Teaching unit for robots

A direct teaching apparatus which allows an operator to perform the direct teaching of a robot in safety. The apparatus includes a force detector and a teaching tool. The tool includes a working tool or handle fixed to the first detector and held by the operator to lead the robot. It also includes a device for computing the position or speed directive based on the force detector data and a motion model. It further includes a device for computing the generation torque of a motor for driving a robot depending on the position or speed directive and a controller to control the generated torque.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a teaching apparatus for teaching data
 with reference to a working point to such as an industrial robot, more
 particularly to a teaching apparatus which is improved in safety.
 2. Discussion of the Background
 As a conventional zeaching method for teaching data of a working point to
 an industrial robot, there is a direct teaching method, as disclosed in
 J.P.A. Gazette 85106/1981, in which a force sensor is provide as a
 teaching tool in a manual operation part of the industrial robot, each
 driving unit for driving an industrial robot is controlled according to
 directives showing positional data of a tip and attitude data of a wrist
 of the robot which are indicated by signals generated by the force sensor
 at the time when an operator operates the manual operation part to lead
 the position of the tip and the attitude of the wrist of the robot, and
 thus the data (lead data) controlling each driving unit are stored in a
 memory.
 Further, in a method disclosed in J.P.A. Gazette 71086/1983, teaching tool
 221 having a built-in force sensor is attached to the tip of robot 211 as
 shown in FIG. 1, and force control is performed corresponding to the force
 or the moment which is applied to teaching tool 221, when operator 214
 directly manipulates teaching tool 221, and thus the position or the speed
 of the robot is controlled for leading a working tool of the robot. When
 performing teaching, operator 214 instructs the start and termination of
 teaching by manipulating many switches provided in teaching tool 221.
 Different from the direct teaching method as above, there is an indirect
 teaching method as shown in FIG. 2, in which operator 214 manipulates
 teaching manipulator 220 provided with manipulation switches for teaching
 the motion of the robot to lead robot 211.
 Conventional examples shown in FIG. 1 and FIG. 2 each shows the same
 example in which cylindrical tube 213 is welded on a flat plate.
 Among the conventional examples shown above, the method disclosed in J.P.A.
 Gazette 85106/1981 has a risk such that, if the operator stumbles during
 teaching and leads the teaching tool with excessive foe or makes the
 teaching tool contact the work or other obstruction, excess force is
 applied to a force detector and then abrupt motion of the robot is caused
 due to the excessive torque thus generated.
 Or, in case the operator is caught between the arms of the robot or between
 the arm and the work while he is leading a teaching tool and the robot is
 generating power in the direction of applying force to the operator
 standing therebetween, it is hard for the operator to escape from this
 state.
 Further, even when the operator detects danger during direct teaching, he
 will be unable to avoid the danger because he has no means at hand to
 suddenly stop the motion of the robot.
 Still further, when the output from the force detector varies due to a
 temperature drift or external force is applied to the force detector, a
 teaching handle is not in a fixed position and there is a danger that a
 robot may move contrary to the operator's intention. Also when a working
 tool makes contact during direct teaching operation with the work or other
 obstruction, there is a danger that the robot may continue to move
 deforming the working tool. Moreover, when the operator performs the
 teaching of a narrow portion of the work, the teaching handle on the
 working tool becomes an obstrution, thereby causing a danger that the
 operator's arm may be grasped by the work, and further that the robot may
 be locked at the time of emergency stop, and in the worst case, the
 operator may be held in a constrained state being unable to escape
 therefrom.
 With the robot shown in FIG. 1, since the operator performs teaching while
 manipulating many switches on the teaching tool for leading the robot, the
 physical/mental fatigue of the operator becomes very large. Further, when
 one teaching tool is commonly used among a plurality of robots, it becomes
 necessary to lay the wiring from the teaching tool to respective robot
 controllers directly thereby requiring a large cost.
 Also as for the robot shown in FIG. 2, since the operator leads the robot
 per each axis or leads in the XYZ direction on the robot coordinate system
 or on the tool coordinate system through manipulation switches on a
 teaching manipulator, it is hard to intuitively lead the position or the
 attitude of the robot or the tool relative to the work, and the large
 physical/mental fatigue of the operator as well as the prolonged teaching
 time are required, causing a disadvantage to the person concerned.
