Troubleshooting

ER21 alarm

• Question: RE21 Alarm.
• Solution: include two situations:
  • The customer site is indeed under-voltage power supply,
  • AC220V wiring :The possible wiring is L1 and L2, which are replaced by L1 and L3.

ER30/ER34/ER36/ER37 alarm

• Problem: When first power-on or motor runs half-turn,then appear alarm ER30/ER34/ER36/ER37.
• Solution: The phase sequence of the power line UVW is wrong, it may be the customer has connected it wrong,or it may be that WECON line sequence is marked wrong. Remove the motor from machine and test the phase sequence.

ER37 alarm

• Problem: When first time to power on servo and run about half circle,then the alarm ER37 appear.
• Solution: In addition to the wrong phase sequence of the power line UVW, or the drive and the motor can not match.

ER23 alarm

• Problem: ER23 alarms.The built-in resistance of servo is possible to be broken
• Solution: User could buy an external braking resistor with corresponding power.(such as 200W 50 ohm). The power of braking resistor could be calculate with power calculation tool of WECON servo brake resistor as below link.
  • http://docs.we-con.com.cn/wiki/servo/view/6.Software/

How to connect a external braking resistor?

• Disconnect the short wire between C-D first
• Then connect the external braking resistor between P+ and C.

ER27 and ER31 alarm

• Problem: ER27 and ER31 alarm.
• Solution: ER27: Encoder cable does not connect well.ER31:Power cable do not connect well.Check whether the lines are connected properly.If the alarm still occurs, replace the motor.

ER26 alarm

Problem: ER26 alarms.

Solution: Motor type error. Please check whether the servo drive supports this motor

Configuration

Modify P0-16 in panel

In servo panel, we want to set P0-16=200. 

Use and share of internal multi-position and speed mixed mode

(only Servo firmware V1.10 and above can support）

• p0-1 set 4 speed and position mixed mode
• p1-1 set 0 to go internal speed
• p1-2 set speed
• p1-6 set 1 to go to the internal position
• p6-5 set to 17 switch mode signal
• p6-7 set 1 virtual switching signal
• p6-8 set 20 internal multi-position enable signal
• p6-10 set 1   
• p7-1 set 1 internal multi-position cyclic operation
• p7-2 p7-3 Set the start section and end section
• p7-5 Set absolute and relative position
• p7-9 p7-10 set position pulse and speed
• p7-12 Set multiple position waiting time
• Then p6-4 set 1 servo enable (DI2is valid as internal speed mode)
• p13-2 is the switch mode switch, set 1 (DI2 invalid as the internal multi-segment position mode)

Multi-turn servos and multiple simultaneous communication timeout problems

Problem: When the customer's site 5V communicates with two multi-turn absolute value servo by rs485 at the same time, the position address in the encoder circle of the servos cannot be read in real time, and the communication of a single servo is normal.

Solution: After testing,Set more retry times in SD2598,then this problem can be solved.

Servo rigidity

Problem: Many times we will encounter insufficient servo rigidity and motor shaking, especially in powder packaging, labeling, discs record and other equipment. There are great requirements for the rigidity of the servo. The following parameters are specific to our servos. It is a good fix for our rigidity problem.

solve:

• P3-2 load rigidity level selection, this parameter is appropriately increased.But you have to ensure that the motor do not have noise.
• P3-1 Load inertia ratio. This is complementary to P3-2. Under the condition that the motor must can not have noise, these two parameters are adjusted.
• P2-1 to P2-3 should be increased appropriately for general rigidity requirements, and the three parameters can be increased appropriately to basically meet the needs of customers.

The servo rotates abnormally

Question: Regarding the solution to the abnormal rotation of the servo due to the inconsistent enable disconnection time after the servos of different power ranges are powered off.

Solution: When using VD2 drives with different power ranges on one machine, when the servo is powered off at the same time, the capacitance of the drive is inconsistent, resulting in the inconsistent time of the servo's enable disconnection, which will cause the servo to be inconsistent. In certain modes, abnormal rotation may occur.

The current solution is to turn off the enable of each servo after the servo motor stops running to avoid it.

In position mode, external pulse positioning, servo positioning is inaccurate

Problem: In position mode,servo positioning are inaccurate with external pulse positioning.

Solution: There are two reasons: one is a mechanical problem, and the other is an electrical problem. Mechanical problems are usually caused by gaps in lead screws and gears, or belts and chains are tight, or coupling parts such as couplings are not firmly connected; electrical problems are generally interference and wiring problems.

