Patent Publication Number: US-2022219334-A1

Title: Sensor assembly and suction apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to a sensor assembly and a suction apparatus. 
     BACKGROUND ART 
     A work robot including a robot arm with a plurality of arm members is known in the related art. Patent document 1 discloses, for example, a robot hand (robot arm) used in a conveyance robot for holding and conveying an object to be conveyed, the robot hand including: a hand body; a plurality of bellows-type suction pads provided on the hand body, expandable and contractible in an axial direction with elastic force, and suctioning the object to be conveyed using vacuum pressure; and an axial length sensor for measuring an axial length of each bellows-type suction pad that is suctioning the object to be conveyed. 
     RELATED ART DOCUMENT 
     Patent Document 
     Patent Document 1: JP 2011-107011A 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     In the above-described conventional technique, the axial length sensor of the robot hand detects the object to be conveyed, and does not detect the amount of deformation of the suction pad. Accordingly, it may not be possible to accurately determine whether or not the suction pad is in a state in which it is possible to suction the object to be conveyed. 
     In one aspect, the present invention was made in consideration of this situation, and the object of the present invention is to provide a sensor that is attachable to a suction apparatus, and can measure the amount of deformation of a suction portion such as a suction pad. 
     Means for Solving the Problems 
     In order to solve the above-described issues, the present invention adopts the following configuration. 
     A sensor assembly according to one aspect of the present disclosure is a sensor assembly that is attachable to a suction apparatus including a suction portion configured to suction an object with negative pressure, and a shaft configured to support the suction portion and having an air passage, the sensor assembly includes: a main body in which a space through which the shaft of the suction apparatus passes is formed; one or more first proximity sensors that are disposed on the main body, and configured to detect that the suction portion is deformed by the negative pressure; a fixture that has a fixed portion that is fixed to the shaft, and a support portion that is configured to support the main body. 
     According to the above configuration, the sensor assembly can be attached to the shaft of the suction apparatus that supports the suction portion and has the air passage, and the first proximity sensor can be disposed on the suction portion. In addition, the distance between the first proximity sensor and the suction portion can be easily changed, and the degree of freedom of the installation position of the first proximity sensor is high. Furthermore, it is possible to measure the amount of deformation of the suction portion using the first proximity sensor. 
     In the sensor assembly according to the one aspect, the support portion may extend from the fixed portion toward the suction portion. 
     With the above configuration, the first proximity sensor can be disposed on the upper portion of the suction portion to be closer to the suction portion, and the amount of deformation of the suction portion can be easily measured. In addition, the S/N ratio (signal-to-noise ratio) is improved due to bringing the first proximity sensor closer to the suction portion. 
     In the sensor assembly according to the one aspect, the main body may be supported by the support portion on a suction portion side relative to the fixed portion. 
     With the above configuration, when a pipe is provided on the shaft, the fixed portion can be attached above the pipe. Accordingly, the first proximity sensor can be brought closer to the suction portion, and the amount of the deformation of the suction portion can be easily measured. In addition, the S/N ratio (signal-to-noise ratio) is improved by bringing the first proximity sensor closer to the suction portion. 
     In the sensor assembly according to the one aspect, a plurality of the first proximity sensors may be disposed on the main body along a circumferential direction of the shaft. 
     With this configuration, it is possible to eliminate blind spots of the plurality of the first proximity sensors. 
     In the sensor assembly according to the one aspect, the one or more first proximity sensors may be disposed in a circular shape covering the suction portion. 
     In the above configuration, an appropriate proximity sensor can be selected in accordance with the size of the main body. 
     In the sensor assembly according to the one aspect, a plurality of the first proximity sensors may be disposed on the main body along a radial direction with respect to the shaft. 
     With the above configuration, it is possible to obtain the details of the deformation of the suction portion by observing the suction portion with higher resolution. As a result, the state of deformation of the suction portion can be accurately measured. 
     In the sensor assembly according to the one aspect, the sensor assembly may further include one or more third proximity sensors that are disposed on a radially outer side of the first proximity sensor with respect to the shaft in the main body, and that is configured to detect the object. 
     With the above configuration, in addition to the amount of displacement of the suction portion, the state of the object to be suctioned can also be measured. As a result, the detection accuracy can be improved, and the operation speed of the suction apparatus can be increased. 
     In the sensor assembly according to the one aspect, the sensor assembly may further include one or more second proximity sensors that are disposed on a side surface of the main body, and that are configured to detect an object approaching the side surface of the main body. 
     With the above configuration, the state of the side surface of the sensor assembly can be measured, and for example, it is possible to prevent collision between the sensor assembly and the object approaching the suction apparatus. 
     In the sensor assembly according to the one aspect, a plurality of the second proximity sensors may be disposed on the side surface of the main body along the circumferential direction of the shaft. 
     With the above configuration, the state of the side surface of the sensor assembly can be measured accurately, and for example, it is possible to prevent collision between the sensor assembly and objects approaching the suction apparatus from a plurality of directions. 
     A suction apparatus according to one aspect of the present disclosure includes: the sensor assembly; a suction portion configured to suction an object with negative pressure; and a shaft configured to support the suction portion and having an air passage. 
     According to the above configuration, the sensor assembly is attachable to the shaft that supports the suction portion and has the air passage, and the first proximity sensor can be disposed on the suction portion. In addition, the distance between the first proximity sensor and the suction portion can be easily changed, and the degree of freedom of the installation position of the first proximity sensor is high. Furthermore, it is possible to measure the amount of deformation of the suction portion using the first proximity sensor. 
     In the suction apparatus according to the one aspect, the suction portion may include a conductive member at a portion to be displaced, and the one or more first proximity sensors may be capacitive sensors or electromagnetic induction sensors. 
     With the above configuration, it is possible to accurately detect the contact between the suction portion and the object, and the amount of deformation of the suction portion, regardless of the physical properties of the object such as the permittivity and the magnetic permeability of the object. 
     In the suction apparatus according to the one aspect, the suction portion may be grounded. 
     With the above configuration, the electrostatic capacitance of the suction portion is increased, and the electric potential of the suction portion is stabilized, so that the influence of disturbance can be reduced. Accordingly, the detection accuracy is improved. 
     Effects of the Invention 
     According to one aspect of the present invention, it is possible to provide a sensor assembly that is attachable to a suction apparatus, and can measure an amount of deformation of a suction portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  a diagram illustrating an example of a configuration of a suction apparatus according to the present embodiment. 
         FIG. 2  is a cross-sectional view taken along line A-A of  FIG. 1 . 
         FIG. 3  is a diagram illustrating an example of a configuration of a sensor assembly according to the present embodiment. 
         FIG. 4  is a partially enlarged diagram illustrating an example of a configuration of the sensor assembly according to the present embodiment. 
         FIG. 5  is a diagram showing a change in the positional relationship between the suction apparatus and an object to be suctioned. 
         FIG. 6  is a diagram illustrating an example of the result of the measurement of a capacitance value performed by the sensor assembly according to the present embodiment related to detection of an object having a low permittivity. 
         FIG. 7  is a schematic diagram illustrating an example of a hardware configuration of the mobile suction apparatus according to the embodiment. 
         FIG. 8  is a diagram illustrating the definition of an amount of deformation of the suction pad that is used in the embodiment of the present invention. 
         FIG. 9  is a diagram illustrating another definition of an amount of deformation of the suction pad that is used in the embodiment of the present invention. 
         FIG. 10  is a diagram illustrating orientation control of the suction pad according to the embodiment of the present invention. 
         FIG. 11  is a flowchart showing the operation of the suction apparatus in the embodiment of the present invention. 
         FIG. 12  is a flowchart showing the operation of a suction apparatus in another embodiment of the present invention. 
         FIG. 13  is a flowchart showing the operation of a suction apparatus in still another embodiment of the present invention. 
         FIG. 14  is a block diagram illustrating an example of a configuration of a suction apparatus according to the present embodiment in a modified example 1. 
