Patent Publication Number: US-2021186306-A1

Title: Manipulator system, and control method of manipulator system

Description:
This application is a continuation application based on a PCT International Application No. PCT/JP2018/033220, filed on Sep. 7, 2018. The content of the PCT International Application is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a manipulator system such as an endoscope system, and a control method of a manipulator system. 
     BACKGROUND ART 
     Conventionally, a manipulator system such as an endoscope system and the like, wherein an operation of a bending portion of the endoscope may be switched between an electrical operation and a manual operation, is utilized. According to such a manipulator system, it is possible to perform an automatic operation of the bending portion of the endoscope by the electrical operation and an electrical assistance and the like by the manual operation of an operator. 
     An endoscope apparatus having a clutch mechanism configured to switch the operation of the bending portion between the electrical operation and the manual operation is disclosed in Japanese Unexamined Patent Application, First Publication No. H6-189897. According to the endoscope apparatus disclosed in Japanese Unexamined Patent Application, First Publication No. H6-189897, when the electrical operation is switched to the manual operation by the clutch mechanism and the transmission of an electrical driving force to the bending portion is canceled, a regulation operation for preventing the bending portion from sharply restoring is temporarily performed if a bending angle of the bending portion is large. 
     SUMMARY 
     According to an aspect of the present disclosure, a manipulator system has an elongated portion having a bending portion and a wire configured to bend the bending portion; an operation portion configured to generate a first force for pulling the wire by an operator; a motor configured to generate a second force for pulling the wire; a clutch mechanism configured to switch a pulling force to pull the wire to at least one of the first force or the second force; a grasping-state detector configured to determine a grasping state of the operation portion by the operator; and a controller configured to control the motor and the clutch mechanism, wherein the controller is configured to obtain the grasping state from the grasping-state detector, generate a control signal for controlling the clutch mechanism according to the obtained grasping state, and transmit the control signal to the clutch mechanism. 
     According to another aspect of the present disclosure, a manipulator system has an elongated portion having a bending portion and a wire configured to bend the bending portion; an operation portion configured to generate a first force for pulling the wire by an operator; a motor configured to generate a second force for pulling the wire; a switching mechanism configured to switch a pulling force to pull the wire between at least one of the first force or the second force; and a controller configured to control the motor and the switching mechanism, wherein the controller is configured to determine possibility of switching the second force to the first force, and allow the switching when the switching is determined to be possible. 
     According to a further aspect of the present disclosure, a method for controlling an endoscope system, wherein the endoscope system is configured to be switchable between a first mode in which an bending portion of an endoscope is bent due to a driving force of a motor and a second mode in which the bending portion of the endoscope is bent by a manual operation of an operation portion, the method includes determining possibility of switching the first mode to the second mode, and allowing the switching when the switching is determined to be possible. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view showing a whole configuration of an endoscope system according to the first embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view showing a bending portion of the endoscope system. 
         FIG. 3  is a schematic diagram showing an insertion portion, an operation portion, and a controller of the endoscope system. 
         FIG. 4  is a view showing a configuration a control portion of the endoscope system. 
         FIG. 5  is a flow chart showing the control by the control portion when an operation mode is switched from an electrical operation to a manual operation in the endoscope system. 
         FIG. 6  is a flow chart showing the control of the control portion during the manual operation mode. 
         FIG. 7  is a flow chart showing a modification example of the control by the control portion shown in  FIG. 5 . 
         FIG. 8  is a schematic diagram showing an insertion portion, an operation portion, and a controller of an endoscope system according to a second embodiment of the present disclosure. 
         FIG. 9  is a flow chart showing the control by the control portion when the operation mode is switched from the electrical operation mode to the manual operation mode in the endoscope system. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     First Embodiment 
     A first embodiment of the present disclosure will be described with reference from  FIG. 1  to  FIG. 6 . 
       FIG. 1  is a view showing a whole configuration of an endoscope system  100  according to the present embodiment. 
     As shown in  FIG. 1 , the endoscope system (manipulator system)  100  has an insertion portion  2 , an operation portion  3 , a universal cable  4 , and a main body  8 . 
