U.S. patent application number 13/283087 was filed with the patent office on 2012-05-03 for method and arrangement for correlating time bases between interconnected units.
This patent application is currently assigned to XINSHU MANAGEMENT L.L.C.. Invention is credited to Lars-Berno Fredriksson, David Lindqvist.
Application Number | 20120109453 13/283087 |
Document ID | / |
Family ID | 32466186 |
Filed Date | 2012-05-03 |
United States Patent
Application |
20120109453 |
Kind Code |
A1 |
Fredriksson; Lars-Berno ; et
al. |
May 3, 2012 |
METHOD AND ARRANGEMENT FOR CORRELATING TIME BASES BETWEEN
INTERCONNECTED UNITS
Abstract
A system and arrangement for correlating time in different time
bases used by interconnected units by timestamping a reference
event with a time determined with respect to a first time base. A
message unit provides the time to a second interconnected unit that
uses a second time base. A translation device is configured to
calculate a difference between the time measured by the first time
base and in the second time base. The difference is used to
translate a time measured by the first clock to a time in a
different time base at run time.
Inventors: |
Fredriksson; Lars-Berno;
(Kinna, SE) ; Lindqvist; David; (Gothenburg,
SE) |
Assignee: |
XINSHU MANAGEMENT L.L.C.
Dover
DE
|
Family ID: |
32466186 |
Appl. No.: |
13/283087 |
Filed: |
October 27, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11554370 |
Oct 30, 2006 |
8065052 |
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13283087 |
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PCT/SE05/00581 |
Apr 21, 2005 |
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11554370 |
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Current U.S.
Class: |
701/36 ;
701/70 |
Current CPC
Class: |
H04L 12/403 20130101;
H04L 2012/40234 20130101; H04L 12/40026 20130101; H04L 2012/40273
20130101; H04J 3/0667 20130101; H04L 2012/40215 20130101 |
Class at
Publication: |
701/36 ;
701/70 |
International
Class: |
G06F 19/00 20110101
G06F019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 30, 2004 |
SE |
0401130-0 |
Claims
1. A system, comprising: a detector unit configured to detect a
first reference event having a first time base generated in
response to movement of a part in a machine and to transfer the
first reference event; a pressure unit configured to detect a
second reference event having a second time base in response to
sensor information within a cylinder in a motor and to transfer the
second reference event; an internal clock having a third time base;
and a translator unit configured to receive and compile the
transferred first and second reference events and the third time
base into a control time base and to send the control time base to
a control unit.
2. The system of claim 1, wherein the control unit is configured to
send control commands using the control time base to a valve
control mechanism.
3. The system of claim 1, wherein the sensor information comprises
pressure information.
4. The system of claim 1, wherein the movement of a part in a
machine comprises a wheel rotation.
5. The system of claim 1, wherein the first and second time bases
are non-linear.
6. The system of claim 1, wherein the third time base is
linear.
7. The system of claim 4, wherein the detector unit comprises a
pulse generator and pulse detector.
8. The system of claim 7, wherein the reference event comprises the
pulse generator generating a pulse in response to the wheel
rotation and the pulse detector detecting the pulse.
9. A system, comprising: a detector unit configured to detect a
reference event generated in response to movement of a part in a
machine; a first control unit configured to generate a first report
comprising a first clock function based on the detected reference
event, a messenger unit configured to transmit the first report;
and a second control unit, configured to receive the first report,
comprising a second time base and a translator unit that is
configured to compile the first time base and the second time base
into a control time base.
10. The system of claim 9, wherein the second control unit is
further configured to determine commands based on the first reports
and to send the commands operating on the control time base to the
first control unit.
11. The system of claim 9, wherein the movement of a part in a
machine comprises a wheel rotation.
12. The system of claim 9, wherein the detector unit comprises a
pulse generator and pulse detector.
13. The system of claim 9, wherein the first time base is circular
and the second time base is linear.
14. The system of claim 10, wherein the command messages control a
braking force applied to the wheel.
15. The system of claim 12, wherein the reference event comprises
the pulse generator generating a pulse in response to the wheel
rotation and the pulse detector detecting the pulse.
16. The system of claim 14, wherein the pulse is generated with an
inverted sign.
17. A system, comprising: a detector unit configured to detect a
reference event; an interface unit configured to interface between
the detector unit and a processor, the processor configured to:
interpret the reference event using instructions stored in a first
storage unit, and transfer the interpreted reference event to a
second storage unit; and a clock configured to determine a
reference time of the detected reference event.
18. The system of claim 17, wherein the interface unit is further
configured to obtain a first reference time from the clock.
19. The system of claim 17, further comprising a function execution
detector that obtains a second reference time from the clock.
20. The system of claim 19, further comprising a capture register
configured to receive the reference event from the function
execution detector and to temporarily store the reference event.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation application of
U.S. patent application Ser. No. 11/554,370 filed Oct. 30, 2006,
the contents of which are hereby incorporated by reference into
this application, which is a continuation under 35 U.S.C. 120 of
International Application PCT/SE2005/000581 filed on Apr. 21, 2005,
the contents of which are hereby incorporated by reference into
this application, which claims priority to Swedish Application
0401130-0 filed on Apr. 30, 2004.
BACKGROUND
[0002] The present disclosure relates to a fixed and/or movable
system, in particular in or for vehicles, for example cars. The
system operates with common or related time bases for indication of
the time of detected or generated events in the system, and/or in a
system or systems connected to this.
[0003] The present disclosure also relates to a device for
effecting the establishment of functions carried out by two or more
units (nodes) comprised in the system in a fixed and/or movable
system, in particular in or for vehicles, for example cars. The
device can relate to arrangements for detection, control, analysis
and/or simulation of comprised units.
[0004] The use of systems of this type in, for example, vehicles,
is already known and reference can accordingly be made, among other
things, to the patent applications and patents submitted by and
granted to the same applicant as the present applicant. In the
respective systems, the message and information (data)
transmissions are carried out using or in accordance with protocols
of a known type, which can be of a standardized type, for example
Universal Serial Bus (USB), Controller Area Network (CAN), Local
Interconnect Network (LIN), Ethernet, IEEE 802.11x, Infrared (IR),
Wireless USB (WUSB), etc.
[0005] With this type of system, there are problems in determining
events and/or time functions without relatively complicated and
bandwidth-intensive arrangements. There is, for example, a desire
to be able to determine the occurrence of the events and/or give
indications of the time so that the normal traffic can be utilized
to indicate the relevant time and/or occurrence of the event, for
example, without extra hardware needing to be involved. The object
of the disclosure is, among other things, to solve this problem.
There is a need, in the respective module units, to be able to
operate with preferably small resources with the object of
simplifying the construction of the units. There should also be
great freedom of choice in the construction of systems and their
relationships. This disclosure also solves this problem.
[0006] A major problem in distributed embedded control system is to
synchronize the generation of events in different nodes to each
other in a timely manner, e.g., reading sensor values, execution of
movements, releasing of power etc. The main solution to this
problem is to create a global time and synchronize clocks at each
node. Usually the time synchronization is made at the communication
level. Typical examples are TTCAN, TTP and FlexRay protocols in the
vehicle industry and SERCOS in the factory automation industry. All
of these communication protocols are time triggered and it is a
common opinion that safety critical distributed embedded control
systems have to be based on a time triggered communication. An
alternative to synchronizing clocks is to have each module relying
on its own local clock and have a time translator recalculating the
time of each clock to a common global time, but it has been
regarded impossible to do in real time.
[0007] U.S. Pat. No. 5,896,524 suggests a method to recalculate
clock readings by associating event pairs related to each other.
