Smart taps for a single-wire industrial safety system

Patent metadata

Field	Value
Publication number	US-9846423-B2
Application number	US-201615187859-A
Country	US
Kind code	B2
Filing date	Jun 21, 2016
Priority date	Dec 22, 2014
Publication date	Dec 19, 2017
Grant date	Dec 19, 2017

Abstract

A single-wire safety system is provided that yields reliable safety device monitoring without the need for dual redundant signal channels. The safety system comprises a safety relay acting as a communications master device and one or more safety devices connected in series with the safety relay via a single-wire communication circuit. A smart tap device is used to interface safety devices that are not compliant with the single-wire protocol to the single-wire channel. The safety device or smart tap device farthest from the safety relay on the safety circuit modulates a safety signal with a recognizable pulse pattern that traverses the single-wire safety circuit to the safety relay via the intermediate safety devices or smart taps. The safety relay maintains safety mode as long as the pulse pattern is received and recognized. The architecture allows bi-directional communication of initialization, configuration, and diagnostic messages over the single-wire safety channel.

First claim

What is claimed is:

1. A smart tap device, comprising:
a memory that stores executable components;
a processor, operatively coupled to the memory, that executes the executable components, the executable components comprising:
a safe state detection component configured to determine whether a safety device connected to a slave device terminal of the smart tap device is in a safe state;
a pulse detection component configured to verify that a modulated pulse pattern of a safety signal received on an input terminal of the smart tap device corresponds to a defined pulse pattern;
a safety signal relaying component configured to output the safety signal on an output terminal of the smart tap device in response to verification that the modulated pulse pattern corresponds to the defined pulse pattern and a determination that a safety function of the safety device is valid; and
a message processing component configured to, in response to receipt, via the output terminal, of a request message requesting a reset of the safety device and containing a target address that matches an address of the smart tap device, momentarily remove power from a power supply line of the slave device terminal that provides power to the safety device.

2. The smart tap device of claim 1 , wherein the safe state detection component is further configured to identify a type of the safety device, and to configure functionality of an input line and an output line of the slave device terminal based on the type of the safety device.

3. The smart tap device of claim 1 , the executable components further comprising:
a pulse generating component configured to generate the modulated pulse pattern; and
a safety master mode component configured to enable the pulse generating component in response to detection of a terminator connected to the input terminal and to disable the pulse generating component in response to determining that the terminator is not connected to the input terminal.

4. The smart tap device of claim 1 , wherein the message processing component is further configured to, in response to receipt of an input message via the output terminal indicating that at least one of a downstream safety device or a downstream safety tap device is active, send an output message via the output terminal indicating that the smart tap device is active.

5. The smart tap device of claim 1 , wherein the message processing component is further configured to send an output message via the input terminal indicating that the safety tap device is active, and wherein the executable components further comprise:
a single-wire communication component configured to, in response to receipt of an input message via the input terminal indicating that at least one of an upstream safety device or an upstream safety tap device is active, establish a safety channel sub-link between the smart tap device and the at least one of the upstream safety device or the upstream smart tap device.

6. The smart tap device of claim 1 , wherein the executable components further comprises a device addressing component configured to, in response to receipt of an enumeration message via the output terminal containing an address of at least one of a downstream safety device or a downstream safety tap device, increment the address to yield an incremented address and assign the address to the smart tap device.

7. The smart tap device of claim 6 , wherein the message processing component is further configured to send an enumeration response message via the output terminal containing at least the incremented address and an indication of whether the smart tap device is a last addressable device on a safety circuit.

8. The smart tap device of claim 1 , wherein the target address is a first target address, and the message processing component is further configured to
in response to determining that a second target address contained in a device information request message received via the output terminal matches the address of the smart tap device, send an output message via the input terminal containing device information obtained from the safety device via the slave device terminal, and
in response to determining that the second target address contained the device information request message does not match the address of the smart tap device, send the device information request message via the input terminal.

9. The smart tap device of claim 1 , wherein the smart tap device further comprises a power tap configured to connect to a power supply and to provide power from the power supply to a first power supply line associated with the input terminal, and wherein the first power supply line is electrically isolated from a second power supply line associated with the output terminal.

10. The smart tap device of claim 1 , wherein the smart tap device is configured to detect a low voltage condition of the safety device, and the message processing component is further configured to send a low voltage warning message via the output terminal in response to detection of the low voltage condition.

11. The smart tap device of claim 1 , wherein the safety device is at least one of an emergency stop pushbutton, a light curtain device, a safety door switch, a safety mat device, an emergency pull-cord device, a laser scanner, a photoelectric sensor, or a safety contactor.

12. A method for operating a smart tap device, comprising:
determining, by a smart tap device comprising a processor, whether a safety device connected to a slave device terminal of the smart tap device is in a safe status;
comparing, by the smart tap device, a pulse pattern carried by a safety signal received on an input terminal of the smart tap device with a defined pulse pattern;
in response to determining that the pulse pattern matches the defined pulse pattern based on the comparing and that the safety device is in the safe status, outputting the safety signal via an output terminal of the smart tap device; and
in response to receipt, via the output terminal, of a reset request message requesting a reset of the safety device and containing a target address corresponding to an address of the smart tap device, momentarily removing, by the smart tap device, power from a power supply line of the slave device terminal that provides power to the safety device.

13. The method of claim 12 , further comprising:
identifying, by the smart tap device, a type of the safety device; and
configuring, by the smart tap device, functionality of at least one input line and at least one output line of the slave device terminal based on the type of the safety device.

14. The method of claim 12 , wherein the target address is a first target address, and the method further comprises:
in response to determining that an input message received via the output terminal is a request for device status information and that a second target address contained the input message matches the address of the smart tap device:
obtaining device status information from the safety device via the slave device terminal, and
sending the device status information as part of an output message via the input terminal; and

in response to determining that the second target address contained the input message does not match the address of the smart tap device, outputting the input message via the input terminal.

15. The method of claim 12 , further comprising:
detecting, by the smart tap device, a low voltage status of the safety device; and
in response to the detecting, sending, by the smart tap device, a low voltage warning message via the output terminal.

16.

Assignees

• Rockwell Automation Tech Inc

Inventors

• Nair Suresh R
• Foster Wayne R
• Harris Alex
• Papenbreer Rudolf Laurenz
• Machuletz Norbert
• Heckel Oliver
• Helpenstein Thomas
• Duros Van

Classifications

• G05B19/0425 Primary

  Safety, monitoring · CPC title