Rexroth Motors

Overview

Rexroth MSK Series motors use singe-turn and multi-turn serial absolute encoders of both Stegmann Hiperface and Heidenhain Endat brands. Refer to this section and Stegmann section, and the Heidenhain secction for more information on testing motors with the Stegmann Hiperface encoders. These encoders include memory, and the MSK motors utilize this memory area for motor parameters including alignment information. This section will focus on the memory support for these motors.

The Rexroth MSM series motors use incremental and Tamagawa MFE0017 serial encoders. The incremental encoder is not supported. Please see the section on Tamagawa encoders for more detail.

 

Types Supported

The following lists show the Rexroth motors with their corresponding encoders that are currently supported by the TI-5000JX, along with test cable possibilities. Please check the current PDF catalog file and price list files for a complete listing of all cables supporting Rexroth motors.

This list includes Rexroth MSK series motors using Heidenhain Endat and Stegmann Hiperface encoders.

 

This list includes Rexroth MSM series motors using incremental and Tamagawa serial encoders.

 

The MSM series also includes an incremental encoder that is currently not supported. It may be called MFE2500. Rexroth calls it an incremental, but it is a serial encoder. It uses 10,000 counts/rev for the position count. But it does not count revolutions, so it does not need battery backup. More information will be included in the future when it is supported.

Note: The first count is the number of counts/rev for the incremental signals, the second is the number of counts/rev for the absolute serial position count, and the last count is the number of revolutions that can be counted (for multi-turn encoders only).

 

Identification

MSK Series-

The part number breakdown for these motors is as follows:

 

 

MSM Series-

 

Connection

Connection requires using the correct cable as shown in the chart in the Type Supported section. Also the Athena ‘Feedback Selection’ frame has a cable dropdown menu from which you can select the cable that you need. After making the cable selection, that selection will appear on the Data Display report which is helpful in documenting the cable used.

The MSK motor feedback connector is compatible with theTI-5093 cable for either the Stegmann or Heidenhain encoders. The TI-5104 Adapter Module should be use with this cable in order to provide 8 VDC supply voltage to the encoder. When the Heidenhain encoders are used, and the MSK encoder wiring includes a 5VDC voltage regulator that reduces the 8 VDC to 5VDC for the Heidenhain encoders. The TI-5094 generic cable connects directly to the 9 pin connector on the Hiperface encoder. It should also be used with the TI-5104 Adapter Module. The TI-5079 generic cable connects directly to the 12 pin connector on the Heidenhain Endat encoder. The TI-5104 Adapter Module should not be used with this cable. The Endat encoders are 5V encoders, and the 8VDC from the module may damage them. The MSM motor feedback connector is compatible with the TI-5080 cable when the MFE0017 serial absolute encoder is used.

 

Data Display

Commutation

The electrical angle is best for checking and setting commutation. For a particular lockup polarity, the rotor will lock up in as many different positions as there are pole pairs but the electrical angle indications will be the same at each lockup position. The mechanical angle will be different at each lockup position (except for 2 pole motors where there is only one lockup position), so mechanical angle is not as convenient to use for feedback alignment. See section 3.2 for a more detailed description of commutation alignment procedures.

The number of poles must be entered correctly for the electrical angle to be displayed correctly. The electrical angle and mechanical angle are derived from the position count. The position count is absolute immediately on power up for Stegmann Hiperface, Heidenhain Endat, and Tamagawa serial absolute encoders.

The two procedures require applying power to only two armature leads at a time. It is easy to go from +U –V to +U –W just by moving the minus lead from V to W. This should cause the motor to jog 60 electrical degrees in the forward direction (CW looking at the shaft for MSK). Failure to move the correct number of degrees or in the correct direction would be an indication of a significant problem. Setting these angles within ±3 electrical degrees is normally quite sufficient.

The table below shows 2 different lockups that can be used to check or set commutation on Rexroth MSK motors with Hiperface or Endat serial encoders.

 

Note: This is an example alignment based on encoder data. These motors do not have a standard alignment. The angles you see will be different.

 

Unlike most feedback alignment discussed in this manual, Rexroth MSK motors using Hiperface and Endat
encoders do not have a common lockup angle, and in general, they will all lock up at different angles. These motors store a commutation offset in the encoder memory. By using the commutation offset, the encoders do not have to be set to a common alignment. In order to correctly check or set the alignment, you have to run the Memory Test on the encoder, and write down the +U –V and +U –W lockup angles provided by the memory test.

Again, for the MSM motors, it is easy to go from +U –V to +U –W just by moving the minus lead from V to W. This should cause the motor to jog 60 electrical degrees in the forward direction (CW looking at the shaft for MSM). Failure to move the correct number of degrees or in the correct direction would be an indication of a significant problem. Setting these angles within ±3 electrical degrees is normally quite sufficient.

