Process monitor for a weld controller
First Claim
1. A digital weld control system for a resistance welder supplied from an AC line voltage source comprising:
- A. a phase reference clock for establishing a fundamental time base;
B. a voltmeter synchronized with the fundamental time base for measuring selected parameters of the AC line voltage source;
C. a current meter for measuring various parameters of weld load current;
D. a firing, control synchronized with the fundamental time base;
E. a weld sequence controller for implementing a weld program by generating weld pulse commands; and
F. a weld process controller using the generated weld pulse commands to generate a sequence of firing commands sent to the firing control for generating firing pulses to control load current and for maintaining an internal dynamic model of load impedance calculated from the measured selected parameters of the AC line voltage source and weld load current and further including means to generate weld range events when a difference is detected between a measured load impedance and the internal dynamic model of load impedance by a prescribed amount.
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Accused Products
Abstract
A weld controller maintains an internal dynamic model of load impedance, which tracks normal impedance variations that occur as the weld tooling degrades. The weld controller contains a weld process monitor function that tests an estimated load impedance of a weld schedule presently under execution against an internal dynamic model and generates events when characteristics of the estimated load impedance of the present weld falls outside an operator definable band, indicating a problem with the workpiece presently being welded. The weld controller further includes the capability to accept a static model of the load impedance that is used as the reference impedance for the weld control and tooling. The weld controller also includes means to declare an event when characteristics of the dynamic model differ from the static model by an operator-defined amount. The weld controller allows a distinction to be made between a short-term difference in load impedance, generally indicative of a weld process variation and the long-term difference in load impedance, generally indicative of tooling degradation. This provides for tighter controls of weld process variations than could previously be achieved, coupled with an indication of incipient tooling faults.
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Citations
20 Claims
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1. A digital weld control system for a resistance welder supplied from an AC line voltage source comprising:
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A. a phase reference clock for establishing a fundamental time base; B. a voltmeter synchronized with the fundamental time base for measuring selected parameters of the AC line voltage source; C. a current meter for measuring various parameters of weld load current; D. a firing, control synchronized with the fundamental time base; E. a weld sequence controller for implementing a weld program by generating weld pulse commands; and F. a weld process controller using the generated weld pulse commands to generate a sequence of firing commands sent to the firing control for generating firing pulses to control load current and for maintaining an internal dynamic model of load impedance calculated from the measured selected parameters of the AC line voltage source and weld load current and further including means to generate weld range events when a difference is detected between a measured load impedance and the internal dynamic model of load impedance by a prescribed amount. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A digital weld control system for a resistance welder of the type connecting and disconnecting through a welding contactor, a welding transformer load from an alternating current weld power source to control timing periods of a welding sequence and a level of heat intensity in the weld to ensure quality welds, the digital weld control system comprising:
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A. a phase reference clock for establishing a fundamental time base; B. a voltmeter synchronized with the fundamental time base for measuring selected parameters of the AC line voltage source; C. a current meter for measuring various parameters of weld load current; D. a firing control synchronized with the fundamental time base; E. a weld sequence controller for implementing a weld program by generating weld pulse commands; and F. a weld process controller for establishing a static reference model of load impedance indicative of the intended operation of the weld control system, and for maintaining an internal dynamic model of load impedance calculated from the measured selected parameters of the AC line voltage source and weld load current and means for generating weld control system trend faults when the internal dynamic model of load impedance differs from the static reference model of load impedance by a prescribed amount. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification