Abstract:
A factory line system includes a series of robot arms arranged alongside a conveyor on which workpieces are transported. Each workpiece is fitted with a data carrier and each robot arm is fitted with a reader/writer that can wirelessly communicate with the data carrier of each workpiece when the latter is in transit between the conveyor and a work station. Specifically, when a first robot arm detects a workpiece, it removes the workpiece from the conveyor to a first work station that performs work on the workpiece and sends result data through the reader/writer of the robot arm to the data carrier and replaces the workpiece from the first work station to the conveyor. When the workpiece is transported, approaching a second robot arm, the latter reads the result data through its reader/writer from the data carrier. According to the result data, the second work station performs work on the workpiece.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based on Japanese Patent Application No. 2004-316424, filed Oct. 29, 2004, which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a robot-controlled factory line system that performs a specified work on each material or product item transported on a conveyer system.  
         [0004]     2. Description of the Related Art  
         [0005]     In a factory line system where a series of work stations are provided alongside a belt conveyer, each work station includes a robot arm that picks up a product item from the conveyor, performs a specified work on it and then returns it the conveyer. In a known factory line system, pallets are provided on the conveyer to carry the materials to be worked on and a data carrier on which data are recorded to instruct the robot arm of each work station. As disclosed in Japanese Patent Publication 06-210556, each pallet on the conveyor system is provided with a data carrier which is constructed of a coil to be inductively coupled with a reader/writer of each work station. The reader/write is also constructed of a coil and fixed in a predetermined position of the work station. The first work station is additionally provided with a video camera that senses the position of the workpiece on each pallet and writes its position data through its reader/writer into the data carrier of the same pallet of the sensed workpiece. Each of subsequent workstations on the downstream side of the first station determines the position of each approaching workpiece by establishing inductive coupling between its reader/writer and the data carrier of the pallet carrying the workpiece. Since the reader/writer of each work station is stationary with respect to the approaching data carrier, the time to keep read data from it is limited. If it is desired to increase the time interval for reading a large volume of data, the conveyor system needs to be stopped whenever each pallet comes to each work station and the cycle time of the system will increase with a resultant low productivity. To reduce the cycle time, the robot arm must be moved at high speeds. However, this requires the robot arm to be driven at high power, constructed of rigid structure and provided with a high-power hand for holding the workpiece. In addition, the robot arm would experience increased acceleration at the start of each stroke and increased deceleration at the end of the stroke, which is likely to cause a damage on a workpiece of relatively soft material by increased arm&#39;s holding power. Furthermore, a braking device must be provided to stop or decelerate.  
       SUMMARY OF THE INVENTION  
       [0006]     It is therefore an object of the present invention to provide a factory line system for robot-arm work stations that permit communication to be established with data carriers for a sufficient time interval for data read/write operations.  
         [0007]     The object of the invention is obtained by attaching the data carrier to each workpiece that is carried on the conveyer system and mounting a communication device on the robot arm for wirelessly establishing communication between the data carrier and the communication device when the workpiece is being moved between the conveyor system and a work station.  
         [0008]     In general terms, the present invention provides a factory line system comprising a conveyor system that carries a workpiece, a data carrier on the workpiece, a robot arm provided on one side of the conveyor system for handling the workpiece, a communication device attached to the robot arm to wirelessly communicate with the data carrier. Control circuitry is associated with the robot arm and the communication device. The control circuitry control circuitry, associated with the robot arm and the communication device, that operates the robot arm to hold the workpiece and causes the communication device to communicate with the data carrier while the robot arm is proximate to the workpiece.  
         [0009]     According to a specific aspect, the present invention provides a factory line system comprising a conveyor system that carries a workpiece, a data carrier, on the workpiece, that stores type-of-work information, a robot arm provided on one side of the conveyor system for handling the workpiece, a reader, attached to the robot arm, that wirelessly communicates with the data carrier when the robot arm is proximate to the workpiece, and control circuitry, associated with the robot arm and the reader, that operates the robot arm to remove the workpiece from the conveyor system, causes the reader to read the type-of-work information from the data carrier while the robot arm is proximate to the workpiece, and operates the robot arm to perform work on the workpiece according to the read type-of-work information.  
         [0010]     The factory line system further comprises a further robot arm provided on one side of the conveyor system for handling the workpiece, a reader, attached to the robot arm, that wirelessly communicates with the data carrier, and control circuitry, associated with the further robot arm and the reader, that operates the further robot arm to remove the workpiece from the conveyor system, causes the reader to read the response signal from the data carrier while the robot arm is proximate to the workpiece, and operates the further robot arm to perform work on the workpiece according to the read response signal.  
