Indramat Digital Motors, Serial Encoders and Resolvers

Overview

This section covers the so called digital Indramat motors and feedback. The part numbers begin with MDD, MHD, MKD, and MKE. These motors use complicated serial encoder and resolver feedback systems which include memory data to identify the motor to the drive.

The older motors, whose part numbers begin with MAC, are much simpler. They use Hall effect feedback for commutation, and use incremental encoders for position feedback. They also include a tachometer for speed feedback. Refer to previous sections on Generic Incremental Encoders whenever MAC motors are involved. Accessories available for the MAC motors include the TI-5042 cable and the TI-5105 Adapter Module which allow connection to the encoder, Halls, and tach at the same time.

This section covers the serial digital feedback devices, and does not cover MAC motors.

 

Types Supported

The following list shows the Indramat serial encoders that are currently supported by the TI-5000JX:

 

Identification

The Indramat encoders are manufactured by both Heidenhain and Stegmann. The encoders will have an Indramat part number that starts with DSF or HSF followed by a number and SN for single-turn or MN for multi-turn. At the end of this number, -H will mean Heidenhain and –S will mean Stegmann. The Stegmann encoders seem to be very common on Indramat spindle motors. On the permanent magnet brushless motors, they do not seem to be used on the MHD series motors, and they seem to be used considerably less than Heidenhain encoders on the MDD motors. This is also indicated by the Indramat motor part number. Here are some example part numbers:

• MDD 112D-N-020-N2L-130PB0 Heidenhain single-turn
• MDD 065A-N-040-N2M-095PB0 Heidenhain multi-turn
• MDD 071A-N-030-N2S-095PB0 Stegmann single-turn
• MDD 071C-N-060-N2T-095GA2 Stegmann multi-turn

The Heidenhain encoders include an ECN, RCN, EQN or RQN part number. The older MDD motors can have the ECN/RCN212, EQN/RQN224, ECN/RCN413 and EQN/RQN425 encoders (the newer motors will have the 400 series encoders). According to the manual, the MDD motors can also use resolver feedback, but it does not appear to be very common.

The Stegmann encoders will include a Stegmann SCS70 part number. These encoders will appear on the MDD servo motors and the 2AD spindle motors. There is much less memory data in the spindle motor encoders. If you mistakenly select the Stegmann servo motor encoder, the Memory Test will show a large number of errors. The Memory Test software as well as the encoder ID should warn you that you have made an incorrect selection in that situation.

The MHD motors will use the Heidenhain ECN/RCN413, EQN/RCN425, ECN1313 and EQN1325 encoders.

The MKD motors typically use resolver feedback, but according to the manual, they can come with encoder feedback. The MKE motors seem to be environmentally sealed versions of the MKD motors.

To avoid confusion, please note that Heidenhain has encoders using these same part numbers in their standard catalog, and they are completely different. The Heidenhain ECN1313 and EQN1325 ENDAT encoders were discussed in a previous section, and they are not the same as the Indramat encoders. The Endat encoders are used in Siemens, Bosch, Heidenhain, Baldor, B+R, and other motors, and they will not have the DSF part number on them.

 

Testing

As mentioned previously, Indramat MAC motors with Heidenhain Incremental encoders are tested as Generic Incremental Encoders using Data Display, Line Levels, Incremental Count Test, and Phase Test for a complete test. Indramat serial encoder types listed above (like most serial encoders) use only the Data Display and the Serial Count Test. The forward armature direction for Indramat motors is CW looking at the drive shaft end.

 

1 V p-p Signals –

The 1 V p-p signals must be verified on encoders that incorporate these signals. If the incremental count is not working correctly, that will be an immediate indication of a problem. However, the fact that the incremental count appears to be working is not sufficient. The amplitude of these signals should be checked. Amplitude measurement is probably best done with an oscilloscope. Connecting the scope ground clip to J1 pin 2 and checking the amplitude of the individual line at J1 pins 3, 4, 5, and 6, is a good method to use. This should be done coming out of the encoder before the signals go through any adapter modules. Since these are nominally 1 V p-p between true and complement lines, each individual signal will be about 0.5 V p-p.

Note that for the Indramat/Stegmann encoders, the encoder must be connected to the TI-5000JX and the
software on the Data Display reading serial position data. This is important because these encoders will not output the 1 V p-p signals until they receive software commands from the TI-5000JX (or and Indramat drive).

