Patent Publication Number: US-9405292-B2

Title: Delivery vehicle and method and program for controlling drive of delivery vehicle

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a delivery vehicle that is moved by driving a servomotor, and a method and program to control driving of a delivery vehicle. 
     2. Description of the Related Art 
     There have been known vehicle control systems that automatically deliver goods using delivery vehicles, for example, in a factory or warehouse. In such a system, each delivery vehicle is driven by a servomechanism including a servomotor. The servomechanism includes a controller, a servo amplifier, and a servomotor. The servo amplifier drives the servomotor by supplying, to the servomotor, a drive current corresponding to the difference between the command position from the controller and the current position from a position detector in the servomotor. Japanese Unexamined Patent Application Publication No. 2000-99151 discloses, as such a system, a configuration in which the gain for feedback control varies with the weight of a loaded article. 
     When unexpected disturbance or the like occurs, the servomechanism may abruptly change the drive of the servomotor so that the current position follows the command position. However, such a transient movement for following the command position cannot be controlled by the controller. For this reason, the current position may significantly deviate from the command position due to the unexpected disturbance or the like, failing to follow the command position. Further, the servomechanism may raise the output torque in order to follow the command position, thereby increasing power consumption. Furthermore, such an excessive movement may impair safety. While the system of Japanese Unexamined Patent Application Publication No. 2000-99151 described above performs feedback control using an appropriate gain corresponding to the weight of a loaded article, the system does not have any means for avoiding the current position from excessively deviating from the command position. 
     SUMMARY OF THE INVENTION 
     Preferred embodiments of the present invention provide a delivery vehicle that prevents a current position from deviating from a command position due to unexpected disturbance or the like, and a method and program to control driving of a delivery vehicle. 
     According to a preferred embodiment of the present invention, a delivery vehicle includes a command position generator that generates a command position to move the delivery vehicle to a target position by driving a servomotor, an acceptable value calculator that calculates a predetermined acceptable value based on a current position, an acceptable value determiner that determines whether the command position exceeds the predetermined acceptable value calculated by the acceptable value calculator, and a command position changer that changes the command position when the acceptable value determiner determines that the command position exceeds the predetermined acceptable value. 
     The delivery vehicle may further include a position detector configured to detect the current position, and the acceptable value calculator may calculate the predetermined acceptable value based on the current position outputted from the position detector. Further, the command position changer may change the command position to the predetermined acceptable value or a predetermined position within a range which does not exceed the predetermined acceptable value. Further, the command position generator may generate the command position in predetermined cycles, and the acceptable value calculator may acquire the current position in synchronization with generation of the command position. Further, preferably, the predetermined acceptable value is set to include the amount of movement during one of the predetermined cycles. Further, the command position changer may change the command position at the timing when the command position generator generates the command position. 
     Another preferred embodiment of the present invention provides a method to control driving of a delivery vehicle. The method includes generating a command position to move the delivery vehicle to a target position by driving a servomotor, calculating a predetermined acceptable value based on a current position; determining whether the command position exceeds the predetermined acceptable value, and changing the command position when it is determined that the command position exceeds the predetermined acceptable value. 
     A further preferred embodiment of the present invention provides a non-transitory computer-readable medium including a computer program that controls driving of a delivery vehicle. The program causes the delivery vehicle to perform a command position generation process of generating a command position to move the delivery vehicle to a target position by driving a servomotor, an acceptable value calculation process of calculating a predetermined acceptable value based on a current position, an acceptable value determination process of determining whether the command position exceeds the predetermined acceptable value calculated in the acceptable value calculation process, and a command position change process of changing the command position when it is determined in the acceptable value determination process that the command position exceeds the predetermined acceptable value. 
     According to various preferred embodiments of the present invention, a predetermined acceptable value is calculated based on the current position; it is determined whether the command position exceeds the predetermined acceptable value; when it is determined that the command position exceeds the predetermined acceptable value, the command position is changed. Thus, it is possible to prevent the current position from deviating from the command position due to unexpected disturbance or the like. As a result, the following are prevented: a significant deviation of the current position from the command position and thus a failure to follow the command position; raising of the output torque to follow the command position and thus an increase in power consumption; and impairment of safety due to an excessive movement. 
     Further, if the delivery vehicle includes a position detector configured to detect the current position and the acceptable value calculator calculates the predetermined acceptable value based on the current position outputted from the position detector, it is possible to calculate an acceptable value based on the correct current position. Further, if the command position changer changes the command position to the predetermined acceptable value or to a predetermined position within a range which does not exceed the predetermined acceptable value, it is possible to set the command position to an acceptable value corresponding to the configuration or use configuration of the servomechanism, or the like. Further, if the command position generator generates the command position in predetermined cycles and the acceptable value calculator acquires the current position in synchronization with the generation of the command position, it is possible to calculate an acceptable value based on a position close to the actual current position. Further, if the predetermined acceptable value is set to include the amount of movement during one of the predetermined cycles, it is possible to set an accurate acceptable value. Further, if the command position changer changes the command position at the timing when the command position generator generates the command position, it is possible to prevent a delay in changing the command position and to control the drive of the servomotor based on the changed command position. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system configuration diagram of a delivery vehicle control system according to an example preferred embodiment of the present invention. 
         FIG. 2  is a schematic diagram showing the configuration in one feeding area, of the vehicle control system shown in  FIG. 1 . 
         FIG. 3  is a block diagram showing the configuration of a vehicle controller shown in  FIG. 1 . 
         FIGS. 4A and 4B  are diagrams showing command information or status report information exchanged between the vehicle controller and delivery vehicles, in which  FIG. 4A  is a diagram showing command information; and  FIG. 4B  is a diagram showing status report information. 
         FIGS. 5A and 5B  includes diagrams showing the modes or statuses of a delivery vehicle. 
         FIG. 6  is a block diagram showing the configuration of a delivery vehicle shown in  FIG. 1 . 
         FIG. 7  is a flowchart showing an example of a power control process performed by the vehicle controller. 
         FIG. 8  is a block diagram showing the configurations of a traveling controller and a servo system. 
         FIG. 9  is a flowchart showing an example of a power limitation process performed by the traveling controller. 
         FIG. 10  is a waveform diagram showing the relationships among the power consumption, speed, torque, and torque limit value of a servomotor. 
         FIG. 11  is a flowchart showing an example of a command value setting process performed by the traveling controller. 
         FIG. 12  is a diagram showing waveforms of the unchanged command position, current position, and changed command position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereafter, preferred embodiments of the present invention will be described with reference to the drawings. 
       FIG. 1  is a system configuration diagram a vehicle control system according to an example preferred embodiment of the present invention. As shown in  FIG. 1 , a vehicle control system  1  is a system in which multiple delivery vehicles  50  perform predetermined operations based on operation commands transmitted from a vehicle controller (controller)  10 . The vehicle control system  1  includes at least multiple zone controllers  30  installed on the ground and the multiple delivery vehicles  50 . If the area in which the delivery vehicles  50  are able to move is divided into multiple areas, the divided areas are provided with zone controllers  30 A and  30 B, respectively, in the vehicle control system  1 . 