         [0011]     According to a further aspect, the present invention provides a method of operating a factory line system including a conveyor system and a robot arm provided on one side of the conveyor system, comprising the steps of (a) providing a workpiece on the conveyor system, (b) attaching a data carrier to the workpiece, (c) attaching a communication device to the robot arm, the communication device being capable of wirelessly communicating with the data carrier when the robot arm is proximate to the workpiece, and (d) operating the robot arm to hold the workpiece and causing the communication device to communicate with the data carrier while the robot arm is proximate to the workpiece.  
         [0012]     According to a further aspect, the present invention provides a factory line system including a robot arm provided in the neighborhood of a conveyor system on which workpieces of different types of work to be performed are transported, the robot arm having a holder fitted to a forward end of the robot arm for holding one of the workpieces and removing the one workpiece from the conveyor system. The factory line system comprises a data carrier, attached to each of the workpieces, that stores information indicating the type of work of the workpiece, tracking control means that controls the robot arm so that the forward end of the robot arm keeps track of the, movement of the one workpiece on the conveyor system, reading means, attached to the forward end of the robot arm, that wirelessly communicates with the data carrier to read the type-of-work information of the one workpiece stored in the data carrier, and work control means that determines work to be performed according to the information read by the reading means and controls the robot arm according the determined work. The reading means performs reading of the stored information from the one workpiece during a time interval that runs from the instant the forward end of the robot arm approaches the one workpiece while the same is being transported on the conveyor system and then kept track of by the forward end to the instant the one workpiece is removed from the conveyor system.  
         [0013]     According to a still further aspect, the present invention provides a factory line system including a robot arm provided in the neighborhood of a conveyor system on which a workpiece is transported, the robot arm having a holder fitted to a forward end of the robot arm for holding the workpiece and removing the one workpiece from the conveyor system to a work station and replacing the workpiece to the conveyor system after work is performed by the work station on the workpiece. The factory line system comprises a data carrier, attached to the workpiece, into which information is written and from which the stored information is read out, tracking control means that controls the robot arm so that the forward end of the robot arm keeps track of the movement of the conveyor system, ommunication means that receives work result information from the work station, the information indicating a result of the work performed by the work station on the workpiece, and writing means, attached to the forward end of the robot arm, that writes the work result information of the workpiece into the data carrier. The writing means performs writing of the work result information into the data carrier during a time interval that runs from the instant the forward end of the robot arm approaches the workpiece on the work station and then keeps track of the movement of the conveyor system to the instant the workpiece is replaced to the conveyor system.  
         [0014]     According to a still further aspect, the present invention provides a factory line system comprising a conveyor system on which a workpiece is transported, a first robot arm having a holder fitted to a forward end of the first robot arm for holding the workpiece and removing the one workpiece from the conveyor system to a work station and replacing the workpiece to the conveyor system after work is performed by the work station on the workpiece, a second robot arm having a holder fitted to a forward end of the second robot arm for holding the workpiece and removing the one workpiece from the conveyor system to perform work, a data carrier, attached to the workpiece, into which information is written and from which the stored information is read out, first tracking control means that controls the first robot arm so that the forward end of the first robot arm keeps track of the movement of the conveyor system, communication means that receives work result information from the work station, the information indicating a result of the work performed by the work station on the workpiece, and writing means, attached to the forward end of the first robot arm, that writes the work result information of the workpiece into the data carrier, second tracking control means that controls the second robot arm so that the forward end of the second robot arm keeps track of the movement of the workpiece on the conveyor system, reading means, attached to the forward end of the robot arm, that wirelessly communicates with the data carrier to read the type-of-work information of the one workpiece stored in the data carrier, and work control means that determines work to be performed according to the information read by the reading means and controls the second robot arm according the determined work. The writing means performs writing of the work result information into the data carrier during a time interval that runs from the instant the forward end of the first robot arm approaches the workpiece on the work station and then keeps track of the movement of the conveyor system to the instant the workpiece is replaced to the conveyor system. The holder of the second robot arm holds the workpiece while the forward end of the second robot arm is tracking the movement of the workpiece on the conveyor system. The reading means performs reading of the stored information from the one workpiece during a time interval that runs from the instant the forward end of the second robot arm approaches the one workpiece while the same is being transported on the conveyor system and then kept track of by the forward end of the second robot arm to the instant the one workpiece is removed from the conveyor system. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The present invention will be described in detail with reference to the following drawings, in which:  
         [0016]      FIG. 1  is a top-plan view of a factory line system according to the present invention;  
         [0017]      FIG. 2  is a perspective view of a first work station (inspecting station) of the line system of  FIG. 1 ;  
         [0018]      FIG. 3  is a perspective view of a second work station (sorting station) of the line system of  FIG. 1 ;  
         [0019]      FIG. 4  is a block diagram of the first work station;  
         [0020]      FIG. 5  is a block diagram of the second work station;  
         [0021]      FIG. 6  is a flowchart of the operation of the first work station;  
         [0022]      FIG. 7  is a flowchart of the operation of the second work station; and  
         [0023]      FIG. 8  is a timing diagram of the operation of the second work station. 