         FIG. 15  is a block diagram illustrating an example of a schematic configuration of a suction apparatus according to the present embodiment in a modified example 2. 
         FIG. 16  is a flowchart showing an example of a flow of a process of the suction apparatus according to the present embodiment in the modified example 2. 
         FIG. 17  is a schematic diagram illustrating an example of the flow of the process of the suction apparatus according to the present embodiment in the modified example 2. 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     An embodiment according to one aspect of the present invention (hereinafter, also referred to as “present embodiment”) will be described with reference to the drawings. 
     1. Application example 
     First, an example of a situation to which the present invention is applied will be described with reference to  FIG. 1 .  FIG. 1  is a diagram illustrating an example of the configuration of a suction apparatus  1  according to the present embodiment. The suction apparatus  1  can be used as a mobile robot that conveys an object. 
     As shown in  FIG. 1 , the suction apparatus  1  includes a sensor assembly  101 , a suction portion  112  that suctions an object with negative pressure, a shaft  133  that supports the suction portion  112  and has an air passage, and a tube  134  connected to the air passage. Examples of the suction portion  112  include a suction pad that holds an object by suctioning the object with negative pressure. 
     The sensor assembly  101  is attachable to the suction apparatus  1 , and includes a main body  102 , one or more first proximity sensors  114 , and a fixture  104 . A space through which the shaft  133  passes is formed in the main body  102 . The first proximity sensor  114  is disposed on the main body  102 , and detects the suction portion  112  that is deformed with negative pressure. The fixture  104  has a fixed portion  141  that is fixed to the shaft  133 , and a support portion  142  that supports the main body  102 . 
     The first proximity sensor  114  may be a sensor capable of measuring a short distance, or may also be a sensor capable of measuring a certain distance. Examples of a detection method of the first proximity sensor  114  include a capacitive method, an optical method, an electromagnetic induction method, and an acoustic method such as a sound wave method or an ultrasonic method. Also, examples of the capacitive sensor include a self-capacitive sensor and a mutual capacitive sensor. The one or more first proximity sensors provided in the sensor assembly may be of the same type, or may also be of the different types. 
     The sensor assembly  101  is attachable to the shaft  133  of the suction apparatus  1  that supports the suction portion  112  and has the air passage, and the first proximity sensor  114  can be disposed on the suction portion  112 . The first proximity sensor  114  measures the amount of deformation of the suction portion  112  that is deformed by negative pressure. By measuring the amount of deformation, it is possible to accurately determine whether or not the suction portion  112  is in a state in which it is possible to suction an object (workpiece)  61 . Furthermore, it is not necessary to change the design of the end effector of the suction apparatus  1  every time the sensor assembly  101  is attached to the suction apparatus  1 . 
     2. Configuration example 
     Suction Apparatus 
     Hereinafter, the configuration of the suction apparatus  1  according to an embodiment of the present invention will be described with reference to  FIG. 1 .  FIG. 1  is a diagram illustrating examples of the configuration of the suction apparatus  1  according to the present embodiment.  FIG. 2  illustrates examples of the sensor assembly  101  in a cross-sectional view taken along line A-A of  FIG. 1 . 
     In the example of  FIG. 1 , the suction apparatus  1  includes a sensor assembly  101 , a suction portion (suction pad)  112 , and a shaft  133 . An air passage for suctioning air is provided in the shaft  133 . The air passage is connected to the suction portion  112  and a tube  134 . The shaft  133  and a vacuum pump that generates negative pressure may also be connected via the tube  134 . The suction portion  112  of the suction apparatus  1  may also be grounded. 
     Because the suction portion  112  is disposed on one side of the shaft  133 , the position where the sensor assembly  101  is attached to the shaft  133  is preferably the other end side of the shaft  133 , for example. However, in order to accurately detect the deformation of the suction portion  112 , the main body  102  is preferably disposed at a position close to the suction portion  112 , for example. 
     The support portion  142  of the fixture  104  extends from the fixed portion  141  toward the suction portion  112 . The main body  102  is disposed on a suction portion  112  side with respective to the fixed portion  141  using the support portion  142 . With this configuration, it is possible to fix the fixture  104  to the other end side (the opposite side to the suction portion  112 ) of the shaft  133 , and to dispose the sensor assembly  101  at a position close to the suction portion  112 . 
     Sensor Assembly 
     In the example of  FIG. 1 , the sensor assembly  101  includes the main body  102 , one or more first proximity sensors  114 , and the fixture  104 . 
     A space  105  (not shown) through which the shaft  133  of the suction apparatus  1  passes is formed in the main body  102 . The space  105  may be a hole, or may also be a notch. The main body  102  is not in contact with the shaft  133 , for example. The main body  102  may have a circular shape, a quadrangular shape, or an elliptical shape. In addition, the space  105  may have a circular shape, a quadrangular shape, or an elliptical shape. The main body  102  and a controller such as a programmable logic controller (PLC) may be connected via a sensor wiring  151 . 
     In the example of  FIG. 2( a ) , the first proximity sensor  114  is disposed on the main body  102  along the circumferential direction of the space  105  (the shaft  133 ). In the example of  FIG. 2( b ) , a plurality of the first proximity sensors  114  are disposed on the main body  102  along the circumferential direction of the space  105  (the shaft  133 ). In the example of  FIG. 2( c ) , a plurality of the first proximity sensors  114  are disposed on the main body  102  along the circumferential direction and the radial direction with respect to the space  105  (the shaft  133 ). In the example of 
       FIG. 2( d ) , the space  105  has a quadrangular shape, and the first proximity sensor  114  is disposed on the main body  102  having a quadrangular outer shape. In the example of  FIG. 2( e ) , the space  105  has a circular shape, and the first proximity sensor  114  is disposed on the main body  102  having a quadrangular outer shape. In the example of  FIG. 2( f ) , the first proximity sensor  114  is disposed on the quadrangular main body  102  in which the space  105  has a circular shape. In the example of  FIG. 2( g ) , the first proximity sensor  114  is disposed on the elliptical main body  102  in which the space  105  has an elliptical shape. In the example of  FIG. 2( h ) , a plurality of the first proximity sensors  114  that are sensor chips are disposed on the main body  102  along the circumferential direction of the space  105  (the shaft  133 ). 
       FIG. 3  illustrates an example of the configuration of the sensor assembly  101 . In the example of  FIG. 3( a ) , the sensor assembly  101  includes the main body  102  shown in the example of  FIG. 2( a ) . The first proximity sensor  114  provided in the main body  102  can measure the amount of displacement of the suction portion  112 . The first proximity sensor  114  is disposed above the suction portion  112 . In the example of  FIG. 3( b ) , the sensor assembly  101  includes the main body  102  shown in the example of  FIG. 2( c ) . The plurality of first proximity sensors  114  are disposed on the main body  102  along the radial direction with respect to the shaft  133 . With this configuration, the sensor assembly  101  can individually detect displacement at a plurality of positions in the radial direction of the suction portion  112 . In the example of  FIG. 3( c ) , the sensor assembly  101  includes the main body  102  shown in the example of  FIG. 2( c ) . The main body  102  includes one or more third proximity sensors (first proximity sensors  114 ) that are disposed radially outward of the first proximity sensors  114  with respect to the axis  133 , and that detect an object. Because the main body  102  includes these third proximity sensors, in addition to measurement of the amount of displacement of the suction portion  112  using the first proximity sensors  114 , the state of the object to be suctioned with the suction portion  112  can also be measured by the third proximity sensors (first proximity sensors  114 ). As a result, the detection accuracy can be improved, and the operation speed of the suction apparatus can be increased. The example of  FIG. 3( d )  shows a configuration in which the suction portion  112  shown in  FIG. 3( c )  is replaced with another larger suction portion  112 . The sensor assembly  101  includes a plurality of the first proximity sensors  114  that are arranged along the radial direction. Accordingly, the sensor assembly  101  can detect deformation of (the outer end portion of) the suction portion  112 , with respect to suction portions  112  having a plurality of sizes. Also, when the sensor assembly  101  includes the main body  102  shown in the example of  FIG. 2( c ) , the plurality of first proximity sensors  114  are disposed in a circle covering the suction portion  112 . With this configuration, an appropriate proximity sensor can be selected in accordance with the size of the main body. 
       FIG. 4  is a diagram illustrating an example of the configuration of the sensor assembly  101 . In  FIG. 4 , the fixture  104  is not shown. In the example of  FIG. 4 , the first proximity sensor  114  is provided in the vicinity of the main body  102  along the circumferential direction of the shaft  133  (along the space  105 ). In addition, at least one second proximity sensor  116  may also be disposed on a side surface of the main body  102 . The side surface is in the radial direction with respect to the shaft  133 . The second proximity sensor  116  has a detection range to the side (radial direction) of the sensor assembly  101 , and detects objects approaching the side surface of the sensor assembly  101 . With this configuration, for example, it is possible to prevent collisions between the suction apparatus  1  and objects approaching the suction apparatus  1 . A plurality of the second proximity sensors  116  may also be arranged along the circumferential direction of the shaft  133 . By disposing the plurality of second proximity sensors  116  along the circumferential direction of the shaft  133 , it is possible to widen a range in which objects around the sensor assembly  101  can be detected. 
