ini_homing.lyx

CNC 的开放码,EMC2 V2.2.8版

#LyX 1.3 created this file. For more info see http://www.lyx.org/
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\language english
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\layout Section

Homing
\begin_inset LatexCommand \label{sec:Homing}

\end_inset 


\layout Subsection

Overview
\layout Standard

Homing seems simple enough - just move each joint to a known location, and
 set EMC's internal variables accordingly.
 However, different machines have different requirements, and homing can
 be quite complicated.
 When specifying the direction of travel for the axis by using a positive
 or negative number for SEARCH_VEL and LATCH_VEL the machine will move in
 the same direction as when you do a + or - jog in manual control.
 For example if you press the + key to move toward your home switch and
 you have a typical configuration then both SEARCH_VEL and LATCH_VEL will
 be positive numbers for that axis.
\layout Subsection

Homing Sequence
\begin_inset LatexCommand \index{Homing Sequence}

\end_inset 


\layout Standard

In figure 
\begin_inset LatexCommand \ref{fig:Typical-Homing-Sequence}

\end_inset 

 you can see the sequence of a typical homing scenario when both SEARCH_VEL
 and LATCH_VEL are the same sign (positive or negative number).
 Notice that typical switches will have two different points where the switch
 will change states the 
\begin_inset Quotes eld
\end_inset 

tripped
\begin_inset Quotes erd
\end_inset 

 point and the 
\begin_inset Quotes eld
\end_inset 

reset
\begin_inset Quotes erd
\end_inset 

 point.
 Normally you have to travel past the reset point to get to the trip point
 and you have to travel past the tripped point to reach the reset point.
\layout Standard


\begin_inset Float figure
placement H
wide false
collapsed false

\layout Caption

Typical Homing Sequence
\begin_inset LatexCommand \label{fig:Typical-Homing-Sequence}

\end_inset 


\layout Standard
\align center 

\begin_inset Graphics
	filename images/HomingTyp.jpg
	scale 70

\end_inset 


\end_inset 


\layout Enumerate

The axis moves toward the home switch at search velocity as defined by SEARCH_VE
L in the [AXIS_n] section of the ini file.
 Usually there is some overshoot as depicted in the figure.
 Search velocity is usually fast enough so you won't fall asleep waiting
 for the axis to traverse from one side to the other, but not so fast that
 damage could be done.
\layout Enumerate

The axis moves in the reverse direction until the home switch changes state
 (off to on or on to off) plus a little to clear the switch.
\layout Enumerate

The axis moves toward the home switch at latch velocity as defined by LATCH_VEL
 in the [AXIS_n] section of the ini file.
 Usually this is at a much lower speed than search velocity to get a more
 accurate position.
 When the switch changes state if a home offset is defined it is applied.
\layout Enumerate

The axis moves to the home position.
 Usually the home location is not at the switch to prevent false tripping
 of the switch.
\layout Standard

Figure 
\begin_inset LatexCommand \ref{fig:motion-homing-sequence-diagram}

\end_inset 

 shows four possible homing sequences, along with the associated configuration
 parameters.
 For a more detailed description of what each configuration parameter does,
 see the following section.
\layout Standard


\begin_inset Float figure
placement H
wide false
collapsed false

\layout Caption


\begin_inset LatexCommand \label{fig:motion-homing-sequence-diagram}

\end_inset 

Homing Sequences
\layout Standard
\align center 

\begin_inset Graphics
	filename emc2-motion-homing-diag.eps
	scale 70

\end_inset 


\end_inset 


\layout Subsection

Homing Configuration
\begin_inset LatexCommand \index{Homing Configuration}

\end_inset 


\layout Standard

There are six pieces of information that determine exactly how the home
 sequence behaves.
 They are defined in an [AXIS] section of the ini file.
\layout Standard


\begin_inset Float table
placement H
wide false
collapsed false

\layout Standard
\align center 

\begin_inset  Tabular
<lyxtabular version="3" rows="6" columns="4">
<features>
<column alignment="center" valignment="top" leftline="true" width="0">
<column alignment="center" valignment="top" leftline="true" width="0">
<column alignment="center" valignment="top" leftline="true" width="0">
<column alignment="center" valignment="top" leftline="true" rightline="true" width="0">
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

SEARCH_VEL
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

LATCH_VEL
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

USE_INDEX
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard

Homing Type
\end_inset 
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

nonzero
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

nonzero
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

NO
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard

Switch-only
\end_inset 
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

nonzero
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

nonzero
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

YES
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard

Switch + Index
\end_inset 
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

0
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

nonzero
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

YES
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard

Index-only
\end_inset 
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

0
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

0
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

NO
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard

None
\end_inset 
</cell>
</row>
<row topline="true" bottomline="true">
<cell multicolumn="1" alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

Other combinations
\end_inset 
</cell>
<cell multicolumn="2" alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

\end_inset 
</cell>
<cell multicolumn="2" alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text

\layout Standard

\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard

Error
\end_inset 
</cell>
</row>
</lyxtabular>

\end_inset 


\layout Caption


\begin_inset LatexCommand \label{cap:Homing-Sequences}

\end_inset 

Homing Types
\end_inset 


\layout Subsubsection

HOME_SEARCH_VEL
\begin_inset LatexCommand \index{HOME SEARCH VEL}

\end_inset 


\layout Standard

The default value is zero.
 A value of zero causes EMC to assume that there is no home switch; the
 search stage of homing is skipped.
 
