Step detection device

Abstract

To provide a step detection device capable of accurately detecting a step on a road surface.SOLUTION: A step detection device 10 mounted on a wheelchair 100 including a front wheel 101 and a rear wheel 102 has a step detection unit 13 that acquires a pitch rate detected by a gyro sensor 4 for detecting a pitch rate of the wheelchair 100 to detect a step on a road surface on which the wheelchair 100 travels and passes based on the acquired pitch rate. The step detection unit 13 detects a step based on a first pitch rate that is a pitch rate detected by the gyro sensor 4 when the front wheel 101 passes on a road surface and a second pitch rate that is a pitch rate detected by the gyro sensor 4 when the rear wheel 102 passes a position where the first pitch rate is detected.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a step detection device for detecting steps on a road surface.

Background Art

[0002] A barrier-free map has been created that shows steps on the road surface and clearly indicates an easy-to-pass route for users such as wheelchair users. Such a barrier-free map has been surveyed manually for steps and the like, which is time-consuming, takes time, and costs a lot. Therefore, barrier-free maps have only been created in some cities.

[0003] Also, due to manual surveys, it is difficult to update the barrier-free map frequently. Therefore, for example, changes in the road surface conditions such as road construction may not be reflected in the barrier-free map, and there may be a situation where it is far from the actual road surface conditions.

[0004] In response to such problems, devices that automatically detect steps and the like have been proposed. For example, Patent Document 1 describes that an angular velocity sensor of a mobile terminal detects the angular velocity of a user while walking, compares it with the angular velocity data of a flat place stored in advance, and determines that it is a step of a staircase if the difference is large, and transmits the step information and the position to the center.

[0005] Also, Patent Document 2 describes that when the road gradient of a vehicle calculated by a 3D gyroscope during running is larger than a predetermined value, it is determined as a steep step, and the point determined as a step is registered.

[0006] Also, Patent Document 3 describes that a vibration detection means and an inclination detection means are provided on a wheelchair, and the unevenness and inclination of the road surface when moving are uploaded to a server together with position information.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] JP 2012-098939 A [Patent Document 2] JP 2005-043261 A [Patent Document 3] JP 2003-010257 A Summary of the Invention [Problem to be solved by the invention]

[0008] The method described in Patent Document 1 can detect steps that have a continuous series of steps, such as stairs, or steps with a large difference in height, but may not be able to detect small steps because a pedestrian can cross them in one step. The method described in Patent Document 2 distinguishes between steps and inclinations based on the magnitude of the gradient angle, making it difficult to accurately detect steps that have a small gradient angle and are relatively low in height. Thus, the methods described in these documents have difficulty accurately detecting steps that are not a problem for pedestrians but are a barrier for wheelchairs, etc.

[0009] In addition, the method described in Patent Document 3 discloses that a vibration detection means detects the unevenness of the road surface, but does not disclose any specific method for detecting steps, so it is not possible to distinguish whether a detected point is an unevenness or a step.

[0010] In view of the above-mentioned problems, an object of the present invention is to provide a step detection device that can accurately detect steps on a road surface, for example. [Means for solving the problem]

[0011] In order to solve the above problems, the invention according to claim 1 is a step detection device mounted on a moving body having front wheels and rear wheels or attachable to the moving body, comprising: an acceleration acquisition means for acquiring an acceleration detected by an acceleration detection means for detecting an acceleration in a direction perpendicular to the moving plane of the moving body; a pitch rate acquisition means for acquiring a pitch rate detected by a pitch rate detection means for detecting a pitch rate of the moving body, and a step detection means for detecting a step on a road surface on which the moving body has traveled and passed based on the acquired pitch rate and the acceleration acquired by the acceleration acquisition means, wherein the step detection means includes a first pitch rate which is the pitch rate detected by the pitch rate detection means when the front wheels pass on the road surface, the acceleration acquired in the acceleration acquisition step when the first pitch rate is detected, a second pitch rate which is the pitch rate detected by the pitch rate detection means when the rear wheels pass at the position where the first pitch rate is detected, and the acceleration acquired by the acceleration acquisition means when the second pitch rate is detected, and detects the step based on these. A step detection device characterized by the above is provided.

[0012] Further, the invention according to claim 9 is a step detection method executed by a step detection device mounted on a moving body having front wheels and rear wheels or attachable to the moving body, the method including: an acceleration acquisition step of acquiring an acceleration detected by an acceleration detection means for detecting an acceleration in a direction perpendicular to the moving plane of the moving body; a pitch rate acquisition step of acquiring a pitch rate detected by a pitch rate detection means for detecting a pitch rate of the moving body, and detecting a step on a road surface passed by the moving body based on the acquired pitch rate and the acceleration acquired in the acceleration acquisition step; wherein the step detection step includes detecting the step based on a first pitch rate which is the pitch rate detected by the pitch rate detection means when the front wheels pass on the road surface, the acceleration acquired in the acceleration acquisition step when the first pitch rate is detected, a second pitch rate which is the pitch rate detected by the pitch rate detection means when the rear wheels pass at the position where the first pitch rate is detected, and the acceleration acquired in the acceleration acquisition step when the second pitch rate is detected.

[0013] Further, the invention according to claim 10 is a step detection program characterized by causing a computer to execute the step detection method according to claim 9.

[0014] Further, the invention according to claim 11 is a computer-readable recording medium characterized by storing the step detection program according to claim 10.

Brief Description of the Drawings

[0015]

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DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, a step detection device according to an embodiment of the present invention will be described. The step detection device according to an embodiment of the present invention is mounted on a moving body having front wheels and rear wheels or can be attached to the moving body. And the step detection means detects a step based on a first pitch rate which is the pitch rate detected by the pitch rate detection means when the front wheel passes on the road surface, and a second pitch rate which is the pitch rate detected by the pitch rate detection means when the rear wheel passes the position where the first pitch rate was detected. By doing so, since a step can be detected by the change in the pitch rate of the two wheels of the front wheel and the rear wheel, even a relatively low step can be accurately detected on the road surface.

[0017] Further, the step detection means may use, as the second pitch rate, the pitch rate detected when the moving body moves a distance related to the wheelbase length of the moving body from the position on the road surface where the first pitch rate is detected. By doing so, based on the wheelbase length, which is the length between the front wheels and the rear wheels of the moving body and is a known value, the position for detecting the second pitch rate can be specified.

[0018] Further, the step detection means may detect the position as a step when the absolute value of the first pitch rate is equal to or greater than a predetermined first threshold value and the absolute value of the second pitch rate is equal to or greater than a predetermined second threshold value. By doing so, when pitch rates having absolute values equal to or greater than a certain value are detected at the time of front wheel passage and at the time of rear wheel passage, they can be regarded as steps, so that the detection of steps can be made with high accuracy.

[0019] Further, an acceleration acquisition means for acquiring the acceleration detected by an acceleration detection means for detecting the acceleration in the direction perpendicular to the moving plane of the moving body is provided, and the step detection means may detect a step based on the acceleration acquired by the acceleration acquisition means when the first pitch rate is detected and the acceleration acquired by the acceleration acquisition means when the second pitch rate is detected. By doing so, in addition to the pitch rate, the acceleration in the vertical direction can also be considered, so that the detection accuracy of the step can be further improved.

[0020] Further, the step detection means may detect the position as a step when the absolute value of the acceleration acquired by the acceleration acquisition means when the first pitch rate is detected is equal to or greater than a predetermined third threshold value and the absolute value of the acceleration acquired by the acceleration acquisition means when the second pitch rate is detected is equal to or greater than a predetermined fourth threshold value. By doing so, when accelerations in the vertical direction equal to or greater than a certain value are detected at the time of front wheel passage and at the time of rear wheel passage, they can be regarded as the first pitch rate, and the detection of steps can be made with high accuracy.

[0021] Further, the step detection means may detect a step based on the sign of the pitch rate acquired from the pitch rate detection means and the direction of change in acceleration acquired by the acceleration acquisition means. By doing so, it is possible to consider the sign of the pitch rate, that is, whether the pitch rate is positive or negative, and the direction of change in acceleration, that is, whether the acceleration has increased or decreased. Therefore, it is possible to accurately detect a step by considering the direction of the pitch rate and the direction of the acceleration.

[0022] Further, the step detection means may detect whether the step passed by the moving body is an uphill step or a downhill step based on the sign of the first pitch rate and the sign of the second pitch rate. By doing so, it is possible to determine whether the currently passed step is an uphill step or a downhill step based on the signs of the two pitch rates.

[0023] Further, when the step detection means detects a step, it generates normalized pitch rate information including a first normalized pitch rate obtained by normalizing the peak value of the first pitch rate by the wheelbase length and / or a second normalized pitch rate obtained by normalizing the peak value of the second pitch rate by the wheelbase length. Then, the position acquisition means acquires information regarding the position where the step is detected, and the transmission means transmits the information regarding the position where the step is detected acquired from the position acquisition means and the normalized pitch rate information to the server device as information for causing the external server device to determine the level of the step on the road surface. By doing so, it is possible to reduce the detection error due to the difference in wheelbase length by the normalized pitch rate information. In addition, it is possible to accumulate the result of determining the step level based on the information collected from a plurality of step detection devices by the server device. Therefore, the determination accuracy of the step can be improved.

[0024] Further, when the step detection means detects a step, it may determine the level of the step based on a first normalized pitch rate obtained by normalizing the peak value of the first pitch rate by the wheelbase length, and / or a second normalized pitch rate obtained by normalizing the peak value of the second pitch rate by the wheelbase length. By doing so, it is possible to reduce the detection error due to the difference in the wheelbase length.

[0025] Alternatively, the position acquisition means may acquire information regarding the position where the step is detected, and the transmission means may transmit the step level determined by the step detection means and information regarding the position where the step is detected to an external server device. By doing so, it is possible to accumulate the result of determining the step level based on the information collected from a plurality of step detection devices by the server device.

[0026] Further, in the step detection method according to an embodiment of the present invention, in the step detection step, a first pitch rate which is the pitch rate detected by the pitch rate detection means when the front wheel passes on the road surface, and a second pitch rate which is the pitch rate detected by the pitch rate detection means when the rear wheel passes through the position where the first pitch rate is detected are used to detect a step. By doing so, since a step can be detected based on the change in the pitch rate of two wheels, the front wheel and the rear wheel, it is possible to accurately detect a step on the road surface even for a relatively low step.

[0027] Alternatively, it may be a step detection program for causing a computer to execute the above-described step detection method. By doing so, since a step can be detected based on the change in the pitch rate of two wheels, the front wheel and the rear wheel, using a computer, it is possible to accurately detect a step on the road surface.

[0028] Alternatively, the above-described step detection program may be stored in a computer-readable recording medium. By doing so, the program can be distributed not only when incorporated into a device but also as a single entity, and version updates and the like can be easily performed.

Example

[0029] A step detection device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 12. As shown in FIG. 1, an arithmetic unit 1 as the step detection device according to this embodiment is mounted on a wheelchair 100 as a moving body.

[0030] FIG. 1 is a configuration diagram of a step detection system having a step detection device according to an embodiment of the present invention. As shown in FIG. 1, in addition to the arithmetic unit 1, a GPS receiver 2, an acceleration sensor 3 as acceleration detection means, a gyro sensor 4 as pitch rate detection means, and a communication device 5 as transmission means are mounted on the wheelchair 100. Here, the arithmetic unit 1 and the communication device 5 constitute a step detection device 10 according to an embodiment of the present invention.

[0031] The communication device 5 mounted on the wheelchair 100 can be wirelessly connected to a network network N such as the Internet, and can communicate with the server device 50 via this network network N.

[0032] The wheelchair 100 is provided with a pair of left and right front wheels 101 and a pair of left and right rear wheels 102 on the vehicle body. The front wheels 101 are provided on the front side of the vehicle body. The rear wheels 102 are provided on the rear side of the vehicle body. The diameter of the front wheels 101 is smaller than the diameter of the rear wheels 102.

[0033] The vehicle body of the wheelchair 100 is, for example, a frame structure composed of a steel pipe frame. And, a seat on which a user sits, a footrest on which the user's feet are placed, etc. are provided on the vehicle body.

[0034] Fig. 2 shows a functional block diagram of the devices mounted on the wheelchair 100. The arithmetic unit 1 includes, for example, a microcomputer equipped with a memory such as a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and an interface for connecting to a GPS receiver 2, an acceleration sensor 3, a gyro sensor 4, and a communication device 5. Further, the arithmetic unit 1 functions as a pitch rate acquisition unit 11, an acceleration acquisition unit 12 as an acceleration acquisition means, and a step detection unit 13 as a step detection means by executing a control program stored in a ROM or the like.

[0035] The pitch rate acquisition unit 11 acquires the pitch rate and the like detected by the gyro sensor 4. Further, the pitch rate acquisition unit 11 acquires the pitch rate acquired when the conditions described later are met as the first pitch rate and the second pitch rate.

[0036] The acceleration acquisition unit 12 acquires the acceleration and the like detected by the acceleration sensor 3.

[0037] The step detection unit 13 detects a step on the road surface based on the pitch rates (the first pitch rate and the second pitch rate) acquired by the pitch rate acquisition unit 11. The method of detecting the step will be described later. That is, the step detection unit 13 functions as a step detection means for detecting a step on the road surface that the moving body (wheelchair 100) has traveled through based on the acquired pitch rate. Note that the step in this embodiment refers to a position (point) on the road surface where it is difficult for the wheelchair 100 to go up or down, and a position where one road surface and the next road surface are connected by a vertical surface with a predetermined height or more or an inclined surface with a predetermined angle or more.

[0038] The GPS receiver 2 receives radio waves transmitted from a plurality of GPS (Global Positioning System) satellites as is well known, obtains the current location information (latitude, longitude), and outputs it to the arithmetic unit 1.

[0039] ​The acceleration sensor 3 detects the acceleration (vertical acceleration) in the direction perpendicular to the moving plane on which the wheelchair 100 travels and moves. The acceleration sensor 3 may be a sensor of any type, such as a capacitance type or a piezoresistive type, etc., but it is preferably small in size since it is mounted on the wheelchair 100.

[0040] The gyro sensor 4 acquires the rotational angular velocity (pitch rate) in the pitch direction of the wheelchair 100. Here, the pitch indicates the inclination in the vertical direction with respect to the traveling direction of the wheelchair 100 (the rotation angle with the lateral direction as the axis). The gyro sensor 4 may be a sensor of any type, such as a capacitance type or a piezoelectric type, etc., but it is preferably small in size since it is mounted on the wheelchair 100.

[0041] The communication device 5 wirelessly transmits the result calculated by the arithmetic unit 1 to the server device 50. The communication device 5 may be a communication method used in a mobile phone network such as LTE (Long Term Evolution) or W-CDMA (Wideband Code Division Multiple Access). It may also be a communication method of a wireless LAN such as Wi-Fi (registered trademark), or one that can switch between them and be used.

[0042] A functional configuration diagram of the server device 50 is shown in FIG. 3. The server device 50 includes a communication device 51, an arithmetic unit 52, and a storage device 53. The communication device 51 receives the result calculated by the arithmetic unit 1 transmitted from the communication device 5.

[0043] The arithmetic unit 52 has, for example, a microcomputer including memories such as a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). Also, the arithmetic unit 52 functions as a level determination unit 521 and an update unit 522 by executing a control program stored in the ROM or the like.

[0044] The level determination unit 521 determines the level of the step based on the information transmitted from the arithmetic unit 1. The level of the step is obtained by classifying the height of the step into levels, and is determined based on predetermined thresholds, for example, level 1 for 0 or more and less than 5 cm, level 2 for 5 cm or more and less than 10 cm, and so on.

[0045] The update unit 522 updates the barrier information of the map information 532 stored in the storage device 53 based on the determination result of the level determination unit 521. In addition, the update unit 522 accumulates information such as the normalized pitch rate transmitted from the arithmetic unit 1 as the normalized pitch rate information 531.

[0046] Next, the step detection principle in this embodiment will be described with reference to FIGS. 4 to 7. FIG. 4 is a diagram showing the movement state of the wheelchair 100 when passing through the upward step U, and FIG. 5 is a graph showing the changes in the pitch rate, pitch angle, and vertical acceleration in the state of FIG. 4. Note that the vertical acceleration graph in FIG. 5(c) has an initial value of about 9.8 m / s2, and the gravitational acceleration is detected as the initial value. That is, FIG. 5(c) means that a downward acceleration has been detected in advance, and the downward acceleration increases as the value increases.

[0047] First, the state in FIG. 4(a) is the state before passing through the upward step U. In this case, there are no significant changes in the pitch rate, pitch angle, or vertical acceleration (a in FIG. 5(a)). Next, the state in FIG. 4(b) is the state where the front wheel 101 climbs the upward step U (the front wheel 101 collides with the step). In this case, since the front wheel 101 climbs the upward step U, the body of the wheelchair 100 is in a diagonally upward state in the traveling direction, and the pitch rate increases upward (b in FIG. 5(a)). In addition, an upward vertical acceleration is generated because an upward force is received from the upward step U and an upward movement occurs, and the vertical acceleration increases (b in FIG. 5(c)).

[0048] Next, the state of FIG. 4(c) is a state where the rear wheel 102 climbs the upward step U (the rear wheel 102 collides with the step). In this case, since the rear wheel 102 climbs the upward step U, the body of the wheelchair 100 tries to shift from an inclined state to a horizontal state, and the pitch rate increases downward (c in FIG. 5(a)). Also, since the rear wheel 102 climbs the step, the body receives an upward force from the upward step U, so the vertical acceleration increases (c in FIG. 5(c)). And the state of FIG. 4(d) is the state after passing the upward step U. Also in this case, similar to before passing the upward step U, no large changes occur in the pitch rate, pitch angle, and vertical acceleration (d in FIG. 5(a)).

[0049] That is, in the case of the upward step U, when the front wheel 101 passes the upward step U, the pitch rate increases in the + direction and the vertical acceleration increases. That is, the vertical acceleration obtained by subtracting the pitch rate and the gravitational acceleration becomes a positive number. And when the rear wheel 102 passes the upward step U, the pitch rate increases in the - direction and the vertical acceleration increases. That is, the pitch rate becomes a negative number, and the vertical acceleration obtained by subtracting the gravitational acceleration becomes a positive number. Here, the pitch rate in this embodiment becomes a positive number when the body of the wheelchair 100 tilts upward with respect to the traveling direction, and becomes a negative number when the body tilts downward with respect to the traveling direction. Also, the vertical acceleration becomes a positive number in the upward direction and a negative number in the downward direction if the gravitational acceleration is subtracted. Here, when the front wheel 101 and the rear wheel 101 pass the upward step U, the vertical acceleration increases and then turns to decrease. This is because the wheels collide with the step and rise to a position higher than the upper surface of the step, and then fall from that position to the upper surface of the step (immediately after points b and c in FIG. 5(c)).

[0050] FIG. 6 is a diagram showing the moving state of the wheelchair 100 when passing the downward step D, and FIG. 7 is a graph showing the changes in the pitch rate, pitch angle, and vertical acceleration in the state of FIG. 6.

[0051] First, the state in Fig. 6(a) is the state before passing through the downward step D. In this case, there are no significant changes in the pitch rate, pitch angle, or vertical acceleration (a in Fig. 7(a)). Next, the state in Fig. 6(b) is the state where the front wheel 101 descends (falls) through the downward step D. In this case, since the front wheel 101 descends through the downward step D, the body of the wheelchair 100 becomes in a diagonally downward state in the traveling direction, and the pitch rate increases downward (b in Fig. 7(a)). Also, since the front wheel 101 falls, the vertical acceleration decreases (b in Fig. 7(c)).

[0052] Next, the state in Fig. 6(c) is the state where the rear wheel 102 descends (falls) through the downward step D. In this case, since the rear wheel 102 descends through the downward step D, the body of the wheelchair 100 tries to shift from a diagonal state to a horizontal state, and the pitch rate increases upward (c in Fig. 7(a)). Also, since the rear wheel 102 falls, the vertical acceleration decreases (c in Fig. 7(c)). And the state in Fig. 6(d) is the state after passing through the downward step D. In this case as well, similar to before passing through the downward step D, there are no significant changes in the pitch rate, pitch angle, or vertical acceleration (d in Fig. 7(a)).

[0053] That is, in the case of the downward step D, when the front wheel 101 passes through the downward step D, the pitch rate increases in the - direction and the vertical acceleration decreases. That is, the vertical acceleration obtained by subtracting the pitch rate and the gravitational acceleration becomes negative. And when the rear wheel 102 passes through the downward step D, the pitch rate increases in the + direction and the vertical acceleration decreases. That is, the pitch rate becomes positive, and the vertical acceleration obtained by subtracting the gravitational acceleration becomes negative. Here, when the front wheel 101 and the rear wheel 101 pass through the downward step D, the vertical acceleration decreases and then turns to increase, which is because the wheels bounce back after colliding with the ground (immediately after points b and c in Fig. 7(c)).

[0054] Therefore, according to FIGS. 4 to 7, it is possible to detect whether the wheelchair has passed over the upward step U or the downward step D based on the value and sign of the pitch rate detected by the gyro sensor 4 and the absolute value and the direction of change such as increase or decrease of the vertical acceleration detected by the acceleration sensor 3. Further, by setting a threshold value for the detected pitch rate and vertical acceleration, it is possible to surely detect the peaks that appear when passing over steps such as point b and point c shown in FIGS. 5 and 7.

[0055] Next, a method for accurately discriminating the height level of the step detected by the above-described principle will be described. As described above, the presence or absence of a step can be detected by a pitch rate or the like, but the height of the step cannot be discriminated only by the peak value of the pitch rate. This is because the wheelchair 100 has different wheelbase lengths (the length between the axle of the front wheel 101 and the axle of the rear wheel 102).

[0056] Here, as shown in FIG. 8, assuming that the height of the step is h, the wheelbase length is H, and the pitch angle is θ, then h = Hsinθ. Further, when the pitch angle θ is small, since sinθ ≒ θ, h = Hθ. Therefore, when h is constant, the pitch angle θ increases as the wheelbase length H decreases. Since this also applies to the pitch rate, which is the time change of the pitch angle, it can be said that there is a correlation (inverse proportional relationship) between the wheelbase H and the peak value of the pitch rate.

[0057] Therefore, in this embodiment, the influence of the wheelbase length is eliminated by normalizing the peak value of the detected pitch rate by the wheelbase length. As an example of normalization, multiplying the peak value of the pitch rate by the reciprocal of the wheelbase length can be mentioned. Note that other normalization methods may be used.

[0058] FIG. 9 shows a comparison of the pitch rate before and after normalization. FIG. 9(a) shows the case where the step is 2 cm, and FIG. 9(b) shows the case where the step is 4 cm. The horizontal axis in FIG. 9 is the sample number for identifying the wheelchair for which the data was measured. The diamonds in FIG. 9 are before normalization, and the circles are after normalization.

[0059] Figure 10 is a table summarizing the graph shown in Figure 9. As shown in Figure 10, in the case of a 2 cm step, the normalized average value μ decreases from 28.4 to 12.8, the standard deviation σ decreases from 6.98 to 2.50, and the coefficient of variation cv decreases from 0.246 to 0.195, respectively. In the case of a 4 cm step, the normalized average value μ also decreases from 44.7 to 19.8, the standard deviation σ decreases from 10.0 to 3.06, and the coefficient of variation cv decreases from 0.225 to 0.155, respectively. Here, the coefficient of variation is the standard deviation divided by the average value, and using this value, the degree of variation can be evaluated. It can be judged that the smaller the coefficient of variation, the less the variation, and the larger the coefficient of variation, the more the variation.

[0060] Therefore, normalization can reduce the variation due to the difference in the wheelbase of the wheelchair 100. Therefore, the accuracy (reliability) of the discrimination of the step level can be improved.

[0061] Next, the operations of the arithmetic unit 1 and the server device 50 having the above-described configuration will be described with reference to the flowcharts of FIGS. 11 and 12. FIG. 11 is a flowchart of the operation of the arithmetic unit 1.

