EP3040251B1

EP3040251B1 - Method of decreasing lateral pressure in railroad vehicle

Info

Publication number: EP3040251B1
Application number: EP14839442.2A
Authority: EP
Inventors: Masaaki Mizuno; Osamu Goto; Satoshi Kikko; Takuji Nakai
Original assignee: Nippon Steel and Sumitomo Metal Corp
Current assignee: Nippon Steel Corp
Priority date: 2013-08-28
Filing date: 2014-08-27
Publication date: 2018-10-17
Anticipated expiration: 2034-08-27
Also published as: CN105492291A; TW201522139A; CN105492291B; TWI558593B; JP6436214B2; ES2706741T3; WO2015030061A1; JPWO2015030061A1; JP6292237B2; EP3040251A1; JP2018012501A; EP3040251A4

Description

TECHNICAL FIELD

The present invention relates to a method of reducing a load in a lateral direction (a lateral force) that acts on a wheel of a railroad vehicle when traveling, with the aim of achieving enhanced safety.

BACKGROUND ART

When traveling in a curved section, a lateral force acts on a wheel of a railroad vehicle (see FIG. 10 (c)). It is advantageous to reduce the lateral force as much as possible, because the more the lateral force increases, the greater is the risk of derailment of the railroad vehicle.
There is a positive correlation between the lateral force and a curvature of a track in a curved section, and the smaller the radius of curvature in a curved section, the greater the lateral force that steadily arises. This steadily arising lateral force (see FIG. 10 (a)) is referred to below as a steady lateral force.
On the other hand, a high lateral force occurs instantaneously as a result of track irregularities such as an alignment irregularity (unevenness in a longitudinal direction on a rail side surface) (see FIG. 10 (b)). A lateral force that occurs instantaneously as a result of track irregularities such as an alignment irregularity is referred to below as a fluctuating lateral force.
Therefore, in order to enhance safety while traveling through curved sections, it is necessary not only to reduce the steady lateral force, but also to reduce the range of fluctuation of the fluctuating lateral force. It should be noted that fluctuating lateral force occurs not only in curved sections, but in straight sections as well.
Methods of reducing lateral force are disclosed in Patent References 1 and 2, wherein an actuator is installed between a vehicle body and a bogie, and the actuator is operated in response to a radius of curvature while traveling through a curved section.
According to the method disclosed in Patent Reference 1, a thrust capable of imparting a rotational force is generated in the actuator according to the radius of curvature. According to the method disclosed in Patent Reference 2, a thrust is generated in the actuator so as to reduce a lateral force that is directly measured.
However, in the methods disclosed in Patent References 1 and 2, the purpose for using the lateral force as an input value is to detect entrance into a curved section and to compensate for changes in the coefficient of friction, and no consideration is given to reducing the fluctuating lateral force that arises as a result of track irregularities such as alignment irregularity.
In Patent Reference 3, there is disclosed a method for estimating the lateral force exerted on eight wheels installed in a single vehicle and controlling a thrust generated by an actuator, by uploading track data such as track irregularities in advance, and by providing a vehicle state data storage device.
However, Patent Reference 3 does not describe a specific method for estimating the lateral force from track data such as track irregularities, nor does it describe in detail a method for determining the thrust generated by the actuator.
Moreover, the method disclosed in Patent Reference 3 requires the storage of track data in advance, because feed forward control for estimating the lateral force is based on track data stored in the vehicle and travel location data for the vehicle. However, erroneous control can occur in cases where errors in the measurement of travel location data (degree of distance) occur, or in cases where unsuitable track data is stored, as a result of idling or sliding when the vehicle is braking.
Patent Reference 4 discloses a railway bogie with a mounted vehicle body including a frame; a plurality of wheelsets and steering linkages linking the wheelsets so that the wheelsets can cooperate to be in steering alignment. The bogie has a wheelset body linkage pivotally connecting the steering linkages with the bogie body so to position the body relative to the wheelsets and two alignment rams to position the body relative to the frame. The bogie also has sensors for monitoring the yaw angle and yaw velocity. The sensor input is then processed to estimate track curvature and determine the train speed and yaw velocity of the vehicle body. The processor then actuates the alignment rams to adjust the position of the body relative to the frame in response to the track curvature and current frame positions to minimize wheel contact creepage and maximize bogie stability.
However, Patent Reference 4 does not disclose reducing the fluctuating lateral force arising from track irregularities during travel, on the basis of state quantities measured by sensors installed in a railroad vehicle.
Patent Reference 5 discloses the problem of reducing a delay in generation of operating force when controlling steering, and to reduce a steady deviation. The solution to this problem is a method of controlling a steering actuator 4 to be operated by an electrical command and provided between a vehicle body 2 and a bogie frame 1 of each of two bogies fitted to a front part and a rear part of the vehicle body 2 is structured so as to work in the rotating direction freely to rotate between the vehicle body and the bogies in the curving direction of a curve when passing through a curved section. As a command voltage to the actuator 4, a value obtained by adding the amount of friction resistance compensation, which is obtained by multiplying a direction (code) of any one of curvature speed, angular velocity of the bogie and speed of the actuator, by the friction force Fc of the actuator 4 itself, which is previously measured, is used. As a result, the outer rail side lateral pressure to be applied to a leading wheel axle when passing through a curved section can be reduced, and a reliable actuator can be realized at low cost.
However, Patent Reference 5 does not disclose reducing the fluctuating lateral force arising from track irregularities during travel, on the basis of state quantities measured by sensors installed in a railroad vehicle.
Patent Reference 6 relates to a vehicle having steerable axles. A track guided vehicle comprises at least one pair of independent wheel axles, and at least two members (14, 15) for measuring the transverse position of the vehicle relative to the track, and it is characterized in that it includes at least one measuring member (20) for measuring the angle of the axles relative to references related to portions of the vehicle, and at least two actuator members (21) for correcting said angles by bearing against said axles, and a servo-control circuit receiving the signals from said measuring members and generating control signals for said actuator members.
However, Patent Reference 6 does not disclose reducing the fluctuating lateral force arising from track irregularities during travel, on the basis of state quantities measured by sensors installed in a railroad vehicle.

