Generic Resolvers

Overview

Resolver feedback is a special case. Rather than try to categorize or list as manufacturers all the various resolver setups, resolvers are listed simply as a generic type.

Setup

The FBK MFG key must be pressed until the top line of the display shows Generic Resolver. The FBK TYPE key has no function for the Generic Resolver Setup. The TI-3000JX needs 4 pieces of information to run the resolver based motor:

1. The number of poles of the motor.
2. The speed of the resolver.
3. Forward direction of resolver relative to armature phase forward direction (same or opposite).
4. The resolver angle when the rotor is locked using a +U –V lockup polarity.

This information can be found quickly and easily by a simple procedure. As this information is found using the procedure, it can be documented on a setup sheet and entered into the TI-3000JX using the Setup Menu. The setup sheet documents can be cataloged and the information simply entered into the TI-3000JX the next time a motor of the same type is used. This documentation will save a lot of time and provide additional confidence when encountering the same motor in the future.

The 10 step procedure is described below. On the page following the procedure a form is shown that can be used to record the motor information during the procedure. You may wish to make copies of this page for recording your information.

1. With the armature disconnected from the amplifier, connect a low voltage (around 5 volts, preferably adjustable from a small bench power supply) with + to the U and - to the V armature leads (or +A, -B, or however they are designated). The motor should move to a position where it locks up.
   
   Note: If you do not have information on armature pinouts, make up your own assignments and proceed.  Enter the pinout designations on the worksheet.
   
   
2. Slowly rotate the motor by hand through a full revolution and note the number of different positions in which it locks up in one rotation. Multiply that number by 2 and enter it as the number of poles on the worksheet. For instance, if it locks up in 4 different positions, it is an 8 pole motor.
   
   
3. Visually note the lockup position. Turn off the power supply, and leaving the + power supply lead on U, move the - lead from V to W. Turn the power supply back on, and the motor should move a small amount either CW or CCW. Note this direction, CW or CCW, on the worksheet as the forward armature direction.
   
   
4. Connect the resolver leads to the TI-3000JX resolver terminal block J12 in the manner suggested by the motor manufacturer. If no information is available, determine the excitation, sine and cosine windings by DC resistance checks. Make your own pin assignments and connect accordingly. Pin 1 of the resolver connector is the one closest to the display, and the pin assignments are:
   
   

   Pin	Signal	Usage
   1	GND	Connect one resolver rotor lead here for minimum excitation.
   2	EXC	Connect the rotor + excitation lead here.
   3	EXC*	Connect one resolver rotor lead here for maximum excitation.
   4	COS	Connect the + cosine lead here.
   5	COS*	Connect the - cosine lead here.
   6	SIN	Connect the + sine lead here.
   7	SIN*	Connect the - sine lead here.

   
   Note: Please see the end of this section for more tips on resolvers.
   
   
5. Power up the TI-3000JX and press the MFG key until Generic Resolver appears on the display. Press the F1 key to use the resolver frequency setup function. Select a frequency range of 1 - 4 (by pressing keys 1 through 4) and fine tune the frequency up or down using the arrow keys. For best results, connect an oscilloscope to the cosine and sine signals returning to the TI-3000JX (J12 pins 4 and 6, ground clip to pin 1, 5 or 7) to verify that a good clean waveform exists. If the waveform is poor, the frequency may need to be adjusted (usually increased) and/or the excitation level reduced. The excitation may be reduced by 1/2 by moving the excitation line from J12-3 (EXC*) to J12-1 (GND).
   
   
6. Press the DEBUG key so that the angle display appears on the 3rd line. Move the motor to verify that the resolver angle changes.
   
   
7. Rotate the motor one full revolution while watching the angle display. Record the number of times the angle passes through zero for one full revolution as the resolver speed. For instance, if the resolver angle goes from 359 degrees to 0 degrees 3 times in one revolution, then it is a 3 speed resolver.
   
   
8. Note the direction of rotation which causes the displayed angle to increase from 0, 90, 180, 270, and back to 0. This is the forward rotation of the resolver. Note this direction, CW or CCW, on the worksheet as the forward resolver direction and indicate ‘same’ or ‘opposite’ with reference to the forward armature direction.
   
