Yaskawa Sigma II/III Encoder Support Procedures and Alarms

This section presents additional reference material for the Yaskawa Sigma II/III Serial Absolute Encoder. This information includes an explanation of special maintenance communication commands and a description of the alarm conditions that can be generated by the encoder hardware. This information is typically not necessary for setting up the encoder or for normal operations.

Encoder Asynchronous Commands

The following table presents the Yaskawa Sigma II/III asynchronous commands supported by the Guidance Controller software. These functions are referred to as P0 commands in the Yaskawa Sigma II/III documentation.

These commands should never be issued during normal encoder operation. Also, special care must be taken as some of these commands may change the multi-turn absolute counter data and thus invalidate the calibration of the motor and the mechanism.

DataID 14063 Command #	Description - Yaskawa Commands
0	No operation (NOP)
1	Resets the multi-turn counter to 0 and clears encoder alarms. This command is usually executed after the battery is changed to clear the battery alarm. See the Clear Encoder Alarms section below for more details.
2	Sets the multi-turn limits and clears the multi-turn counter in the encoder to 0. The default encoder multi-turn limit is set to 65535. Normally there is no need to change this value.
3	Echo's a test pattern from the encoder. This command is used during encoder boot-up to check the encoder communication.
4	Sets the serial communication to synchronous mode.
5	Sets the serial communication to asynchronous mode.

To execute these commands, you must access the console interface by either connecting a terminal to the first serial port or launching the Remote Console from the web Control Panels. To perform any of these commands, issue the following instructions using the console port, where the <robot> and <axis> numbers count from 1:

PC 14500,<robot> = <axis>
PC 14063 = <command #>

Commands #0 to #3 are encoder asynchronous (P0) commands. In order to execute these functions, the encoder communications must first be put into asynchronous mode by issuing command #5. After the final asynchronous command is executed, command #4 must be issued to set the encoder communications back to synchronous mode for normal operation. When robot high power is enabled, asynchronous commands are not permitted.

In addition, the system supports the following limited set of Generic Commands that are redundant with the DataID 14063 commands, but will work for all absolute encoders.

DataID 14065 Command #	Type	Description - Generic Commands
1	Asynchronous	Clear all latched errors.
2	Asynchronous	Clear battery and counter overflow errors.
3	Asynchronous	Clear the multi-turn data and latched errors.

Encoder Alarm Conditions - Response and Recovery

The Yaskawa Sigma II/III Serial Absolute Encoder can generate a number of hardware alarms conditions. These alarms are specific to this absolute encoder. The alarm condition is captured as bit flags in the "Encoder alarm" (DataID 12251).

A detailed description of each alarm for the Yaskawa Sigma II/III encoder is presented in the following table.

Bit	Name	Cause	Description
0	Backup Alarm	Backup power is down, internal data has been lost including multi-turn count data. This alarm indicates that both the power supply and the battery power have failed. This alarm is latched until a RESET command is executed.	System Action: When this alarm occurs, the servo issues a severe error and disables the motor power immediately. Motor power is prevented from being enabled until the user performs the corrective action. User Action: Check the external battery connected to the Controller's MCIM board and replace if necessary. After the battery problem is corrected, follow the steps outlined in the Resetting the Multi-Turn Counter section below to clear this fault. If you are unable to clear the alarm, the motor may need to be replaced. (In this case, it might still be possible to use the motor as a single turn device by disabling the alarm check via DataID 10251.)
1	Runtime Error	Error in encoder memory. This alarm is latched until a RESET command is executed by the user.	System Action: When this alarm occurs, the servo issues a severe error and disables the motor power immediately. Motor power is prevented from being enabled until the user performs the corrective action. User Action: Follow the steps outlined in the Resetting the Multi-Turn Counter section below to clear this fault. If you are unable to clear the alarm, the motor may need to be replaced.
2	Battery Warning	The battery voltage has dropped below 2.7V or the battery has been disconnected.	System Action: When the battery warning is issued, the multi-turn counter data is still valid and the encoder will still operate normally. The motor power will not be effected, but if a homing command is executed, the servo will issue a warning and the homing operation will fail. User Action: Check the external battery connected to the Controller's MCIM board and replace if necessary. Follow the steps in the Encoder Battery Replacement section below to change the battery.
3	Absolute Error	Operational error in the encoder, possible error in the position data. Indicates malfunctioning absolute encoder.	System Action: When this alarm occurs, the servo issues a standard error and the motor power is disabled. User Action: Check all of the encoder cable connections. Power cycle the Controller. If the alarm does not clear, the motor may need to be replaced.
4	Overspeed	The speed of the motor is too high when the encoder power is being enabled.	System Action: When this alarm occurs, the servo issues a standard error. The motor power is unaffected but a subsequent homing operation will fail. User Action: Power cycle the Controller, make sure the motor is stopped when the power is turned on.
5	Overheat	The encoder temperature is too high (> 100 Deg C). Continued operation of the motor at this temperature may damage the motor and encoder.	System Action: When this alarm occurs, the servo issues a severe error and disables the motor power immediately. User Action: Change the motor operating conditions or parameters to reduce the heat generation.
6	Reset Complete	A RESET command is completed. The multi-turn counter is reset to 0 and the alarm conditions are cleared.	System Action: When this alarm occurs, the servo issues a standard error. The motor power is not affected but a subsequent homing operation will fail. User Action: Power cycle the Controller to clear this alarm bit. NOTE: After the multi-turn counter is reset, the absolute position of the motor is probably changed the the axis homing data is most likely invalid.

