Patent Publication Number: US-6902488-B2

Title: Lateral steady acceleration simulation system for railway vehicle

Description:
TECHNICAL FIELD 
   The present invention relates to a lateral steady acceleration simulation system for simulating lateral steady acceleration generated when a railway vehicle runs around a curve or the like. 
   BACKGROUND ART 
   In order to improve the riding quality of a railway vehicle, it is essential to accurately evaluate vibration and acceleration, which variously change depending on conditions of railroad tracks and vehicles, from the viewpoint of passengers. Such evaluation could be made by carrying out a running test, by means of an experimental vehicle, between runs by commercial vehicles. In this case, however, some problems arise as follows. 
   First of all, it is not easy to equalize the conditions of vehicles and tracks all the time running tests are performed, and reproducibility is not good. This fact results in a low reliability of evaluation. Also, it is difficult economically, and in view of efficiency as well, to shorten an interval of running tests or to carry out running tests a number of times. This fact results in a long period of development. Furthermore, it is not easy to modify conditions such as performance, properties, and the like. 
   On the other hand, there is known a system for simulating the riding quality without relying upon such running tests by use of experimental vehicles; that is, a simulation system by means of a simple four-axis vibration table for generating vibration along an up-down axis, a left-right axis, a forward-backward axis, and a roll axis (i.e., rotary motion about the forward-backward axis) (for example, refer to p.p. 113 to 116 of  Ergonomics , vol. 33, 1997) This simulation system is capable of simultaneously generating vibrations along a plurality of axes arbitrarily selected among the four axes. According to such a simulation system, the aforementioned problems with the running of the experimental vehicles could be resolved. 
   However, no system for simulating lateral steady acceleration, which is generated when a railway vehicle runs around a curve, has yet been known. 
   Such a lateral steady acceleration simulation system could be realized by utilizing acceleration generated by moving a simulated passenger room in the left or right direction. In the case of a long-distance curve, however, a railway vehicle is subjected to the lateral steady acceleration for a long period of time. In order to simulate such a long-period lateral steady acceleration, extremely long rails extending in the left and right directions are required. This means that the size of the entire system needs to be large. 
   SUMMARY OF THE INVENTION 
   The present invention was made to solve the aforementioned problems; and more particularly, the object of the invention is to provide a lateral steady acceleration simulation system for railway vehicle, which is capable of simulating a situation in which the lateral steady acceleration is applied to a railway vehicle for a long period of time, while having a compact structure. 
   In order to attain the aforementioned object, there is provided a lateral steady acceleration simulation system for railway vehicle comprising: 
   a simulated passenger room simulating an interior of a railway vehicle; 
   a base for supporting the simulated passenger room; 
   roll application means provided between the base and the simulated passenger room, the roll application means being capable of applying to the simulated passenger room at least rolling movement about a forward-backward axis; 
   laterally moving means for moving the base in either of the left or right direction; and 
   control means for controlling the roll application means and the laterally moving means; wherein 
   the control means makes control in such a manner that the simulated passenger room is rotated and inclined about the forward-backward axis by means of the roll application means, thereby causing to a person riding on the simulated passenger room a first reproductive acceleration that is a component force, along an inclined plane, of gravitational acceleration, and also in such a manner that the base is subjected to accelerated motion in either of the left or right direction by means of the laterally moving means, thereby causing a second reproductive acceleration to the person riding on the simulated passenger room, the first and second reproductive accelerations both being utilized to simulate lateral steady acceleration on a railway. 
   According to the simulation system of the invention, the lateral steady acceleration on the railway is not simulated only by utilizing the acceleration bodily sensed by the person riding on the simulated passenger room by means of the accelerated motion of the base integrated with the simulated passenger room. In addition to such acceleration, the acceleration bodily sensed by the person riding on the simulated passenger room by means of the rolling movement (rotation) and inclination of the simulated passenger room is also utilized, thereby simulating the lateral steady acceleration on the railway. 
   Therefore, according to the simulation system of the invention, even in cases where a railway vehicle is subjected to the lateral steady acceleration for a long period of time, for example, in the case of running through a long-distance curving section of a railroad track, such a long-period lateral steady acceleration can be simulated by utilizing the acceleration bodily sensed by the person riding on the simulated passenger room by means of the inclination of the simulated passenger room as well as the acceleration bodily sensed by him/her by means of the accelerated motion of the simulated passenger room. In this case, it is not necessary that the simulated passenger room should be moved such a long distance in the left or right direction. As a result, the simulation system of the invention is capable of simulating a situation in which a railway vehicle is subjected to the lateral steady acceleration for a long period of time, while having a compact structure. 