     The insertion portion (elongated portion)  2  is an elongated member to be inserted into an observation target site. A distal end portion  5 , a bending portion  6 , and a flexible tube portion  7  is provided continuously in a sequence from a distal end side of the insertion portion  2 . 
     The distal end portion  5  has an illumination optical system (not shown) having a light guide and an imaging portion having an imaging device (not shown) built in the distal end portion  5 . The bending portion  6  is configured to be freely bendable toward an upward direction and a downward direction, or left and right. The flexible tube portion  7  is a tube-shaped member being elongated and flexible. 
       FIG. 2  is a cross-sectional view of the bending portion  6 . 
     Two wires  15   a ,  15   b  configured to bend the bending portion  6 , an imaging cable  16  being connected to the imaging portion, a treatment device channel tube  17 , two light guide fiber bundles  18 , an air-and-water supply tube  19  and the like are inserted through the bending portion  6  along a longitudinal axis  2   a  of the insertion portion  2 . 
     The wires  15   a ,  15   b  are corresponding to the two bending directions of the upward direction and the downward direction, or left and right. Distal ends of the two wires  15   a ,  15   b  are connected to the distal end portion  5 . The two wires  15   a ,  15   b  are inserted through the distal end portion  5 , the bending portion  6 , and the flexible tube portion  7  along the longitudinal axis  2   a  of the insertion portion  2  and extend to the operation portion  3  disposed at a proximal end side of the flexible tube portion  7 . 
     The operation portion  3  has an operation knob (operation input portion)  10 , various switches  11 , an air-and-water supply button  12 , a suction button  13 , a treatment device insertion port  14  and the like are provided on an external circumferential portion of the operation portion  3 . The various switches  11  refer to operation-mode-switching button  11   a  and the like. An angle lock configured to lock the operation knob  10  is also disposed in the operation portion  3 . 
     The bending portion  6  may be configured to be freely bendable in four directions, the upward direction, the downward direction, left and right. In this case, four wires  15  are provided corresponding to the bending directions of the upward direction, the downward direction, left and right, and the operation knobs  10  is configured to have a upward-downward bending knob and a left-right bending knob for example. 
       FIG. 3  is a schematic view showing the insertion portion  2 , the operation portion  3  and the main body  8 . 
     The operation portion  3  has a bending operation portion  30  configured to operate the bending portion  6  therein. The bending operation portion  30  has a wire traction portion  31 , an electrical driving portion  32 , a clutch mechanism  33 , and a grasping-detection portion  34 . 
     The wire traction portion  31  is configured to pull the wires  15   a ,  15   b  extending from the flexible tube portion  7 . The wire traction portion  31  has a traction pulley  31   a  configured to pull the wires  15   a ,  15   b , a first shaft member  31   b  supporting the pulley  31   a  so as to be rotatable, and a potentiometer  31   c  configured to determine a rotation angle of the pulley  31   a.    
     In the following description, the direction along the longitudinal axis of the insertion portion  2  is referred to a Z-axis direction, the axial direction of the first shaft member  31   b  is referred to a Y-axis direction, and a direction orthogonal to the Z-axis direction and the Y-axis direction is referred to an X-axis. 
     The pulley  31   a  is a disc-shaped member rotating around the first shaft member  31   b  as a rotation center. When the pulley  31   a  rotates, the pulley  31   a  pulls either of the wires  15   a ,  15   b  whose proximal ends are attached to the external circumference of the pulley  31   a . A wire formed by connecting the proximal ends of the two wires  15   a ,  15   b  may be hooked to the external circumference of the pulley  31   a . In the following description, a state of the pulley  31   a  in which distances from the pulley  31   a  to the proximal ends of the two wires  15   a ,  15   b  are the same with each other is defined as an “initial state” of the pulley  31   a.    
     The first shaft member  31   b  is a rod-shaped member as the rotation center O of the pulley  31   a . An end portion of the first shaft member  31   b  is connected to the operation knob  10 . The other end portion of the first shaft member  31   b  is connected to the clutch mechanism  33  by penetrating the pulley  31   a.    
     The potentiometer  31   c  is configured to determine the rotation angle of the pulley  31   a . The rotation angle of the pulley  31   a  in the initial state is defined as “zero”. The potentiometer  31   c  may be suitably selected from the well-known potentiometers that can determine angles. The determined rotation angle is output to the main body  8 . 
