YRC1000 Safety IO Counter Operation:

Background:

Yaskawa has had some customers inquire about wanting to monitor the frequency of operation of their safety inputs on their YRC1000 controller. This is a semi-infrequent request but if implemented it can be helpful to monitor the operation of a cell and potentially steer toward a potential issue be it operator, environmental, or hardware. Via a CIO ladder change, logic can be established that will count the number of operations of GSIN and FSBIN inputs. The counting of these signals will provide a reliable indication of the number of times:

• An operator enters a light curtain or area scanner
• The number of times an operator door is opened into a system

These counters can also be helpful for:

• Determining if an environmental condition is tripping the light curtains or area scanner
• Determining if weld spatter or debris from parts is triggering tripping the light curtain or scanner

Yaskawa’s implementation of this counting feature will provide an active monitor & count of the safety input state changes (raising edge). When 10-million cycles of any input are reached, a message will appear stating “SAFETY DEVICE ACTUATION > 10Mil!” and that message will remain in-place until a reset operation is performed to clear the counters back to zero.

Why this matters:

• Safety devices are often connected to the robot controller via Safety Relays which are mechanically operated devices with a finite number of mechanical operations. Most Safety relays have a published expected life span of 1million to 10million expected operations.
• When in production, those cycles accumulate quickly especially when an operator may break a safety light curtain or scanner multiple times while loading various parts into a fixture.
• Safety devices are interfaced with safety relays in a fashion that draws very little current across the contacts of the safety relays. This low-current (5-20mA) across the contacts of a safety relay (often rated at 5-10A) is so little that the contacts of the relay often “film over”. This “filming” is an oxidation which leading to contacts that while they may physically close, doesn’t pass the electrical signal. To the robot controller or PLC, this results in a mismatched safety signal which will fault the robot or PLC

General Safety Relay Implementation Considerations:

• If possible, attempt to eliminate the use of electro-mechanical relays where possible. Instead, solid-state inputs like those found on Safety-PLCs are desirable but admittedly are not always a viable option.
• Yaskawa often uses electro-mechanical safety relays for interfacing with the various robot controllers because the light curtains or area scanners often have “test pulses” on their outputs which if connected to the YRC directly, it can cause false alarms on the robot when the robot detects a test-pulse. Detection of a “test” pulse will likely result in a “Safety Signal Mismatch” alarm or result in an alarm indicating that safety device was interrupted when it wasn’t.

Requirements for Implementation:

The following requirements and considerations should be taken into account when considering implementation of this feature:

1. This counting logic will make use of the following system registers & PSEUDO input. Please confirm that they are not in use on your system. They typically are not used by Yaskawa:
   • M-Registers: 120-140
   • PSEUDO Input# 87203
2. The required ladder modifications are best performed by the Yaskawa Customer Support. They have a software tool that will implement the needed Concurrent IO modification quickly and without error. To perform this implementation, they will require the following files from your YRC1000 robot:
   • CIOPRG.LST
   • IOMNAME.DAT
   • PSEUDOIN.DAT

Send these files to Yasakwa customer support at: techsupport@motoman.com , include the warranty ID from the system where this feature is desired and provide a link to this article in the text of the email.

1. Once the files are returned from Yaskawa Customer Support team, they can be loaded into the controller with a basic management level password.
2. Once loaded, the counting process will occur anytime the PSEUDO input #87203 is ON. It can remain on for long-term monitoring or can be used for a short duration of time to monitor a signal for several days. If you wish to reset the counters, see the end of this article for details.

Monitoring the Safety Input Counters:

Below is an example of a system that has been counting FSBIN1-4 values for an extended period of time. Since the YRC1000 M-register are only able to count to 65535, a roll-over register is used to count the number of roll-overs. To calculate the actual count of a register use the following formula:

Actual count = (M13x * 65535) + M12x (where “x” is the index of the count be calculated

Counts from above:

• FSBIN#1: (16 * 65535) + 53540 = 1,102,100
• FSBIN#2: (134 * 65535) + 4953 = 8,786,643
• FSBIN#3: (4 * 65535) + 13492 = 275,140
• FSBIN#4: (2 * 65535) + 6753 = 137,823
• FSBIN#5-8: (0 * 65535) + 0 = 0
• GSIN#1-2: (0 * 65535) + 0 = 0

Message when reaching limit:

When any of the M13x registers exceed a value of 152 (152 * 65535 = 9,991,320) a message appears at the bottom of the screen indicating that you’ve essentially reached 10million cycles of the input and that you should consider maintenance or replacement of the device connected to the specific safety input. This message will not interfere with production or operation of the system but will remain on the screen until it is reset. See next section on how to reset it.

Resetting Safety Counters:

The safety counters can be reset at any time, not just when the message is active. The reset operation will reset ALL of the counters to a value of zero so be aware of the fact you can’t individually reset just one particular counter.

To reset the counters to a value of zero, the PSEUDO input #87203 needs to be toggled off and back on within 1.5seconds. This semi-rapid toggling will reset all the counters to a value of zero. When the registers are reset to zero, a message will briefly display on the bottom of the screen stating “SAFTEY DEVICE/INPUT CNT RESET!”.