Patent Description:
In recent years, application of autonomous transport vehicles has been advanced in order to promote labor saving and automation of distribution and production. In many cases, an autonomous transport vehicle travels on a flat traveling road in a distribution warehouse or a production plant. Further, in order to handle a transported object having a weight exceeding the maximum load weight, the autonomous transport vehicle may travel while towing the transported object. In order for an autonomous transport vehicle to travel and transport stably, in addition to a traveling driving force corresponding to weights of a vehicle body and a transported object, a ground contact load sufficient to prevent traveling wheels from slipping (idling) is required. An example of a technique related to this type of autonomous transport vehicle is disclosed in Patent Literature <NUM>. A height of the bottom plate of a transported carriage disclosed in Patent Literature <NUM> is chosen in combination with an unmanned transfer vehicle comprising a biasing portion with predetermined lifting characteristics depending on the weight to be transported. Patent Literature <NUM> discloses the preamble of claims <NUM> and <NUM>. Patent Literature <NUM> discloses a transport vehicle with a primary chassis and a secondary chassis, both with their own set of wheels. A weight of a transported load is carried by the secondary chassis, but if it exceeds a certain threshold weight, the suspension of the secondary is compressed, so that the secondary chassis abuts on the primary chassis.

An autonomous transport vehicle disclosed in Patent Literature <NUM> includes a drive unit having a right wheel, a left wheel, and a wheel driver, a turning shaft mechanism that turnably supports the drive unit with respect to a top plate, and a coil spring disposed in a vertical direction around the turning shaft mechanism in order to apply a force applied to the top plate to the right wheel and the left wheel. According to this, it is considered that ground contact loads of the right wheel and the left wheel are made substantially uniform, and traveling stability of the autonomous transport vehicle can be improved.

A case where an autonomous transport vehicle travels on an inclined traveling road (slope) is also assumed. In this case, a larger traveling driving force and a larger ground contact load are required as compared with a flat traveling road. Here, in a case where an own weight of a vehicle body is increased in order to secure the larger ground contact load, an even larger traveling driving force is required, and the autonomous transport vehicle becomes heavy and large. Further, even on a flat traveling road, in a case where a road surface is wet, a coefficient of friction decreases, so that traveling wheels easily slip (idle), and the same problem occurs. Further, in an autonomous transport vehicle of a type in which a current position is estimated based on a driving amount of traveling wheels, estimation accuracy of the current position is reduced because of a slip of the traveling wheels.

The above problem also occurs in the same way in a case where an autonomous transport vehicle travels while towing the transported object. In addition, in a case where a weight (load) acting on a vehicle body from the transported object is small because of dependence on a form of towing, it is difficult to secure a sufficient ground contact load of traveling wheels. Conversely, in a case where the weight acting on the vehicle body from the transported object is excessive and exceeds the maximum load weight, there is a concern that travel is destabilized or the vehicle body or the traveling wheels is damaged.

Therefore, an object of the present description is to provide an autonomous transport vehicle and a towing and transportation method capable of securing a stable ground contact load of a traveling wheel and transporting a transported object while towing the transported object even in a case where a total weight of the transported object is different on a case-by-case basis.

The problem is solved by an autonomous transport vehicle as defined by appended claim <NUM> and a towing and transportation method according to appended claim <NUM>.

In the autonomous transport vehicle and the towing and transportation method according to the invention, the vehicle body is caused to enter the lower side of the transported object, and the partial weight of the transported object is caused to act on the vehicle body from the transported object, so that a large load obtained by adding the partial weight of the transported object to an own weight of the vehicle body acts as a ground contact load of the traveling wheel. Accordingly, even in a case where the total weight of the transported object is different on a case-by-case basis, it is possible to secure a stable ground contact load of the traveling wheel to suppress a slip (idling), and it is possible to transport the transported object while towing the transported object.

First, an overall configuration of autonomous transport vehicle <NUM> according to an embodiment will be described with reference to <FIG>. As indicated by an upper right arrow in <FIG>, front, rear, right, and left sides of autonomous transport vehicle <NUM> are defined for convenience. Autonomous transport vehicle <NUM> performs one of traveling with loading transported object <NUM> and traveling while towing transported object <NUM> based on a total weight and shape of transported object <NUM> different on a case-by-case basis. Autonomous transport vehicle <NUM> operates according to a transportation command including individual identification information of transported object <NUM> and a current position and target position of transported object <NUM>. Autonomous transport vehicle <NUM> includes vehicle body <NUM> and weight acting portion <NUM>.

Vehicle body <NUM> includes loading platform portion <NUM> on a front side and driving portion <NUM> on a rear side. Loading platform portion <NUM> is formed in a thin rectangular parallelepiped shape that has a substantially rectangular shape elongated in a front-rear direction in plan view and has a small height dimension. Loading platform portion <NUM> enters a lower side of transported object <NUM> to be transported. Driving portion <NUM> is formed in a vertically long rectangular parallelepiped shape that has the same width dimension as a width dimension of loading platform portion <NUM> in a right-left direction, has a substantially rectangular shape elongated in the right-left direction in plan view, and has a large height dimension. For loading platform portion <NUM> and driving portion <NUM>, heights of bottom surfaces have been aligned.

