophisticated remotely operated vessels (ROVs). Furthermore, in may require specialized equipment such as a deep-towed high-resolution side-scan sonar equipment like GLORIA II. Such systems require precise positioning in order to gain the maximum benefit from the increased picture resolution. This system has been used recently by British Telecom to delineate local troughs and canyons on the continental slope of the Western Approaches. A detailed knowledge of the local seafloor topography is required to assist in determining the exact branching point for the UK link into the new transatlantic fibre-optic communication cable (Newsfocus, 1985).
Fig. 1. Function block diagram of a modern integrated navigation systems with an additional towed platform navigation system. Although, when depicted at this level, the system appears relatively simple, the ability to process data from a wide range of sensor concurrently in real time imposes severe design constraints on each data channel processor and also in merging these channels. This aspect is particularly well-suited to transputer-based designs (available in full paper)