Setting the Ratio Between Machine Encoder and Motor Encoder
The ratio between the machine encoder and the motor encoder adjusts the machine encoder to the internal units of the drive.
Definition of the ratio:
oA specific number of Encoder increments ResolENC2Num correspond to a specific number of motor revolutions ResolENC2Denom.
This can be determined either by calculation or by measuring.
Calculating the Ratio for Rotary Encoders
Formula for calculation of the ratio:
|
Item |
Meaning |
|---|---|
|
EncIncOneRev |
Number of encoder increments of one revolution of the machine encoder. For the definition of encoder increments see chapter Definition of Encoder Increments. |
|
MechGearDenom(1) |
Denominator of the mechanical gear. Example: Value 2, if a mechanical gear with a ratio of 5:2 is used. |
|
MechGearNum(1) |
Numerator of the mechanical gear. Example: Value 5, if a mechanical gear with a ratio of 5:2 is used. |
|
AnaDig |
For analog encoders: Value 4 For digital encoders: Value 1 |
|
1 If a mechanical gear is used. |
|
Examples:
|
Type of encoder |
Mechanical gear |
Result |
|---|---|---|
|
Analog encoder Resolution: 20000 encoder increments (5000 periods/lines) per revolution of the machine encoder |
None |
ResolENC2Num: 20000 x 1 x 1 = 20000 ResolENC2Denom: 1 x 1 x 4 = 4 |
|
Ratio 5:2 |
ResolENC2Num: 20000 x 2 x 1 = 40000 ResolENC2Denom: 1 x 5 x 4 = 20 |
|
|
Digital encoder ABI Resolution: 20000 encoder increments (5000 periods/lines) per revolution of the machine encoder |
None |
ResolENC2Num: 20000 x 1 x 1 = 20000 ResolENC2Denom: 1 x 1 x 1 = 1 |
|
Ratio 5:2 |
ResolENC2Num: 20000 x 2 x 1 = 40000 ResolENC2Denom: 1 x 5 x 1 = 5 |
|
|
Digital encoder EnDat 2.2, BISS or SSI Resolution: 8192 encoder increments (13 bits) per revolution of the machine encoder |
None |
ResolENC2Num: 8192 x 1 x 1 = 8192 ResolENC2Denom: 1 x 1 x 1 = 1 |
|
Ratio 5:2 |
ResolENC2Num: 8192 x 2 x 1 = 16384 ResolENC2Denom: 1 x 5 x 1 = 5 |
Calculating the Ratio for Linear Encoders
Formula for calculation of the ratio:
|
Item |
Meaning |
|---|---|
|
Feed |
The feed of the linear axis with one revolution of the input shaft. Use the same unit as for “Resol”. |
|
Resol |
The resolution of the machine encoder corresponding to 1 encoder increment. Use the same unit as for “Feed”. For the definition of encoder increments see chapter Definition of Encoder Increments. |
|
MechGearDenom(1) |
Denominator of the mechanical gear. Example: Value 3, if a mechanical gear with a ratio of 7:3 is used. |
|
MechGearNum(1) |
Numerator of the mechanical gear. Example: Value 7, if a mechanical gear with a ratio of 7:3 is used. |
|
AnaDig |
For analog encoders: Value 4 For digital encoders: Value 1 |
|
1 If a mechanical gear is used. |
|
Examples:
|
Type of encoder |
Feed of the linear axis |
Mechanical gear |
Result |
|---|---|---|---|
|
Analog encoder Resolution: 1 periods/lines correspond to 0.02 mm, therefore 1 encoder increment correspond to 0.005 mm |
One revolution of the input shaft correspond to 155 mm |
None |
ResolENC2Num: (155/0.005) x 1 x 1 = 31000 ResolENC2Denom: 1 x 1 x 4 = 4 |
|
Ratio 7:3 |
ResolENC2Num: (155/0.005) x 3 x 1 = 93000 ResolENC2Denom: 1 x 7 x 4 = 28 |
||
|
Digital encoder ABI Resolution: 1 periods/lines correspond to 0.02 mm, therefore 1 encoder increment correspond to 0.005 mm |
One revolution of the input shaft correspond to 155 mm |
None |
ResolENC2Num: (155/0.005) x 1 x 1 = 31000 ResolENC2Denom: 1 x 1 x 1 = 1 |
|
Ratio 7:3 |
ResolENC2Num: (155/0.005) x 3 x 1 = 93000 ResolENC2Denom: 1 x 7 x 1 = 7 |
||
|
Digital encoder EnDat 2.2 or SSI Resolution: 1 encoder increment (1 bit) correspond to 0.005 mm |
One revolution of the input shaft correspond to 155 mm |
None |
ResolENC2Num: (155/0.005) x 1 x 1 = 31000 ResolENC2Denom: 1 x 1 x 1 = 1 |
|
Ratio 7:3 |
ResolENC2Num: (155/0.005) x 3 x 1 = 93000 ResolENC2Denom: 1 x 7 x 1 = 7 |
Measuring the Ratio (Alternative)
Procedure:
|
Step |
Action |
|---|---|
|
1 |
Set the parameter ENC_ModeOfMaEnc to the value 0 to keep the motor from being controlled during the procedure. |
|
2 |
Read the value of the parameter _Inc_ENC2Raw using the commissioning software. |
|
3 |
Move the motor shaft by exactly one revolution in positive direction using the commissioning software. |
|
4 |
Calculate the difference between _Inc_ENC2Raw before and after the revolution of the motor. |
|
5 |
Set the value of the parameter ResolENC2Num to the difference calculated. |
|
6 |
Set the parameter ResolENC2Denom to: oFor analog encoders: Value 4 oFor digital encoders: Value 1 |
|
7 |
Reset the parameter ENC_ModeOfMaEnc to the original value. |
|
Parameter name HMI menu HMI name |
Description |
Unit Minimum value Factory setting Maximum value |
Data type R/W Persistent Expert |
Parameter address via fieldbus |
|---|---|---|---|---|
|
Raw increment value of encoder 2. This parameter is only needed for commissioning of encoder 2 in case of an unknown machine encoder resolution. Type: Signed decimal - 4 bytes |
EncInc - - - |
INT32 R/- - - |
Modbus 7754 IDN P-0-3030.0.37 |
|
Parameter name HMI menu HMI name |
Description |
Unit Minimum value Factory setting Maximum value |
Data type R/W Persistent Expert |
Parameter address via fieldbus |
|---|---|---|---|---|
|
Resolution of encoder 2, numerator. Digital encoders: Specification of the encoder increments the external encoder returns for one or several revolutions of the motor shaft. The value is indicated with a numerator and a denominator so that it is possible, for example, to take into account the gear ratio of a mechanical gearing. The value must not be set to 0.
The resolution factor is not applied until this numerator value is specified.
Example: One motor revolution causes 1/3 encoder revolution at an encoder resolution of 16384 EncInc/revolution.
ResolENC2Num = 16384 EncInc ResolENC2Denom = 3 revolutions
Analog encoders: Num/Denom must be set equivalent to the number of analog periods per 1 motor revolution.
Example: One motor revolution causes 1/3 encoder revolution at an encoder resolution of 16 analog periods per revolution.
ResolENC2Num = 16 periods ResolENC2Denom = 3 revolutions Type: Signed decimal - 4 bytes Write access via Sercos: CP2, CP3, CP4 Setting can only be modified if power stage is disabled. Modified settings become effective the next time the power stage is enabled. |
EncInc 1 10000 2147483647 |
INT32 R/W per. - |
Modbus 20492 IDN P-0-3080.0.6 |
|
|
Resolution of encoder 2, denominator. See numerator (ResolEnc2Num) for a description. Type: Signed decimal - 4 bytes Write access via Sercos: CP2, CP3, CP4 Setting can only be modified if power stage is disabled. Modified settings become effective the next time the power stage is enabled. |
revolution 1 1 16383 |
INT32 R/W per. - |
Modbus 20490 IDN P-0-3080.0.5 |
Setting the Maximum Deviation Between Motor Encoder and Machine Encoder
The Maximum Deviation Between Motor Encoder and Machine Encoder can be set via the parameter p_MaxDifToENC2.
|
Parameter name HMI menu HMI name |
Description |
Unit Minimum value Factory setting Maximum value |
Data type R/W Persistent Expert |
Parameter address via fieldbus |
|---|---|---|---|---|
|
Maximum permissible deviation of encoder positions. The maximum permissible position deviation between the encoder positions is cyclically monitored. If the limit is exceeded, an error is detected. The position deviation is available via the parameter '_p_DifEnc1ToEnc2'. The default value corresponds to 1/2 motor revolution. The maximum value corresponds to 100 motor revolutions. Type: Signed decimal - 4 bytes Write access via Sercos: CP2, CP3, CP4 Setting can only be modified if power stage is disabled. Modified settings become effective the next time the power stage is enabled. |
Inc 1 65536 13107200 |
INT32 R/W per. - |
Modbus 20494 IDN P-0-3080.0.7 |