   In the lateral steady acceleration simulation system of the invention, it is preferable that the control means sets angular acceleration or angular velocity, in making the simulated passenger room roll about the forward-backward axis by means of the roll application means, within a range in which the rolling movement is not recognized by human beings. In this manner, in spite of the fact that the simulated passenger room is actually rotated, the person riding thereon is not aware of its rotation, and thus, he/she does not have a strange feeling about the riding quality. The aforementioned range may be experientially determined in advance. 
   In the lateral steady acceleration simulation system of the invention, it is preferable that the control means compensates for insufficiency of the first reproductive acceleration with the second reproductive acceleration, thereby simulating the lateral steady acceleration on the railway. In other words, in simulating the lateral steady acceleration on the railway, the first reproductive acceleration is mainly utilized, and the second reproductive acceleration is utilized for the purpose of compensation therefor. In this case, the rate of the second reproductive acceleration in the lateral steady acceleration to be simulated becomes smaller and, consequently, the moving distance of the base integrated with the simulated passenger room can be shortened, which results in a further compact structure of the system. 
   In the lateral steady acceleration simulation system of the invention, it is preferable that the control means adjusts the second reproductive acceleration such that it has negative value, and correspondingly adjusts the first reproductive acceleration so as to stop the motion of the base, if the base is in motion in either of the left or right direction when the second reproductive acceleration has reached zero. At a point of time at which the second reproductive acceleration has reached zero, the lateral steady acceleration is simulated only by utilizing the first reproductive acceleration and, therefore, it would be possible to keep simulating the lateral steady acceleration by maintaining such a state. However, in cases where the base is in motion when the second reproductive acceleration has reached zero, and if such a state is maintained as it is, the base continues to move at a constant velocity, which results in a large moving distance of the base in the left or right direction. Thus, in such a case, the second reproductive acceleration is preferably adjusted to have negative value, and the first reproductive acceleration is preferably adjusted correspondingly as well, thereby stopping the motion of the base. In this manner, the base is not kept moving, and thus, the structure of the system can be made compact. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a view showing the entire structure of a riding quality simulation system according to an embodiment of the invention; 
       FIG. 2  is an explanatory view showing how to dispose actuators; 
       FIGS. 3A  to  3 E are explanatory views showing the motion of the actuators when vibration along each of six axes is applied to a simulated passenger room; 
       FIG. 4  is an explanatory view showing an example of a curve of a railway line (track); 
       FIG. 5  is a graph showing changes with time in acceleration applied to a passenger and changes with time in velocity of the simulated passenger room, in simulating the traveling of a railway vehicle around a curve; and 
       FIGS. 6A and 6B  are explanatory views showing first and second reproductive accelerations, respectively. 
   

   PREFERRED EMBODIMENT OF THE INVENTION 
   A preferred embodiment of the invention is hereinafter described with reference to the drawings.  FIG. 1  is a view showing the entire structure of a riding quality simulation system according to the embodiment. A riding quality simulation system  1  according to this embodiment is an example of a lateral steady acceleration simulation system of the invention, which comprises a simulated passenger room  10 , a passenger room mounting table  20 , a base  30 , six actuators  40 , a drive unit  60 , and a control unit  60 . 
   The simulated passenger room  10  is a closed space imitating an interior of a railway vehicle. In the simulated passenger room  10 , seats  11 , which are the same as those of the railway vehicle, are arranged in the same manner as in the railway vehicle. Peripheral walls and a ceiling are also provided in the same manner as those of the railway vehicle. Each of lateral walls is provided with a simulated window  12 , in which an imaging device  12   a  is installed. While a simulated running test is being performed, views seen from an actual railway vehicle during its traveling are projected on the imaging device  12   a . Furthermore, speakers (not illustrated) are also installed inside the simulated passenger room  10  such that, while the simulated running test is being performed, sounds heard in an actual railway vehicle during its traveling are outputted from the speakers. 
   The passenger room mounting table  20  is a table on which the simulated passenger room  10  is to be mounted. The simulated passenger room  10  is mounted on the passenger room mounting table  20  via a high-frequency vibration table  25 . The high-frequency vibration table  25  is a relatively small device that is capable of reproducing vibration along three axes, i.e., an up-down axis, a left-right axis, and a forward-backward axis, in a high-frequency range of at least 5 to 40 Hz. 
   The base  30  supports the passenger room mounting table  20  via six actuators  40 . The base  30  is movable along two guide rails  31 ,  31  extending in the lateral direction. More specifically, the base  30  is moved by a laterally moving device  32  (corresponding to laterally moving means of the invention), which is employed, during the simulated running test, to simulate running of a railway vehicle taking a curve. 
   The six actuators  40  are, as shown in  FIG. 2 , respectively arranged along six sides of a virtual octahedron comprising, as its top face, a virtual triangle T 1  on the passenger room mounting table  20  and, as its bottom face, a virtual triangle T 2  on the base  30 , the six sides respectively connecting vertexes of the virtual triangle T 1  and those of the virtual triangle T 2 . Each of the actuators  40  is rotatably attached, at its upper end, to the undersurface of the passenger room mounting table  20  and, at its lower end, to the top face of the base  30 . Each actuator  40  is a hydraulic servo actuator (that is, a vibration generation part having a piston with a hydraulic control mechanism) and, as shown in  FIG. 3 , is composed of a piston rod  41  for its upper part and a cylinder  42  for its lower part 
   The drive unit  50  drives the actuators  40  by supplying each of the actuators  40  with hydraulic pressure generated by a hydraulic pump (not shown). 
   The control unit  60  (corresponding to control means of the invention) controls the drive unit  50  such that the hydraulic pressure generated by the hydraulic pump of the drive unit  50  is adjusted to provide a pressure and a flow as required by each of the actuators  40 , thereby activating each of the actuators  40 . In this manner, the simulated passenger room  10  mounted on the passenger room mounting table  20  is subjected to oscillation or vibration in a low-frequency range along six axes, that is, an up-down axis, a left-right axis, a forward-backward axis, a yaw axis (i.e., rotary motion about the up-down axis), a pitch axis (i.e., rotary motion about the forward-backward axis), and a roll axis (i.e., rotary motion about the forward-backward axis). Also, the control unit  60  controls the laterally moving device  32  so as to move the base  30  integrated with the simulated passenger room  10  with an arbitrary acceleration. 
   Here, a unit for applying oscillation or vibration in a low-frequency range along six axes, including the six actuators  40  and the drive unit  50 , is referred to as a six-degree-of-freedom vibration device (corresponding to roll application means of the invention). As such a six-degree-of-freedom vibration device, for example, a Stewart-type six-degree-of-freedom motion, which is conventionally known, may be employed. 
   Now, the operation of the six-degree-of-freedom vibration device of the riding quality simulation system  1  according to this embodiment is described.  FIGS. 3A  to  3 E are explanatory views showing the motion of the six actuators  40  when vibration along each of six axes is applied to the simulated passenger room. As shown in  FIGS. 3A  to  3 E, the control unit  60  controls the drive unit  50  so as to appropriately adjust the amount of protrusion of the piston rods  41  of the six actuators  40 , thereby applying to the passenger room mounting table  20 , and thus to the simulated passenger room  10 , oscillation or vibration in a low-frequency range along the up-down axis, the left-right axis, the forward-backward axis, the roll axis, the pitch axis, or the yaw axis. Also, the control unit  60  allows a simultaneous application of oscillations or vibrations along a plurality of axes arbitrarily selected among the six axes, by controlling the drive unit  50  accordingly. 
   Now, in the riding quality simulation system  1  according to this embodiment, the operation for simulating lateral steady acceleration generated when a railway vehicle runs around a curve is described. 
   As shown in  FIG. 4 , a curve of a railway line (track) comprises a first transition curve  91 , a circular curve  92 , and a second transition curve  93 . The first transition curve  91  is a section of the railway line in which radii of curvature gradually become smaller between a linear section  90  and the circular curve  92  and finally reach a radius of curvature of the circular curve  92 . The circular curve  92  is a section of the railway line having a constant radius of curvature. The second transition curve  93  is a section of the railway line in which radii of curvature gradually become larger between the circular curve  92  and a linear section  94 , the second transition curve  93  finally turning into a straight line of the linear section  94 . 