 SUMMARY OF THE INVENTION
 The present invention has been developed in view of the above
 circumstances. A first object of the present invention is to provide a
 direct teaching apparatus which can control the motor generation torque
 within an allowable limit and enables an operator to perform teaching in
 safety by using a simple teaching apparatus, even if the excessive
 manipulation force is applied by the operator to a force detector or even
 if the operator is caught between arms of the robot or between the arm and
 the work.
 Further, a second object of the present invention is to provide an
 apparatus for teaching a robot which can remarkably reduce the
 physical/mental fatigue of the operator by decreasing the number of
 switches on a teaching tool thereby enabling the operator to use both the
 direct and indirect teaching methods, the teaching apparatus being
 concurrently made simple with the reduced wiring.
 Still further, a third object of the present invention is to provide a
 direct teaching apparatus which allows the operator to perform the
 teaching operation in safety even if there is a temperature drift in the
 force detector or attachment omission of a teaching handle, even if a
 working tool makes contact with the work or the teaching is made with
 reference to a narrow portion of the work or even if an emergency stop
 takes place.
 The apparatus for teaching a robot according to the present invention
 comprises a force detector, a teaching tool composed of a working tool or
 an handle which is fixed to said force detector and held by the operator
 for leading the robot, a motion model operation part which serves as a
 means for computing a position or a speed directive based on data of said
 force detector and a motion model, a flexible servo system composed of
 means for computing motor generation torque based on said position data or
 said speed directive and means for controlling said generation torque, and
 means for storing directive data with reference to the position, speed or
 direction.
 When the operator performs direct teaching of a working point according to
 the teaching apparatus structured as above by holding and leading the
 teaching tool and the simple teaching apparatus, the torque generated by a
 driving unit is controlled to a minimum amount required for the motion of
 the arm itself because the apparatus has a function for controlling the
 motor generation torque, and hence, for example, even if excessive force
 by the operator is applied to the force detector, there is no danger that
 the robot may move under the excessive generation torque. Further, even if
 the operator is caught between the arms of the robot or between the arm
 and the work, the force holding the operator is not excessively large so
 that the operator can easily escape by his own force, and accordingly the
 operator can perform the teaching operation in safety. Also, when the
 motor generation torque is controlled, sometimes the robot may move
 without corresponding to the directive data thereby producing a difference
 between the directive data and the detector data; however, since the
 apparatus comprises storage means based on the detector data, the robot
 can move in a playback operation to the working point actually indicated
 by the operator.
 A apparatus for teaching a robot according to another aspect of the present
 invention comprises a force detector, a teaching tool composed of a handle
 which is fixed to the detection terminal of said force detector and held
 and manipulated by the operator, a teaching manipulator in which said
 teaching tool can be housed or attached thereon, a force detector lead
 wire connecting said teaching tool and said teaching manipulator, and
 means for controlling force based on said force detector data.
 This teaching apparatus further comprises means for performing direct
 teaching by separating the teaching tool from the teaching manipulator and
 attaching to a hand or an arm or a working tool of the robot, and means
 for performing the indirect teaching by attaching the teaching tool to the
 teaching manipulator.
 Further, if the above teaching apparatus comprises additional means for
 switching the force control with reference to the manipulation force in
 the direction of translation and rotation, it becomes possible to perform
 teaching of a position and an attitude independently, achieving an
 effective result for the user.
 In case of teaching the working point by using the teaching apparatus
 structured as above, the operator attaches the teaching tool to the hand
 or the arm or the working tool and the like of the robot and leads the
 robot in accordance with the manipulation force applied to the handle of
 the teaching tool and thus performs the teaching of the position and the
 attitude of the working tool according to the direct teaching method, or
 the operator inserts the teaching tool in the Leaching manipulator and
 leads the robot in accordance with the manipulation force applied to the
 handle of the teaching tool and thus performs the teaching of the position
 and the attitude of the working tool according to the indirect teaching
 method. Further, by switching the force control between the manipulation
 force in the translational direction and the manipulation force in the
 rotational direction on the teaching apparatus, it becomes possible to
 perform the teaching of the working tool only for the position or only for
 the attitude in relation to the work.
