Patent Publication Number: US-2007112458-A1

Title: Assist transportation method and its device

Description:
TECHNICAL FIELD  
      The present invention relates to an assist transportation method and its device for decreasing the load to a worker when the worker operates transportation means to transport a product.  
     BACKGROUND ART  
      Conventionally, known is a work assist to which impedance control is applied by which a worker can perform transportation work while the worker feels as if he/she transports a light weight object though a heavy one. The work assist is a power assist provided with first to eighth movable bodies for supporting a heavy object, actuators for moving the movable bodies, and a controller for controlling outputs of the actuators, detecting a force to be indirectly applied to the heavy object by a worker by a force sensor in order to transport the heavy object fixed to the eighth movable body by worker&#39;s way, controlling the first to eighth movable bodies in accordance with the information, and reducing the load to the worker (for example, refer to Japanese Patent Laid-Open No. 2000-84881).  
      However in the case of the work assist disclosed in Japanese Patent Laid-Open No. 2000-84881, while a worker transports a heavy object or when the worker positions and sets the heavy object to a setting portion, even if the heavy object contacts with an obstacle, a reaction force generated in the heavy object due to the contact is not conducted to a worker operating the assist. Therefore, there is a problem that the worker cannot detect that the heavy object contacts with the obstacle and thereby continues transportation work, and the heavy object or the heavy-object setting portion may be damaged.  
      The present invention is made to solve the above problem of a conventional technique and its object is to provide an assist transportation method and a device capable of properly communicating a reaction force due to contact to a worker without damaging a product and an obstacle even if the product contacts with an obstacle at the time of work.  
     DISCLOSURE OF THE INVENTION  
      To solve the above problem, the invention of claim  1  is an assist transportation method for reducing a load applied to a worker when the worker operates transportation means to transport a product, in which when the product contacts with an obstacle, the product is floated from the transportation means to moderate the impact, the displacement value of the product due to floating is detected, the displacement value is processed to compute a reaction force due to the impact, and the reaction force is communicated to the worker.  
      According to the invention, when the product contacts with the obstacle, the impact is moderated by setting a floating mechanism between the transportation means and the product and the displacement value of the floating mechanism is processed to compute an impact force, and the reaction force by the impact force is communicated to the worker through the transportation means. Therefore, when the worker transports the product or sets the product to a component to be set, the worker can efficiently perform work while the worker feels that the worker contacts with any obstacle or component to be set without damaging a product or the component to be set even if the product contacts with any obstacle or component to be set.  
      The invention of claim  2  is an assist transportation device for reducing a load applied to a worker when the worker operates transportation means to transport a product, which includes holding means for holding a product, a floating mechanism set to the connection portion between the holding means and the transportation means, displacement detection means for detecting the displacement value of the floating mechanism, and control means for processing the displacement value detected by the displacement detection means and computing a reaction force, and communicates the reaction force to the worker operating the transportation means.  
      According to the invention, because the floating mechanism set between the holding means for holding a product and the transportation means, displacement detection means for detecting the displacement value of the floating mechanism, and control means for processing the displacement value detected by the displacement detection means and computing a reaction force are included, even if the product contacts with any obstacle or component to be set when the worker transports the product or sets the product to the component to be set, the product or the component to be set cannot be damaged. Moreover, the worker can efficiently perform work while feeling that the worker contacts with the obstacle or component to be set.  
      The invention of claim  3  is an assist transportation method for reducing a load applied to a worker when the worker operates transportation means to transport a product, in which a work area through which a product can freely move is set and a limit area formed adjacently to the work area for generating a predetermined reaction force so as to return a product to the work area when the product comes in is set.  
      According to the invention, because the work area through which a product can freely move is set and the limit area for generating a predetermined reaction force so as to return the product to the work area when the product comes in is set, the worker can efficiently perform the transportation work without being aware of an obstacle or without applying an impact to the product.  
      The invention of claim  4  is an assist transportation device for reducing a load applied to a worker when the worker operates transportation means to transport a product, which includes a work area through which the product can freely move, a limit area formed adjacently to the work area to generate a predetermined reaction force so as to return the product to the work area when the product comes in, and control means for processing the incoming value of the product incoming to the limit area to compute the reaction force.  
      According to the invention, because the word area through which the product can freely move, limit area formed adjacently to the work area to generate a predetermined reaction force so as to return the product to the work area when the product comes in, and control means for processing the incoming value of the product entering the limit area to compute the reaction force are included, the worker can efficiently perform transportation work without being aware of an obstacle or without applying an impact to the product.  
      The invention of claim  5  is an assist transportation method for reducing a load applied to a worker when the worker operates transportation means to transport a product, in which the product is floated from the transportation means, the displacement value of the product due to floating is detected when the worker holds the product and operates it in a direction for transporting the product, the displacement value is processed, and the product is assist-transported as a target value of the transportation means.  
      The invention of claim  6  is an assist transportation device for reducing a load applied to a worker when the worker operates transportation means to transport a product, which includes holding means for holding the product, operation handle set to the holding means for the worker to lead the product in a desired direction, floating mechanism set to the connection portion between the holding means and the transportation means, displacement detection means for detecting the displacement value of the floating mechanism, and control means for processing the displacement value detected by the displacement detection means to assist-transport the product as a target value of the transportation means.  
      According to inventions of claims  5  and  6 , it is possible to efficiently reduce a load applied to a worker while keeping a state having preferable operability without directly feeling driving of transportation means. Moreover, when a worker transports a product or sets the product to a component to be set, a load applied to the worker is reduced and even if the product contacts with any obstacle or component to be set, the product or component to be set is not damaged. Moreover, the worker can efficiently perform work while feeling that the product contacts with any obstacle or component to be set.  
      The invention of claim  7  is an assist transportation method for reducing a load applied to a worker who operates an operation handle set to transportation means to transport a product, in which the direction and magnitude of an operation force applied to the operation handle when the worker operates the product in a direction for transporting the product are detected, the direction and magnitude of an external force when the product contacts with an obstacle, directions and magnitudes of the operation force and the external force are processed to assist-transport the product as a target value of the transportation means, and the reaction force by the external force is communicated to the worker.  
      The invention of claim  8  is an assist transportation device for reducing a load applied to a worker for operating an operation handle set to transportation means to transport a product, in which holding means for holding the product, operation force detection means for detecting the direction and magnitude of an operation force applied to the operation handle set to the connection portion between the holding means and the transportation means, external force detection means set to the connection portion between the holding means and the transportation means to detect the direction and the magnitude of an external force applied to the holding means, and control means for processing the direction and magnitude of the operation force detected by the operation force detection means and the direction and magnitude of the external force detected by the external force detection means and assist-transporting the product as a target value of the transportation means are included and the reaction force by the external force is communicated to the worker.  
      According to inventions of claims  7  and  8 , it is possible to efficiently reduce a load applied to a worker while keeping a state of preferable operability without directly feeling driving of transportation means. Moreover, when a worker transports a product or sets the product to a component to be set, a load applied to the worker is reduced and the product or component to be set is not damaged even if the product contacts with any obstacle or component to be set. Furthermore, the worker can efficiently perform work while feeling that the product contacts with any obstacle or component to be set.  
      The invention of claim  9  is an assist transportation method for reducing a load applied to a worker for operating transportation means to transport a product, in which the direction and magnitude of an operation force when the worker holds the product and moves the transportation means in a direction for transporting the product are detected and the direction and magnitude of the operation force is processed to assist-transport the product as a target value of the transportation means.  
      The invention of claim  10  is an assist transportation device for reducing a load applied to worker for operating transportation means to transport a product, which includes holding means for holding the product, an operation handle set to the holding means to lead the product in a direction desired by the worker, external force detection means set to the connection portion between the holding means and the transportation means to detect the direction and magnitude of an external force applied to the holding means, and control means for processing the direction and magnitude of the external force detected by the external force detection means to assist-transport the product as a target value of the transportation means.  
      According to inventions of claims  9  and  10 , it is possible to efficiently reduce a load applied to a worker while keeping a state of preferable operability without directly feeling driving of the transportation means. Moreover, when a worker transports a product or sets the product to a component to be set, a load applied to the worker is reduced and even if the product contacts with any obstacle or component to be set, the product or component to be set is not damaged. Furthermore, the worker can efficiently perform work while feeling that the product contacts with any obstacle or component to be set.  
      The invention of claim  11  is an assist transportation method for reducing a load applied to a worker when the worker operates transportation means to transport a product, which comprises a condition setting step of setting a transportation area and assist condition every predetermined position of a transportation route and a transportation area setting step of setting a transportation area between adjacent predetermined positions and an assist condition through operations in accordance with the transportation area and the assist condition every predetermined position set in the condition setting step to set the transportation area of components.  