The table below shows 2 different lockups that can be used to check or set commutation on Rexroth MSM motors with Tamagawa MFE0017 serial encoders.

Note: The MSM motors apparently do not store alignment information in the encoder data. These motors apparently have a standard alignment. The above alignment is the only alignment that has been reported so far for these motors.

 

As with most feedback alignment discussed in this manual, Rexroth MSM motors using Tamagawa encoders do appear to have a common lockup angle. The alignment shown above is the only alignment that we are aware of for these motors. You still need to do a memory test to verify that the memory data is in the encoder and is readable.

 

Count

See the section for the appropriate encoder.

 

Encoder Status

See the section for the appropriate encoder.

 

Memory Status

When Stegmann Hiperface encoders are selected, the Data Display provides a function for reading the memory status. There is no such function for the Heidenhain Endat encoders.

The Read Memory Status button on the Data Display allows the user to check whether memory is currently in use for a particular encoder. Clicking the button when connected to an SKS36 encoder on an Rexroth MSK motor would produce the following display:

This tells us that there are 8 memory fields of 128 bytes each defined in this encoder. All 8 fields are write enabled (WE). The access code is set to 0 (could be 0, 1, 2, or 3). The code enable bit (CE) is not set for the 8 defined fields, so the access code does not have to be used. The total bytes number of memory bytes used is 1,024. The total bytes unused is 0, and this means that all of the available memory is in use. No more data fields could be defined for this memory because it is used up.

This data formatting is done by the motor manufacturer and is of little concern to the TI-5000JX user. However, it is useful to look at it to verify that the memory looks normal. For instance if you see that no fields have been defined for an encoder on a Rexroth MSK motor, it is very likely that the encoder has been replaced and the correct data has not been programmed into the memory. This would be very important to know because the motor would not run correctly on the Rexroth drive. It is also useful to check on unfamiliar motors to determine whether the motor manufacturer is using the memory.

This Memory Status data is automatically included on the Data Display report when a Stegmann Hiperface encoder has been selected.

 

Count Test

See the section for the appropriate encoder.

 

Memory Test

Encoder memory is used on Rexroth MSK and MSM PM brushless motors (this list may not be all inclusive). As explained previously, the Read Memory Status button on the Data Display can be used to determine whether the memory is in use when Stegmann Hiperface encoders are used.

When the memory is used, it will normally be programmed with the motor model number and sometimes motor parameters. The drive can read this memory data on power up and determine what kind of a motor is connected to it. Some manufacturers, such as Rexroth and Indramat, are now programming a commutation offset value into the memory. This offset tells the drive the difference in the present feedback alignment from the ideal feedback alignment so that the drive can adjust its timing to compensate for an imperfectly aligned feedback device. This relieves the manufacturer of performing a precise alignment during manufacturing. They simply program in the offset for the drive to read. This means that each motor may be aligned somewhat differently, but the repair shop must still align the feedback the way the drive is expecting it to be. The TI-5000JX memory support will display the proper alignment angles based on this memory data so that the repair technician can properly align the feedback.

Because the way in which the memory is used differs with the various motor manufacturers, software support must be developed for each brand (and sometimes models) of motors. Therefore TI-5000JX memory support must be purchased for each motor type in addition to the basic Stegmann encoder support.

Note: If a Hiperface encoder is replaced on an Rexroth motor, the motor data must be programmed into the replacement encoder in order for the drive to run the motor. Contact Mitchell Electronics, Inc. for information on software support for programming replacement encoders.

 

Rexroth MSK Memory Test

Rexroth MSK motors use the Hiperface encoder memory to store motor parameters. This data is programmed at the factory and cannot be changed by the drive. This data is read by the drive system on power-up prior to moving the motor. If the drive system cannot read the memory or if it gets incorrect data from it, the motor will not run. It is therefore very important to verify that the memory can be read and appears to be correct. The memory also contains information that allows checking the commutation alignment.

In verifying correct memory data and memory operation, we are looking at two things:

1. Is the data correct and not corrupted?
2. Is it the correct data for this motor?

The first item is done automatically. The data in the encoder is encoded with the ability to check data integrity. The TI-5000JX automatically checks some of this data as it reads and displays the various motor parameters. An explanation of possible errors is provided at the end of this section.

The second item amounts to making sure that the encoder that is on the motor is the correct one. Sometimes in trouble-shooting, encoders get swapped in an attempt to isolate a problem, and the encoder on the motor you have could be the wrong one entirely. In general the data from the encoder should match the data from the motor nameplate. In this regard, we are looking for gross errors. Minor differences in the encoder data and nameplate data are normal.

The display shown below is a memory test from an SKS36 encoder. The motor part number and motor parameters are fairly self explanatory. These numbers should match reasonably well with the nameplate data. At the end of the right column is some information that is useful to the repairman. The number of pole pairs is 4, which indicates a, 8 pole motor. MSK motors are know to use 6, 8 and 12 poles. There may be other numbers of poles, but those have been seen so far.