PRIOR ART REFERENCES

PATENT REFERENCES

Patent Reference 1: Japanese Patent Application Kokai Publication No. 2002-087262
Patent Reference 2: Japanese Patent Application Kokai Publication No. 2004-161115
Patent Reference 3: Japanese Patent Application Kokai Publication No. 2012-166733
Patent Reference 4: WO 2008/101287
Patent Reference 5: Japanese Patent Application Kokai Publication No. 2007-186126
Patent Reference 6: U.S. Pat. No. 4,982,671

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

The problems that the present invention aims to solve are that in the methods disclosed in Patent References 1 and 2, the purpose for using the lateral force as an input value is to detect entrance into a curved section and to compensate for changes in the coefficient of friction, and no consideration is given to reducing the fluctuating lateral force that arises as a result of track irregularities. A further problem that the present invention aims to solve is that Patent Reference 3 does not describe a specific method for estimating the lateral force from track data such as track irregularities, nor does it describe in detail a method for determining the thrust generated by the actuator.

MEANS FOR SOLVING THESE PROBLEMS

The object of the present invention is to advantageously reduce the fluctuating lateral force arising from track irregularities during travel, on the basis of values estimated from state quantities measured by sensors installed in a railroad vehicle, without referring to track data stored in advance in a storage device or the like.
First, there is described the process undertaken by the inventors from conception of the invention to solving the above-described problems. The inventors conceived of reducing a lateral force that arises during travel, by installing sensors in a railroad vehicle, and using the values output by these sensors to control a thrust of an actuator according to state quantities that have a correlation with computed track irregularities.
According to the present invention, which is defined by the technical features and steps as set forth in independent method claim 1, an actuator that can control a thrust by inputting signals from the outside is installed between a vehicle body and a bogie of a railroad vehicle. In addition, sensors for measuring state quantities that have a correlation with track irregularities are installed in at least the vehicle body, the bogie, or the wheelset.
The state quantities measured by the sensors are converted to parameters (u_st1, u_st2, ...) that have a strong correlation to the track curvature, and the actuator thrust that is used to control the steady lateral force is determined from these parameters. If u_st1, u_st2 ... are parameters for steady lateral force control input, F1 is the output to the actuator for steady lateral force control, and G1 is a transfer function of the steady lateral force, then F1=G1(u_st1, u_st2 ...). The output F1 to the actuator for steady lateral force control is of course not generated while travelling through a straight section.
On the other hand, the state quantities measured by the sensors are converted to parameters (u_fl1, u_fl2, ...) that have a strong correlation to the track irregularities, and the actuator thrust that is used to reduce the fluctuating lateral force is determined from these parameters. If u_fl1, u_fl2 ... are parameters for fluctuating lateral force control input, F2 is the output to the actuator for fluctuating lateral force control, and G2 is a transfer function of the fluctuating lateral force, then F2=G2(u_fl1, u_fl2 ...).
Therefore, the total F of the output to the actuator for lateral force control when a railroad vehicle is traveling can be expressed by F = F1 + F2 = G1(u_st1, u_st2 ...) + G2(u_fl1, u_fl2 ...) (see FIG, 1).
The lateral force exerted on the wheels during travel is affected by a downward perpendicular force acting on the wheels and by the coefficient of friction between the wheels and the rail. Therefore, it is advantageous to obtain these values and add them to the state quantities for control input to the actuator.
Accordingly, the lateral force occurring while the railroad vehicle is traveling is obtained and separated into the steady lateral force and the fluctuating lateral force, state quantities having a strong correlation to each type of lateral force are measured, and the actuator thrust is controlled in accordance with these state quantities. This makes it possible to advantageously reduce the fluctuating lateral force that is thought to be caused by track irregularities, without using data pertaining to track irregularities during travel, and without using data pertaining to railroad vehicle travel location data.
The track curvature in a curved section is generally approximately constant, even if it is slightly affected by track irregularities while traveling in one particular curved section. Thus, the value of the steady lateral force is constant while traveling in one particular curved section.
Therefore, in the case of the parameters u_st1, u_st2 ... for steady lateral force input control, state quantities are selected that are approximately constant while traveling in one particular curved section, and the output F1 to the actuator for steady lateral force control is also a value that is approximately constant.