However, such conventional methods cannot be used in realtime
(e.g., see column 1, line 65 through column 2, line 4). What is
needed is a method and apparatus that calculates the relationship
between local clocks at run time. What is further needed is to
calculate the relationship between local clocks and a global time
base at run time.
[0008] U.S. Patent Application Publication US2006-0143345A1 shows
that, in realtime systems at run time, it is more efficient to use
different time domains within the system, wherein each time domain
is created according to the need of cooperating nodes, rather than
to rely on a global time. However, a global time may be better used
for analyzing a system.
[0009] Each system in which the disclosure can be used can be
regarded as individual, one or more series or sequences of events
that are related to each other in time and space. There can be
different time descriptions and time frames within one and the same
system. Smaller systems can be comprised in the system, which in
turn can, now or later, be comprised in other systems. During the
first stage, the "drawing board" stage, of a system development, it
is expedient to relate all the events to one and the same time
frame, for example related to the physically defined second. The
degree of coordination that is required of the different events in
order for the required system function to be achieved can be
analyzed in a first stage. In a second stage, an analysis of the
relationship of the individual events to each other can indicate
that other time frames and the utilization of knowledge concerning
the association of different events to each other can simplify the
design of the final system and the description, verification and
validation of the same. The disclosure simplifies these development
processes.
[0010] For analysis or verification of systems, there is a need not
only to timestamp events that have occurred, but also to know with
what precision and/or accuracy the timestamping is carried out.
[0011] It can happen in systems that different parts of the system
relate events to different time bases, which in turn are related to
each other.
[0012] Analysis and monitoring instruments of different types for
vehicles are often based on standard computers with operating
systems, for example a personal computer (PC) with WINDOWS XP.RTM..
The operating system (OS) simplifies the development of the
software at the price of precision of timestamping of external
events. Therefore special units are introduced between the PC and
the bus system that, among other things, comprise a clock for
timestamping of incoming time messages. For example, with the
utilization of the program CANANALYZER from the company VECTOR, a
CANCARDXL from the same company is connected to the PC. The
CANCARDXL has a local clock and can timestamp messages from two CAN
busses. If there is a need for several CAN busses, an additional
CANCARDXL unit must be connected to the PC and the two CANCARDXL
units must be connected to a coordination unit via a coaxial cable
arrangement in order to synchronize their local clocks to a common
time. By utilizing the disclosure, timestamping can be carried out
with great precision, utilizing only components to be found as
standard in the PC.
SUMMARY
[0013] This disclosure addresses time synchronization in
distributed embedded control systems by selecting specific events
and their relation to the local time at different nodes ahead of
time to be identified as reference events. A time translator can
then filter out messages with time stamps related to the reference
events, and a respective transmitting node within the system. By
defining the relationship between a reference event, time-stamped
according to a first clock at a first node, and the time relation
of the reference event to a second clock, the time translator can
recalculate the first time to the second time and vice versa at run
time, i.e., in real time.
[0014] In addition, a reference event can generate several
secondary events. By defining the relationship between such a
reference event, its secondary events, the time stamping of these
events, and how these time stamps are transmitted to a time
translator, a time translator can be programmed to recalculate the
time at one time domain to the time at another time domain at run
time
[0015] An occurrence of the execution of a function can be arranged
to be able to be detected and determined by means of one or more
devices that perceive time, for example clocks, and/or devices that
indicate events, which devices are comprised in one or more of the
units that constitute or form module units in the system. The
system can thereby include one or more serial, distributed and
protocol-utilizing systems. The respective determination is to be
arranged to form the basis of or invoke functionality in the system
and/or in monitoring, analyzing, verifying, completely or partially
simulating or stimulating devices in the system.
[0016] A consequence of the concept of the disclosure is that the
same or different events that are perceived or generated by
different modules in the same or different systems can be time
related in a simple way. The modules that are affected by the time
relating can perceive certain events at the same time, or
alternatively certain different events for which the time
relationship is known. Such events belong to the group "reference
events". The modules can be arranged to generate or detect
reference events, display local clock function, be able to read off
local time upon the detection or generation of a reference event
and provide time information on the basis of the value that was
read off being sent to one or more translation units. The
translation unit(s) then utilize these values in order to create a
common time reference for the modules and events concerned, with
the result that it is possible to create time indications that are
comparable. The translation unit can be considered to create a
common time domain for relating events. Comparisons can be carried
out in different time domains that can be created by different
translation units, which can utilize common reference events. In an
embodiment, the bit pattern in a communication protocol is utilized
as reference event. For example, the Start Of Frame bit (SOF) in
CAN is suitable. More specifically, the sampling point in the bit
can be used, as certain CAN controllers, for example MCP 2515 from
MICROCHIP (Microchip Technology, Inc., 2355 West Chandler
Boulevard, Chandler, Ariz., USA, 85224-6199), generate a signal for
this that can be used in order to trigger the requisite electronics
for the reading off of local time for the occurrence of the
event.
[0017] Further developments of the concept of the disclosure are
apparent from the following.
[0018] For example, the system operates with event functions and
accordingly reference events can be utilized which can be related
to one or more reference event generators. A reference event can be
sent from a common point and can refer to a common group. The
reference events can occur at particular intervals and can
themselves define the clock function (compare with a Phase Locked
Loop). The reference event detectors must be able to be placed in
the units and accordingly a detector can be placed in each unit. An
interrupt generated by a selected protocol's communication circuit
can be utilized as a detector. The respective detector can be set
up by defining or implementing how it is to be obtained (for
example, by connecting to a suitable layer in the protocol stack
and searching there for a special packet/bit pattern/edge). Events
must be able to be related by group, for example with regard to
sequence or time. The group can work with a common starting point.
Thus, for example, a unit can communicate directly with all units
in the group or at least send messages that all the other units can
detect. The messages can represent typical events. The respective
message can, for example, include packets according to any serial
communication standard, for example the protocols mentioned in the
introduction. The reference event can consist wholly or partially
of a message. The USB protocol's Start-of-Frame (SOF) packet can
advantageously be selected as reference event. This packet is
transmitted in the normal way and has a sequence number, which
facilitates the correct association of timestamp to reference
event. USB packets propagate in a USB system in a defined way and a
USB host can be regarded as a reference event generator in its own
time domain, distinct from other time domains, for example the
domain in which a WINDOWS application operates, in the same PC as
the USB host. The reference events can be transmitted to all units
that are comprised in the same USB arrangement, that is all units
can listen to the same event, for example, at the same time. The
phrase at the same time here means a maximum of 50-100 ns jitter in
the detection for all the units plus up to a couple of hundred ns
constant delays. A USB Hi-speed maximal delay can be 26 ns in the
cable, 4 ns in the "hub trace", 36 hs-bits in the hub electronics
in a maximum of 5 levels plus 30 ns for connecting in last unit,
totaling 530 ns. A Hi-speed jitter due to the USB protocol can be a
maximum of 5 hs-bits per hub and a maximum of 5 hubs can be
connected, which gives a maximal uncertainty of 25 hs-bits, which
corresponds to approximately 50 ns time inaccuracy for the
propagation of an SOF through a USB connection. A "hs-bit" is here
considered to be the duration of a hi-speed USB bit time i.e.
1/(480 MHz), or approximately 2 ns.
[0019] In the embodiments, each unit can comprise a local clock
which is able to be read by or in the application in question.
Timestamping can be carried out of each reference event and the
timestamping is carried out preferably with externally triggered
capture register. Correct association of the timestamp with the
reference event can be ensured. The timestamps can form the basis
for relating clocks, time and events. The clocks or the read-off
time must be able to be related. In addition, in an embodiment, a
time master can be included, whose time is, if required, to be
regarded as global (in groups). In order to create a transitive
relationship, that is even if two different units cannot directly
relate their time to each other, this can still be achieved if both
can relate their times to a utilized master or intermediate unit.