Electrical problems

Monitor whether the number of input command pulses of the servo is consistent with that sent by the PLC. Pay attention to the relative value, or send it after resetting after power off and restart.

If there is an inconsistency, there is an electrical problem. If the number of pulses sent and the number of pulses received are orders of magnitude different, the high probability is a wiring problem. If the numbers are close, but there is always an error, then the high probability is an interference problem. There are several methods as follows :

• Check whether the pulse wiring is correct, whether it is firm, whether the wiring is separated from the power line, you can take the pulse line out of the wire slot and leave it in the air for testing.
• Check if there are interference sources, pay special attention to the electrical components that are working, such as inverters, contactors, etc., and take care of them, such as add magnet ring, freewheel diodes etc. (requires troubleshoot experience).
• If you use a switching power supply, it is recommended to use the DC24V power supply of the PLC. The power supply is easy to be interfered and other loads carried by it are also easy to cause interference, such as solenoid valve relays. (Easy to use, solve 90% interference problems)
• Whether the pulse frequency sent by the PLC is too fast, the filter parameter of the servo setting, taking into account the attenuation, generally set 1/4 the duration of the pulse width of the highest frequency.

• In special cases, the anti-interference ability can be enhanced: 2KΩ resistor can be connected between the pulse output terminal Y0 and the pulse power supply DC24V+, which can increase the rising edge time and increase the duty cycle.

Eliminate the problem through the above several methods, so that the number of input command pulses is consistent with the number of pulses sent by the PLC.

Machine problem

If the number of input command pulses is the same as the number of pulses sent by the PLC, the electrical problem is eliminated, which is basically a mechanical problem. There are several methods as follows:

• Keep going in one direction at a fixed length, if it is still inaccurate, the problem caused by the mechanical gap can be eliminated.
• Check whether the joints such as the coupling and the motor shaft are firm.

When the machine is stopped, the film cutter moves slowly

Problem: When the machine is stopped, the film cutter has a slow movement problem.

Solution: The processing method of the interference signal from the servo receiving is as follows.

Because if the filtering time is too long, it may filter out normal PLC pulses. So it should be set according to the on-site process requirements. For example, the field technology requires the maximum pulse frequency of the PLC to be 100k, then convert the pulse sent out under the condition of 100k, the pulse period is about 1/100k=10us, the theoretical pulse width is 5us, and the actual situation is a little smaller than 5us. . Therefore, in view of this situation, it is clear that p0-14 cannot be set to more than 6.

1. Increase p0-14. VD2 servo filter time can be modified more.
2. The equipment is not connected to the earth. Make sure that the servo drive-motor-chassis-earth is effectively connected. The servo, PLC, and switching power supply are all grounded.
3. The DC24v common end of the servo control line is best to be directly powered by the output DC24v of the plc, which is isolated from other devices.

Real-time synchronization with PLC curve, follow---requiring high servo response occasions

Process requirements

There are some applications where the deviation between the position of the servo and the pulse sent by the PLC should not be too large. Winding machines, textiles and other equipment will respond quickly to the pulse received by the servo from the PLC to avoid problems such as disconnection. Generally, the acceleration time is very long, but the speed is high.

Solution

For the PLC setting, you can do the acceleration/deceleration frequency by yourself. It is not recommended to directly use the PLC's own acceleration/deceleration time. The servo settings are as follows:

1. You can use our servo debugging(self-turning) function to set the tuned inertia and rigidity into the servo.
2. P3-2 load rigidity level selection: this parameter is increased appropriately,and the premise is to ensure that  that the motor will not have abnormal noise.
3. P2-9 speed feed forward gain set to the maximum 100%.
4. After changing the above two parameters, the follow-up effect has been significantly improved. If the follow-up requirements of the customer are still not satisfy, you can change P3-3 to 1 to control by manual. Then manually adjust [P2-1]Position loop gain, gradually increase the position loop gain, and increase the value upward while ensuring that the motor will not have abnormal noise.

Actual test: From 0-3000 revolutions in about 3 seconds, the position deviation of the servo should not exceed 2 to 3 degrees of the motor (10,000 pulses per circle means that the position deviation does not exceed 56 to 83 pulses).