     
    
     DETAILED DESCRIPTION  
       [0024]     In  FIG. 1 , there is shown a factory line system according to a first embodiment of the present invention. The factory line system comprises a belt conveyor system  1  and a plurality of work stations located alongside the conveyor system  1 . A plurality of pallets  3  are provided at spaced intervals on the conveyor belt  11  which is transported in a direction A. Product items, or workpieces  2  are shown carried on respective pallets  3 . For simplicity, only two work stations ST 1  and ST 2  are shown. Although not shown, one or more work stations located on the upstream side of the work station ST 1  are dedicated to perform specified work on each workpiece, such as drilling, for example. Work station ST 1  is an inspecting station that includes an inspection unit  4  and a robot arm  5 . Inspection unit  4  determines the quality of work performed by the upstream work stations by measuring the flow of compressed air directed into each workpiece picked up from the conveyor belt  11  by the robot arm  5 . The inspected workpieces are returned to the conveyor belt  11  by the robot arm  5  and transported to the work station ST 2 .  
         [0025]     Work station ST 2  is a sorting station that includes a nondefective-product bin  6 , a defective-product bin  7  and a robot arm  8 . Robot arm  8  picks up the inspected workpieces from the conveyor system and sorts them into the bin  6  or  7  according to their determined quality.  
         [0026]     Inspecting station ST 1  is provided with an optical sensor  9  as a proximity sensor that detects when each workpiece has approached a predetermined distance to the pick-up position of robot arm  5  and issues a start timing signal to the robot arm  5  to initiate a pick-up motion. Further provided is a rotary encoder  12  that generates a pulse at a rate corresponding to the moving speed of conveyor belt  11 . By counting pulses from the rotary encoder  12 , the inspecting station ST 1  determines a displacement each workpiece or pallet has traveled upstream from the position of the conveyor belt where it is detected by the optical sensor  9 . In the same way, the sorting station ST 2  is provided with an optical sensor  10  to detect when each inspected workpiece has approached a predetermined distance to the pick-up position of robot arm  8  and supplies it with a start timing signal. A rotary encoder  13  generates a pulse at a rate corresponding to the moving speed of conveyor belt  11 . Sorting station ST 2  counts pulses from the rotary encoder  13  to determine a displacement each object has traveled from the position it is detected by the optical sensor  10 .  
         [0027]     As clearly shown in  FIGS. 2 and 3 , the workpiece  2  is provided with a wireless data carrier  14 , or an IC chip card containing a memory for storing the test data of a workpiece which is obtained at the inspecting station ST 1  and then read by the sorting station ST 2  for operating its robot arm  8 . The IC chip card  14  includes control circuitry and a wireless interface consisting of a digital modem and a coil antenna for receiving test data from the wireless reader/writer  17  and storing it in the memory and then sending the stored test data to the reader/writer  18 . Data carrier  14  is further provided with an RDID (Read Identification) tag, not shown.  
         [0028]     Robot arm  5  of the inspecting station ST 1  has at its lower end a workpiece holding hand, or holder  15  and a wireless reader/writer  17  ( FIG. 2 ). Likewise, the robot arm  8  of the sorting station ST 2  has at its lower end a workpiece holder  16  and a wireless reader/writer  18  ( FIG. 3 ). Each wireless reader/writer is used to communicate with the wireless data carrier  14 .  