 An apparatus for teaching a robot according to still another aspect of the
 present invention comprises a force detector, a teaching handle fixed to
 said force detector and held by the operator for leading the robot, a
 motion model operation part serves as a means for computing the position
 or the speed directive based on the data of said force detector and a
 motion model, a position/speed servo system for computing motor generation
 torque based on said position data or said speed directive, and a simple
 teaching apparatus.
 The simple teaching apparatus has input switches for inputting data with
 reference to positions or the like of the robot and means for expressing
 the state such as on-off of the servo power, which are both provided
 thereon.
 Further, an apparatus for teaching a robot according to still another
 aspect of the present invention described above comprises a compliance
 mechanism which is provided between the teaching handle and the tip of the
 robot or between the working tool attached with the teaching handle and
 the tip of the robot, means for changing a signal at the time when said
 compliance mechanism is subjected to a fixed amount of displacement, and
 means for stopping the motion of the robot upon receiving said signal.
 Also, the above teaching apparatus is structured such that, after the robot
 is urgently stopped by the electric brake, mechanical braking operation
 will not be applied to three wrist shafts nor to a shaft which is not
 subject to gravity.
 Further, the above teaching apparatus includes manipulation buttons
 provided on the teaching handle, means for recognizing that the teaching
 handle is attached to the tip of the robot or to the fixed place on the
 working tool, and means for attaching the teaching handle onto said simple
 teaching apparatus.
 Furthermore, the above teaching apparatus is structured such that the
 handle attachment recognition switch can be manipulated by means or a
 remote manipulation jig which is used for manipulation when the teaching
 handle is detached from the robot.
 An apparatus for teaching a robot according to still another aspect of the
 present invention comprises a direct teaching apparatus having a teaching
 handle disposed on the tip of the robot and a force sensor interposed
 therebetween detects the force applied to said teaching handle held by the
 operator by means of said force sensor, and moves the robot arm in the
 direction of the detected force or teaching the position to which the
 robot is to be moved, wherein
 the teaching tool is attached through the compliance mechanism to the tip
 of the robot and the teaching handle is attached to the tool through the
 force sensor.
 Also in the above direct teaching apparatus, the force sensor and the
 teaching handle are integrated as a unit which is detachable at the time
 of playback operation, and the unit detached including the force sensor
 and the teaching handle is held during the playback operation at the
 position provided on the robot arm or on the controller.
 The compliance mechanism of the present invention is a mechanism which
 produces a buffering effect such as that of a RCC (Remote Center
 Compliance) mechanism or a floating mechanism.
 By attaching the tool through the compliance mechanism as described above,
 the flexible motion of the tool portion becomes realized to prevent the
 damage of the tool and the force sensor at the time of collision, and
 further when some object strikes the teaching handle or the tool or the
 instructing operator falls carrying the teaching handle, the compliance
 mechanism absorbs the impact and prevents an abnormal motion of the robot
 which may be caused by the excessive load.
 Further, when a part of the instructing operator's body is caught between
 the tool and the robot arm for some reason after the braking action of the
 control board is started, if the resulting coasting distance is short, the
 compliance mechanism absorbs the motion energy of the robot thereby
 preventing an accident of sandwiching the operator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Next, an embodiment of the present invention will be described with
 reference to the drawings.
 FIG. 3 is a block diagram showing a structure of an embodiment of a direct
 teaching apparatus of a robot of the present invention. As shown in FIG.
 3, the present embodiment comprises force detector 21, teaching tool 20
 composed of working tool 22 (or exclusive handle 23) which is fixed to
 said force detector and held by the operator for leading the robot, motion
 model operation part 24 which serves as a means for computing the position
 or the speed directive based on the output data of force detector 21 and a
 motion model, flexible servo system 25 composed of means for computing
 motor generation torque based on said position data or said speed
 directive data and means for controlling said generation torque, and
 storage means 29 for storing directive data with reference to the
 position, speed or direction.
 The motion of the present embodiment will be described below.
 First, a simple teaching apparatus used in the present embodiment for
 direct teaching as an auxiliary tool will be shown in FIG. 4 and described
 in advance.