Vehicle body <NUM> has four traveling wheels <NUM>. As illustrated in <FIG> and <FIG>, two traveling wheels <NUM> on the front side are disposed in a forward position of the bottom surface of loading platform portion <NUM>. Two traveling wheels <NUM> on the rear side are disposed on the bottom surface around a boundary between loading platform portion <NUM> and driving portion <NUM>. As traveling wheels <NUM>, four omni wheels that are driven independently by different drive motors and have different axle directions at a pitch of <NUM>° can be used.

In this aspect, four traveling wheels <NUM> (omni wheels) can rotate in mutually different rotation directions, and can rotate at mutually different rotation speeds. Accordingly, a traveling direction of autonomous transport vehicle <NUM> is free. In addition, autonomous transport vehicle <NUM> is capable of traveling in various forms such as steering and spin turning. The number, a type, and an arrangement of traveling wheels <NUM> can be changed in various ways, without being limited thereto.

Further, Vehicle body <NUM> includes battery <NUM>, control section <NUM>, manual operation section <NUM>, emergency stop buttons (<NUM> and <NUM>), and acquisition section <NUM>. Battery <NUM> is disposed in a lower portion inside a housing of driving portion <NUM>. The disposition of battery <NUM> having a large weight in a lower portion lowers a position of the center of gravity of vehicle body <NUM> and improves stability. Battery <NUM> supplies power to the drive motors of traveling wheels <NUM>, control section <NUM>, and drive section <NUM> (described later) of weight acting portion <NUM>.

Control section <NUM> is disposed in an upper portion inside the housing of driving portion <NUM>. Control section <NUM> controls operations of the drive motors of traveling wheels <NUM> and operation of weight acting portion <NUM> according to a transportation command (details will be described later). Further, control section <NUM> obtains a current position of autonomous transport vehicle <NUM> based on a detection result of a position marker using a sensor (not shown) or the like, and further determines a future traveling route. In addition, control section <NUM> also estimates the current position based on a driving amount of traveling wheels <NUM>. Accordingly, in a case where a ground contact load of traveling wheels <NUM> is insufficient and a slip (idling) occurs, estimation accuracy of the current position decreases.

Manual operation section <NUM> is disposed on a left side of an upper surface of driving portion <NUM>, and is connected to control section <NUM>. Manual operation section <NUM> functions in a case where a predetermined safety condition is satisfied, and a command by a manual operation of a worker is input thereto. The predetermined safety condition is satisfied, for example, in a case where a temporary stop command is transmitted to autonomous transport vehicle <NUM> and autonomous transport vehicle <NUM> temporarily stops. Further, as a command based on a manual operation, a command for canceling a transportation command set in advance in autonomous transport vehicle <NUM>, a command for changing a target position, or the like can be exemplified.

First emergency stop button <NUM> is disposed at a left rear end of the upper surface of driving portion <NUM>. Second emergency stop button <NUM> is disposed on a front surface of loading platform portion <NUM>. In a case where emergency stop button (<NUM> or <NUM>) is pressed by the worker or another person, a power supply circuit connecting the drive motors of traveling wheels <NUM> and battery <NUM> is cut off, and autonomous transport vehicle <NUM> stops in an emergency. Further, an approach detection sensor (not shown) may be provided in vehicle body <NUM>. The approach detection sensor detects an approach of another autonomous transport vehicle <NUM>, the worker, or the like and outputs a detection signal to control section <NUM>. Upon receiving the detection signal, control section <NUM> stops autonomous transport vehicle <NUM> or reduces a traveling speed. Accordingly, interference between autonomous transport vehicles <NUM> and contact between autonomous transport vehicle <NUM> and the worker are avoided.

Acquisition section <NUM> is disposed on a left side of emergency stop button <NUM> on the front surface of loading platform portion <NUM>. Acquisition section <NUM> acquires the individual identification information for identifying an individual of transported object <NUM>. In the present embodiment, a two-dimensional code indicating individual identification information is displayed on transported object <NUM>. Meanwhile, a camera can be used as acquisition section <NUM>. Acquisition section <NUM> (camera) acquires the individual identification information by imaging and reading the two-dimensional code displayed on transported object <NUM>. Acquisition section <NUM> can perform an imaging operation while moving with respect to transported object <NUM> while autonomous transport vehicle <NUM> is traveling. Acquisition section <NUM> sends the acquired individual identification information to control section <NUM>.

Note that acquisition section <NUM> including a camera may also be used for detecting an obstacle in front during traveling. Further, acquisition section <NUM> is not limited to the above-described camera. For example, transported object <NUM> may include a wireless tag that transmits a wireless signal indicating the individual identification information, and acquisition section <NUM> may be a wireless reception section that receives the wireless signal.