         [0029]     As shown in detail in  FIG. 4 , the inspecting station ST 1  includes a robot-arm controller  23  to which the inspection unit  4 , robot arm  5 , optical sensor  9 , rotary encoder  12 , a wireless reader/writer  17  and a teach pendant  25  are connected. Inspection unit  4  includes a sender  27  that encodes a digital signal indicating the result of inspection on a workpiece with a predetermined line code to protect the data from electromagnetic interference and sends it to a line receiver  28  provided in the robot-arm controller  23 . Teach pendant  25  is used to teach the robot-arm controller  23  about specified locations of the robot arm  5 .  
         [0030]     Wireless reader/writer  17  is activated by the robot-arm controller  23  for an interval when a data carrier is brought close to it. Reader/writer  17  includes a read/write head  19  and a read/write controller  21  that receives the test result data of inspection unit  4  from the robot-arm controller  23  when the reader/writer  17  is rendered active and supplies the read/write head  19  with the test result data. Read/write, head  19  includes a coil antenna and a digital modem that digitally modulates the test result data onto a radio-frequency carrier for transmission to the data carrier  14 .  
         [0031]     As shown in detail in  FIG. 5 , the sorting station ST 2  includes a robot-arm controller  24  to which the robot arm  8 , optical sensor  10 , rotary encoder  13 , wireless reader/writer  18  and a teach pendant  26  are connected. Teach pendant  26  is used to teach the robot-arm controller  24  about specified locations of the robot arm  8 .  
         [0032]     Wireless reader/writer  18  is activated by the robot-arm controller  24  for an interval when a data carrier is brought close to it. Reader/writer  18  includes a read/write controller  22  and a read/write head  20 . Read/write head  20  includes a coil antenna that receives a wireless signal from the coil antenna of data receiver and a modem that recovers original digital signal from the wireless signal in response to a request signal supplied from the robot-arm controller  24  to the read/write controller  22 . When the robot-arm controller  24  receives the test result from the wireless reader/writer  18 , the controller  24  operates the robot arm  8  according to the test result.  
         [0033]     The operation of the robot-arm controller  23  proceeds according to the flowchart of  FIG. 6 .  
         [0034]     Workpieces  2  that have been worked on by preceding work stations are successively transported on the conveyor system  1  carried on respective pallets  3  in the direction of arrow A. When one of these workpieces moves past the inspecting station ST 1 , the optical sensor  9  supplies a signal to the robot-arm controller  23 . Controller  23  recognizes that a workpiece is detected (step A 1 ) and starts counting the pulses supplied from the rotary encoder  12  to determine the location of the workpiece on a real-time basis and moves the robot arm  5  from its home position to the determined location of the workpiece so that its holder  15  comes to a position immediately above the workpiece (step A 2 ). Controller  23  enters a tracking mode in which the holder  15  keeps track of the moving workpiece (step A 3 ). While being moved at the same speed as the workpiece, the holder  15  is lowered to hold the workpiece (step A 4 ). Robot arm&#39;s holder  15  is then raised from the pallet  3  (step A 5 ) and the robot arm  5  is moved from the conveyor system  1  to the inspection unit  4  (step A 6 ). Holder  15  is lowered until the workpiece is in contact with the test bed of the inspection unit  4  (step A 7 ) and the holder  15  releases the workpiece (step A 8 ). Then, the robot-arm controller  23  raises the holder  15  (step A 9 ) and moves the arm  5  to its home position (step A 10 ).  
         [0035]     When the workpiece is set in position, the inspection unit  4  performs a test on it by supplying pressurized air to determine whether it is a nondefective product or a defective product. The result of the test is converted to a coded signal capable of correcting its bit errors and transmitted from the line transmitter  27  of inspection unit  4  to the line receiver  28  of robot-arm controller  23 . Line receiver  28  decodes the received signal and corrects bit errors, if present, caused by electromagnetic interference. When the robot-arm controller  23  receives the coded test result signal (step A 11 ), the robot arm  5  is moved from the home position to the inspection unit  4  (step A 12 ).  
         [0036]     When the robot arm&#39;s holder  15  approaches the tested workpiece, the controller  23  proceeds to step A 13 . In this step, the controller  23  sets the wireless reader/writer  17  in a data transfer mode by activating the reader/writer  17  and then loading the coded test result signal into the read/write controller  21 . During the time the reader/writer  17  is activated, the read/write controller  21  controls the read/write head  19  to begin transmission of the received test result signal to the data carrier  14  of the tested workpiece for writing the signal into its memory.  
         [0037]     As the data transmission proceeds, the controller  23  lowers the holder  15  and operates it to hold the tested workpiece (step A 14 ) and raises the holder  15  from the test bed of the inspection unit  4  (step A 15 ).  