The time master can, in turn, be synchronized or related to a
second reference, for example GPS. This gives the system access to
a correct physical second that can be used for physical
calculations, for example engine speed, power, accelerations, etc.
The location of the time master can be in a common point in the
system concerned, can be separate or can have another role in
another unit. The role or the function can be changed. In an
embodiment, the system does not need to utilize any master unit,
but instead the translation takes place in an all-to-all function.
In addition, it should be pointed out that a time master does not
need to have its own physical clock, but instead can construct a
virtual clock function by utilizing timestamps of reference events
carried out by and messages from modules with their own time
domains, that are connected to the system. With knowledge of the
relationships of the reference events and respective time domains
to each other, the time master can transform the time information
to a time domain of its own and give respective time information
referring to its own time domain to other units within or outside
the system.
[0020] An important part for an efficient utilization of the
disclosure is the actual development process for the device. In a
first stage, the events are identified that are to be generated and
detected and their relationships to a common notional time base
relating to times and a permitted range around these, in order for
the device to have the required functionality. In a second stage,
events are identified that can constitute reference points between
different units, in order for these to be able to detect, initiate
or generate other events within the required time range, relative
or absolute. In a third stage, functions are implemented in an
actual design in order to achieve the required functionality. It
should be pointed out that reference events are defined at system
level and that these do not need to be known at module level. A
basic idea in the disclosure is the concept of time. Each
interaction between given event patterns can be regarded as having
its own time domain, that is the time frame is based on its own
time tick generator (which can be linear or non-linear) and the
time indication is given as the number of ticks, whole plus if
required parts thereof, according to a linear or circular model.
The different time domains can be transformed from and to each
other. Domains with circular model will appear as a cyclic course
of events and those with a linear restricted model as discrete
intervals in a linear unrestricted model. For general analysis
tools, it is expedient to utilize a linear unrestricted model with
the physical second as time tick. Another basic idea in the
disclosure is the concept of a system. According to the disclosure,
the system is regarded as a number of event functions that are
coordinated by a controlling unit, the sum of all the event
functions. These functions can be of two types, event-generating or
event-detecting. The coordination takes place in time and space. A
part of the coordination is carried out mechanically, and a part is
carried out through the exchange of information between electronic
units, of which a part of the latter is carried out via serial
communication, for example of the CAN or USB type, directly or in
combination. The system S is described with the number n of
subsidiary functions F as:
S = 1 n F i , ##EQU00001##
where F.sub.i is the sum of the number m of events h, that is
F i = 1 m h j ##EQU00002##
[0021] In the first stage, the system in one or a few time domains
is described, which system is well suited for describing and
calculating its characteristics, for example the time domain T.
This can be represented symbolically by:
S ( T ) = 1 n F i ( T ) ##EQU00003## F i ( T ) = 1 m h j ( T )
##EQU00003.2##
[0022] In the second stage, a number of events are identified that
are mutually interconnected between functions of interest and which
are suitable for providing a time domain for the functions. These
events are designated reference events. It is often expedient to
have non-linear time ticks in time domains for event functions that
are mechanically connected. In addition, reference events are
identified that are connected in chains, that can be described
mathematically, to different time domains. Starting from a
generated event in a time domain, the detection of which generates
a further event (in the same or another time domain), which in turn
is detected in another time domain, during the development work a
mathematical transfer function can be created between two time
domains similar to a transformation of one coordinate system to
another. Such transfer functions are implemented as required in the
system's different units. The system can be described symbolically
as follows:
S=.SIGMA.F.sub.i(T.sub.q T.sub.k, . . . )
T.sub.1=.A-inverted.T.sub.m, where .A-inverted. is a
transfer/reproduction operator between the time domains 1 and
m.
[0023] In an additional embodiment, one or more time coordinators
can be utilized. These can delegate any role as time master and
receive and send timestamps of reference events. In this
connection, the transmission can be carried out to any translation
units in order for these to be able to calculate and translate the
time in question. In an additional embodiment, certain units carry
out the actual translation function in question. The time
coordinates can receive and send other timestamps to any
translation units. In an embodiment of the disclosure, the time
coordinator is arranged in a common point in the system in
question. The disclosure also takes into account the need for time
translators to be included. Time translators handle the translation
of time for the units that do not carry out the translation
themselves.
[0024] A time translator can be located anywhere in the system, but
a location in a common point is advantageous from the point of view
of efficiency. A time translator can carry out translation from one
unit to another via a selected reference time or alternatively
according to the all-to-all principle, that is directly from each
unit to every other unit. In this connection, a logical translation
matrix can be utilized. A matrix that can keep track of how
translation is to be carried out rapidly from all-to-all can,
however, assume large dimensions and require substantial resources
to keep updated (the complexity scales quadratically), but gives as
a result faster translations. It is also possible to carry out the
time translation just by keeping the reference timestamps updated,
but this results in more work per translation. The translation unit
can keep statistics of how well the clocks are related and can send
the measurement value together with this information as a
parameter. The inaccuracy can be calculated and sent with each
measurement value. The translation function can be carried out with
greater accuracy afterwards, that is when an additional reference
message has been exchanged.
[0025] In connection with this, the derivative for the current
period can, for example, be used instead of assuming that the same
derivative applies as in the preceding period. Expressed in more
general terms, interpolation is used instead of extrapolation for
indication of a value. This is of particularly great significance
for analysis and verification of a system's function. In short, it
can be said that each unit/module that has been given access to the
occurrence of reference events in different time domains can be
arranged to carry out translation between the time domains,
irrespective of whether the units/modules themselves are comprised
in or represent any of the domains or not. In order that no
ambivalences shall arise concerning the time domain to which a
particular indication belongs, protocols should be set up which,
for example, state who translates what and to what extent a unit's
incoming/outgoing indications are to be considered to belong to the
time domain of the transmitting and/or receiving unit.
[0026] The further developments can comprise the system's units
being physically synchronized to their local clocks in accordance
with some master time. This in itself increases and complicates the
hardware in the units, which in such a case must perhaps still be
supported by software resources. All clock operation can be carried
out proactively, that is once the clock is to be used, it already
shows the time in the master's time domain and it has only to read
this off, which can reduce the unit's response time and in this way
justify the greater complexity. The respective unit can itself
calculate how it is to regulate its clock using the master's
timestamps of the reference events. The respective unit can let the
coordinator or translation unit calculate how the regulation and
offset compensation are to be carried out by sending their
timestamps of the reference events to the same and then awaiting a
response.
[0027] The units can translate their time to another time before
the time in question is transmitted. This does not need to require
any extra hardware, but instead can comprise some software
resources, depending upon how the translation is to be carried out.
The translation work is carried out between production and
consumption of the value. The unit can itself calculate how the
translation is to be carried out using the master's timestamps of
the reference events. The unit can let the coordinator/translator
calculate how the translation is to be carried out by sending its
timestamps of reference events to the same and then awaiting a
response. The units need not be aware of another time than their
own as far as the time relationship is concerned. It is sufficient
for the units to send their respective timestamps of reference
events to the coordinator. This requires relatively little resource
in the units. The translator is responsible for all
translation/time relating. The translator is arranged with compute
power appropriate for the translation method.