     In the example shown in  FIG. 1 , the vehicle controller  10  is connected to another server S and a personal computer P through a local area network (LAN). The vehicle controller  10  is also connected to the two zone controllers,  30 A and  30 B, through the LAN, as well as to a server S 1  and a personal computer P 1  through the LAN. The zone controller  30 A is connected to multiple access points  41 A to  44 A (represented by “AP” in  FIG. 1 ) through the LAN, and the zone controller  30 B is connected to multiple access points  41 B to  44 B (represented by “AP” in  FIG. 1 ) through the LAN. The access points  41 A to  44 A and  41 B to  44 B communicate with the multiple delivery vehicles  50  through a wireless LAN, for example. 
     The vehicle controller  10  is a computer server that centrally controls the vehicle control system  1 . Specifically, when the vehicle controller  10  receives a request to deliver a predetermined article from the other server S, personal computer P, or the like, the vehicle controller  10  transmits, to one of the delivery vehicles  50 , delivery instruction information corresponding to the delivery request and instructing the delivery vehicle  50  to deliver the predetermined article. For example, the delivery instruction includes information on which delivery vehicle  50  being used to deliver the predetermined article, the position in which the predetermined article is to be loaded, the position in which the predetermined article is to be unloaded, and the route of the delivery vehicle  50  (movement path). At this time, the vehicle controller  10  properly determines a route that bypasses the concentration or congestion of the delivery vehicles  50  while avoiding the delivery vehicle  50  from being interfered with the other delivery vehicles  50 . 
     As shown in  FIG. 1 , the area in which the delivery vehicles  50  are able to move is divided into multiple areas. The multiple areas are feeding areas  20 A and  20 B, and are provided with the zone controllers  30 A and  30 B, respectively. The feeding areas  20 A and  20 B are each assigned the amount of power corresponding to the size of the area, the workloads of the delivery vehicles  50  in the area, and the like. The amount of power assigned to each of the feeding areas  20 A and  20 B serves as the main amount of power of the feeding area. The respective main amounts of power are determined by the vehicle controller  10 . For example, the vehicle controller  10  assigns the main amount of power of 3500 W to the feeding area  20 A and the main amount of power of 4000 W to the feeding area  20 B. 
     In causing a delivery vehicle  50  in one feeding area (e.g., feeding area  20 B) to enter other feeding area (e.g., feeding area  20 A), the vehicle controller  10  transmits area entry information to the zone controller  30  in the feeding area which the delivery vehicle  50  is to enter. The area entry information includes information identifying the delivery vehicle  50  which is to enter the feeding area  20 A (e.g., vehicle number information) and information indicating the operating status (status) of the delivery vehicle  50 . 
     The zone controllers  30 A and  30 B perform collision prevention control (blocking control) of the delivery vehicles  50  in the feeding area  20 A and  20 B, respectively. As shown in  FIG. 1 , the zone controller  30 A is installed on the ground in the feeding area  20 A. The zone controller  30 A performs blocking control of the delivery vehicles  50  in the feeding area  20 A by wirelessly communicating with the delivery vehicles  50  in the feeding area  20 A through the access points  41 A to  44 A. The zone controller  30 B is installed on the ground in the feeding area  20 B. The zone controller  30 B performs blocking control of the delivery vehicles  50  in the feeding area  20 B by wirelessly communicating with the delivery vehicles  50  in the feeding area  20 B through the access points  41 B to  44 B. Note that there may be used a configuration in which the zone controllers  30 A and  30 B are omitted and the vehicle controller  10  performs blocking control. 
     The delivery vehicles  50  are, for example, ceiling traveling vehicles, which travel along rails installed on the ceiling. However, the delivery vehicles  50  are not limited to ceiling traveling vehicles and may be, for example, delivery vehicles which do not include one or both of lifting and transfer apparatuses, stacker cranes, or the like. 
     If the area in which the delivery vehicles  50  are able to move is not divided into multiple areas (that is, if there is only one feeding area), one zone controller  30  may perform control such as the reception of a delivery request, the determination of a task corresponding to the delivery request, and the determination of the route of the delivery vehicle  50 , or there may be used a configuration in which the zone controller  30  is omitted and the vehicle controller  10  performs control of the vehicles, including blocking control. Further, even if the area in which the delivery vehicles  50  are able to move is divided into multiple feeding areas,  20 A and  20 B, the zone controllers  30  may perform some or all functions of the vehicle controller  10 . Further, the area in which the delivery vehicles  50  are able to move may be divided into three or more feeding areas, for example. In this case, a zone controller may be installed in each feeding area. 
       FIG. 2  is a schematic diagram showing the configuration in one feeding area, of the vehicle control system shown in  FIG. 1 . Specifically,  FIG. 2  shows the configuration in the feeding area  20 A thereof. In  FIG. 2 , the zone controller  30 A and access points  41 A to  44 A are omitted, and four delivery vehicles  50 A to  50 D are able to enter the feeding area  20 A. 
     As shown in  FIG. 2 , a rail (track)  60  on which the delivery vehicles  50 A to  50 D travel is installed along the load ports of multiple production facilities or the like in the feeding area  20 A. The rail  60  is connected to a rail installed in the other feeding area,  20 B. 
     In the example shown in  FIG. 2 , the delivery vehicle  50 A is automatically circulating (traveling); the delivery vehicle  50 B is automatically traveling to an unloading position; the delivery vehicle  50 C is automatically transferring (loading) an article; and the delivery vehicle  50 D is jogging manually (based on an operation of a manual controller  70  such as a remote control by the operator). 
     In the present preferred embodiment, the vehicle controller  10  determines the maximum amounts of power consumption to be assigned to each delivery vehicles  50 A to  50 D corresponding to the operating statuses of the delivery vehicles  50 A to  50 D within the main amount of power that is supplied to the feeding area  20 A. The maximum amounts of power consumption are the amounts of power available (consumable) to the delivery vehicles  50 A to  50 D, respectively, in the main amount of power assigned to the feeding area  20 A. 
     In the example shown in  FIG. 2 , the delivery vehicle  50 A, which is automatically circulating, is assigned the amount of power of 1000 W as the maximum amount of power consumption; the delivery vehicle  50 B, which is automatically traveling to the unloading position, is assigned the amount of power of 1300 W as the maximum amount of power consumption; the delivery vehicle  50 C, which is automatically transferring the article, is assigned the amount of power of 700 W as the maximum amount of power consumption; and the delivery vehicle  50 D, which is manually jogging, is assigned the amount of power of 500 W as the maximum amount of power consumption. The delivery vehicles  50 A to  50 D perform operations such as traveling within the assigned maximum amounts of power consumption, respectively. 
     Although the configuration in the feeding area  20 B is not shown in  FIG. 2 , it is the same as that in the feeding area  20 A except for the number of delivery vehicles, the position of the rail, and the like. For this reason, repeated description is omitted. 
       FIG. 3  is a block diagram showing the configuration of the vehicle controller shown in  FIG. 1 .  FIGS. 4A and 4B  are diagrams showing command information or status report information exchanged between the vehicle controller and the delivery vehicles, in which  FIG. 4A  is a diagram showing command information; and  FIG. 4B  is a diagram showing status report information. The elements shown in  FIG. 3  are implemented when an arithmetic device such as a central processor (CPU) performs processing in accordance with a program stored in the memory. 