       FIG. 5  is a diagram showing a change in the positional relationship between the suction apparatus and an object  61  to be suctioned. In  FIG. 5 , the fixture  104  is not shown. The amount of pressing at the position where the suction portion  112  (pad) is in contact with the object  61  (workpiece) is zero. The amount of pressing indicates a distance by which the suction portion  112  is further pressed against the object  61  from the contact position. 
       FIG. 6  illustrates an example of the result of the measurement of the capacitance value performed by the sensor assembly  101 , related to detection of an object  61  having a low permittivity. An example of an object having a low permittivity is an object made of plastic. In the example of  FIG. 6 , the vertical axis indicates the capacitance value (pF). The horizontal axis indicates the distance (mm) between the suction portion  112  (pad) and an object (workpiece). A distance of 0 mm between the suction portion  112  and the object indicates that the suction portion  112  and the workpiece are in contact with each other. A negative distance between the suction portion  112  and the object indicates that the suction portion  112  is pressed against the object  61 , and the suction portion  112  is deformed. In this example, the first proximity sensor is a capacitive sensor. The capacitance value detected by the first proximity sensor increases, as the suction portion  112  approaches the object  61  from a distant position. 
     A case where the suction portion  112  is a conductive pad that includes a conductive member at a position to be deformed will be described. When the suction portion  112  has come into contact with an object, and the suction portion  112  is further pressed against the object, the electrostatic capacitance detected by the first proximity sensor  114  rapidly increases. This is because the distance between the main body  102  and the deformed suction portion  112  decreases, due to the pressing. In other words, this is because the first proximity sensor  114  and the conductive member of the suction portion  112  approach each other. Therefore, when the suction portion  112  includes a conductive member at a position to be displaced and at least one of the first proximity sensors  114  is a capacitive sensor, contact between the suction portion  112  and an object, and the amount of deformation of the suction portion  112  can be accurately detected, regardless of the permittivity of the object (workpiece). 
     Next, a case where the suction portion  112  is a non-conductive pad will be described. In this case, even if the suction portion  112  comes into contact with an object, and the suction portion  112  is pressed against the object, the electrostatic capacitance detected by the first proximity sensor  114  does not change rapidly. When the suction portion  112  is a non-conductive pad, the influence of the suction portion  112  is relatively small. The capacitance value slightly increases after the contact between the suction portion  112  and the object mainly due to the electrostatic capacitance of the object. 
     Therefore, when the suction portion  112  is a conductive pad, the amount of deformation of the suction portion  112  can be accurately detected, regardless of the permittivity of an object. With this configuration, a control apparatus (not shown) of the suction apparatus can determine whether or not the suction portion  112  is appropriately pressed against the object  61  (whether or not the suction portion  112  is suctioning the object  61  in a correct orientation). Mobile suction apparatus 
     Next, with reference to  FIGS. 7( a ) and 7( b ) , an example of a hardware configuration of the mobile suction apparatus  100  including the suction apparatus according to the present embodiment will be described. 
       FIG. 7  is a block diagram schematically illustrating an example of the configuration of the mobile suction apparatus  100  according to the present embodiment. In the example shown in  FIG. 7 , the mobile suction apparatus  100  according to the present embodiment includes a suction apparatus  1 , a conveyance unit  2 , and a battery  3 . 
     Suction Apparatus 
     The suction apparatus  1  includes a robot arm  11 , a vacuum pump  12 , and an operation control unit (manipulator control unit)  13 . 
     Robot Arm 
     In the example shown in  FIG. 7 , the robot arm  11  includes a manipulator unit  111 , a suction pad  112 , a deformation information obtaining unit (manipulator-speed subtraction command value calculation unit)  113 , and the operation control unit. 
     Manipulator Unit 
     The manipulator unit  111  is driven together with the suction pad  112  of the robot arm  11 , under the control of the operation control unit  13 . The manipulator unit  111  includes, for example, one or more joints. 
     Suction Pad 
     When the suction pad  112  is positioned at the work position by the driving of the manipulator unit  111 , the suction pad  112  performs an operation of gripping an object by suctioning the object with negative pressure corresponding to the amount of driving of the vacuum pump  12 . 
     Deformation Information Obtaining Unit 
     The deformation information obtaining unit  113  obtains information on deformation of the suction pad  112 . The deformation information obtaining unit  113  obtains, for example, data indicating the amount of deformation of the suction pad  112  from the first proximity sensor  114 , and specifies the amount of deformation of the suction pad  112 . A specific example of the amount of deformation will be described later. 
     The deformation information obtaining unit  113  outputs, to the manipulator control unit  13  and the negative pressure control unit  21 , deformation data such as the amount of deformation, the speed of deformation, or the acceleration of deformation of the suction pad  112 .] 
     Abnormality Determination Unit 
     An abnormality determination unit  115  may also determine that the object is stuck to the suction pad  112 , if the amount of deformation of the suction pad  112  after a predetermined period of time has elapsed since the suction pad  112  stopped suctioning the object and has separated the object is greater than or equal to a predetermined amount. In other words, the abnormality determination unit  115  may also determine that the object is stuck to the suction pad  111 , if the amount of deformation of the suction pad  112  after a predetermined period of time has elapsed since the space between the suction pad  112  and the object is no longer in the vacuum state (that is to say, the vacuum is broken) is greater than or equal to the predetermined amount. 
     In this case, the abnormality determination unit  115  may issue an alert or cause the suction pad  112  to perform an operation of dropping the object (placing operation). In this manner, it is possible to prevent a failure of the placement due to the fact that the object does not separate from the suction pad  112  by being stuck to the suction pad  112  after the vacuum breakdown. 
     Vacuum Pump 
     The vacuum pump  12  generates negative pressure in accordance with the amount of driving and provides the negative pressure to the suction pad  112 . Here, an example in which the suction apparatus  1  in the mobile suction apparatus  100  includes the vacuum pump  12  will be described. In the present embodiment, the suction apparatus  1  in the mobile suction apparatus  100  may not include the vacuum pump  12 , and for example the vacuum pump  12  may also be provided outside the suction apparatus  1  and the mobile suction apparatus  100 . Also with this configuration, the negative pressure control unit  21  controls the amount of driving of the vacuum pump  12 , so that the same effects as those in the above-described example can be achieved. 
     Operation Control Unit 
     The operation control unit  13  includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), or the like, and preforms control in response to an information process. The manipulator control unit  13  controls the manipulator unit  111  of the robot arm  11 , based on the manipulator control signal output from the negative pressure control unit  21 . In this manner, the manipulator control unit  13  moves the suction pad  112  using the manipulator unit  111 . Specifically, the manipulator control unit  13  drives the manipulator unit  111  so that the suction pad  112  of the robot arm  11  is located at a work position where the suction pad  112  can suction the object. Also, the manipulator control unit  13  may also operate the manipulator unit  111  so that the angle of the suction pad  112  with respect to the object reaches a predetermined angle, after the suction pad  112  is positioned at the work position. In this manner, the position of the suction pad  112  can be finely adjusted to a more suitable position. In addition, after the suction pad  112  has suctioned the object, the manipulator control unit  13  drives the manipulator unit  111  so that, for example, the suction pad  112  of the robot arm  11  is positioned at the position of a predetermined box (not illustrated) installed on the upper portion of the manipulator control unit  13 . 
     Furthermore, the manipulator control unit  13  may also determine the direction in which the suction pad  112  is moved to suction the object again, based on a plurality of amounts of deformation at a plurality of positions in the suction pad  112 . 
     In the pick-up operation (suction operation) of the object with the suction pad  112 , the mobile suction apparatus  100  measures the positional relationship between the object and the mobile suction apparatus  100  by two-dimensional vision, three-dimensional vision, or the like, and the suction pad  112  performs the pick-up operation of the object, in order to prevent variation in the stop position of the mobile suction apparatus  100  after traveling of the mobile suction apparatus  100 . In this case, there is a risk that an error in picking up the object by the suction pad  112  may occur due to a measurement error in the positional relationship between the object and the mobile suction apparatus  100 . 