   Note: Until software V3.1 Beta11, the software did not provide for reversing the resolver direction, so the resolver direction had to be reversed by interchanging the SIN and SIN* resolver leads. If you prefer to switch SIN and SIN* leads, then make sure that you leave the direction setting on ‘S’ for same. Also note that switching the SIN and SIN* leads changes the direction in which the displayed resolver angle increases. However changing from ‘S’ to ‘O’ or from ‘O’ to ‘S’ does not change the direction of the displayed resolver angle. That direction remains the same and will agree with the TI-5000JX displayed resolver angles. The ‘S’ or ‘O’ selection simply informs the TI-3000JX runtime software as to whether the rotation of the resolver and armature phases are the same or opposite so that it can take that into account and correctly commutate the motor.
   
   
9. Again apply a DC voltage + to U and - to V. Move the motor through one rotation in the forward direction, and record each lockup angle starting with the smallest first. There will be one lockup position angle for each pole pair. For instance, a 2 pole motor will have 1 angle, while an 8 pole will have 4 lockup angles.
   
   
10. All the information is now available to enter into the TI-3000JX. Press the SETUP key, and an entry screen will appear as shown below.

The cursor will be on the field for the number of poles. It will read either 2 as the default or it will read the last number entered. Each time the EDIT key is pressed, the number will increment to a new number of poles. After reading 20, it will return to 2. Press EDIT until it reads the number of poles indicated on the worksheet.

With the number of poles showing, press the ENTER key, and the cursor will move to the Speed field which will read either 1 as the default or the last number entered. Each time the EDIT key is pressed, the number will increment to a new speed. After reading 4, it will return to 1. Press EDIT until it reads the speed indicated on the worksheet.

With the correct speed showing, press the ENTER key The cursor will move to the Direction field which will read either ‘S’ to indicate that the forward armature direction and forward resolver direction are the same or ‘O’ to indicate that the directions are opposite. Each time the EDIT key is pressed, the indication will switch between ‘S’ and ‘O’. Press EDIT until it reads the direction indicated on the worksheet.

With the correct speed showing, press the ENTER key, and the cursor will move to the Angle field which will read either 000 as the default or the last angle entered. Key in 3 digits to enter the lowest number of degrees recorded on the worksheet in the lockup data. After the 3rd digit is entered the cursor will jump back to the Poles field. You do have to enter leading zeros. For instance, 30 degrees must be entered as 030.

Review the number of poles, resolver speed, and angle showing on the display. If any are not correct, use the ENTER key to move to that field and correct the data as described above. When the data is correct, again press the SETUP key to exit the resolver setup menu.

The display will show the information as follows:

For instance, if it is an 8 pole motor with a 4 speed resolver that locks up at 30 degrees with the resolver direction the same as the armature direction, the display would look like the example above.

Debugging

Debugging is a quick and essential step that must be accomplished before trying to run the motor. If there are any problems in the setup, correct debugging should find them. If the correct setup has not been verified by debugging, there is nothing to be accomplished by attempting to run the motor.

Section 2.2.3 provides general information about debugging the TI-3000JX setup. You will want to be familiar with that material.

When you believe that the TI-3000JX is properly set up (as described in the previous section), perform the following steps to debug the setup:

1. Press the DEBUG key to enter DEBUG mode.
   
   
2. Rotate the shaft and verify that the resolver angle moves smoothly through the entire range of angles from 0 to 359 degrees. It should move through that range the same number of times as the resolver speed (single speed – 1 time, 4 speed – 4 times, etc.).
   
   
3. Verify that the armature leads are not connected to the drive. From the lockup power supply, connect the + lead to the U phase and the – lead to the V phase
   
   
4. Switch on the lockup power supply. The angle reading should be very close to the lockup angle that you recorded on your worksheet. For single speed resolvers and motor poles great than 2, there will be multiple lockup angles.]
   
   
5. On the TI-3000JX display, you should see V = H and W = L. When you wiggle the shaft slightly, you should see U change or toggle between H and L. This is very important. If this does not happen, the motor cannot run properly, and you have a mistake in your setup that must be corrected.
   