 Simple teaching apparatus 40 is of approximately palm size and the operator
 manipulates each switch holding it by one hand (since the other hand of
 the operator must hold a later described teaching tool, apparatus 40 must
 be held by one hand). Here, each switch means servo Dower retention switch
 41, emergency stop button 42, input switch 43, memory data editing key 44,
 and further state indication lamp 45 is also included therein.
 Operator 11 shown in FIG. 7 can input the servo power by holding servo
 power retention switch 41 with a fixed level of force. Also, when operator
 11 feels danger during the direct teaching operation, he can stop the
 motion of the robot by releasing the hold of servo power retention switch
 41 or by pushing emergency stop button 42.
 In the present embodiment, the position data of the robot is stored only
 when input switch 43 is pushed. Input switch 43 is pushed every time
 teaching is finished at each teaching point, and thus each position of the
 robot at each push time is stored.
 Memory data editing key 44 is used for performing editing such as addition,
 change or erasing of storage data. By using this key, teaching points can
 be changed with other points.
 State indication lamp 45 is a lamp for indicating that teaching is in
 progress.
 FIG. 5 is a block diagram showing a structure of a control system of the
 present embodiment. A control method of the present embodiment is
 structured such that force detector 22 detects the leading force of
 teaching tool 21 held by the operator, and depending on the detected data,
 motion model operation part 24 computes the position directive on the
 rectangular Cartesian coordinate system which is established according to
 the motion model prepared by using imaginary inertia and viscosity. Motion
 model operation part 24 further inversely transforms the computed position
 directive to the data on a revolute type system to obtain an articulation
 angle directive of each articulation.
 Flexible servo system 25 calculates the motor generation torque based on
 articulation angle directive calculated by motion model operation part 24
 and based on the articulation angle and articulation speed detected by
 articulation angle detector 32 provided on each driving unit or on each
 articulation part of the robot. Here, in torque limiter 26, limit value of
 the torque is set which gives a required minimum value for moving the arm
 of robot 12. By inputting said generation torque to this torque limiter
 26, the generation torque is controlled within a safety range. For
 example, when the operator exerts excessive force on teaching tool 21 and
 the generation torque calculated by torque limiter 26 exceeds the
 predetermined threshold, torque limiter 26 controls the generation torque
 to the minimum value necessary to move the arm of robot 12.
 To the generation torque, which is controlled by torque limiter 26 are
 added, gravity compensation torque which acts on each arm with the value
 calculated by gravity compensator 30 based on the angle of each
 articulation, the distance from the center of gravity of each arm to the
 center of each articulation and the mass of each arm and friction
 compensation torque which acts on a driving part of each articulation with
 the value calculated by friction compensator 31 based on the articulation
 speed of each articulation. Robot 12 is driven by the generation torque
 which is added with his gravity compensation torque and this friction
 compensation torque.
 When the operator lads robot 12 to a working point of working object 14
 (FIG. 7) and pushes input switch 43 (FIG. 4) provided on simple teaching
 apparatus 40, an articulation angle directive is stored in data storage
 29. At the time of playback operation, position control is performed based
 on the articulation angle directive thus stored.
 FIG. 6 is a block diagram showing a structure of a second embodiment of the
 present invention. In the present embodiment, an articulation angle
 detected by articulation angle detector 32 is stored in data storage 29
 and used for playback operation in place of the articulation angle
 directive.
 When torque generation is controlled, sometimes motor generation torque
 becomes short and robot 12 does not operate as directed, thereby producing
 a difference between directive data and detector output data. If directive
 data is stored in data storage 29 (FIG. 5) in this state, robot 12 moves
 in playback operation to a position deviated from the actual teaching
 point.
 In the present embodiment, by providing data storage 29 (FIG. 6) which uses
 the detector data, it is arranged so that the robot can move in playback
 operation to the working point settled at the time when the input switch
 is actually pushed.
 Whether the directive data is stored as in the embodiment shown in FIG. 5
 or the detector data is stored as in the present embodiment can be
 selected according to cares. Further, to meet the above circumstances, a
 selection switch to select either one of the above two may be added on
 simple teaching apparatus 40.
 FIG. 7 and FIG. 8 are perspective views each showing a state of welding
 work in the direct teaching method of the robot of the present invention.
