JP2006182231A - Wheel brake system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wheel brake system constituting an advanced robust control system effective for the case when all axles of a vehicle glide without using a slip ratio. <P>SOLUTION: A variable structure system observer presumes rolling friction coefficient by inputting a wheel speed of the vehicle and a brake cylinder pressure to the variable structure system observer. Control of the wheel brake system is performed by the presumed rolling friction coefficient. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wheel brake system for controlling the sliding of a wheel.

  A vehicle such as a railway vehicle or an automobile performs acceleration / deceleration by a force generated between a wheel and a surface (rail surface, road surface, etc.) in contact with the wheel. For example, in a railway vehicle, acceleration / deceleration is performed by a longitudinal adhesive force generated between a wheel and a rail. By controlling this adhesive force, it can be expected to prevent the vehicle from sliding, shorten the stopping distance, and the like. The rolling friction coefficient is obtained by dividing the adhesive force by the vertical load.

  Conventionally, in a vehicle brake system, it has been proposed to design a sliding control system using a sliding mode control theory by estimating an adhesion force between a wheel and a rail, which is difficult to measure, with a disturbance observer.

However, the conventional sliding control system based on the sliding mode control theory obtains the target wheel speed from the slip ratio (also called the slip ratio), which is the difference between the wheel speed and the vehicle speed divided by the vehicle speed, and follows this. It is a robust servo system.
Since this control system is based on the slip ratio, there is a possibility that sufficient performance cannot be exhibited when all the axes of the vehicle slide.

In order to construct a control system that does not use the slip ratio, it is necessary to estimate the rolling friction coefficient as a state variable. Generally, as an estimation method, there are a linear observer and a nonlinear observer.
However, linear observers are inaccurate when there are system parameter variations (eg, changes in the friction coefficient of the brake friction material) and disturbances (eg, changes in contact conditions with the rail). For this reason, an effective estimation mechanism for system parameter fluctuations and disturbances is required among nonlinear observers, and research on variable structure system (VSS) observers having robustness has been made (for example, non-observer) Patent Document 1).
The VSS observer is an estimation method that can compensate for robustness even in a system in which system parameter variations and disturbances exist, and has the smallest estimation error among various estimation methods.
Kenzo Nonami and Hiroki Tana, “Sliding Mode Control—Design Theory of Nonlinear Robust Control”, Corona, February 1999, p. 161-252

  However, what applied the VSS observer to the wheel brake system has not yet been presented.

  The present invention has been made in view of these points, and provides a wheel brake system that constitutes an advanced robust control system that is effective even when all the axes of a vehicle slide without using a slip ratio. The purpose is to do.

  In order to achieve the above object, the invention according to claim 1 is a wheel brake system for controlling a wheel using a variable structure observer, wherein the variable structure observer is caused by rolling friction from wheel speed and brake cylinder pressure. The coefficient is estimated.

According to a second aspect of the present invention, in the wheel brake system according to the first aspect, the variable structure observer is represented by the following equation.

  According to a third aspect of the present invention, in the wheel brake system according to the first or second aspect, the wheel is a wheel of a railway vehicle.

  According to the present invention, in a wheel brake system that controls a wheel using a variable structure observer, the variable structure observer estimates a rolling friction coefficient from a wheel speed and a brake cylinder pressure. Therefore, it is possible to configure a robust control system that is effective even when all the axes of the vehicle slide without using the slip ratio, and also against parameter fluctuations and disturbances.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
The wheel brake system according to the present embodiment constitutes a nonlinear robust control system. The control target of this control system is a brake system that is provided on a wheel of a railway vehicle and brakes the wheel. The brake system incorporates a variable structure system (VSS: Variable Structure System) observer (hereinafter referred to as a VSS observer).

ただし、Ａ−ＬＣの固有値は負であるように選ぶ。 First, the design of the VSS observer will be described. Consider a one-dimensional observer for reconstructing all state quantities from observable state variables among controlled state variables. The same-dimensional observer is expressed by the following equation (1), and an estimated value of the state variable x can be calculated.

However, the eigenvalue of A-LC is selected to be negative.

Further, since Equation (1) is a linear observer, the estimated value is inaccurate when there is a system parameter variation or disturbance. Therefore, the VSS observer of the following formula (3) is redesigned.

The switching function ν is expressed as the following equation (4).

At this time, the control side represented by the following equation (5) is adopted so as to suppress the high-frequency vibration induced by the high gain M.

Here, there is a method of selecting the observer gain L as the feedback gain F for optimal control as shown in the following equation (6).