[0028] Depending upon what precision is required for the detection
of a reference event within a system, a group of individual events
can be regarded as one and the same reference event. For example,
SOF in CAN messages can be utilized as a reference event. A
practical way of detecting SOF in CAN is to utilize the sampling
point in the CAN controller. As the detection of SOF in the
respective node is dependent upon the setting of the sampling point
(which can be different in different nodes) and the nodes' distance
to the transmitting module, the time of the detection will vary
depending upon which node is transmitting and the setting of the
receiving module. If SOF of any message is used as a reference
event, in practice it is a group of events that is utilized.
[0029] The precision of the reference event is obviously not
sufficient to measure, for example, the delay between different
messages from different nodes. This is possible if instead
individual CAN messages are selected as reference events (if SOF is
to constitute a reference point, the message may not, except in
certain special circumstances, have won the bit arbitration from a
message with lower priority). More precisely, it can be the
occurrence of specific edges/bits in the different nodes that gives
the ability to determine delays between units, and the fact that
these edges/bits have been propagated in both directions relative
to the delay that is to be determined. Consequently, specific
edges/bits that have been propagated through the system as
undisturbed as possible are suitably selected for determining
delays. An edge/bit that very probably originates from only one
transmitting unit can be one following the arbitration field in a
CAN message (however, suitably not the ACK bit, that is transmitted
by receiving units).
[0030] At the system level, it is known which CAN messages the
respective nodes transmit. By each of the transmitting and
receiving modules timestamping one and the same message, and
messages being sent in both directions through the system, the
delays between respective modules can be measured and calculated to
a common time domain.
[0031] In one embodiment, a unit, for example any such unit, can
act as time master (with or without its knowledge). The units can
work with a translation function for each time that is to be
translated/related to the master time. The translation work is
carried out between production and consumption of the value. This
can result in a delay of possible consumption of the same.
[0032] The translation function can be carried out by the offset
between the first and second times being added to the time that is
to be translated. With this method, little compute power is needed
for the respective translation. Synchronization/time relating is
preferably carried out frequently with this method in order to
minimize the effect of the respective clock's drift in relation to
the other clocks. The translation can also be achieved by both
offset and fixed frequency error compensation (drift compensation).
The translation A.sub.x to B.sub.x (new and old refer to reference
timestamps) can be carried out as follows:
B.sub.x=B.sub.new+(B.sub.new-B.sub.old)*(A.sub.x-A.sub.new)/(A.sub.new-A-
.sub.old)
[0033] Given a computer with limited resolution and/or calculation
accuracy and given that the times A and B are already scaled to be
approximately equal (the derivative between them is approximately
one), the following method can give a better result:
B.sub.x=B.sub.new-(A.sub.x-A.sub.new)+(((B.sub.new-A.sub.new)-(B.sub.old-
-A.sub.old))*(A.sub.x-A.sub.new))/(A.sub.new-A.sub.old).
[0034] Viewed analytically, the two methods are equivalent and are
based on linear regression. As the calculation is carried out using
a computer, discrete values must be used which results in limited
possibilities for representation which has the result that the
sequence is important. Irrespective of the method, care must be
taken that the calculation does not overflow or get truncated in an
undesirable way. The latter method can be a way to make this
easier.
[0035] There can thus be great computing power per translation but,
in return, the time relating does not need to be carried out as
often in order to attain the same precision. The constant frequency
error can be determined offline or the frequency error can be
measured online. There can also be cable delays of a not
inconsiderable size, which must then be included in the
calculation. In one embodiment, negligible cable delays are
selected. In the offline case, offset and/or frequency deviation
can be measured once and for all and appropriate constant values
can be calculated and inserted in the translation function.
[0036] In one embodiment, where delays can be measured online,
units can be arranged so that reference function executions
propagate through the communication medium in both directions
relative to the units whose delay is to be measured, during which
the two units determine the occurrence of the reference function
executions relative to some time. These determined occurrences can
be used to determine the delay.
[0037] The translator can save information in the respective unit
about how the clock behaved during the most recent session in order
to be able to phase in the unit in the next function stage more
quickly and/or make the synchronization/time relating easier for
the translator.
[0038] The more of the abovementioned resources, methods and/or
functions that can be made dedicated, the more easily predicted
and/or easily used and hence perhaps also more reliable is the
utilization of clocks, time, time synchronization and/or time
relating in the system.
[0039] The system described can advantageously be used on a
vehicle, for example a car, lorry, tractor, scooter, boat, ship,
airplane, etc. For the direct control system in a car, it is
advantageous to have time domains with varying time tick in order
to coordinate movements that are associated with the mechanical
function of the driveline. As each so-called ECU (Electronic
Control Unit) comprises a CPU that is controlled by an oscillating
circuit that is independent of the movement of the mechanics, an
ECU has at least two time domains with associated transformation
operator. One and the same ECU can interact with several other ECUs
that form groups working in a time domain common to the respective
group.
[0040] The whole system in a car (vehicle) can have a linear finite
time domain, which, for example, starts with the ignition key's
"on" position and which ends with the ignition key's "off"
position. In this time domain, the system behaves in a way
expedient for driving the vehicle. When the ignition key is in the
"off" position, the system operates in a different time domain, for
example a circular time where information is obtained from some
operating module that periodically listens for commands from a
wireless signal for opening or locking of the car's doors and/or
control of alarm functions. The car can be comprised in other
systems connected with traffic control, traffic monitoring,
law-enforcement monitoring, etc., which make completely different
demands, but which now and then interact with the car's direct
control systems.
[0041] Here, other time domains can be better suited, for example a
time domain where the time tick varies with the location of the
car. In a monitoring system, a need to update the car's location
can be lower when it is in the country in normal circumstances than
within built-up areas or in the vicinity of an accident. This frees
bandwidth requirements in both the car's control system and the
monitoring system. The present disclosure has a great advantage in
that the development of systems that are to be incorporated in
larger systems at a later date can be carried out without advance
planning. When the systems are to be incorporated, the respective
systems' event-generating and event-detecting functions are
reviewed. As the respective systems have many such functions, there
is a great probability that events will be found that can be
utilized as reference events for the coordination of the systems
that is required in order to obtain the required result. If
suitable events cannot be detected during the coordination
analysis, expedient or suitable event-generating or event-detecting
functions can be created and introduced into any one or both
systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] A currently proposed embodiment of a device that has the
significant characteristics of the disclosure will be described
below with reference to the attached drawings in which:
[0043] FIG. 1 shows a schematic illustration at system level of how
various comprised module units and systems are logically
interconnected,
[0044] FIG. 2 shows in detail a unit 103 comprised in FIG. 1,
[0045] FIG. 3 shows a simple schematic illustration of a subunit
105 or 350 shown in FIG. 1,
[0046] FIG. 4 shows a schematic illustration of a first unit 104
comprised in FIG. 1,
[0047] FIG. 5 shows two possible ways of measuring delays between
units,
[0048] FIG. 6 shows how the USB protocol's SOF packets can be
utilized for time relating in a system with a computer, for example
a PC, and a number of units connected to this,
[0049] FIG. 7 shows a traffic system in which the cars utilize
local independent time domains that are coordinated with a traffic
monitoring system with centrally coordinated, flexible time
domains, and
[0050] FIG. 8 shows schematically a traffic monitoring system.
DETAILED DESCRIPTION
[0051] In FIG. 1, three different systems are symbolized by S1, S2
and S3 interconnected to a system S. The systems can be of the
types described in the introduction, for example USB, CAN,
Bluetooth, etc. The serial bus connections in the systems are
indicated by B1, B2 and B3. The systems work with protocols P1, P2
and P3 associated with the standards. In the systems there are one
or more first units 104, 104', 104''. In accordance with the
disclosure, function events or function executions in the systems
are to be related with regard to some type of time, for example
linear time, circular time, virtual time, etc. The empty boxes in
FIG. 1 illustrate other modules connected to their respective bus
and which could each contain a microcontroller and related clock
used, for example, to read sensor values, control mechanical
actuators, or to control electrical devices.