     The operation knob (operation input portion)  10  is an input portion of a force (first force) for the operator to input a force (first force) to rotate the pulley  31   a  so as to pull the wires  15   a ,  15   b . The operation knob  10  is connected to the first shaft member  31   b , and the first force is transmitted to the pulley  31   a  via the first shaft member  31   b . The operator may rotate the first shaft member  31   b  and the pulley  31   a  by rotating the operation knob  10  around the Z-axis as the rotation center. 
     The operation knob (operation input portion)  10  is biased such that the pulley  31   a  returns to the initial position if there is no operation input from the operator. Accordingly, when the operator takes hands off from the operation knob  10 , the pulley  31   a  returns to the initial state and the bending portion  6  enters a “straight state” in which the bending portion  6  is not bent. 
     The electrical driving portion  32  is configured to generate a force (second force) for rotating the pulley  31   a  so as to pull the wires  15   a ,  15   b  by the electric power. The electrical driving portion  32  has a motor  32   a , a first gear  32   b  connected to a rotation shaft of the motor  32   a , a second gear  32   c  engaged with the first gear  32   b , and a second shaft member  32   d  being the rotation axis of the second gear  32   c . The second shaft member  32   d  is connected to the clutch mechanism  33 . 
     The clutch mechanism  33  has a clutch configured to switch whether to transmit the second force to the first shaft member  31   b . The clutch mechanism  33  is configured to switch whether to connect the first shaft member  31   b  and the second shaft member  32   d . The switching by the clutch mechanism  33  may be an electromagnetic type or a mechanical type. 
     In a case in which the connection between the first shaft member  31   b  and the second shaft member  32   d  is canceled (the case in which the clutch is disengaged), the second force cannot be transmitted to the first shaft member  31   b . The first shaft member  31   b  is rotated only by the first force. In other words, the wires  15   a ,  15   b  are pulled only by the manual operation of the operator. This operation mode is defined as a “manual operation mode”. 
     In a case in which the connection between the first shaft member  31   b  and the second shaft member  32   d  is maintained (the case in which the clutch is engaged), the second force can be transmitted to the first shaft member  31   b . The first shaft member  31   b  is rotated by the second force. That is, the wires  15   a ,  15   b  are pulled due to the electrical operation of the electrical driving portion  32 . This operation mode is defined as an “electrical operation mode”. The first shaft member  31   b  and the operation knob  10  are still connected such that when the first shaft member  31   b  is rotated by the second force, the operation knob  10  also rotates. 
     The switching of the clutch of the clutch mechanism  33  and the driving of the motor  32   a  of the electrical driving portion  32  are controlled by the main body  8  according to operations modes such as the manual operation mode and the electrical operation mode. 
     The grasping-detection portion  34  is configured to detect the grasping state when the operation knob is grasped by the hand of the operator. The grasping-detection portion  34  may be suitably selected from the well-known three-axis torque sensors. The grasping-detection portion  34  is configured to detect the rotation torque around the Z-axis as the rotation center that is input by the operator to the operation knob  10 . The grasping-detection portion  34  may detect the force in the Z-axis direction that is input by the operator to the operation knob  10 . The detected grasping state is output to the main body  8 . 
     The universal cable  4  extends from the lateral portion of the operation portion  3 . An end of the universal cable  4  is connected to the main body  8 . 
     The main body  8  has a control portion  9  configured to control the bending operation portion  30  of the operation portion  3 . 
       FIG. 4  is a configuration view of the control portion  9 . The control portion  9  is a processing device (computer) capable of executing program and having a processor  90 , a memory  91  capable of reading program, a storage  92  capable of storing program and data, and an input-output control portion  93 . The functions of the control portion  9  are realized by the processor executing the program supplied to the control portion  9 . 
     The processor  90  may obtain the input states of the buttons such as the angle lock  20 , the operation-mode-switching buttons  11   a  and the like that are provided in the operation portion  3  via the input-output control portion  93 . The processor  90  obtains the grasping state detected by the grasping-detection portion  34  via the input-output control portion  93 . The processor  90  may control the electrical-driving portion  32  and the clutch mechanism  33  via the input-output control portion  93 . 