     In contrast, with the above-described configuration, even when the suction pad  112  is not in intimate contact with the object, the suction pad  112  can be moved in the direction in which the object is suctioned again. As a result, it is possible to prevent an error of picking up the object with the suction pad  112 . 
     When the amount of deformation of the first portion is larger than the amount of deformation of the second portion among the plurality positions of the suction pad  112 , the manipulator control unit  13  may also move the suction pad  112  to the first portion side (the side opposite to the placement position of the sensor that has detected the smaller amount of deformation) from the second portion, in order to suction the object again. In this manner, it is possible to suitably prevent misalignment of the suction position of the suction pad  112 . As a result, it is possible to prevent an error of picking up the object by the suction pad  112  better. 
     Operation Control Unit 
     The operation control unit  13  may further include a contact point specifying unit  131 . The contact point specifying unit  131  specifies a contact point where the suction pad  112  contacts the object, based on the deformation (amount of deformation, speed of deformation, or acceleration of deformation) of the suction pad  112 . In addition, the contact point specifying unit  131  specifies a contact point where the object contacts the surface on which the object is to be placed, based on the deformation (amount of deformation, speed of deformation, or acceleration of deformation) of the suction pad  112  in a state where the suction pad  112  is suctioning the object. According to the above configuration, even if there is a measurement error in the position and orientation relationship between the object and the mobile suction apparatus  100 , the measurement error can be canceled by the operation control unit  13  causing the manipulator unit  111  to tilt the orientation of the suction portion (suction pad)  112  toward the suction surface side taking the contact point that is specified by the contact point specifying unit  131  as a fulcrum. As a result, it is possible to better prevent an error of picking up the object by the suction portion  112 . 
     Conveyance Unit 
     The conveyance unit (automated guided vehicle)  2  includes a negative pressure control unit (control signal output unit)  21  and an automated guided vehicle  22 . 
     Negative Pressure Control Unit 
     The negative pressure control unit  21  includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), or the like, and preforms control in response to an information process. The negative pressure control unit  21  includes, for example, a programmable logic controller (PLC) or a microcontroller. The negative pressure control unit  21  controls the vacuum pump  12  that generates negative pressure, based on an output signal that is received from the one or more first proximity sensors  114  in the deformation information obtaining unit  113 , and a conveyance state signal that is received from the conveyance control unit  221  in the automated guided vehicle  22 . 
     The negative pressure control unit  21  controls ON and OFF of the vacuum pump  12  based on a signal that is output from the operation control unit  13 . If it is determined from the deformation of the suction pad  112  that the suction pad  112  has sufficiently pressed against the object when picking up the object, for example, the negative pressure control unit  21  turns ON the vacuum pump. Also, when the object is to be placed on the table, if the operation control unit  13  determines that the entire bottom surface of the object is in contact with the surface of the table on which the object is to be placed, the negative pressure control unit  21  turns OFF the vacuum pump. 
     In addition, the negative pressure control unit  21  outputs a manipulator control signal for causing the manipulator control unit  13  to control the manipulator unit  111 . 
     Furthermore, the negative pressure control unit  21  may also include an analog signal output unit  211  that outputs an analog signal as a control signal for the vacuum pump  12 . The analog signal output unit  211  may also perform control to monotonically increase or monotonically decrease the analog signal. In this manner, the amount of driving of the vacuum pump  12  can be changed in a slope shape, so that a rush current can be reduced. In addition, power consumption can be reduced and control can be stabilized. 
     Automated Guided Vehicle 
     In the example of  FIG. 7 , the automated guided vehicle  22  includes a conveyance control unit  221 . The conveyance control unit  221  controls the movement (conveyance) of the mobile suction apparatus  100  by controlling the conveyance of the automated guided vehicle  22 . The conveyance control unit  221  moves, for example, the mobile suction apparatus  100  to a work position where the robot arm  11  can grip the object. Also, when the mobile suction apparatus  100  has already been positioned at the work position, the conveyance control unit  221  does not move the mobile suction apparatus  100 . In addition, the automated guided vehicle  22  transmits a conveyance state signal, which is a signal indicating the conveyance state of the automated guided vehicle  22 , to the negative pressure control unit  21 . 
     Battery 
     The battery  3  controls the units of the mobile suction apparatus  100 , that is to say, the suction apparatus  1  and the conveyance unit  2 , by supplying power to these units of the mobile suction apparatus  100 . 
     In the above example, the mobile suction apparatus  100  is configured to operate with the battery  3 , but there is no limitation to the present embodiment. In the present embodiment, the mobile suction apparatus  100  may also be configured such that power is supplied from the outside of the mobile suction apparatus  100  through a power cord. 
     Controller 
     The controller  5  includes the deformation information obtaining unit  113  that obtains information on the deformation of the suction pad  112 , and the operation control unit  13  that controls the movement of the suction pad  112  in accordance with the deformation of the suction pad  112 . In other words, the operation control unit  13  changes the movement (movement direction, speed, and/or inclination) of the suction pad  112  in accordance with the deformation of the suction pad  112 . 
     The controller  5  further includes an object information obtaining unit  14  that obtains information about an object, and a placement information obtaining unit  15  that obtains information about a table on which the object is to be placed. 
     The controller  5  may be provided in the mobile suction apparatus  100 , or may also be provided separately from the mobile suction apparatus. The controller  5  may also be configured to be capable of communicating with the mobile suction apparatus, and to transmit a control signal for controlling the mobile suction apparatus to the mobile suction apparatus, for example. 
     3. Operation Examples 
     Hereinafter, various operation examples of the suction apparatus  1  according to the present invention will be described. 
     Before describing specific operation examples, the definition of the amount of deformation of the suction pad  112  will be described. 
     Definition of Amount of Deformation of Suction Pad  112   
     Next, the definition of the amount of deformation of the suction pad  112  will be described with reference to  FIGS. 8 and 9 . 
       FIG. 8  is a diagram illustrating the definition of the amount of deformation of the suction pad that is used in the embodiment of the present invention. First, a definition  1  of the amount of deformation of the suction pad  112  will be described with reference to  FIG. 8 . 
     As described above, the suction pad  112  has a substantially conical shape whose lower side (suction surface) Q is open. Here, a plane including a circular end portion of the suction pad  112  that is to be brought into contact with an object is referred to as “suction surface”. Also, the X-axis and the Y-axis extend in two directions perpendicular to each other and parallel to the suction surface of the suction pad when it is not deformed, and the Z-axis is taken in a direction normal to the suction surface of the suction pad when it is not deformed. In the definition  1  of the amount of deformation of the suction pad  112 , the inclination of the suction surface of the suction pad  112  is represented by the amount of rotation Mx about the X-axis and the amount of rotation My about the Y-axis. In the definition  1 , the amount of deformation of the suction pad  112  is represented by Mx, My, and the amount of pressing Z in the Z-axis direction. 
       FIG. 9  is a diagram illustrating the definition of the amount of deformation of the suction pad that is used in the embodiment of the present invention. Next, a definition  2  of the amount of deformation of the suction pad  112  will be described with reference to  FIG. 9 . 
     A vector connecting the center of the suction surface of the suction pad when it is not deformed and the center of the suction surface of the suction pad when it is not deformed is defined as R. In addition, the unit normal vector of the suction surface of the suction pad when it is not deformed is defined as N. In the definition  2 , the projection of the vector N onto the X-axis is denoted by ex, the projection of the vector N onto the Y-axis is denoted by ey, and the projection of the vector R onto the Z-axis is denoted by ez. In other words, in the definition  2 , the X-axis component of the vector N is ex, the Y-axis component of the vector N is ey, and the Z-axis component of the vector R is ez. In the definition  2 , the amount of deformation of the suction pad  112  is represented by {ex, ey, ez}. 
     As for the amount of deformation of the suction pad  112 , equivalent amount of information can be obtained by the definition  1  and the definition  2 , but the definition  2  is used in the following description. 
     Hereinafter, operations such as picking up and placing of a workpiece W (an object W to be conveyed, an object  61 ) by the mobile suction apparatus  100  will be described with reference to  FIGS. 11 to 13 . 
     Operation Example 1 
       FIG. 11  is a flowchart showing the operation of the mobile suction apparatus  100  in the embodiment of the present invention. First, with reference to  FIG. 11 , an operation example in which the suction pad  112  suctions a workpiece W and picks up the workpiece W will be described.
     Step S 10     

     First, in step S 10 , the operation control unit  13  causes the suction pad  112  to approach the workpiece W by lowering the suction pad  112  in the vertical direction.
     Step S 12     

     Next, in step S 12 , the operation control unit  13  determines whether or not at least a part of the suction pad  112  has come in contact with the workpiece W. When the suction pad  112  has come into contact with the workpiece W, the suction pad  112  is inclined in the X and Y directions, and the amount of inclination of the suction pad  112  represented by the absolute value of the vector (ex, ey) exceeds a threshold value ε 1  or the amount of pressing ez in the Z-axis direction exceeds a threshold value ε 2 . Accordingly, the following expression is satisfied: 
       |(ex, ey)|ε1, or ez&gt;ε2
 
     Therefore, more specifically, in this step, the operation control unit  13  determines that the suction pad  112  has come into contact with the workpiece W if the above expression is satisfied, and otherwise determines that the suction pad  112  has not come into contact with the workpiece W. 
     When the operation control unit  13  determines that the suction pad  112  has come into contact with the workpiece W (YES in step S 12 ), the process proceeds to step S 14 . 
     If the operation control unit  13  does not determine that the suction pad  112  has not come into contact with the workpiece W (NO in step S 12 ), the process returns to step S 10  and the operation control unit  13  continues the approach of the suction pad  112  to the workpiece W.
     Step S 14     

     Next, in step S 14 , the operation control unit  13  determines whether or not the suction pad  112  and the workpiece W are entirely in contact with each other. When the suction pad  112  is entirely in contact with the workpiece W, the inclination of the suction pad  112  is eliminated, so that the following expression is satisfied. 
       |(ex, ey)|&lt;ε1
 
     Therefore, in this step, the operation control unit  13  determines that the suction surface of the suction pad  112  is entirely in contact with the workpiece W if the above expression is satisfied, and otherwise determines that the suction surface of the suction pad  112  is not entirely in contact with the workpiece W. 
     If the operation control unit  13  determines that the suction surface of the suction pad  112  and the workpiece W are entirely in contact with each other (YES in step S 14 ), the operation control unit  13  completes the control of the inclination of the suction pad  112  and shifts to the control of the amount of pressing described later. 
     If the operation control unit  13  does not determine that the suction surface of the suction pad  112  and the workpiece W are entirely in contact with each other (NO in step S 14 ), the process proceeds to step S 16 .
     Step S 16     

     In step S 16 , the contact point specifying unit  131  specifies the position of the contact point between the suction pad  112  and the workpiece W, based on the deformation of the suction pad  112 . 
       FIG. 10( a )  is a side view of the suction pad  112 , and  FIG. 10( b )  is a top view of the suction pad  112 . Here, with reference to  FIG. 10 , a process of specifying the position of the contact point between the suction pad  112  and the workpiece performed by the contact point specifying unit  131  will be described. Letting an angle formed by a projection of the inclination (vector N) of the suction pad  112  onto the XY plane and the X-axis be  8 ,  8  is obtained from the following expression. 
       θ=arctan( ey/ex )
 
     The contact point specifying unit  131  specifies a contact point between the suction pad  112  and the workpiece W based on θ. 
     Once the contact point is specified, the process proceeds to step S 18 .
     Step S 18     

     In step S 18 , the operation control unit  13  changes the inclination of the suction pad  112  while maintaining the contact between the suction pad  112  and the workpiece W at the specified contact point. That is to say, the operation control unit  13  changes the inclination of the suction pad  112  to reduce the angle between the suction surface of the suction pad  112  and the surface to be suctioned of the workpiece W. Here, the operation control unit  13  obtains, by the following process, an operation command of the manipulator unit  111  in a case where the inclination of the suction pad  112  is changed to align the suction surface of the suction pad  112  with the surface to be suctioned of the workpiece W while maintaining the contact at the contact point. 
     The suction pad  112  is attachable to and detachable from the robot arm. The operation control unit  13  calculates a command speed (Pv) and a command angular velocity (φω) for controlling the position and the angle (orientation) of the conveyance hand, which is the base of the suction pad  112 , as a combination (simple sum) of the following two command values. The command angular velocity (φω) is a change speed of the angle of the conveyance hand.
     1. A command speed Pv (more specifically, a command speed vector) for maintaining the contact between the suction pad  112  and the workpiece W at the contact point.   