The TI-5000JX uses the commutation offset to calculate what the +U –V and +U –W lockup angles should be in electrical degrees for proper feedback alignment, and these angles are reported in the Derived Data
frame. 

Comparing the above nameplate data to the encoder data below, we see that the data agrees quite well. 

 

 

Each data item has a checksum associated with it for checking data integrity. If the checksum is found to be incorrect, ‘DATA ERROR’ is written into the field in the report in place of the data. At this time, the TI-5000JX cannot check all the data, but it will report any problems with the portion of the data that it can check.

If data errors occur, it could be for any of the following reasons:

1. Faulty encoder.
2. Faulty or no encoder data.
3. Faulty feedback cable from the feedback connector to the encoder in the motor.
4. Failure to use the TI-5104 Indramat Adapter Module.
5. Incorrect or faulty TI-5000JX test cable.
6. Faulty TI-5000JX.

Experience so far indicates that it is somewhat rare for the encoder memory to actually have a problem. If you encounter an encoder data error, check the list above to verify that you are doing everything correctly. Especially if you are unfamiliar with testing Rexroth motors, you might check with Mitchell Electronics, Inc. if you have an encoder (or several encoders) that do not read the data correctly.

The TI-5000JX software will attempt to pop up a message to help identify possible data problems or incorrect tester selections.

The data from this screen may be saved or printed as a report either in the usual manner with the Save Report to File or Print Report buttons.

The Save Encoder Data File button may be used to save a copy of the data to a disk file as Intel hexcode. You may wish to do this to send to Mitchell Electronics, Inc. in the event that there might be a question about the data. You may also wish to have a copy in case you would need to program it into a replacement encoder in the future.

 

Rexroth MSM Memory Test

Rexroth MSM motors use the Tamagawa MFE0017 encoder memory to store motor parameters. This data is programmed at the factory and cannot be changed by the drive. This data is read by the drive system on power-up prior to moving the motor. If the drive system cannot read the memory or if it gets incorrect data from it, the motor will not run. It is therefore very important to verify that the memory can be read and appears to be correct. The memory also contains information that allows checking the commutation alignment.

In verifying correct memory data and memory operation, we are looking at two things:

1. Is the data correct and not corrupted?
2. Is it the correct data for this motor?

The first item is done automatically. The data in the encoder is encoded with the ability to check data integrity. The TI-5000JX automatically tests 2 checksums, and this should determine whether or not the data I good.

The second item amounts to making sure that the encoder that is on the motor is the correct one. This is more complicated with the MSM motors that normal because of the process required to get the model number. It has only been tested with the MSM020B MSM030B, and MSM030C models, and other models will like not display correctly. As more models are checked, the software will be updated to accommodate them.

The display shown below is a memory test from an MFE0017 encoder. There is actually not very much data used for these motors. But, the checksums should provide a very good indication as to whether the data is good or not.

As stated previously, the MSM motors use a standard alignment, and the lockup is not derived from the data. But for convenience, the +U –V and +U –W lockup angles are displayed in the Derived Data frame. These angles should be in electrical degrees for proper feedback alignment.

 

 

There are two blocks of data in the encoder memory, and each block has a checksum associated with it which allows the ability to check data integrity. The TI-5000JX does this automatically as it reads and displays the various motor parameters. Any incorrect data in one of the data blocks will result in an incorrect checksum calculated for that block. This will be reported with the text “Error” followed by the calculated checksum and then the data from the checksum field. The word “Error” is all you need to see to know that the information is incorrect. If the data is correct, the checksum field will show the text “OK” (as we see in our example). You should assume that if a checksum error occurs, the Rexroth drive will not run the motor.

 

If data errors occur, it could be for any of the following reasons:

1. Faulty encoder.
2. Faulty or no encoder data.
3. Faulty feedback cable from the feedback connector to the encoder in the motor.
4. Incorrect or faulty TI-5000JX test cable.
5. Faulty TI-5000JX.

Experience so far indicates that it is somewhat rare for the encoder memory to actually have a problem. If you encounter an encoder data error, check the list above to verify that you are doing everything correctly. Especially if you are unfamiliar with testing Rexroth motors, you might check with Mitchell Electronics, Inc. if you have an encoder (or several encoders) that do not read the data correctly.

The TI-5000JX software will attempt to pop up a message to help identify possible data problems or
incorrect tester selections.

The data from this screen may be saved or printed as a report either in the usual manner with the Save Report to File or Print Report buttons.

The Save Encoder Data File button may be used to save a copy of the data to a disk file as Intel hexcode. You may wish to do this to send to Mitchell Electronics, Inc. in the event that there might be a question about the data. You may also wish to have a copy in case you would need to program it into a replacement encoder in the future.