However, P is a solution of the Riccati equation of the following equation (7) for an arbitrary Q> 0.

Next, in this embodiment, the state variable x and the input u are set as in the following equation (8). FIG. 1 shows a block diagram of a wheel brake system 1 according to an embodiment of the present invention. That is, the brake cylinder pressure p is used as an input signal to the VSS observer, and the wheel speed v _w and the rolling friction coefficient number μ are estimated by the VSS observer 3.

  The brake cylinder pressure p can generally be obtained from the following signal system. That is, when controlling the brake device for the railway vehicle 2, for example, a service brake command signal delivered to each railway vehicle as an electrical signal by the service brake command line is applied to each railway vehicle 2 by the brake notch operation of the service brake of the crew. In response, train speed, vehicle load, and power generation braking force are taken into account, the required braking force is calculated by the brake receiver, a brake control signal is output from this brake receiver, and this brake control signal is sent to the electropneumatic conversion valve. input. This electropneumatic conversion valve controls the pressure of the compressed air supplied from the supply air reservoir, and supplies the air pressure proportional to the current value of the brake control signal to the brake cylinder of the brake device. In this brake device, the traveling rail vehicle 2 is moved by pressing the control member against the tread surface of the wheel by the air pressure supplied to the brake cylinder or by sandwiching the brake disc provided on the wheel by the brake lining. It is designed to decelerate or stop by frictional force.

In the present embodiment, the system matrix A and the control matrix B are set as in the following equation (9).

Of the state quantities v _w and μ, the wheel speed v _w can be measured using a speed sensor or the like, and in the present embodiment, this v _w is treated as an observable state quantity. On the other hand, it is generally difficult to measure the rolling friction coefficient μ, and in the present embodiment, this μ is treated as a state quantity that is difficult to observe. Thus, the set v _w as the reference type observation matrix C following equation (10), assume a VSS observer for estimating the mu.

Therefore, the VSS observer 3 is expressed as the following expressions (11) and (12) by substituting the expressions (8) to (10) into the expressions (3) and (5).

  Therefore, the rolling friction coefficient μ can be estimated by sequentially calculating using the mathematical formulas (11) and (12). Then, the wheel brake system 1 of the railway vehicle 2 is controlled by the estimated rolling friction coefficient μ.

  As described above, according to the present embodiment, the observer is configured without depending on the slip ratio. The rolling friction coefficient μ can be estimated using the VSS observer 3, and the control of the brake system including the sliding control can be further advanced based on the robust control theory.

Next, in order to verify the effectiveness of the wheel brake system 1 configured as described above, a simulation was performed using continuous simulation software on a computer. The parameters used in the simulation are as shown in Table 1.

Further, Q and R adjusted to obtain a desired response are as follows.

Then, the next observer gain L is obtained from the solution of the Riccati equation.

Further, the matrix M ₁ satisfying the stability and the matrix M ₂ satisfying the reachability are set as follows, and ε = 0.03.

  The calculation results of the rolling friction coefficient are shown in FIGS. The result shown in FIG. 2 is a calculation result when the friction coefficient of the brake friction material is constant. In the figure, Real represents a theoretical value based on the beam model, and Estimated represents an estimation result based on the VSS observer 3. The rolling friction coefficient has a small estimation error, and it can be seen that the rolling friction coefficient is well estimated. Next, the result shown in FIG. 3 is a calculation result when there is a variation in the friction coefficient of the brake friction material. Although it has been difficult to estimate with the conventional technology, it can be seen that although the estimation accuracy is deteriorated as compared with the case where the friction coefficient of the brake friction material is constant, the estimation can be performed roughly.

In the above embodiment, the wheel speed is adopted as the state quantity of the wheel, but a wheel angular speed or the like may be adopted.
In addition, it is needless to say that specific detailed structures and the like can be appropriately changed.

It is a block diagram showing a schematic structure of a wheel brake system concerning one embodiment to which the present invention is applied. It is a figure which shows a result in case the friction coefficient of a brake friction material is constant in embodiment same as the above. It is a figure which shows a result in case the friction coefficient of a brake friction material fluctuates similarly.

Explanation of symbols

1 Wheel brake system 2 Railway vehicle 3 Variable structure system (VSS) observer

Claims (3)

In a wheel brake system that controls a wheel using a variable structure observer,
The variable structure system observer estimates a rolling friction coefficient from a wheel speed and a brake cylinder pressure. The wheel brake system according to claim 1, wherein the variable structure observer is expressed by the following equation.

  The wheel brake system according to claim 1 or 2, wherein the wheel is a wheel of a railway vehicle.

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