         Pv =( Pvr−Gv·ez ) h    
     Here, Pyr is the target speed of the suction pad  112 , Gv is a constant gain, ez is the Z-axis component of the normal vector R representing the inclination of the suction pad  112 , and h is the direction vector of the hand orientation (φ). Also, “−” represents multiplication.
     2. Command speed (Pv) and command angular velocity (φω) for rotating suction pad  112  taking contact point as fulcrum.   

     The contact point is set for an extended hand, and the position and the orientation of the contact point is set as {Pe, φe}. Because ex and ey are very small in step S 18 , it is assumed that φe=φ. {Pe, φe} is expressed as follows using the pad installation position offset (Po), the pad radius (Pr), θ that is obtained in step S 16 , and the original hand position/orientation {P, φ} shown in  FIG. 10 . 
       { Pe, φe}=FK ({ P, φ}, {Po, Pr , θ})
 
     Here, Pe is the center of rotation, Po is the offset of the suction pad installation position (the distance between the center of the suction surface of the suction pad  112  and the position of the conveyance hand), and Pr is the radius of the suction pad  112 . FK is a kinematics function for obtaining {Pe, φe} from {P, φ}. The inverse kinematics function IK corresponding to FK exists, and is set as follows. 
       { P, φ}=IK ({ Pe, φe}, {Po, Pr , θ})
 
     Assuming that Pe is the rotation center, and a command that gives rotation on a plane that passes through Pe and the central axis of the suction pad  112  is {Pev, φev}, the operation control unit  13  determines {Pv, φω} using the above IK or Jacobian derived from the IK. This set is defined as a command speed and a command angular velocity. 
     As described above, the operation control unit  13  changes the inclination of the suction pad  112  in accordance with the obtained command speed. Thereafter, the process proceeds to step S 20 .
     Step S 20     

     In step S 20 , the operation control unit  13  determines whether or not the suction pad  112  and the workpiece W are entirely in contact with each other. More specifically, the operation control unit  13  performs the determination through the same process as that in step S 14  described above. If the operation control unit  13  determines that the suction surface of the suction pad  112  and the workpiece W are entirely in contact with each other (YES in step S 20 ), the operation control unit  13  completes the control of the inclination of the suction pad  112  and shifts to the control of the amount of pressing. If the operation control unit  13  does not determine that the suction surface of the suction pad  112  and the workpiece W are entirely in contact with each other (NO in step S 20 ), the process returns to step S 18 , and the operation control unit  13  continues to control the inclination of the suction pad  112 . 
     According to the above operation example, after the suction pad  112  has come into contact with the workpiece W, the operation control unit  13  specifies the position of the contact point and the inclination of the suction pad  112 , and changes the inclination of the suction pad  112  to bring the suction pad  112  into intimate contact with the surface to be suctioned of the workpiece W while maintaining the contact at the contact point. Therefore, the orientation of the suction pad  112  can be accurately corrected, and the workpiece W can be reliably picked up. 
     Operation Example 2 
       FIG. 12  is a flowchart showing the operation of a controller  5  in another embodiment of the present invention. Next, with reference to  FIG. 12 , an operation example in a case where the suction pad  112  presses the workpiece W before suctioning or placing an object will be described.
     Step S 110     

     First, in step S 110 , the operation control unit  13  causes the suction pad  112  to approach the workpiece W by lowering the suction pad  112  in the vertical direction.
     Step S 112     

     Next, in step S 112 , the operation control unit  13  determines whether or not the suction pad  112  has come into contact with the workpiece W, based on the amount of deformation of the suction pad  112 . 
     If the operation control unit  13  determines that the suction pad  112  has come into contact with the workpiece W based on the amount of deformation of the suction pad  112  (YES in step S 112 ), the process proceeds to step S 114 . If the operation control unit  13  does not determine that a part of the suction pad  112  has come into contact with the workpiece W (NO in step S 112 ), the process returns to step S 110  and the operation control unit  13  continues the approach of the suction pad  112  to the workpiece W.
     Step S 114     

     Next, in step S 114 , the operation control unit  13  continues to press the suction pad  112  onto the workpiece W. At this time, the operation control unit  13  may also change the speed of the suction pad  112  in accordance with the deformation of the suction pad  112 . If the amount of deformation (amount of pressing ez) of the suction pad  112  exceeds a first threshold value, the operation control unit  13  may also reduce the speed at which the suction pad  112  is brought closer to the workpiece W. That is to say, the operation control unit  13  may also reduce the speed of the suction pad  112  in step S 114  with respect to the speed of the suction pad  112  in step S 110 . Thereafter, the process proceeds to step S 116 .
     Step S 116     

     In step S 116 , the operation control unit  13  determines whether or not the pressing of the suction pad  112  onto the workpiece W is completed. In this step, letting the threshold value of the amount of pressing ez of the suction pad  112  against the workpiece W be c 2 , the operation control unit  13  determines that the amount of pressing is sufficient if the following expression is satisfied, and otherwise does not determine that the amount of pressing is sufficient. ez&gt;ε2 
     Then, if the operation control unit  13  determines that the pressing of the suction pad  112  onto the workpiece W is completed (YES in step S 116 ), the operation control unit  13  stops the movement of the suction pad  112 . At this time, for example, if the amount of deformation of the suction pad  112  exceeds a second threshold value that is larger than the first threshold value, the operation control unit  13  may also stop the operation of bringing the suction pad  112  closer to the workpiece W. 
     When the pressing control is ended, the operation control unit  13  turns ON the vacuum pump  12  and starts suction of the object. If the deformation information obtaining unit  113  does not determine that the pressing of the suction pad  112  onto the workpiece W is completed (NO in step S 116 ), the process returns to step S 114  to continue the pressing. 
     In the above operation example, the deformation information obtaining unit  113  observes the amount of pressing of the suction pad  112  onto the workpiece W based on the amount of deformation of the suction pad  112 , and determines whether or not to continue the pressing. Therefore, because the amount of pressing ez onto the workpiece W can be kept within a certain range, the suction pad  112  can be pressed onto the workpiece W as appropriate when the workpiece W is picked up or placed. 
     Operation Example 3 
     Next, with reference to  FIG. 13 , an operation example when the suction pad  112  that is gripping the workpiece W places the workpiece W on the table will be described.
     Step S 210     

     First, in step S 210 , the operation control unit  13  causes the suction pad  112  (the workpiece W) to approach the table by lowering the suction pad  112  in the vertical direction.
     Step S 212     

     Next, in step S 212 , the operation control unit  13  determines whether or not a part of the workpiece W that is gripped by the suction pad  112  has come into contact with the table at the contact point. Here, the operation control unit  13  basically performs the same process as the process in step S 12  in the operation example  1  described above. Due to the suction and the weight of the workpiece W, the amount of deformation {ex 0 , ey 0 , ez 0 } of the suction pad  112  before the workpiece W has come into contact with the table is not zero. The operation control unit  13  records the amount of deformation {ex 0 , ey 0 , ez 0 } of the suction pad  112  before the workpiece W has come into contact with the table. Then, if the following expression is satisfied, the operation control unit  13  determines that the workpiece W that is being gripped by the suction pad  112  is in contact with the table, and otherwise determines that the workpiece W is not in contact with the table. 
       |( ex−ex 0 , ey−ey 0)|&gt;ε4, or | ez−ez 0|&gt;ε5
 
     If the operation control unit  13  determines that a part of the workpiece W (the surface that is not suctioned) is in contact with the table (YES in step S 212 ), the process proceeds to step S 214 . If the operation control unit  13  does not determine that a part of workpiece W is in contact with the table (NO in step S 212 ) at the contact point, the process returns to step S 210 , and the operation control unit  13  continues to bring the workpiece W closer to the table.
     Step S 214     