     The program by be provided by the “computer-readable recording medium” such as a CD-ROM, a flash memory and the like. The program may be transmitted from the computer having the storage where the program is stored to the endoscope system  100  through the transmission medium or transmission wave in the transmission medium. The “transmission medium” transmitting the program refers to the medium having the information transmission function such as the internet and the like among the networks (communication network) and the telephone line and the like among the communication circuit (communication lines). Furthermore, the program may be a differential file (differential program) which is combined with the program already recorded in the control portion  9  so as to realize the functions of the control portion  9 . 
     The main body  8  has a display portion that is not shown in figures. The display portion is a LED, a display panel and the like. The display portion may display warning messages and the like to the operator by the control of the control portion  9 . 
     The operations of the endoscope system  100  having the above-described configurations will be described by referring to the flow chart shown in  FIG. 5  and  FIG. 6 . 
     [Switching Operation from Electrical Operation Mode to Manual Operation Mode] 
       FIG. 5  is a flow chart regarding the control of the control portion  9  when the operation mode is switched from the electrical operation mode to the manual operation mode. As shown in  FIG. 5 , when the operation mode of the control portion  9  is switched to the electrical operation mode, the control portion  9  starts the control of the electrical operation mode (Step S 10 ). Next, the control portion  9  executes Step S 11 . 
     During Step S 11 , in a case in which the operation mode is not the electrical operation mode, the control portion  9  controls the clutch mechanism  33  so as to connect the first shaft member  31   b  and the second shaft member  32   d  (engage the clutch). The control portion  9  drives the motor  32   a  of the electrical driving portion  32  to electrically control the bending portion  6 . After a predetermined period, the control portion  9  subsequently executes Step S 12 . 
     During Step S 12 , the control portion  9  detects whether the operation-mode-switching button  11   a  is pressed. In a case in which it is detected that the operation-mode-switching button  11   a  is pressed, it is intended that the operator changes the operation mode from the electrical operation mode to the manual operation mode. In this case, the control portion subsequently executes Step S 13 . On the other hand, in a case in which it is not detected that the operation-mode-switching button  11   a  is pressed, the control portion repeatedly executes Step S 11  subsequently. 
     During Step S 13 , the control portion  9  obtains the rotation angles of the pulley  31   a  and the operation knob  10  from the potentiometer  31   c . The control portion  9  may accurately obtain the rotation angles of the pulley  31   a  and the operation knob  10  by the electrical operation. The control portion  9  subsequently executes Step S 14 . 
     During Step S 14 , the control portion  9  determines whether the rotation angle of the operation knob  10  detected in Step S 13  is equal to or larger than a predetermined value (for example, 90 degrees). In other words, the control portion  9  determines whether the second force for rotating the operation knob  10  is equal to or larger than the predetermined value. In a case in which the rotation angle is equal to or larger than the predetermined value, the control portion subsequently executes Step S 15 . In a case in which the rotation angle is not equal to or larger than the predetermined value, even if the clutch of the clutch mechanism  33  is disengaged to cancel the transmission of the second force, the control portion  9  determines that the bending portion  6  does not operate to rapidly approach the straight stage immediately after the disengagement of the clutch. In this case, the control portion  9  subsequently performs Step S 17  so as to switch the operation mode to the manual operation mode. 
     During Step S 15 , the control portion  9  obtains the rotation torque as part of the grasping state output from the grasping-detection portion  34 . Subsequently, the control portion executes Step S 16 . 
     During Step S 16 , the control portion  9  determines whether the rotation torque input to the operation knob  10  by the operator is equivalent to the rotation angle of the operation knob  10  obtained during Step S 13 . That is, it is determined whether the magnitude and vector of the first force determined from the grasping state is equivalent to the magnitude and vector of the second force. In a case in which the rotation torque has an amount equivalent to the rotation angle of the operation knob  10 , even if the clutch of the clutch mechanism  33  is disengaged to cancel the transmission of the second force, the control portion  9  determines that the bending portion  6  does not rapidly operate to enter the straight stage immediately after the disengagement of the clutch. In this case, the control portion subsequently executes Step S 17  to switch the operation mode to the manual operation mode. 