On the other hand, since the value of track irregularities changes due to the travel location of the railroad vehicle when traveling in one particular curved section, the value of the fluctuating lateral force changes in response to the value of track irregularities, and the output F2 to the actuator for fluctuating lateral force control also changes in response to changes in the value of track irregularities.
Consequently, in cases where only the output F1 to the actuator for steady lateral force control, which is approximately constant when traveling in curved sections, is generated as a thrust of the actuator, then the amount of decrease in lateral force is approximately constant, and there is almost no change in the magnitude of the range of fluctuation in the fluctuating lateral force.
On the other hand, in cases where only the output F2 to the actuator for fluctuating lateral force control is generated as the thrust of the actuator, then the range of fluctuation of the fluctuating lateral force becomes small. In other words, the lateral force decreases at sites where the lateral force is higher than the average value of lateral force when traveling in a single curved section, so the range of fluctuation of lateral force is reduced by increasing the lateral force at sites where the lateral force is low. However, the average value of lateral force undergoes almost no change.
Therefore, if the output F1 to the actuator for steady lateral force control and the output F2 for fluctuating lateral force control are both generated as the thrust of the actuator, then a thrust of the output F1 is constantly generated, and the output F2 undergoes change in response to the parameters u_fl1, u_fl2 ... for fluctuating lateral force control input.
In general, if a curved section has a relatively high track curvature (small radius of curvature), then the steady lateral force is high, and the fluctuating lateral force is lower than the steady lateral force. On the other hand, it is known that if a curved section has a relatively low track curvature (large radius of curvature), then the steady lateral force is low, but the fluctuating lateral force is higher than the steady lateral force. Accordingly, because there is a limit to the maximum thrust of the actuator. It is necessary to adjust the ratio of the output F1 to the actuator for steady lateral force control and the output F2 to the actuator for fluctuating lateral force control, so as not to be saturated by the maximum thrust.
If the transfer function of the steady lateral force G1 and the transfer function of the fluctuating lateral force are set so that the output F1 is greater relative to the output F2, then a constant lateral force reducing effect can always be expected. On the other hand, since the amount of reduction in the fluctuating lateral force decreases, there is no change in the range of fluctuation in the lateral force.
If the thrust of the actuator resulting from the output F1 is excessive, then the bogie rotates too much toward the inner side of the curved section. Therefore, a front wheelset having a flange contact between a wheel on an outer track side and a rail typically makes a flange contact on an inner track side and a rail, so there is a possibility of derailment on the inner track side.
On the other hand, if the transfer function G1 and the transfer function G2 are set so that the output F2 becomes greater relative to the output F1, then the fluctuating lateral force is reduced. In other words, the range of fluctuation of the lateral force is reduced. However, an elevated steady lateral force is maintained, because the amount of reduction in the steady lateral force is small.
Therefore, in the case of curved sections with a relatively high track curvature (the radius of curvature is relatively small), it is advantageous to set the transfer function G1 and the transfer function G2 so that the output F1 is greater than the output F2, thereby emphasizing a reduction in the steady lateral force.
On the other hand, in the case of curved sections with a relatively low track curvature (the radius of curvature is relatively large), it is advantageous to set the transfer function G1 and the transfer function G2 so that the output F2 is greater than the output F1, thereby emphasizing a reduction in the fluctuating lateral force.
One factor that determines the maximum traveling speed in a curved section is the value of the maximum lateral force that is generated while traveling through a curve. It is therefore necessary to lower the maximum lateral force so as to raise the maximum traveling speed in a curved section.
When the maximum lateral force is lowered to the greatest extent possible, for example, in cases where a reduction in friction between wheels and rails is emphasized, it is considered effective to reduce the average value of the lateral force generated while traveling in a single curved section. Therefore, it is advantageous to control the system so as to reduce the average lateral force while traveling in a curved section as much as possible, in other words, to increase the value of the output F1.