Resetting the Multi-Turn Counter

There are a number of situations where it may be necessary to reset the Yaskawa Sigma II/III encoder:

The motor is being setup for the first time
An encoder generates a "Backup Alarm" and/or a "Runtime Error"
An encoder losses power due to a cable disconnection at anytime or a battery disconnection when the controller power is off.

In these circumstances, the multi-turn data may become invalid and it may be necessary to clear the alarm and reset the multi-turn data before continuing normal operation.

The Yaskawa Sigma II/III encoder provides a RESET command to clear the alarm and reset the multi-turn counter data at the same time. To execute this command, you must have access to the console interface by either connecting a terminal to the first serial port or launching the Remote Console from the Web Control Panels.

NOTE: After a RESET command is executed, an encoder's multi-turn counter will be set to 0. This normally changes the absolute position indicated by the encoder and invalidates the homing setup information. To correct this calibration error, the homing data must be re-initialized.

To execute the RESET command, enter the following commands in the console, where the <robot> and <axis> numbers count from 1:

PC 14500,<robot> = <axis>
PC 14063 = 5
PC 14063 = 1

wait for about 5 seconds, then enter:

PC 14063 = 4

After completing the steps above, enter the following command in the console:

PD 12251

The console will display the value of the "Encoder Alarm" (DataID 12251). The exact display will be a function of the system configuration and the axis being reset. The following example is for a 4 axes system where the first axis was reset.

12251, 1, 1, 0, "Encoder alarm" = 64, 0, 0, 0

The first encoder alarm value has bit 6 set ("64"), which indicates that the RESET command has been completed (See Encoder Alarm table above).

If a battery warning is signaled due to the external battery having a low charge, keep in mind that the alarm will probably be set on all encoders and each encoder's alarm condition must be individually reset.

Finally, restart the Controller to have the RESET operation take effect.

External Encoder Battery Replacement

The Yaskawa Sigma II/III encoder uses an external battery to retain the multi-turn data when the Guidance Controller is powered off. The external battery is connected to the controller's MCIM and supplies power to all connected absolute encoders. The controller generates a battery alarm when the controller is restarted or a homing operation is initiated if the voltage of the battery for the encoder drops below 2.7V.

NOTE: The parameter "Ignore encoder battery alarm during homing" (DataID 10251) can be used to prevent the controller from reporting a battery alarm during homing. However, the alarm will still be reported when the controller is restarted.

The following procedure can be used to replace the battery without losing the multi-turn counter information.

Leave the controller powered on in order to supply power to the encoder.
With the controller powered on, carefully replace the external battery connected to the MCIM.
After the battery is replaced, turn off the power to the controller to clear any alarm conditions asserted by the encoder.
Turn on the power to the controller and confirm that all of the battery alarms are now cleared.