The maximum load weight of autonomous transport vehicle <NUM> is determined in consideration of traveling stability of autonomous transport vehicle <NUM>, mechanical strength of vehicle body <NUM> and traveling wheels <NUM>, and the like. Further, the maximum towing weight is determined in consideration of traveling driving forces of the drive motors that drives traveling wheels <NUM>, an own weight of vehicle body <NUM>, and the like. Further, the maximum load weight or the maximum towing weight may be determined in consideration of the maximum inclination angle or quality of a road surface condition of a traveling road on which autonomous transport vehicle <NUM> travels. Of course, the maximum towing weight is larger than the maximum load weight. In a case where autonomous transport vehicle <NUM> travels while towing transported object <NUM> having a relatively large total weight, it is important to appropriately maintain the ground contact load of traveling wheels <NUM> from the viewpoint of traveling stability.

Next, a configuration of weight acting portion <NUM> will be described with reference to <FIG>. Weight acting portion <NUM> is provided on an upper portion of loading platform portion <NUM> and enters the lower side of transported object <NUM>. Weight acting portion <NUM> causes the total weight or partial weight of transported object <NUM> to act on loading platform portion <NUM> of vehicle body <NUM> from transported object <NUM>. To cause the total weight of transported object <NUM> to act on loading platform portion <NUM> means transportation with loading. To cause a partial weight of transported object <NUM> to act on loading platform portion <NUM> means that a remaining weight is borne by transported object <NUM> itself, in other words, transportation while towing transported object <NUM>. Weight acting portion <NUM> includes common base <NUM>, four sets of elastic support portions <NUM>, drive section <NUM> (refer to <FIG>), and the like, and two connecting members <NUM> are attached thereto.

Common base <NUM> is a substantially rectangular plate-shaped member that occupies the majority of an upper surface area of loading platform portion <NUM>. Common base <NUM> is formed of a thick member, and has high rigidity due to addition of a reinforcing member. In a case of being driven by drive section <NUM>, common base <NUM> is lifted and lowered while maintaining a horizontal state. Common base <NUM> is lowered (refer to <FIG>) under a normal condition, and is driven to be lifted in a case of transporting transported object <NUM> (refer to <FIG>). As drive section <NUM>, a combination of a motor and a cam mechanism can be exemplified, and another mechanism such as a hydraulic drive mechanism can also be used.

Four sets of elastic support portions <NUM> are respectively disposed in the vicinity of four corners of common base <NUM>. The number of sets of elastic support portions <NUM> is not limited to four sets, and can be changed. Elastic support portions <NUM> are provided on loading platform portion <NUM> via common base <NUM> so as to be capable of being lifted and lowered, and support transported object <NUM> from the lower side via elastic body <NUM>. As illustrated in <FIG>, each of elastic support portions <NUM> includes base body <NUM>, support body <NUM>, and elastic body <NUM>.

Base body <NUM> is formed of base member <NUM>, bottom plate member <NUM>, cylinder member <NUM>, and the like. Base member <NUM> is formed to have a large bottom portion and a small upper portion, and a reinforcing stay whose reference numeral is omitted is added. The bottom portion of base member <NUM> is fixed to common base <NUM>. Bottom plate member <NUM> is a rectangular plate-shaped member. Bottom plate member <NUM> is horizontally fixed to an upper side of base member <NUM>. Support pin <NUM> is disposed to stand upward at a center of bottom plate member <NUM> and is fixed using a fastening screw whose reference numeral is omitted. Cylinder member <NUM> is a member which has a central axis extending in a vertical direction and in which cylinder space <NUM> having an opening in an up-down direction is formed. Cylinder member <NUM> is fixed to an upper side of bottom plate member <NUM>. Cylinder space <NUM> is formed in a stepped cylindrical shape having small-diameter portion <NUM> on an upper side and a large-diameter portion <NUM> on a lower side.

Support body <NUM> is formed of piston member <NUM>, support member <NUM>, and the like. Piston member <NUM> is a bottomed cylindrical member having a central axis common to cylinder member <NUM>. Specifically, piston member <NUM> has bottom portion <NUM> at an upper portion of cylindrical portion <NUM>, and a lower portion of cylindrical portion <NUM> is flange <NUM> having an increased diameter. Support member <NUM> is a circular plate-shaped member. Support member <NUM> is horizontally disposed on an upper side of bottom portion <NUM> of piston member <NUM>, and is fixed using a fastening screw whose reference numeral is omitted. Support member <NUM> supports a bottom portion of transported object <NUM> (a lower surface of bottom plate <NUM>) from below.

A lower portion of piston member <NUM> constituting support body <NUM> is disposed in cylinder space <NUM> of cylinder member <NUM> so as to be capable of being lifted and lowered. Further, support member <NUM> constituting support body <NUM> is disposed above cylinder member <NUM>. Bottom portion <NUM> and cylindrical portion <NUM> of piston member <NUM> can be lifted and lowered in small-diameter portion <NUM>. Meanwhile, flange <NUM> of piston member <NUM> can be lifted and lowered in large-diameter portion <NUM>, but cannot enter small-diameter portion <NUM>. This prevents support body <NUM> from being detached upward.