[0062] First, in step S101, threshold values T1, T2, T3, and T4 are set in the step detection unit 13, and the process proceeds to step S102. The threshold values T3 and T4 are threshold values set for the vertical acceleration detected by the acceleration sensor 3. The threshold value T3 is a threshold value for detecting that the front wheel 101 has passed over a step, and the threshold value T4 is a threshold value for detecting that the rear wheel 102 has passed over a step. The threshold values T1 and T2 are threshold values set for the pitch rate detected by the gyro sensor 4. The threshold value T1 is a threshold value for detecting that the front wheel 101 has passed over a step, and the threshold value T2 is a threshold value for detecting that the rear wheel 102 has passed over a step. These threshold values T1, T2, T3, and T4 can be adjusted according to the wheelchair 100. Also, a data table corresponding to the type of wheelchair may be prepared in advance, and the type of wheelchair may be input so that the threshold values T1, T2, T3, and T4 and the wheelbase length H are automatically set.

[0063] Next, in step S102, the vertical acceleration Az and the pitch rate Pr are detected, and the process proceeds to step S103. In this step, the acceleration acquisition unit 12 acquires the vertical acceleration Az detected by the acceleration sensor 3, and the pitch rate acquisition unit 11 acquires the pitch rate Pr detected by the gyro sensor 4. That is, the pitch rate Pr acquired in this step becomes the first pitch rate.

[0064] Next, in step S103, the step detection unit 13 determines whether the vertical acceleration Az acquired in step S102 is less than -T3 and the pitch rate Pr is less than -T1. If this condition is satisfied (Yes), the process proceeds to step S104. If the condition is not satisfied (No), the process proceeds to step S105. This step detects the b point in FIGS. 7(a) and 7(c). Note that the vertical acceleration Az to be compared with the threshold value after this step is a value obtained by subtracting the gravitational acceleration component, and the threshold value is also defined by the change from the gravitational acceleration. That is, the threshold value T3 is the third threshold value, and the threshold value T1 is the first threshold value. Also, it is detected that the signs of the vertical acceleration Az and the pitch rate Pr are negative (negative numbers).

[0065] Next, in step S104, since it is determined in step S103 that the condition is satisfied, the step detection unit 13 tentatively determines that the step currently being passed through is a downward step, sets -1 in the step candidate flag, and proceeds to step S107. In this step, a state corresponding to the b point in FIGS. 7(a) and 7(c) is detected, but since the determination on the rear wheel 102 side has not been made, a tentative determination is made, and the step candidate flag set in the arithmetic unit 1 as a flag indicating the determination is set. Note that the value to be set in the step candidate flag is not limited to -1, and any value indicating that it is tentatively determined to be downward may be used.

[0066] On the one hand, in step S105, the step detection unit 13 determines whether the vertical acceleration Az acquired in step S102 is T3 or more and the pitch rate Pr is T1 or more. If this condition is satisfied (Yes), the process proceeds to step S106. If the condition is not satisfied (No), it is determined that no step is detected and this flowchart ends. This step detects the b point in FIGS. 5(a) and 5(c). That is, it also detects that the signs of the vertical acceleration Az and the pitch rate Pr are positive (positive numbers).

[0067] Next, in step S106, since it is determined in step S105 that the condition is satisfied, the step detection unit 13 tentatively determines that the currently passing step is an ascending step, sets 1 in the step candidate flag, and proceeds to step S107. In this step, a state corresponding to the b point in FIGS. 5(a) and 5(c) is detected, but since the determination on the rear wheel 102 side has not been made, a tentative determination is made and the step candidate flag is set in the same manner as in step S104. Note that the value set in the step candidate flag is not limited to 1, and any value indicating that it is tentatively determined to be ascending may be used.

[0068] Next, in step S107, the vertical acceleration Az and the pitch rate Pr after the movement of the wheelbase length H are detected, and the process proceeds to step S108. In this step, similar to step S102, the acceleration acquisition unit 12 acquires the vertical acceleration Az detected by the acceleration sensor 3, and the pitch rate acquisition unit 11 acquires the pitch rate Pr detected by the gyro sensor 4. Also, the moving distance of the wheelbase length H may be calculated from the latitude and longitude detected by the GPS receiver 2 based on the preset wheelbase length H, or may be calculated by multiplying the rotation angle of the wheels (rear wheels 102) of the wheelchair 100 by the preset circumference of the wheels. The rotation angle of the wheels of the wheelchair 100 can be detected by providing an angle sensor or the like on the wheels. Note that in this step, the detection of the vertical acceleration Az and the pitch rate Pr is performed within a predetermined range (predetermined range) before and after the distance of the wheelbase length H. That is, the predetermined range before and after the distance of the wheelbase length H becomes a distance related to the wheelbase length of the moving body (wheelchair 100). And the pitch rate Pr acquired in this step S108 becomes the second pitch rate.

[0069] Next, in step S108, the step detection unit 13 determines whether the vertical acceleration Az acquired in step S107 is less than -T4 and the pitch rate Pr is greater than or equal to T2. If this condition is satisfied (Yes), the process proceeds to step S109. If the condition is not satisfied (No), the process proceeds to step S111. This step detects the c point in FIGS. 7(a) and 7(c). That is, the threshold value T4 becomes the fourth threshold value, and the threshold value T2 becomes the second threshold value. Also, it is detected that the sign of the vertical acceleration Az is negative (negative number) and the sign of the pitch rate Pr is positive (positive number).

[0070] Next, in step S109, the step detection unit 13 determines whether the step candidate flag is -1. If it is -1 (Yes), the process proceeds to step S110. Otherwise (No), it is determined that no step is detected, and this flowchart ends.

[0071] Next, in step S110, since the step candidate flag indicates a downward step, the conditions at points b and c in FIG. 7 are satisfied, and the step detection unit 13 formally determines that the passed step is a downward step and proceeds to step S114. That is, the absolute value of the first pitch rate is greater than or equal to the first threshold (T1), and the absolute value of the second pitch rate is greater than or equal to the second threshold (T2). Also, the absolute value of the vertical acceleration obtained when detecting the first pitch rate is greater than or equal to the third threshold (T3), and the absolute value of the vertical acceleration obtained when detecting the second pitch rate is greater than or equal to the fourth threshold (T4). And the step is detected based on these conditions. Also, since the first pitch rate is negative and the second pitch rate is positive, the passed step is a downward step. That is, the downward step is detected based on the signs of the first pitch rate and the second pitch rate.