 

Data Display

Data Display is the initial test, and it is started by default when AThena is started. When already in another test, it can be started by clicking on the Data Display button among the test buttons at the top of the display. Use it for the following:

1. Turn the encoder to ensure that the encoder is counting approximately the right number of counts per revolution.
2. Use the commutation display to check or set the feedback commutation alignment.
3. Check the encoder status for the following: ensure that the encoder is indexed, communicating properly with the tester, not reporting internal errors, correctly displaying overheat and battery alarms, and displaying the correct encoder ID (if ID is implemented).

When Data Display first starts for the Indramat encoders, a support message box appears to display important support information relevant to the Indramat encoders since they are quite unique. The message content is as follows:

1. Read the Indramat Alignment Note From Mitchell Electronics, Inc.
2. Power down the TI-5000JX before connecting or disconnecting Indramat feedback devices.
3. Disconnect the resolver from the resolver board before reading the resolver board memory.

The alignment notes provide a detailed procedure for alignment when dealing with both encoders and resolvers, and it is very informative to read. The Data Display continuously reads position data from the

encoder, and it is best not to connect or disconnect the encoder while this data transfer is occurring. Entering Data Display without the feedback device connected could result in missing important data, so it is best to have the feedback connected before starting. Disconnecting the resolver board while the TI-5000JX is powered could cause transient voltages to develop on the resolver board. This is especially a problem if the resolver is connected to the resolver board during the memory read operation. Always disconnect the resolver from the memory board and power down the TI-5000JX before connecting to the resolver board to avoid the possibility of generating high voltage transients.

Data Display should be used as the initial check to see whether the encoder is doing anything at all. The following sections describe information shown on the display. Two examples of the Indramat Data Display
are shown below. The first is using the ECN413 selection which shows the multi-turn data disabled. An EQN425 encoder was intentionally used to make this graphic in order to show what the ENCODER ID field looks like with an incorrect selection. The second graphic uses the EQN425 selection, and it shows the additional multi-turn data. It also shows how the ENCODER ID field looks with a correct selection.

 

Commutation

The electrical angle can be used to check and set commutation using a static rotor lockup by applying a small lockup voltage to the stator windings. 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 it 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 correct. The electrical angle and mechanical angle are derived from the absolute position information in the serial data. The mechanical and electrical angle data is absolute immediately on power up for Indramat serial encoders.

The table below shows 2 different lockups that can be used to check or set commutation on Indramat digital motors with serial 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 Indramat). 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.

Unlike most feedback alignment discussed in this manual, Indramat digital motors do not have a common
lockup angle, and in general, they will all lock up at different angles. Indramat 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 record the +U –V and +U –W lockup angles provided by the memory test.

The MKD motors utilize a memory board along with the resolver. Again, you must perform a Memory Test to get the lockup angle for that particular motor. When you have the correct lockup angle, you can then lock up the motor and check for that resolver angle in the conventional manner.

A document is available from Mitchell Electronics, Inc. with more detail on Indramat alignment procedures.

 

Position Code Rings

There are significant differences between the Indramat encoders and other serial encoders described in this manual. The serial data returns sine and cosine amplitudes rather than position counts. In this regard, the data is similar to resolver data, and it can be converted to an angle. Furthermore, sine/cosine data is returned for the 1 period/revolution code ring and the 16 periods/revolution code ring for the 200 series encoders and for the 1 period/revolution code ring, 8 periods/revolution code ring and the 64 periods/revolution code ring for the 400 and 1300 series encoders. An absolute position angle can be calculated from the 1 period/rev data. However, this angle can be determined more accurately if it is interpolated using the finer resolution 8, 16, and 64 period/rev data. The TI-5000JX displays the data both ways as will be further explained.

As described above, the absolute position angle information is available as both mechanical and electrical angles. To display the electrical angle correctly, the number of poles must be set correctly. The mechanical angle always changes 360 degrees for a full rotation of the encoder. The mechanical angle should roughly agree with the angle in the 1R box. In fact, the 1R box provides the approximate angle, and that angle is further refined by interpolation with the angles in the 1/8R, 1/16R, and 1/64R boxes. While the 200 series encoders produce a 1R and 1/16R position, the 400 and 1300 series encoders produce 1R, 1/8R and 1/64R position data. This allows for even more precise interpolation.

It is not necessary to completely understand the interpolation. Rather, it is important to understand that the final angle is made up from the contributions of these various angles, and that even when working correctly, the mechanical angle will typically not agree exactly with the 1R angle. If we are not looking for perfect agreement, then why are the various angles displayed and how should we evaluate them? The following guidelines should help in evaluating the data for the ECN212 and EQN224 encoders:

1. Data in the Mechanical Angle, INCREMENTAL, 1/16R and 1R boxes should all be changing as the encoder is rotated.
2. The Mechanical Angle and 1R boxes should be approximately equal (within a few degrees).
3. As the data in the 1/16R box goes through 360 degrees, the 1R box data should change about 22 degrees (22.5 ideally).
4. As the data in the Mechanical Angle box changes by 360 degrees, the data in the INCREMENTAL box should change by about 1024 counts.