However, there is a limit to the maximum thrust of the actuator, and it is desirable to reduce the thrust generated by the actuator, due to factors other than the maximum thrust.
Viewed from the general standpoint of energy conservation, when a railroad vehicle travels through a particular curved section, for example, it is desirable that the average value per unit time of the thrust generated by the actuator be small. Furthermore, since the actuator itself has sliding parts, the operating time should be short, from the standpoint of increasing its useful life. This means reducing the average value per unit time of the thrust generated by the actuator.
In particular, in cases where a pneumatic actuator is employed that uses compressed air for its power source, a supply of compressed air is obtained from a compressor installed in the railroad vehicle. In this case, the compressor installed in the railroad vehicle is often selected from units that are as compact as possible, from the standpoint of reducing the weight of the railroad vehicle and saving installation space for underfloor equipment. Therefore, it is desirable to reduce the consumption of compressed air, and also to reduce the average value per unit hour of thrust generated by the actuator, because there are many cases where there are stringent limiting conditions on compressor capacity.
On the other hand, if an electric actuator is employed, cooling becomes a challenge in many cases, because heat is emitted due to the flow of current when the actuator operates. With regard to cooling, the heat-emitting capacity of the actuator itself is important, but this is also greatly affected by the environment in which it is used. Therefore, from this standpoint as well, it is desirable for the average value per unit time of the thrust generated by the actuator to be small.
In other words, from the standpoint of increasing the maximum traveling speed in a curved section, it is important to reduce the maximum lateral force, but on the other hand, there is a limit to the capacity of the actuator. In particular, if upper limits are set for the maximum value of thrust generated by the actuator and the thrust generated per unit time, it cannot be considered desirable to continue operating the actuator at a constant thrust that is always near the limit. Therefore, it is desirable for the output F1 to have a value lower than the capacity limit of the actuator, so as to have some thrust of the actuator left over, thereby generating a suitable amount of thrust which is close to the limit of the actuator at a point where a high fluctuating lateral force is generated.
The reason for installing an actuator is to impart a moment to a wheelset via a bogie.
In the case of a direct mount-type bolstered bogie, a side bracket is installed between a bolster and a bogie frame, which are structural components of the bogie, and it rotates between the bolster and the bogie frame. Therefore, if the actuator is installed on the vehicle body side, it is installed in the vehicle body or in a swing bolster. If the actuator is installed on the bogie side, it is installed in the bogie frame.
In the case of an indirect mount-type bolstered bogie, the side bracket is installed between the vehicle body and the swing bolster, and rotates between them. Therefore, if the actuator is installed on the vehicle body side, it is installed in the vehicle body. If the actuator is installed on the bogie side, it is installed in the swing bolster or the bogie frame.
Factors that significantly affect the lateral force occurring in the leading axle of a railroad bogie are: The downward perpendicular force acting on the wheels, the coefficient of friction between the wheels and the rail, the lateral creep ratio and the longitudinal creep ratio acting on the wheelsets, and the combined component force and centrifugal force induced by cant.
Among these, the downward perpendicular force acting on the wheels fluctuates greatly, depending on the passenger occupancy rate of the vehicle. This value can be estimated from a load-bearing value obtained using a secondary spring installed between the vehicle body and the bogie or a primary spring installed between the bogie and the wheelset.
In the case of a railroad vehicle using an air spring as the secondary spring, the load borne by the secondary spring can be converted from the inner force of the air spring. If the load is borne by the primary spring, and if mainly metal springs are used, then the load can be converted by measuring the displacement between the wheelset and the bogie frame.
The coefficient of friction between the wheels and the rail can be estimated from the ratio of the longitudinal load exerted on coupling members such as links which connect bogies and wheelsets in the longitudinal direction and the downward perpendicular force.
The longitudinal creep ratio can be obtained using FORMULA 1 below, and the lateral creep ratio can be obtained from FORMULA 2 below. $\begin{array}{l} v_{xl} & = \frac{γ}{r_{0}} y + \frac{ψ}{V} b \\ v_{xr} & = - (\frac{γ}{r_{0}} y + \frac{ψ}{V} b) \end{array}$