   
6. Switch off the lockup power supply and move the – lead from phase V to phase W. This will provide a valuable cross-check for verifying proper operation.
   
   
7. Switch on the power supply and note which way the motor jogs. This should agree with the forward direction you noted on your worksheet.
   
   
8. Read the angle from the TI-3000JX display. If it is greater than the angle you read with the +U –V lockup (providing the angle did not move through zero), the resolver and armature rotation are the same. Verify that your display shows ‘DS’ meaning ‘same direction’. If the displayed angle is less than the angle you read with the +U –V lockup (providing the angle did not move through zero), the resolver and armature rotation are opposite. Verify that your display shows ‘DO’ meaning ‘opposite direction’.
   
   
9. On the TI-3000JX display, you should see U = L and V = H. When you wiggle the shaft slightly, you should see W change or toggle between H and L. This is very important. If this does not happen, the motor cannot run properly, and you have a mistake in your setup that must be corrected.

Those specific setup checks should help insure that your resolver motor will run correctly. For more general information on debugging your setup, see Section 2.2.3.

Running

Section 2.2.4 provides general information about running motors with the TI-3000JX. You will want to be familiar with that material.

Section 2.2.5 provides safety information to be observed when running motors with the TI-3000JX. Please read this section carefully and exercise all safety considerations.

Considerations specific to running resolver motors usually have to do with minimizing noise on resolver lines. Excessive noise pickup on these lines can result in clicking sounds from the motor or very rough running of the motor. When noise is a problem, you can see the noise on the resolver signals by using an oscilloscope. Use the TI-3011 Resolver Breakout board to easily connect the scope. As you take measures to reduce noise, you can evaluate your progress by looking at the signals on the scope. You can compare what it looks like when running with how it looks with the drive turned off.

Here are some further points to help reduce noise:

1. Make sure that you have a ground continuous from the motor body to the body of the drive. The drive cable has a G pin on it that goes to the drive body. The motor usually has a ground pin on the power connector. Make sure you make that connection.
   
   
2. Sometimes a shielded cable for the armature leads will help.
   
   
3. Sometimes a shielded cable for the resolver leads will help.
   
   
4. Try to keep the power leads and feedback leads as far apart as possible.

General Resolver Information

Excitation Frequency Adjustment –

The TI-3000JX provides support for resolver checkout through the use of an Analog Devices resolver to digital converter chip set. This interface is built into the TI-3000JX board. Part of this interface provides the resolver excitation signal whose frequency is adjustable in 4 steps to these maximum frequencies: 2,000, 5,000, 10,000 and 20,000 Hz. A digital potentiometer adjustment allows each of these base frequencies to be adjusted down to about 1/2 the maximum values. This provides most frequencies between 2,000 and 20,000 Hz. The resolver to digital converter is specified only for excitation frequencies from 3,000 Hz. to 20,000 Hz. Typical components will operate down to 1,250 Hz. or so, but it is best to operate in the 3,000 Hz. to 20,000 Hz. range whenever possible. The range switching and potentiometer adjustments are done electronically, so the user makes these adjustments from the TI-3000JX keypad.

Note: The exact frequencies covered vary due to component tolerances, and all frequencies may not be attainable by a particular unit. This is a property of the Analog Devices component used, and not a function of the circuit design. Normally a frequency will be attainable that is close enough to the desired frequency.

The excitation frequency is displayed on the LCD display during adjustment (see the 10 step procedure for setting up resolver motors for details). With Generic Resolver selected as the feedback manufacturer, pressing F2 from Stop Mode will allow frequency setting. The table below shows the approximate range of frequencies for each dipswitch setting.

The frequencies shown are nominal, and actual frequencies may vary due to component tolerances. The output frequency range is specified from 2,000 Hz. to 20,000 Hz. Some parts will adjust down to 1,250 Hz., but other parts will produce distorted waveforms when the frequency is adjusted below 2,000 Hz.

Convenient test points on the TI-3011 Breakout Board allow easy connection to an oscilloscope. This board can be connected between the resolver terminal block and the TI-3000JX connector whenever oscilloscope measurements are desired. At other times it may be removed or left in place at the user's discretion. Test points are provided for the excitation signal to the resolver and for the sine and cosine signals returned from the resolver. Observing these signals with an oscilloscope will provide most useful information with regard to signal distortion that could be responsible for poor readings.