     On the other hand, in the case in which the rotation torque is not equivalent to the rotation angle of the operation knob  10 , in the case when the clutch of the clutch mechanism  33  is disengaged to cancel the transmission of the second force, the control portion  9  determines that the bending portion  6  rapidly operates to enter the straight stage immediately after the disengagement of the clutch. In this case, the control portion  9  does not switch the operation mode to the manual operation mode. The control portion  9  subsequently executes Step S 19 . 
     The corresponding relationship between the rotation torque input to the operation knob  10  and the rotation angle of the operation knob  10  may be obtained by calculation according to the design information or be obtained according to the result of the prior experiment. 
     It is preferable to determine the corresponding relationship between the rotation torque input of the operation knob  10  and the rotation angle of the operation knob  10  by taking the error and the clearance of the knob and the wires into consideration so as to associate them in a certain range. 
     During Step S 19 , the control portion  9  controls the display portion to show the message such as “Impossible to switch the operation mode to the manual operation mode”. In a case in which the display portion is an LED, the control portion  9  lights up the LED. The control portion  9  subsequently executes Steps S 11  again. The operator adjusts the rotation torque input to the operation knob  10  and then presses the operation-mode-switching button  11   a  so as to make another try to switch the operation mode to the manual operation mode. 
     During Step S 17 , the control portion  9  disengages the clutch of the clutch mechanism  33  to switch the operation mode to the manual operation mode and finishes the control processing (Step S 1 ). 
     According to the control processing of the endoscope system  100  described above, by switching the operation mode from the electrical operation mode to the manual operation mode, it is possible to prevent the bending portion  6  from rapidly operating to enter the straight state. 
     [Operation in Manual Operation Mode] 
     Next, the operations of the endoscope system  100  during the manual operation mode will be described. 
       FIG. 6  is a flow chart regarding the control of the control portion  9  during the manual operation mode. As shown in  FIG. 6 , when the operation mode of the control portion  9  is changed to the manual operation mode, the control portion  9  starts the control processing of the manual operation mode (Step S 20 ). The control portion  9  executes Step S 21 . 
     During Step S 21 , in a case in which the operation mode is not the manual operation mode, the control portion  9  controls the clutch mechanism  33  to separate the first shaft member  31   b  and the second shaft member  32   d  (disengage the clutch). The operator uses the operation knob  10  to manually control the bending portion  6 . After a predetermined period, the control portion  9  subsequently executes Step S 22 . 
     During Step S 22 , the control portion  9  obtains the rotation torque and the force along the Z-axis (hereinafter described as “external force”) as part of the grasping state that is output from the grasping-detection portion  34 . The control portion  9  subsequently executes Step S 23 . 
     During Step S 23 , the control portion  9  determines whether the external force input to the operation knob  10  by the operator is equal to or larger than the predetermined amount. In the case in which the external force is equal to or larger than the predetermined amount, the control portion  9  determines that the operator is grasping the operation knob  10 . In this case, the control portion executes Step S 22  again to continue the control in the manual operation mode. 
     On the other hand, in the case in which the external force input to the operation knob  10  by the operator is not equal to or larger than the predetermined amount, the control portion  9  determines that the operator is not grasping the operation knob  10 . In this case, the control portion  9  executes Step S 21  again. 
     During Step S 24 , the control portion  9  obtains the rotation angle of the pulley  31   a  and the operation knob  10  from the potentiometer  31   c . The control portion  9  may accurately obtain the rotation angle of the pulley  31   a  and the operation knob  10  being rotated due to the electrical operation. The control portion subsequently executes Step S 25 . 
     During Step S 25 , the control portion  9  determines whether the rotation angle of the operation knob  10  determined during Step S 24  is equal to or larger than the predetermined amount (for example, 90 degrees). In the case in which the rotation angle is not equal to or larger than the predetermined amount, even if the operator is not grasping the operation knob  10 , the control portion  9  determines that the bending portion  6  does not rapidly operate to approach the straight state. In this case, the control portion  9  executes Step S 21  again to continue the control in the manual operation mode. 
     ON the other hand, in the case in which the rotation angle is equal to or larger than the predetermined amount, since the operator is not grasping the operation knob  10 , the control portion  9  determines that the bending portion  6  would rapidly operate to approach the straight state. The control portion  9  subsequently executes Step S 26 . 