Elastic body <NUM> is provided between base body <NUM> and support body <NUM>. Specifically, elastic body <NUM> is used in a form in which a coil spring (shown in a cylindrical shape for convenience in <FIG>) capable of expanding and contracting in the up-down direction is applied and a stress is generated by compression. A lower end of elastic body <NUM> is supported by engagement of support pin <NUM> of base body <NUM>. An upper end of elastic body <NUM> is pressed against bottom portion <NUM> of support body <NUM>. An intermediate portion of elastic body <NUM> is held inside cylindrical portion <NUM> of support body <NUM>, and is prevented from being deformed in a direction other than an expansion and contraction direction. In manufacture of elastic support portion <NUM>, after piston member <NUM> and elastic body <NUM> are incorporated into cylinder member <NUM>, bottom plate member <NUM> with support pin <NUM> and support member <NUM> are attached.

As illustrated in <FIG>, a stress generated in elastic body <NUM> is small at a lifted position of support body <NUM> in which flange <NUM> is located at an upper end of large-diameter portion <NUM>. Meanwhile, in a case where elastic support portion <NUM> is driven to be lifted, support body <NUM> is lifted at the beginning. In a case where support body <NUM> is further lifted and comes into contact with the lower side of transported object <NUM>, support body <NUM> cannot be lifted thereafter. In a case where elastic support portion <NUM> is further driven to be lifted, support body <NUM> maintains a height thereof, and is relatively lowered with reference to base body <NUM>.

Accordingly, bottom portion <NUM> of support body <NUM> receiving the weight of transported object <NUM> presses elastic body <NUM> downward to compress elastic body <NUM>. As illustrated in <FIG>, support body <NUM> can be lowered to a predetermined lowered position with reference to base body <NUM>. At a predetermined lowered position, support member <NUM> is lowered by lowering stroke length DS (refer to <FIG>) and comes into contact with cylinder member <NUM>. At the same time, flange <NUM> is lowered to the vicinity of a lower end of large-diameter portion <NUM>. Alternatively, flange <NUM> may be lowered to the lower end of large-diameter portion <NUM> and come into contact with bottom plate member <NUM>, and support member <NUM> may be lowered to a position close to cylinder member <NUM>.

In a case where support body <NUM> is lowered to the lowered position, elastic body <NUM> is compressed by lowering stroke length DS, and a stress equal to a predetermined weight is generated. This stress has a magnitude that is balanced with the weight acting on support body <NUM> from transported object <NUM>. This stress acts on loading platform portion <NUM> via base body <NUM> and common base <NUM>.

In the present embodiment, the predetermined weight is determined to be one fourth of the maximum load weight of autonomous transport vehicle <NUM>. In other words, a sum of the predetermined weights of four elastic bodies <NUM> matches the maximum load weight. Accordingly, stresses equal to the maximum load weight in total is generated in four elastic bodies <NUM>. In this case, an amount corresponding to the maximum load weight of the weight of transported object <NUM> acts on loading platform portion <NUM> from transported object <NUM> via elastic support portion <NUM>. A sum of the amount corresponding to the maximum load weight of transported object <NUM> and the own weight of vehicle body <NUM> acts on four traveling wheels <NUM> to be the ground contact load.

Note that various factors such as a spring constant and lowering stroke length DS of elastic body <NUM> are designed such that the above-described stress is generated. Even in this case, the stress generated in four elastic bodies <NUM> may include some manufacturing errors resulting from a dimensional tolerance of the members, an operation error during an assembly operation, or the like.

Further, in a case where a lifting amount of elastic support portion <NUM> is small, support body <NUM> is lowered by a stroke length shorter than lowering stroke length DS with reference to base body <NUM>. In other words, support body <NUM> may stop in the middle of being lowered, instead of being lowered to the predetermined lowered position. In this case, stresses equal to a partial weight smaller than the maximum load weight in total is generated in four elastic bodies <NUM>. In this case, an amount corresponding to the partial weight of the total weight of transported object <NUM> acts on loading platform portion <NUM> from transported object <NUM>. A sum of the amount corresponding to the partial weight of transported object <NUM> and the own weight of vehicle body <NUM> acts on four traveling wheels <NUM> to be the ground contact load.

Two connecting members <NUM> respectively connect two front and rear base bodies <NUM>. As connecting member <NUM>, for example, square rod-shaped section steel is used. Connecting member <NUM> is fastened to front and rear base bodies <NUM> (cylinder members <NUM>) using two fastening bolts <NUM>. Connecting member <NUM> is provided to increase mechanical rigidity. Four connecting members <NUM> may be disposed to be a rectangular shape, and right and left base bodies <NUM> may be connected together. Each of connecting members <NUM> has pressing portions <NUM> at two positions on an upper surface. Pressing portion <NUM> is provided to stand upward from the upper surface of connecting member <NUM>, and is formed in, for example, a conical shape or a round rod shape. An upper end of pressing portion <NUM> extends to a position higher than an upper surface of support body <NUM> (support member <NUM>).

As illustrated in <FIG>, bottom plate <NUM> of transported object <NUM> is formed with contacted portion <NUM> protruding downward in a lattice shape. In a case where loading platform portion <NUM> enters the lower side of transported object <NUM>, common base <NUM> is lowered, and pressing portion <NUM> passes a lower side of contacted portion <NUM>. Thereafter, in a case where weight acting portion <NUM> operates, connecting member <NUM> is lifted integrally with common base <NUM> and base body <NUM>. Accordingly, pressing portion <NUM> is lifted to a height of contacted portion <NUM>. Then, as vehicle body <NUM> travels, pressing portion <NUM> comes into contact with contacted portion <NUM> from a lateral side and presses transported object <NUM>. According to this, in both cases of loading and towing, transported object <NUM> does not go through a significant lateral skid with respect to four elastic support portions <NUM>, and is stably transported.

Here, there are cases where autonomous transport vehicle <NUM> is traveling and suddenly stops because of some reasons. In this case, a large inertial force in a horizontal direction is generated because of a sudden stop of transported object <NUM>, and acts on pressing portion <NUM> from contacted portion <NUM>. In this case, since the large inertial force is divided and transmitted from pressing portion <NUM> to front and rear base bodies <NUM> via connecting member <NUM>, a deformation amount of front and rear elastic support portions <NUM> is small, and there is no concern of breakage. That is, by providing connecting member <NUM>, it is possible to increase the mechanical rigidity against the large inertial force from transported object <NUM> generated in a case where autonomous transport vehicle <NUM> suddenly stops.

Next, an example of transported object <NUM> will be described with reference to <FIG>. In the present embodiment, transported object <NUM> is a roll container on which multiple packages can be placed, and is not limited thereto. As illustrated in <FIG>, transported object <NUM> (roll container) includes bottom plate <NUM>, two side plates <NUM>, top plate <NUM>, two inventory plates <NUM>, and curtain <NUM>. Bottom plate <NUM>, two side plates <NUM>, and top plate <NUM> form a rectangular parallelepiped frame that has openings in front and rear.

Bottom plate <NUM> has contacted portion <NUM> described above and four casters <NUM> whose traveling directions freely change. Further, the two-dimensional code (not shown) described above is displayed on front and rear sides of bottom plate <NUM>. A height of a bottom surface of bottom plate <NUM> varies depending on individual differences of transported objects <NUM>. Two inventory plates <NUM> are disposed horizontally while being vertically separated so as to divide an inside of the frame into approximately three equal parts. Packages are placed on upper surfaces of two inventory plates <NUM> and bottom plate <NUM>. Curtain <NUM> is formed using a transparent and flexible resin sheet. Curtain <NUM> is disposed so as to cover front and rear sides of the frame in an openable and closable manner.

The total weight of transported object <NUM> is obtained by adding an own weight of transported object <NUM> to a weight of the packages placed thereon. Accordingly, the total weight of transported object <NUM> varies depending on a type and the number of the packages placed on a case-by-case basis. Further, there are multiple types of transported objects <NUM> having different height dimensions. A height dimension of transported object <NUM> illustrated in <FIG> is close to four times a height dimension of autonomous transport vehicle <NUM>, and it cannot be said that stability is good in a case where transported object <NUM> is loaded and transported. Accordingly, even in a case where transported object <NUM> is unloaded and the total weight of transported object <NUM> is smaller than the maximum load weight, autonomous transport vehicle <NUM> tows that transported object <NUM> without loading that transported object <NUM> and performs stable transportation.

In <FIG>, casters <NUM> of transported object <NUM> are oriented in a right-left direction of the drawing, and autonomous transport vehicle <NUM> travels on road surface RD while towing unloaded transported object <NUM> in the right-left direction. In a case where the traveling direction of autonomous transport vehicle <NUM> changes, a traveling direction of casters <NUM> also changes accordingly, so that autonomous transport vehicle <NUM> can stably travel even while towing transported object <NUM>. Meanwhile, autonomous transport vehicle <NUM> transports a transported object having a relatively small height dimension and a total weight smaller than the maximum load weight by elevating the transported object from road surface RD and loading the transported object.

Next, a configuration related to control of autonomous transport vehicle <NUM> will be described with reference to <FIG> together with management of transported object <NUM>. As illustrated in <FIG>, control section <NUM> separately controls the four drive motors so as to separately control the rotation directions and the rotation speeds of four traveling wheels <NUM>. Further, control section <NUM> is connected to manual operation section <NUM>, and receives a command by a manual operation of the worker. Further, control section <NUM> is connected to acquisition section <NUM> and receives the individual identification information of transported object <NUM> acquired by acquisition section <NUM>. Further, control section <NUM> controls drive section <NUM> of weight acting portion <NUM>.

Further, control section <NUM> is wirelessly communicably connected to transported object management section <NUM>. Transported object management section <NUM> manages operating of multiple transported objects <NUM> using transported object data DC illustrated in <FIG>. Transported object data DC is set for each of multiple transported objects <NUM>. Transported object data DC has a data format in which individual identification information ID is associated with other management information. In the present embodiment, the other management information includes seven items: current position information P1, target position information P2, package name NM, package weight information W2, own weight information W1, bottom portion height information HT, and loading possibility information YN.

