Panasonic, Tamagawa and Bosch Encoder Support Procedures and Alarms

This section presents additional detailed reference material for the supported Panasonic, Tamagawa and Bosch serial absolute and incremental encoders. 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 Startup Operation

For encoders with 17-bit counts per turn, the single turn data is valid as soon as the controller powers up and always provides accurate information on the motor's commutation reference angle. However, 10000 count serial incremental encoders operate in a different, more complicated fashion when they first power up.

When a 10000 count serial incremental encoder first starts, its single turn encoder counter is a random value with respect to the motor's commutation angle. Until the encoder is rotated and encounters the first internal zero index, the "preload" flags in the alarm and status words are asserted and the controller reads internal hall sensors values via the serial data stream. These hall readings are used by the controller to approximately set the motor's commutation reference angle. When the first zero index is encountered, the "preload" flags are set to 0 and, internally, the encoder encounter spontaneously changes value to be accurately aligned with the motor's commutation reference angle.

All of these special operations and changes in the encoder reading are automatically handled by the FPGA firmware and servo code and are not visible at the GPL level. However, this does require substantially more FPGA resources than the 17-bit encoders and the commutation angle will not be accurately set until the first internal zero index is encountered.

Encoder Low-Level Commands

This section describes the low-level commands that can be issued to the encoder. During normal operating modes, these commands should never have to be manually issued. The control system automatically issues these commands as necessary for accessing the multi-turn and single turn encoder count data and for retrieving the alarm codes.

The available commands specifically for the Panasonic and Bosch 17-Bit encoders are described in the following table:

DataID 14063 Command #	Type	Description - Panasonic / Bosch Commands
4	Synchronous	(Default) Get the single turn data and the alarm codes.
5	Synchronous	Get the single turn data, multi-turn data and the alarm codes.
10	Asynchronous	Get the single turn data, encoder ID and the alarm codes.
9	Asynchronous	Clear the battery and counter overflow errors.
11	Asynchronous	Clear the multi-turn data and latched errors.
14	Asynchronous	Clear all latched errors.

The available commands specifically for the Panasonic 10000 Count encoders are described in the following table:

DataID 14063 Command #	Type	Description - Panasonic / Bosch Commands
5	Synchronous	(Default) Get 24-bit position and single turn data.
10	Asynchronous	Get the single turn data, encoder ID.
11	Asynchronous	Clear all latched errors, get 24-bit position data.
14	Asynchronous	Clear all latched errors, get encoder ID.

The available commands specifically for the Tamagawa encoders are described in the following table:

DataID 14063 Command #	Type	Description - Tamagawa Commands
0	Asynchronous	Get the single turn data.
1	Asynchronous	Get the multi-turn data.
2	Asynchronous	Get the encoder ID.
3	Synchronous	(Default) Get the single turn data, multi-turn data, encoder ID and the alarm codes.
7	Asynchronous	Clear all latched errors.
12	Asynchronous	Clear the multi-turn data and latched errors.

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 #>

Command #5 is automatically executed by the system to obtain the multi-turn data during the homing operation. During normal execution, the controller is continuously issuing Command #4 (or Command #5) to read the single-turn position and the alarm status.

Commands #9 to #14 are used for clearing the various encoder alarm conditions or to facilitate initializing the encoder during the manufacturing process or during field service.

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 serial 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

These serial absolute and incremental encoders can generate a number of hardware alarm conditions. The specific error condition is indicated in "Encoder alarm" (DataID 12251). The interpretation of the alarm bits returned in this system parameter is a function of the type of encoder.

The following table contains a detailed description of each alarm for ALL 17-BIT encoders.

