Ground condition estimation system, ground condition estimation method, ground condition estimation device, and program

Abstract

To efficiently obtain information on a condition of the ground.SOLUTION: A ground condition estimation system includes: a load sensor that detects a load applied to wheels of a handcart; a positioning unit that measures a position of the handcart; and a ground condition estimating unit that associates the position of the handcart measured by the positioning unit with a time at which the load of the load sensor is detected, and estimates a condition of the ground at the position where a change pattern is obtained based on the change pattern of the load detected by the load sensor over time.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a ground condition estimation system, a ground condition estimation method, a ground condition estimation device, and a program. [Background technology]

[0002] There is known a technology for assisting in guiding small mobile / carrying devices such as baby strollers and wheelchairs to a destination by guiding the device while avoiding obstacles such as nearby utility poles, guardrails, handrails, walls, pedestrians, etc. detected by infrared sensors, cameras, etc. (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6258879 Summary of the Invention [Problem to be solved by the invention]

[0004] When a user moves around while carrying a pushcart such as a stroller, it is preferable for the user to know the ground conditions, such as steps, in advance, so that the user can select a detour in advance. In this case, it is required to efficiently obtain information about the ground conditions, such as steps.

[0005] In consideration of the above-mentioned problems, an object of the present invention is to efficiently obtain information regarding the condition of the ground. [Means for solving the problem]

[0006] One aspect of the present invention that solves the above-mentioned problems is a ground condition estimation system that includes a load sensor that detects the load on the wheels of a pushcart, a positioning unit that measures the position of the pushcart, and a ground condition estimation unit that associates the position of the pushcart measured by the positioning unit with the time at which the load of the load sensor was detected, and estimates the ground condition at the position where the change pattern was obtained based on the change pattern of the load detected by the load sensor over time.

[0007] One aspect of the present invention is a ground condition estimation method in a ground condition estimation system, which includes a ground condition estimation step of matching the position of a pushcart measured by a positioning unit that measures the position of the pushcart with the time at which a load is detected by a load sensor that detects the load on the wheels of the pushcart, and estimating, based on a change pattern of the load detected by the load sensor over time, the ground condition at the position where the change pattern was obtained.

[0008] One aspect of the present invention is a ground condition estimation device that includes a ground condition estimation unit that associates the position of a pushcart measured by a positioning unit that measures the position of the pushcart with the time at which a load is detected by a load sensor that detects the load on the wheels of the pushcart, and estimates the ground condition at the position where the change pattern was obtained based on a change pattern of the load detected by the load sensor over time.

[0009] One aspect of the present invention is a program for causing a computer acting as a ground condition estimation device to function as a ground condition estimation unit that corresponds the position of a pushcart measured by a positioning unit that measures the position of the pushcart with the time at which a load is detected by a load sensor that detects the load on the wheels of the pushcart, and estimates the ground condition at the position where the change pattern is obtained based on the change pattern of the load detected by the load sensor over time. Effect of the Invention

[0010] According to the present invention, it is possible to obtain an effect that information regarding the state of the ground can be obtained efficiently. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of a ground condition estimation system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating an example of a functional configuration of a stroller according to the present embodiment. [Diagram 3] FIG. 4 is a diagram showing an example of load history information in the present embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of a functional configuration of the ground condition estimation device according to the present embodiment. [Diagram 5] 10 is a flowchart showing an example of a processing procedure executed by a stroller and a ground condition estimating unit in the present embodiment in relation to processing of load history information. [Figure 6] 5 is a flowchart showing an example of a processing procedure executed by the ground condition estimation device in the present embodiment in relation to estimating ground conditions. [Figure 7] 6A and 6B are diagrams illustrating an example of a change pattern of a load in the present embodiment. [Figure 8] 6A and 6B are diagrams illustrating an example of a change pattern of a load in the present embodiment. [Figure 9] 6A and 6B are diagrams illustrating an example of a change pattern of a load in the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 1 shows an example of the overall configuration of the ground condition estimation system of this embodiment. In this embodiment, the "ground" includes not only the ground consisting of soil and the like that exists under the stroller 100 when the stroller is pushed and carried by the user, but also structures such as floors, roads, and walkways.

