Electricity: motive power systems – Positional servo systems – Time-sharing or multiplexing systems
Reexamination Certificate
1998-05-08
2001-10-02
Sircus, Brian (Department: 2839)
Electricity: motive power systems
Positional servo systems
Time-sharing or multiplexing systems
C318S625000, C318S034000, C318S105000, C307S029000, C307S038000, C362S085000, C315S295000, C315S317000
Reexamination Certificate
active
06297610
ABSTRACT:
The present invention relates to a control system for controlling a plurality of electrical devices.
The invention is particularly but not exclusively applicable to the control of electrical devices such as electric motors especially those used for control of stage equipment.
In the control of stage equipment in a theater there is a need for precise and synchronized control of a plurality of motors which may be used for moving and/or wincing stage equipment. In these applications safety considerations are paramount because any fault may result in serious injuries to equipment or personnel. Typically the motors required to drive winches and the like are coupled to a variable speed drive (VSD) which in turn is coupled to a central computer usually via an axis controller. The VSD provides output power to the motor to control its speed in a precise way. The motors may for example be DC or AC either single or three phase. The drives must provide the correct control voltage, current or frequency input to the motor to achieve the desired speed. The axis controller generates control signals which are coupled to the VSD and controls such things as the rate of acceleration, maximum speed, duration of maximum speed, rate of deceleration and precise end-point positioning. The central controller on the other hand provides the highest level control and it usually comprises a computer which is programmed to select which pieces of stage equipment are moved, where they are moved to and when they are moved. The central controller provides appropriate control signals to the axis controllers.
In an ideal system, there would be an axis controller and VSD for each motor. In this way the central controller can effectively control all of the motors so that all of the motors can be simultaneously operated. Whilst this may be appropriate for relatively small theaters it is not usually appropriate for large theaters where there may be more than 60 motors to be controlled. It is not appropriate in the larger systems because of the substantial expense involved in providing separate axis controllers and VSDs for each motor. Further, there would be a substantial amount of cabling required to couple the components together.
Economies can be realized if the number of motors required to run simultaneously is lower or substantially lower than the total number of motors and this is frequently the case. In this case, the number of VSDs can be reduced to the number of motors required to run at the same time. However, a mechanism needs to be put in place which can variously connect a group of motors required at any given time to available VSDS.
In the theater flying system application area, the connection of a group of motors to their designated VSDs must be made quickly, i.e. in less than half of one second, This precludes the use of a “manual patch” in which an operator plugs a cable from each required motor into an available VSD. Some form of “automatic patch” is needed, where the connections of all power and signal routes between motors and VSDs can be made using controlled switches such as relays, contactors, solid-state switches, etc.
Conceptually, an automatic patch can be represented by a rectangular matrix. Ideally, a “switch” (actually a set of switches, because there are many conductors required to be routed between a winch and its associated drive) would be located at each cross point in the matrix to enable any combination of motors (up to the total number of VSDs) to be connected to a drive each. In practice, this is not economically feasible and would cost more than a system having one VSD per motor.
As an acceptable compromise, a subset of matrix cross points are populated with switches. The number of switches allocated to each motor, i.e. cross points populated in each row of the matrix, will determine the probability of being able to assign a given motor in a group to an available VSD. The probability decreases, of course, as the group size increases. This probability can be quite high for small group sizes, e.g. up to 100%, but it drops sharply as the group size approaches the number of VSDs.
One automatic motor-drive patch system has been proposed but it tended to be over complicated and cumbersome to implement. In this system the central controller is coupled to each of the patch switches so that the central controller acting through the patch switches determines which of the motors are coupled to which of the VSDS. This of course requires considerable cabling and also reliability is not optimized. An example of such a system is the scenery flying system implemented at The Olivier Theater, London and reference is made to a paper entitled
The National Theater's Scenery Hoist Matrix Scheme
by S. K. Das and R. H. Keenan.
An object of the present invention is to provide a novel control system which is particularly applicable to an automatic motor-drive patch system.
The invention herein concerns the architecture of the patch and control logic, i.e. the method by which the patch switches are inter-connected and controlled.
In the system of the invention, the control logic is distributed in the network which couples the central controller to the electrical devices to be controlled.
According to the present invention there is also provided a control system for controlling a plurality of electrical devices, a central controller for controlling selected functions of said devices, a plurality of device drivers for providing drive signals to said electrical devices, the number of device drivers being less than the number of devices and a network coupled between said device drivers and said devices, said network including logic elements which determine which devices are coupled to respective device drivers.
Preferably the logic elements are operable to determine which devices are coupled to respective drivers without direct coupling between the central controller and said logic elements.
Preferably, the central controller comprises a computer which coordinates network activity.
According to a further aspect of the invention there is provided a stage apparatus control system including a central controller, a plurality of motors and a patch network including patch buses for coupling the central controller to the motors characterized in that elements of the patch network are coupled to the central controller through the patch buses and are not independently connected thereto.
The invention also provides a stage control system comprising a central computer, a patch network, a plurality of motors characterized in that a satellite processor is provided for each motor.
The invention also provides a stage control system comprising a central computer, a patch network, a plurality of motors characterized in that the system includes a plurality of axis controllers and wherein the axis controllers include logic elements which cooperate in the control of the patch network.
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Bauer Michael John
Fregon Edward John
Bytecraft Research Pty, Ltd.
Seed IP Law Group PLLC
Sircus Brian
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