Corrected from:
Servo-Inverter i950 FW: ab V01.04.01.1471
Response of the new version:
Within the firmware of the i950, the evaluation procedure for linear SSI absolute encoders (laser distance measurement system, barcode reader) has now been revised and adapted to the special characteristics.
Large differences between the transmitted raw values from the SSI encoder are correctly recorded and processed now.
There is no loss of position information and the reference position is not lost.
Using the newly implemented parameters (0x2C4A:20, 0x2C5A:20), a distinction is now made for motor encoders and load encoders between rotary encoders and linear encoder systems:
SlotA (Motor) Absolute value encoder SSI: 0x2C4A:20 = 0: Rotary encoder (Lenze setting)
= 1: Linear encoder
SlotB (Appl.) Absolute value encoder SSI: 0x2C5A:20 = 0: Rotary encoder (Lenze setting)
= 1: Linear encoder
In Lenze setting (rotary encoder), the drive controller behaves as before.
The SSI encoder evaluation is adapted to the peculiarities of linear SSI encoder systems only after conversion to "linear encoder".
The scaled actual positions are displayed with rotary and linear encoders:
- 0x2C4A:21: Motor encoder, scaled to 0x608F
- 0x2C5A:21: Load transmitter, scaled to 0x60E6
Hint:
The function for shifting the actual position within the drive controller is no longer available with the new evaluation method.
In practice, this is not important, since the reference position is normally shifted via the functionality in the superimposed PLC application.
What happens?
The actual position assumes incorrect values due to a loss of position information.
The effect on the machine is equivalent to the loss of the reference position.
When does the behaviour occur?
When using linear SSI absolute encoders (laser distance measuring system, barcode reader). Rotative SSI absolute encoders are not affected.
A loss of position information can occur if two raw values successively transmitted by the linear SSI encoder system show a very large position difference, whereby the difference is significantly larger than would be physically possible with a real movement.
Such large position differences can only be caused by a malfunction of the SSI encoder system (beam interruption, barcode failure) or occur during initialization after switch-on.
The occurrence of very large position differences is a peculiarity of linear SSI encoder systems.
Which products are affected?
Servo-Inverter i950 FW
Short-term measures / Evaluation / Recommendations:
In the meanwhile the new i950 firmware version within the correction of the function restriction is available. It will be recommendet to use this new FW version in case of the problem occurrs.
The remedy descriced below is not needed anymore.
The remedy described below is only for bridging the time until the new i950 firmware version is available:
i950 (BS-STO) - TA Cia-Advanced:
- 0x2C5A:003 Load encoder resolution: 26 [bits/rev] | = at least SSI data width + 1 bit
- 0x60E6:001 Load encoder line count: 26 bit == 67108864 inc/rev
- 0x500E:032 Encoder feed constant: 67108864 inc/rev (== 26 bits)
- Position resolution in the application: unchanged, as before, e.g.: 65536 [inc/rev]
i950 (BS-STO) - TA Table Positioning:
- 0x2C5A:003 Load encoder resolution: 26 [bits/rev] | = at least SSI data width + 1 bit
- 0x60E6:001 Load encoder line count: 26 bit == 67108864 inc/rev
- 0x500B:032 Feed constant: 6710,8864 Units/rev (== 26 bits/10000)
- 0x500B:033 i-gear counter: (Value as before)
- 0x500B:034 i-gear denominator: (value as before) * 10000
- Position resolution in the application: unchanged, as before, e.g.: 65536 [inc/rev]
Background:
In practice, very large position differences can only occur with linear encoder systems, e.g. with a laser distance measuring system after a beam interruption or with a barcode reader after a barcode failure. With rotary encoder systems such large position differences between two consecutive raw values will not occur.
Position differences in the range of +/- half a motor revolution can be processed error-free by the i950. With larger values, information is inevitably lost and an incorrect actual position is formed.
Until now, the parameterization of the SSI interface has been tailored to rotary encoder systems. Therefore, the input "bits/revolution" with reference to one motor revolution is necessary.
With a linear encoder system, this setting can in principle be freely selected. Adapting the load encoder resolution to (SSI data width + 1 bit) causes the entire display range of the SSI encoder i950 to be projected internally to half a motor revolution and the actual position to be formed error-free.
The load transmitter line count cannot be set to 25 bits, therefore the next higher adjustable value is selected. For 24 bit data width, 26 bit.
Automatic Translation