[0072] On the other hand, in step S111, the step detection unit 13 determines whether the vertical acceleration Az obtained in step S107 is greater than or equal to T4 and the pitch rate Pr is less than -T2. If this condition is satisfied (Yes), it proceeds to step S112. If the condition is not satisfied (No), it determines that no step is detected and ends this flowchart. This step detects point c in FIGS. 5(a) and 5(c). That is, it also detects that the sign of the vertical acceleration Az is positive (a positive number) and the sign of the pitch rate Pr is negative (a negative number).

[0073] Next, in step S112, the step determination unit 13 determines whether the step candidate flag is 1. If it is 1 (Yes), it proceeds to step S113. Otherwise (No), it determines that no step is detected and ends this flowchart.

[0074] Next, in step S113, since the step candidate flag indicates an uphill step, the conditions at points a and c in FIG. 5 are satisfied, and the step determination unit 13 formally determines that the passed step is an uphill step and proceeds to step S114. That is, the absolute value of the first pitch rate is greater than or equal to the first threshold (T1), and the absolute value of the second pitch rate is greater than or equal to the second threshold (T2). Also, the absolute value of the vertical acceleration obtained when the first pitch rate is detected is greater than or equal to the third threshold (T3), and the absolute value of the vertical acceleration obtained when the second pitch rate is detected is greater than or equal to the fourth threshold (T4). And the step is detected based on these conditions. Also, since the first pitch rate is positive and the second pitch rate is negative, the passed step is an uphill step. That is, the uphill step is detected based on the signs of the first pitch rate and the second pitch rate.

[0075] Next, in step S114, the step detection unit 13 acquires the position (latitude, longitude) from the GPS receiver 2 and records the position of the step in an internal memory or the like. In addition, when the distance of the wheelbase length is detected using the GPS receiver 2 in step S107, the position acquired at that time may be recorded. That is, the step detection unit 13 functions as a position acquisition means for acquiring information regarding the position where the step is detected.

[0076] Next, in step S115, the step detection unit 13 detects the peak value of the pitch rate Pr at the location (position) determined to be a step and proceeds to step S116. The peak value of the pitch rate Pr may be the value used in the determinations in steps S103, S105, S108, S111, etc. and stored in an internal memory or the like and used. Note that the peak value detected in this step may be the peak value on the front wheel 101 side (when determining steps S103 and S105), the peak value on the rear wheel 102 side (when determining steps S108 and S111), or the average of both.

[0077] Next, in step S116, the step difference determination unit 13 multiplies the reciprocal of the wheelbase length H of the wheelchair 100 by the peak value of the pitch rate Pr detected in step S115 for normalization and proceeds to step S117. Let the normalized peak value be the normalized pitch rate Pr_n. That is, the normalized pitch rate Pr_n becomes the normalized pitch rate information. Here, when the peak value on the front wheel 101 side is used in step S115, the normalized pitch rate Pr_n is the first normalized pitch rate; when the rear wheel 102 side is used, it is the second normalized pitch rate; and when the average of the peak values on the front wheel 101 side and the rear wheel 102 side is used, it is the average normalized pitch rate.

[0078] Next, in step S117, the step difference determination unit 13 adds the ID of the wheelchair 100 and transmits the position determined as a step difference (step difference position Sp) and the normalized pitch rate value Pr_n to the server device 50 via the communication device 5. The ID of the wheelchair 100 is an ID pre-assigned to each wheelchair and is set in the arithmetic unit 1.

[0079] As is clear from the above description, the flowchart of FIG. 11 functions as a step difference detection process for detecting a step difference based on the first pitch rate, which is the pitch rate detected by the pitch rate detection means when the front wheel 101 passes on the road surface, and the second pitch rate, which is the pitch rate detected by the pitch rate detection means when the rear wheel 102 passes through the position where the first pitch rate was detected.

[0080] Next, the operation of the server device 50 shown in FIG. 12 will be described. The flowchart shown in FIG. 12 is executed by the arithmetic unit 52.

[0081] First, in step S201, the arithmetic unit 52 reads the ID of the wheelchair 100 received by the communication device 51 and acquires the weighting value W of the wheelchair 100. Then, the arithmetic unit 52 performs an averaging process between the normalized pitch rate value Pr_n at the step difference position Sp received by the communication device 51 and past data using W (after consideration) and proceeds to step S202. Let the value calculated by this averaging process be the average value Pr_ave.

[0082] This weighted value W indicates the reliability of the normalized pitch rate value Pr_n transmitted in the past, and is stored in the storage device 53 in association with the ID of the wheelchair 100. This weighted value W may be, for example, set with an initial value of 1 and the numerical value increased as the reliability increases. Then, a weighted average is calculated together with the data of the normalized pitch rate information 531 in the storage device 53 where past data is stored.

[0083] Next, in step S202, the arithmetic unit 52 changes the weighted value W for the wheelchair 100 with the ID received in step S201 and proceeds to step S203. In this step, when the difference between the normalized pitch rate value Pr_n received by the communication device 51 and the average value Pr_ave is large, the weighted value W of this wheelchair 100 is decreased by a predetermined amount. Also, when the difference between the normalized pitch rate value Pr_n received by the communication device 51 and the average value Pr_ave is small, the weighted value W of this wheelchair 100 is increased by a predetermined amount. That is, a wheelchair that outputs a normalized pitch rate value Pr_n close to the average value Pr_ave will have a higher weighted value W.

[0084] Next, in step S203, the level determination unit 521 of the arithmetic unit 52 compares the threshold value of the step level with the average value Pr_ave calculated in step S202, determines the step level, and proceeds to step S204. This threshold value is preset according to the step level, for example, 5 cm, 10 cm, etc. For example, if the calculated average value Pr_ave is 6.8 cm, since it is in the range of 5 cm or more and less than 10 cm, it is determined as step level 2 or the like.

[0085] Next, in step S204, the update unit 522 of the arithmetic unit 52 creates or updates the barrier information stored in the map information 532 of the storage device 53 (creates or updates the barrier-free map) based on the result of the step level determined in step S203.

