Data processing: generic control systems or specific application – Generic control system – apparatus or process – Plural processors
Reexamination Certificate
1999-02-12
2001-03-13
Grant, William (Department: 2786)
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Plural processors
C370S222000, C370S242000, C370S405000, C700S082000
Reexamination Certificate
active
06201995
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The field of the invention pertains to methods and apparatus for connecting nodes in a control network having multiple data buses.
2. Background
Automated control systems are commonly used in a number of manufacturing, transportation, and other applications, and are particularly useful to control machinery, sensors, electronics, and other system components. For example, manufacturing or vehicular systems may be outfitted with a variety of sensors and automated electrical and/or mechanical parts that require enablement or activation when needed to perform their predefined functions. Such systems commonly require that functions or procedures be carried out in a prescribed order or with a level of responsiveness that precludes sole reliance on manual control. Also, such systems may employ sensors or other components that require continuous or periodic monitoring and therefore lend themselves to automated control.
As the tasks performed by machinery have grown in number and complexity, a need has arisen for ways to exercise control over the various components of a system rapidly, efficiently and reliably. The sheer number of system components to be monitored, enabled, disabled, activated, deactivated, adjusted or otherwise controlled can lead to difficulties in designing and implementing a suitable control system. As the number of system components to be controlled is increased, not only is the operation of the control system made more complicated, but also the wiring and inter-connections of the control system are likewise more elaborate. In addition, greater reliance on automated control has resulted in larger potential consequences if the automated control system fails.
Traditionally, control systems in certain applications, such as transit vehicles and railcars, have relied upon relay-based control technology. In such systems, relays and switches are slaved to a logic circuit that serves to switch signal connections. This approach requires a large number of relays and a substantial amount of wiring throughout the vehicle. In some instances distributed processors or logic circuits may be used for subsystems such as the door, but these processors or logic circuits often take up significant space and can be costly to maintain.
A substantial improvement has recently been made in the field of control systems. An improved network control system recently developed uses a dual-bus architecture along with distributed controllers. In this improved network control system, a primary bus forms a high-speed, bi-directional communication link interconnecting a main data bus controller with distributed slave modules, one of which acts as a second data bus controller connected to a secondary, low-speed data bus. The slave modules are generally connected to various input/output ports. The second data bus controller can be connected to second-tier slave modules over the secondary, low-speed data bus. The main data bus controller, secondary data bus controller, first-tier slave modules, second-tier slave modules, input/output ports and other system components collectively form a hierarchical system wherein the main data bus controller supervises the first-tier slave modules, including the second data bus controller, the second data bus controller supervises the second-tier slave modules, and the first-tier slave modules and second-tier slave modules supervise their assigned input/output functions.
While the dual-bus control network as described above has many advantages, there are also ways in which it could be improved further. The dual-bus control network architecture as currently known in the art generally relies on a single top-level main data bus controller. If the main data bus controller fails, system performance will be adversely impacted. Also, the possibility of a short circuit occurring, particularly over a region of the bus, is a constant danger. In addition to disrupting communication signals among the components accessing the bus, a short circuit can be difficult to trace and cause substantial disruption of system service while maintenance personnel attempt to locate the short circuit Furthermore, while the dual-bus network control architecture reduces wiring needed in a vehicle or other automated system, simplification of wiring connections would lead to greater ease of implementation and maintenance.
Accordingly, it would be advantageous to provide a network control system that has a means for recovering from a failure in a main data bus controller or otherwise mitigating the effects such a failure. It would further be advantageous to provide a network control system that reduces the impact of a short circuit and enables rapid identification of the location of a short circuit by maintenance personnel. It would further be advantageous to provide a distributed network control system with simplified wiring and connections.
SUMMARY OF THE INVENTION
The invention provides in one aspect a technique for connecting nodes, such as master nodes and slave nodes, in a hierarchical, multi-bus control network.
In one aspect of the invention, a multiple-bus hierarchical control network is provided. A first-tier master node controls a plurality of first-tier slave nodes using a first common bus for communication. One of the first-tier slave nodes is connected to a second common bus, and operates as a second-tier master node for a plurality of second-tier slave nodes connected to the second common bus. Each master node comprises at least a downlink transceiver, and each slave node comprises at least an uplink transceiver. All of the nodes in the control network are connected in a continuous loop configuration with each segment of the loop comprising a cable connector of either a first type (feed thru) or a second type (crossover). Each cable connector comprises a pair of signal wires for each bus. The type of cable connector between any two adjacent nodes in the loop is related according to which of the uplink or downlink transceiver should be connected to which bus.
In a preferred embodiment of the invention, a master node serves as a controller for a multiplicity of slave nodes. The master node polls the slave nodes periodically. Each of the slave nodes comprises a failure mode detector whereby, if a slave node fails to receive a message from the master node within a certain fixed period of time, then the slave node takes over control for the master node.
In another aspect of the invention, prioritized redundant backup control for the master node is provided by establishing an order in which the slave nodes take over the master node, or substitute master node, in the case of multiple node failures. Preferably, each slave node is programmed to detect a failure mode condition after a different amount of time than the other slave nodes are programmed with. When the first slave node programmed with the shortest failure mode detection time detects a failure mode condition, it takes over for the master node and becomes the substitute master node. Should the substitute master node also fail, then the slave node programmed with the next shortest failure mode detection time will detect a failure mode condition and take over for the substitute master node, becoming the second substitute master node. Likewise, in turn each slave node has the capability of becoming the master node when its programmed failure mode detection time elapses. In this manner, prioritized redundant backup control is achieved for the master node.
Should a failure of the first-tier master node occur, any of the first-tier slave nodes connected to the first common bus can take over the first-tier master node, doing so according to their programmed priority. Should a failure of the second-tier master node occur, any of the second-tier slave nodes connected to the second common bus can take over the second-tier master node, doing so according to their programmed priority. Redundant master control is thereby provided for both the first tier and second tier in the hierarchical control
Garland Steven R.
Grant William
I/O Control Corporation
Lyon & Lyon LLP
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