[0052] The systems work with a number of functions. Any first
function is indicated by F1 and relates to one or more reference
times or master times to which the first units can relate. The
times in question can be, for example, real and/or virtual. The
time that any clock function 352, 410, 457 (not indicated in FIG.
1) represents can constitute an example of a real time, which can
be with or without the knowledge of the unit. An example of a
virtual time is an average time extrapolated from suitable units'
time.
[0053] The systems can also comprise one or more second functions
F2 that represent translation functions between different times in
the system. Depending upon the characteristics of the times, a
suitable method is selected for determining the translation
functions. If, for example, two times both represent linear/modular
times with tick of the same size, linear regression of the type is
advantageously used.
[0054] A third function is indicated by F3 and is arranged to
generate/represent the reference function execution that can at
least be detected by the units that must be able to be related
directly. This function can either be arranged in one or more
dedicated new units and/or in any one or more existing units. As a
proposal, suitable existing function executions in the system are
identified and arranged to carry out the function. Examples of such
suitable existing function executions in a USB system are SOF
packets, which, in addition, are provided with sequence numbers
which make easier the correct identification of specific packets. A
proposed existing function execution in a CAN system that could be
suitable for the disclosure is the SOF bit or suitable edge/bit
inside a message and then preferably an edge/bit that occurs after
the identification field, but before the ACK bit. In the case when
an edge/bit within the data field constitutes F3, the transmitting
unit's Time Reference (Tref) should, in addition, be able to be
sent as data in the same packet in order to save time and
bandwidth. In order to make the system more stable, an edge/bit in
a message should not be accepted for reference function execution
before the whole message has been validated.
[0055] The first function F1 can, in principle, be arranged to be
in any of the units, with or without their knowledge. The second
function F2 must, however, know which unit or units represent the
first function F1, assuming that F2 wants to utilize F1 in
question. The second function F2 can be arranged in one or more of
the units. In this case, the units can be arranged to carry out
translations from or to their own times. Alternatively, a unit in
question can let any other unit carry out the translation in
question. The first function F1 can, in turn, be synchronized with
or related to another time, for example UTC and the physical second
via GPS, 107. Protocols can be established for how times are to be
interpreted and/or translated. If, for example, a group of units is
arranged to be able to translate times between themselves, incoming
times are selected, for example, that are already translated, while
times that are to be sent are first translated to the receiving
unit's time or vice versa. Alternatively, as described, F1 can be
utilized in the form of both incoming and outgoing times being
interpreted as or translated to the first function F1.
[0056] In one embodiment, a second unit 102 can advantageously be
arranged with the first function F1, the second function F2, the
third function F3, the fourth function F4, the fifth function F5
and/or a subunit 105. Such an arrangement is particularly
advantageous if the protocol P2 consists of USB. In this case, unit
103 should be able to correspond to a unit 200, as shown in FIG. 2,
which contains one or more units 201, where 201 can be internal
and/or external USB hubs and/or units such as unit 450 in FIG. 4.
In one embodiment, the second function may include use of a
centralized translator, which means that the first units should be
able be implemented relatively easily. A decentralization of the
translation function, on the other hand, causes a somewhat higher
complexity of the first units, but in return the bandwidth can
perhaps be lower and fewer units can be utilized in the system,
while at the same time the reliability can increase as the
resources are dispersed and accordingly no "single point of
failure" needs to be introduced.
[0057] FIG. 3 also shows a fourth function F4 that detects the
function execution that the third function F3 generates. The first
units 104 in FIG. 1 are arranged with one or more subunits 105.
FIG. 3 shows a simple schematic drawing of unit 104 where unit 300
corresponds to 104 and unit 350 corresponds to 105. The subunits
350 comprise one or more time-perceiving devices 352, function
execution detectors F4, and subunits or capture registers 351
arranged to store times. In the event of an actual detection, the
clock 352 is read off and saved in a subunit 351 that saves the
reference times in question, here designated Tref. The latter
timestamping or reading off can be transmitted to units carrying
out the second function F2, which for this purpose are arranged to
determine how the translation in question is to be carried out. If
the second function F2 is a part of the unit itself, one or more
Trefs are awaited from other unit or units, which can be used for
determining how translation to/from this and/or other units is to
be arranged to be carried out. Alternatively, a unit's incoming
Trefs can be selected in order to synchronize the local clock to,
for example, any F1 on the basis of one or more timestamp(s). The
Tref values can be considered to form the basis for relating all
time in the systems. This applies irrespective of whether it is a
question of translating time locally, synchronizing the time in
question locally, or leaving the translation to some other unit. As
shown in FIG. 3, any of the functions/roles can be arranged in the
unit 300.
[0058] One embodiment of the clock function 352 and the subunits
351 is to utilize a counter/timer in a suitable CPU and allowing a
detection in F4 trigger a reading off of the counter/timer 352 to
capture register 351. The clocks are, in other respects, intended
to define system times and can be read off by applications that are
executing in the units, in contrast to the clocks that are hidden
from the applications such as are often used in certain
time-controlled communication protocols. An extremely advantageous
facility that the disclosure provides is that clocks can be made as
accurate as their applications require, without forcing other
clocks in the system to be equally accurate.
[0059] An advantageous accuracy can be obtained if the first units'
times are translated directly to each other instead of carrying out
the translation via one or more first functions F1. More precisely,
it can be said that negative effects originating from, for example,
reading off errors and jitter in system components' electronics and
logic can be limited. If, however, it is desired to have all events
in the system on a common time axis or basis, for example for
analysis, it is advantageous to utilize a first function F1 and
plot the events concerned along the time axis that F1 describes. A
fifth function F5, shown in FIGS. 1 and 3, includes a coordinator
function which receives and sends reference timestamps to a unit
that requesting the timestamps concerned, or to all the units that
operate with function F2. The fifth function F5 suitably
determines, with or without guidance from one or more second
functions F2, which unit or units are to operate as or have the
role of F1. The second functions in the system or the systems
should, in addition, be able to calculate and send/associate
translation accuracy/inaccuracy and/or stability/instability of the
times/clocks/translations. This is in order not to need to assume
that the worst case always applies, but instead to be able to
utilize current assumptions.
[0060] In the most general case, the units do not need to know the
originator of a specific reference function execution. If the
units, however, are arranged to be able to measure any delay over
the serial communication between two units, they may, however, be
provided with this facility. The delay can, for example, be
determined with knowledge of a number of occurrences of reference
function executions that propagate in both directions relative to
the units between which the delay is to be determined. FIG. 5 shows
examples of how this can be carried out.
[0061] If unit 102 is, for example, a computer of the PC type with
an operating system such as, for example, WINDOWS XP, the functions
F1, F2 and/or F5 may be able to be implemented in the software that
communicates with the OS's interface to the communication channel.
The advantage of this is that PC computers are very common today
and often are already used in many planned target systems and, in
addition, usually have resources that can advantageously be
utilized. Depending upon the implementation method and system
requirements, great care must be taken so that calculations are
carried out with sufficiently short response times, irrespective of
what the OS is otherwise engaged in. This embodiment can provide a
simple, flexible and accordingly cost-effective way of, for
example, connecting a computer by means of the hardware to several
CAN systems for analysis and/or interaction and, at the same time,
provide a competent way of relating time within and/or between the
systems. FIG. 6 shows examples of how this can be carried out.