[0086] Note that, as described above, the determination of the step level requires the peak value of the pitch rate. However, if only determining whether there is a step, it does not have to be the peak value, and the determination can be made when values equal to or greater than each threshold value T1, T2, T3, and T4 are detected.

[0087] Also, in the above-described flowchart, the threshold values for determining the up-step and the down-step were set to the same absolute value with different polarities (such as T1 and -T1), but different threshold values may be set. As described above, when the front wheel 101 and the rear wheel 101 pass over the up-step U, the vertical acceleration increases and then turns to decrease because the wheel rises to a position higher than the upper surface of the step due to hitting the step, and then falls from that position to the upper surface of the step. When the front wheel 101 and the rear wheel 101 pass over the down-step D, the vertical acceleration decreases and then turns to increase because of the bounce after the wheel hits the ground. Therefore, if different threshold values are set for these vertical acceleration changes for determination, the up-step and the down-step can be detected with higher accuracy.

[0088] According to this embodiment, the arithmetic unit 1 is mounted on the wheelchair 100 including the front wheel 101 and the rear wheel 102. Then, the pitch rate detected by the gyro sensor 4 and acquired by the pitch rate acquisition unit 11 when the front wheel 101 passes on the road surface is defined as the first pitch rate, and the pitch rate detected by the gyro sensor 4 and acquired by the pitch rate acquisition unit 11 when the rear wheel 102 passes through the position where the first pitch rate was detected is defined as the second pitch rate. And the step detection unit 13 detects a step based on the first pitch rate and the second pitch rate. By doing so, since the step can be detected by the change in the pitch rate of the two wheels, the front wheel 101 and the rear wheel 102, even a relatively low step can be accurately detected on the road surface.

[0089] Further, the step detection unit 13 sets, as the second pitch rate, the pitch rate acquired by the pitch rate acquisition unit 11 when the wheelchair 100 moves within a predetermined range before and after a position that is at a distance of the wheelbase length H of the wheelchair 100 from the position on the road surface where the first pitch rate is detected. By doing so, based on the wheelbase length H, which is the length between the front wheels 101 and the rear wheels 102 of the wheelchair 100 and is a known value, the position for detecting the second pitch rate can be specified.

[0090] Further, the step detection unit 13 detects the position as a step when the absolute value of the first pitch rate is greater than or equal to the threshold value T1 and the absolute value of the second pitch rate is greater than or equal to the threshold value T3. By doing so, when pitch rates having an absolute value greater than or equal to a certain value are detected at the time of passing of the front wheels 101 and the time of passing of the rear wheels 102, they can be regarded as steps, so that the detection of steps can be performed with high accuracy.

[0091] Furthermore, an acceleration acquisition unit 12 is provided that acquires the vertical acceleration detected by an acceleration sensor 3 that detects the acceleration in the direction perpendicular to the moving plane of the wheelchair 100. The step detection unit 13 detects a step based on the vertical acceleration acquired by the acceleration acquisition unit 12 when the first pitch rate is detected and the vertical acceleration acquired by the acceleration acquisition unit 12 when the second pitch rate is detected. By doing so, in addition to the pitch rate, the acceleration in the vertical direction can also be considered, so that the detection accuracy of steps can be further improved.

[0092] Further, the step detection unit 13 detects the position as a step when the absolute value of the vertical acceleration acquired by the acceleration acquisition unit 12 when the first pitch rate is detected is greater than or equal to the threshold value T3 and the absolute value of the vertical acceleration acquired by the acceleration acquisition unit 12 when the second pitch rate is detected is greater than or equal to the threshold value T4. By doing so, when accelerations in the vertical direction greater than or equal to a certain value are detected at the time of passing of the front wheels 101 and the time of passing of the rear wheels 102, they can be regarded as the first pitch rate, and the detection of steps can be performed with high accuracy.

[0093] Further, the step detection unit 13 detects a step based on the sign of the pitch rate acquired from the gyro sensor 4 and the direction of change in the vertical acceleration acquired by the acceleration acquisition unit 12. By doing so, it is possible to consider the sign of the pitch rate, that is, whether the pitch rate is positive or negative, and the sign of the acceleration, that is, whether the acceleration has increased or decreased. Therefore, it is possible to accurately detect the step by considering the direction of the pitch rate and the direction of the acceleration as well.

[0094] Further, the step detection unit 13 detects whether the step passed by the wheelchair 100 is an ascending step or a descending step based on the sign of the first pitch rate and the sign of the second pitch rate. By doing so, it is possible to determine whether the currently passed step is an ascending step or a descending step based on the signs of the two pitch rates.

[0095] Further, when the step detection unit 13 detects a step, it generates a normalized pitch rate Pr_n obtained by normalizing the peak value of the pitch rate Pr by the wheelbase length H. Then, the step detection unit 13 acquires the latitude and longitude of the position where the step is detected from the GPS receiver 2. Then, in addition to the latitude and longitude of the position where the step is detected, the communication device 5 transmits the normalized pitch rate Pr_n and the ID of the wheelchair 100 to the server device 50 as information for the server device 50 to determine the level of the step on the road surface. By doing so, by calculating the normalized pitch rate Pr_n, it is possible to reduce the detection error due to the difference in the wheelbase length H. In addition, it is possible to accumulate the result of determining the step level based on the information collected from a plurality of step detection devices by the server device 50. Therefore, the determination accuracy of the step can be improved.

[0096] Further, the arithmetic unit 52 of the server device 50 performs weighting on the normalized pitch rate Pr_n transmitted from the wheelchair 100 (arithmetic unit 1) based on the weighting value W and then determines the step level. By doing so, it is possible to reduce the fluctuation of the step level due to low-reliability data and improve the reliability of the step level.

[0097] In the above-described embodiments, the server device 50 determines the step level. However, the determination may be made by the arithmetic unit 1 mounted on the wheelchair 100 based on the normalized pitch rate Pr_n. Then, the determination result, the latitude and longitude of the position where the step is detected, and the ID of the wheelchair 100 may be transmitted to the server device 50 via the communication device 5.