[0013] The ground condition estimation system of this embodiment includes a stroller 100 and a ground condition estimation device 200.

[0014] The stroller 100 is a type of handcart that is pushed and carried by a user U. The stroller 100 in the figure has four wheels, two front wheels and two rear wheels, as an example. In this case, the stroller 100 is equipped with four load sensors 101 (101-FL, 101-FR, 101-RL, 101-RR) corresponding to each of the four wheels. The load sensor 101-FL detects the load associated with the left front wheel. The load sensor 101-FR detects the load associated with the right front wheel. The load sensor 101-RL detects the load associated with the left rear wheel. The load sensor 101-RR detects the load associated with the right rear wheel. The stroller 100 includes a communication unit 104 that communicates via a network. The communication unit 104 of the stroller 100 transmits load history information indicating the history of the loads detected by each of the four load sensors 101 (101-FL, 101-FR, 101-RL, 101-RR) to the ground condition estimation device 200 via the network.

[0015] A positioning unit 102 is provided at a predetermined position of the stroller 100. The positioning unit 102 measures the position of the stroller 100. The positioning unit 102 may be configured to measure the position in accordance with GNSS (Global Navigation Satellite System), LiDAR (Light Detection And Ranging), Visual SLAM (Simultaneous Localization and Mapping), or the like. The positioning unit 102 may also be configured to measure the position using electromagnetic waves such as Bluetooth (registered trademark), Wi-Fi (registered trademark), or the like. The position measured by the positioning unit 102 is included in the load history information in such a manner that it is associated with the load detected at the same time (hour).

[0016] The ground condition estimation device 200 estimates the ground condition (ground condition) for each position indicated by the position information included in the load history information based on the load history information transmitted from the stroller 100. The ground condition estimation device 200 reflects the estimated ground condition on a map.

[0017] Although one stroller 100 is shown in the figure, there may be a plurality of strollers 100 in various locations that are communicatively connected to the ground condition estimation device 200. The ground condition estimation device 200 may estimate the ground condition at each location based on the load history information transmitted from each of the plurality of strollers 100, and may reflect the estimated ground condition on a map.

[0018] Furthermore, the ground condition estimation device 200 transmits a map reflecting the estimated ground conditions to the user terminal 300 of the user U of the stroller 100 as a ground condition map. The user terminal 300 displays the received ground condition map. The displayed ground condition map shows the ground conditions estimated by the ground condition estimation device 200. By checking the ground conditions shown on the ground condition map, the user U can plan a travel route, for example, when moving the stroller 100 with a child on it, so as to avoid large steps and rough roads. The user terminal 300 may be, for example, a smartphone or a tablet terminal.

[0019] Fig. 2 shows an example of the functional configuration of the stroller 100 of this embodiment. The functions shown in the figure are realized by a program executed by a CPU (Central Processing Unit) provided in the stroller 100. In the figure, the same parts as those in Fig. 1 are given the same reference numerals, and the description will be omitted as appropriate.

[0020] The stroller 100 in the figure includes load sensors 101 (101-FL, 101-FR, 101-RL, 101-RR), a positioning unit 102, a memory unit 103, a communication unit 104, and a control unit 105.

[0021] The storage unit 103 stores various types of information corresponding to the stroller 100. The storage unit 103 includes a load history information storage unit 131. The load history information storage unit 131 stores the load history information. The load history information is information that indicates the history of the load detected by the load sensor 101 for each stroller 100.

[0022] 3(A) shows an example of load history information corresponding to one stroller 100. As shown in the figure, the load history information has a structure in which load information (P1, P2, P3...) detected by the stroller 100 is associated with position information (ps1, ps2, ps3...) indicating the position of the stroller 100 for each time (tm1, tm2, tm3...).

[0023] In addition, in Figure 3 (B), load information Pn corresponding to one time includes loads (Pn-FL, Pn-FR, Pn-RL, Pn-RR) detected by each of the load sensors 101-FL, 101-FR, 101-RL, and 101-RR of the corresponding stroller 100.

[0024] Returning to Fig. 2 for the explanation, the control unit 105 executes various controls on the stroller 100. The control unit 105 associates the load detected by the load sensor 101 and the position measured by the positioning unit 102 with time, and stores them in the load history information storage unit 131 as load history information. Furthermore, the control unit 105 causes the load history information stored in the load history information storage unit 131 to be transmitted from the communication unit 104 to the ground condition estimation device 200 at a predetermined timing.