     During Step S 26 , the control portion  9  engages the clutch of the clutch mechanism  33  to start the transmission of the second force, then switches the operation mode to the electrical operation mode and finishes the control processing (Step S 2 ). When the operation mode is switched to the transmission operation mode, the control portion  9  drives the motor  32   a  so as to not to change the rotation angle of the pulley  31   a . According to this control, the bending posture of the bending portion  6  is maintained. 
     According to the control processing of the endoscope system  100  described above, in the case when the operation mode is the manual operation mode, even if the operator takes hands off the operation knob  10 , it is possible to prevent the operation that the operation mode is changed to the electrical operation mode and the bending portion  6  rapidly approaches the straight state. 
     The first embodiment of the present disclosure has been described above in details; however, the specific configuration is not limited to the embodiment, and additions, omissions, substitutions and other changes in the structure are possible without departing from the spirit of the present disclosure. The configuration elements shown in the first embodiment and following modification examples may be suitably combined. 
     First Modification Example 
     For example, in the embodiment described above, the embodiment of the manipulator system is not limited to the endoscope system  100  as described above. The manipulator system may be configured to have a robot arm with the treatment device at the distal end thereof while the electrical operation and the manual operation being switched due to the clutch mechanism. 
     Second Modification Example 
     For example, in the embodiment described above, it is described that the wire traction portion  31  pulls the wire by the pulley  31   a , however, the embodiment of the wire traction portion is not limited thereto. The wire traction portion may pull the wire by a link structure. In this case, the operation input portion may be a lever and the like capable of operating the link structure. 
     Third Modification Example 
     For example, in the embodiment described above, it is described that the control portion  9  obtains the rotation angle of the pulley  31   a  and the operation knob  10  by the potentiometer  31   c , however, the embodiment of the configuration for obtaining the rotation angle is not limited thereto. The control portion  9  may obtain the rotation angle by an encoder or the like besides the potentiometer  31   c.    
     Fourth Modification Example 
     For example, in the embodiment described above, it is disclosed that the control portion  9  detects the grasping state of the operation knob  10  by the three-axis torque sensor, however, the embodiment of the configuration for detecting the grasping state is not limited thereto. The control portion  9  may detect the grasping state by three strain sensors or the like besides the three-axis torque sensor. 
     Fifth Modification Example 
     For example, in the embodiment described above, it is described that during Step S 16 , in the case when the rotation torque is not equivalent to the rotation angle of the operation knob  10 , the control portion does not switch the operation mode to the manual operation mode. However, the embodiment of switching operation from the electrical operation mode to the manual operation mode by the control portion is not limited thereto.  FIG. 7  is a flow chart regarding the control processing of the control portion  9  according to the modification example when the operation mode is switched from the electrical operation mode to the manual operation mode. During Step S 16 , in the case in which the rotation torque is not equivalent to the rotation angle of the operation knob  10 , the control portion  9  subsequently executes Step S 18 . During Step S 18 , the control portion  9  detects whether there is a pressing operation to the angle lock  20 . In the case in which it is detected that the angle lock  20  is pressed, the pulley  31   a  is mechanically fixed so as to not to rotate and the wire  15  does not move (angle lock). In this case, even if the clutch of the clutch mechanism  33  is disengaged to cancel the transmission of the second force, the control portion  9  determines that it is necessary to prevent the operation of the bending portion  6  as rapidly approaching the straight state immediately after the cancellation. In this case, the control portion  19  subsequently executes Step S 17  so as to switch the operation mode to the manual operation mode. 
     Second Embodiment 
     A second embodiment of the present disclosure will be described by referring to  FIG. 8  and  FIG. 9 . In the following description, the common configuration that has been described will be designated with the same reference sign and the duplicated description will be omitted. An endoscope system  100  according to the second embodiment is different from the endoscope system  100  according to the first embodiment in the functional configuration of the main body  8  and the like. 
       FIG. 8  is a schematic view showing the insertion portion  2 , the operation portion  3 , and a main body  8 B of the endoscope system  100 B. 
     The endoscope system  100 B has the insertion portion  2 , the operation portion  3 , the universal cable  4 , and the main body  8 B. 