Test process: After completing the setting process of 1-3 (rigidity 16), the servo position deviation is about 120 pulses, and then manually adjust the [P2-1] position loop gain to 1600, and the maximum position deviation tested is 65 pulses. Achieve customer requirement.

Mode switching (speed mode/torque mode)

Process requirements

The servo normally runs at 500 rpm in the speed mode. When the DI_5 signal is input, the working mode is switched to the torque mode, and the speed is limited to 150 rpm. The torque setting value is 80.0%. When the servo torque reaches the setting value, the DO_3 signal is output to the PLC, and the PLC performs reverse operation and switches back to the speed mode at the same time.

Solution

Adjust the parameters according to the yellow font of the icon below, and the steps are as follows:

Instruction:

• The yellow parameter is required, other parameters can be adjusted according to the usage.
• P6-08 DI_3 instruction inversion: used to control the direction in speed and torque mode.
• P6-14 DI_5 mixed mode selection: used to switch between speed and torque modes.
• P6-30 DO_3 torque arrival output: when the current servo current torque reaches the sum of the two parameters P5-20 and P5-21, the DO_3 signal is output.
• The speed mode is limited by P1-12/P1-13, and the torque mode is limited by P1-17/P1-18.
• In the torque mode, the servo running is not stable during debugging. The problem is solved after adjusting P3-01 and P3-02.

The software waveform monitoring of the servo PC tool is as follows:

Figure 2-6

Figure 2-7

The actual running video is as follows:

Debugging Application

In the case of only positioning control-servo positioning is inaccurate

Problem analysis

(1) The servo has received too many pulses. For example, the single-turn pulse of the servo is 10000, and the plc sends 10000 pulses to the servo, but the servo has moved more than one circle or more.

(2) The pulse received by the servo is less. For example, the single-turn pulse of the servo is 10000, and the plc sends 10000 pulses to the servo, but the servo does not complete one turn.

Therefore, we need to determine the situation first, and then make targeted corrections.

Checking problem reason

We can make the plc send a fixed amount of pulses (it is better to make the servo rotate full circle more intuitive), and then look at the servo's encoder cumulative position U0-13.

The value of U0-13 is related to the number of digits of the motor encoder. 2500 lines correspond to 10000/turn, 17 digits correspond to 131072/turn, and 23 digits correspond to 8388608/turn.

If there is no way to turn a full circle due to the mechanism, you can refer to the following formula for observation: 2500 lines, encoder cumulative position = plc sent pulse number * 10000/p0-16.

• 17-bit encoder cumulative position = plc sent pulses * 131072/p0-16
• 23-bit encoder cumulative position = plc sent pulses *8388608/p0-16

Through the above determination method, we can basically know what the servo problem situation is.

Solution

The first case

If the servo receives too many pulses, it means that the servo drive has received the interference signal as a pulse signal. At this time, we need to adjust the position pulse filter on the servo side to filter out the interference signal. The corresponding parameter is p0-14.

Figure 3- 2

The value of P0-14 cannot be adjusted to the maximum blindly, because if the filtering time is too long, it may filter out normal PLC pulses. So it should be set according to the on-site process requirements. For example, the field technology requires the maximum pulse frequency of the PLC to be 100kHZ, then we can calculate the pulse period sent out under the condition of 100k.The pulse period is about 1/100k=10us, the theoretical pulse width is 10us/2=5us, and the actual situation is a little smaller than 5us. Therefore, in view of this situation, it is clear that p0-14 cannot be set to more than 6.

Theoretically, the problem can be solved by the setting of p0-14. If it does not work, it means that the electromagnetic environment on site is indeed very poor. At this time, you should find the interference source first. There are two common situations:

1. The equipment is not connected to the ground. Ensure that the servo drive-motor-machine casing-ground is effectively connected.
2. Interference comes from the power supply. Generally, the DC24v common terminal of the servo drive control line is often directly connected from the power supply. However, the power supply may also provide high-power solenoid valves, contactors, and frequency conversions in addition to the servo. The moment when these devices are turned on/off, it is easy to make the DC24v drop or rise instantly, which will affect the servo end. Therefore, it is recommended that the DC24v common end of the servo control line is directly powered by the output DC24v of the plc(independent power supply), and it is isolated from other devices.

