rtcomps.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/
\lyxformat 221
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\end_preamble
\language english
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\quotes_language english
\quotes_times 2
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\layout Chapter


\begin_inset LatexCommand \label{cha:Internal-Components}

\end_inset 

Internal Components
\layout Standard

Most components have unix-style manual pages.
 To view manual pages for real-time components, type 
\begin_inset Quotes eld
\end_inset 

man 9 
\emph on 
componentname
\emph default 

\begin_inset Quotes erd
\end_inset 

 at the terminal prompt.
\layout Standard

This document focuses on more complicated components which have figures
 which are hard to reproduce in the manual page format.
\layout Section


\begin_inset LatexCommand \label{sec:Stepgen}

\end_inset 

Stepgen
\begin_inset LatexCommand \index{stepgen}

\end_inset 


\layout Standard

This component provides software based generation of step pulses in response
 to position or velocity commands.
 In position mode, it has a built in pre-tuned position loop, so PID tuning
 is not required.
 In velocity mode, it drives a motor at the commanded speed, while obeying
 velocity and acceleration limits.
 It is a realtime component only, and depending on CPU speed, etc, is capable
 of maximum step rates of 10kHz to perhaps 50kHz.
 Figure 
\begin_inset LatexCommand \ref{fig:Stepgen-Block-Diag}

\end_inset 

 shows three block diagrams, each is a single step pulse generator.
 The first diagram is for step type '0', (step and direction).
 The second is for step type '1' (up/down, or pseudo-PWM), and the third
 is for step types 2 through 14 (various stepping patterns).
 The first two diagrams show position mode control, and the third one shows
 velocity mode.
 Control mode and step type are set independently, and any combination can
 be selected.
\layout Standard


\begin_inset Float figure
wide false
collapsed false

\layout Standard
\align center 

\begin_inset Graphics
	filename stepgen-block-diag.eps
	width 7.5in
	height 8.5in
	keepAspectRatio
	clip

\end_inset 


\layout Caption


\begin_inset LatexCommand \label{fig:Stepgen-Block-Diag}

\end_inset 

Step Pulse Generator Block Diagram (position mode)
\end_inset 


\layout Standard


\begin_inset Float figure
wide false
collapsed false

\layout Standard
\align center 

\begin_inset Graphics
	filename freqgen-block-diag.eps
	width 7.5in
	height 8.5in
	keepAspectRatio
	clip

\end_inset 


\layout Caption


\begin_inset LatexCommand \label{fig:Freqgen-Block-Diag}

\end_inset 

Step Pulse Generator Block Diagram (velocity mode)
\end_inset 


\layout Subsection

Installing
\layout LyX-Code

emc2$ 
\series bold 
halcmd loadrt stepgen step_type=<type-array> [ctrl_type=<ctrl_array>]
\layout Standard


\family typewriter 
<type-array>
\family default 
 is a series of comma separated decimal integers.
 Each number causes a single step pulse generator to be loaded, the value
 of the number determines the stepping type.
 
\family typewriter 
<ctrl_array>
\family default 
 is a comma separated series of 
\begin_inset Quotes eld
\end_inset 


\family typewriter 
\series bold 
p
\family default 
\series default 

\begin_inset Quotes erd
\end_inset 

 or 
\begin_inset Quotes eld
\end_inset 


\family typewriter 
\series bold 
v
\family default 
\series default 

\begin_inset Quotes erd
\end_inset 

 characters, to specify position or velocity mode.
 
\family typewriter 
\series bold 
ctrl_type
\family default 
\series default 
 is optional, if ommitted, all of the step generators will be position mode.
 For example:
\layout LyX-Code

emc2# 
\series bold 
halcmd loadrt stepgen.o step_type=0,0,2 ctrl_type=p,p,v
\layout Standard

will install three step generators.
 The first two use step type '0' (step and direction) and run in position
 mode.
 The last one uses step type '2' (quadrature) and runs in velocity mode.
 The default value for 
\family typewriter 
<config-array>
\family default 
 is 
\family typewriter 

\begin_inset Quotes eld
\end_inset 

0,0,0
\begin_inset Quotes erd
\end_inset 


\family default 
 which will install three type '0' (step/dir) generators.
 The maximum number of step generators is 8 (as defined by MAX_CHAN in stepgen.c).
 Each generator is independent, but all are updated by the same function(s)
 at the same time.
 In the following descriptions, 
\family typewriter 
<chan>
\family default 
 is the number of a specific generator.
 The first generator is number 0.
\layout Subsection

Removing
\layout LyX-Code

emc2$ 
\series bold 
halcmd unloadrt stepgen
\layout Subsection

Pins
\layout Standard

Each step pulse generator will have only some of these pins, depending on
 the step type and control type selected.
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.position-cmd
\family default 
 -- Desired motor position, in position units (position mode only).
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.velocity-cmd
\family default 
 -- Desired motor velocity, in position units per second (velocity mode
 only).
\layout Itemize