      According to the invention, because a transportation area and an assist condition every predetermined position of a transportation route and a transportation area and an assist condition are automatically set over the whole transportation route connecting predetermined positions, it is possible to easily set the transportation area. Therefore, it is possible to efficiently correspond to change of assist conditions due to change of transportation routes and change of transportation components.  
      The invention of claim  12  is an assist transportation method for reducing a load applied to a worker when the worker operates transportation means to transport a product, which comprises a transportation area confirmation step of confirming a transportation route and a transportation area in accordance with position data for a plurality of teaching points and transportation area data set every teaching point, a transportation-portion position confirmation step of obtaining the position of a transportation portion for supporting a product, and a transportation-portion-position moving step of obtaining a transportation route closest to the position of the transportation portion and moving the transportation portion to the predetermined position of the obtained transportation route or into transportation area of the obtained transportation route when the position of the transportation portion is out of the transportation area, wherein the transportation portion is returned into the transportation area when the position of the transportation portion for supporting a product is out of the transportation area.  
      According to the invention, when a transportation portion is out of a transportation area, it is possible to automatically move the position of the transportation portion onto the nearest transportation route or into the transportation area of the nearest transportation route. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic illustration of an instrument-panel setting station to which a first embodiment using an assist transportation method and its device of the present invention is applied;  
      FIGS.  2 ( a ) and  2 ( b ) are schematic diagrams of a floating mechanism, in which  FIG. 2 ( a ) is a perspective view of the floating mechanism and  FIG. 2 ( b ) is a schematic view showing the inside of the floating mechanism;  
       FIG. 3  is a block diagram of a control system for power assist control in the first embodiment using the assist transportation method and its device of the present invention;  
       FIG. 4  is a conceptual illustration of a reaction-power detection control in the first embodiment;  
      FIGS.  5  to  7  are illustrations of a work area setting method;  
       FIG. 8  is a schematic illustration of an instrument-panel setting station to which a second embodiment of an assist transportation method and its device of the present invention is applied;  
       FIG. 9  is a block diagram of a control system for power assist control in the second embodiment of the assist transportation method and its device of the present invention;  
       FIG. 10  is a conceptual illustration of an assist transportation control in the second embodiment;  
       FIG. 11  is a general schematic diagram of a vehicle-door assembly line to which an assist transportation method and its device of the present invention are applied;  
       FIG. 12  is a perspective view of transportation means;  
       FIG. 13  is a top view of the machine pedestal of transportation means;  
       FIG. 14  is a perspective view of the connection portion between transportation means and holding means;  
       FIG. 15  is an illustration of holding means;  
       FIG. 16  is a block diagram of a control system for power assist control of a third embodiment of an assist transportation method and its device of the present invention;  
       FIG. 17  is a conceptual illustration of an assist transportation control in the third embodiment;  
       FIG. 18  is an illustration of a door viewed from an inner panel side;  
      FIGS.  19 ( a ) and  19 ( b ) are illustrations of a door-glass elevating regulator, in which  FIG. 19 ( a ) is a back view of the regulator and  FIG. 19 ( b ) is an illustration viewed from the surface side;  
      FIGS.  20 ( a ) and  20 ( b ) are illustrations of a state of setting a door-glass elevating regulator in a door inner panel, in which  FIG. 20 ( a ) is a state diagram when inserting a door-glass elevating regulator into the opening of an inner panel and  FIG. 20 ( b ) is state diagram when the door-glass elevating regulator is rotated and fixed to the inner panel after inserting the regulator;  
       FIG. 21  is a perspective view of the connection portion between transportation means and holding means;  
       FIG. 22  is a block diagram of a control system for power assist control in a fourth embodiment of an assist transportation method and its device of the present invention;  
       FIG. 23  is a conceptual illustration of assist transportation control in the fourth embodiment;  
       FIG. 24  is a block diagram of a fifth embodiment of an assist transportation method and its device of the present invention;  
       FIG. 25  is an illustration showing a teaching job program;  
       FIG. 26  is an illustration showing an assist parameter table;  
       FIG. 27  is an illustration showing an assist area setting method;  
       FIG. 28  is an illustration showing the switching characteristic of assist impedance;  
      FIGS.  29 ( a ) and  29 ( b ) are illustrations of the relating processing between the present position and an assist area;  
       FIG. 30  is an illustration ( 1 ) of computation processing of assist area and assist impedance when the assist area and assist impedance are changed between teaching points;  
       FIG. 31  is an illustration ( 2 ) of computation processing of assist area and assist impedance when the assist area and assist impedance are changed between teaching points; and  
       FIG. 32  is an illustration of computation of the returning force of an invisible wall and switching processing of assist impedance, 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      Embodiments of the present invention are described below by referring to the accompanying drawings.  
      At the instrument panel setting station of a vehicle assembly line, vehicle bodies Wa positioned to a mounting jig set on a slat conveyer are continuously transported at equal speed in the direction of the arrow A as shown in  FIG. 1 .  
      A first embodiment using an assist transportation method and its device of the present invention is constituted as described below. In  FIG. 1 , an assist transportation device shows two states, that is, a position (original position) for horizontally (Y direction) holding an instrument panel P of the vehicle body Wa and a position of setting the instrument panel P to the vehicle body Wa.  
      A first frame body  1  is set above the vehicle assembly line in parallel with (X direction) the vehicle assembly line. Two slide rails  2  and one rack  3  are set to the first frame body  1  in parallel with the vehicle assembly line. A plurality of rollers  4  are rotatably engaged with the two slide rails  2  and a pinion gear  6  set to a motor  5  is engaged with the rack  3 . The rollers  4  and motor  5  are set to a support member  7 . The motor  5  is a motor for synchronizing the assist transportation device with the vehicle body Wa.  
      Moreover, a second frame body  8  is connected to the rollers  4  and the support member  7  of the motor  5 . Two slide rails  9  and one rack  10  are set to the second frame body  8  orthogonally to the vehicle assembly line. A plurality of rollers  11  are rotatably engaged with the two slide rails  9  and a pinion gear  13  set to a motor  12  is engaged with the rack  10 . The rollers  11  and motor  12  are set to a support member  14 . The motor  12  is a motor for power-assist-driving the assist transportation device in Y-axis direction.  
      Moreover, a third frame body  15  is connected to the rollers  11  and the support member  14  of the motor  12 . Two slide rails  16  and one rack  17  are set to the third frame body  15  in parallel with the vehicle assembly line. A plurality of slide guides are slidably engaged with the two slide rails  16  and a pinion gear  20  set to the motor  19  is engaged with the rack  17 . The slide guides and motor  19  are set to lower-face marginal portion of a table  21 . The motor  19  is a motor for power-assist-driving the assist transportation device in X-axis direction.  
      Furthermore, a telescopit-type slide guide  22  is set to the lower-face center of the table  21 , a feed screw (not illustrated) is set in the slide guide  22 , and a motor  23  is connected to the feed screw. The motor  23  is vertically set to the table  21 . The motor  23  is a motor for power-assist-driving the assist transportation device vertically (Z direction).  
      A cylindrical arm  24  is extended to the side facing the vehicle body Wa nearby the lower end of the slide guide  22  and a box  25  housing a floating mechanism is set to the front end of the arm  24 . Instrument panel holding means  27  for holding the instrument panel P is set to the face of the box  25  facing the traveling direction of the vehicle body Wa through the floating mechanism and an operation handle  28  is set to the face of the box  25  facing the vehicle body Wa.  
      As shown in  FIG. 2 , a floating mechanism  30  is provided with a fixed table  32  in which a pair of slide rails  31  are set horizontally (Y direction) to the front end of the vehicle body Wa, a first slide table  34  in which a slide guide  33  slidably engaged with the slide rails  31  is set to the rear face, and a second slide table  37  in which a slide guide  36  slidably engaged with a pair of slide rails  35  vertically (Z direction) set to the vehicle body Wa at the front end of the first slide table  34  is set to the rear face.  
      A centering member  38  to be held is set to the front center of the fixed table  32  and a pair of centering cylinders  39  in which the front end of a piston rod are faced to the horizontal direction (Y direction) of the vehicle body Wa in a state capable of holding the centering member  38  to be held is set to the rear face of the first slide table  34 . A displacement sensor is built in the centering cylinder  39  and thereby it is possible to always confirm a displacement value in the horizontal direction (Y direction) of the vehicle body Wa of the first slide table  34 .  
      Moreover, a centering member  40  to be held is set to the front center of the first slide table  34  and a pair of centering cylinders  41  in which the front end of a piston rod is faced in the vertical direction (Z direction) of the vehicle body Wa in a sate capable of holding the centering member  40  to be held are set to the rear face of the second slide table  37 . A displacement sensor is built in the centering cylinder  41  and thereby it is possible to always confirm a displacement value in the vertical direction (Z direction) of the vehicle body Wa of the second slide table  37 .  
      Moreover, a cylinder  42  directing the front end of a piston rod in the traveling direction of the vehicle body Wa is set to the front of the second slide table  37  and a pair of slide guides  43  are set in parallel with the cylinder  42 . A rectangular parallelepiped block  44  is fixed to the front end of the piston rod of the cylinder  42  and the front end of the slide guide  43  and an arm  45  for connecting the instrument panel holding means  27  is set to the front of the block  44 . A displacement sensor is built in the cylinder  42  and thereby it is possible to always confirm a displacement value in the cross-direction (X direction) of the vehicle body Wa of the block  44 .  
      As shown in  FIG. 1 , the instrument panel holding means  27  is constituted of a base pedestal  47  set to the front end of the arm  45  through a connection member  46  by directing the longitudinal direction to the horizontal direction (Y direction) of the vehicle body Wa, a pair of slide rails  48  set to both ends of the front of the base pedestal  47  in the horizontal direction (Y direction) of the vehicle body Wa, a pair of slide tables  50  set to a slide guide  49  slidably engaged with the slide rails  48 , a pair of support arms  52  having a plurality of connection pins  51  set to the slide tables  50 , and a pair of cylinders  53  for sliding the support arms  52  toward the reference hole  26  of the instrument panel P.  
      Moreover, load cells (force sensors) for detecting forces in orthogonal three-axis directions are built in the setting portion of the operation handle  28  of the box  25  supporting the instrument panel holding means  27  to always detect forces applied to the horizontal direction (Y direction) of the vehicle body Wa, cross direction (X direction) of the vehicle body Wa, and vertical direction (Z direction) of the vehicle body Wa. Forces detected by these force sensors are used for power-assist control of this device.  
      Displacement values detected by displacement sensors built in the cylinders  39 ,  41 , and  42  of the floating mechanism  30  are used to generate a reaction force when the instrument panel P held by the instrument panel holding means  27  contacts with the vehicle body Wa or an obstacle.  