Where v_xl : Longitudinal creep ratio of a left wheel
v_xr : Longitudinal creep ratio of a right wheel
γ : Effective tread gradient of wheel
r₀ : Wheel radius
y : Lateral displacement of wheel
ψ : Yawing angular velocity of wheelset
V : Vehicle traveling velocity
b : Distance between contact points of left and right wheels and rail/2

\begin{array}{l} v_{yl} & = - ψ + \frac{\dot{y}}{v} + \frac{r_{0}}{v} ψ \\ v_{yr} & = - ψ + \frac{\dot{y}}{v} + \frac{r_{0}}{v} ψ \end{array}

Where v_yl: Lateral creep ratio of a left wheel
v_yr: Lateral creep ratio of a right wheel
ψ: Yawing angle of wheelset
ẏ : Lateral velocity of wheelset

In the longitudinal and lateral creep ratios shown in FORMULA 1 and FORMULA 2, the state quantities that can be measured while a vehicle is traveling are: Lateral displacement of the wheelset, lateral velocity of the wheelset, yawing angle of the wheelset, yawing angular velocity of the wheelset, and vehicle traveling velocity. Among these, the lateral velocity of the wheelset can be computed from the lateral acceleration of the wheelset.
If the spring constant between the wheelset and the bogie frame is sufficiently high, and if there is deemed to be a nearly rigid connection between the wheelset and the bogie frame, then the lateral displacement of the wheelset, the lateral velocity of the wheelset, the lateral acceleration of the wheelset, the yawing angle of the wheelset, and the yawing angular velocity of the wheelset can be substituted with the respectively corresponding state quantities on the bogie side.
The combined forces resulting from the component force due to cant and the centrifugal force generated while traveling through a curved section can be converted from the rolling angle of the vehicle and the time differential thereof, or from the height of the air spring which is a secondary spring.
Based on the above, the following are given as state quantities to be used when converting the parameters for steady lateral force control input u_st1, u_st2 ... and the parameters for fluctuating lateral force control input u_fl1, u_fl2 ...

Internal pressure of an air spring used as a secondary spring
Vertical displacement of a coil spring used as a primary spring
Longitudinal load exerted on a coupling member such as a link that connects a wheelset and A bogie frame in a longitudinal direction
Yawing angle, yawing angular velocity, yawing angular acceleration which occur in the wheel set, bogie, and vehicle body respectively, or lateral displacement, lateral velocity, and lateral acceleration
Vehicle traveling velocity
Rolling angle and rolling angular velocity
Height of an air spring used as a secondary spring

Here, the lateral displacement, velocity, acceleration, yawing angle, and yawing angular velocity of the vehicle body are compared with state quantities that are likewise generated in the bogie and the wheelset, and the weight and moment of inertia are large; and the vibration insulation properties between the bogie and the vehicle body are high due to a lateral damper, a yaw damper, and the like. Therefore, the amount of fluctuation in the lateral displacement, velocity, acceleration, yawing angle, and yawing angular velocity that occur in the vehicle body as a result of track irregularities become smaller than the amount of fluctuation that likewise occurs in the bogie and the wheelset. It is therefore thought effective to use state quantities on the vehicle body side to estimate the steady lateral force.
Moreover, it is possible to estimate the fluctuating lateral force by using a difference between the state quantities on the bogie side and on the vehicle body side, since the steady component of lateral force can be suitably excluded.
The method according to the present invention was devised by the inventors through a process from conception to solving the above-described problems, and the most salient features of the constitution of the invention are described below.

1) Installing an actuator in a railroad vehicle.
If the railroad vehicle is mounted with a bolsterless bogie, then the actuator is installed between a vehicle body and a bogie frame. If the railroad vehicle is mounted with a direct-mount type bolstered bogie, then the actuator is installed between the vehicle body and the bogie frame or between the bolster and the bogie frame. If the railroad vehicle is mounted with an indirect-mount-type bolstered bogie, then the actuator is installed between the vehicle body and the bolster.
2) Installing sensors in a railroad vehicle for measuring state quantities while traveling, in at least one of the following: The vehicle body, the bogie, and the wheelset.
State quantities measured while traveling include any of the following, which are factors that significantly affect the lateral force.
- Internal pressure of an air spring used as a secondary spring
- Vertical displacement of a coil spring used as a primary spring
- Longitudinal load exerted on a coupling member such as a link that connects a wheelset and a bogie frame in a longitudinal direction
- Yawing angles of a wheelset, a bogie, and a vehicle body, respectively
- Yawing angular velocity
- Yawing angular acceleration
- Lateral displacement
- Lateral velocity
- Lateral acceleration
- Vehicle traveling velocity
- Rolling angle
- Rolling angular velocity
- Height of an air spring
3) Converting in real time steady lateral force input control parameters having a strong correlation to steady lateral force from the above measured state quantities, and computing output commands to the actuator based on transfer functions for steady lateral force that are set in advance.
4) Converting in real time fluctuating lateral force input control parameters having a strong correlation to fluctuating lateral force due to track irregularities from the above measured state quantities, and computing output commands to the actuator based on the pre-set transfer functions for fluctuating lateral force.
5) Combining the output command values computed in 3) and 4), and the resulting command is sent to the actuator which is installed between the vehicle body and the bogie.