Individual identification information ID is information displayed on each of transported objects <NUM> as described above and acquired by acquisition section <NUM>. Current position information P1 is information indicating the current position of transported object <NUM>. As an expression format of current position information P1, for example, two-dimensional coordinate values of a field in which autonomous transport vehicle <NUM> travels or position numbers of multiple stop positions at which transported object <NUM> is stopped or stored are used. Each position number is associated in advance with a two-dimensional coordinate value of the field. Target position information P2 is information indicating a position of a transport destination to which autonomous transport vehicle <NUM> transports transported object <NUM>. Target position information P2 is blank in a case where it is not necessary to transport transported object <NUM>, and is set in a case where transported object <NUM> is transported. Target position information P2 is expressed in the same expression format as current position information P1.

Package name NM is information obtained by encoding a name of the package placed on transported object <NUM>. Package weight information W2 is information corresponding to an added value obtained by adding each weight of the multiple packages placed on transported object <NUM>. Package name NM and Package weight information W2 are sequentially updated by the worker or a work robot in a case where the worker or the work robot loads and unloads the packages. The four items are changing information that changes with time: current position information P1, target position information P2, package name NM, and package weight information W2.

Own weight information W1 is information on the own weight of transported object <NUM>. The total weight of transported object <NUM> can be automatically obtained by adding own weight information W1 and package weight information W2. Bottom portion height information HT is information indicating a height from road surface RD of each bottom plate <NUM> of transported objects <NUM> having individual differences. Loading possibility information YN is information that determines whether transportation with loading is possible. For example, for transported object <NUM> having a large height dimension (refer to <FIG>), loading possibility information YN is set to "impossible to transport with loading". The three items are fixed information that does not change under a normal condition and may change in a case where transported object <NUM> is modified or repaired: own weight information W1, bottom portion height information HT, and loading possibility information YN.

Transported object management section <NUM> transmits a transportation command including transported object data DC in which target position information P2 is set to autonomous transport vehicle <NUM>. Autonomous transport vehicle <NUM> transports transported object <NUM> based on transported object data DC included in the transportation command. Transported object management section <NUM> may transmit a transportation command including multiple pieces of transported object data DC, and autonomous transport vehicle <NUM> may sequentially transport multiple transported objects <NUM> in accordance with an arrangement order of the multiple pieces of transported object data DC.

Next, the operation of autonomous transport vehicle <NUM> will be described with reference to <FIG>. The following description includes description of a towing and transportation method of the embodiment. An operation flow illustrated in <FIG> is advanced mainly under the control of control section <NUM>. In step S1 of <FIG>, control section <NUM> receives a transportation command from transported object management section <NUM>. In next step S2, control section <NUM> determines a transportation method for transported object <NUM> based on transported object data DC included in the transportation command. Specifically, control section <NUM> determines whether to load transported object <NUM> or to tow transported object <NUM>, and determines an operation condition of weight acting portion <NUM> in a case of towing transported object <NUM>.

Specifically, in a case where loading possibility information YN included in transported object data DC indicates that "impossible to transport with loading", control section <NUM> determines to tow transported object <NUM>. Further, in a case where loading possibility information YN indicates "possible to transport with loading", control section <NUM> determines to load transported object <NUM> in a case where the total weight of transported object <NUM> is equal to or less than the maximum load weight, and determines to tow transported object <NUM> in a case where the total weight of transported object <NUM> exceeds the maximum load weight. Further, for example, in a case where the total weight of transported object <NUM> exceeds the maximum towing weight, control section <NUM> notifies transported object management section <NUM> that transported object <NUM> cannot be transported, and ends the operation flow.

In a case where it is determined that transported object <NUM> is loaded, control section <NUM> determines a lifting amount that is large enough to elevate transported object <NUM> from road surface RD as a lifting amount by which drive section <NUM> of weight acting portion <NUM> causes common base <NUM> to be lifted. Further, in a case where it is determined that transported object <NUM> is towed, control section <NUM> determines a lifting amount by which drive section <NUM> causes common base <NUM> to be lifted based on the total weight of transported object <NUM> and bottom portion height information HT. Determination patterns include following (<NUM>), (<NUM>), and (<NUM>), and (<NUM>) may be merged into (<NUM>).

(<NUM>) In a case where the total weight of transported object <NUM> exceeds the maximum load weight (predetermined weight), control section <NUM> adds lowering stroke length DS to a separation distance between support body <NUM> and bottom plate <NUM> of transported object <NUM> to obtain a lifting amount. In this case, in a case where common base <NUM> is lifted, as illustrated in <FIG>, support body <NUM> is lowered to the lowered position with reference to base body <NUM>. Accordingly, the sum of the amount corresponding to the maximum load weight of transported object <NUM> and the own weight of vehicle body <NUM> acts on four traveling wheels <NUM> to be the ground contact load. In consideration of a manufacturing error of the stress generated in four elastic bodies <NUM>, an error of unevenness of road surface RD, or the like, control section <NUM> may reduce the lifting amount by an amount corresponding to the error. Accordingly, it is possible to avoid a concern that a load exceeding the maximum load weight acts on loading platform portion <NUM>.