     Next, in step S 214 , the operation control unit  13  determines whether or not the lower surface of the workpiece W and the table are entirely in contact with each other. When the entire lower surface of the workpiece W has come into contact with the table, the inclination of the suction pad  112  and the workpiece W is eliminated, and thus the following expression is satisfied. 
       |( ex−ex 0 , ey−ey 0)|&lt;ε4
 
     Therefore, the operation control unit  13  determines that the entire lower surface of the workpiece W is in contact with the table if the above expression is satisfied, and otherwise determines that the lower surface of the workpiece W is not in contact with the table. 
     If the operation control unit  13  determines that the lower surface of the workpiece W and table are entirely in contact with each other (YES in step S 214 ), the operation control unit  13  completes the inclination control of the suction pad  112 , and shifts to the control of the amount of pressing described above. If the operation control unit  13  does not determine that the workpiece W and the table are entirely in contact with each other (NO in step S 14 ), the process proceeds to step S 216 .
     Step S 216     

     In step S 216 , the contact point specifying unit  131  specifies the position of the contact point where the workpiece W contacts the surface of the table on which the workpiece W is to be placed, based on the deformation of the suction pad  112 . Here, the deformation information obtaining unit  113  performs basically the same process as that in step S 16  in the operation example  1 . However, the deformation information obtaining unit  113  executes the following calculation using the recorded offset {ex 0 , ey 0 , ez 0 }. 
       θ=arctan(( ey−ey 0)/( ex−ex 0))
 
     When the contact point where the workpiece W contacts the surface of the table on which the workpiece W is to be placed is specified by the above process, the process proceeds to step S 218 .
     Step S 218     

     In step S 218 , the operation control unit  13  changes the inclination of the suction pad  112 , while maintaining the contact between the workpiece W and the surface of the table on which the workpiece W is to be placed at the specified contact point (contact side). At this time, the operation control unit  13  changes the inclination of the suction pad  112  to reduce the angle formed by the surface of the suctioned workpiece W, which is not the suctioned surface, and the surface of the table on which the workpiece W is to be placed. 
     Then, the operation control unit  13  basically performs the same process as that in step S 18  in the operation example  1  described above, and obtains a command speed for aligning the suction surface of the suction pad  112  with the surface of the table by changing the inclination of the workpiece W while maintaining the contact at the contact point. 
     However, the operation control unit  13  uses the recorded offset {ex 0 , ey 0 , ez 0 } to perform a calculation by reading the symbols as follows. ez is read as ez-ez 0 . 
     {Pe, φd}: the contact point between the suction pad  112  and the workpiece W is read as the contact point between the workpiece W and the table. {FK({P, φ}, {Po, Pr, θ}) is read as {FK({P, φ}, {Po+Wh/2, Pr+WI/2, θ}) 
     Here, Wh is the height of the workpiece W, WI is the width of the workpiece W, and FK is the same kinematics function as FK in step S 18  in the operation example 1. 
     As a result, the expression in step S 18  in the operation example 1 is read as follows. 
       { P, φ}=IK ({ Pe, φe}, {Po, Pr , θ}) is read as { P, φ}=IK ({ Pe, φe}, {Po+Wh/ 2 , Pr+WI/ 2, θ})
 
     Ik in the above expression is the same kinematics function as IK in step S 18  in the operation example 1. 
     In response to the above process, the operation control unit  13  changes the inclination of the suction pad  112  in accordance with the obtained command speed. Thereafter, the process proceeds to step S 220 .
     Step S 220     