     As shown in  FIG. 3 , the vehicle controller  10  includes an inter-vehicle distance controller  31 , a power controller  32 , and a communicator  33 . The inter-vehicle distance controller  31  is a processor that commands the operations of the delivery vehicles  50 A to  50 D in the feeding area  20 A and/or inter-vehicle distances of the delivery vehicles  50 A to  50 B. Specifically, the inter-vehicle distance controller  31  recognizes the operations of the delivery vehicles  50 A to  50 D in the feeding area  20 A and the routes of the delivery vehicles  50 A to  50 D based on delivery command information. The inter-vehicle distance controller  31  also recognizes the current positions of the delivery vehicles  50 A to  50 D on the routes in the feeding area  20 A and the current distances between these delivery vehicles based on status report information transmitted from these delivery vehicles  50 A to  50 D as seen in  FIG. 4B . The inter-vehicle distance controller  31  then outputs, to the communicator  33 , command information commanding the delivery vehicles  50 A to  50 D in the feeding area  20 A to perform operations or keep inter-vehicle distances as seen in  FIG. 4A . 
     The command information outputted from the inter-vehicle distance controller  31  preferably includes vehicle number information identifying a delivery vehicle (“vehicle No.” in  FIG. 4A ), operation command information commanding the delivery vehicle to perform an operation (e.g., traveling, loading, or the like) (“operation command” in  FIG. 4A ), and inter-vehicle distance control command information commanding the delivery vehicle to control inter-vehicle distances (“inter-vehicle distance control command” in  FIG. 4A ). The inter-vehicle distance control command information includes “system clock (millisecond),” “block (starting point No.)” identifying the target position, “unit (distance from starting point),” “speed (mm/s),” and “attribute.” 
     The information, for which the inter-vehicle distance controller  31  recognize the current positions of the delivery vehicles  50 A to  50 D and the current inter-vehicle distances, are vehicle number information identifying a vehicle (e.g., “1 to 1500”), current position information (“current position” in  FIG. 4B ) including “block (starting point No.)” identifying the current position of the delivery vehicle and “unit (distance from starting point),” and inter-vehicle distance information consisting of “point No. on route” “distance to point” and “time required to reach point” among the status report information shown in  FIG. 4B . 
     The power controller  32  is a processor that manages the number of the delivery vehicles  50  in the feeding area  20 A and determines the maximum amounts of power consumption assigned to the respective delivery vehicles  50  in the feeding area  20 A. As shown in  FIG. 3 , the power controller  32  includes a vehicles number controller  32 A and a power amount assigner  32 B. The vehicles number controller  32 A determines whether to permit delivery vehicles  50  to enter the feeding area  20 A and also determines the number of delivery vehicles  50  that perform operations such as traveling in the feeding area  20 A. The power amount assigner  32 B determines the maximum amounts of power consumption corresponding to the number of delivery vehicles  50  in the feeding area  20 A determined by the vehicles number controller  32 A and the current operating statuses (statuses) of delivery vehicles  50 , and assigns the determined maximum amounts of power consumption to the respective delivery vehicles  50 . 
     Specifically, the power controller  32  recognizes the main amount of power that is able to be supplied to the feeding area  20 A, based on feeding area information and suppliable power information. The power controller  32  also recognizes the current statuses (statuses) of the delivery vehicles  50 A to  50 D in the feeding area  20 A based on the status report information, shown in  FIG. 4B , transmitted from the delivery vehicles  50 A to  50 D. The power controller  32  also recognizes whether there are any delivery vehicles which are newly entering the feeding area  20 A, based on the area entry information. 
     More specifically, the information, for which the power controller  32  recognizes the operating status of each of the delivery vehicles  50 A to  50 D, are vehicle number information identifying the delivery vehicle (e.g., “1 to 1500”) and status information (“operation information”) indicating the operating status of the delivery vehicle among the status report information shown in  FIG. 4B . 
     The vehicles number controller  32 A of the power controller  32  determines the number of the delivery vehicles in the feeding area  20 A based on the main amount of power, the statuses of the delivery vehicles  50  (if there are any newly entering delivery vehicles, the statuses of those delivery vehicles), the number of the delivery vehicles  50  in the feeding area  20 A, and information indicating whether there are any delivery vehicles entering the feeding area  20 A. The power amount assigner  32 B of the power controller  32  determines the maximum amounts of power consumption assigned to the respective delivery vehicles  50  within the main amount of power based on the number of delivery vehicles  50  in the feeding area  20 A determined by the vehicles number controller  32 A and the current operating statuses (statuses) of the delivery vehicles  50 . The power amount assigner  32 B of the power controller  32  then outputs power amount information indicating each determined maximum amount of power consumption to the communicator  33 . 
     The power amount information indicating the maximum amount of power consumption outputted from the power controller  32  is “power limit value” in the command information shown in  FIG. 4A . 
     The communicator  33  is a processor that transmits or receives information to or from the delivery vehicles  50 A to  50 D in communication cycles of, for example, 100 ms. Specifically, the communicator  33  sets, in a transmission buffer, command information outputted from the inter-vehicle distance controller  31  and commanding each delivery vehicle to perform an operation or keep inter-vehicle distances, that is, the vehicle number information, operation command information, and inter-vehicle distance control information in the command information shown in  FIG. 4A . The communicator  33  also sets, in the transmission buffer, the power amount information outputted from the power controller  32  (“power limit value” in the command information shown in  FIG. 4A ). The communicator  33  then transmits the buffered command information to the delivery vehicles  50 A to  50 D in synchronization with in communication cycles of 100 ms. 
     As shown in  FIG. 3 , the delivery vehicles  50 A to  50 D each include an operation information transmitter  51  that transmits operation information to the vehicle controller  10 , a power amount information receiver  52  that receives power amount information transmitted from the vehicle controller  10 , and an operation controller  53  that performs an operation within the amount of power assigned by the power amount assigner  32 B. 
     Next, specific examples of the status (operating status) will be described.  FIGS. 5A and 5B  are diagrams showing the modes and statuses of a delivery vehicle. In the present preferred embodiment, as shown in  FIG. 5A , a delivery vehicle  50  has three modes: “manual,” “automatic,” and “semi-automatic.” “Manual” is a mode in which the operator causes the delivery vehicle  50  to jog by using a remote control (manual controller  70 ) near the delivery vehicle  50 . “Automatic” is a mode in which the delivery vehicle  50  automatically moves based on a command from the vehicle controller  10 . “Semi-automatic” is a mode in which the operator automatically moves the delivery vehicle  50  using the vehicle controller  10  or remote control. 
