Camber control for rail vehicles

Details Camber control for rail vehicles Camber control for rail vehicles

1999-07-29

2001-08-14

Morano, S. Joseph (Department: 3617)

Railway rolling stock

Trucks

Bogie

C105S453000

Reexamination Certificate

active

06273003

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a tilt control system for the body of a rail vehicle.
2. Brief Description of the Prior Art
In a known tilt control system of this type, as disclosed in DE 37 27 768 C1, a gyroscope for the detection of the rotational speed of the vehicle body and a speed sensor are provided, in addition to a lateral acceleration sensor, to generate a control signal for the curve-dependent tilt of the body of a rail vehicle. The output signals of the lateral acceleration sensor and the angle of rotation sensor are fed to identical electrical low-pass filters with a low cutoff frequency in order to remove primary signals with superimposed parasitic oscillation from the output signals. The filtered, rotation angle-dependent output signal of the gyroscope is multiplied by a signal derived from vehicle speed and acceleration due to gravity. Together with the filtered signal of the lateral acceleration sensor, the signals are fed to a tilt control device used for tilting the vehicle body, in dependence on the input values, about its longitudinal axis, relative to a running gear or bogie assembly supporting the vehicle body. The low-pass filters have a cutoff frequency of 2 Hz. The low cutoff frequency results in an undesirable electrical time delay of the output signal. In order to compensate for this disadvantage, which would delay the tilting action of the vehicle body with adverse results for ride comfort, the output signal is filtered by the low-pass filter and, as such, determines the tilt of the vehicle body and is joined by a correction signal. The correction signal results from multiple multiplication and addition, which is calculated from the rotational speed of the vehicle body about its vertical axis and from its speed of travel. This involves much technical effort and an increased possibility of errors. In addition, the cutoff frequency of the low-pass filters is high compared to the rate of increase of the lateral acceleration.
SUMMARY OF THE INVENTION
The invention is based on the problem of providing by suitable measures a tilt control system for the body of a rail vehicle, wherein the tilt control device is controlled with minimum delay while circuit design is simplified.
In a design of a tilt control system according to the invention, only the output signal of a lateral acceleration sensor is used to control the actuator arrangement of a tilt control device, effecting the tilting of the vehicle body. This signal is fed in its original form, noisy due to parasitic oscillation, to a characteristic element without filtration. In the characteristic element, at least one characteristic is fixed, in accordance with which an output signal value allocated to a defined input signal value is output. In this context, the input signal is weighted in a way to ensure that only a medium range is used to control the tilt of the vehicle body. The characteristic element may, in particular, be constructed on a digital basis, whereby associated output signal values are stored in a memory in dependence on the magnitude of the output signal of the lateral acceleration sensor. The characteristic of the characteristic element has an unweighted initial range, in which the input signal does not result in an output signal, i.e. the lateral acceleration in the vehicle body varies with the lateral acceleration at track level. In the next range, the weighted medium range, the characteristic element is defined as any monotonically increasing function. In particular, curve sections rising linearly in stages are chosen. At least one curve section must have enough slope to keep lateral acceleration in the vehicle body constant for this curve range. This compensates at least partially for the delay of the downstream low-pass filter. From a preset upper acceleration value, the characteristic element once again supplies an unweighted, constant output signal value, independent of the input signal, so that the lateral acceleration in the travelling vehicle body once again varies with the lateral acceleration at track level, there being no further tilting of the vehicle body. The initial range detected at track level preferably extends to approximately 0.4 m/s
2
and the weighted medium range from approximately 0.4 to 1. 6 m/s
2
. The output signal of the characteristic element may be either a converted lateral acceleration value or a value determining the set tilt angle of the vehicle body. This low-pass filter can have a cutoff frequency of less than 1 Hz. This cutoff frequency is preferably adjusted to approximately 0.2 Hz. Irrespective of the increased delay of the filter, the actuator arrangement reacts very fast, owing to the weighting function of the characteristic element, because the delay of the low-pass filter is at least partially compensated for. The low cutoff frequency of the low-pass filter results in a soft tilt variation at the vehicle body and a rounded characteristic transition at the beginning and end of the weighted characteristic range. By omitting any further sensors and associated filter and computing units, a simple tilt control system with excellent noise immunity is created, which can be implemented cost-effectively and with little technical effort.
The permissible lateral acceleration at track level is limited to values between 0 and 2 m/s
2
in the present context. The lateral acceleration in the vehicle body varies synchronously with the lateral acceleration at track level, up to approximately 0.4 m/s
2
, while being kept constant at approximately 0.4 m/s
2
in the medium range by the activation of the actuators of the tilt control system, followed by a further synchronous increase to approximately 0.8 m/s
2
in the range above 1.6 m/s
2
.
The control behaviour can be adapted to varying rail vehicle types by storing several optional families of characteristics in the characteristic element, which can be called up when installing the system on the rail vehicle or when a change in the tilt characteristic is desired. In a digital characteristic element, an input signal curve can be allocated its own group of memory locations with static data for each characteristic, or the data values in a group of memory locations can be changed in accordance with the required characteristic curve.


REFERENCES:
patent: 5775230 (1998-07-01), Joos
patent: 5784969 (1998-07-01), Steidl et al.
patent: 5943962 (1999-08-01), Birkhahn et al.
patent: 0557893 (1993-09-01), None
patent: 557893 B1 (1996-11-01), None

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