Bit	Name	Cause	Description
0	Over-speed (latched until manually cleared)	This alarm occurs when the encoder power is OFF and its shaft speed and/or acceleration exceed specified limits. This alarm is returned the next time the encoder power is enabled. When this alarm occurs it’s likely that the multi-turn encoder data is no longer correct.	System Action: If the motor is turned ON and calibrated, it can continue to be used so long as the multi-turn data is not accessed. If homing is initiated, the operation will probably fail until this fault condition is manually cleared. User Action: This alarm condition must be explicitly cleared using one of the commands presented in the next section. Also, the "Calibration home offset" (DataID 16120) will have to be recomputed. The zero position of the encoder must be reset after this error occurs since the multiple turn counter will probably be invalid.
1	Reduced encoder resolution	When the controller is first restarted, this alarm is generated if the encoder is turning faster than 100 RPM. When this occurs, the accuracy of the single turn data drops to only 5 bits of resolution. When the encoder shaft speed drops below 100 RPM the single turn data is restored to 17 bits (full resolution) and this flag is automatically cleared.	System Action: After boot up, before using the encoder data, the servo checks to ensure that this flag is cleared. If it remains set for consecutive reads, an encoder error is issued to prevent the motor power from being enabled. User Action: None required.
2	Counter error	At any time when the controller is on: Type 1 – If the encoder shaft is turning faster than 100 RPM, special error detection is conducted every 45 degrees. If the single turn data is shifted by more than +/- 22.5 degrees then this alarm bit is set. When the shift drops below the limit, this bit is automatically cleared. Type 2 – If the encoder shaft is turning less than 100 RPM, the standard error detection is conducted all the time. If the single turn data is shifted by more than +/- 0.7 degrees then this error flag is set and latched until cleared.	System Action: For either a type 1 or type 2 encoder count error, the servo will issue a standard error message, which is equivalent of an “index error”, and motor high power is disabled. User Action: For a type 2 error, the alarm must be explicitly cleared using one of the commands presented in the next section. Until the error is reset, the motor power is prevented from being enabled.
3	Multi-turn counter overflow (latched until manually cleared)	If the multi-turn data overflows, then this bit is set. If the overflow occurs when the encoder power is turned off, this alarm will be returned after the encoder is powered up. The multi-turn data will keep accumulating regardless of this alarm. The multi-turn counter counts between 0 and 65535.	Action: A multi-turn data overflow (or underflow) has no effect on the servo run-time operation. However, during homing, if this fault is detected then the homing operation will fail. User Action: This alarm must be explicitly reset using one of the commands presented in the next section. NOTE: During normal encoder setup, the multi-turn data is interpreted by the servo as a signed value and its actual count range is between -32768 and 32767. So, this error should never occur for a typical robot.
4		(reserved)
5	Multiple turn read error (latched until manually cleared)	If the encoder multi-turn data cannot be properly accessed when the controller is restarted, this bit is set.	System Action: There is no effect on turning on motor power. However, the motor homing operation will fail. User Action: This alarm must be explicitly reset using one of the commands presented in the next section. After the alarm is cleared, power cycle the encoder to force the multi-turn data to be reloaded.
6	System down (latched until manually cleared)	For Panasonic, if the encoder’s built-in capacitor voltage drops below 2.5 +/- 0.2V then this flag is set and the multi-turn data is most likely corrupted. For Tamagawa, this error is signaled if the external battery voltage drops below 2.5V, even if the internal capacitor still has a sufficient charge. The multi-turn data will be lost once the capacitor's hold time has elapsed. For either encoder, the capacitor's hold time is roughly 1 hour after the external battery is disconnected. The hold time will degrade to 15 minutes after 10 years of operation at 40 degrees C.	System Action: When this alarm occurs, the servo issues a severe error and motor power is disabled immediately. Motor power is prevented from being turned on. User Action: Check the external battery connected to the Controller's MCIM board, it may need to be replaced or be re-seated. Also ensure that all battery connectors are of the high compression type with gold plating. Low compression connectors or tin plated connectors can result in a momentary drop of battery power especially for connectors that are located within the moving parts of a robot. After the battery problem is corrected then power cycle the encoder and clear this fault explicitly using the commands presented in the next section. Once the problem is corrected, then the encoder multi-turn counter may have to be reset and the "Calibration home offset" (DataID 16120) may have to be recomputed.
7	Battery alarm (Panasonic -latched until manually cleared. Tamagawa - automatically cleared)	If the external battery voltage drops below 3.1 +/- 0.1V then this alarm is set. This occurs regardless of the encoder power state. Note that when the battery is disconnected this alarm will be asserted.	System Action: When a battery low warning is issued, the multi-turn data is still valid as long as the encoder’s internal capacitor maintains a proper voltage level. See alarm bit #6. User Action: Check the external battery connected to the Controller's MCIM board and replace if necessary, Also ensure that all battery connectors are of the high compression type with gold plating. Low compression connectors or tin plated connectors can result in a momentary drop of battery power especially for connectors that are located within the moving parts of a robot. Clear this fault using one of the commands presented in the next section (if required).
8	Communication time out	When the controller is first started, this error will be generated if the controller is not able to communicate with the encoder.	System Action: After boot up, the servo communicates with the encoder to extract information stored in the encoder. If the servo is unable to successfully communicate, this error is signaled. User Action: This error indicates a hardware problem. Either the encoder is not working, the encoder is not receiving any power or the encoder communication line is broken.