      As shown in  FIG. 3 , a control system for power assist control in the first embodiment using an assist transportation method and its device is constituted of a force sensor  60  for detecting forces in orthogonal three-axis directions set to the setting portion of the operation handle  28 , displacement sensor  61  for detecting displacement values in orthogonal three axis directions set to the floating mechanism  30 , position instruction computing portion  62 , position control portion  63 , motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  serving as assist driving actuators, and position and speed detection means  64  for detecting positions and speeds of the motors  12 ,  19 , and  23 .  
      The information on forces applied to the horizontal direction (Y direction) of the vehicle body Wa, cross direction (X direction) of the vehicle body Wa, and vertical direction (z direction) of the vehicle body Wa detected by the force sensor  60  are input to the position instruction computing portion  62 . The position instruction computing portion  62  computes assist-driving data F for the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  to perform assist driving in accordance with the force information and inputs the data F to the position control portion  63 .  
      The position control portion  63  performs control so that the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  perform assist driving in accordance with the assist driving data F. In this case, positions and speeds of the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  are detected by the position and speed detection means  64  and fed back to the position instruction computing portion  62  and position control portion  63 .  
      Moreover, as shown in  FIG. 4 , when the instrument panel P held by the instrument panel holding means  27  contacts with the vehicle body Wa or an obstacle, at least one of three displacement sensors  61  set to the floating mechanism  30  detects a displacement value x and the displacement value x is input to the position instruction computing portion  62 .  FIG. 4  shows one axis (X axis) and it is assumed that the X-axis cylinder  42  of the floating mechanism  30  for connecting the instrument panel holding means  27  with the arm  24  of the assist transportation device has the same characteristic as a spring.  
      The position instruction computing portion  62  computes reaction-force generation data f in accordance with the information on the displacement value x. In this case, by assuming f=K·x, it is possible to create rigidity feeling as a spring constant in which K can be set to an optional value. Therefore, as the displacement value x increases, a worker feels a larger reaction force. It is possible to use not only the displacement value x but also the speed and acceleration to compute a reaction force.  
      Moreover, the position instruction computing portion  62  subtracts the reaction force generation data f from the assist driving data F for the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  to perform assist driving and inputs the instruction value of the position computed by using the subtraction result (F-f) to the position control portion  63 .  
      The position control portion  63  performs control so that the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  perform assist driving while generating reaction forces with the subtraction result (F-f). In this case, positions and speeds of the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  are detected by the position and speed detection means  64  and fed back to the position instruction computing portion  62  and the position control portion  63 .  
      Moreover, in the case of an assist transportation method and its device of the present invention, by making it possible for the assist to freely move through a space in an operation range when operating the assist, it interferes with the vehicle body Wa or the like. Therefore, as shown in  FIG. 5 , by setting not a mechanical limiter having impact feeling but a limiter for controlling a movable range in software so as to hold a work area We in the operation range in the cross direction (X direction) of the vehicle body Wa, it is possible to form limit areas La and Lb in an area exceeding the limiter. Moreover, it is possible to form a limit area so as to hold the work area We in the operation range in the horizontal direction (Y direction) of the vehicle body Wa and the vertical direction (Z direction) of the vehicle body Wa.  
      In the work area We, power assist driving according to normal impedance control is performed and in the limit areas La and Lb, it is changed to impedance control using a control expression including the expression of rigidity characteristic (f=Kd·(x−xd), x&gt;xd or x&lt;−xd) is started. In this case, f denotes a force so that the instrument panel P returns to the work area We from the limit areas La and Lb, Kd denotes a spring constant which can be set to an optional value, x denotes the coordinate value at an end of a workpiece (instrument panel P), xd denotes a coordinate value of the vehicle body Wa with which an end of the workpiece (instrument panel P) may contact, and (x−xd) denotes an entry value (entry distance from work area We) to the limit areas La and Lb of the workpiece (instrument panel P).  
      Moreover, because the spring constant Kd can be set to an optional value by software, it is possible to change the value by limit areas, for example, by the limit areas La and Lb or change the value in accordance with the distance from the work area We in the limit areas La and Lb.  
      Furthermore, as shown in  FIG. 6 , when putting the workpiece (instrument panel P) into the vehicle body Wa from a front-door opening by synchronizing the workpiece with vehicle body Wa transported by a slat conveyer and setting the workpiece to a predetermined position, it is possible to set the workpiece so that the work area We and limit areas La and Lb move synchronously with the vehicle body Wa. In this case it is also possible to set the work area We and limit areas La and Lb in accordance with a coordinate system at the vehicle body Wa side.  
      Moreover, as shown in  FIG. 7 , in one cycle until the workpiece (instrument panel P) is set to the vehicle body Wa after being held, it is possible to change limit areas in accordance with an operation mode (workpiece setting preparation mode, workpiece setting mode, or in-vehicle moving mode).  
      For example, it is possible to set the limit areas La and Lb to both ends of the operation range in the cross direction (X direction) of the vehicle body Wa orthogonal to the traveling direction (Y direction) of the workpiece in the work setting preparation mode and work setting mode. Moreover, in the vehicle moving mode, it is possible to set limit areas Lc and Ld to both ends of the operation range in the horizontal direction (Y direction) of the vehicle body Wa in which the workpiece may contact with the vehicle body Wa and the limit area Lb to either end of the operation range in the cross direction (X direction) of the vehicle body Wa. Therefore, it is possible to move the workpiece (instrument panel P) along the limit areas La, Lb, Lc, and Ld.  
      Operations of the assist transportation device and the assist transportation method of the first embodiment constituted as described above are described below. To hold the instrument panel P transported to the instrument panel supply position B shown in  FIG. 1 , a worker operates the operation handle  28  of the assist transportation device stopped at the original position, opens a pair of support arms  52 , and moves the instrument panel holding means  27  up to the instrument panel supply position B in which the instrument panel is mounted on a carriage (not illustrated).  
      Then, by facing the connection pin  51  to the reference hole  26  of the instrument panel P and then driving the cylinder  53 , and inserting the connection pin  51  into the reference hole  26 , the instrument panel holding means  27  holds the instrument panel P. Moreover, when raising the instrument panel P from the carriage and operating the operation handle  28  in a direction for moving the instrument panel P, the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  perform assist driving for reducing a load of a worker.  
      Then, by operating the operation handle  28  so that the instrument panel P moves synchronously with the vehicle body Wa, the instrument panel P is further transported into the vehicle body Wa from the front-door opening of the vehicle body Wa to move the panel P nearby the instrument-panel-setting positioning pin Wp set to the vehicle body Wa. In this case, the instrument-panel-setting positioning pin Wp may contact with a bracket on which a pin-inserting guide hole is formed or an end of the instrument panel P may contact with the vehicle body Wa at a high probability.  
      When the instrument panel P contacts with the vehicle body Wa, a cylinder located in the direction in which the instrument panel P is returned among the cylinders  39 ,  41 , and  42  set to the floating mechanism  30  is contracted and a displacement sensor built in the cylinder detects the displacement value. The motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  are controlled so that a worker for operating the assist transportation device feels a reaction force due to contact between the instrument panel P and the vehicle body Wa.  
      According to the above assist control, the worker detects that the instrument panel P approaches its setting position and transports the instrument panel P to a position nearby the setting portion of the vehicle body Wa and then can perform the setting work by manually delicately adjusting the position of the instrument panel P. The range of position adjustment in this case can be absorbed by the floating mechanism  30 . Therefore, no impact is added to this device.  
      When the above setting work is completed and the worker brings the instrument panel holding means  27  to the outside of the vehicle body Wa, the worker operates the operation switch for work completion. Then, the assist transportation device automatically returns to the original position without contacting with the vehicle body Wa or facilities around a line.  
      Moreover, the work area We of the instrument panel holding means  27  is previously set by setting the limit areas La and Lb. Therefore, the worker does not make the instrument panel P contact with the vehicle body Wa or facilities around the line while transporting the instrument panel P.  
      Moreover, even if the worker operates the operating handle  28  so as to move the instrument panel holding means  27  from the work area We to the limit areas La and Lb, motors  12 ,  19 , and  23  serving as power-assist driving actuators is controlled so that an impact does not occur and a reaction force for returning the instrument panel holding means  27  to the work area We occurs. Therefore, no impact is applied to this device or instrument panel P. Therefore, the worker can perform work without being aware of boundaries between the work area We and the limit areas La and Lb.  
      Then, second embodiment of an assist transportation method and its device of the present invention has a configuration same as the above-described first embodiment except that a pair of operation handles  28   a  and  28   b  are set to the instrument panel holding means  27  and a control system is used.  
      As shown in  FIG. 9 , a control system for power assist control in the second embodiment is constituted of displacement sensors  61  for detecting displacement values in orthogonal three-axis directions set to the floating mechanism  30 , target value computing portion  65 , control portion  66 , motor (for Y axis)  12 , motor (for X axis)  19 , motor (for Z axis)  23  serving as assist driving actuators, and position and speed detection means  64  for detecting positions and speeds of the motors  12 ,  19  and  23 .  
      As shown in  FIG. 10 , when a worker grips operation handles  28   a  and  28   b  and leads the instrument panel P held by the instrument panel holing means  27  in a desired direction, at least one of three displacement sensors  61  set to the floating mechanism  30  detects a displacement value and the displacement value is input to the target value computing portion  65 .  
      Moreover, when the instrument panel P held by the instrument panel holding means  27  contacts with the vehicle body Wa or an obstacle, at least one of three displacement sensors  61  set to the floating mechanism  30  detects a displacement value and the displacement value is input to the target value computing portion  65 .  FIG. 10  shows one axis (X axis) and it is assumed that the X-axis cylinder  42  of the floating mechanism  30  for connecting the instrument panel holding means  27  with the arm  24  of the assist transportation device has the same characteristic as a spring.  
      The target value computing portion  65  computes target values (target trajectory, speed, and assist force) of an assist transportation device in accordance with displacement values of the displacement sensors  61 . For example, when it is assumed that x is a displacement value of the displacement sensor  61 , pd is a target trajectory, Kd is a desired spring coefficient, Dd is a desired viscous friction coefficient, and Md is a desired mass, the following expression (1) is effected. 
 