\family typewriter 
\noun on 
(s32) 
\noun default 
stepgen.<chan>.counts
\family default 
 -- Feedback position in counts, updated by 
\family typewriter 
capture_position()
\family default 
.
\layout Itemize


\family typewriter 
\noun on 
(float) 
\noun default 
stepgen.<chan>.position-fb
\family default 
 -- Feedback position in position units, updated by 
\family typewriter 
capture_position()
\family default 
.
\layout Itemize


\family typewriter 
\noun on 
(bit)
\noun default 
 stepgen.<chan>.step
\family default 
 -- Step pulse output (step type 0 only).
\layout Itemize


\family typewriter 
\noun on 
(bit)
\noun default 
 stepgen.<chan>.dir
\family default 
 -- Direction output (step type 0 only).
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
stepgen.<chan>.up
\family default 
 -- UP pseudo-PWM output (step type 1 only).
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
stepgen.<chan>.down
\family default 
 -- DOWN pseudo-PWM output (step type 1 only).
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
stepgen.<chan>.phase-A
\family default 
 -- Phase A output (step types 2-14 only).
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
stepgen.<chan>.phase-B
\family default 
 -- Phase B output (step types 2-14 only).
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
stepgen.<chan>.phase-C
\family default 
 -- Phase C output (step types 3-14 only).
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
stepgen.<chan>.phase-D
\family default 
 -- Phase D output (step types 5-14 only).
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
stepgen.<chan>.phase-E
\family default 
 -- Phase E output (step types 11-14 only).
\layout Subsection

Parameters
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.position-scale
\family default 
 -- Steps per position unit.
 This parameter is used for both output and feedback.
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.maxvel
\family default 
 -- Maximum velocity, in position units per second.
 If 0.0, has no effect.
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.maxaccel
\family default 
 -- Maximum accel/decel rate, in positions units per second squared.
 If 0.0, has no effect.
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.frequency
\family default 
 -- The current step rate, in steps per second.
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.steplen
\family default 
 -- Length of a step pulse (step type 0 and 1) or minimum time in a given
 state (step types 2-14), in nano-seconds.
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.stepspace
\family default 
 -- Minimum spacing between two step pulses (step types 0 and 1 only), in
 nano-seconds.
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.dirsetup
\family default 
 -- Minimum time from a direction change to the beginning of the next step
 pulse (step type 0 only), in nanoseconds.
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.dirhold
\family default 
 -- Minmum time from the end of a step pulse to a direction change (step
 type 0 only), in nanoseconds.
\layout Itemize


\family typewriter 
\noun on 
(float)
\noun default 
 stepgen.<chan>.dirdelay
\family default 
 -- Minmum time any step to a step in the opposite direction (step types
 1-14 only), in nano-seconds.
\layout Itemize


\family typewriter 
\noun on 
(s32)
\noun default 
 stepgen.<chan>.rawcounts
\family default 
 -- The raw feedback count, updated by 
\family typewriter 
make_pulses()
\family default 
.
 
\layout Standard

In position mode, the values of maxvel and maxaccel are used by the internal
 position loop to avoid generating step pulse trains that the motor cannot
 follow.
 When set to values that are appropriate for the motor, even a large instantaneo
us change in commanded position will result in a smooth trapezoidal move
 to the new location.
 The algorithm works by measuring both position error and velocity error,
 and calculating an acceleration that attempts to reduce both to zero at
 the same time.
 For more details, including the contents of the 
\begin_inset Quotes eld
\end_inset 

control equation
\begin_inset Quotes erd
\end_inset 

 box, consult the code.
\layout Standard

In velocity mode, maxvel is a simple limit that is applied to the commanded
 velocity, and maxaccel is used to ramp the actual frequency if the commanded
 velocity changes abruptly.
 As in position mode, proper values for these parameters ensure that the
 motor can follow the generated pulse train.
\layout Subsection


\begin_inset LatexCommand \label{sub:Stepgen-Step-Types}

\end_inset 

Step Types
\layout Standard

The step generator supports 15 different 
\begin_inset Quotes eld
\end_inset 

step types
\begin_inset Quotes erd
\end_inset 

.
 Step type 0 is the most familiar, standard step and direction.
 When configured for step type 0, there are four extra parameters that determine
 the exact timing of the step and direction signals.
 See figure 
\begin_inset LatexCommand \ref{fig:StepDir-timing}

