Safety network system, safety slave, and communication method

• US 20040210323A1
• Filed: 06/07/2004
• Published: 10/21/2004
• Est. Priority Date: 06/22/2001
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Nakamura, Toshiyuki, Muneta, Yasuo
• Granted Patent: US 7,050,860 B2
• Time in Patent Office: Days
• US Class Current: 700/21
• CPC Class Codes: G05B 19/058 Safety, monitoring
• CPC Class Codes: G05B 2219/1179 Safety, on error, fault, block, inhibit output
• CPC Class Codes: G05B 2219/1195 Critical I-O monitored by safety module connected to plc, other I-Os by plc self
• CPC Class Codes: G05B 9/02 electric

Abstract

The safe PLC1 and the safe slaves 2 are connected with each other via the safe network 3. The safe PLC has the function of transmitting a request of safety information by broadcast message to the safe slaves. The safe slaves are each provided with a safety information transmission function for transmitting safety information indicative of whether the safe slave is in a safe condition or not; and a changing means for changing a priority of a transmission frame which carries the safety information. As a result, when the safe slaves send back safe responses at once in response to the broadcast message, safety information (danger) with a higher priority is transmitted ahead of others to the safe PLC.

Claims

1. A safe network system composed of a safe controller and safe slaves which are connected with each other via a safe network, wherein

the safe controller has a function of transmitting a request for safety information by broadcast message to the safe slaves;

the safe slaves each comprise;

a safety information transmission function for transmitting safety information indicative of whether the safe slave is in a safe condition or not; and

a changing means for changing a priority of a transmission frame which carries the safety information, the changing means setting the priority higher when the safe slave is not in the safe condition than when the safe slave is in the safe condition.

2. A safe slave for being connected with a safe network system composed of a safe controller and safe slaves which are connected with each other via a safe network, the safe slave comprising:

a safety information transmission function for transmitting safety information indicative of whether the safe slave is in a safe condition or not; and

a changing means for changing a priority of a transmission frame which carries the safety information, the changing means setting the priority higher when the safe slave is not in the safe condition than when the safe slave is in the safe condition.

3. A communication method in a safe network system composed of a safe controller and safe slaves which are connected with each other via a safe network, wherein

the safe controller makes a transmission request of safety information by broadcast message in a prescribed timing to the safe slaves connected with the safe network, and

a safe slave received the transmission request transmits the safety information indicative of whether the safe slave is in a safe condition or not in response to the transmission request by changing the priority of transmission in accordance with the contents of the safety information.