The second case

That is, there are fewer pulses received by the servo, so there are two common reasons for this situation:

• Pulse direction signal interference during servo operation, that is to say, when that the current servo is in forward rotation, and suddenly the servo pulse direction signal pin comes to a low level to inform the servo to reverse. Due to the stuck pulse inside the servo, At this time, the servo will not reverse, but will only cancel the pulse, so the final result is that the servo does not run,looks like servo do not receive full pulse.
  • The solution for this situation is very simple. Remove the servo pulse direction signal and run for a while to see if it is normal. If possible, it is easy to see with an oscilloscope. If this is the case, the solution is to isolate the 24v public end.
• The servo control line is longer than 10 meters, and the impedance is too large, which leads to signal attenuation. The original normal pulse waveform is distorted and then filtered out by the servo driver, and the final result is that the servo runs less. The solution is, you can try to connect a resistance of about 1000 ohms (1 watt) in parallel between the PL and plus- of the servo drive. As shown in the figure:

Servo motor vibrates and screams

Problem analysis

It is often encountered that the servo will vibrate at a high frequency when it is in enable state, and in severe cases, it will be accompanied by screams. The root of the problem is mostly servo parameters. High-frequency vibration is caused by the resonance of the motor and the equipment. We need to avoid the resonance frequency range. A small part of the situation is a mechanical structure problem.

In the application environment of multiple servos, first of all, we have to determine which servo is re-vibrating. The scene environment is noisy, and the vibration can be transmitted through metal. It is easy to confuse us.

For example, we has a painful experience, a three-axis application environment. At that time, the FAE engineer at the site always thought that the z-axis was re-vibrating, but the monitoring waveform was not there. Later, it was discovered that the x-axis was re-vibrating, which was transmitted to the z-axis, which wasted a lot of time.

Positioning problem

First Method

Open the servo PC software and monitor the servo waveform, as shown in Figure 3-4 is a normal situation, and Figure 3-5 is a typical vibration situation.

Figure 3-4

Figure 3-5

Second Method

Turn off the servo enable signal and the motor is still vibrating to confirm that the vibration source is not the motor. If the motor does not vibrate, it can be determined that the vibrating source is the motor.

Solve vibrating problem

Solution after locking the vibrating source:

(1) Open the PC monitor software to monitor the vibration frequency, whether it corresponds to the value of P4-5 first notch filter frequency.

For example, if the vibration frequency is occasionally 300 and occasionally 500, you can set P4-5 to 400, and then increase the value of the first notch filter width of P4-7.

(2) After adjusting the frequency of the first notch filter, adjust the P4-4 torque filter time constant. If the value is adjusted to a lower value, the vibration decreases, and then continue to adjust lower with small value. If it is not ideal, you can decrease the value P4-6:1st notch depth (decreasing the value will affect the response speed of the servo).

If the above methods are not ideal, consider reducing the rigidity level, and the adjusted waveform will look like this as shown in Figure 3-6.

Figure 3-6

For vibration caused by a small probability of mechanical structure

In the case of screw drive, it mainly depends on whether the motor shaft and the connector are parallel, whether there is left and right shaking, and whether the screws of the connector are locked well.

Figure 3-7

The same is true for belt drive, which mainly depends on whether the belt is tilted left and right, and whether the synchronization wheel screw is locked well.

Figure 3-8

Too slow servo response affects overall output

In some simple reciprocating positioning and feeding occasions, such as high-speed one-to-one mask machine, terminal machine, feeder, etc., servo positioning is required to respond quickly to achieve higher output of the equipment as a whole. At this time, the servo also needs to adjust the gain with plc. .

Problem analysis

Figure 3-9 is a typical graph before optimization. After the servo finish debugging(auto-tuning), without parameter adjustment, the whole positioning time is almost 225ms, and the plc is 50ms acceleration and deceleration time, so it runs softly.

Figure 3-9

Solution

Optimize the acceleration and deceleration time of PLC

Optimize the acceleration and deceleration time of the PLC first. The acceleration time can be set as small as 10ms or less. The deceleration time can be longer but generally can be done within 50ms. If the load is small, the acceleration time can be consistent with the acceleration time, unless the load inertia ratio is very big, then adjust accordingly.

As shown in the figure: we directly press the acceleration and deceleration of the plc below 5ms, and the overall positioning time is shortened to about 155ms, but it can be seen that the servo lag in the second half of the deceleration is serious and there is a lag of about 75ms, so we have to start adjusting the servo parameters.

The rigidity level directly adopts self-tuning

The rigidity level can be directly used as the recommended level from self-tuning, without any changes. Change [P3-3] to 1(manual setting). Then, manually adjust [P2-1]:position loop gain, and gradually increase the position loop gain.