\end_inset 

 for the meaning of these parameters.
 The parameters are in nanoseconds, but will be rounded up to an integer
 multiple of the thread period for the threaed that calls 
\family typewriter 
make_pulses()
\family default 
.
 For example, if 
\family typewriter 
make_pulses()
\family default 
 is called every 16uS, and steplen is 20000, then the step pulses will be
 2 x 16 = 32uS long.
 The default value for all four of the parameters is 1nS, but the automatic
 rounding takes effect the first time the code runs.
 Since one step requires 
\family typewriter 
steplen
\family default 
 nS high and 
\family typewriter 
stepspace
\family default 
 nS low, the maximum frequency is 1,000,000,000 divided by 
\family typewriter 
(steplen+stepspace)
\family default 
.
 If 
\family typewriter 
maxfreq
\family default 
 is set higher than that limit, it will be lowered automatically.
 If maxfreq is zero, it will remain zero, but the output frequency will
 still be limited.
\layout Standard


\begin_inset Float figure
wide false
collapsed false

\layout Standard
\align center 

\begin_inset Graphics
	filename stepgen-type0.eps
	width 7in
	height 4in
	keepAspectRatio

\end_inset 


\layout Caption


\begin_inset LatexCommand \label{fig:StepDir-timing}

\end_inset 

Step and Direction Timing
\end_inset 


\layout Standard

Step type 1 has two outputs, up and down.
 Pulses appear on one or the other, depending on the direction of travel.
 Each pulse is 
\family typewriter 
steplen
\family default 
 nS long, and the pulses are separated by at least 
\family typewriter 
stepspace
\family default 
 nS.
 The maximum frequency is the same as for step type 0.
 If 
\family typewriter 
maxfreq
\family default 
 is set higher than the limit it will be lowered.
 If 
\family typewriter 
maxfreq
\family default 
 is zero, it will remain zero but the output frequency will still be limited.
 
\layout Standard

Step types 2 through 14 are state based, and have from two to five outputs.
 On each step, a state counter is incremented or decremented.
 Figures 
\begin_inset LatexCommand \ref{fig:Quad-Three-Phase}

\end_inset 

, 
\begin_inset LatexCommand \ref{fig:Four-Phase}

\end_inset 

, and 
\begin_inset LatexCommand \ref{fig:Five-Phase}

\end_inset 

 show the output patterns as a function of the state counter.
 The maximum frequency is 1,000,000,000 divided by 
\family typewriter 
steplen
\family default 
, and as in the other modes, 
\family typewriter 
maxfreq
\family default 
 will be lowered if it is above the limit.
\layout Standard


\begin_inset Float figure
wide false
collapsed false

\layout Standard
\align center 

\begin_inset Graphics
	filename stepgen-type2-4.eps
	width 7.5in
	height 8.5in
	keepAspectRatio
	rotateAngle 90

\end_inset 


\layout Caption

Three-Phase step types
\begin_inset LatexCommand \label{fig:Quad-Three-Phase}

\end_inset 


\end_inset 


\layout Standard


\begin_inset Float figure
wide false
collapsed false

\layout Standard
\align center 

\begin_inset Graphics
	filename stepgen-type5-10.eps
	width 7.5in
	height 8.5in
	keepAspectRatio
	rotateAngle 90

\end_inset 


\layout Caption


\begin_inset LatexCommand \label{fig:Four-Phase}

\end_inset 

Four-Phase Step Types
\end_inset 


\layout Standard


\begin_inset Float figure
wide false
collapsed false

\layout Standard
\align center 

\begin_inset Graphics
	filename stepgen-type11-14.eps
	width 7.5in
	height 8.5in
	keepAspectRatio

\end_inset 


\layout Caption


\begin_inset LatexCommand \label{fig:Five-Phase}

\end_inset 

Five-Phase Step Types
\end_inset 


\layout Subsection

Functions
\layout Standard

The component exports three functions.
 Each function acts on all of the step pulse generators - running different
 generators in different threads is not supported.
 
\layout Itemize


\family typewriter 
\noun on 
(funct)
\noun default 
 stepgen.make-pulses
\family default 
 -- High speed function to generate and count pulses (no floating point).
\layout Itemize


\family typewriter 
\noun on 
(funct)
\noun default 
 stepgen.update-freq
\family default 
 -- Low speed function does position to velocity conversion, scaling and
 limiting.
\layout Itemize


\family typewriter 
\noun on 
(funct)
\noun default 
 stepgen.capture-position
\family default 
 -- Low speed function for feedback, updates latches and scales position.
\layout Standard

The high speed function 
\family typewriter 
stepgen.make-pulses
\family default 
 should be run in a very fast thread, from 10 to 50uS depending on the capabilit
ies of the computer.
 That thread's period determines the maximum step frequency, since 
\family typewriter 
steplen
\family default 
, 
\family typewriter 
stepspace
\family default 
, 
\family typewriter 
dirsetup
\family default 
, 
\family typewriter 
dirhold
\family default 
, and 
\family typewriter