 d   2   Pd/dt   2 =( Kdx+Dddx/dt )/ Md   (1) 
 
      For simplification, the expression is shown by only one axis (X axis). Actually, there are three axes (X, Y, and Z).  
      Moreover, the target value computing portion  65  computes target values (target trajectory, speed, and assist force) in accordance with the expression (1) for the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  to drive an assist in accordance with the expression (1) and inputs the target values to the control portion  66 .  
      The control portion  66  controls the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  so as to follow computing results (trajectory: pd, speed: dpd/dt, and acceleration: d 2 pd/dt 2 ) by the target value computing portion  65 . In this case, positions and speeds of the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  are detected by the position and speed detection means  64  and fed back to the target value computing portion  65  and control portion  66 .  
      Operations of the assist transportation device of the second embodiment constituted as described above and an assist transportation method are described below. To hold the instrument panel P transported to the instrument panel supply position B shown in  FIG. 8 , a worker operates the operation handles  28   a  and  28   b  of the assist transportation device stopped at the original position, opens a pair of support arms  52 , and mounts the instrument panel P on a carriage (not illustrated), and moves the instrument panel holding means  27  up to the instrument panel supply position B in which the instrument panel is mounted on a carriage (not illustrated).  
      Then, by directing the connection pin  51  to the reference hole  26  of the instrument panel P and then, driving the cylinder  53 , and inserting the connection pin  51  into the reference hole  26 , the instrument panel holding means  27  holds the instrument panel P. Moreover, when the work raises the instrument panel P from the carriage and operates the operation handles  28   a  and  28   b  in a direction for moving the instrument panel P, the motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  perform assist driving for reducing a load applied to the worker.  
      Then, the operation handles  28   a  and  28   b  are operated so that the instrument panel P moves synchronously with the vehicle body Wa and moreover, the instrument panel P is transported into the vehicle body Wa from the front-door opening portion of the vehicle body Wa and moved up to the vicinity of the instrument-panel-setting positioning pin Wp set to the vehicle body Wa. In this case, the instrument-panel-setting positioning pin Wp may contact with a bracket on which a pin inserting guide hole of the instrument panel P is formed or an end of the instrument panel P may contact with the vehicle body Wa at a high probability.  
      When the instrument panel P contacts with the vehicle body Wa, a cylinder located in the direction in which the instrument panel P is returned among the cylinders  39 ,  41 , and  42  set to the floating mechanism  30  contracts and the displacement sensor  61  built in the cylinder detects the displacement value. The motor (for Y axis)  12 , motor (for X axis)  19 , and motor (for Z axis)  23  are controlled so that a worker operating the assist transportation device feels a reaction force due to contact between the instrument panel P and the vehicle body Wa in accordance with a displacement value detected by the displacement sensor  61 .  
      In accordance with the assist control, the worker feels that the instrument panel P approaches its setting position and transports the instrument panel P up to the vicinity of the setting portion of the vehicle body Wa and then, can perform the setting operation by manually performing delicate position adjustment. Because the range for position adjustment can be absorbed by the floating mechanism  30 , no impact is applied to this device.  
      When the above setting work is completed and the worker brings the instrument panel holding means  27  to the outside of the vehicle body Wa, the worker operates an operation switch for work end. Then, the assist transportation device automatically returns to the original position without contacting with the vehicle body Wa or circumferential facilities.  
      Then, a third embodiment of an assist transportation method and its device of the present invention is applied to the door-glass elevating-regulator setting step portion of a vehicle door assembly line so that a door-glass elevating regulator can be efficiently set to a vehicle door to be pitch-fed.  
      That is, as shown in  FIG. 11 , the vehicle door assembly line  101  includes a door transportation line  102  for pitch-feeding a vehicle door W and a plurality of setting step portions  103  to be sequentially arranged from the upstream side to the downstream side of the door transportation line  102  and each setting component is set to the door W by the setting step portions  103 .  
      Moreover, some of the setting step portions  103  are used as step portions for setting a door-glass elevating regulator R and the transportation means  104  shown in  FIG. 12  is set to the step portion for setting the door-glass elevating regulator R.  
      In the door transportation line  102 , a pair of right and left doors W of the same vehicle is pitch-transported and the sets are aligned and vertically mounted on one rectangular pallet p ( FIG. 12 ) while directing inner panel-Wi sides in the same direction. A plurality of pallets p are proximity-arranged along the line and at the same time the pallets p are transported by a constant stroke and stopped for a certain period and the above operations are repeated.  
      As shown in  FIG. 12 , the transportation means  104  includes a portal machine pedestal  105  set so as to straddle the door transportation line  102  and holding means  106  capable of moving in the multispindle direction from the machine pedestal  105  and the holding means  106  is constituted as a setting apparatus for setting the door-glass-elevating regulator R ( FIG. 19 ) so that it can be moved between a component supply position A set nearby the machine pedestal  105  and a setting position B of the stopped door W.  
      First, relevant equipment is described. A pair of upper and lower slide rails  108  is set to either side of an upper beam  107  of the machine pedestal  105  and a rack  109  is set between the slide rails  108 ,  
      Then, a slide table  112  is slidably engaged with the slide rails  108  through a slide guide  111 , a first motor (for X axis)  113  is set to the slide table  112  as an actuator and a pinion gear to be driven by the first motor  113  is protruded to the back of the slide table  112  and engaged with the rack  109 . Therefore, the slide table  112  can horizontally move by the operation of the first motor  113 .  
      Moreover, a support table  115  is set to the surface of the slide table  112  through a setting pedestal, a pair of slide guides  116  is set to the surface of the support table  115 , a second motor  117  (for Z axis) is set to the back of the support table  115  as one of actuators, the rotating shaft of the second motor  117  protrudes to the surface side of the support table  115 , and a pinion gear (not illustrated) is set to the front end of the rotating shaft. Furthermore, the pinion gear gears with a rack  119  of an elevating table  118  to be described below.  
      The elevating table  118  includes a pair of slide rails  121  to be slidably engaged with the slide guide  116  of the support table  115  and the rack  119  set between the slide rails  121  so that it can be vertically moved in accordance with the operation of the second motor  117 .  
      A support pedestal  122  protruding forward is set to the lower end of the elevating table  118  and a third motor  123  (for horizontal-rotational S shaft) as a part of an actuator. Moreover, the output shaft of the third motor  123  is connected to the proximal end of a horizontal arm  124  horizontally protruded from the lower portion of the support pedestal  122  via the gear and the horizontal arm  124  can be rotated about the vertical shaft at the proximal end side by the driving of the third motor  123  as shown in  FIG. 13 .  
      By driving the first to third motors (X axis, Z axis, and x axis)  113 ,  117 , and  123 , it is possible to change positions of a product (door-glass-elevating regulator R) in a three-dimensional space.  
      Moreover, as shown in  FIG. 14 , fourth to sixth motors (for rotation)  125 ,  127 , and  128  are set as some of actuators whose output shafts are orthogonal to each other. That is, the fourth motor (for rotational α axis)  125  is vertically set to the upper face at the front end of the horizontal arm  124 , a vertical arm  126  is connected to the output shaft of the fourth motor  125 , the fifth motor (for rotational α axis)  127  is set to the lower end of the vertical arm  126  through a bracket  127   a , the sixth motor (for rotational γ axis) is set to the output shaft of the fifth motor  127  through a bracket  128   a , and the holding means  106  is set to the output shaft of the sixth motor  128  through the setting portion  129   a  of an operation handle  129  and a box  130 .  
