PAREP
Robust Automatic Piloting under Stopping-Skidding Stress
The control system for trains, metros and streetcars includes an anti-skid and anti-wheel-slip device.
This device is active in both manual and automatic driving and intervenes as soon as wheel slip or wheel lock is detected.
The measurement and calculation period of the control command system is less than 30ms.
ATC (Automatic Train Control) is the signaling system made up of an ATP (Automatic Train Protection) safety subsystem and an ATO (Automatic Train Control) autopilot system. ATP ensures safe train operation by checking the train's speed against the maximum authorized speed, as well as its ability to brake and stop ahead of any danger point. The ATO sends commands to the train: this is a high-level control system, which can be seen as a subsystem replacing the driver. The measurement and calculation period of the ATC is of the order of 100ms to 300ms.
At the ATC level, the kinematics observers are coded wheels, mounted on the train wheels. Accelerometers may also be considered.
During an anti-skid condition, displacement, speed and acceleration measurements are altered. When the anti-skid device "corrects" the phenomenon, the measurements are also inaccurate.
Skid protection is a key factor in the success of an anti-skid system.
To ensure safety, ATP takes margins into account, including increased speed in the case of clutching and reduced displacement in the case of slipping. In automatic driving, the ATO does not control clutching and slipping, a task devolved to the train control system; to ensure efficient steering, it tries to drive within the limits of adhesion.
.The margins taken by the ATP and ATO lead to a reduction in the performance and transport capacity of the signaling system.
The study consists, on the one hand, in proposing a finer kinematics measurement, with the possibility of soliciting a smaller computation period and, on the other hand, in defining an ATO control that is robust to jamming-skidding. Thanks to this control, ATP increments/minorities will be more limited in time and amplitude, and performance should be improved. For example, the autopilot should not be in opposition to the anti-skid actions and should limit their solicitation as much as possible.