Bosch 6000 User's Guide download pdf (Page 208)

Chapter 6. Following

193

Performance Considerations

(see also page 33)

Position Sampling Period

Steppers – 2 milliseconds.

Servos –

system update

period

(depends on SSFR

and INDAX command

values – see SSFR

command description).

When a slave is following a master, the 6000 controller does not simply measure the master

velocity to derive slave velocity. Instead, the 6000 controller samples the master position

(position sampling period) and calculates the corresponding slave position command. This is true

even if the slave is in the process of changing ratios. A slave is not simply following velocity,

but rather position. With this algorithm, the master and slave position or phase relationship is

maintained indefinitely, without any drift over time due to velocity measurement errors.

The 6000 controller also measures master velocity by measuring the change in master position

over a number of sample periods. The present master velocity and position may be used to

calculate the next commanded slave position, so the slave has no velocity-dependent phase

delay. This concept is known as Master Position Prediction and may be enabled or disabled as

needed with the FPPEN command.

GREATER DETAIL ...

on the technical aspects of

Following can be found on

page 213, or in the

associated command

descriptions in the

6000

Series Software Reference

The 6000 controller's default Following algorithm should work well for most applications;

however, you can change the Following algorithm to meet application-specific needs. For

instance, suppose that the speed of the master is very slow, or has some vibration. For a case

like this, the 6000 controller allows you to filter the master position signal to generate a

smooth slave position command. This is known as Master Position Filtering and is

programmed with the FFILT command.

Following Status (TFSF, TFS & FS Commands)

Many of the Following features described in this document have

associated status bits that can be displayed (with the TFSF and TFS

commands) or used in assignment or comparison operations (with

the FS operator). The portions of this document which describe

those features also summarize the related status bits.

TFS bit response format:

*TFS bbbb_bbbb_bbbb_bbbb_bb ← Axis 1

* bbbb_bbbb_bbbb_bbbb_bb ← Axis 2

* bbbb_bbbb_bbbb_bbbb_bb ← Axis 3

* bbbb_bbbb_bbbb_bbbb_bb ← Axis 4

^ ^

Bit #1 Bit #18

Bit Function (YES = 1; NO = Ø)

1......... Slave in Ratio Move ........ A Following move is in progress.

2......... Ratio is Negative ............. The current ratio is negative (i.e., slave counts counting in the opposite direction from master).

3......... Slave Ratio Changing ..... The slave is ramping from one ratio to another (including a ramp to or from zero ratio).

4......... Slave At Ratio .................. The slave is at constant non-zero ratio.

Bits 1-4 indicate the status of slave Following motion.

* 5......... FOLMAS Active ............... A master is specified with the FOLMAS command.

* 6......... FOLEN Active.................. Following has been enabled with the FOLEN command.

* 7......... Master is Moving ............ The specified master is currently in motion.

8......... Master Dir Neg ............... The current master direction is negative. (Bit must be cleared to allow Following move in preset mode—MCØ).

Bits 5-8 indicate the status required for Following motion (i.e., a master must be assigned, Following must be enabled, the

master must be moving, and for many features, the master direction must be positive).

Unless the master is a commanded position of another axis, minor vibration of the master will likely cause bits 7-8 to toggle

on and off, even if the master is nominally “at rest”. These bits are meant primarily as a quick diagnosis for the absence of

master motion, or master motion in the wrong direction. Many features require positive master counting to work properly.

9......... OK to Shift........................ Conditions are valid to issue shift commands (FSHFD or FSHFC).

10......... Shifting now ..................... A shift move is in progress.

11......... Shift is Continuous .......... An FSHFC-based shift move is in progress.

12......... Shift Dir is Neg................ The direction of the shift move in progress is negative.

Bits 9-12 indicate the shift status of the slave. Shifting is super-imposed motion, but if viewed alone, can have its own status.

In other words, bits 10-12 describe only the shifting portion of motion.

13......... Master Cyc Trig Pend .... A master cycle restart is pending the occurrence of the specified trigger.

14......... Mas Cyc Len Given ........ A non-zero master cycle length has been specified with the FMCLEN command.

15......... Master Cyc Pos Neg ...... The current master cycle position (PMAS) is negative. This could be by caused by a negative initial master

cycle position (FMCP), or if the master is moving in the negative direction.

16......... Master Cyc Num > 0...... The master position (PMAS) has exceeded the master cycle length (FMCLEN) at least once, causing the

master cycle number (NMCY) to increment.

Bits 13-16 indicate the status of master cycle counting. If a Following application is taking advantage of master cycle

counting, these bits provide a quick summary of some important master cycle information.

17......... Mas Pos Prediction On ... Master position prediction has been enabled (FPPEN).

18......... Mas Filtering On ............. A non-zero value for master position filtering (FFILT) is in effect.

Bit 17-18 indicate the status of master position measurement features.

* All these conditions must be true before Following motion will occur.

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Bosch 6000 User's Guide Page 208

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