   An example of acceleration generated when a railway vehicle runs around such a curve is shown in FIG.  5 . More particularly, shown in an upper part of this  FIG. 5  is relationship between time and acceleration to which a person riding on the simulated passenger room  10  is subjected, and shown in a lower part thereof is relationship between time and moving velocity of the simulated passenger room  10 . As shown in the upper part of  FIG. 5 , lateral steady acceleration α (shown by an alternate-long-and-short dashed line) increases at a constant rate in the first transition curve  91  and reaches a fixed value (i.e., constant acceleration) in the circular curve  92 . 
   In order to simulate such a lateral steady acceleration pattern as shown in the upper part of  FIG. 5 , the control unit  60  makes control in such a manner that the simulated passenger room  10  is subjected to roll and the base  30  integrated with the simulated passenger room  10  is subjected to accelerated motion, as shown in  FIGS. 6A and 6B . 
   More specifically, as shown in  FIG. 6A , the control unit  60  activates each of the actuators  40  via the drive unit  50 , thereby making the simulated passenger room  10  roll (see FIG.  3 D). In this manner, the simulated passenger room  10  is gradually inclined, while a component force, along the inclined plane, of gravitational acceleration g, that is, a first reproductive acceleration G 1  (=g·sin θ) is generated depending on an angle of inclination θ. This means that the person riding on the simulated passenger room  10  bodily senses the first reproductive acceleration G 1  by the roll. Also, as shown in  FIG. 6B , the control unit  60  moves the simulated passenger room  10 , by means of the laterally moving device  32 , in either of the left or right direction with acceleration G. Accordingly, the person riding on the simulated passenger room  10  bodily senses a second reproductive acceleration G 2 , which is a component force, along the inclined plane, of the acceleration G of the simulated passenger room (=G·cos θ). As a result, the person riding on the simulated passenger room  10  bodily senses a combination of the first and second reproductive accelerations G 1  and G 2  as lateral steady acceleration on a railway. 
   Now, the procedure for simulating the lateral steady acceleration pattern as shown in the upper part of  FIG. 5  is described in detail. First of all, a range of angular acceleration and angular velocity within which rolling movement is not recognized by a person riding on the simulated passenger room  10  is experientially determined in advance (this range hereinafter referred to as an insensible range). In the first transition curve  91 , the simulated passenger room  10  is subjected to rolling movement within the insensible range. In this manner, as the simulated passenger room  10  is inclined by the rolling movement, its angle of inclination θ is increased, and the first reproductive acceleration G 1  is increased as well. In this respect, the first reproductive acceleration G 1  is controlled to increase at a fixed rate. Then, insufficiency of the first reproductive acceleration G 1  relative to the lateral steady acceleration α is compensated for with the second reproductive acceleration G 2 , thereby simulating the lateral steady acceleration α (=G 1 +G 2 ). Here, the second reproductive acceleration G 2  is also increased at a fixed rate. 
   Subsequently, the first reproductive acceleration G 1  is still increased at the fixed rate for a while after reaching a point of time t 1 , at which switching is made to the circular curve  92 . On the contrary, the second reproductive acceleration G 2  is now decreased at a fixed rate, since the insufficiency of the first reproductive acceleration G 1  relative to the lateral steady acceleration α is gradually reduced. 
   Then, at a point of time t 2 , at which the first reproductive acceleration G 1  becomes equal to the lateral steady acceleration α, the second reproductive acceleration G 2  becomes zero. However, at the point of time t 2 , the base  30  integrated with the simulated passenger room  10  is still moving at a velocity v 0  (see the lower part of FIG.  5 ). Accordingly, if this state were maintained as it were, lack of length of the guide rails  31 ,  31  would be raised due to the continuing motion of the base  30  integrated with the simulated passenger room  10 , although the lateral steady acceleration α could be simulated only by the first reproductive acceleration G 1 . 
   Therefore, after passing the point of time t 2 , the second reproductive acceleration G 2  continues to be decreased at the fixed rate to reach negative value, such that the velocity of the simulated passenger room  10  is lowered. On the other hand, the first reproductive acceleration G 1  continues to be increased at the fixed rate so as to be equal, in combination with the second reproductive acceleration G 2 , to the lateral steady acceleration α. 
   Further subsequently, the second reproductive acceleration G 2  still has negative value after passing a point of time t 3 . However, the absolute value thereof is decreased at a fixed rate, and thus, the moving velocity of the base  30  integrated with the simulated passenger room  10  is finally made zero at a point of time t 4 . Between the points of time t 3  and t 4 , the first reproductive acceleration G 1  is decreased at a fixed rate so as to be equal, in combination with the second reproductive acceleration G 2 , to the lateral steady acceleration α. 
