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1 Research Reports of the National Institute of Industrial Safety, NIIS-RR UDC * ** *** **** An Inquiry into Basic Safety Requirements of Field-bus Network for Safety Control* by Tsuyoshi SAITO**, Hideo NAKAMURA*** and Masaki MIURA**** Abstract: In the bottom layer of a hierarchized computer network for manufacturing in a factory, serial communication networks, in which sensors, actuators and logic controllers are connected to a single wire the bus that has two endpoints, are collectively termed Field Buses. Recently, application of the field bus technology to transmission of safety-related information from protective sensing devices for human safety to control parts of industrial machinery shows rapid progress. However, dangerous transmission errors on field buses and preventive measures against them have still not been investigated enough. The safety-related information transmission requires special considerations to ensure the promptness and inerrancy as well as the conventional hard-wired failsafe interlock system. This paper deals with the derivation of basic safety requirements of field bus network to transmit safety-related information Safety Field Bus SFB and the experimental verification of safety performance of the SFB. From the perspective of the conventional fail-safe theories and requirements of international standards concerning safety of machinery, the four requirements are showed for the redundant architecture of processing interface controller, the cyclic signal transmission to confirm the normalcy of communication function and the double error detection coding of telegrams. In order to establish a concrete example of SFB system, a test model of safety control device capable of connected to SFB is experimentally produced by using a single board bit microcomputer and a prepared SFB controller chip based on the controller area network CAN bus. Using the experimental SFB system including the test model, its response time to detect dummy hardware failures and to perform a designated safety function are measuared. From the results of the measurements, it is confirmed that the experimental SFB system has enough potential to achieve a higher safety integrity level than the level described on the associated international standards, however the importance of improvement in its slow response time was revealed. Keywords; Safety control, Field-bus network, Safety-related information, International standards, Dependable computing, Redundant diverse processor, Interface gate circuit **** **** Mechanical and System Safety Research Group **** Nihon University, College of Science aud Technology **** Kasuga Electric Works Ltd.

2 NIIS-RR- 1 PLC,, CANControl Area Network Bus 2 PLC LAN CAN 2 1 CAN Bosch ISO Fig. 1 Fig. 1 Schematic diagram of CAN bus.

3 CAN Fig. 1 Bus Interface Unit BIU CAN LSI BIU Fig. 1 kbit/s CAN High CAN Low Fig. 2 Fig. 3 CAN CSMA/CA Carrier Sense Multiple Access with Collision Avoidance Start of Frame SOF Identifier Fig. 2 An example of CAN bus comunication. 8 Fig. 2 CAN CRC Cyclic Redundancy Check Code CRC CRC Acknowledgment ACK 2 2 CRC ID Fig. 3 Fig. 2 Configuration of CAN standard data frame. 3

4 NIIS-RR-, ISO IEC 3 1 BIU BIU BIU Fig. 4 Fig. 4 a BIU Fig. 4 b Fig. 4 a Fig. 4 b 3 2 t, t S t Sc t E t S t, Sc t E t, t S t Sc t E t S t Sc t E t ON OFF Fig. 4 Redundant structure of field-bus system for safety control. Fig. 2

5 S ton t D k S t kd t kd k S t Sc kd E kd t Sc t Sc kd t E t E kd t S t t kd E kd D E kd D E kd D ms D 3 2 Fig. 3 CRC Fig. 4 b CRC CRC CRC CAN Safety BUS p Fig. 5 CRC CAN CRC CRC / CRC CRC CRC h Fig. 5 Configuration of a data frame of Safety bus p protocol Fig. 2

6 NIIS-RR- SC m n HW BC p v SC CRC BC CRCHW h n m m vh p Tcc h BIU LSI SC BC Fig. 5 BC SC h 3 4, Tcc Table Table 1 Relationship between transmission errors and preventive measures Table 1

7 Well-tried BIU BIU BIU BIU. BIU 4 4 Safety BUS p Safety BUS p Pilz Management Device MD BIU. Fig. 6 CAN BIU CAN A ACAN CAN CRC CAN A B Safety BUS p CRC H H CAN H MD IDID MD Safety BUS p 4 1 Safety BUS p CAN BIU H / F H Photo 1 Photo. 1 Photo. 1 Test model of a safety control device capable of connecting to Safety BUS p.