[0025] 4 shows an example of the functional configuration of the ground condition estimation device 200. The ground condition estimation device 200 in the figure includes a communication unit 201, a control unit 202, and a storage unit 203. The communication unit 201 performs communication via a network.

[0026] The control unit 202 executes various controls in the ground condition estimation device 200. The control unit 202 includes a load history information acquisition unit 221 and a ground condition estimation unit 222.

[0027] The load history information acquisition unit 221 acquires the load history information transmitted from the stroller 100 and received by the communication unit 201. The load history information acquisition unit 221 causes the load history information storage unit 231 to store the acquired load history information.

[0028] The ground condition estimation unit 222 estimates the ground condition for each position to which the stroller 100 has moved, using the load history information stored in the load history information storage unit 231. The ground condition estimation unit 222 generates a ground condition map that reflects the estimated ground condition, and stores the generated ground condition map in the ground condition map storage unit 232.

[0029] The storage unit 203 stores various types of information corresponding to the ground condition estimation device 200. The storage unit 203 includes a load history information storage unit 231 and a ground condition map storage unit 232. The load history information storage unit 231 stores the load history information acquired by the load history information acquisition unit 221 . The ground condition map storage unit 232 stores information on the ground condition map.

[0030] 5, a flowchart showing an example of a processing procedure executed by the stroller 100 and ground condition estimating device 200 of the present embodiment in relation to processing of load history information. First, an example of a process performed by the stroller 100 will be described.

[0031] Step S100: In the stroller 100, the control unit 105 waits for the stroller 100 to start moving. The control unit 105 may determine whether or not movement has started based on a change in load output by the load sensor 101, for example, or may determine whether or not movement has started using an acceleration sensor provided in the stroller 100. In addition, as step S100, for example, the control unit 105 may wait for an operation (start instruction operation) by the user U to instruct the start of acquisition of load history information. Such a start instruction operation may be an operation on an operator such as a predetermined switch or button provided in the stroller 100, or may be an operation on a user terminal 300 connected to the stroller 100 by short-range wireless communication such as Bluetooth.

[0032] Step S102: When it is determined in step S100 that the stroller 100 has started moving, the control unit 105 starts measuring time. After the time measurement starts, the control unit 105 becomes able to obtain the measured time (time of day).

[0033] Step S104: Furthermore, the control unit 105 starts measuring the current position.

[0034] Step S106: The control unit 105 acquires the loads detected by the load sensors 101. Step S108: The control unit 105 stores in the load history information storage unit 131 the load history information in which the load acquired in step S106 is associated with the time corresponding to the acquired load and the current position.

[0035] Step S110: After the process of step S108, the control unit 105 judges whether or not the stroller 100 has transitioned from a moving state to a stopped state. If it is judged that the stroller 100 has not transitioned to a stopped state, the process returns to step S106.

[0036] Step S112: If it is determined in step S110 that the stroller 100 has transitioned to a stopped state, the control unit 112 causes the communication unit 104 to transmit the load history information stored in the load history information storage unit 131 by the processes of steps S106 and S108 to the ground condition estimation device 200. After the process of step S112, the process returns to step S100. Note that, as the process of step S110, the control unit 105 may determine whether or not a certain time has elapsed from the timing when the time measurement was started in step S102. Alternatively, as the process of step S110, the control unit 105 may also start measuring the distance traveled by the stroller 100 at the timing when the time measurement was started in step S102, and determine whether or not the measured distance has reached a predetermined value. In this case, when it is determined in step S110 that a certain time has elapsed or that the distance has reached a predetermined value, the control unit 105 causes the communication unit 104 to transmit the load history information stored in the load history information storage unit 131 to the ground condition estimation device 200 in step S112.

[0037] Next, an example of a processing procedure executed by the ground condition estimation device 200 will be described. Step S200: In the ground condition estimation device 200, the load history information acquisition unit 221 acquires the load history information transmitted from the stroller 100 in step S112. Step S202: The load history information acquisition unit 221 stores the load history information acquired in step S200 in the load history information storage unit 231.

[0038] An example of a processing procedure executed by the ground condition estimation device 200 in relation to estimating ground conditions will be described with reference to the flowchart of Fig. 6. The processing in the figure may be executed at a predetermined timing. Specifically, for example, it may be executed each time the processing of steps S200 and S202 in Fig. 5 is completed. For simplicity of explanation, a case in which ground conditions are estimated based on load history information obtained corresponding to a period from the start to the stop of one movement of one stroller 100 will be taken as an example.

[0039] Step S300: In the ground condition estimation device 200, the ground condition estimation unit 222 detects a pattern of change in load over time by using load history information stored in the load history information storage unit 231, the load history information obtained corresponding to the period from the start of one movement of one stroller 100 to the stop of the movement.

[0040] Step S302: The ground condition estimating unit 222 estimates the ground condition at a position according to the movement trajectory of the corresponding stroller 100, based on the change pattern of the load detected in step S300.

[0041] A specific example of the estimation of the ground condition based on the load change pattern in step S302 will be described with reference to Figs. FIG. 7 shows an example of a load change pattern. In the figure, the horizontal axis is time and the vertical axis is load. In the figure, line L1 shows the change over time of the load Pn-FL on the left front wheel. Line L2 shows the change over time of the load Pn-FR on the right front wheel. Line L3 shows the change over time of the load Pn-RL. Line L4 shows the change over time of the load Pn-RR.

[0042] 7, the load change pattern of each of the four wheels is substantially constant at a value p1 before time t1. The state in which the load of each of the four wheels is constant at a value p1 corresponds to the state in which the stroller 100 is moving with each of the four wheels in contact with the ground.

[0043] Next, in the period from time t1 to time t2, the loads on the left and right rear wheels increase from value p1 to value p2, and the loads on the left and right front wheels decrease from value p1 to zero. Next, in the period from time t2 to time t3, the loads on the left and right front wheels increase from zero to a value p2, and the loads on the left and right rear wheels decrease from the value p2 to zero. Next, after time t3, the load on each of the four wheels becomes constant at approximately the value p1, similar to the load before time t1.

[0044] Such a load change pattern is obtained when the stroller 100 moves over a step on the ground that has a height difference that allows the front wheel to be lifted up. That is, the user U moves the stroller 100 forward with the front wheels temporarily lifted off the ground from time t1 to time t2, moves the stroller 100 forward while lowering the front wheels to the higher side of the step and lifting the rear wheels off the ground from time t2 to time t3, and at time t3, the front and rear wheels touch the ground at a point beyond the step. Therefore, in this case, when the load change pattern of Figure 7 is obtained, the ground condition estimation unit 222 may estimate that the ground condition is such that, for example, a step exists with time t2 as the boundary, where the side corresponding to time t1 is lower and the side corresponding to time t3 is higher.

[0045] Next, in the load change pattern in Figure 8, before time t11, the load on each of the four wheels is constant at approximately the value p1, and after time t11, the load on each of the four wheels becomes zero for a certain period of time. Such a load change pattern corresponds to a situation where the user U is lifting the stroller 100 while moving in a place where the stroller 100 cannot be pushed, such as stairs. Therefore, when the load change pattern in Figure 8 is obtained, the ground condition estimation unit 222 may estimate, as the ground condition, that a staircase exists in a position range corresponding to the time from time t11 onwards where the load on each of the four wheels is zero.

[0046] Next, the load change pattern in Fig. 9 shows that the loads on the four wheels change at short time intervals, fluctuating relatively significantly around the value p1. Such a load change pattern occurs when the stroller 100 moves over a highly uneven surface such as gravel. Therefore, the ground condition estimation unit 222 may estimate that the ground condition at the position corresponding to the time when the load change pattern in Fig. 9 is obtained is one in which the ground condition is highly uneven and the ride comfort is not good.

[0047] It should be noted that the load change patterns shown in Figures 7 to 9 are merely examples, and the ground condition estimation unit 222 may estimate various ground conditions based on various load change patterns other than those shown in Figures 7 to 9. For example, the ground condition estimation unit 222 may be configured to estimate the conditions of mud, sand, uneven roads, etc. in addition to steps, stairs, and places with large unevenness, based on various load change patterns.

[0048] Let us return to the explanation given in FIG. Step S304: The ground condition estimation unit 222 reflects the estimation result about the ground in step S302 in the ground condition map stored in the ground condition map storage unit 232.

[0049] In response to an access from a user terminal 300, the control unit 202 of the ground condition estimation device 200 transmits a ground condition map reflecting the above-mentioned ground condition estimation result to the accessing user terminal 300. The user terminal 300 displays the transmitted ground condition map.

[0050] As described above, in this embodiment, the ground condition estimation device 200 estimates the ground condition by using the load history information transmitted from the stroller 100. In this case, even without using personnel to investigate the site, for example, it is possible to estimate the ground condition in various locations by each user U who is a guardian of an infant or small child using the stroller 100 in the city, and create a ground condition map showing the estimated ground condition. In other words, in this embodiment, it is possible to efficiently estimate the ground condition related to the movement of the stroller 100.

[0051] In addition, the ground condition estimation device 200 can efficiently estimate ground conditions over a wide range by using the load history information transmitted from a plurality of strollers 100 moving around in various locations.

[0052] The ground condition estimation unit 222 of the ground condition estimation device 200 may obtain an estimation result of one ground condition at a position by using a load change pattern indicated by load history information obtained at different times from one or more strollers 100 corresponding to the same position. In this case, it is possible to remove noise such as outliers, for example, and therefore to obtain an estimation result with high accuracy.

[0053] The ground condition estimation unit 222 may estimate the ground condition using a trained model. Such a trained model may be constructed, for example, by having a learning device learn the relationship between various load change patterns and the ground condition.

[0054] In the above embodiment, the stroller 100 has four wheels, a pair of left and right front wheels and a pair of rear wheels, and the load sensor 101 is provided for each of the four wheels. However, the load sensor 101 may be provided for two wheels, for example, one of the two front wheels (left or right) and one of the two rear wheels (left or right). In addition, the number of wheels on the stroller 100 may be other than four, for example, three wheels consisting of one front wheel and two rear wheels (one on each side), and the load sensor 101 may be appropriately installed on a specified wheel depending on the relationship between the number of wheels and the position at which the stroller 100 is attached, etc.

[0055] The configuration of the ground condition estimation system in this embodiment is not limited to the above example. For example, the stroller 100 may be equipped with a ground condition estimation unit 222 to estimate the ground condition for each position measured by the positioning unit 102, and transmit the estimation results to the ground condition estimation device 200. In this case, the ground condition estimation device 200 may reflect the received estimation results of the ground condition in the ground condition map stored in the ground condition map storage unit 232. Also, for example, the current position of the stroller 100 may be measured by a user terminal 300 carried by a user U. In this case, for example, the stroller 100 and the user terminal 300 may be connected by short-range wireless communication such as Bluetooth. Then, the stroller 100 may transmit the load detected by the load sensor 101 to the user terminal 300, and the user terminal 300 may store the load history information by associating the position information measured by itself with the received load at a time, and transmit the load history information to the ground condition estimation device 200 at a predetermined timing. Alternatively, in the opposite manner to the above, the user terminal 300 may transmit its own measured position information to the stroller 100, and the stroller 100 may store load history information by correlating the load detected by the load sensor 101 and the position information received from the user terminal 300 with time, and transmit the load history information to the ground condition estimation device 200 at a predetermined timing. Furthermore, in each of the above configurations, the stroller 100 or the user terminal 300 may create and store a ground condition map that reflects the ground condition estimation results. The stored ground condition map may be displayed, for example, on a display unit provided in the stroller 100 or a display unit of the user terminal 300. In this case, since the stroller 100 or the user terminal 300 has the function of the ground condition estimation device 200, the ground condition estimation device 200 on the network may be omitted.

[0056] It should be noted that the pushcart that this embodiment is compatible with is not limited to the stroller 100. The pushcart that this embodiment is compatible with may be, for example, a suitcase with wheels, a shopping cart, a pushcart for the elderly, a wheelchair, or the like.