\layout Standard

If HOME_SEARCH_VEL is non-zero, then EMC assumes that there is a home switch.
 It begins by checking whether the home switch is already tripped.
 If so, it backs off the switch at HOME_SEARCH_VEL (the direction of the
 back-off is opposite the sign of HOME_SEARCH_VEL).
 Then it searches for the home switch by moving in the direction specified
 by the sign of 'HOME_SEARCH_VEL', at a speed determined by its absolute
 value.
 When the home switch is detected, the joint will stop as fast as possible,
 but there will always be some overshoot.
 The amount of overshoot depends on the speed.
 If it is too high, the joint might overshoot enough to hit a limit switch
 or crash into the end of travel.
 On the other hand, if 'HOME_SEARCH_VEL' is too low, homing can take a long
 time.
\layout Subsubsection

HOME_LATCH_VEL
\begin_inset LatexCommand \index{HOME LATCH VEL}

\end_inset 


\layout Standard

Specifies the speed and direction that EMC uses when it makes its final
 accurate determination of the home switch (if present) and index pulse
 location (if present).
 It will usually be slower than the search velocity to maximise accuracy.
 If HOME_SEARCH_VEL and HOME_LATCH_VEL have the same sign, then the latch
 phase is done while moving in the same direction as the search phase.
 (In that case, EMC first backs off the switch, before moving towards it
 again at the latch velocity.) If HOME_SEARCH_VEL and HOME_LATCH_VEL have
 opposite signs, the latch phase is done while moving in the opposite direction
 from the search phase.
 That means EMC will latch the first pulse after it moves off the switch.
 If 'HOME_SEARCH_VEL' is zero (meaning there is no home switch), and this
 parameter is nonzero, EMC goes ahead to the index pulse search.
 If 'HOME_SEARCH_VEL' is non-zero and this parameter is zero, it is an error
 and the homing operation will fail.
 The default value is zero.
\layout Subsubsection

HOME_IGNORE_LIMITS
\begin_inset LatexCommand \index{HOME IGNORE LIMITS}

\end_inset 


\layout Standard

Can hold the values YES / NO.
 This flag determines whether EMC will ignore the limit switch inputs.
 Some machine configurations do not use a separate home switch, instead
 they route one of the limit switch signals to the home switch input as
 well.
 In this case, EMC needs to ignore that limit during homing.
 The default value for this parameter is NO.
\layout Subsubsection

HOME_USE_INDEX
\begin_inset LatexCommand \index{HOME USE INDEX}

\end_inset 


\layout Standard

Specifies whether or not there is an index pulse.
 If the flag is true (HOME_USE_INDEX = YES), EMC will latch on the rising
 edge of the index pulse.
 If false, EMC will latch on either the rising or falling edge of the home
 switch (depending on the signs of 'HOME_SEARCH_VEL' and 'HOME_LATCH_VEL').
 The default value is NO.
\layout Subsubsection

HOME_OFFSET
\begin_inset LatexCommand \index{HOME OFFSET}

\end_inset 


\layout Standard

Contains the location of the home switch or index pulse, in joint coordinates.
 It can also be treated as the distance between the point where the switch
 or index pulse is latched and the zero point of the joint.
 After detecting the index pulse, EMC sets the joint coordinate of the current
 point to 
\begin_inset Quotes eld
\end_inset 

HOME_OFFSET
\begin_inset Quotes erd
\end_inset 

.
 The default value is zero.
\layout Subsubsection

HOME
\begin_inset LatexCommand \index{HOME}

\end_inset 


\layout Standard

The position that the joint will go to upon completion of the homing sequence.
 After detecting the index pulse, and setting the coordinate of that point
 to 
\begin_inset Quotes eld
\end_inset 

HOME_OFFSET
\begin_inset Quotes erd
\end_inset 

, EMC makes a move to "HOME" as the final step of the homing process.
 The default value is zero.
 Note that even if this parameter is the same as 
\begin_inset Quotes eld
\end_inset 

HOME_OFFSET
\begin_inset Quotes erd
\end_inset 

, the axis will slightly overshoot the latched position as it stops.
 Therefore there will always be a small move at this time (unless HOME_SEARCH_VE
L is zero, and the entire search/latch stage was skipped).
 This final move will be made at the joint's maximum velocity.
 Since the axis is now homed, there should be no risk of crashing the machine,
 and a rapid move is the quickest way to finish the homing sequence.
\layout Standard


\begin_inset Note
collapsed false

\layout Standard

The distinction between 'home' and 'home_offset' is not as clear as I would
 like.
 I intend to make a small drawing and example to help clarify it.
\end_inset 


\layout Subsubsection

HOME_IS_SHARED
\begin_inset LatexCommand \index{HOME IS SHARED}

\end_inset 


\layout Standard

If there is not a separate home switch input for this axis, but a number
 of momentary switches wired to the same pin, set this value to 1 to prevent
 homing from starting if one of the shared switches is already closed.
 Set this value to 0 to permit homing even if the switch is already closed.
\layout Subsubsection

HOME_SEQUENCE
\begin_inset LatexCommand \index{HOME SEQUENCE}

\end_inset 


\layout Standard

Used to define a multi-axis homing sequence (
\begin_inset Quotes eld
\end_inset 

HOME ALL
\begin_inset Quotes erd
\end_inset 

) and enforce homing order (e.g., Z may not be homed if X is not yet homed).
 An axis may be homed after all axes with a lower HOME_SEQUENCE have already
 been homed and are at the HOME_OFFSET.
 If two axes have the same HOME_SEQUENCE, they may be homed at the same
 time.
 If HOME_SEQUENCE is -1 or not specified then this joint will not be homed
 by the HOME ALL sequence.
 HOME_SEQUENCE numbers start with 0 and there may be no unused numbers.
\layout Standard


\begin_inset Note
collapsed false

\layout Standard

is a 
\backslash 
clearpage needed for some reason? JT
\end_inset 


\layout Standard


\begin_inset ERT
status Collapsed

\layout Standard

\backslash 
clearpage
\end_inset 


\the_end