      By driving the fourth to sixth motors (α axis, β axis, and γ axis)  125 ,  127 , and  128 , it is possible to change attitudes of the product (door-glass-elevating regulator R) in a three dimensional space.  
      Moreover, six-axis force/torque sensors for operation inputs for detecting the direction and magnitude of an operation force generated when a worker operates the operation handle  129  are set to the setting portion  129   a  of the operation handle  129  and six-axis interference detection force/torque sensors for detecting the direction and magnitude of an external force when the product (door-glass-elevating regulator R) contact with an obstacle is set to the box  130 . Forces detected by these force/torque sensors are used for power assist control of this device.  
      Actuators of the first to sixth motors (X axis, Z axis, S axis, α axis, β axis, and γ axis)  113 ,  117 ,  123 ,  125 ,  127 , and  128  realize switching control of an automatic transportation mode which does not require a worker and an assist transportation mode capable of reducing a load applied to a worker though requiring the worker. Moreover, when a mode change switch is changed to the automatic transportation mode, the holding means  106  automatically moves through a previously taught route. When the automatic transportation mode is changed to the assist transportation mode, a load applied to the worker is reduced when the worker indirectly moves the holding means  106  by the operation handle  129 .  
      Then, the holding means  106  is described below. As shown in  FIG. 15 , the holding means  106  has a machine pedestal table  131  connected to the output shaft of the sixth motor  128  through the box  130  and setting portion  129   a  of the operation handle  129  and the machine pedestal table  131  has a holding mechanism portion  132  for holding the door-glass-elevating regulator R, a positioning mechanism portion  133  for positioning the door-glass-elevating regulator R to a predetermined position of the door W, and a fastening mechanism portion  134  for setting the door-glass-elevating regulator R to the door W.  
      Moreover, the door-glass-elevating regulator R is inserted into the space portion between an inner panel Wi and an outer panel Wo through an opening portion H of the inner panel Wi of the door W shown in  FIG. 18 , positioned by the positioning mechanism portion  133 , and then fastened and fixed with bolts by the fastening mechanism portion  134 .  
      The holding mechanism portion  132  includes a first cylinder  135  set to the front of the machine pedestal table  131 , substrate  136  connected to the front end of a cylinder rod  135   a  of the first cylinder  135 , motor  137  set to the front of the substrate  136 , and table  138  set to the front of the rotating shaft of the motor  137 . A plurality of attraction pads  141  and a bossed positioning pin  142  are set to the table  138  via each bracket  139  and the bossed positioning pin  142  can be inserted into the reference hole k ( FIG. 19 ( b )) of the door-glass-elevating regulator R.  
      Moreover, a slide rail (not illustrated) is set to the side of the substrate  136  and slidably fitted to the slide guide  143  extended from the front of the machine pedestal table  131 . Therefore, the substrate  136  can be slid vertically to the machine pedestal table- 131  face by the operation of the first cylinder  135  and the table  138  can be rotated by a predetermined angle by the operation of the motor  137 .  
      Furthermore, by attracting the attraction pads  141  to the surface (face in  FIG. 19 ( b )) of the plate portion of the door-glass-elevating regulator R while inserting the bossed positioning pin  142  into the reference hole k of the door-glass-elevating regulator R, the door-glass-elevating regulator R can be held and the door-glass-elevating regulator R is tilted to an attitude not interfering with the margin of the opening H of the inner panel Wi and inserted by the motor  37  and then the attitude of the door-glass-elevating regulator R can be converted into a setting attitude.  
      In the case of the positioning mechanism portion  133 , a support member  144  is set to the front end of a support rod  147  extended from the machine pedestal table  131  through a bracket  150  and a bossed pin  145  to be inserted into the reference hole of the inner panel and an inner panel contact member  146  made of resin or rubber contacting with a predetermined portion of the inner panel are set to the support member  144 . Moreover, a pair of positioning mechanism portions  133  is used while holding the holding mechanism portion  132 .  
      Moreover, by inserting the bossed pin  145  of the positioning mechanism portion  133  into the reference hole t ( FIG. 18 ) of the inner panel and bringing the inner-panel contact member  146  into contact with the inner panel Wi at a predetermined position, the door W and holding means  106  are aligned.  
      The fastening mechanism portion  134  includes a nut runner  148  slidably engaged with a slide rail (not illustrated) formed on the side of the support rod  147  fixed to the machine pedestal table- 131  side through a slide guide and a second cylinder  151  for advancing or retreating the nut runner  148  to or from the inner panel Wi-side. The second cylinder  151  is connected to a slide-guide-provided table  149  integrated with the nut runner- 148  side through a connection member  152 .  
      Moreover, the nut runner  148  is advanced or retreated to or from the inner panel Wi in accordance with the telescopic motion of the second cylinder  151 . A pair of nut runners  148  is used. Moreover, when positioning the door-glass-elevating regulator R to the setting attitude, the nut runner  148  advances and the fixing operation is performed through bolt fastening.  
      When a worker pushes the operation handle  129  in a direction for moving the handle  129  while gripping a deadman switch, the automatic transportation mode is changed to the assist transportation mode so that the handle  129  can be transported by a small force. When the worker releases his hand from the deadman switch, the assist transportation mode is changed to the automatic transportation mode.  
      As shown in  FIG. 16 , a control system for power assist control in the third embodiment is constituted of six-axis operation-input force/torque sensors  160  set to the setting portion of the operation handle  128  to detect the direction and magnitude of an operation force by a worker applied to the operation handle, six-axis interference detection force/torque sensors  161  set to the box  130  to detect the direction and magnitude of an external force when the product (door-glass-elevating regulator R) contact with an obstacle, target value computing portion  162 , control portion  163 , position control motors (X axis, Z axis, and S axis)  113 ,  117 , and  123  serving as assist driving actuators, attitude control motors (α axis, β axis, and γ axis)  125 ,  127 , and  128 , and position and speed detection means  164  for detecting positions and speeds of the motors  113 ,  117 ,  123 ,  125 ,  127 , and  128 .  
      As shown in  FIG. 17 , when a worker grips the operation handle  129  and leads the door-glass-elevating regulator R held by the holding means  106  in a desired direction, at least one axis of six-axis operation input force/torque sensors  160  set to the setting portion  129   a  of the operation handle  129  detects an operation force and the operation force is input to the target value computing portion  162 .  
      Moreover, even if the door-glass-elevating regulator R held by the holding means  106  contacts with the door W or an obstacle, at least one axis of the six-axis interference detection force/torque sensors  161  detects an external force and the external force is input to the target value computing portion  162 .  FIG. 17  shows one axis (X axis).  
      The target value computing portion  162  computes target values (target trajectory, speed, and assist force) of the assist transportation device in accordance with operation forces (direction and magnitude) detected by the operation input force/torque sensors  160  and external forces (direction and magnitude) detected by the interference detection force/torque sensors  161 .  
      For example, when assuming that X-directional forces detected by the interference detection force/torque sensor  161  is F x , moments around X axis detected by the interference detection force/torque sensors  161  is Nx, X-directional forces detected by the operation input force/torque sensors  160  is f x , moments around X axis detected by the operation input force/torque sensors  160  is n x , X-directional target trajectory is x, target trajectory of rotation around X axis is θ, desirable mass is M, desirable moment of inertia as I, desirable X-directional viscous friction coefficient is D xd , and desirable viscous friction coefficient around X axis is D θd , the following expressions (2) and (3) are effected. 
 