[0057] In addition, a program for realizing the functions of the above-mentioned stroller 100, ground condition estimation device 200, user terminal 300, etc. may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed to perform the above-mentioned processing of the stroller 100, ground condition estimation device 200, user terminal 300, etc. Here, "reading a program recorded on a recording medium into a computer system and executing it" includes installing the program into a computer system. The "computer system" here includes hardware such as an OS and peripheral devices. In addition, the "computer system" may include multiple computer devices connected via a network including the Internet, a WAN, a LAN, a dedicated line, and other communication lines. In addition, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, an optical magnetic disk, a ROM, a CD-ROM, etc., and a storage device such as a hard disk built into a computer system and an SSD. In this way, the recording medium storing the program may be a non-transient recording medium such as a CD-ROM. In addition, the recording medium also includes a recording medium provided inside or outside and accessible from a distribution server to distribute the program. The code of the program stored in the recording medium of the distribution server may be different from the code of the program in a format executable by the terminal device. In other words, the format in which the program is stored in the distribution server does not matter as long as it can be downloaded from the distribution server and installed in a format executable by the terminal device. The program may be divided into multiple parts, downloaded at different times, and then combined on the terminal device, or each of the divided programs may be distributed by a different distribution server. Furthermore, the "computer-readable recording medium" includes a memory that holds a program for a certain period of time, such as a volatile memory (RAM) inside a computer system that becomes a server or a client when a program is transmitted via a network. The above program may also be for realizing part of the above-mentioned functions.Furthermore, the above-mentioned functions may be realized in combination with a program already recorded in the computer system, that is, a so-called differential file (differential program).

[0058] The "Sustainable Development Goals (SDGs)" are 17 international goals that were adopted at the United Nations Summit in September 2015. The ground condition estimation system of this embodiment can contribute to achieving one of the 17 SDGs, for example goal 9 "Build resilient infrastructure, promote industry, innovation and infrastructure." [Explanation of symbols]

[0059] 100 Stroller, 101 (101-FL, 101-FR, 101-RL, 101-RR) Load sensor, 102 Positioning unit, 103 Memory unit, 104 Communication unit, 105 Control unit, 112 Control unit, 131 Load history information memory unit, 200 Ground condition estimation device, 201 Communication unit, 202 Control unit, 203 Memory unit, 221 Load history information acquisition unit, 222 Ground condition estimation unit, 231 Load history information memory unit, 232 Ground condition map memory unit, 300 User terminal

Claims

1. A load sensor for detecting a load applied to a wheel of the handcart; A positioning unit for measuring the position of the handcart; a ground condition estimating unit that associates the position of the handcart measured by the positioning unit with the time at which the load of the load sensor is detected, and estimates the ground condition at the position at which the change pattern is obtained based on a change pattern of the load detected by the load sensor over time; A ground condition estimation system comprising:

2. the load sensor is provided to individually detect loads applied to the front wheels and the rear wheels of a handcart having front wheels and rear wheels, The ground condition estimating unit estimates the ground condition at a position on the map where the change pattern is obtained, based on a change pattern of the load on the front wheels and the load on the rear wheels over the same time period. The ground condition estimation system of claim 1 .

3. The ground condition estimation unit may further include a map providing unit that displays, on a terminal device, a ground condition map indicating the ground condition estimated by the ground condition estimation unit. The ground condition estimation system according to claim 1 or 2.

4. 1. A ground condition estimation method for a ground condition estimation system, comprising: a ground condition estimating step of associating a position of the handcart measured by a positioning unit that measures the position of the handcart with a time at which a load was detected by a load sensor that detects a load applied to a wheel of the handcart, and estimating a ground condition at a position where the change pattern was obtained based on a change pattern of the load detected by the load sensor over time. A ground state estimation method comprising:

5. a ground condition estimating section which associates a position of the handcart measured by a positioning section which measures the position of the handcart with a time at which a load is detected by a load sensor which detects a load applied to a wheel of the handcart, and which estimates a ground condition at a position where a change pattern is obtained based on a change pattern of the load detected by the load sensor according to the passage of time. A ground condition estimation device comprising:

6. A computer as a ground condition estimation device, a ground condition estimating section which associates a position of the handcart measured by a positioning section which measures the position of the handcart with a time at which a load is detected by a load sensor which detects a load applied to a wheel of the handcart, and which estimates a ground condition at a position where a change pattern is obtained based on a change pattern of the load detected by the load sensor according to the passage of time. A program to function as a

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