[0062] FIG. 4 shows in greater detail than in FIG. 3 a schematic
construction of a unit 104 according to FIG. 1, here designated
400. For the sake of clarity, it is provided with two
microprocessors, but the task can be carried out by one
microprocessor. The unit 400 is connected on one side to a system
401 via the connectors 402, 403 and the connection cable 404. Via
the interface electronics 405, the signals on the bus can be read
by the microprocessor 406. Using instructions stored in the memory
407, the signals can be interpreted in accordance with the protocol
408 used in the system. In its simplest form, the interpretation
can mean that only the received bit pattern is transferred, but the
interpretation can be of a more complex type where much
supplementary information provided by the protocol's rules is added
by the microprocessor. Application software, that is instructions
for one or more applications that process information available to
the microprocessor, is also stored in the memory 407. The
information thus interpreted is transferred to the dual-ported
memory 409. Additional information of interest can be added to the
interpreted information, for example timestamping when the
information was obtained from the system. The time is obtained from
the clock 410 which is triggered to be read off in a suitable way
by the interface electronics 405, 414, 419 or alternatively by
function execution detectors 424, 426, 428, for example when
reception of a message commences. In order to make the reading off
of the clock more independent of the processor 406, the event can
be stored temporarily in capture registers 425, 427 and/or 429. The
information is stored in the dual-ported memory in an organized way
in accordance with rules depending on the system protocol's
requirements, so that specific information is stored in a specific
location indicated by the table 411. The dual-ported memory 409 can
be read by the microprocessor 412 which can communicate, according
to a second protocol, using rules stored in the memory 413, and
physically via the interface electronics 414, with a second system
415 via the connectors 416 and 417. Rules are also stored in the
memory 413 for how the information stored in 409 according to the
rules in 407 and 411 is converted according to the rules for the
second protocol 418. In simpler systems, the second protocol can be
based on CAN and several units 400', 400'', etc., of the type 400.
In the same way as described above, the unit 400 also contains
rules for a third protocol with the interface unit 419 and
connectors 420 and 421 which connect to the link 422 with the
protocol 423. A suitable protocol can be based on USB.
[0063] In order to be able to synchronize a local clock 410 to an
external time, for example, any F1, the processor should at least
be able to set a new value in the clock. For the sake of simplicity
and reliability, the interface between the clock and CPU should,
however, allow the processor to, for example, ask the clock itself
to compensate for a given offset and/or frequency error in a way
that is acceptable to the unit and the system.
[0064] As the ability to get WINDOWS to carry out tasks in real
time is greatly limited, it can be advantageous to let second unit
102 include a separate computer system with an OS better suited for
the task. Such a computer system can be a unit or module 450
according to FIG. 4 with a microprocessor and peripherals specially
adapted to handle communication and calculation problems. A number
of modules such as unit or module 400 can be connected to the unit
450 via a suitable connection, for example a USB connection. Such
an arrangement has many advantages. The analog and strictly
real-time problems are solved by the module 400, while the
calculation-intensive and less real-time-critical tasks are handled
by the unit 450. The module 450 is connected directly to one or
more modules 400 by connectors that are illustrated by 451, 452,
451', 452', etc. Communication circuits 453, 453' are connected to
a microprocessor 454 with associated peripherals, among other
things memory or memories. These memories contain applications
software, that is instructions for one or more applications that
process information available to the microprocessor. A memory card
455 is arranged for log equipment, recording and playback
capability, etc. A memory 456 connected to the microprocessor can
be written to and read from in two (both) directions, that is from
both the system side and the tool side. The memory can be divided
into a number of subsidiary memories with different algorithms
456'. The clock 457 can be synchronized with or related to the
clock in the first unit 410 via the protocol in the abovementioned
way. To assist with this, there can be a function execution
detector 463 and capture register 464 arranged in a similar way to
components in the unit 400.
[0065] In this way, all first units 104 connected to a second unit
102 can be time synchronized or time related. In the same way,
second units 102 should be able to relate time between themselves.
Through time synchronization of the different units, the execution
of the applications in the different units can be synchronized or
related to each other. Execution of applications or parts of
applications that are responsible for measuring can, in this way,
be coordinated with execution of applications or parts of
applications that are responsible for communication within and
between the different units. This means, among other things, that
messages sent according to an event-controlled protocol, for
example CAN, can appear in a time-controlled way, as applications
for the transmission of messages are executed and coordinated in
time.
[0066] As a result of the execution of applications for
measurements being coordinated with the transmission of measurement
results, a time relationship is obtained between the measurement
and the distribution of the measurement results in the system in
the form of messages. The same can, of course, be carried out for
indicated events and messages with information about the respective
events. Together with the unit 400 and also with suitable software,
the unit 450 can simulate completely or partially an ECU in an
ordinary CAN system in a vehicle. The unit 450 can be equipped with
means for communication with other network protocols, for example
Bluetooth 459 and TCP/IP 460 for communication between a network of
units 450 and/or tool units implemented in a PC or PDA. As an
alternative to storage disks so-called "USB mass storage devices"
can be connected to a USB connection. For communication over a
telecommunications network, the unit can be equipped with a GSM
module 461 and for time synchronization or clock synchronization
with a GPS module 462 which can also be utilized for position
determination. See above, regarding the protocols.
[0067] Irrespective of whether the unit 102 includes a normal PC or
a unit such as 450, it can advantageously carry out the function
F3, in particular if the selected protocol is USB and the unit is a
USB host, which means that the unit generates SOF packets. As
mentioned above, these are suited for carrying out reference
function executions.
[0068] FIG. 5 shows the measuring of communication delays between
units, where the units 501 and 502 can be of the type, for example,
such as unit 400. In the first case, unit 501 sends a message 503
to unit 502 and both timestamp the message with their local clock.
We can call 501's timestamp of 503 T.sub.ref13, and 502's timestamp
of 503 T.sub.ref23. Thereafter, 502 sends a message 504 to 501
which is timestamped by the two units. 501's timestamp of 504 can
be called T.sub.ref14 and 502's timestamp of the same can be called
T.sub.ref24. If, for example, 502 thereafter sends T.sub.ref23 and
T.sub.ref24 to unit 501, 501 can determine the communication delay,
T.sub..lamda.=T.sub..lamda.501+T.sub..lamda.gem+T.sub..lamda.502,
between 501 and 502, for example using the following method:
{ T .lamda. = T .lamda.501 + T .lamda. gem + T .lamda. 502 T
.lamda. gem = ( T ref 27 - T ref 17 ) - ( T ref 18 - T ref 28 )
##EQU00004##
where T.sub..lamda.501 and T.sub..lamda.502 represent the delay
from the units 501, 502 to their respective connection point to the
communication channel. The "gem" portion of the subscript is
derived from the Swedish word for "common" i.e. "gemensam".
[0069] An additional variant of the determining of delays is also
the one shown in FIG. 5. Instead, a unit 505 sends a message 507
which, in accordance with the figure, first reaches 501's
connection point in the communication channel and then 502's
connection point, and 501 timestamps the message as T.sub.ref17 and
502 as T.sub.ref27. Thereafter, unit 506 sends a message 508 that
propagates through the communication channel in the opposite
direction. This time, the message reaches 502's connection point
first and thereafter 501's connection point. 502 timestamps it as
T.sub.ref28 and 501 as T.sub.ref18. The delay in the shared part of
the communication channel T.sub..lamda.gem can then be determined
according to:
T.sub..lamda.gem=(T.sub.ref27-T.sub.ref17)-(T.sub.ref18-T.sub.ref28)
[0070] Both these simple variants of delay determination assume
that the Trefs utilize time tick of the same size and that any
frequency deviation between the units 501 and 502 can be made
negligible or can be compensated for by any of the methods.