         [0038]     Controller  23  determines the current position of the pallet  3 , which has been left vacant by the tested workpiece, from the count value of the pulses supplied from the rotary encoder  12  and controls the robot arm  5  so that its holder  15  comes to a position directly above the intended pallet (step A 16 ) and enters a pallet tracking mode in which the holder  15  keeps track of the pallet  3  moving in the direction of allow A (step A 17 ).  
         [0039]     During the time the robot arm&#39;s holder  15  is keeping track of the pallet, the holder  15  is lowered and releases the workpiece on the surface of the pallet (step A 18 ). Controller  23  terminates the data transfer mode by deactivating the reader/writer  17  (step A 19 ) and raises the arm&#39;s holder  15  (step A 20 ) and moves the robot arm  5  to the home position (step A 21 ). Controller  23  now returns to the starting point of the routine to repeat the same process on the next workpiece.  
         [0040]     Therefore, during the time between the instant the holder  15  approaches the tested workpiece and the instant the tested workpiece is replaced on the pallet, the wireless reader/writer  17  is activated and test result data is transferred to the data carrier of the tested workpiece and the data carrier  14  cooperates with the read/write controller  21  to receive the transmitted data and perform a writing process on the received data.  
         [0041]     When the inspected workpiece moves past the optical sensor  10  of sorting station ST 2 , the latter sends a signal to the robot-arm controller  24  of sorting station ST 2 .  
         [0042]     The following is a description of the operation of the controller  24  for sorting tested workpieces with reference to a flowchart and a timing diagram respectively shown in  FIGS. 7 and 8 .  
         [0043]     Controller  24  begins to operate according to the flowchart of  FIG. 7  by recognizing that a tested workpiece is arriving (step B 1 ). Controller  24  starts counting the pulses supplied from the rotary encoder  13  to determine the location of the tested workpiece on a real-time basis and moves the robot arm  8  from its home position to the determined location of the workpiece so that its holder  16  comes to a position directly above the workpiece (step B 2 ).  
         [0044]     Controller  24  proceeds to step B 3  to set the reader/writer  18  in a data fetching mode by activating the wireless reader/writer  18  and then wirelessly commanding its read/write controller  22  to send a request message to the data carrier of the tested workpiece, requesting it to transmit the stored test result data to the reader/writer  18 .  
         [0045]     Controller  24  enters a tracking mode in which the holder  16  keeps track of the moving workpiece (step B 4 ). While being moved at the same speed as the workpiece, the holder  16  is lowered to hold the workpiece (step B 5 ) and raised from the pallet  3  (step B 6 ).  
         [0046]     Since the stored data has been fetched from the data carrier of the tested workpiece in response to the data-fetch request of step B 3  before the tested workpiece is raised above the test bed (step B 6 ) as can be seen from  FIG. 8 , the controller  24  terminates the data fetching mode by deactivating the wireless reader/writer  18  (step B 7 ).  
         [0047]     At decision step B 8 , the controller  24  examines the test result data and determines whether the workpiece is nondefective or defective. If the workpiece is nondefective, the controller  24  proceeds to step B 9  to move the robot arm  8  to the nondefective-product bin  6 . Otherwise, the controller  24  proceeds to step B 10  to move the robot arm  8  to the defective-product bin  7 . In either case, the controller  24  lowers the holder  16  (step B 11 ), releases the workpiece in the intended bin (step B 12 ) and raises the holder  16  (step B 13 ). Controller  24  moves the arm  8  to its home position (step A 10 ) and returns to the starting point of the routine to repeat the same sorting process on the next workpiece.  
         [0048]     Since data transfer is performed wirelessly while the reader/writer is keeping track of the moving data carrier, a sufficient amount of time is given to transfer or fetch data. Thus, the conveyor system  1  is not required to stop or lower its speed at intervals. Further, the two communicating devices are mutually spaced a short distance apart, the communication channel is protected interference from other sources.  
         [0049]     Since the data carrier is attached to the workpiece, it is only necessary to write work-type information of the workpiece into the data carrier if different types of work are performed in sequence on the same conveyor system. If the data carrier is mounted on the pallet as in the aforesaid prior art, it would be necessary to maintain a record indicating the relationship between a workpiece and a pallet carrying it all the way through the conveyor system, in addition to writing the type-of-work information of the workpiece into the associated data carrier.