     Further, in the present preferred embodiment, as shown in  FIG. 5B , the delivery vehicle  50  preferably has eight statuses, for example: “abnormal/warning,” “unstarted,” “idle,” “traveling for loading,” “traveling for unloading,” “traveling,” “loading,” and “unloading.” “Abnormal/warning” is a status in which an abnormality is occurring and a warning is needed. “Unstarted” is a status in which the delivery vehicle  50  is yet to be started. “Idle” is a status in which the delivery vehicle  50  is at rest but can perform an operation upon receipt of a command from the vehicle controller  10 . “Traveling for loading” is a status in which the delivery vehicle  50  is traveling to the position in which it loads goods (articles). “Traveling for unloading” is a status in which the delivery vehicle  50  is traveling to the position in which it unloads goods. “Traveling” is a status in which the delivery vehicle  50  is traveling for a purpose other than the transfer of goods, such as dispatch, push-out, or circulation. “Loading” is a status in which the delivery vehicle  50  is raising the lifting apparatus thereof after lowering it and causing a gripper to grasp goods, for example, on the load port of a production facility below the rail. “Unloading” is a status in which the delivery vehicle  50  is raising the lifting apparatus after lowering it and placing goods grasped by the gripper, for example, on the load port of a production facility below the rail. 
     The status “abnormal/warning” has manual, automatic, and semi-automatic modes. The statuses other than “abnormal/warning” have automatic and semi-automatic modes. For example, the status “traveling” includes “traveling automatically,” whose mode is automatic, and “traveling semi-automatically,” whose mode is semi-automatic. Similarly, the status “loading” includes “loading automatically,” whose mode is automatic and “loading semi-automatically,” whose mode is semi-automatic. The same applies to the other statuses. 
     While the delivery vehicle  50  preferably has the multiple statuses (operating statuses) as described above, the required amount of power varies among the statuses. For this reason, in the present preferred embodiment, the power controller  32  of the vehicle controller  10  assigns the delivery vehicles  50  the main amount of power which is able to be supplied to the feeding areas  20 A and  20 B with optimal allocation corresponding to the operating statuses of the delivery vehicles  50 . The respective delivery vehicles  50  perform operations requested by commands within the assigned maximum amounts of power consumption. 
       FIG. 6  is a block diagram showing the configuration of a delivery vehicle shown in  FIG. 1 . It is assumed that the delivery vehicle  50  shown in  FIG. 6  is a delivery vehicle in the feeding area  20 A (e.g., one of the delivery vehicles  50 A to  50 D shown in  FIG. 2 ). Further, in the present preferred embodiment, it is assumed that the delivery vehicles  50  preferably have the same configuration. As shown in  FIG. 6 , the delivery vehicle  50  includes a communicator  100 , a traveling controller  110 , a raise/lower controller  130 , a transfer controller  150 , servo systems  120 ,  140 , and  160 , a power supply controller  170 , and a power receiving coil  171 . 
     The traveling controller  110 , raise/lower controller  130 , and transfer controller  150  constitute the operation controller  53  shown in  FIG. 3 . The communicator  100 , operation controller  53  (traveling controller  110 , raise/lower controller  130 , and transfer controller  150 ), and servo systems  120 ,  140 , and  160  constitute a servomechanism. 
     The communicator  100  is a processor that receives command information from the vehicle controller  10  and transmits status report information to the vehicle controller  10 . The communicator  100  transmits or receives information to or from the vehicle controller  10  in communication cycles of, for example, 100 ms. The communicator  100  serves as the operation information transmitter  51  and power amount information receiver  52  shown in  FIG. 3 . 
     The traveling controller  110  controls the traveling of the delivery vehicle  50  by transmitting a command to the servo system  120  to drive a servomotor (see  FIG. 8 ) in the servo system  120 . The traveling controller  110  also transmits status report information (status information, current position information, inter-vehicle distance information) corresponding to the current operating status of the delivery vehicle  50  through the communicator  100 . 
     The raise/lower controller  130  controls the raising or lowering of a platform (not shown) mounted on the delivery vehicle  50  by transmitting a command to the servo system  140  to drive a servomotor (not shown) in the servo system  140 . The raise/lower controller  130  also transmits status report information (mainly, status information) corresponding to the current operating status of the platform through the communicator  100 . 
     The transfer controller  150  causes a gripper (not shown) mounted on the platform of the delivery vehicle  50  to grip or release goods by transmitting a command to the servo system  160  to drive a servomotor (not shown) in the servo system  160 . The transfer controller  150  also transmits status report information (mainly, status information) corresponding to the current operating status of the transfer apparatus through the communicator  100 . 
     The power supply controller  170  and power receiving coil  171  constitute a non-contact power receiving apparatus of the delivery vehicle  50 . A guide wire (also called a feeder line) installed along the rail  60  (see  FIG. 2 ) and a feeder panel that converts commercial power into power having a predetermined frequency suitable for non-contact power supply and transmits the power to the guide wire constitute a non-contact power supply apparatus  70  shown in  FIG. 6 . When the feeder panel transmits the power having the predetermined frequency to the guide wire, a magnetic field occurs around the guide wire. The power receiving coil  171  is disposed in a position opposite to the guide wire in the delivery vehicle  50  and receives the power through the magnetic field generated by the guide wire. The power supply controller  170  stabilizes the power received by the power receiving coil  171  and supplies the resulting power to the servo systems  120 ,  140 , and  160 . 
     While the vehicle controller  10  and delivery vehicles  50  are able to communicate with each other as described above, the delivery vehicles  50  are also able to communicate with one another. 
     Next, the operation of the vehicle control system  1  according to various preferred embodiments of the present invention will be described. 
       FIG. 7  is a flowchart showing an example of a power control process performed by the vehicle controller. In the description of  FIG. 7 , it is assumed that the vehicle controller  10  performs a power control process. In the power control process shown in  FIG. 7 , the power controller  32  of the vehicle controller  10  acquires suppliable power information and feeding area information. The power controller  32  also receives status report information transmitted from all the delivery vehicles,  50 A to  50 D, in the feeding area  20 A through the communicator  33 . The power controller  32  also acquires area entry information. In this way, the power controller  32  acquires the suppliable power information, feeding area information, status report information, and area entry information (step S 1 ). 
     The power controller  32  then recognizes the main amount of power that is able to be supplied to the feeding area  20 A, based on the suppliable power information and feeding area information. The power controller  32  also recognizes the statuses (operating statuses) and number of the delivery vehicles  50 A to  50 D based on the status report information. The power controller  32  also recognizes whether there are any delivery vehicles which are newly entering the feeding area  20 A, based on the area entry information. 
     Next, the vehicles number controller  32 A of the power controller  32  determines the number of the delivery vehicles in the feeding area  20 A based on the recognized main amount of power, the statuses of the delivery vehicles  50 A to  50 D (if there are any newly entering delivery vehicles, the statuses of those delivery vehicles), the number of the delivery vehicles  50 A to  50 D, and information indicating whether there are any delivery vehicles entering the feeding area  20 A (step S 2 ). 