8 NIIS-RR- Safety BUS p I O. ON OFF Fig. 7 A B hh h AAh A B BIU CAN MD. DCAN DCAN Tcycle Tbus Tdelay Safety BUS p CAN MD Tdata Ddata 4 2 D CAN Tbus T delay Tbus Tdelay MD MD Tcycle Tcycle CAN Fig. 6 Fig. 2 Fig. 7 Fig. 2 Schematic block diagram of test model. An example of data transmission to confirm the normalcy of data buses and l/o ports.

Ddata Tdata Tcycle Tbus Tdelay 4 3 MD Photo 2MD I O MY N OFF CANCAN Low IC DCANFig. 8 Tdelay ms Tbus ms ms ms Tcycle DCAN DCAN DCAN Tcycle Tbus Tdelay Fig.

9 Ddata Tdata Tcycle Tbus Tdelay 4 3 MD Photo 2MD I O MY N OFF CANCAN Low IC DCANFig. 8 Tdelay ms Tbus ms ms ms Tcycle DCAN DCAN DCAN Tcycle Tbus Tdelay Fig. 8 A IC GNDDdata T bus Tdelay ms Tdata ms ms ms Tcycle Ddata Fig. 9 Tcycle Ddata CANDCAN Pm h h Ddata Pm Ddata Ddata hour Photo. 2 Photo. 2 Experimental setup to measure the response time to detect dummy failures. Ddata DCAN Ddata Tdata. Tcycle Tbus Tdelay Fig. 9 Fig. 8 Fig. 2 Measurement result of the detection time-lag in case of CAN bus-line failure.

10 NIIS-RR- Pm h h, Ddata. h ms. h LSI ms 5 BIU 5 1 Micro Processing Unit MPU MPU BIU MPU MPU LSI MPU FIFO 5 2 Fig. 9 Fig. 2 Measurement result of the detection time-lag in case of data bus line failure. MPU Fig.10 MPU

11 Fig.11 A B 6 Well-tried Safety BUS p Andy McFarlane Fieldbus Review, Sensor Review, Vol.No. pp.-. Vol., No.. Vol., No. pp. -. Richard Piggin, Ken Young, Richard McLaughlin: The current fieldbus standards situation. A European view, Assmbly Automation, Vol., No. pp.-. Richard Piggin A fieldbus for machine safety, IEE Review, Vol., No. pp. -. Reinert D., Schaefer M. NPO Fig. 10 Fig. 10 An redundant diverse architecture of micro processing unit instakked in a device connected to safety-related field bus.

12 NIIS-RR-. ISO, Road vehicles - Interchange of digital information - Controller area network CAN for high-speed communication. IEC, Railway applications-communication, signaling and processing systems-part Safety-related communication in open transmission systems. C Vol. No.pp. -. C, Vol. No. pp. -. NIIS-SRR-No. pp. -. ISO, Safety of machinery Safety-related parts of control systems. Fig. 11 Fig. 11 An example of factorial analysis for verification of proposed rebundant diverse MPU. in case that it is assumed as the top event that the device neglects an emergency stop command

13 CARAT D, Vol. No. pp. -.. IEC, Functional safety of electrical/ electronic/programmable electronic safetyrelated systems. DC- - pp. -.

Vol.53 No (July 2012) EV ITS 1,a) , EV 1 EV ITS EV ITS EV EV EV Development and Evaluation of ITS Information Commu

Vol.53 No (July 2012) EV ITS 1,a) , EV 1 EV ITS EV ITS EV EV EV Development and Evaluation of ITS Information Commu EVITS 1,a) 2 2 2011 10 21, 2012 4 2 EV 1 EV ITS EV ITS EV EV EV Development and Evaluation of ITS Information Communication System for Electric Vehicle Yuriko Hattori 1,a) Tomokazu Shimoda 2 Masayoshi