At
this juncture, the exiting carrier informs the packet of its intention to leave, effects
an “exit distance” with respect to
the contiguous carriers, engages the transfer rail and departs.
Passive
switches make any "exit distances" absolutely unnecessary. The usual headway
between vehicles is quite sufficient.
It
is quite likely that multi-directional switching
will be required with multi-line operation.
How
do you imagine it? 3, 4, 5 guide rails? It’s impossible because of the problem of
crossing of guide rails with wheel rails.
It
may in some instances be required to elevate the guideway.
We anticipate that this will be the exception;
in most instances the freeway itself, augmented by barriers and other devices, should be
sufficient.
It
is true only for DM, but not for PRT. PRT stations should be situated everywhere and not
just along freeways. I think that the system will be mixed both in America and in
Europe/Asia (DM+PRT), despite differences in the primary mode. DM in America (except
densely populated or congested areas or separate objects with many clients or employees),
but PRT + portable electric scooters in Europe/Asia (except remote suburbs). So the design
of the system can be identical in America and Europe/Asia. It would be much cheaper and
more successful to design, produce and sell the same elements for both American and
Europe/Asia. Transport problems in Europe/Asia are more serious than transport problems in
America. Therefore, PRT in Europe/Asia is a necessary step towards DM in America. I
believe that the combined efforts of leaders in American and European/Asian capitals
(especially Moscow) are necessary for the creation of DM + PRT.
All
operations on the main line must be at a constant
system speed.
I
do not see any reason to limit speed, if there are no objective reasons. Vehicles
certainly should use special lanes of queue and acceleration (before mainline) and lanes
of deceleration (before turn to another mainline or before station). But it does not mean
that speed on mainline should be fixed. It is necessary to ensure only that nothing (like
short acceleration lanes) slows down the stream of vehicles. The system with unstable
speed is easier and has higher average speed, throughput and reliability, than the system
with fixed speed.
Some
have suggested that a vehicle wishing to transfer depart the line completely, come to a complete stop, and is re-launched onto the new
line.
In
most cases vehicles transfer to another mainline without complete stop. At good conditions
they even do not reduce speed at all, if the radius of turn is big enough. In case of a
dense stream on mainline only, the queue may be formed and complete stop may be necessary.
As
the vehicle approaches a need to transfer, the velocity is adjusted to coincide with a
vacancy in the next line. However, to first
order, capacity is proportional to velocity; thus any appreciable reduction in velocity is reflected in a reduced
capacity.
It
is not so because 80% of vehicles go directly, and only 20% of vehicles join the queue for
transfer to another mainline. Therefore the capacity of lanes of queue and acceleration is
usually quite sufficient. Mr. Turnbull suggests a 50/50 split but I don't think it is the
best idea in all circumstances.
It
is not necessary to slow down the lanes of deceleration,queue and acceleration at all, if
it's possible to build the turns with a big radius (900 m for 150 kph, the length of the
90° turn is 1414 m). In this case,100% of the stream from the mainline can be
accommodated. Nevertheless, the lanes of deceleration (1736 m for 150 kph), queue
and acceleration (1736 M for 150 kph) for the possible complete stop. Some part of these
lanes can be situated at the turn. But usually in densely populated cities, there is not
enough space; therefore turns with this large a radius are not possible, while its
advantage is insignificant (some tens of seconds).
If
we have one 150 kph lane of mainline in each direction, then the turn with a radius
of 100 m will allow 50 kph and a 50/50 split, but the turn with a radius of only 9 m will
allow 15 kph and average a statistical 80/20 split.
If
we have two 150 kph lines of mainline in each direction, then 50/50 split requires a
radius of 900 m for one switching lane, but an average statistical 80/20 split
requires 30 kph and a radius of only 35 m.
However
it is necessary to get rid of automobile stereotypes. There is no need to wait for vacancy
in the mainline all day, if it is possible to slow down slightly the stream on this
mainline (i.e. temporary large headway instead of permanent inter-packet headways) when
the queue length or waiting time becomes too big. The system must allocate priorities to
vehicles from both directions in advance (“Updating of priorities of vehicles” block
at my block diagram “Algorithms of PRT/DM control system”). The necessary
slot for entrance on mainline will be created by the assignment of higher priority to a
vehicle from a lateral direction (“Updating of priorities of vehicles” block
at my block diagram “Algorithms of PRT/DM control system”) and by
preliminary creation of a safe distance between the vehicle with a low priority from
mainline and this vehicle from a lateral direction (“Approaching to leading vehicle” block at my
block diagram “Algorithms of PRT/DM control system”). As there is no
direct visibility of the vehicle from lateral direction, the information on it is
transmitted by system to the vehicle with a low priority from mainline.