[0071] FIG. 6 shows an embodiment of how the USB protocol's SOF
packet can be utilized for time relating in accordance with the
disclosure. The system comprises a number of units 603, 603', 603''
which can be of the type, for example 104 or 400. These are
connected via one or more USB hubs 602 (for example of type 103 or
200) to a computer 601, for example a PC, which can also be of the
type, for example 102. 601 transmits SOF packets 651 as it should
in accordance with the USB protocol at regular intervals. This can
constitute an example of the previously mentioned function F3, that
is the reference function execution generator or reference event
generator.
[0072] A Start-Of-Frame packet, SOF, contains typically a
Start-Of-Packet/Sync field 691, an identification field 692, the
identification field inverted 693, frame number 694, CRC field 695
and finally an End-Of-Packet field 696.
[0073] The unit 603 contains a USB controller 631 which in turn
contains a device 632 designed to detect SOF packets 651. The
detections in 632 are arranged to trigger a reading of clock 634 to
a capture register 633. The time stored in this way is hereafter
called Tref. Both the clock 634 and the capture register 633 can be
read by the microprocessor 635. Both 633 and 634 should
advantageously be able to be incorporated in 635. Program code is
stored in the memory 636 which, for example, is run each time 635
receives an SOF packet from 631. The program can, for example, read
off the frame number on the SOF packet and, depending upon the
requirements and conditions always or at certain intervals read out
Tref from 633 and send a new USB packet 652 using 631 via 602 to
601. 603 also contains interface electronics 637 for a CAN
controller 638 which, in turn, contains a precise detection
mechanism 638' for detecting when the CAN messages commence.
[0074] The detection mechanism 638' also triggers the capture
register 639 which then reads clock 634. The timestamp which is to
be found in capture register 639 can be sent, together with the
message that triggered the reading in a packet 653 to 601. The
packet type 653' can, for example, include USB overhead, 642 and
642'''', data, 642', from the CAN controller 638, a timestamp,
642'', of when the data 642' was received by 638, and if required
more data with associated timestamps, 642'''. The packet type 652'
contains, in addition to the overhead, 641, 641'''', that USB adds,
a Tref, 641', the sequence number of the SOF that gave rise to the
Tref, 641'', and, if required, more Trefs with associated sequence
numbers and/or other data, 641''''.
[0075] Computer or processor 601 is arranged with a USB host 671.
As already mentioned, 671 sends SOF packets 651 t regular intervals
in accordance with the USB protocol. When the computer receives
packets of the type 652 from its connected units 603, 603', etc.,
via the USB host 671, these can be read and processed by the
processor 672 using program code in the memory 673. Among other
things, program code according to the logical data flow chart in
680 is run in the processor. Unit 681 represents here the USB drive
routines that constitute a part of the operating system that
processor 601 utilizes. These contain, among other things, checks
on the physical structure of the USB system, and read out the data
packets from the controller 671. If these packets originate from
any of the units 603, 603', etc., they are forwarded via the
time-handling functions 682 to the drive routines 683 intended for
the purpose. If the messages are packets of the type 652, the
information 652' is retrieved from them, that is the so-called
Trefs 641', also the sequence numbers 641'' and any other data
641''', and they are taken charge of by the time-handling functions
682 which are a part of 683.
[0076] The system is, after all, also intended to be used and it is
represented here by a user application 685 which logically
communicates directly with the units 603, etc., but in practice
this is carried out via the commonly used interface 684 which
provides all the functions that a user can utilize in the units.
The interface 684 thus connects together the program 685 with
units' drive routines 683. The interface displays, for example, if
so required, all timestamps from the different units along one and
the same time axis, which is carried out using the time-handling
functions 682 completely in the spirit of the disclosure. In the
figure, this is exemplified by the message 653 sent from a unit 603
to 601. Unit 671 decodes the packet and forwards the content 653'
to the processor 672 for further processing. For example, unit 681
sees that the message originates from a unit of type 603 and
forwards it to the drive routines 683 intended for the purpose. The
time-handling functions 682 in 683 see that the message contains a
timestamp 642'' in a local unit's time, and so it translates this
to a suitable time according to, for example, the following
procedure. The translated time, 643', and any calculated inaccuracy
643'', are displayed together with data, 643, (that is 642'
possibly further processed by 683) and any other information
643'''', taken as a whole 653'', to the application 685 via the
interface 684.
[0077] The time-handling functions 682 can be divided into a part
that saves and handles a history 682' of Trefs with sequence
numbers that come from the packets 652' and information about the
originating unit and keep translation functions updated and a
second part that carries out the actual translations. In order to
be able to carry out direct translation between the times of all
units, a type of logical translation matrix 686 can be utilized.
For each pair of units 687, 687', etc., whose time is to be able to
be translated directly, there is a list 688 with most recently
matched pairs of Trefs 688', 688'', etc. These Trefs 688', etc.,
can then be utilized to carry out a translation between the times
of the comprised units, for example according to:
B.sub.x=B.sub.new+(B.sub.new-B.sub.old)*(A.sub.x-A.sub.new)/(A.sub.new-A-
.sub.old) or
B.sub.x=B.sub.new-(A.sub.x-A.sub.new)+(((B.sub.new-A.sub.new)-(B.sub.old-
-A.sub.old))*(A.sub.x-A.sub.new))/(A.sub.new-A.sub.old).
where A.sub.x is to be translated to B.sub.x using the matched Tref
pairs (A.sub.new, B.sub.new) and (A.sub.old, B.sub.old) which can
thus correspond to 688' and 688'''. As can be seen, there is a part
of the calculations that can be carried out in advance, for example
(B.sub.new-B.sub.old) and (A.sub.new-A.sub.old) in first
alternative and (B.sub.new-A.sub.new) and (B.sub.old-A.sub.old),
etc., in second alternative. Such calculations can, as stated,
advantageously be performed in advance and saved in a location 689
designed for the purpose in order to simplify and thereby speed up
future translations. Statistical inaccuracy concerned can also be
calculated and saved in a location 689' designed for the purpose.
It is, of course, possible to make an extremely complex and
exhaustive estimate of any inaccuracy on the basis of the whole
history of matched Tref pairs, but in order to give a simple
illustrative example, one of the Trefs in a pair 688' can, for
example, be translated using two other pairs in the list 688. The
translated Tref is then compared with the actual Tref in the pair.
The difference between them can be regarded as a simple measurement
of inaccuracy/non-linearity.
[0078] Another variant of the translation matrix can be to let a
row or column represent a virtual time, on the basis, for example,
of some weighting of suitable other times.
[0079] A simpler variant of the translation matrix is the special
case when only one or a few rows or columns in the matrix are kept
updated in the way mentioned above. As each row or column can give
information about how relating can be carried out from and to a
particular time, this time can be utilized as a kind of
intermediate master time in translation between two other times.
This can be a less memory- and/or resource-intensive alternative to
keeping the whole matrix updated at a cost of slightly more
complicated translations and/or possibly greater inaccuracy. The
intermediate master time here can constitute examples of the
function F1.
[0080] The time-handling or translation function F2/682 can be
broken down into a number of elements that, however, do not all
necessarily need to be carried out in each unit arranged with the
function. Certain elements can be carried out by one unit that then
sends the information to another unit that then does not need to
carry out the element. Examples of element functions include:
[0081] collecting and keeping track of time-stamped reference
function executions for each time that is to be able to be
translated. [0082] finding, from among the collected timestamps,
timestamps from different units of the same reference function
execution. [0083] determining, on the basis of these matched
timestamps, how any translation is to be carried out depending upon
given conditions. [0084] determining, on the basis of timestamps,
how stable/accurate a particular time can be considered to be, for
example using statistics. [0085] demanding, if a time is considered
to be unstable/inaccurate, more frequent timestamped reference
function executions from the system. [0086] carrying out
translations when so requested.