In the above description, a thrust is generated in the actuator installed between the bogie and the vehicle body, based on the values estimated by from the state quantities measured by the sensors installed in the railroad vehicle. It is therefore possible to effectively control the lateral force generated while the railroad vehicle is traveling, without referring to track data stored beforehand in a storage device or the like.

ADVANTAGEOUS EFFECTS OF THE INVENTION

According to the present invention, it is possible to effectively reduce the maximum lateral force generated while traveling, because the steady lateral force and the fluctuating lateral force generated while a railroad vehicle is traveling can be effectively controlled, thus making it possible to enhance the travel safety of railroad vehicles. Therefore, it is possible to increase the potential traveling speed in a curved section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing illustrating a control image of the method of reducing lateral force in a railroad vehicle according to the present invention.
FIG. 2 is a drawing illustrating an example of a control block line diagram of the method of reducing lateral force in a railroad vehicle according to the present invention.
FIG. 3 shows graphs illustrating the results of train running simulation of lateral force on an outer track side for a leading axle when a railroad vehicle travels in a curved section, where FIG. 3 (a) illustrates Condition 1, and FIG. 3 (b) illustrates Condition 2.
FIG. 4 shows graphs illustrating the results of a train running simulation of a lateral force on an outer track side for a leading axle when a railroad vehicle travels in a curved section, where FIG. 4 (a) illustrates Condition 3, FIG. 4 (b) illustrates Condition 4, and FIG. 4 (c) illustrates Condition 5.
FIG. 5 shows graphs illustrating results of a train running simulation of an added torque generated by an actuator when a railroad vehicle travels in a curved section, where FIG. 5 (a) illustrates Condition 1 and FIG. 5 (b) illustrates Condition 2.
FIG. 6 shows graphs illustrating results of a train running simulation of an added torque generated by an actuator when a railroad vehicle travels in a curved section, where FIG. 6 (a) illustrates Condition 3, FIG. 6 (b) illustrates Condition 4, and FIG. 6 (c) illustrates Condition 5.
FIG. 7 is a graph showing the maximum values for the added torque generated by the actuator in Condition 3 - Condition 5.
FIG. 8 is a graph showing the average and maximum values for the lateral force in Condition 1 - Condition 5, generated while a railroad vehicle travels in a circular curved section.
FIG. 9 is a graph showing the added torque per unit time in Condition 3 - Condition 5, generated while a railroad vehicle travels in a circular curved section.
FIG. 10 shows graphs illustrating changes in lateral force generated while traveling in a curved section, where FIG. 10 (a) illustrates steady lateral force, FIG. 10 (b) illustrates fluctuating lateral force, and FIG. 10 (c) is a wave diagram of actual lateral force computed by adding the fluctuating lateral force to the steady lateral force.

EMBODIMENT OF THE INVENTION

The object of the present invention, which is to reduce the lateral force generated while traveling, is achieved by estimating the steady lateral force and the fluctuating lateral force, on the basis of state quantities measured by sensors installed in a railroad vehicle, and generating thrust in an actuator installed between the vehicle body and the bogie, according to the estimated values.

EXAMPLE

Following is a description of results confirming the advantageous effects of the method of reducing lateral force in a railroad vehicle according to the present invention, through the use of train running simulations.
The railroad vehicle model used in the train running simulation was a typical two-axle bogie vehicle, and the track conditions included a curved section having a radius of curvature of 600 m. Track irregularities corresponding to a typical existing track were randomly produced, and the track irregularities were varied depending on the test conditions.
The actuator was mounted between the vehicle body and the bogie. In these simulations, actuator thrust was replaced with added torque between the vehicle body and the bogie. In addition, the state quantities used in estimating steady lateral force and fluctuating lateral force were the yawing angular velocity of the vehicle body, yawing angular velocity of the front bogie and the rear bogie, and the vehicle velocity. These state quantities were multiplied by the transfer functions of the applicable steady lateral force and fluctuating lateral force to determine the added torque to be applied between the vehicle body and the bogie, and these were then applied between the vehicle body and the bogie. FIG. 2 is a block line drawing for determining this added torque.
The five conditions for the train running simulations are given below.