     Specifically, the vehicles number controller  32 A of the power controller  32  determines the number of delivery vehicles in the feeding area  20 A using the following method. That is, the vehicles number controller  32 A determines whether there are any delivery vehicles which are newly entering the feeding area  20 A, based on the area entry information; if the vehicles number controller  32 A determines that there are no newly entering delivery vehicles, it grasps the number of the delivery vehicles  50 A to  50 D currently present in the feeding area  20 A (four in the example shown in  FIG. 2 ) as the number of delivery vehicles; and if the vehicles number controller  32 A determines that there are any newly entering delivery vehicles, it adds the number of the delivery vehicles newly entering the feeding area  20 A to the number of the delivery vehicles  50 A to  50 D currently present in the feeding area  20 A and grasps the resulting number as the number of delivery vehicles. The vehicles number controller  32 A then checks the statuses (operating statuses) of all the delivery vehicles grasped as the number of delivery vehicles. The vehicles number controller  32 A also checks the minimum guarantee amounts of power corresponding to the statuses of all the delivery vehicles. As used herein, the minimum guarantee amount of power refers to the minimum amount of power which the delivery vehicle requires to perform an operation corresponding to the status thereof and which should be guaranteed. 
     The vehicles number controller  32 A then determines whether a total minimum guarantee amount of power obtained by summing up the minimum guarantee amounts of power corresponding to the statuses of all the delivery vehicles exceeds the main amount of power that can be supplied to the feeding area  20 A. If the total minimum guarantee amount of power does not exceed the main amount of power, the vehicles number controller  32 A permits the new delivery vehicles to enter the feeding area  20 A. In contrast, if the total minimum guarantee amount of power exceeds the main amount of power, the vehicles number controller  32 A refuses (restricts) the entry of the new delivery vehicles into the feeding area  20 A. 
     If the vehicles number controller  32 A of the power controller  32  refuses the entry of those delivery vehicles into the feeding area  20 A in step S 2 , it outputs the result. The vehicle controller  10  receives the result and places those delivery vehicles on standby or performs a process such as the change of the route. 
     Subsequently, based on the number and statuses of the delivery vehicles determined in step S 2 , the power amount assigner  32 B of the power controller  32  determines the power limit values (maximum amounts of power consumption) of the delivery vehicles (step S 3 ). Specifically, the power amount assigner  32 B determines standard amounts of power corresponding to the statuses of all the delivery vehicles determined in step S 2  as the power limit values of those delivery vehicles. As used herein, the standard amount of power refers to a sufficient amount of power to perform an operation corresponding to the status. 
     The power amount assigner  32 B then determines whether a total standard amount of power obtained by summing up the standard amounts of power corresponding to the statuses of all the delivery vehicles exceeds the main amount of power that is able to be supplied to the feeding area  20 A. If the total standard amount of power exceeds the main amount of power, the power amount assigner  32 B sets power limit values to all the delivery vehicles in such a manner that the sum of the power limit values of all the delivery vehicles falls within the main amount of power and in such a manner that the power limit value of at least one of all the delivery vehicles does not fall below the corresponding minimum guarantee amount of power, based on predetermined priorities assigned to the statuses. Higher priorities are assigned to more important statuses in order to efficiently perform delivery tasks corresponding to delivery requests. For example, the power amount assigner  32 B sets, to a delivery vehicle whose status has the highest priority, the standard amount of power thereof as the power limit value and sets, to a delivery vehicle whose status has a low priority, the amount of power which is smaller than the corresponding standard amount of power but does not fall below the corresponding minimum guarantee amount of power as the power limit value. 
     Subsequently, the power controller  32  outputs the power limit values of the delivery vehicles determined in step S 3  to the communicator  33 . The communicator  33  sets the power limit values in transmission buffers corresponding to the respective delivery vehicles (step S 4 ). The communicator  33  then transmits command information including the power limit value information to the delivery vehicles in synchronization with the communication cycles. 
     In step S 3  described above, if the sum of the standard amounts of power exceeds the main amount of power, the power controller  32  sets power limit values to all the delivery vehicles based on the predetermined priorities assigned to the statuses, but it is not limited such a configuration. For example, the power controller  32  may set power limit values to all the delivery vehicles so that the sum of the power limit values of all the delivery vehicles falls within the main amount of power, by uniformly reducing, from the respective standard amounts of power of all the delivery vehicles, the amount of power obtained by dividing, by the number of all the delivery vehicles, the amount of power by which the sum of the standard amounts of power exceeds the main amount of power. 
     The power control by the vehicle controller  10  described with reference to  FIG. 7  produces the following advantageous effects. That is, the power controller  32  assigns, to the delivery vehicles  50 , available amounts of power corresponding to the statuses (operating statuses) thereof within the main amount of power, and the delivery vehicles  50  perform predetermined operations within the respective assigned amounts of power. That is, the power controller  32  assigns, to the delivery vehicles  50 , the amounts of power most suitable for the statuses thereof within the main amount of power available to the system. Thus, it is possible to increase the number of delivery vehicles  50  that are able to be driven and thus to improve delivery efficiency. Further, since the main amount of power that is able to be supplied to the vehicle control system  1  is used efficiently, the main amount of power is significantly reduced. 
     Further, since each delivery vehicle  50  transmits status information about the current operation thereof to the vehicle controller  10  in predetermined cycles, the vehicle controller  10  is able to change the amount of power assigned to the delivery vehicle  50  in accordance with the operation thereof when necessary. Thus, a robust system is provided. Further, in the case that the power controller  32  assigns the amounts of power to the delivery vehicles  50  based on the priorities of the operations of the delivery vehicles  50 , the power controller  32  is able to assign a sufficient amount of power to a delivery vehicle  50  which is performing an important operation in a delivery task. As a result, a reduction in the efficiency of the delivery task is avoided. Further, in the case that the power controller  32  assigns to each delivery vehicle  50 , the amount of power that does not fall below the corresponding minimum guarantee amount of power, which allows the delivery vehicle  50  to perform a predetermined operation, the power controller  32  prevents the delivery vehicles  50  from lacking power. 
     Further, if the area in which the delivery vehicles  50  are able to move is divided into multiple feeding areas,  20 A and  20 B, and if the system includes a vehicle controller  10  that assigns the suitable main amounts of power to the feeding areas  20 A and  20 B, it is possible to improve the power efficiency of the entire system, which is divided into the multiple areas,  20 A and  20 B. Further, when a delivery vehicle from one of the feeding areas  20 A and  20 B enters the other feeding area, if the amount of power assigned by the power controller  32 , of at least one of the delivery vehicles  50  in the other feeding area falls below the corresponding guaranteed minimum amount, which allows the delivery vehicle  50  to perform a predetermined operation, the vehicle controller  10  restricts the entry of the delivery vehicle into the other feeding area. As a result of the configuration described above, it is possible to reliably drive the delivery vehicles  50  in the feeding areas managed by the vehicle controller. 
       FIG. 8  is a block diagram showing the configurations of the traveling controller and servo system. The elements shown in  FIG. 8  are implemented when an arithmetic device such as a CPU performs processing in accordance with a program stored in the memory. 
     The traveling controller  110  includes a command generator  111 , a torque limit value calculator  112 , and an acceptable value calculator  113 . The command generator  111  includes a command position generator  111   a , an acceptable value determiner  111   b , and a command position changer  111   c . The command position generator  111   a  of the command generator  111  receives command information transmitted from the vehicle controller  10  through the communicator  100 . Then, based on operation command information and inter-vehicle distance control command information included in the command information, the command position generator  111   a  generates an operation waveform to cause the delivery vehicle  50  to perform an operation (traveling) indicated by the operation command information at a position and speed indicated by the inter-vehicle distance control command information. 