(<NUM>) In a case where the total weight of transported object <NUM> exceeds the maximum load weight but an excess amount is equal to or less than a predetermined reducible weight, control section <NUM> adds the above-described separation distance and a reduction stroke length obtained by multiplying lowering stroke length DS by a first reduction rate less than <NUM> to obtain a lifting amount. In this case, in a case where common base <NUM> is lifted, support body <NUM> stops in the middle of being lowered, instead of being lowered to the lowered position with reference to base body <NUM>. Accordingly, the sum of the amount corresponding to the partial weight of transported object <NUM> and the own weight of vehicle body <NUM> acts on four traveling wheels <NUM> to be the ground contact load. That is, in a case where an excess amount is not so large, it is not necessary to apply the maximum load weight from transported object <NUM> to traveling wheels <NUM>, and a certain degree of reduction is allowed. Accordingly, for example, by setting the first reduction rate to <NUM>%, a partial weight that is half the maximum load weight is applied from transported object <NUM> to traveling wheels <NUM> via loading platform portion <NUM>, thereby obtaining a sufficient ground contact load.

(<NUM>) In a case where the total weight of transported object <NUM> is equal to or less than the maximum load weight, control section <NUM> adds the above-described separation distance and a stroke length obtained by multiplying lowering stroke length DS by a second reduction rate to obtain a lifting amount. The second reduction rate is set within a range in which transported object <NUM> is not elevated from road surface RD. For example, in a case where the total weight of transported object <NUM> is <NUM>% of the maximum load weight, the second reduction rate is set to a range of <NUM>% or more and less than <NUM>% (refer to Hooke's law). In a case where the second reduction rate is <NUM>%, transported object <NUM> is self-standing while bearing the total weight of transported object <NUM> and is pressed by pressing portion <NUM>. Further, in a case where the second reduction rate approaches <NUM>%, elastic body <NUM> is compressed by that amount, and most of the total weight of transported object <NUM> acts on traveling wheels <NUM> via loading platform portion <NUM>.

In next step S3, autonomous transport vehicle <NUM> travels toward the current position of transported object <NUM> indicated by current position information P1. Step S3 can be executed in parallel with step S2. In step S4 during traveling, acquisition section <NUM> acquires the individual identification information of transported object <NUM> while approaching transported object <NUM> and sends the individual identification information to control section <NUM>. In next step S5, control section <NUM> checks whether the individual identification information received from acquisition section <NUM> matches individual identification information ID included in transported object data DC received from transported object management section <NUM>.

In a case where two pieces of individual identification information ID do not match, and in a case where acquisition section <NUM> cannot acquire the individual identification information from transported object <NUM>, the execution of the operation flow branches to step S12. In step S12, control section <NUM> notifies transported object management section <NUM> that commanded transported object <NUM> is absent (not found), and ends the operation flow.

In step S6, in a case where two pieces of individual identification information ID match, loading platform portion <NUM> and weight acting portion <NUM> of autonomous transport vehicle <NUM> enter the lower side of transported object <NUM>. In next step S7, weight acting portion <NUM> operates based on any one of the determination patterns (<NUM>) to (<NUM>) described above. In any one of the determination patterns, elastic support portion <NUM> and connecting member <NUM> is lifted. Accordingly, support body <NUM> supports bottom plate <NUM> of transported object <NUM>, and elastic body <NUM> is compressed and deformed. Further, pressing portion <NUM> is lifted to a height at which pressing portion <NUM> can come in to contact with contacted portion <NUM> from the lateral side. Accordingly, transported object <NUM> is loaded on loading platform portion <NUM> and can be towed by loading platform portion <NUM>.

In next step S8, control section <NUM> drives traveling wheels <NUM>. Accordingly, autonomous transport vehicle <NUM> loads transported object <NUM> and travels to the target position indicated by target position information P2. Autonomous transport vehicle <NUM> travels to the target position while towing transported object <NUM> while pressing portion <NUM> presses contacted portion <NUM>.

Here, in a case where the total weight of transported object <NUM> exceeds the maximum load weight, the maximum load weight or the partial weight of the total weight of transported object <NUM> acts on loading platform portion <NUM> because of the action of elastic support portion <NUM>. According to this, the sum of the maximum load weight or partial weight of transported object <NUM> and the own weight of vehicle body <NUM> acts on four traveling wheels <NUM> to be the ground contact load. Accordingly, a stable ground contact load of traveling wheels <NUM> can be secured, and autonomous transport vehicle <NUM> can transport transported object <NUM> while towing transported object <NUM>. Further, even in a case where road surface RD of the traveling road has some unevenness or steps, autonomous transport vehicle <NUM> can transport transported object <NUM> while towing transported object <NUM>.