 d   2   x/dt   2 ( f   x   −F   x   −D   xd   ·dx/dt )/ M   (2) 
 
 d   2   θ/dt   2 =( n   x   −N   x   −D   θd   ·dθ/dt )/ I   (3) 
 
      The expressions are shown only by one axis direction (X axis direction) for simplification. In fact, expressions (2) and (3) are effected for six axes (X axis, Z axis, S axis, α axis, β axis, and γ axis).  
      Moreover, the target value computing portion  162  computes target values (target trajectory, speed, and assist force) for the position control motors (X axis, Z axis, and S axis)  113 ,  117 , and  123  and attitude control motors (α axis, β axis, and γ axis)  125 ,  127 , and  128  to perform assist driving in accordance with the expressions (2) and (3) and inputs the target values to the control portion  163 .  
      The control portion  163  controls the position control motors (X axis, Z axis, and S axis)  113 ,  117 , and  123  and the attitude control motors (α axis, β axis, and γ axis)  125 ,  127 , and  128  so as to follow computing results (trajectory: x, speed; dx/dt, and acceleration: d 2 x/dt 2 ) by the target value computing portion  162 . In this case, positions and speeds of the position control motors (X axis, Z axis, and S axis)  113 ,  117 , and  123  and the attitude control motors (α axis, β axis, and γ axis)  125 ,  127 , and  128  are detected by the position and speed detection means  164  and fed back to the target value computing portion  162  and control portion  163 .  
      Operations of the assist transportation device and the assist transportation method of the third embodiment constituted as described above are described below.  
      When a pair of right and left doors W are pitch-fed along the door transportation line  102 , the door-glass-elevating regulator R is automatically transported to the setting position B by the transportation means  104 . That is, when the holding means  106  holds the door-glass-elevating regulator R at the component supply position A, the regulator R is automatically transported toward a predetermined point nearby the setting position B in accordance with a route set in the automatic transportation mode. In this case, it is allowed to hold the door-glass-elevating regulator R in the automatic mode or assist mode.  
      When the regulator R reaches the predetermined point nearby the setting position B, the mode of each actuator is changed to the assist transportation mode. Therefore, when the worker pushes the operation handle  129  in a direction for moving the handle  129  while gripping the deadman switch of the holding means  106 , the holding means  106  is moved up to the setting position B. Moreover, when the worker passes through the opening H of the inner panel Wi of the door W, the door-glass-elevating regulator R is inserted by tilting its attitude so that the regulator R does not interfere with the margin of the opening H by operating another switch as shown in  FIG. 20 ( a ).  
      Furthermore, after the worker passes through the above opening H, the bossed pin  145  of the positioning mechanism portion  133  is inserted into the reference hole t of the inner panel Wi until the bossed portion contacts with the surface and at the same time, positioning is performed by bringing the inner panel contact member  146  into contact with the surface of the inner panel Wi. Thereafter, by returning the tilt of the door-glass-elevating regulator R and slightly moving it to the inner panel-Wi side, the door-glass-elevating regulator R contacts with the inner panel Wi.  
      Then, the nut runner  148  provided with a bolt advances to the inner panel-W 1  side, the bolt is passed through the bolt hole x of the inner panel Wi and fastened and fixed to a nut to be set to the door-glass-elevating regulator R. Thereby, the nut runner  148  can be set in the state shown in  FIG. 20 ( b ).  
      When the setting work to either of the right and left doors W is completed, the worker releases his hand from the deadman switch. Then, the operation mode of the holding means  106  is changed to the automatic mode and the holding means  106  automatically moves to the component supply position A by following a decided route. Then, the holding means  106  holds the next door-glass-elevating regulator R and automatically transports it up to a portion nearby the setting position B in accordance with the same procedure.  
      Moreover, when the holding means  106  comes up to a predetermined point by transporting the regulator R, the present mode is changed to the assist transportation mode in accordance with the procedure same as the above described and the regulator R is set to the other door W in accordance with the same procedure. Then, transportation of the door transportation line  102  is stopped until setting of the regulator R to two doors W is completed. When setting to two doors W is completed, the next pallet p (door W) comes through pitch transportation.  
      According to the above procedure, by using the holding means  106  and thereby setting the door-glass-elevating regulator R to the doors W, it is possible to very efficiently perform work and moreover, because the inner panel Wi and outer panel Wo are previously integrated, the versatility of setting of other door setting components is not impaired.  
      When work is performed in the automatic transportation mode and any trouble occurs, by changing an operation switch to the assist mode, it is possible to perform transportation between all points in the assist mode. In this case, impedance setting when returning the component transportation means  104  to a point or area decided in the automatic transportation mode is automatically performed.  
      Then, as shown in  FIG. 21 , fourth embodiment using an assist transportation method and its device of the present invention has the same configuration as the third embodiment except that an operation handle  229  is set to the holding means  106  set to the output shaft of the sixth motor  128  through the box  130  and a control system is used.  
      As shown in  FIG. 22 , the control system for power assist control of the fourth embodiment is constituted of six-axis interference detection force/torque sensors  161  set to the box  130  to detect the direction and magnitude of an external force when the product (door-glass-elevating regulator R) contacts with an obstacle, target value computing portion  262 , control portion  263 , position control motors (X axis, Z axis, ands axis)  113 ,  117 , and  123  serving as assist driving actuators, attitude control motors (α axis, β axis, and γ axis)  125 ,  127 , and  128 , and position and speed detection means  164  for detecting positions and speeds of the motors  113 ,  117 ,  123 ,  125 ,  127 , and  128 .  
      As shown in  FIG. 23 , when a worker grips the operation handle  229  and leads the door-glass-elevating regulator R held by the holding means  106  in a desired direction, at least one axis of the six-axis interference detection force/torque sensors  161  set to the box  130  detects an operation force and the operation force is input to the target value computing portion  262 .  
      Moreover, when the door-glass-elevating regulator R held by the holding means  106  contacts with the door W or an obstacle, at least one axis of the six-axis interference detection force/torque sensors  161  set to the box  130  detects an external force and the external force is input to the target value computing portion  262 .  FIG. 23  shows one axis (X axis).  
      The target value computing portion  262  computes target values (target trajectory, speed, and assist force) of the assist transportation device in accordance with operation forces and external forces detected by the interference detection force/torque sensors  161 . For example, when assuming that the X-directional force detected by the interference detection force/torque sensor  161  is F x , the moment around X axis detected by the interference detection force/torque sensor  161  is N x , X-directional target trajectory is x, target trajectory of rotation around x axis is θ, desirable mass is M, desirable moment of inertia is I, desirable X-directional viscous friction coefficient is D xd , and desirable viscous friction coefficient around X axis is D θd , the following expressions (4) and (5) are effected. 
 
 d   2   x/dt   2 =(− F   x   −D   xd   ·dx/dt ) M   (4) 
 
 d   2   θ/dt   2 =(− N   x   −D   θd   ·dθ/dt )/ I   (5) 
 
