Multiple controllers, coordination

When there are multiple controllers (human and/or automated), control actions may be inadequately coordinated, including unexpected side effects of dedsions or actions or conflicting control actions. Communication flaws play an important... 

Coordination among Multiple Controllers At this level, each component (aircraft) had a single controller and thus coordination problems did not occur. They were rife, however, at the higher control levels. 

This level of the control structure contains more examples of inconsistent mental models and asynchronous evolution. In addition, this control level provides interesting examples of the adaptation over time of specified procedures to accepted practice and of coordination problems. There were multiple controllers with confused and overlapping responsibilities for enforcing different aspects of the safety requirements and constraints (figure 5.8). The overlaps and boundary areas in the controlled processes led to serious coordination problems among those responsible for controlling aircraft in the TAOR. 

Coordination among Multiple Controllers As mentioned earlier, coordination problems are pervasive in this accident due to overlapping control responsibilities and confusion about responsibilities in the boundary areas of the controlled process. Most notably, the helicopters usually operated close to the boundary of the TAOR, resulting in confusion over who was or should be controlling them. 

Some constraints on the two system components (ATC and TCAS) are closely related, such as the requirement to provide advisories that maintain safe separation between aircraft. This example of overlapping control raises important concerns about potential conflicts and coordination problems that need to be resolved. As noted in section 4.5, accidents often occur in the boundary areas between controllers and when multiple controllers control the same process. The inadequate resolution of the conflict between multiple controller responsibilities for aircraft separation contributed to the collision of two aircraft over the town of Uberlingen (Germany)... 

When multiple controllers are engaging in coordinated control of a process, incon-sistenqr between their process models can lead to hazardous control actions. Careful design of communication channels and coordinated activity is required. In aircraft, this coordination, called crew resource management, is accomplished through careful design of the roles of each controller to enhance communication and to ensure consistenqr among their process models. 

That a carefully designed and coordinated process such as air traffic control can suffer such problems with coordinating multiple controller process models (and procedures) attests to the difficulty of this design problem and the necessity for careful design and analysis. 

Inadequate coordination or communication among multiple controllers... 

MPP. This multiple instruction stream, multiple data stream or MIMD class of parallel computer integrates many (from a few to several thousand) CPUs (central processing units) with independent instruction streams and flow control coordinating through a high-bandwidth, low-latency internal communication network. Memory blocks associated with each CPU may be independent of the oth-... 

Control coordinates all activities. As mentioned previously, unless multiple processors exist within the... 

Each resei voir generally has a dominant drive, an optimal pattern ofwell locations, and a maximum efficient rate of production (MER), which, if exceeded, would lead to an avoidable loss of ultimate oil recovery. Unfortunately, oil, gas, and water are not evenly distributed within the reservoir. With multiple leases above the reservoir, some lease owners will have more oil, gas, or water than will others, and coordination among competing firms in well placement and in controlling production rates is difficult. Efficient production of the reservoir suggests that some leases not be produced at all. Further, since each firm s production inflicts external costs on the other firms on the formation, some mechanism must be found to internalize those costs in production decisions. 

B. Grocholsky, A. Makarenko, and H. Durrant-Whyte, Information-theoretic coordinated control of multiple sensor platforms, in Proceedings of the IEEE International Conference on Robotics and Automation, Taipei, Taiwan, September 2003, pp. 1521-1526. 

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