We
believe that adjusting velocity on the main line to accommodate the next transfer creates
control problems of significant proportion. This
requires that a central control authority must know
the exact location and velocity of each vehicle under its control, and issue
instructions accordingly. Moreover, this approach does not really provide for uninterrupted journeys.
Yes,
the system must know the exact location and velocity of each vehicle under its control. It
is not a problem. The information about concrete vehicles, in most cases, circulates
inside the corresponding controlled district. It goes from vehicles and from the guideway
to the district server. The district server transmits information to those vehicles,
which need this information to prevent collisions. The size of controlled districts is set
so as to manage this information flow.
By
the way, Mr. Turnbull demands that periodic track-side sensors provide real-time position
and velocity data [about packets] throughout the system. His system would have to keep
track of each vehicle which is leaving or joining the packet, and also track the first and
last vehicle in every packet. But the work of forming, merger, routing, division and
disbandment of packets would also arise. The lack of information about every vehicle
prevents the system from sending commands (about emergency braking, for example) to every
vehicle in a packet.
As
before, it we do not require a specific slot,
considerable advantage obtains. Let’s
consider the next step and require only a non-specific vacancy in a specific packet.
There
is no need to plan either specific slots between concrete vehicles, or non-specific
vacancies in specific packets on all route. Besides, such a task is too burdensome for
servers of the system.
It
is enough to plan the number of vehicles going
through segments
of lines in future minute intervals (“Current distribution of transport network capacity”
block at my block diagram “Algorithms of PRT/DM control system”). It
allows planning a route for a concrete vehicle (“Routing algorithm” block at my block diagram
“Algorithms of PRT/DM control system”) to prevent congestion. Every
new planned route of a concrete vehicle increases the planned loading on corresponding
lines (“Current
distribution of transport network capacity” block at my block diagram
“Algorithms of PRT/DM control system”). Routes may not be planned on the
overloaded lines (analogue of entrance quotas). All these calculations are made before the
departure of vehicles from the station.
All
one needs is an auxiliary (i.e., off the main line) transfer line which allows individual
vehicles to slow and slide back the appropriate
number of slots.
That
is, the same queue, about which I wrote above, is offered. It is the only opportunity to
push an irregular stream of vehicles into a line of limited capacity.
The
carrier makes many of its own decisions,
including initiating the transfer to other lines…
While it lacks authority to launch on the system.
My
approach is similar. The function of planning a route (“Routing algorithm” block at my block diagram
“Algorithms of PRT/DM control system”) and the function of priorities
allocation (“Updating
of priorities of vehicles” block at my block diagram “Algorithms of PRT/DM
control system”) should be carried out by district servers of the system,
instead of the highly specialized onboard computer of the carrier.
The
following functions should be carried out by the highly specialized onboard computer of
carrier:
· “Approaching to leading vehicle”,
· “Going after leading vehicle”,
· “Speed limitation and stop”,
· “Emergency braking”,
· “Interfaces and triple-modular redundancy”
(including steering according to the planned
route).
See
these blocks at my block diagram “Algorithms of PRT/DM control system”.
The
operations-model must be sufficiently flexible to accommodate differing traffic patterns,
seasonal variations, and (predictable) emergencies. In fact there is no single model. A specific scenario is designed for each specific
traffic pattern, or a specific event, or series of events. As each will have been
previously downloaded to the entrance stations, it is only necessary for the central
authority (computer or otherwise) to designate the specific scenario and time of execution
to alter the system.
This
is unnecessary. In any case it is desirable to be guided by standard criteria when
planning a route. That is minimal duration of trip, comfortable longitudinal accelerations
and decelerations, avoidance of congestion and observance of speed limits (taking lateral
accelerations into account) on different segments of lines. There are effective enough and
fast mathematical algorithms for this purpose (“Routing algorithm” block at my block
diagram “Algorithms of PRT/DM control system”). All these calculations
are made before the departure of vehicles from the station.
It
would be impracticable to allocate destination quotas for the entire system at each
station. Thus… quotas apply only to the initial
transfer.