     The main body  8 B has the control portion  9  and a current sensor  9 B. The current sensor  9 B is configured to determine the current flowing to the motor  32   a  so as to determine the rotation torque as the output of the motor  32   a  according to the current. 
     Operations of the endoscope system  100 B having the above-described configuration will be described by referring to the flow chart shown in  FIG. 9 . 
     [Operation of Switching the Electrical Operation Mode to Manual Operation Mode] 
       FIG. 9  is a flow chart regarding the control processing of the control portion  9  when the operation mode is switched from the electrical operation mode to the manual operation mode. As shown in  FIG. 9 , when the operation mode of the control portion  9  is switched to the electrical operation mode, the control portion  9  starts the control processing of the electrical operation mode (Step S 30 ). The control portion  9  subsequently executes Step S 31 . 
     During Step S 31 , in the case in which the operation mode is not the electrical operation mode, the control portion  9  controls the clutch mechanism  33  to connect the first shaft member  31   b  and the second shaft member  32   d  (engage the clutch). The control portion  9  drives the motor  32   a  of the electrical driving portion  32  so as to control the bending portion  6  by the electrical operation. After a predetermined period, the control portion  9  subsequently executes Step S 32 . 
     During Step S 32 , the control portion  9  detects whether there is a pressing operation to the operation-mode-switching button  11   a . In the case in which it is detected that the operation-mode-switching button  11   a  is pressed, the operator intends to change the operation mode from the electrical operation mode to the manual operation mode. In this case, the control portion subsequently executes Step S 33 . On the other hand, in the case in which it is not detected that the operation-mode-switching button  11   a  is pressed, the control portion  9  executes Step S 31  again. 
     During Step S 33 , the control portion  9  obtains the rotation angle of the pulley  31   a  and the operation knob  10  from the potentiometer  31   c . The control portion  9  may accurately obtain the rotation angle of the pulley  31   a  and the operation knob  10  due to the electrical operation. The control portion  9  subsequently executes Step S 34 . 
     During Step S 34 , the control portion  9  determines whether the rotation angle of the operation knob  10  detected during Step S 33  is equal to or larger than the predetermined amount (for example, 90 degrees). In the case in which the rotation angle is equal to or larger than the predetermined amount, the control portion  9  subsequently executes Step S 35 . In the case in which the rotation angle is not equal to or larger than the predetermined amount, even if the clutch of the clutch mechanism  33  is disengaged to cancel the transmission of the second force, the control portion  9  determines that the bending portion  6  does not rapidly operate to enter the straight stage immediately after the disengagement of the clutch. In this case, the control portion subsequently executes Step S 36  to switch the operation mode to the manual operation mode. 
     During Step S 35 , the control portion  9  determines the rotation torque as the output of the motor  32   a . The control portion  9  controls the current flowing to the motor  32   a  to be smaller so as to make the determined rotation torque to be smaller. The force (second force) for rotating the pulley  31   a  by the electrical driving portion  32  becomes smaller such that the rotation angle of the pulley  31   a  becomes smaller and the pulley  31   a  approaches the initial state. The control portion  9  subsequently executes Step S 33  again. 
     The control portion  9  repeats Step S 33  to Step S 35  such that the rotation angle of the operation knob  10  gradually becomes smaller and the pulley  31  gradually approaches the initial state. As a result, the control processing of the control portion  9  is branched to Step S 36  at Step S 34  to switch the operation mode to the manual operation mode. 
     According to the endoscope system  100 B disclosed in the present embodiment, it is possible to prevent the bending portion  6  from rapidly operating to enter the straight state by switching the operation mode from the electrical operation mode to the manual operation mode. The endoscope system  100 B may be transitioned to the manual operation mode after gradually returning the bending portion in the bent state to the straight state. 
     The first embodiment of the present disclosure has been described above in details; however, the specific configuration is not limited to the embodiment, and additions, omissions, substitutions and other changes in the structure are possible without departing from the spirit of the present disclosure. The configuration elements shown in the first embodiment and following modification examples may be suitably combined. 
     Several embodiments and modification examples of the present disclosure have been described above, however, technical scope of the present disclosure is not limited to the embodiment and the application examples. The present disclosure is not limited to the above-described embodiments and is limited only by the accompanying claims.