     Next, in step S 220 , the operation control unit  13  determines whether or not the surface of the workpiece W, which is not the suctioned surface, and the surface of the table on which the workpiece W is to be placed are entirely in contact with each other. At this time, the operation control unit  13  performs the same process as that in the step S 214  described above. 
     If the operation control unit  13  determines that the surface of the workpiece W, which is not the suctioned surface, and the surface of the table on which the workpiece W is to be placed are entirely in contact with each other (YES in step S 220 ), the operation control unit  13  completes the inclination control of the suction pad  112 , stops the suction, and releases the workpiece. If the operation control unit  13  does not determine that the surface of the workpiece W, which is not the suctioned surface, and the surface of the table on which the workpiece W is to be placed are entirely in contact with each other (NO in step S 220 ), the process returns to step S 218 , and the operation control unit  13  continues the inclination control of the suction pad  112 . 
     In the above operation example, the operation control unit  13  specifies the position of the contact point and the inclination of the suction pad  112  after the surface of the workpiece W, which is not the suctioned surface, and the surface of the table on which the workpiece W is to be placed have come into contact with each other, and changes the inclination of the suction pad  112  so that the surface of the workpiece W, which is not the suctioned surface, and the surface of the table on which the workpiece W is to be placed are entirely in contact with each other while maintaining the contact at the contact point. In this manner, the orientation of the suction pad  112  can be accurately corrected, and the workpiece W can be placed at an accurate position. Furthermore, it is possible to prevent an impact from being applied to the workpiece W released from the suction pad  112 , or prevent that workpiece W from falling over. 
     Modified Example 1 
       FIG. 14  illustrates an example of a suction apparatus in a modified example 1. In the example of  FIG. 14 , a suction apparatus  202  includes a support  126 , three shafts  133 , three suction portions  112 , a main body  102 , and two fixtures  104 . The three suction portions  112  are provided on the support  126  via the three shafts  133 , respectively. The support  126  is attachable to, for example, a robot arm of the suction apparatus. The main body  102  is fixed to the two shafts  133  with the two fixtures  104 . The main body  102  includes a plurality of the first proximity sensors  114  at positions corresponding to the three suction portions  112 . Due to the suction apparatus  202  including the plurality of suction portions  112 , the suction apparatus  202  can reliably grip an object with sufficient suction force, even when the object is large. In addition, the suction apparatus  202  can individually detect deformation of the plurality of suction portions  112 . 
     Modified Example 2 
       FIG. 15  is a block diagram illustrating an example of a schematic configuration of a suction apparatus according to the present embodiment in a modified example  2 . In the example of  FIG. 15 , a suction apparatus  10  includes a suction pad  112 , an image capturing apparatus  121 , a manipulator unit  111 , an image processing unit  119 , a manipulator control unit  13 , and a manipulator-speed subtraction command value calculation unit  113 . The image processing unit  119  includes an image obtaining unit  120 , a feature point specifying unit  123 , and a deformation amount specifying unit  124 . The manipulator-speed subtraction command value calculation unit  113  includes a deformation amount change speed calculation unit  36  and a constant gain multiplication unit  37 . The deformation amount change speed calculation unit  36  may also be included in the image processing unit  119 , not in the manipulator speed subtraction command value calculation unit  113 . 
     The image capturing apparatus  121  captures an image of the suction pad  112 . The image data may be monochrome image data, or may also be color image data. 
     The image obtaining unit  120  obtains image data captured by the image capturing apparatus  121 . Then, the image obtaining unit  120  inputs the obtained imaged data to the feature point specifying unit  123 . 
     The feature point specifying unit  123  specifies the feature point included in the image data that is received from the image obtaining unit  120 . Then, the feature point specifying unit  123  outputs, to the deformation amount specifying unit  124 , the coordinate values of the feature points in the image coordinate system. The feature point specifying unit  123  also specifies the coordinates (a plurality of coordinates) of the fixed portions  117 , which are not deformed, of the suction pad  112 , as the reference coordinates. The displacement of the respective feature points can be obtained, based on the coordinates of the feature points relative to the reference coordinates. 
     The deformation amount specifying unit  124  specifies the amounts of deformation of the plurality of portions of the suction pad  112  (that is to say, the amount of deformation of the suction pad), based on the feature points (coordinate values) and the coordinates of the fixed portions that are output from the feature point specifying unit  123 . 
     The manipulator control unit  13  determines the operation of the manipulator unit  111 , based on the amount of deformation that is specified by the deformation amount specifying unit  124 . Then, the manipulator control unit  13  instructs the manipulator unit  111  to perform the determined operation. 
     The manipulator unit  111  is driven together with the suction pad  112  in the robot arm  11 , based on the instruction from the manipulator control unit  13 . 
     The deformation amount change speed calculation unit  36  calculates the change speed of the amount of deformation, by time-differentiating the amount of deformation that is specified by the deformation amount specifying unit  124 . Then, the deformation amount change speed calculation unit  36  outputs the change speed of the amount of deformation to the constant gain multiplication unit  37 . 
     The constant gain multiplication unit  37  calculates a deceleration value, by multiplying the change speed of the amount of deformation (the angular velocity of the suction surface of the suction pad, for example), which is calculated by the deformation amount change speed calculation unit  36 , by a constant. The constant gain multiplication unit  37  outputs the calculated deceleration value to the manipulator control unit  13 . 
     The manipulator control unit (operation control unit)  13  stores a target moving speed of the suction pad  112  for conveying the object. The manipulator control unit  13  obtains the command speed, by subtracting the deceleration value from the target moving speed. The manipulator control unit  13  controls the manipulator unit  111  to move the hand (suction pad  112 ) of the manipulator at the command speed. By changing the speed of the hand of the robot arm to reduce the change speed of the amount of deformation of the suction pad  112 , vibration of the suction pad  112  (vibration of the object) can be reduced. 
     Similarly, the manipulator control unit  13  may also change the inclination of the suction pad  112  to decrease the change speed of the amount of deformation, based on the change speed of the amount of deformation. By changing the inclination of the suction pad  112 , the vibration of the suction pad  112  can be controlled. In addition, by utilizing the inclination of the suction pad  112  for vibration damping control, the positioning time at the time of stopping conveyance can be minimized, and the conveyance processing time (conveyance tact time) can be shortened. 
       FIG. 16  is a flowchart showing an example of a flow of a process performed by a suction apparatus according to the present embodiment in the modified example  2 .  FIG. 17  is a schematic diagram showing an example of the flow of the process performed by the suction apparatus according to the present embodiment in the modified example 2. 
     In step S 201 , the manipulator control unit  13  brings the suction pad  112  closer to the object  61 . The example of  FIG. 17( a )  shows the process in step S 201 . Next, in step S 202 , the manipulator control unit  13  determines whether or not the suction pad  112  is in contact with the object  61 . Whether or not the suction pad  112  is in contact with the object  61  can be determined by the amount of deformation of a variable portion  118  in the suction pad  112 . If the amount of deformation is larger than or equal to a threshold value, the manipulator control unit  13  determines that the suction pad  112  is in contact with the object  61 . If the manipulator control unit  13  determines that the suction pad  112  is in contact with the object  61  (YES in step S 202 ), the manipulator control unit  13  causes the suction pad  112  to suction the object  61  (step S 203 ). The example of  FIG. 17( b )  shows the process in step S 203 . If the manipulator control unit  13  determines that the suction pad  112  is not in contact with the object  61  (NO in step S 202 ), the manipulator control unit  13  executes the processes of steps S 201  and S 202  again. 
     In step S 204 , the manipulator control unit  13  causes the manipulator unit  111  to lift the object  61 . The example of  FIG. 17( c )  shows the process in step S 204 . Next, in step S 205 , the manipulator control unit  13  determines whether or not the lifting of the object  61  has succeeded. Whether or not the object  61  has been successfully lifted can be determined by the amount of deformation of the variable portion  118  of the suction pad  112 . If the amount of deformation is larger than or equal to another threshold value, the manipulator control unit  13  determines that the lifting of the object  61  has succeeded. If the manipulator control unit  13  determines that the lifting of the object  61  has succeeded (YES in step S 205 ), the manipulator control unit  13  conveys the object  61  to the target position (step S 206 ). The example of  FIG. 17( d )  shows the process in step S 206 . If the manipulator control unit  13  determines that the lifting of the object  61  has failed (NO in step S 205 ), the manipulator control unit  13  executes the processes of steps S 204  and S 205  again. 
     In step S 207 , the manipulator control unit  13  determines whether or not vibration occurs in the suction pad  112  that is conveying the object  61 . If the change speed of the amount of deformation of the suction pad  112  is larger than or equal to still another threshold value, the manipulator control unit  13  determines that the vibration is occurring in the suction pad  112  that is conveying the object  61 . If the manipulator control unit  13  determines that the vibration is not occurring in the suction pad  112  that is conveying the object  61  (YES in step S 207 ), the manipulator control unit  13  conveys the object  61  to the target position without changing the inclination of the object  61  (step S 208 ). If the manipulator control unit  13  determines that vibration is occurring in the suction pad  112  that is conveying the object  61  (YES in step S 207 ), the manipulator control unit  13  controls the inclination of the suction pad  112  (step S 212 ). Then, the manipulator control unit  13  executes the process of step S 207  again. 
     In step S 209 , the manipulator control unit  13  causes the manipulator unit  111  to lower the object  61  to the target position. The example of  FIG. 17( e )  shows the process in step S 209 . Next, in step S 210 , the manipulator control unit  13  determines whether or not the object  61  has come into contact with the target position. Whether or not the object  61  has come into contact with the target position can be determined by the amount of deformation of the variable portion  118  of the suction pad  112 . If the amount of deformation is larger than or equal to still another threshold value, the manipulator control unit  13  determines that the object  61  has come into contact with the target position. If the manipulator control unit  13  determines that the object  61  has come into contact with the target position (YES in step S 210 ), the manipulator control unit  13  releases the suction of the object  61  by the suction pad  112  (step S 211 ). The example of  FIG. 17( f )  shows a case where the determination in step S 210  is YES. If the manipulator control unit  13  determines that the object  61  has not come into contact with the target position (NO in step S 210 ), the manipulator control unit  13  executes the processes of steps S 209  and S 210  again. 
     The present invention is not limited to the above-described embodiments and modified examples, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention. 
     INDEX TO THE REFERENCE NUMERALS 
     
         
         
           
               1 ,  10 ,  202  Suction apparatus 
               2  Conveyance unit 
               3  Battery 
               5  Controller 
               11  Robot arm 
               12 Vacuum pump 
               13  Operation control unit 
               14  Object information obtaining unit 
               15  Placement information obtaining unit 
               21  Negative pressure control unit 
               22 Automated guided vehicle 
               36  Deformation amount change speed calculation unit 
               37  Constant gain multiplication unit 
               61  Object (workpiece) 
               100  Mobile suction apparatus 
               101  Sensor assembly 
               102  Main body 
               104  Fixture 
               105  Space 
               111  Manipulator unit 
               112  Suction portion (suction pad) 
               113  Manipulator-speed subtraction command value calculation unit (deformation information obtaining unit) 
               114  First proximity sensor 
               115  Abnormality determination unit 
               119  Image processing unit 
               120  Image obtaining unit 
               121  Image capturing apparatus 
               123  Feature point specifying unit 
               124  Deformation amount specifying unit 
               126  Support 
               131  Contact point specifying unit 
               133  Shaft 
               134  Tube 
               141  Fixed portion 
               142  Support portion 
               151  Sensor wiring 
               211  Analog signal output unit 
               221  Conveyance control unit