Safety controller with safety response time monitoring
First Claim
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1. A safety industrial controller receiving signals from electrical sensors on a safety process and providing signals to electrical actuators on the safety process, the safety industrial controller comprising:
- input circuits receiving input signals from sensors and transmitting them to logic circuitry before a first worst-case delay;
logic circuitry receiving the input signals from the input circuits to create at least one output signal based on the input signals and transmitted to an output circuit before a second worst case delay; and
output circuit receiving the output signal from the logic circuitry to output the output signal to an actuator before a third worst case delay only if the time elapsed since the input circuits received at least one of the input signals is less than a predetermined time limit, the predetermined time limit being less than the sum of the first, second, and third worst case delays, and otherwise the output circuit entering a predetermined safety state.
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Abstract
A safety controller having a total worst case propagation delay, exceeding the required propagation delay required by a safety process, may be used to control the safety process by monitoring actual delays in signal processing in the safety controller and moving to a safety state if a signal delay exceeds an amount less than the total worst case propagation delay.
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Citations
30 Claims
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1. A safety industrial controller receiving signals from electrical sensors on a safety process and providing signals to electrical actuators on the safety process, the safety industrial controller comprising:
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input circuits receiving input signals from sensors and transmitting them to logic circuitry before a first worst-case delay; logic circuitry receiving the input signals from the input circuits to create at least one output signal based on the input signals and transmitted to an output circuit before a second worst case delay; and output circuit receiving the output signal from the logic circuitry to output the output signal to an actuator before a third worst case delay only if the time elapsed since the input circuits received at least one of the input signals is less than a predetermined time limit, the predetermined time limit being less than the sum of the first, second, and third worst case delays, and otherwise the output circuit entering a predetermined safety state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of operating a safety industrial controller receiving input signals from electrical sensors on a safety process at input circuits and transmitting the input signals to logic circuits to produce output signals transmitted in turn to output circuits and then to electrical actuators on the safety process, the method comprising the steps of:
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at the input circuitry, transmitting received input signals to logic circuitry before a first worst-case delay; at the logic circuitry, creating at least one output signal based on the input signals and transmitting the output signals from the logic circuitry to an output circuit before a second worst case delay; and at the output circuitry, outputting the output signal to an actuator before a third worst case delay only if the time elapsed since the input circuits received at least one of the input signals is less than a predetermined time limit, the predetermined time limit being less than the sum of the first, second and third worst case delays, and otherwise the output circuit entering a predetermined safety state. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification