Verifying the Maximum Position Value of the Machine Encoder

Description

Each machine encoder with the interface EnDat 2.2, BISS, or SSI has to be verified whether the maximum position value of the machine encoder exceeds the maximum positioning value of the drive.

The maximum position value of the machine encoder depends on two factors:

oThe resolution of the machine encoder

oThe ratio between the motor encoder and machine encoder

A formula can be used to calculate the maximum position value of the machine encoder.

If the maximum position value of the machine encoder exceeds the maximum positioning value of the drive you can ether change mechanical components (for example, use of a machine encoder with a lower resolution or use of a mechanical gear box with a lower ratio) or you can limit the resolution of the machine encoder via a parameter.

Calculating the Maximum Position Value

The maximum position value of the machine encoder can be calculated using the following formula. The result must be lower or equal to 2147483647.

Meaning of RESOBITS:

Interface	Value for RESOBITS
Rotary EnDat 2.2	Number of the bits of the singleturn resolution plus number of the bits of the multiturn resolution (see the technical data of the encoder for the values)⁽¹⁾
Linear EnDat 2.2	Number of the bits of the position resolution (see the technical data of the encoder for the values)
Rotary BISS	Number of the bits of the singleturn resolution (same as parameter ENCDigBISSResSgl) plus number of the bits of the multiturn resolution (same as parameter ENCDigBISSResMul)⁽¹⁾
Rotary SSI	Number of the bits of the singleturn resolution (same as parameter ENCDigSSIResSgl) plus number of the bits of the multiturn resolution (same as parameter ENCDigSSIResMult)⁽¹⁾
Linear SSI	Number of the bits of the position resolution (same as parameter ENCDigSSILinRes)
(1) In case of singleturn encoder, the value for the bits of the multiturn resolution is 0.

If the maximum position value of the machine encoder exceeds the maximum positioning value of the drive and if the mechanical components cannot be changed, then you can limit the resolution of the machine encoder via a parameter.

NOTE: Limiting the resolution of the machine encoder considerably reduces the mechanical movement range.

Limiting the Resolution of the Machine Encoder

For rotary encoders, the resolution of the machine encoder can be limited by specifying the number of bits used for the multiturn resolution via parameter ENCDigResMulUsed.

Parameter name HMI menu HMI name	Description	Unit Minimum value Factory setting Maximum value	Data type R/W Persistent Expert	Parameter address via fieldbus
ENCDigResMulUsed	Number of bits of the multiturn resolution used from the encoder. Specifies the number of bits of the multiturn resolution used for position evaluation. If ENCDigResMulUsed = 0, all bits of the multiturn resolution of the encoder are used. Example: If ENCDigResMulUsed = 11, only 11 bits of the multiturn resolution of the encoder are used. Type: Unsigned decimal - 2 bytes Write access via Sercos: CP2, CP3, CP4 Setting can only be modified if power stage is disabled. Modified settings become effective after the next power cycle.	bit 0 0 24	UINT16 R/W per. -	Modbus 21014 IDN P-0-3082.0.11

Parameter name

HMI menu

HMI name

Description

Unit

Minimum value

Factory setting

Maximum value

Data type

R/W

Persistent

Expert

Parameter address via fieldbus

ENCDigResMulUsed

Number of bits of the multiturn resolution used from the encoder.

Specifies the number of bits of the multiturn resolution used for position evaluation.

If ENCDigResMulUsed = 0, all bits of the multiturn resolution of the encoder are used.

Example:

If ENCDigResMulUsed = 11, only 11 bits of the multiturn resolution of the encoder are used.

Type: Unsigned decimal - 2 bytes

Write access via Sercos: CP2, CP3, CP4

Setting can only be modified if power stage is disabled.

Modified settings become effective after the next power cycle.

bit

UINT16

R/W

per.

Modbus 21014

IDN P-0-3082.0.11

For linear encoders, the resolution of the machine encoder can be limited by specifying the number of bits used for the position resolution via parameter ENCDigLinBitsUsed.

Parameter name HMI menu HMI name	Description	Unit Minimum value Factory setting Maximum value	Data type R/W Persistent Expert	Parameter address via fieldbus
ENCDigLinBitsUsed	Linear encoder: Number of bits of the position resolution used. Specifies the number of bits of the position resolution used for position evaluation. If ENCDigLinBitsUsed = 0, all position bits of the position resolution of the encoder are used. Example: If ENCDigLinBitsUsed = 22, only 22 bits of the position resolution of the encoder are used. Type: Unsigned decimal - 2 bytes Write access via Sercos: CP2, CP3, CP4 Setting can only be modified if power stage is disabled. Modified settings become effective after the next power cycle. Available with firmware version ≥V01.06.	bit 0 0 31	UINT16 R/W per. -	Modbus 21020 IDN P-0-3082.0.14

Parameter name

HMI menu

HMI name

Description

Unit

Minimum value

Factory setting

Maximum value

Data type

R/W

Persistent

Expert

Parameter address via fieldbus

ENCDigLinBitsUsed

Linear encoder: Number of bits of the position resolution used.

Specifies the number of bits of the position resolution used for position evaluation.

If ENCDigLinBitsUsed = 0, all position bits of the position resolution of the encoder are used.

Example:

If ENCDigLinBitsUsed = 22, only 22 bits of the position resolution of the encoder are used.

Type: Unsigned decimal - 2 bytes

Write access via Sercos: CP2, CP3, CP4

Setting can only be modified if power stage is disabled.

Modified settings become effective after the next power cycle.

Available with firmware version ≥V01.06.

bit

UINT16

R/W

per.

Modbus 21020

IDN P-0-3082.0.14

Examples for Rotary Encoders

Example 1:

oResolution singleturn bits: 17 bits

oResolution multiturn bits: 12 bits

oMechanical gear box: None

oParameter ResolENC2Num: 131072

oParameter ResolENC2Denom: 1

2^(17+12) x (1/131072) x 131072 = 536870912

536870912 is less than 2147483647 -> Ok. No limitation of the resolution necessary.

Example 2:

oResolution singleturn bits: 17 bits

oResolution multiturn bits: 12 bits

oMechanical gear box: 3:1

oParameter ResolENC2Num: 131072

oParameter ResolENC2Denom: 3

2^(17+12) x (3/131072) x 131072 = 1610612736

1610612736 is less than 2147483647 -> Ok. No limitation of the resolution necessary.

Example 3:

oResolution singleturn bits: 17 bits

oResolution multiturn bits: 12 bits

oMechanical gear box: 5:1

oParameter ResolENC2Num: 131072

oParameter ResolENC2Denom: 5

2^(17+12) x (5/131072) x 131072 = 2684354560

2684354560 is greater than 2147483647 -> Not ok. Change mechanical components (for example a machine encoder with a lower resolution or use of a mechanical gear box with a lower ratio) or limit the resolution of the machine encoder via the parameter ENCDigResMulUsed.

Limitation of the resolution of the machine encoder:

oParameter ENCDigResMulUsed: 11

2^(17+11) x (5/131072) x 131072 = 1342177280

1342177280 is less than 2147483647 -> Ok.

Examples for Linear Encoders

Example 1:

oResolution bits: 20 bits

o10 motor revolutions correspond to 3000 encoder increments

oParameter ResolENC2Num: 3000

oParameter ResolENC2Denom: 10

2²⁰ x (10/3000) x 131072 = 458129845

458129845 is less than 2147483647 -> Ok. No limitation of the resolution necessary.

Example 2:

oResolution bits: 24 bits

o10 motor revolutions correspond to 6702 encoder increments

oParameter ResolENC2Num: 6702

oParameter ResolENC2Denom: 10

2²⁴ x (10/6702) x 131072 = 3281144816

3281144816 is greater than 2147483647 -> Not ok. Change mechanical components (for example a machine encoder with a lower resolution or use of a mechanical gear box with a lower ratio) or limit the resolution of the machine encoder via the parameter ENCDigLinBitsUsed.

Limitation of the resolution of the machine encoder:

oParameter ENCDigLinBitsUsed: 23

2²³ x (10/6702) x 131072 = 1640572408

1640572408 is less than 2147483647 -> Ok.