(Condition 1)

Track irregularities: None
Transfer function multiplied by state quantities for estimating the steady lateral force: G1 = 0
Transfer function multiplied by state quantities for estimating the fluctuating lateral force: G2 = 0

(Condition 2)

Track irregularities: Present
Transfer function multiplied by state quantities for estimating the steady lateral force: G1 = 0
Transfer function multiplied by state quantities for estimating the fluctuating lateral force: G2 = 0

(Condition 3)

Track irregularities: Present
Transfer function multiplied by state quantities for estimating the steady lateral force: G1 > 0
Transfer function multiplied by state quantities for estimating the fluctuating lateral force: G2 = 0

(Condition 4)

Track irregularities: Present
Transfer function multiplied by state quantities for estimating the steady lateral force: G1 = 0
Transfer function multiplied by state quantities for estimating the fluctuating lateral force: G2 > 0

(Condition 5)

Track irregularities: Present
Transfer function multiplied by state quantities for estimating the steady lateral force: G1 > 0
Transfer function multiplied by state quantities for estimating the fluctuating lateral force: G2 > 0

Conditions 3-5 which give thrust command values yielding an added torque due to the actuator have the transfer functions G1 and G2 set so that the maximum values for the generated added torque are at approximately the same level, assuming the use of actuators possessing the identical capacity.
FIG. 3 to FIG. 9 give the results of the train running simulations.
When Condition 1 (FIG. 5 (a)), in which thrust command values are not output to impart an added torque generated by the actuator, is compared with Condition 2 (FIG. 5 (b)), it is found, as shown in FIG. 3 (b), that in the case of Condition 2, in which track irregularities are input, fluctuating lateral force is generated in addition to the steady lateral force shown in FIG. 3 (a).
On the other hand, it was found that, when Condition 3 (FIG. 6 (a)), in which the transfer function G1, obtained by multiplying the steady lateral force by the estimated state quantities, is greater than 0, is compared to Condition 2, the lateral force decreases at almost the same rate (see FIG. 4 (a) and FIG. 3 (b)).
Moreover, in the case of Condition 4 (FIG. 6 (b)), in which the transfer function G2, obtained by multiplying the fluctuating lateral force by the estimated state quantities, is greater than 0, there is an average lateral force on the same level as in Condition 2, but the lateral force decreases at a time when a large fluctuating lateral force is generated due to track irregularities (See FIG. 4 (b) and FIG. 3 (b)).
By contrast, when Condition 5 (FIG. 6 (c)), in which both transfer functions G1 and G2, obtained by multiplying the steady lateral force and the fluctuating lateral force by the estimated state quantities, are greater than 0, is compared to Condition 2, the lateral force decreases at almost the same rate, and the fluctuating lateral force can also be reduced (see FIG. 4 (c) and FIG. 3 (b)).
That is to say, in the case of Condition 3 to Condition 5, the maximum values for added torque generated by the actuator were nearly identical, as shown in FIG. 7. On the other hand, as shown in FIG. 8, the average lateral force is Condition 3 < Condition 5 < Condition 4. Although there are slight differences in the maximum values for lateral force, they differ by less than 5%, so they can be considered as about equal. As shown in FIG. 9, the added torque per unit time is Condition 4 < Condition 5 < Condition 3.
Therefore, the maximum values for lateral force under Conditions 3-5 can be considered as being about equal. Accordingly, we see that from the standpoint of enhancing the maximum travel speed in curved sections, the same level of performance is obtained under the control conditions given in Conditions 3-5.
Here, it is thought that if the conditions are such that the actuator thrust can be set at a high level, then an emphasis is placed on controlling wear on the wheels and the rail, so that the average value of lateral force generated when passing through a curve is reduced effectively. In this case, Condition 3 is advantageous for implementing the greatest reduction in the average lateral force (see FIG. 8). A condition that makes it possible to set the actuator thrust at a high level is, for example, if there is leeway in setting the capacity of the compressor installed on the vehicle side when a pneumatic actuator is employed. In the alternative, when an electric actuator is employed, it can be used in an environment in which a great amount of heat emission is anticipated.
Conversely, for the sake of convenience with regard to the conditions, if one wants to reduce added torque of the actuator per unit time, in other words, the thrust generated by the actuator, to the greatest extent possible, then it is advantageous to focus primarily on Condition 4 only to reduce the fluctuating lateral force (see FIG. 9).
Moreover, depending on the added torque conditions, such as in Condition 5, when an almost constant thrust is generated by the actuator during travel in curved sections, and when a large fluctuating lateral force is generated, it becomes possible to achieve control so as to further increase the actuator thrust to within a range of maximum thrust.
The present invention is not limited to the above-described example, and the preferred embodiment may, of course, be advantageously modified within the scope thereof as defined by the claims.
For example, in the above-described train running simulations, the railroad vehicle was the two-axle bogie type, but it is also likewise possible to employ a bogie car having a bogie between the vehicle body and the wheelset, regardless of the number of axles, since the actuator is installed between the bogie and the vehicle body.
Moreover, in the above-described train running simulations, the state quantities used in estimating steady lateral force and fluctuating lateral force were the yawing angular velocity of the vehicle body, the yawing angular velocity of the front bogie and the rear bogie, and the vehicle velocity. However, the yawing angle of the wheelset, the bogie, and the vehicle body and/or the yawing angle of the wheelset may be used instead, as long as steady lateral force and fluctuating lateral force can be estimated. In addition, any of the following may be used: The internal pressure of an air spring, the vertical displacement of a coil spring, the longitudinal load acting on links which connect bogie frames and wheelsets in the longitudinal direction, or the lateral displacement of the wheelset, bogie, and vehicle body, the lateral velocity, the lateral acceleration, as well as the rolling angle, rolling angular velocity, and height of the air spring.
The above-described train running simulations were performed while traveling in a curved section, but it is also possible to reduce a fluctuating lateral force that occurs instantaneously as a result of track irregularities while traveling in a straight section.

