Pendolino tilt system

[Bletchleyite]

I strongly agree. I always avoid coach K where possible. (likewise I've not travelled SP/First since Avanti took over.)

Not only do I find coach K cramped, I find the ride quality is very bad in my opinion, I believe due to how the tilting system works on the two driving vehicles on Pendolinos.

It has no vehicle in front to predict the degree of tilt from, so it tends to be considerably rougher, but only southbound (when it's at the front). Northbound it's A that has that issue.

As an aside, the APT didn't predict tilt from leading vehicles at all, each vehicle worked it out itself, which is one reason it made some people feel queasy. I find the front coach of a Pendo does to me if it's dark so I can't see the horizon.

That's not how TASS works, TASS sends signals to the Train Tilting Processor which sends instructions to each individual vehicle's tilting processor about when to tilt and by how much. They aren't "predicting the lead carriage".

In my understanding TASS (Tilt Authorisation and Speed Supervision) dictates the maximum safe degree of tilt without hitting stuff. The unit itself decides how far to tilt within that based on the use of a gyroscope, same as the APT did (the APT did not have TASS but instead had a more tapered body which meant that even if it fully tilted wrong-side it wouldn't hit anything, i.e. a fully tilted vehicle was pretty much within the profile of a Mk1 coach or similar). Each coach tilts based on readings from the coach(es) in front, but the front coach can't so the tilt is noticeably rougher.

 

[hexagon789]

As an aside, the APT didn't predict tilt from leading vehicles at all, each vehicle worked it out itself, which is one reason it made some people feel queasy. I find the front coach of a Pendo does to me if it's dark so I can't see the horizon.

The initial tilt system was indeed vehicle specific, but it was later updated to predict off the vehicle immediately in front by the time of the MkIII system.

That's not how TASS works, TASS sends signals to the Train Tilting Processor which sends instructions to each individual vehicle's tilting processor about when to tilt and by how much. They aren't "predicting the lead carriage".

The TTP (Train Tilt Processor) on A or K interprets the TASS signals and calculates when and by how much to tilt. This calcation is sent in turn to the VTP (Vehicle Tilt Processor) on the subsequent vehicles as to when and by how much they should tilt.

So essentially they predict off the information the leading vehicle's processor has received and calculated, rather than simply how the vehicle ahead has tilted, so yes a bit more nuanced.

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For anyone interested, the APT-P website has a good write up of the three APT tilt systems and those of the Pendolinos and Super Voyagers.

 

[hexagon789]

Each coach tilts based on readings from the coach(es) in front, but the front coach can't so the tilt is noticeably rougher.

Pendolino Tilt System

Sensor Unit Tilt (SUT)​

Two units are located on each leading bogie of vehicles A and K. The SUT contains gyroscopes to detect when the train is tilting and accelerometers to detect lateral acceleration of the train. This information is passed to the TTP which calculates the tilting angle for each car as it travels through the curve.

The SUT also measure the distance that the train has travelled between each balise and therefore knows when to expect another balise.

Train Tilting Processor (TTP)​

The TTP is actually the Vehicle Tilting Processor of the driving cab vehicle. It is activated to become the master TTP by the cab of that vehicle being active.

Receives data from the TASS balise about tilt authorities and speed profiles for the section of track ahead via the TASS vital computer.

Receives data from the Sensor Unit boxes on the leading driving bogies about the speed, cant angle and distance travelled.

Using this data the TTP calculates when the train has to tilt and by how many degrees. This constant stream of data is passed to the VTP on each vehicle.

The TTP constantly monitors the safe operation and behaviour of the tilt system ensuring, that if there are any problems, the train will fail safe, with the tilt system self centring and an emergency brake application if required.

Driver Unit (DRU)​

Receives data from the Vehicle Tilting Processor (VTP) informing it of when and by how many degrees the bogies controlled by the DRU have to tilt.

Activates the drive command on the bogie actuators to tilt the bogie bolster to the required angle of tilt.

Monitors the safe operation of the electro-mechanical system on the bogie and provides data back to the VTP.

On pantograph vehicles there is also a Driver Unit Pantograph (DRUP) which carries out the same functions and checks for the pantograph tilt mechanism.

 

[SansHache]

The TASS (Tilt Authorisation and Speed Supervision) balise fitted on the track transmits the maximum speed and Tilt authorisation status to the train mounted antenna for the next section. Where applicable this will be the Enhanced Permitted Speed for the train, providing tilt is active. The tilt computers on the train calculate the tilt angle required depending on the train speed and information from the on-board gyroscopes and accelerometers as explained above. If the train exceeds the speed limit or the tilt system fails the TASS system intervenes to reduce the speed automatically.
The TASS system does not control the tilt operation on individual vehicles, it only enables tilt authorisation (tilt allowed or not allowed) and supervises the maximum speed when tilt is enabled.

 

[pokemonsuper9]

I've never felt any sort of travelsickness on a Pendolino.
I don't even notice the tilt until I realise the view out of the window is at a bit of a weird angle.

Coach A used to be my favourite before I started using videos to get numbers down (reading them out loud) - obviously can't do that in the quiet coach.

 

[Bletchleyite]

As I understand it, APT went for perfect tilt whereas Pendo is deliberately slightly deficient so that the brain still gets the ‘I am tilting’ feeling to match the visuals and avoid motion sickness.

That's another reason, yes.

 

[cambsy]

I find the Pendolino ride very smooth, as the tilt system acts as extra damper, which improves the ride. The tilt is designed to not totally compensate for feeling of curving, so one doesn’t feel as queasy as reported on the APT. A lot was learned from foreign manufacturers, from the failure of APT, as to how to improve tilt ride etc, and which best system to use, either electric or hydraulic tilt actuation. Feel was really great shame that government at the time didnt just push bit further with APT, to iron out the remaining issues, then we would have been leaders in tilt systems rather than having to buy Pendolino from Alstom, and not a home grown train.

 

[Thames99]

Do drivers suffer from motion sickness at all? Being familiar with the line and able to see it in front of them would let them anticipate movements of the train, but I’m not sure if that helps to prevent symptoms or not.

 

[AlterEgo]

Do drivers suffer from motion sickness at all? Being familiar with the line and able to see it in front of them would let them anticipate movements of the train, but I’m not sure if that helps to prevent symptoms or not.

I've cabbed a few 390s and have to say it felt entirely intuitive when I did it. Though the tilt prior to entering the small DF portal at Linslade Tunnel is a bit hair raising!