      The expression is shown by only axis direction (X axis direction) for simplification. In fact, the expressions (4) and (5) are effected for six axes (X axis, Z axis, S axis, α axis, β axis, and γ axis).  
      Moreover, the target value computing portion  262  computes target values (target trajectory, speed, and assist force) for the position control motors (X axis, Z axis, and S axis)  113 ,  117 , and  123  and attitude control motors (α axis, β axis, and γ axis)  125 ,  127 , and  128  to perform assist driving in accordance with the expressions (4) and (5) and inputs the values to the control portion  263 .  
      The control portion  263  controls the position control motors (X axis, Z axis, and S axis)  113 ,  117 , and  123  and attitude control motors (α axis, β axis, and γ axis)  125 ,  127 , and  128  so as to follow the computing results (trajectory: x, speed: ds/dt, and acceleration: d 2 x/dt 2 ) by the target value computing portion  262 . In this case, positions and speeds of the position control motors (X axis, Z axis, and S axis)  113 ,  117 , and  123  and attitude control motors (α axis, β axis, and γ axis)  125 ,  127 , and  128  are detected by the position and speed detection means  164  and fed back to the target value computing portion  262  and control portion  263 .  
      Then, the fifth embodiment using an assist transportation method and its device of the present invention is applied to the door-glass-elevating-regulator setting step portion of the vehicle door assembly line  101  shown in  FIG. 11 . The vehicle door assembly line  101  includes a door transportation line  102  for pitch-feeding the vehicle door W and a plurality of setting step portions  103  to be sequentially arranged from the upstream side to the downstream side of the door transportation line  102  and each setting component is set to the door W by these setting step portions  103 .  
      Moreover, some of the setting step portions  103  are used as a step of setting the door-glass-elevating regulator R and the component transportation apparatus (transportation means)  104  shown in  FIG. 12  is set. The component transportation apparatus  104  can transport and set the door-glass-elevating regulator R which is a component.  
      As shown in  FIG. 24 , a controller  360  is constituted of a teaching apparatus I/F (interface) portion  361 , setting control portion  362 , and transportation and assist control portion  363 . The controller  360  is constituted by using a microcomputer system.  
      The transportation and assist control portion  363  includes an assist parameter table generating portion  364 , assist parameter table  365 , position computing portion  366 , transportation area setting portion  367 , state display portion  368 , and motor driving control portion  369 .  
      The assist parameter generating portion  364  generates the assist parameter table  365  in accordance with various commands and data supplied from the teaching apparatus  300  through the teaching-apparatus I/F portion  361 . When a remote control mode is set by the teaching apparatus  300 , various commands output from the teaching apparatus  300  are supplied to the motor driving control portion  369  through the teaching-apparatus I/F portion  361  and assist-parameter-table generating portion  364 . Thereby, by individually driving motors  313 ,  317 ,  323 , and  325  by the teaching apparatus  300 , it is possible to move the holding means  106  to a desired position.  
      The position computing portion  366  computes the present position of the holding means  106  in accordance with the position data (including angle data) detected by a first position encoder  312  for detecting the position of the slide table  112 , second position encoder  318  for detecting the position of the support table  115 , third position encoder  324  for detecting the rotational position (rotation angle) of the horizontal arm  124 , and fourth position encoder  326  for detecting rotational position (rotation angle) of the vertical arm  126 .  
      Three-dimensional present position data is supplied to the assist-parameter-table generating portion  364  and transportation area setting portion  367 . Moreover, the present position data is supplied to the teaching apparatus  300  from the assist-parameter-table generating portion  364  through the teaching-apparatus I/F portion  361 . The teaching apparatus  300  can display the present position data on the screen of an image display unit. Moreover, the teaching apparatus  300  can set the present position data as a teaching-point position.  
      The teaching apparatus  300  can supply a previously-generated teaching job program to the transportation and assist control portion  363  through the teaching-apparatus I/F portion  361 .  
      The assist-parameter-table generating portion  364  has a nonvolatile memory for storing the teaching job program. The assist-parameter-table generating portion  364  writes the teaching job program supplied from the teaching apparatus  300  in the nonvolatile memory. The assist-parameter-table generating portion  364  updates the teaching job program stored in the nonvolatile memory whenever the teaching job program is supplied from the teaching apparatus  300 . When power is supplied to the controller  360 , the assist-parameter-table generating portion  364  reads the teaching job program from the nonvolatile memory and generates the assist parameter table  365 .  
      The width W and height H of an assist area, spring coefficient AK and friction coefficient AD of an invisible wall (virtual wall), virtual mass M, virtual friction coefficient D, reaction force coefficient HK, and reaction force friction coefficient HD are set by a teaching job program for each teaching point and whether to perform automatic movement up to the next teaching point or switch to assist transportation is set. When automatic movement up to the next teaching point is performed, movement speed is set. Moreover, an audio output of an operation guidance for a worker is set according to necessity.  
       FIG. 25  is an illustration showing a teaching job program. Line number 0002 shows an example of setting the width W of an assist area to 200 mm, the height H of the assist area to 100 mm, spring coefficient AK of an invisible wall to 10, and friction coefficient AD of the invisible wall to 70 by assist area setting commands. Line number 0003 shows an example of setting virtual mass M to 10, virtual friction coefficient D to 30, reaction force coefficient HK to 50, reaction force friction coefficient HD to 100 by impedance setting commands. Numerical values set by the assist area setting commands and assist impedance setting commands are effective until numerical values are set by the next assist area setting command and assist impedance setting commands. Line number 0005 shows a setting example for performing automatic movement up to the next teaching point P 2  at a speed V=200 (mm/sec). Line number 0008 shows an example of outputting an audio message for prompting switching to the assist mode. Line number 0015 shows an example of setting the assist moving speed V up to the next teaching point P 4  to 30 (mm/sec).  
       FIG. 26  is an illustration showing an assist parameter table. The assist-parameter-table generating portion  364  generates the assist parameter table  365  for relating teaching points to various parameters as shown in  FIG. 26  by deciphering a teaching job program shown in  FIG. 25 . The assist parameter table  365  is stored in a volatile memory such as a RAM. Thereby, the transportation area setting portion  367  can read an assist parameter at a high speed.  
       FIG. 27  is an illustration showing an assist area setting method. The transportation area setting portion  367  sets an assist area in accordance with the assist parameter table  365 . The transportation area setting portion  367  sets a spatial area having a width W and a height H on a plane orthogonal to a transportation route along a transportation route (teaching trajectory) for connecting teaching points P 1  to P 6  as an assist area. The assist area is set so that its center becomes the transportation route (teaching trajectory). When the width W and height H differ between teaching points, the width W and height H are set so that they are slowly changed along the transportation route.  FIG. 27  shows a transportation route of the door-glass-elevating regulator R. In this case, the teaching point P 1  corresponds to the component supply position A and the teaching point P 5  corresponds to the setting position B.  
      The transportation area setting portion  367  determines to which assist area the present position (position of component to be transported) of the holding means  106  supplied from the position computing portion  366  corresponds, computes the return force of an invisible wall, and switches assist impedances. When the holding means  106  is moved in a direction separate from the assist area, a return force according to the invisible-wall spring coefficient is output from the transportation area setting portion  367 .  
      Because the motor driving control portion  369  drives the motors  313 ,  317 ,  323 , and  325  so that the return force acts, the holding means  106  (transportation component) is not out of the assist area. In other words, it is possible to move the holding means  106  only in a tunnel-like transportation area comparted by the invisible wall in either case of automatic movement and assist movement. Moreover, in the case of this embodiment, an example of forming a rectangular assist area is shown. However, it is possible to properly set the shape of the assist area in accordance with the shape of a component to be transported or work conformation.  
       FIG. 28  is an illustration showing the switching characteristic of an assist impedance. In the initial stages of automatic movement and assist movement, the virtual mass M and virtual friction coefficient D are set to small values so that a characteristic suited to transport a component at a high speed is obtained. Moreover, the virtual mass M and virtual friction coefficient D are maximized for setting so that a characteristic suited to finely move components is obtained and setting feedback can be securely obtained by increasing the reaction force coefficient HK and reaction-force friction coefficient HD.  
      FIGS.  29 ( a ) and  29 ( b ) are illustrations of processing for relating the present position with an assist area. As shown in  FIG. 29 ( a ), the transportation area setting portion  367  searches a teaching point closest to the present point (present position). In this case, P(N) is selected as a shortest-distance teaching point. Then, the transportation area setting portion  367  examines whether an intersection of a perpendicular from the present point is present in segments for two segments P(N−1) to P(N) and P(N) to P(N+1) contacting with the shortest teaching point P(N). As shown by (case  1 ) in  FIG. 29 ( b ), when the intersection of the perpendicular is present in both segments, a segment in which the distance between the intersection and the present point is smaller is selected. As shown by (case  2 ), when the intersection of the perpendicular is not present in both segments, a segment in which the intersection is present is selected. As shown by (case  3 ), when the intersection is not present in both segments, a segment in which the distance from the intersection with a straight line obtained by extending the segment up to P (N) is smaller is selected.  
       FIGS. 30 and 31  are illustrations of processing for computing an assist area and assist impedance when the assist area and assist impedance are changed between teaching points. When the transportation area setting portion  367  selects a segment, it computes an assist area at the present position for the selected segment (transportation route). As shown in  FIG. 30 , the segment Pa to Pb is selected. When the range of the assist area is different in one teaching point Pa and the other teaching point Pb, the range of the assist area is changed every transportation position (present point). Therefore, it is necessary to sequentially set an assist area every present point. In  FIG. 30 , the width of the assist area is set Wa and height H of it is set to Ha at one teaching point Pa and the width of the assist area is set to Wb and the height of it is set to Hb at the other teaching point Pb. The distance between teaching points is L. Therefore, when the perpendicular intersection is present in Pa to Pb and the distance from the teaching point Pa up to the perpendicular intersection of the present point is assumed as a, the width W of the assist area at that position is obtained in accordance with the following expression (6).  
      Moreover, the height H of the assist area is obtained in accordance with the following expression (7). 
 