[0098] Also, in the above-described embodiments, the arithmetic unit 1 mounted on the wheelchair 100 is described as the step detection device. However, it may not be a dedicated device. For example, a terminal device having a communication function such as a smartphone equipped with (or connectable to) a GPS receiver, a gyro sensor, and an acceleration sensor can function as the step detection device by using the above-described flowchart as an app (computer program). In this case, a holder or the like may be provided on the wheelchair, and a smartphone or the like may be attached to the holder. That is, it becomes a step detection device attachable to the moving body.

[0099] Also, in the above-described embodiments, the step is detected based on the detection results of both the acceleration sensor 3 and the gyro sensor 4. However, even if only the detection result of the gyro sensor 4 is used, the step can be detected although the accuracy is inferior. In this case, only the threshold values T1 and T2 need to be set.

[0100] Also, in the above-described embodiments, since information on whether an ascending step or a descending step has been passed can be obtained, what kind of step (from which direction moving results in an ascending or descending step) may be determined based on the information and the moving direction such as the moving trajectory of the wheelchair 100.

[0101] Also, in the above-described embodiments, the moving body is described as a wheelchair. However, it may be any vehicle equipped with front and rear wheels for traveling on the road surface, such as a senior car, a baby stroller, a golf cart, a bicycle, an automobile, a trolley, a robot having wheels, etc.

[0102] Furthermore, the present invention is not limited to the above embodiments. That is, those skilled in the art can make various modifications and implement them without departing from the gist of the present invention in accordance with the conventionally known knowledge. As long as the configuration of the step detection device of the present invention is still included even by such modifications, of course, it is included in the scope of the present invention.

Explanation of Reference Numerals

[0103] 1 arithmetic unit 2 PS receiver 3 acceleration sensor (acceleration acquisition means) 4 gyro sensor 5 communication device (transmission means) 10 step detection device 11 pitch rate acquisition unit 12 acceleration acquisition unit (acceleration acquisition means) 13 step detection unit (step detection means, position acquisition means) 50 server device 100 wheelchair (mobile body) 101 front wheel 102 rear wheel

Claims

1. A step detection device that is mounted on a moving body having front and rear wheels or that can be attached to the moving body, an acceleration acquisition means for acquiring an acceleration detected by an acceleration detection means for detecting an acceleration in a direction perpendicular to a plane of movement of the moving body; a step detection means for acquiring a pitch rate detected by a pitch rate detection means for detecting a pitch rate of the moving body, and detecting a step on a road surface over which the moving body has traveled, based on the acquired pitch rate and the acceleration acquired by the acceleration acquisition means; Equipped with the step detection means detects the step based on a first pitch rate, which is a pitch rate detected by the pitch rate detection means when the front wheels pass over the road surface, the acceleration acquired by the acceleration acquisition means when the first pitch rate is detected, a second pitch rate, which is a pitch rate detected by the pitch rate detection means when the rear wheels pass a position where the first pitch rate was detected, and the acceleration acquired by the acceleration acquisition means when the second pitch rate is detected. A step detection device comprising:

2. The step detection device according to claim 1, characterized in that the step detection means detects the position as a step if the absolute value of the first pitch rate is equal to or greater than a predetermined first threshold, the absolute value of the second pitch rate is equal to or greater than a predetermined second threshold, the absolute value of the acceleration acquired by the acceleration acquisition means when the first pitch rate is detected is equal to or greater than a predetermined third threshold, and the absolute value of the acceleration acquired by the acceleration acquisition means when the second pitch rate is detected is equal to or greater than a predetermined fourth threshold.

3. 3. The step detection device according to claim 1, wherein the step detection means detects the step based on the sign of the pitch rate acquired from the pitch rate detection means and the direction of the change in acceleration acquired by the acceleration acquisition means.

4. The step detection device according to any one of claims 1 to 3, characterized in that the step detection means detects whether the step passed by the moving body was an upward step or a downward step based on the sign of the first pitch rate and the sign of the second pitch rate.

5. The step detection device described in any one of claims 1 to 4, characterized in that the step detection means sets the second pitch rate to the pitch rate detected when the moving body moves a distance related to the wheelbase length of the moving body from the position on the road surface where the first pitch rate was detected.

6. the step detection means generates normalized pitch rate information based on a first normalized pitch rate obtained by normalizing a peak value of the first pitch rate by the wheelbase length and / or a second normalized pitch rate obtained by normalizing a peak value of the second pitch rate by the wheelbase length when the step is detected, a position acquisition means for acquiring information regarding a position where the step is detected; a transmitting means for transmitting information regarding the position where the step was detected and normalized pitch rate information, which are acquired by the position acquiring means, to an external server device as information for allowing the server device to determine the level of the step on the road surface; The step detection device according to claim 5 , further comprising:

7. 6. The step detection device according to claim 5, wherein, when the step is detected, the step detection means determines a level of the step based on a first normalized pitch rate obtained by normalizing a peak value of the first pitch rate by the wheelbase length and / or a second normalized pitch rate obtained by normalizing a peak value of the second pitch rate by the wheelbase length.

8. a position acquisition means for acquiring information regarding a position where the step is detected; a transmitting means for transmitting information relating to the level of the step determined by the step detecting means and the position where the step is detected to an external server device; The step detection device according to claim 7, further comprising:

9. A step detection method implemented by a step detection device mounted on a moving body having front and rear wheels or attachable to the moving body, comprising: an acceleration acquiring step of acquiring an acceleration detected by an acceleration detecting means for detecting an acceleration in a direction perpendicular to a plane of movement of the moving body; a step detection step of acquiring a pitch rate detected by a pitch rate detection means for detecting a pitch rate of the moving body, and detecting a step on a road surface through which the moving body has traveled, based on the acquired pitch rate and the acceleration acquired in the acceleration acquisition step; Including, The step detection step detects the step based on a first pitch rate, which is a pitch rate detected by the pitch rate detection means when the front wheels pass over the road surface, the acceleration acquired in the acceleration acquisition step when the first pitch rate is detected, a second pitch rate, which is a pitch rate detected in the pitch rate detection step when the rear wheels pass a position where the first pitch rate is detected, and the acceleration acquired in the acceleration acquisition step when the second pitch rate is detected. A step detection method comprising:

10. A step detection program for causing a computer to execute the step detection method according to claim 9.

11. A computer-readable recording medium storing the step detection program according to claim 10.

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