Figure 3- 11

As shown in the figure above, the position loop gain is 450, the overall positioning time is shortened to 120ms, the second half of the deceleration lag is also shortened to 40ms, there is no overshoot and no vibration, and the gain still can be adjusted up.

Comparison chart

Finally, take a look at the final comparison chart. This is that after the position loop gain is set to 550, the overall positioning time is shortened to 107 ms, which is twice as short as the initial 225 ms.

Figure 3- 12

Summary

The cognition of rigidity level: the rigidity level parameter itself has no meaning for the internal algorithm of the servo. It acts more as a "shortcut key", and the position loop gain, speed loop gain, speed loop integral time constant, and torque filter parameters these four parameters can be quickly set by the choice of rigidity level only. And the values of these four parameters at each rigidity level are the best ratios obtained by our research and development according to the theoretical algorithm, just like the formula, of course, it is only limited to the theory, so there is also the parameter p3-3. When we find that directly changing the rigidity level cannot achieve the effect we want, we need to change p3-3 to manual setting, and fine-tune a certain parameter by observing the curve, such as the position loop gain.

Application occasions of large inertia pulleys-Servo stop instability

Problem analysis

In the application of large inertia pulley, the servo stops unstable.

Solution

Servo tuning

• Step 1: Preparation
  • P4-4 Torque filtering time constant: try to set the minimum value to 10 first (no filtering);
  • P2-3 Speed loop integral time, set 5000 first; (when 5000, the influence of this parameter is small)
• The second step: gradually adjust P2-2 speed loop gain; the larger the value, the faster the response;
• Step 2: gradually adjust P2-3 speed loop integral time constant; the smaller the value, the faster the response;
• Step 3: adjust P2-1 position loop gain, the larger the value, the faster the response;

Parameters and curves before commissioning

Figure 3- 13

Figure 3- 14

It can be seen from the above figure that there will be a short period of uniform speed at the end of the curve and then decelerate to stop, so that there will be an obvious slow-speed and then stop action on the motor.

Such as video action

Adjust P2-2 parameters

When adjusting the parameters, first increase or decrease the parameters, try several times to see the effect of different curves and motors, summarize the rules, and see if the effect of adjusting the parameters is better or if the parameters are adjusted smaller. After determining the direction, adjust back to the original parameter, and then gradually increase or decrease the parameter until the parameter with the best effect is recalled.

Figure 3- 15

Figure 3- 16

From the above figure, it can be seen that the smoothness of the curve at the end section reduces the slow uniform speed, but the fluctuation at the end section is still a bit large. At this time, you need to adjust the P2-3 parameter again.

Adjust P2-3 parameters

After adjusting the P2-2 parameters. You can adjust the P2-3 parameter according to the speed loop integral time constant; the smaller the value, the faster the response.

Figure 3- 17

Figure 3- 18

After adjusting the two parameters of P2-2 and P2-3, you can see that the curve has been significantly improved. In addition, depending on the actual action, finally increase the p2-1 position loop gain so that the motor can stop more quickly, but If the adjustment is too large, it is easy to overshoot.

Servo can not stop and rotate back some position

Problem analysis

This servo uses position mode.Because the tension of  belt moves the motor backwards,and the motor runs out of the correct position.So servo drive will control motor rotate back.

Solution

1. Try to add the P2-1 for example P2-1=40.0 .User can set to 80.0
2. If P2-1 still can not solve problem.User can try to add P3-2 For example,P3-2=14.User can set to 16,18 ...But please make sure motor do not have noise
3. If user want to save the P2-1 and P3-2 parameter after restart servo.Please set P3-3=1 

WECON PLC DVIT to control the Servo stop

Problem analysis

This servo uses position mode.WECON PLC will control servo stop with DVIT.The sersor will check the stop signal,then PLC will receive sensor signal and stop with a setting pulse number.But in different speed,the stop position is different.

The most possible reason is the servo position control can not follow by PLC in time.

Solution

After taking many trials, found that Using VD2 and changing the position loop gain, I got a result in position at different speed. I suggest client to check with his existing machine. Below parameter i changed and i got good result in position.

P2-01 = 310.0

P2-02 = 20.0

Power calculation of WECON servo brake resistor

Power calculation of WECON servo brake resistor V1.05

Servo motor selection calculation

Servo motor selection calculation