 W=Wa− ( Wa−Wb )× a+L   (6) 
 
 H=Ha −( Ha−Hb )× a+L   (7) 
 
      When the perpendicular intersection is present at the outside of the teaching point Pa, W is set to Wa and H is set to Ha. When the perpendicular intersection is present at the outside of the teaching point Pb, W is set to Wb and H is set to Hb.  
      The transportation area setting portion  367  similarly perform computation for the invisible-wall spring coefficient AK and invisible-wall friction coefficient AD. Specifically, when the spring coefficient of the teaching point Pa is set to AKa and the friction coefficient of it is set to ADa and the spring coefficient of the teaching point Pb is set to AKb and the friction coefficient of it is set to ADb, the spring coefficient AK at the position of the distance a is obtained in accordance with the following expression (8) and the friction coefficient AD is obtained in accordance with the following expression (9). 
 
 AK=AKa =( AKa−AKb )× a÷L   (8) 
 
 AD=ADa −( ADa−ADb )× a÷L   (9) 
 
      As shown in  FIG. 31 , the virtual mass M and virtual friction coefficient D at the present point is computed and the reaction-force coefficient HK and reaction-force friction coefficient HD are computed in accordance with the same computation method.  
      FIGS.  32 ( e ) and  32 ( f ) are illustrations of computing of return force of an invisible wall and switching of an assist impedance. When the transportation area setting portion  367  sets an assist area and assist impedance for the present point, it computes the return force of an invisible wall and switches an assist impedance in accordance with the positional relation between the present point and the assist area. As shown by the case  1 , when the present point is present in the assist area, the return force F is zero. As shown by the case  2 , when the present point is protruded in the width or height direction, a return force corresponding to the protrusion value is computed. As shown by the case  3 , when the present point is protruded in both width and height direction, a return force in which a width-directional return force and height-directional return force are synthesized is computed. Moreover, by switching an assist impedance to a value (D+AD) obtained by adding invisible-wall friction coefficient AD to the virtual friction coefficient D at the outside of the assist area, the viscosity of the invisible wall is shown.  
      The motor driving control portion  369  shown in  FIG. 24  drives the motors  313 ,  317 ,  323 , and  325  so as to return the present point (position of holding means  106 , that is, transportation position of transportation component) in an assist area in accordance with the return force computed by the transportation area setting portion  367 . Thereby, when the position of the holding means  106  is present out of the transportation area in an initial state when supplying power to the transportation means  104 , it is possible to automatically return the holding means  106  to a predetermined position in the transportation area. Moreover, after returning the position of the holding means  106  into the transportation area, it is possible to move the holding means  106  through a transportation route in the automatic transportation mode or assist transportation mode.  
      In  FIG. 24 , reference numeral  370  denotes a mode change switch for changing the automatic transportation mode and assist transportation mode. Reference numeral  371  denotes a deadman switch. The deadman switch  371  is a three-position switch which becomes a turned-on (close) state while operating a switch lever by a preferable force and becomes a turned-off (open) state in a non-operation state or when strongly gripping the switch lever. The motor driving control portion  369  stops supply of power to the motors  313 ,  317 ,  323 , and  325  and stops supply of a work assist force (assist force) even if the mode change switch  370  is set to the assist transportation mode side when the deadman switch  371  is the turned-off (open) state.  
      The deadman switch  371  is set to the gripping portion (assist grip) of the operation lever set to the machine pedestal table  131  of the holding means  106 . An operating force/torque sensor  372  for detecting the operation force and operation direction by a worker is set to the operation lever. The operating force/toque sensor  372  can use at least a sensor capable of detecting operation forces in three-axis directions. Specifically, by using at least three pressure sensors and three load cells, the operation force in each direction is detected. The motor driving control portion  369  controls work assist forces (assist forces) supplied from the motors  313 ,  317 ,  323 , and  325  correspondingly to each-directional operation force in the assist transportation mode.  
      A transportation component is set to the vertical arm  126  in a floating state through a floating mechanism. When the transportation component or the holding mechanism portion  132  contacts with a setting portion, a displacement occurs in the floating state and the displacement is detected by a displacement sensor  306 . The motor driving control portion  369  computes a setting feedback force in accordance with the displacement direction, displacement value, reaction force coefficient HK, and reaction force friction coefficient HD detected by the displacement sensor  306  to reduce work assist forces (assist forces) supplied from the motors  313 ,  317   323 , and  325 . Thereby, the worker can feel the setting feedback force through the operation lever.  
      Brake mechanisms  313 A,  317 A,  323 A, and  325 A are set to output shaft sides of the motors  313 ,  317 ,  323 , and  325 . These brake mechanisms  313 A,  317 A,  323 A, and  325 A are respectively constituted so as to mechanically stop the rotation of each motor. The brake mechanisms  313 A,  317 A,  323 A, and  325 A are respectively constituted so as to cancel a brake state when power is supplied to, for example, a solenoid.  
      The motor driving control portion  369  controls the brake mechanisms  313 A,  317 A,  323 A, and  325 A to a brake cancel state before operating the motors  313 ,  317 ,  323 , and  325 . The motor driving control portion  369  controls the brake mechanisms  313 A,  317 A,  323 A, and  325 A to a brake state after a preset delay time elapses from the point of time when stopping operations of the motors  313 ,  317 ,  323 , and  325 . However, in the case of a configuration capable of detecting rotations of the motors  313 ,  317 ,  323 , and  325 , it is allowed to control the brake mechanisms  313 A,  317 A,  323 A, and  325 A to a brake state at the point of time when rotations of the motors are stopped. Thus, it is possible to eliminate an impact when stopping component transportation.  
      The state display portion  368  includes various types of display units for respectively displaying an operation state and alarm of the transportation means  104  and a voice synthesizer for generating a voice message such as operation guide for a worker.  
      The setting control portion  362  controls various operations of the holding means  106 . When an attraction switch  381  is operated, the setting control portion  362  drives an attraction pump  388  to make an attraction pad  341  attract a transportation component. When an advance switch  382  or retreat switch  383  is operated, the setting control portion  362  drives a first cylinder  335  to advance or retreat the substrate  336  of a fastening mechanism  334 . When a clockwise-rotation switch  384  or counterclockwise-rotation switch  385  is operated, the setting control portion  362  drives a motor  337  to return the attitude of a transportation component to a tilted state or the original state. When a setting start switch  386  is operated, the setting control portion  362  drives a second cylinder  351  and drives a nut runner  348  through a nut runner driving portion  389  to make the nut runner  348  fasten a bolt. When a setting completion switch  387  is operated, the setting control portion  362  completes bolt fastening work and notifies the transportation and assist control portion  363  that setting is completed.  
      Then, a specific example of the operation for supplying a component in the automatic transportation mode, setting the component in the assist transportation mode, and returning to a component receiving position (origin) in the automatic transportation mode is described. In this case, it is assumed that the mode change switch  370  is set to the automatic transportation mode side and the holding means  106  returns to the component receiving position (origin). When the transportation and assist control portion  363  detects that a not-illustrated component receiving completion switch is operated, it automatically transports the holding means  106  up to the teaching point P 3  through the teaching point P 2  and then stops transportation. The transportation and assist control portion  363  generates a voice message for prompting change to the assist transportation mode. When the mode change switch  370  is changed to the assist transportation mode side and the deadman switch  371  is turned on, the transportation and assist control portion  363  power-assists the movement of the holding means  106  in accordance with an output of the operating force/torque sensor  372 . Thereby, assist movement and assist positioning are made and components are set.  
      When the transportation and assist control portion  363  receives from the setting control portion  362  a notice showing that setting is completed, it generates a voice message for prompting change to the automatic operation mode. When the mode change switch  370  is changed to the automatic transportation mode side, the deadman switch  371  is turned off, and a not-illustrated automatic operation start switch is operated, the transportation and assist control portion  363  starts automatic movement of the holding means  106 . Thereby, the holding means  106  is moved to the component receiving position (origin) P 1  through the teaching point P 6 .  
      In the case of this embodiment, an assist area is also set to an automatic moving route. Therefore, even if assist transportation is performed instead of automatic transportation, it is possible to transport a component along a transportation route. Because an assist area is narrower as approaching a component setting position, it is possible to assist-move the component up to the vicinity of the setting position. Moreover, because an assist impedance is increased as approaching the component setting position, a worker can accurately perform positioning and setting work.  
      Moreover, in the case of this embodiment, even if the position of the holding means  106  is deviated from an automatic moving route, it is possible to automatically return the holding means  106  into an automatic transportation route or transportation area (assist area).  
     INDUSTRIAL APPLICABILITY  
      According to the present invention, even if a product contacts with any obstacle or component to be set when a worker sets a product to a transportation component or component to be set, the worker can efficiently perform the transportation work without being aware of the obstacle or applying an impact to the product.  
      Moreover, the worker can efficiently perform the transportation work without being aware of an obstacle or applying an impact to the product.  
      Therefore, by applying the present invention to the setting work of an automatic production line which can be hardly fully automated, it is possible to improve a work environment and cost performance.