The following table contains a detailed description of each alarm for 10000 COUNT INCREMENTAL encoders.

Bit	Name	Cause	Description
0-2	Hall sensor value		These bits do NOT indicate an alarm or error condition. They return the internal hall sensor value that is used to commutate the motor until the first zero index is encountered.
3	Wrong count per rev	The wrong number of counts per revolution have been detected when an internal index signal is encountered. If the error is greater than +/- 0.108 degrees, this bit will be set.	System Action: The servo generates a standard error message, which is equivalent to an index error, and motor power is disabled. User Action: The user must explicitly clear the alarm condition (see above). After resetting the alarm, the controller may need to be restarted. If the problem persists and bit 8 of the "Encoder alarm" (DataID 12251) is low, this may indicate a encoder hardware problem.
4	Hall phase count error	The number of encoder counts between hall sensor phases is less than 255.	System Action: The servo will issue a severe error message. The error is equivalent to a hall sensor failure and motor power is disabled. User Action: The user must explicitly clear the alarm condition (see above). After resetting the alarm, the controller may need to be restarted. If the problem persists and bit 8 of the "Encoder alarm" (DataID 12251) is low, this may indicate a encoder hardware problem.
5	First index not found	The internal zero index signal was not detected even though the "pre-load" status flag has been cleared by the encoder.	System Action: The servo generates a standard error message, which is equivalent to an index error, and motor power is disabled. User Action: The user must explicitly clear the alarm condition (see above). After resetting the alarm, the controller may need to be restarted. If the problem persists and bit 8 of the "Encoder alarm" (DataID 12251) is low, this may indicate a encoder hardware problem.
6	Hall phase output error	This alarm bit is set if all of the bits of the internal hall sensor output are "1"'s or "0"'s.	System Action: The servo will issue a severe error message. The error is equivalent to a hall sensor failure and motor power is disabled. User Action: The user must explicitly clear the alarm condition (see above). After resetting the alarm, the controller may need to be restarted. If the problem persists and bit 8 of the "Encoder alarm" (DataID 12251) is low, this may indicate a encoder hardware problem.
7	Pre-load status	This bit is set to 1 when the encoder is first powered on. It will be reset to 0 when the first internal zero index is detected.	This is a status bit and will be normally reset after the first revolution of the motor.
8	Communication time out	This is the same signal as documented above for the absolute encoders.	This is the same signal as documented above for the absolute encoders.

Clearing Alarm Conditions

Although alarm conditions are not very common, when they occur, some alarm conditions stay latched until they are manually cleared. To clear a latched alarm, 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 clear most encoder latched errors, execute the following commands where the <robot> and <axis> numbers count from 1:

PC 14500,<robot> = <axis>
PC 14063 = 14                         ' For Panasonic encoders
            or
PC 14063 = 7                           ' For Tamagawa encoders
            or
PC 14065 = 1                            ' For all serial encoders

To reset the multi-turn counter and reset the latched errors, execute the following commands:

PC 14500,<robot> = <axis>
PC 14063 = 11                         ' For Panasonic encoders
           or
PC 14063 = 12                         ' For Tamagawa encoders
           or
PC 14065 = 3                           ' For all serial encoders

If a battery alarm 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.

External Encoder Battery Replacement

When the Guidance Controller is not powered on, the absolute encoder retains the multi-turn counter using power from either an internal or an external battery. The external battery is connected to the controller's MCIM and supplies power to all connected absolute encoders. The internal battery in each encoder has power for approximately 1 hour when fully charged and is designed to supply power while the external battery is being changed.

To change the external battery, perform the following steps:

Log the current multi-turn data for all axes.

Power down the encoders and replace the battery. As stated above, you have approximately 1 hour to restore the external battery power.

Power the encoders back up and manually clear the encoder alarm conditions for all axes.

Read the multi-turn data back to make sure they are the same as before. If not, then it’s likely that the multi-turn data is corrupted and the homing offset must be set again