     The command position generator  111   a  of the command generator  111  then generates a command position (the amount of rotation, rotation angle) of a servomotor  122  of the servo system  120  based on the generated operation waveform. The command position generator  111   a  then outputs the generated command position to a servo amplifier  121  of the servo system  120 , as well as to the acceptable value calculator  113 . The command position here is a pulse signal. The position (the amount of rotation, rotation angle) of the servomotor  122  with respect to one pulse is predetermined. The pulse frequency serves as the speed (the number of revolutions, rotation speed) of the servomotor  122 . 
     The acceptable value determiner  111   b  of the command generator  111  determines whether to change the position commanded to the servo amplifier  121  by the command position signal (hereafter referred to as the command position), based on a command acceptable value (to be discussed later) outputted from the acceptable value calculator  113 . In the present preferred embodiment, if the acceptable value determiner  111   b  determines that the command position generated by the command position generator  111   a  based on the operation waveform (the command position generated based on the command information from the vehicle controller  10 ) exceeds the command acceptable value, it determines that the command position is to be changed to the command acceptable value. When the acceptable value determiner  111   b  determines that the command position to be changed, the command position changer  111   c  of the command generator  111  changes the command position to the command acceptable value and outputs the changed command position to the servo amplifier  121  of the servo system  120 . 
     The torque limit value calculator  112  receives the power limit value (power amount information) included in the command information transmitted from the vehicle controller  10 . The torque limit value calculator  112  also receives the current speed of the servomotor  122  fed back from the servo amplifier  121  (hereafter referred to as the “FB speed”). The torque limit value calculator  112  then calculates a torque limit value to limit the maximum torque of the servomotor  122  based on the FB speed from the servomotor  122  and the power limit value (maximum power consumption) indicated by the power amount information and outputs the calculated torque limit value to the servo amplifier  121 . 
     The acceptable value calculator  113  receives the current position of the servomotor  122  fed back from a position detector  122 A disposed in the servomotor  122  (hereafter referred to as the “FB position”). Then, based on the FB position, the acceptable value calculator  113  calculates a command acceptable value, which is acceptable as a command position that the FB position should follow. The acceptable value calculator  113  then outputs the calculated command acceptable value to the command generator  111 . 
     The servo system  120  includes the servo amplifier (drive controller)  121  and servomotor  122 . The servo amplifier  121  calculates a deviation (difference) of the FB position (pulse signal) outputted by the position detector  122 A of the servomotor  122  from the command position outputted by the command generator  111  using a deviation counter. The servo amplifier  121  then controls the drive of the servomotor  122  by supplying a drive current corresponding to the deviation calculated using the deviation counter to the servomotor  122 . At this time, the servo amplifier  121  controls the drive current to drive the servomotor  122  so that the torque of the servomotor  122  does not exceed the torque limit value outputted from the torque limit value calculator  112 . The servo amplifier  121  also converts the FB position outputted from the position detector  122 A into a FB speed and outputs the FB speed to the torque limit value calculator  112 . 
     The servomotor  122  is a motor that is driven (rotationally driven) based on the drive current supplied from the servo amplifier  121 . The servomotor  122  includes the position detector  122 A, which detects the position (the amount of rotation) of the servomotor  122 . The position detector  122 A consists of, for example, an encoder. However, the position detector  122 A is not limited to an encoder and may be a position sensor such as a laser range finder or magnetic linear sensor. The position detector  122 A outputs the FB position indicating the detected current position of the servomotor  122  to the servo amplifier  121  and the acceptable value calculator  113 . 
     The traveling controller  110  or command generator  111  includes a processor that outputs the current operating status (status) to the communicator  100 . This also applies to the raise/lower controller  130  and transfer controller  150 . The operation information transmitter  51  of the communicator  100  transmits status report information including operation information to the vehicle controller  10  based on the operating statuses outputted from the traveling controller  110 , raise/lower controller  130 , and transfer controller  150 . 
     The delivery vehicles  50  must perform operations such as traveling within the respective maximum amounts of power consumption (power limit values) assigned by the vehicle controller  10 . Hereafter, a configuration to limit the torque of the servomotor based on the power limit value will be described. 
       FIG. 9  is a flowchart showing an example of a power limitation process performed by the traveling controller. The power limitation process shown in  FIG. 9  is repeatedly performed in the same cycles as those in which the traveling controller  110  and servo amplifier  121  communicate with each other (e.g., 0.888 ms or 0.444 ms). As shown in  FIG. 9 , the torque limit value calculator  112  of the traveling controller  110  receives the power limit value included in the command information transmitted from the vehicle controller  10 . The torque limit value calculator  112  also receives the feedback speed from the servo amplifier  121 . The torque limit value calculator  112  also acquires various parameters preset to the servo system  120 . The various parameters include the efficiency of the traveling driver (servo system  120  and the like) and standby power. 
     The torque limit value calculator  112  then calculates a torque limit value τ to limit the maximum torque of the servomotor  122 , for example, based on the following formula in which the FB speed of the servomotor  122  and the power limit value (maximum power consumption) indicated by the power limit value information serve as variables (step S 12 ).
 
τ≦( P −α)/((1/η)*(2*π/60)*ω)
 
     In this formula, P represents the maximum power consumption (i.e., power limit value) (W); η represents the efficiency of the traveling driver; ω represents the revolutions per minute (rpm) of the servomotor  122 =FB speed (0.01 rpm)/100; τ represents the motor torque (Nm) of the servomotor  122 =(FB torque (0.1%)/10)*1.3 (Nm)/100; and α represents standby power (W). 
     The torque limit value calculator  112  then outputs (transmits) the calculated torque limit value to the servo amplifier  121  (step S 13 ). The communication cycles between the traveling controller  110  and servo amplifier  121  are, for example, 0.888 ms (0.444 ms in some cases). Specifically, the torque limit value calculator  112  sets the torque limit value calculated in step S 12  in a buffer, and transmits the torque limit value set in the buffer to the servo amplifier  121  at the timing synchronous with the communication cycles. 
       FIG. 10  is a waveform diagram showing the relationships among the power consumption, speed, torque, and torque limit value of the servomotor. In  FIG. 10 , the vertical axis represents the amount of power (W), and the horizontal axis represents the time (s). Also, A 1  represents the FB speed (0.1 rpm), A 2  represents the maximum amount of power consumption (power limit value) (0.1 W), A 3  represents the torque limit value (0.1%), A 4  represents the feedback torque (the current torque of the servomotor  122 ; “FB torque” in  FIG. 10 ) (0.1%), and A 5  represents the amount of power consumption (0.1 W) of the servomotor  122 . As shown in  FIG. 10 , the maximum amount of power consumption (power limit value) (0.1 W) is set to 1300 W. 