Connecting the Resolver –

The first step in checking out a resolver is to connect the resolver to terminal block J12 of the TI-3000JX. The typical colors and signal designations are shown in the table below:

Excitation Amplitude and Distortion –

Note that the above chart shows 2 possibilities for connecting R3. Connecting this line to EXC* will provide twice as much excitation voltage to the resolver as connecting to GND. The ground option should be used if the maximum COS or SIN input signals are greater than 3.1 V peak ( 6.2V p-p or 2.2 V RMS). Depending on the resolver transformation ratio, it may require more or less drive for the maximum input to be as near as possible, but less than 3.1 V peak. The resolver must be rotated to find the points of maximum cosine and sine output when checking for proper input levels.

The other consideration with respect to excitation amplitude is waveform distortion. Sometimes the amplitude must be reduced to eliminate distortion. In other situations, the distortion may be due to using an excitation frequency below the frequency recommended by the resolver or motor manufacturer. The waveform distortion is generally due to flux saturation in the resolver’s iron magnetic flux path. Saturation can be caused by an excitation voltage that is too high or by an excitation frequency that is too low. Sometimes distortion indicates a faulty resolver.

Rotating a single speed resolver one full turn from the zero angle point should cause the angle shown in Debug Mode to move through a range from 0 to 359. Notice the use of the term "single speed". Resolvers can have various numbers of poles just like motors. A 2 pole resolver is referred to as a single speed resolver. A 4 pole resolver is a 2 speed resolver and so on with the speed being the same as the number of pole pairs. Servo motors will commonly use 1, 2, 3 and 4 speed resolvers. Other kinds of applications may use resolvers as high as 36 or more speeds. The number of the speed determines the number of times the resolver angle will go through 360 degrees during a single mechanical revolution. For instance, a 4 speed resolver will be seen to go through 360 degrees 4 times in a single revolution.

Note: The Analog Devices resolver/digital converter IC (used in the TI-3000JX resolver circuitry) employs very HI impedance inputs to avoid excessively loading the resolver connected to it. These inputs (like most HI impedance inputs) are very susceptible to noise pickup when they are open circuited and not connected to a resolver. Because of this, it is likely that you might see the resolver angle changing with no resolver connected. This is normal, and should not cause alarm.

Effect of Changing Resolver Connections –

The question often comes up as to the effect of reversing various resolver leads. The following table shows the effect of lead reversal.

In the above table, when we say “reverse sine” we mean to switch the SIN and SIN* resolver leads on the terminal block. When we say “exchange sine and cosine” we mean to connect the resolver SIN and SIN* leads to the terminal block COS and COS* terminals respectively and connect the resolver COS and COS* leads to the terminal block SIN and SIN* terminals respectively.

You can see that the effect of making a combination of changes can be predicted by the individual changes. For instance, reversing the sine leads will reverse the direction. If we then reverse the cosine leads, the direction is reversed again, and the angle is advanced by 180 degrees. The double reversal of direction puts us back to the original direction, and we are advanced by 180 degrees. That is the same thing the table tells us for reversing the sine and cosine leads.

We could predict that exchanging the sine and cosine leads and reversing the excitation leads would advance the angle by 270 degrees and reverse the rotation.

Resolver Versus Armature Direction –

In previous software revisions, it was necessary to swap the sine leads to reverse the resolver direction, if the resolver direction and armature direction were opposite. The above discussion makes it clear why simply reversing the sine leads is the least complicated way to change the resolver direction.

However, the V3.1 software provides a Same/Opposite selection in the setup (see procedure above) that takes care of the direction issue in software so that it is no longer necessary to reverse sine leads. This allows the resolver cable to remain the same for the TI-5000JX and TI-3000JX thus removing an opportunity for mistakes during the test process.

Resolver Diagnostics –

To verify proper operation of the TI-3000JX resolver circuitry, get the ‘TI-3000JX Resolver Diagnostics’ document from the Customer Page at http://www.mitchell-electronics.com . This document describes some simple procedures to verify proper operation.