[0087] The time-handling functions can be considered to be an
example of the translation function F2.
[0088] In the systems, S1 can thus, for example, work with local
translation of time, S2 with centralized translation and S3 with
local synchronization. Of course, it is also possible to combine
different variants in one and the same system.
[0089] The event recognitions are to be arranged or are to form the
basis for or invoke functionality in the system, such as, for
example, analysis. Items of such functionality are represented in
FIG. 1 by F6 and F7.
[0090] FIG. 7 shows a simplified car system 900 that includes a
number of event-generating subsystems that are exemplified by a
motor 901, a gearbox 902, four wheels 903, 904, 905 and 906 and the
doors 907 and 908. Other Electronic Controller Units (ECU) that are
required for the car's functions are symbolized by 900'. Each
event-generating subsystem has an event-generating and
event-detecting ECU. The motor ECU 909, gearbox ECU 910 and the
wheel ECUs 911, 912, 913 and 914 are connected to the CAN network
915. The door ECUs 916 and 917 are connected to the LIN network
918. The LIN master 919 is connected to both the LIN network 918
and the CAN network 915. A system-controlling and monitoring unit
or system module 920 is also connected to the CAN network. External
units such as diagnostics instruments, programming devices,
analysis instruments, etc., represented by 921, can be connected to
the system via the connector 922 and a connection cable 923.
Contact with external units 924 can also be carried out via the
radio unit 925 and the radio link 926 in the monitoring unit 920.
In a first stage, the monitoring unit 920 controls all the other
modules in a first time domain where no time is transferred before
a wake-up event is transmitted over the CAN bus. In this mode, the
system's energy consumption is very low. The monitoring unit itself
is in another low-consumption time domain where a time tick event
is generated by an internal clock 920', for example 10 times per
second. This event initiates listening for incoming signals from an
external unit 924, for example a signal concerning opening of
doors. If such a signal is detected, the monitoring unit sends a
wake-up signal over the CAN bus and all the ECUs change to a
respective local time domain which is suitable for CAN and LIN
communication and for internal event detection and event
generating. A command concerning opening doors is given to the unit
919, which in turn commands the units 916 and 917 to open the
doors.
[0091] The ECUs controlling rotating parts establish their own time
domains on the basis of the speed of rotation. In its simplest
form, time base events are generated by pulse-generating wheels 930
and a pulse-detecting device 931. In this example, a pulse is
generated with inverted sign by a sensor 932. The device 931
detects the pulse train 933 which is forwarded to the ECU 934 which
thereby creates a clock function 934' with a circular time base
with a time tick that corresponds to a rotation of 22.5 degrees.
Time is thus measured locally in past wheel angle units. If the
wheel stops, then the local time stops. The ECU 934 can control the
brakes 935. The time base varies with the speed of rotation of the
wheel compared to a time base based on the physical second. A
controlling unit 936 with a time base 937 based on the physical
second can give commands K1 to and receive reports R1 from the unit
934. By means of status reports from the four wheels, the unit 936
can determine how the wheels are moving relative to each other and
command them to increase or decrease the braking force while
turning. If a wheel locks, then the time there will stop and
reporting will cease. This situation is easily detected by the unit
936, partly by the other wheels reporting, and partly as a result
of an expected report in relation to the internal time domain not
having arrived.
[0092] More complicated time domains can be constructed when
expedient. The event generator 940 generates two pulses per
revolution with inverted sign and 45 degrees interval. These are
detected by the detector unit 941 and transferred to the local
translator or counter 942 in the ECU 943 via the link 944. The
generated time domain is shown as 945. The ECU 943 has an internal
clock 946 which generates the time domain 947. There is a pressure
sensor 948 in the system which gives pressure information in
discrete steps to the unit 943 via the link 949, where each step
can be regarded as an event. Passage of certain of these events can
be utilized in order to generate a time tick. The pressure sensor
is connected to a cylinder 950 in the motor 901. The ECU 943
controls the electrical valve arrangement 951. The local translator
942 compiles the information from the time domains 945 and 947 and
948 into a new time domain 952 that is suitable for valve control.
The control unit 953 gives control commands to the valve control
mechanism 951 via the link 954 in the time of the time domain 952.
The local translator 942 thereby obtains a clock function viewed
from the unit 953. In this way, a "virtual camshaft" can be
created, where the characteristics of the control algorithm are
changed by the time domain 952 being changed in accordance with
variations in speed of revolution and pressure.
[0093] A unit 921 can be connected to the system for analysis or
diagnostics. The various nodes can have stored in their memories a
translation algorithm that states how their respective time domains
are transformed to a linear time domain based on the physical
second. The instrument 921 can request that the respective modules
transmit the translation algorithms. This assumes that the utilized
HLP (Higher Layer Protocol) supports such a procedure. Otherwise,
the algorithms are to be found in the system's documentation.
Alternatively, the algorithms are stored in the system module
920.
[0094] FIG. 8 shows a schematic traffic-monitoring system. Traffic
control and traffic monitoring are an increasing problem in
society. Increasing numbers of cars are equipped with GPS and GSM
in order to make things easier for the car's driver. This
development is taking place largely independently of the social
problem. A simple solution to the problem is to standardize a fixed
local time domain for all cars and for the monitoring system to
work with time domains that vary geographically and according to
requirements. The cars are obliged to be equipped with GPS
receivers and transmitters linked to a communication network
determined by society and to use these to report their position
periodically, for example every ten seconds. If a collision occurs,
this is reported immediately, with information from relevant
collision-related sensors. The road network is covered by
communication cells 970, 970', 970'', etc., of a suitable size.
Each cell is served by a base station 971, 971', 971'', etc.,
connected to a cable-based (optical or copper) network 972. The
control and monitoring system is also connected to this, symbolized
by 973. A number of cars 974, 974A, 974B, 974C, 974D, 974E are
driving along the road 975. Every ten seconds, they transmit their
position according to GPS exemplified by 976, 976'. In addition to
position, additional information can be sent, for example speed,
estimated damage in the event of a collision, number of passengers,
etc., as an anonymous or identified transmitter depending upon
legislation. Each base station carries out a first processing and
compiling of data, for example the number of passing cars per
minute, accidents that have occurred, exceeding of speed limits,
etc., and compiles this in a report 977. Each base station is
allocated at least two local time domains by the unit 973, for
example a circular time domain with transit time of 1 minute and a
linear limited time domain, with a start time upon a particular
type of message being received from the cars, for example collision
messages that extend up to and include a transmitted report to the
unit 973. In this way, the utilization of the road communication
network is optimized. The traffic information arrives regularly
once per minute over the link 973, dispersed in time as the local
time domains are not synchronized with each other. In the event of
a collision, reporting is carried out immediately and can thereby
be dealt with quickly. The transmitted message from the damaged car
becomes a reference event between the system cars and the
monitoring system. 973 can, as required, change time domains, and
the bandwidth of network 972 can be made available for other
information, for example commercial communication. The cars' time
domains do not need to be related to the time domain of the
monitoring system. It can easily be seen that the concept of the
disclosure can be varied in many ways for controlling and changing
characteristics and relationships of systems to those of other
systems so that they will work together.
[0095] The disclosure is not limited to the embodiments described
above as examples, but can be modified within the framework of the
following claims and the concept of the disclosure.
* * * * *