     The torque limit value calculator  112  calculates a torque limit value A 3  based on the FB speed A 1  and the maximum amount of power consumption A 2 . As shown in  FIG. 10 , the servo amplifier  121  controls the FB torque A 4  of the servomotor  122  to a value lower than the torque limit value A 3  by controlling the drive current to drive the servomotor  122 . Thus, the amount of power consumption A 5  of the servomotor  122  is controlled to an amount smaller than or equal to the maximum amount of power consumption A 2  by controlling the FB torque A 4  of the servomotor  122  to the value lower than the torque limit value A 3 . 
     The torque limitation configuration described using  FIGS. 9 and 10  produces the following advantageous effects. That is, since the torque limit value calculator  112  calculates the torque limit value of the servomotor  122  based on the rotation speed of the servomotor  122  and the amount of power consumable by the servo motor  122  and since the servo amplifier  121  drives the servomotor  122  to the extent that the torque of the servomotor  122  does not exceed the torque limit value, it is possible to limit the torque even when disturbance or the like occurs and thus to reduce power consumption. Further, the margin of power consumption in preparation for disturbance or the like is significantly reduced. 
     Further, by acquiring the rotation speed of the servomotor  122  in predetermined cycles and calculating a torque limit value in the predetermined cycles based on the acquired rotation speed and the amount of power, the torque limit value calculator  112  calculates a torque limit value corresponding to the rotation speed of the servomotor  122  at any time. Further, if the torque limit value calculator  112  receives power amount information transmitted from the vehicle controller  10  and calculates a torque limit value using the received power amount information, the vehicle controller  10  is able to easily change the power consumable by the servo system. Further, if the vehicle controller  10  transmits power amount information to each of the multiple servo systems, it is possible to efficiently use the main amount of power that is available to be supplied to the vehicle control system  1  and thus to reduce the main amount of power. 
     The servo system  120  controls the drive of the servomotor  122  using a speed and torque corresponding to the distance between the command position and FB position. However, in the present preferred embodiment, the amount of power available to each delivery vehicle  50  is limited to the corresponding power limit value and therefore the torque of the servomotor  122  of the vehicle is controlled to a torque limit value corresponding to the power limit value. Thus, the FB position may fail to follow the command position and deviate therefrom. The FB position may also deviate from the command position due to disturbance. Further, when the FB position excessively deviates from the command position, the servo system  120  may fail to follow the command position, causing a servo error, or may perform an abnormal operation such as abrupt acceleration to follow the command position. For this reason, in the present preferred embodiment, when the FB position deviates from the command position by a predetermined distance or more, the command position is changed in accordance with the FB position. Thus, an excessive deviation of the FB position from the command position is prevented. Hereafter, a configuration to change the command position as described above will be described. 
       FIG. 11  is a flowchart showing an example of a command value setting process performed by the traveling controller. The command value setting process shown in  FIG. 9  is repeatedly performed in the same cycles as those in which the traveling controller  110  and servo amplifier  121  communicate with each other (e.g., 0.888 ms or 0.444 ms). As shown in  FIG. 11 , the command position generator  111   a  of the command generator  111  in the traveling controller  110  determines whether the command value setting process is complete (step S 21 ). If the command position generator  111   a  determines that the command value setting process is not complete, it determines whether an operation waveform has been generated (step S 22 ). If the command position generator  111   a  determines that an operation waveform has been generated, the process proceeds to step S 25 . In contrast, if the command position generator  111   a  determines that any operation waveform has not been generated, it generates an operation waveform (step S 23 ). The command position generator  111   a  then generates a command position commanding the position (the amount of rotation) of the servomotor  122  of the servo system  120  based on the generated operation waveform (step S 24 ). 
     The acceptable value calculator  113  receives the FB position from the position detector  122 A in synchronization with the timing when the command position generator  111   a  of the command generator  111  generates the command position. The acceptable value calculator  113  then calculates a command acceptable value using the following formula based on the received FB position (step S 25 ). The acceptable value calculator  113  then outputs the calculated command acceptable value to the command generator  111 .
 
Upper limit of command acceptable value= FB  position+time integral of command speed+(command speed/position gain)+tolerance (mm)
 
Lower limit of command acceptable value= FB  position+time integral of command speed+(command speed/position gain)−tolerance (mm)
 
     In these formulas, the FB position is the current position as described above; and “time integral of command speed” represents the amount (distance) that the delivery vehicle travels at a command speed in a command position signal outputted at this time. Note that the acceptable value calculator  113  is able to recognize the command speed based on the frequency of the command position outputted from the command generator  111 . “Speed command/position gain” represents the amount (distance) corresponding to a delay caused by the position gain. In these formulas, it is assumed that the tolerance is the amount of movement (distance) corresponding to one rotation of the motor. 
     Since the command value setting process shown in  FIG. 11  is performed in the same cycles as the communication cycles, the command generator  111  generates a command position in the same cycles as the communication cycles, and the acceptable value calculator  113  acquires the FB position in synchronization with the generation of the command position. Thus, the acceptable value calculator  113  is able to calculate a command acceptable value based on the FB position, which is close to the actual current position. Further, since the command acceptable value is set to include the amount of movement of the delivery vehicle  50  during one communication cycle, it is possible to set an accurate command acceptable value. 
     The acceptable value determiner  111   b  of the command generator  111  determines whether the command position generated based on the operation waveform exceeds the command acceptable value (step S 26 ). If the acceptable value determiner  111   b  determines that the command position does not exceed the command acceptable value, the command position changer  111   c  of the command generator  111  outputs (transmits) the command position generated based on the operation waveform to the servo amplifier  121  without changing the command position (step S 27 ). In contrast, if the acceptable value determiner  111   b  determines that the command position exceeds the command acceptable value, the command position changer  111   c  of the command generator  111  changes the command position generated based on the operation waveform to the command acceptable value. As seen above, since the command generator  111  is able to change the command position to the command acceptable value at the timing when the command position is generated, it is possible to prevent a delay in changing the command position and to control the drive of the servomotor  122  based on the changed command position. The command generator  111  then outputs (transmits) the command position representing the command acceptable value (“the command acceptable value” in  FIG. 11 ) to the servo amplifier  121  (step S 28 ). 
     As described above, the traveling controller  110  and servo amplifier  121  communicate with each other in cycles of 0.888 ms, for example. Accordingly, in the transmission processes of steps S 27  and S 28 , the command generator  111  sets the command position signal in the buffer and transmits the command position signal set in the buffer to the servo amplifier  121  at the timing synchronous with the communication cycles. 
       FIG. 12  is a diagram showing waveforms of the unchanged command position, the current position, and the changed command position. In  FIG. 12 , the vertical axis represents the distance from a predetermined position (mm), and the horizontal axis represents the time (s). B 1  represents the command position generated based on an operation waveform; B 2  represents the FB position; and B 3  represents the command position changed by the command generator  111 , that is, the command acceptable value. 
