Kawasaki Motors and Serial Encoders

Overview

There are several models of Kawasaki serial encoders, and two are currently supported by the TI-5000JX. The H20/M21 8,192 count/rev encoders are used with relatively large robot motors. Connection to these encoders requires only 4 lines: 5 V power, ground, and a pair of RS485 data lines. The cables available are the TI-5011 (4 pin direct connection to the encoder) and the TI-5032 (17 pin circular MS type connector).

HE-02 8,192 count/rev encoders are used on somewhat smaller robot motors. They are supported by the TI-5023 (DB25 connector) and TI-5026 (17 pin circular MS type connector) cables. This encoder is the same as the 8192 count Sanyo Denki E03007758.

Types Supported

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

Identification

The following motor models use H20M21 encoders:

Sanyo Denki uses the P series part numbers for their motors too, and they show the bold character as the encoder identifier. The last two, L and X, are not in the Sanyo Denki literature but appear in the part numbers for Kawasaki motors using H20M21 encoders. There is some inconsistency in some of the descriptions in the manuals, but this should provide some useful guidance. The assignments are as follows:

HE-02 encoder part numbers are not as well known. The two part numbers that we have seen so far are listed below:

Testing

The model H20M21 is a serial encoder and (like most serial encoders) uses only the Data Display and the Count Test.

The model HE-02 encoder has both a quadrature pulse section and a serial section. To completely test these encoders, the quadrature pulse section should be tested like any standard quadrature pulse incremental encoder (8,192 counts/rev). Selecting this encoder from the Kawasaki menu allows testing the serial section using the Data Display and Count Test.

The forward armature direction for Kawasaki motors (like most Japanese motors) is CCW looking at the drive shaft end.

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).

The following sections describe information shown on the display

Commutation

The Fanuc style commutation gray code shown as C1 – C8 (HE-02 only) and 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. We strongly recommend using the electrical angle as the superior method of alignment for Kawasaki encoders. For a particular lockup polarity, the rotor will lock up in as many different positions as there are pole pairs but the gray code and 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 gray code, electrical angle and mechanical angle are derived from the position count. The position count is absolute immediately on power up for Kawasaki serial encoders.

The table below shows 3 different lockups which can be used to check or set commutation on motors using Kawasaki 4 pole and 8 pole motors with H20M21 and HE-02 serial encoders. The first one puts the feedback on a zero electrical angle which some users favor. It requires applying power to all 3 armature lines. 

The last 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 (CCW looking at the shaft). 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.

Count

The Count frame displays the encoder count both as a decimal and hexadecimal number. Users will typically be interested in only the decimal count, but encoder repairmen and other advanced users may find the hexadecimal representation useful. In general this count will not be zero on power up. This is an absolute encoder, and it will remember the count on power up. The number of counts/rev for the various models is shown in the table in an earlier section on types of encoders supported.

The H20M21 encoders are multi-turn encoders in that they keep track of revolutions. The position count is 0 to 8,191 (13 bits) and the revolution count is from -32,768 to 32,767 (16 bits). Since the position count and revolution count are not synchronized well with each other, they are displayed separated. The position count is displayed in the COUNT frame, and it will go to 8,191 and then back to 0 to start over (in the decimal representation).

The HE-02 uses a 0 to 8,191 (13 bit) position count and keeps track of revolutions from -128 to +127 (256 revolutions). This is displayed in the Count frame as 8 more bits of data (above the 13 position bits) as are most serial encoders.

Always verify that the encoder count appears to change by the correct number of counts/rev while turning the encoder. If the count is not changing, then there is an encoder problem. As described in a later section, the Count Test may be performed to more accurately determine whether the correct number of counts per revolution is occurring, but this is an important initial evaluation.

Serial encoders that include incremental lines, like the HE-02, are tested both as incremental encoders and serial encoders.

Encoder Status

• INDEX – The INDEX box is disabled for all Kawasaki serial encoders because these encoders display the correct count on power up without indexing.
• 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.
• INTERNAL ERROR - The information in this box reports on the error bits. The encoder literature for the H20/M21 describes 3 error bits:
  
  
  
  
  At this time we cannot be sure that the bit locations and identities have been determined correctly, but we believe that they have. We can force one of the error bits by interrupting the light source in the encoder. We believe that it is the ABSALM error that is produced in that case. Once the error has been produced in this manner, cycling powering to the encoder will restore proper operation. It will probably require testing known bad encoders to verify the error bits absolutely. In any case the Internal bit will display ALARM instead of OK, if any of the 3 bits monitored go HI. No error bits have been positively identified for the HE-02 encoder.
• BATTERY - The BATTERY box is disabled for Kawasaki serial encoder because they do not utilize battery backup.
• OVERHEAT - The OVERHEAT box is disabled for Kawasaki serial encoders because they do not report overheat conditions.
• ENCODER ID – The ENCODER ID box is disabled as there is no known identification data with the Kawasaki encoders.

Count Test

The Count Test can be started by clicking on the Count Test button among the test buttons at the top of the display. The Count Test it will verify that the encoder is incrementing the correct number of counts per revolution. The Count Test for the Kawasaki encoders is not significantly different from that for other encoders, so please refer to the general information on the count test in Section 2.2.2 for further details. The stuck bit test will test bit0 to bit12 for activity for 8,192 count 13 bit Kawasaki encoders.