Process data exchange with guaranteed minimum transmission intervals
A control device includes first and second control modules. The first control module is configured to generate process data at t 1 , send the process data to the second control module via a communication channel, receive a response to the process data, and process the process data at t 4 . The second control module is configured to receive the process data from the first control module, process the process data at t 2 , generate the response at t 3 , and send the response to the first control module. The times t 1 , t 2 , t 3 , and t 4 are in chronological order. In various implementations, the first and second control modules jointly guarantee a minimum duration Δ1 between t 1 and t 2 . In various implementations, the second control module guarantees a minimum duration Δ2 between t 2 and t 3 . In various implementations, the first and second control modules jointly guarantee a minimum duration Δ3 between t 3 and t 4 .
1 . A control device for controlling an automated system, the control device comprising:
a first control module;
a second control module; and
a communication channel via which the first control module and the second control module are configured to exchange process data of the automated system,
wherein:
the first control module is configured to generate process data at a first time t 1 , send the process data to the second control module via the communication channel, receive a response to the process data from the second control module, and process the process data at a fourth time t 4 ;
the second control module is configured to receive the process data from the first control module, process the process data at a second time t 2 , generate the response at a third time t 3 , and send the response to the first control module;
the times t 1 , t 2 , t 3 , and t 4 are in chronological order,
the first control module and the second control module are jointly configured to guarantee at least one of: a first minimum duration Δ1 between the first time t 1 and the second time t 2 , or a second minimum duration Δ2 between the third time t 3 and the fourth time t 4 , by transmitting the process data redundantly and ensuring specific time characteristics;
the first control module is configured to transmit the process data redundantly by shifting a first instance of the process data into a transmit buffer of the communication channel at a first point of time t a and by shifting a second instance of the process data into the transmit buffer of the communication channel at a second point of time t b ; and
the first control module is configured to ensure the specific time characteristics by starting a first time monitoring, which determines a first time interval between the points of time t a and t b , and by shifting the second instance of the process data into the transmit buffer only in case the determined first time interval exceeds a defined minimum value.
2 . The control device of claim 1 wherein the second control module ensures the specific time characteristics by starting a third time monitoring, which determines a time interval between reception of the first instance of the process data and reception of the second instance of the process data, only in case the second control module receives the first instance of the process data.
3 . The control device of claim 1 wherein:
the first instance of the process data and the second instance of the process data are redundant data telegrams of the process data; and
the first control module provides the first instance of the process data and the second instance of the process data with consecutive instance numbers.
4 . The control device of claim 1 wherein the first control module sends and receives the process data cyclically, monitors a number of cycles between the first time t 1 and the fourth time t 4 as a round-trip time and triggers a safety-related action in case the round-trip time exceeds a defined value.
5 . The control device of claim 1 wherein:
the first control module processes the process data according to a first local cycle;
the second control module processes the process data according to a second local cycle;
the first local cycle and the second local cycle have the same period; and
the first minimum duration Δ1 and the second minimum duration Δ 2 are each shorter than the period.
6 . The control device of claim 5 wherein the first control module sends the first instance and at least the second instance of the process data to the second control module within the first local cycle.
7 . The control device of claim 1 wherein the first control module and the second control module each have a fail-safe implemented processing unit that enables at least one of a fail-safe execution of a user program and a fail-safe input/output of the process data.
8 . The control device of claim 7 wherein each fail-safe implemented processing unit is configured to ensure a fail-safe communication via the communication channel independent of a design of the communication channel.
9 . The control device of claim 7 wherein each fail-safe implemented processing unit is configured to provide fail-safe time monitoring on the respective first control module and the second control module.
10 . A control device for controlling an automated system, the control device comprising:
a first control module;
a second control module; and
a communication channel via which the first control module and the second control module are configured to exchange process data of the automated system,
wherein:
the first control module is configured to generate process data at a first time t 1 , send the process data to the second control module via the communication channel, receive a response to the process data from the second control module, and process the process data at a fourth time t 4 ;
the second control module is configured to receive the process data from the first control module, process the process data at a second time t 2 , generate the response at a third time t 3 , and send the response to the first control module;
the times t 1 , t 2 , t 3 , and t 4 are in chronological order,
the first control module and the second control module are jointly configured to guarantee at least one of: a first minimum duration Δ1 between the first time t 1 and the second time t 2 , or a second minimum duration Δ2 between the third time t 3 and the fourth time t 4 , by transmitting the process data redundantly and ensuring specific time characteristics;
the second control module is configured to transmit the response to the process data redundantly by shifting a first instance of the response into a transmit buffer of the communication channel at a third point of time t a and by shifting a second instance of the response into the transmit buffer of the communication channel at a fourth point of time t b ; and
the second control module is configured to ensure the specific time characteristics by starting a second time monitoring, which determines a second time interval between the points of time t a and t b , and by shifting the second instance of the response into the transmit buffer only in case the determined second time interval exceeds a defined minimum value.
11 . The control device of claim 10 wherein the first control module ensures the time characteristics by starting a fourth time monitor, which determines a time interval between reception of the first instance of the response and reception of the second instance of the response, only in case the first control module receives the first instance of the response.
12 . The control device of claim 10 wherein:
the first instance of the response and the second instance of the response are redundant data telegrams of the response; and
the second control module provides the first instance of the response and the second instance of the response with consecutive instance numbers.
13 . The control device of claim 10 wherein:
the first control module is configured to process the process data according to a first local cycle;
the second control module is configured to process the process data according to a second local cycle;
the first local cycle and the second local cycle have the same period; and
the first minimum duration Δ1 and the second minimum duration Δ2 are each shorter than the period.
14 . The control device of claim 13 wherein the second control module is configured to send the first instance and at least the second instance of the response of the process data to the first control module within the second local cycle.