Count

The data in the INCREMENTAL box is captured as quadrature pulses on the A and B channel inputs. Since there is no index pulse to which it may be referenced, it must be compared with the absolute data to verify that the correct number of counts per revolution is occurring.

The ECN212C and EQN224 encoders provide 1024 (10 bit) incremental counts/revolution. The remaining Indramat encoder selections are 2048 (11 bit) incremental counts/revolution. The Data Display should be used as the initial check to see whether the encoder is doing anything at all. There are no alarm bits produced by these encoders. If no data is being sent from the encoder, that problem will be detected and reported in Data Display. An encoder may be connected to the TI-5000JX and rotated by hand through one revolution (determine one revolution by the mechanical angle and watching the shaft) to see whether the count is changing by approximately the correct amount. The count and all angles increase when the encoder is turned in the clockwise (CW) direction.

With the Indramat encoders made by Heidenhain, the incremental count and serial data functions are basically independent. With a malfunctioning encoder, it is possible to have a problem in receiving serial data but still see the incremental count change. However, the Indramat encoders made by Stegmann must receive serial data from the drive (or TI-5000JX) in order to enable the incremental outputs. A malfunction in the serial data will likely result in no incremental output signals being produced.

 

Revolutions Code Rings and Revolutions

While the ECN212, ECN413 and ECN1313 are single-turn encoders, the EQN224, EQN425, and EQN1325 are multi-turn encoders. The multi-turn encoders include revolution count information in the Revolutions Code Rings frame. The multi-turn encoders are capable of keeping track of 4096 revolutions (0 – 4095). The angle data from the revolution code rings is used to produce a revolutions count which is displayed in the REVOLUTIONS box. For single-turn encoders, the Revolutions Code Rings frame and REVOLUTIONS box will be disabled.

The revolutions are measure by 3 code wheels for 200 series encoders and 4 code wheels for 400 and 1300 series encoders. The wheels are driven by a gear train that provides ratios with reference to the main encoder shaft of 16:1, 256:1, and 4096:1 for 200 series and 8:1, 64:1, 512:1, and 4096:1 for the 400 series & Stegmann. The angles from these code wheels are displayed in the 16R, 256R, and 4096R boxes for the 200 series encoders and 8R, 64R, 512R, and 4096R boxes for the 400 series & Stegmann. Again, by mathematically interpolating these code ring angles, the exact number of turns can be determined. This is the number that appears in the REVOLUTIONS box. The following procedure will help determine that the revolution counting sections are working properly:

1. Rotate the encoder 128 revolutions. During the motion verify the following:
   a. The 1R angle should go through 360 128 times.
   b. The 16R angle should go through 360 very approximately 8 times.
   c. The 256R angle should change by approximately 180 degrees.
   d. The 4096Rev angle should change by approximately 11 degrees (ideally 11.25).
   
   
2. At the end of 128 revolutions, verify that the revolution count has changed by 128.

This procedure will help determine that the EQN425 and EQN1325 revolution counting sections are working properly:

1. Rotate the encoder 128 revolutions. During the motion verify the following:
   a. The 1R angle should go through 360 128 times.
   b. The 8R angle should go through 360 very approximately 16 times.
   c. The 64R angle should go through 360 very approximately 2 times.
   d. The 512R angle should change by approximately 90 degrees.
   e. The 4096R angle should change by approximately 11 degrees (ideally 11.25).
   
   
2. At the end of 128 revolutions, verify that the revolution count has changed by 128.

Of course there are many possible variations on this procedure. In general, if you turn it more than 128 revolutions, you will have a better feel for whether all parts are working properly. Conversely, if you turn it fewer times, the test will be less accurate. It is somewhat of a judgment call as to how much time you decide to spend turning the encoder to convince yourself that it is working properly.

Each of these angles is scanned at various times, and the information for each may not be current when the encoder is moving. In that regard, do not be alarmed if a wild revolution count is seen from time to time while the encoder is moving. However, the revolution count should be correct whenever the encoder is stopped.

When the Indramat motor is equipped with resolver feedback, use the resolver display. At this time, the TI-5000JX does not support reading revolution counts for multi-turn resolver feedback. See the Generic Resolvers section for more on motors with resolver feedback.

 

Encoder Status

INDEX – The INDEX box is disabled for all Indramat serial encoders because there is no indexing with these encoders. The displayed angles are absolute on power up.