   Then, after passing the point of time t 4 , the second reproductive acceleration G 2  is kept zero, and the lateral steady acceleration α is simulated only by the first reproductive acceleration G 1 . In other words, after the point of time t 4 , the lateral steady acceleration α is simulated only by means of the angle of inclination θ of the simulated passenger room  10 , with the base  30  integrated with the simulated passenger room  10  stopping. 
   On the contrary, in order to simulate the lateral steady acceleration applied to the railway vehicle during running from the circular curve to the linear section passing through the second transition curve, the reversed control may be carried out. 
   As described in detail above, by adopting the riding quality simulation system  1  according to the embodiment, lateral steady acceleration applied to a railway vehicle for a long period of time, for example, in cases where the railway vehicle runs through a long-distance curving section, can be simulated. More particularly, such lateral steady acceleration is simulated by utilizing the first reproductive acceleration G 1  that is bodily sensed by a person riding on the simulated passenger room  10  by means of the inclination of the simulated passenger room  10 , in addition to the second reproductive acceleration G 2  that is bodily sensed by the person riding on the simulated passenger room  10  by means of the accelerated motion of the simulated passenger room  10 . Consequently, it is not necessary that the simulated passenger room  10  should be shifted such a long distance in the left or right direction. Accordingly, a situation in which a railway vehicle is subjected to lateral steady acceleration for a long period of time can be simulated within a compact structure of the system. 
   Also, the angular acceleration or angular velocity in making the simulated passenger room  10  roll is set within an insensible range and, accordingly, the person riding on the simulated passenger room  10  does not become aware of the rolling movement. Therefore, he/she does not have a strange feeling about the riding quality. Especially, the simulated passenger room  10  is a closed space and the person riding thereon can not see the outside, which makes it more difficult for him/her to notice the simulated passenger room  10  rotating. As a result, the person riding on the simulated passenger room  10  would never feel odd while riding thereon. 
   Furthermore, in simulation of the lateral steady acceleration on the railway, the first reproductive acceleration G 1  is mainly utilized, while the second reproductive acceleration G 2  is utilized for the purpose of compensation therefor. Consequently, the rate of the second reproductive acceleration G 2  in the lateral steady acceleration to be simulated becomes smaller, and a moving distance of the simulated passenger room  10  can thus be shortened, which results in a further compact structure of the system. 
   Further in addition, in cases where the base  30  is still in motion at the point of time t 2 , at which the second reproductive acceleration G 2  has reached zero, the second reproductive acceleration G 2  is adjusted to have negative value such that the motion of the base  30  is stopped thereafter. At the same time, the first reproductive acceleration G 1  is correspondingly adjusted and, therefore, the base  30  is not kept moving, which also results in a compact structure of the system. 
   The present invention is, of course, not restricted to the above described embodiment, and may be practiced or embodied in still other ways within the technical scope of the invention. 
   For example, in the above described embodiment, the six actuators  40  are provided as the roll application means for making the simulated passenger room  10  roll. However, the roll application means is not restricted to such actuators  40  and may be any other device that can make the simulated passenger room  10  roll. More particularly, the four-axis simulation system as mentioned in the description of the “Background Art” may be employed. 
   Also, in the above described embodiment, centrifugal force generated at the time of rolling of the simulated passenger room  10  is not taken into consideration; however, the lateral steady acceleration may be simulated in view of such centrifugal force. 
   Furthermore, in the above described embodiment, the base  30  is moved by means of the laterally moving device  32 ; however, the base  30  may be designed to be movable by itself in the left or right direction. 
   Further in addition, in the above described embodiment, a relatively simple pattern is given as an example of a lateral steady acceleration pattern, as shown in FIG.  5 . However, the lateral steady acceleration simulation system of the invention is capable of simulating not only lateral steady acceleration that is linearly changed as in the case of  FIG. 5 , but also lateral steady acceleration that is more complicatedly changed with a curve. 
   INDUSTRIAL APPLICABILITY 
   As mentioned above, by adopting a lateral steady acceleration simulation system of the invention, it is possible to simulate a situation in which a railway vehicle is subjected to the lateral steady acceleration for a long period of time, while having a compact structure.