     As shown in  FIG. 12 , at time t 1 , that is, immediately after the servomotor  122  starts to operate at a predetermined speed, the FB position B 2  has yet to deviate from the command position B 1 . However, from time t 2  onward, the FB position B 2  gradually deviates from the command position B 1  due to the limitation of the torque based on the torque limit value, disturbance, or the like. At time t 3 , the command position B 1  becomes the command acceptable value B 3  or more. At this time, the command generator  111  changes the command position B 1  to the command acceptable value B 3  and outputs the changed command position to the servo amplifier  121 . Thus, a deviation of the FB position B 2  from the command position (command acceptable value B 3 ) by a predetermined distance or more is prevented. At time t 4 , the servomotor  122  is driven at an increased speed owing to the relaxation of the power limit value or the disappearance of disturbance and thus the FB position B 2  comes close to the command position B 1 . Subsequently, at time t 5 , the servomotor  122  comes to a stop, and the FB position B 2  reaches the command position B 1 . 
     While the limitation of the torque and the change of the command position performed by the traveling controller  110  and servo system  120  have been described with reference to  FIGS. 8 to 12 , the raise/lower controller  130  and servo system  140 , or the transfer controller  150  and servo system  160  may perform the limitation of the torque and the change of the command position in a similar manner. 
     Specifically, the raise/lower controller  130  may also include the same or approximately the same elements as the command generator  111 , the torque limit value calculator  112 , and the acceptable value calculator  113  of the traveling controller  110  and perform the processes shown in  FIGS. 9 and 11 . More specifically, the torque limit value calculator of the raise/lower controller  130  calculates a torque limit value based on the power amount information and the FB speed from the servo amplifier; the servo amplifier limits the torque of the servomotor within the torque limited by the torque limit value calculated by the torque limit value calculator and drives the lifting apparatus; the acceptable value calculator of the raise/lower controller  130  calculates a command acceptable value based on the FB position outputted from the position detector; the acceptable value determiner of the command generator determines whether the command position exceeds the command acceptable value; and if the acceptable value determiner determines that the command position exceeds the command acceptable value, the command position changer of the command generator changes the command position to the command acceptable value. 
     The transfer controller  150  may also include the same or approximately the same elements as the command generator  111 , the torque limit value calculator  112 , and the acceptable value calculator  113  of the traveling controller  110  and perform the processes shown in  FIGS. 9 and 11 . More specifically, the torque limit value calculator of the transfer controller  150  calculates a torque limit value based on the power amount information and the FB speed from the servo amplifier; the servo amplifier limits the torque of the servomotor within the torque limited by the torque limit value calculated by the torque limit value calculator and drives the transfer apparatus; the acceptable value calculator of the transfer controller  150  calculates a command acceptable value based on the FB position outputted from the position detector; the acceptable value determiner of the command generator determines whether the command position exceeds the command acceptable value; and if the acceptable value determiner determines that the command position exceeds the command acceptable value, the command position changer of the command generator changes the command position to the command acceptable value. 
     As described above, in the present preferred embodiment, the acceptable value calculator  113  calculates a command acceptable value based on the current position of the delivery vehicle  50 ; the acceptable value determiner  111   b  of the command generator  111  determines whether the command position exceeds the command acceptable value; and if the command position is determined to exceed the command acceptable value, the command position changer  111   c  of the command generator  111  changes the command position. Thus, it is possible to prevent the current position from deviating from the command position due to unexpected disturbance, the limitation of the amount of power, or the like. As a result, the following are prevented: a significant deviation of the current position from the command position and thus a failure to follow the command position; the raising of the output torque to follow the command position and thus an increase in power consumption; and the impairment of safety due to an excessive movement. 
     Further, if the delivery vehicle  50  includes a position detector  122 A that detects the current position thereof and the acceptable value calculator  113  calculates a command acceptable value based on the current position outputted from the position detector  122 A, it is possible to calculate a command acceptable value based on the correct current position. Further, if the command position changer  111   c  of the command generator  111  changes the command position to the command acceptable value or a predetermined position within a range which does not exceed the command acceptable value, it is possible to set the command position to a command acceptable value corresponding to the form or the use form of the servo system. Further, if the command position generator  111   a  of the command generator  111  generates a command position in predetermined cycles and if the acceptable value calculator  113  acquires the current position in synchronization with the generation of the command position, it is possible to calculate a command acceptable value based on the position information, which is close to the actual current position. Further, if the command acceptable value is set to include the amount of movement of the delivery vehicle  50  during one cycle of process cycles same as the communication cycles, it is possible to set an accurate command acceptable value. Further, if the command position changer  111   a  changes the command position at the timing when the command position generator  111   a  generates the command position, it is possible to prevent a delay in changing the command position and to control the drive of the servomotor  122  based on the changed command position. 
     While preferred embodiments of the present invention have been described, the present invention is not limited to the elements and the like shown in the drawings. Changes can be made to the elements and the like without departing from the functions, purposes, and the like thereof. While the area in which the delivery vehicles  50  are able to move is preferably divided into the two feeding areas,  20 A and  20 B, in the above embodiment, the area may be divided into three or more feeding areas, for example. 
     While the respective feeding areas preferably correspond to the same system in the above preferred embodiments, the feeding areas may correspond to different systems. For example, one feeding area may correspond to a system using a stacker crane, and the other feeding area may correspond to a system using a ceiling traveling vehicle or the like, which differs from a stacker crane. 
     While, in the above preferred embodiments, the feeding areas are areas in which there are installed production facilities and the like for which delivery vehicles  50  actually perform delivery tasks, there may be an area in which multiple delivery vehicles  50  are placed on standby (standby area). In this case, the delivery vehicles  50  are dispatched from this standby area to a feeding area. Since the delivery vehicles  50  in this standby area need power to perform operations such as traveling, the standby area is also assigned the main amount of power. 
     The following configuration may also be used: video or images of the operating statuses of the delivery vehicles  50  is captured using an imaging device such as a video camera; the operating statuses of the delivery vehicles  50  are analyzed based on the video or images using a method such as pattern matching; and the vehicle controller  10  acquires the analysis results as operation information. 
     While the torque limit value calculator  112  is included in the traveling controller  110  in the above preferred embodiments of the present invention, it may be included in the servo amplifier  121 . 
     While the command position is changed to the command acceptable value in the above preferred embodiments of the present invention, the command position may be changed to a position which prevents the servo system  120  from failing to follow the command position and thus causing a servo error or prevents the servo system  120  from performing an abnormal operation such as abrupt acceleration to follow the command position. Accordingly, the command position may be changed to a predetermined position within a range which does not exceed the command acceptable value. 
     While, in the above preferred embodiments, the upper and lower limits of the command acceptable value preferably are calculated using the formulas: upper limit of command acceptable value=FB position+time integral of command speed+(command speed/position gain)+tolerance (mm), and lower limit of command acceptable value=FB position+time integral of command speed+(command speed/position gain)−tolerance (mm). However, such a calculation is merely one non-limiting example, the command acceptable value may be calculated as a position which prevents the servo system  120  from failing to follow the command position and thus causing a servo error or prevents the servo system  120  from performing an abnormal operation such as abrupt acceleration to follow the command position. 
     While it is assumed in the above preferred embodiments that the non-contact feeding system preferably is an electromagnetic induction-type system, the system may be an electromagnetic resonance-type system, which uses a resonance phenomenon of an electromagnetic field. The system may also be a contact-type feeding system using a trolley or the like. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.