DATA - If no data is being sent from the encoder, NONE will be displayed in the DATA box. If the TI- 5000JX and the encoder are communicating correctly, RECEIVING will be displayed in the DATA box. The cabling is the first thing to check if the encoder is not communicating, but it can also mean a component failure in the encoder.

Indramat encoders do not need to be indexed, they provide no internal errors bits, they do not need a battery, and they do not provide overheat information, so there are no fields on the Data Display for any of that information.

ENCODER ID – As shown in the Data Display screens above, the ENCODER ID field shows the type of encoder that has been detected from the encoder memory data via the serial data. If the encoder detected agrees with the encoder selected, the encoder type is followed by OK. If the selection does not agree with the type selected, the encoder type is followed by ERROR. In this case, you should check your selection. You probably made the wrong selection. However, it is possible that the encoder has been programmed with the wrong data. In any case, the cause of the error should be investigated.

 

Count Test

Currently there is no Count Test for the Indramat encoders. The procedure described in the preceding section can be used to verify correct counting.

 

Memory Test

As explained previously, the feedback for Indramat digital motors use a memory device containing motor parameters. This data is programmed in at the factory and cannot be changed by the drive. Some of the default tuning constants may be overridden by the drive, but the data in the encoder is fixed. This device 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 does this automatically as it reads and displays the various motor parameters. Any parameter that fails this check is not displayed, and “BAD DATA” is displayed in its place. We do not know what the drive requirements are, but the logical guess is that if there is even one bad parameter, the drive will not run the motor. Experience so far indicates that it is somewhat rare for the encoder memory to actually have a problem. Many things such as a bad encoder cable, incorrect connection of the TI-5000JX, etc. could cause a bad data read. Especially if you are unfamiliar with testing Indramat motors, you might check with Mitchell Electronics, Inc. if you have an encoder (or especially, several encoders) that do not read the data correctly.

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 ECN212 encoder. The motor type number and motor parameters are fairly self explanatory. These numbers should match reasonably well with the nameplate data. Toward the end of the right column is some information that is useful to the repairman. The number of pole pairs is 3, which indicates a 6 pole motor. This may not be universal, but it appears that the MDD motors are 6 poles, while the MHD, MKD, and MKE can be either 6 or 8 pole. The feedback type of 3 indicates the ECN212 encoder (as described above). The encoder count of 256 pulses/rev corresponds to 1024 counts/rev as read by the TI-5000JX. The commutation offset number of 238 is what tells the drive how to provide correctly timed armature currents to the motor. 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.

Note: If an encoder is replaced on an Indramat digital 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.

 

 

Comparing the above nameplate data to the encoder data below, we see a typical situation. The nameplate does not include all of the encoder data. Most of the data is very close, but the RPM data is further off than you might expect.

 

 

The 8729 series spindle motors seem to have only the Feedback Type and Encoder Count data included. All other data is zero. The report for spindle motors will show ‘NA/SPINDLE’ for all data except the Feedback Type and Encoder Count. The spindle motors do not have PM rotor, so there is no alignment and no lockup angles to report. 

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. If the encoder is from a spindle motor, there are fewer data fields, and errors will be shown for many of the fields if the correct spindle motor selection is not made. Insure that you use one of the Indramat Spindle Motor selections when performing a Memory Test on an encoder from spindle 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. Failure to use the TI-5104 Indramat Adapter Module.
5. Incorrect or faulty TI-5000JX test cable.
6. Faulty TI-5000JX.

An Indramat drive will alarm if there is an encoder data problem, so the problem cannot be ignored.

It is not uncommon for the Motor Type field to contain ‘?’ characters. These may be treated as a wildcard in parts of the field that do not affect data, but it is unknown why these characters appear in the data. The Indramat drive seems to accept them without any problem.

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

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

 

Saving Data -

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. Athena will make up a proposed filename which includes the Indramat motor part number, the type brand of encoder (Heidenhain or Stegmann), and type of encoder.

For example the software might propose:

Indramat_ MDD112D-N-020-N2L-130PB0_Heidenhain_DSF0XSN-H_ECN212_Enc.hex

You make use this proposed filename as it is, add to it, remove characters from it, or change it entirely as you desire. For example, you might wish to retain this info but add a job number to it such as:

Indramat_ MDD112D-N-020-N2L-130PB0_Heidenhain_DSF0XSN-H_ECN212_Enc_Job98765.hex

Just type in whatever you desire.

If there are ‘?’ characters in the Motor Type, Athena will convert those characters to ‘^’ characters because a ‘?’ is not a legal character in a Windows filename.