Claims

A method of reducing lateral force in a railroad vehicle, comprising:
installing an actuator
(i) between a vehicle body and a bogie frame if the railroad vehicle is mounted with a bolsterless bogie,

(ii) between the vehicle body and the bogie frame or between the bolster and the bogie frame if the railroad vehicle is mounted with a direct-mount type bolstered bogie,
or

(iii) between the vehicle body and the bolster if the railroad vehicle is mounted with an indirect-mount-type bolstered bogie;

installing sensors in at least one of the vehicle body, the bogie, and the wheelset;

on the basis of state quantities obtained by using the sensors while traveling,

computing one or more parameters (u_st1, u_st2, ...) having a correlation with a steady lateral force, to determine a thrust command value (F1) to be output to the actuator, by applying a predetermined transfer function (G1) to the computed parameters (u_st1, u_st2, ...), characterised by, concurrently with determining the thrust command value (F1), computing one or more parameters (u_fl1, u_fl2 ...) having a correlation with a fluctuating lateral force, to determine a thrust command value (F2) to be output to the actuator, by applying a predetermined transfer function (G2) to the computed parameters (u_fl1, u_fl2 ...); and

combining these two thrust command values (F1, F2) to determine the thrust output (F) to the actuator.
The method of reducing lateral force in a railroad vehicle according to Claim 1, wherein the state quantities obtained during travel are any of:
(a) an internal pressure of an air spring used as a secondary spring, (b) a vertical displacement of a coil spring used as a primary spring, (c) a longitudinal load exerted on a coupling member that connects a wheelset and a bogie frame in a longitudinal direction, (d) a yawing angle, a yawing angular velocity, or a yawing angular acceleration, respectively, of a wheelset, a bogie, and a vehicle body, or (e) a lateral displacement, a lateral velocity, a lateral acceleration, or a vehicle traveling velocity, or (f) a rolling angle, a rolling angular velocity, or a height of an air spring.
The method of reducing lateral force in a railroad vehicle according to claim 1 or claim 2, wherein the thrust generated by the actuator depends on a track curvature estimated according to the state quantities obtained during travel, such that the lower the track curvature, the lower the thrust command value (F1) in the case of a transfer function (G1) for the steady lateral force parameters (u_st1, u_st2 ...), and the higher the track curvature, the lower the thrust command value (F2) in the case of the transfer function (G2) for the fluctuating lateral force parameters (u_fl1, u_fl2 ...).
The method of reducing lateral force in a railroad vehicle according to claim 3, wherein
in the case of a higher track curvature, the thrust command value (F1) relating to the steady lateral force parameters (u_st1, u_st2 ...) is greater than the thrust command value (F2) relating to the fluctuating lateral force parameters (u_fl1, u_fl2 ...), and wherein
in the case of a lower track curvature, the thrust command value (F2) relating to the fluctuating lateral force parameters (u_fl1, u_fl2 ...) is greater than the thrust command value (F1) relating to the steady lateral force parameters (u_st1, u_st2 ...).
The method of reducing lateral force in a railroad vehicle according to any one of claims 1 to 4, wherein computing the fluctuating lateral force parameters (u fll, u_fl2 ...) comprises taking a difference between state quantities measured in the vehicle body and state quantities measured in the bogie.
The method of reducing lateral force in a railroad vehicle according to claim 5, wherein the state quantities measured in the vehicle body and the bogie are state quantities in a lateral direction and in a yawing direction, respectively.
The method of reducing lateral force in a railroad vehicle according to any one of the preceding claims, wherein the thrust output (F) to the actuator is determined without referring to track data stored in advance in a storage device.