This
approach does not take into account the fact, that the vehicles after initial transfer
will go to different destinations, and the loading of the next segments of lines along the
vehicles’ routes will not be controlled. Besides, the vehicles from different
stations can go along the same route from the certain point. That is, quotas should not be
attached to the initial transfers. Therefore, Turnbull had to search for palliative
solutions like a quota for the first two transfers and like virtual lines via several
transfers. It would considerably complicate the control system, as it is hard to consider
all possible variants of quotas of the second level. Besides, there would be a problem of
transfer of the unused quotas of second level. Not all cities have as convenient layout as
the layout of Los Angeles, and in these cities the number of transfers along the route may
be quite large. The competing algorithm of planning loading of segments of lines is almost
as simple, but has no such disadvantages.
The
packet will slow as a single entity. Moreover,
by concentrating all excess space between the packets; aside from facilitating entry, we
also provide room for following packets to
execute emergency braking.
Unlike
a train, a packet has no common pneumatic brake pipe. Therefore all vehicles in packet
will brake independently from each other and will be hitting by couplers or bumpers. The
situation is even worse, if the command to brake is transferred along the line from each
vehicle to the next (as suggested by Mr.Turnbull). Add the time for processing the
information in the onboard computers of all vehicles sequentially, for setting of
connection, log on, transmitting, encryption and decryption and so on. In case of a crash
all packets will be damaged, instead of a few vehicles which did not have enough time to
execute emergency braking and to stop to the common command of the system.
The
communication is basically only from one station to the next in line… This makes an easy case for
scalability.
This
means that both stations and vehicles know nothing about the loading of segments of lines
along the route before departure. They have constant, rigid and arbitrary interline quotas
only. They also know nothing about faulty segments of lines. These are powerful
disadvantages. The average length of a route (20 km) is not too long to refuse the
communication with all district servers along the route. It will take not more than a few
seconds before the departure of the vehicle from the station. Mr.Turnbull's provision for
emergency interruption of faulty lines requires that each station should posses the means
to communicate with the longest trip that might be encountered. So I don't suggest using
any additional instruments.
Thus
an onboard computer is required for this task. We
anticipate the central processor of almost any
present-day PC would be more than adequate.
Only
the self-murderer will board the vehicle under control of PC's central processor! It is
necessary to use a specialized onboard computer without a hard drive and without a GUI,
but with triple-modular redundancy. It will be something like airborne computer of jet
plane or ballistic missile. And onboard computer should be designed in Moscow, but not in Silicone Valley. In this case it will be much
safer, especially in an emergency. I mean that some Moscow R&D institutes have
(besides perfect instruments,excellent experience, knowledge, versatile education and
creative ability among the staff) the more fundamental approach and special cultural
standard, based on strict traditions and relations. The missile had to fly absolutely
reliably at any price, despite any emergency conditions and irrespective of contract
clauses. In a strict socialist/military structure nobody was interested in easy profit,
misleading customers, or producing obviously unreliable products for an undemanding
public (like MS Windows) and so on. The best people were selected for these R&D
institutes. Many of them did not leave during bad economic conditions and they still work
there despite the brain drain.
The
platform of the carrier… need only be rugged
enough to carry that type of load.
I
think that it is necessary to securely bind the vehicle automatically to the carrier, and
also to connect to power supplies automatically. It is a rather difficult problem if you
try to keep a support on wheels of carried vehicle.
To
minimize contact with high voltage power, the power for operation within stations is supplied from an onboard battery.
Good
idea!
In
emergency application, the friction forces can be augmented by means of the
guidance apparatus. When pulled into contact
with the guidance rail, considerable
additional braking forces can be provided.
The
transfer guidance rails at switches cannot be used for emergency braking, because they are
asymmetrical.
The
center guidance rail cannot be used for braking when switching to the lateral direction.
So the braking mechanism must be evacuated for the rail in such situations and, therefore,
this mechanism will be rather complicated.
It's
too expensive to have separate center guidance/braking rail along the whole mainline. So
it's a hardly possible, while attractive suggestion.
Guidance
arms extend downward from the carrier and have the means to “grasp” the rail. We use the term grasp in quotation marks because,
in normal operation, there is no physical contact
with the rail. In practice, the lower part of the arm is maintained in proximity to
the guidance rail with its position relative to the rail sensed electronically. The position of the guidance arm does not directly
control steering. The arm is allowed to
follow the normal variations in track position, while the high frequency movement is
damped out by the steering system, providing
a smooth ride to the passengers.
There
is no need for an electronic steering system like ULTRA's steering system. All the
vibrations from steering rollers can be damped by the horizontal shock-absorbers.