Further, since the stable ground contact load is secured, traveling wheels <NUM> is less likely to slip (idle). Accordingly, the estimation accuracy of the current position estimated from the driving amount of traveling wheels <NUM> does not decrease.

In next step S9, weight acting portion <NUM> performs a releasing operation. That is, drive section <NUM> cause common base <NUM> to perform a lowering operation to generate a separation distance between support body <NUM> and bottom plate <NUM> of transported object <NUM>. In next step S10, loading platform portion <NUM> and weight acting portion <NUM> exit from the lower side of transported object <NUM>. Accordingly, autonomous transport vehicle <NUM> leaves transported object <NUM> at the target position and departs from transported object <NUM>. In next step S11, control section <NUM> notifies transported object management section <NUM> that the commanded transportation has ended. Transported object management section <NUM> moves the content of target position information P2 to current position information P1 and makes target position information P2 blank. As a result, the operation flow corresponding to one transportation command is ended.

In autonomous transport vehicle <NUM> of the embodiment, loading platform portion <NUM> of vehicle body <NUM> is caused to enter the lower side of transported object <NUM>, and the partial weight of transported object <NUM> is applied from transported object <NUM> to loading platform portion <NUM>, so that a large load obtained by adding the partial weight of transported object <NUM> to the own weight of vehicle body <NUM> acts as the ground contact load of traveling wheels <NUM>. Accordingly, even in a case where the total weight of transported object <NUM> is different on a case-by-case basis, it is possible to secure the stable ground contact load of traveling wheels <NUM> to suppress a slip (idling), and it is possible to transport transported object <NUM> while towing transported object <NUM>.

The predetermined weight can be set to be smaller than the maximum load weight. For example, the spring constant of elastic body <NUM> is made smaller than that of the embodiment. According to this, it is possible to reliably avoid a concern that the load exceeding the maximum load weight acts on loading platform portion <NUM>. Further, pressing portion <NUM> can be formed long and provided to directly stand upon common base <NUM>. In this aspect, moment generated in pressing portion <NUM> is larger than that in the embodiment, and thus pressing portion <NUM> needs to be thickened, but connecting member <NUM> can be omitted. Further, a combination of pressing portion <NUM> and contacted portion <NUM> can be replaced with another configuration capable of moving transported object <NUM> in the horizontal direction. For example, an engaging portion provided on a front surface of driving portion <NUM> may be engaged with an engaged portion provided on a rear surface of transported object <NUM>, and vehicle body <NUM> and transported object <NUM> may move together.

Further, it is not essential to estimate the current position based on the driving amount of traveling wheels <NUM>, and control section <NUM> may obtain the current position only by detecting the position marker by the sensor and determine the future traveling route. Further, the data format of transported object data DC can be changed in various ways. For example, one item of information, the total weight of transported object <NUM>, can be used instead of two items of information, package weight information W2 and own weight information W1. Further, the total weight of transported object <NUM> on which a package is placed may be measured, and a measured value of the total weight may be used as transported object data DC. Further, information indicating the height dimension of transported object <NUM> may be used instead of loading possibility information YN of transported object data DC. In this aspect, control section <NUM> determines whether loading is possible by comparing the height dimension of transported object <NUM> with a predetermined limit height dimension at which loading is possible. Various modifications and applications in addition to the embodiment are possible as long as they fall within the scope of the attached claims.

Claim 1:
An autonomous transport vehicle (<NUM>) comprising:
a vehicle body (<NUM>), that includes a traveling wheel (<NUM>), is configured to enter a lower side of a transported object (<NUM>), and is configured to travel while towing the transported object (<NUM>); and
a weight acting portion (<NUM>) configured to cause, in a case where a total weight of the transported object (<NUM>) is larger than a predetermined weight, a partial weight of the total weight equal to or less than the predetermined weight to act on the vehicle body (<NUM>) from the transported object (<NUM>),
wherein the weight acting portion (<NUM>) includes
an elastic support portion (<NUM>) that is provided on the vehicle body (<NUM>) so as to be capable of being lifted and lowered, and is configured to support the transported object (<NUM>) from the lower side via an elastic body (<NUM>),
wherein the elastic support portion (<NUM>) includes
a base body (<NUM>) that is provided on the vehicle body (<NUM>) so as to be capable of being lifted and lowered,
a support body (<NUM>) that is provided on the base body (<NUM>) so as to be capable of being lifted and lowered, and is configured to support the transported object (<NUM>) from the lower side, and
the elastic body (<NUM>) that is provided between the base body (<NUM>) and the support body (<NUM>) and in which the stress equal to the predetermined weight is generated in a case where the support body (<NUM>) is lowered to a predetermined lowered position with reference to the base body (<NUM>),
characterized in that
the weight acting portion (<NUM>) further includes
a drive section (<NUM>) configured to lift the elastic support portion (<NUM>) with respect to the vehicle body (<NUM>) such that a stress generated in the elastic body (<NUM>) becomes the partial weight, the drive section (<NUM>) driving the base body (<NUM>) to be lifted and lowered.