 Operator 11 fixedly attaches teaching tool 21 to the wrist portion or the
 like of robot 12, and then supplies the servo power by holding servo power
 retention switch 41 on simple teaching apparatus 40. Operator 11 performs
 teaching of the working point on working object 14 by holding exclusive
 handle 23 fixed to force detector 22 and leading thereof toward the
 optional direction as shown in FIG. 7, or by holding welding torch 1022
 which serves as working tool 20 fixed to force detector 22 and leading
 robot 12 toward the optional direction as shown in FIG. 8.
 It is to be noted that data from force detector 22, directives from simple
 teaching apparatus 40, and data from articulation angle detector 32
 attached to each driving shaft of robot 12 are all stored in robot
 controller 13, and arithmetic is performed there to issue a directive for
 driving robot 12.
 As described above, according to the direct teaching apparatus of the
 industrial robot of the present invention, the torque generated by the
 driving portion is controlled to the required minimum value for moving the
 arm itself, and hence even if excessive force of the operator is applied
 to the force detector, there is no danger that the robot will move being
 driven by the excessive torque. Further, even if the operator is caught
 between the arms of he robot or between the arm and the work, the force
 catching the operator is not excessively large so that the operator can
 easily escape by his own force, and accordingly the operator can perform
 the teaching operation in safety. Further, since the operator has, in
 addition to the teaching tool, the simple teaching apparatus with a servo
 power retention switch, the operator can stop the motion of the robot
 freely on his own decision.
 Next, a third embodiment of the present invention will be described. A
 direct teaching apparatus of the robot according to the present embodiment
 comprises, as shown in FIG. 9 and FIG. 10, a force detector, teaching tool
 121 composed of a handle which is fixed to the detection terminal of said
 force detector and held and manipulated by the operator, teaching
 manipulator 120 in which said teaching tool 121 can be housed or attached
 thereon, a force detector lead wire connecting said teaching tool 121 and
 said teaching manipulator 120, and means for controlling force based on
 said force detector data.
 This teaching apparatus further comprises means for performing the direct
 teaching by separating teaching tool 121 from teaching manipulator 120 and
 attaching to a hand or an arm or a working tool of robot 111, and means
 for performing the indirect teaching by attaching teaching tool 121 to
 teaching manipulator 120.
 The concrete constitution of the present embodiment will be described
 below. First, a teaching apparatus shown in FIG. 11 will be described.
 In FIG. 11, teaching tool 121 is composed of force detector 122 and handle
 123 fixed to the detection terminal of force detector 122 for being held
 and manipulated by operator 114. Teaching tool 121 is connected with
 teaching manipulator 120 by means of force detector lead wire 124 and can
 be housed or attached on teaching manipulator 120. Also, teaching tool 121
 may be attached to the wrist or the arm or the working tool and the like
 of robot 111 by means of the other end of the force detector. Further, a
 translational/rotational direction change-over switch not shown is
 provided on teaching tool 121 or teaching manipulator 120.
 The present embodiment structured as above will be described with reference
 to FIG. 12 and FIG. 13. The contents of the operation will be described
 below using a welding robot employed particularly for welding a
 cylindrical pipe on a flat plate as an example.
 FIG. 12 shows a state in which teaching of the welding line is performed
 according to the direct teaching method. In this case, operator 114 first
 detaches teaching tool 121 from teaching manipulator 120, draws out a
 force detector lead wire, and fixedly attaches the other and of force
 detector 122 to a portion of the wrist or the arm or welding torch 112 or
 the like of robot 111. Next, operator 114 holds handle 123 (see FIG. 11)
 of teaching tool 121 and by applying force to handle 123 in the arbitrary
 direction, leads robot 111 to teach the working point.
 FIG. 13 shows a stale in which teaching of the welding line is performed
 according to the indirect teaching method. In this case, operator 114
 first fixedly attaches the other end of the force detector of teaching
 tool 121 onto teaching manipulator 120. Then operator 114 holds the handle
 of teaching tool 121 and by applying force to handle 123 in the particular
 direction on teaching manipulator 120, leads robot 111 to teach the
 working point.
 After determining the welding attitude of welding torch 112, by switching
 the translational/rotational direction change-over switch to the
 translational direction, it becomes possible to lead robot 111 only in the
 translational direction without changing the welding attitude of welding
 torch 112. Similarly, after determining the welding position of welding
 torch 112, by switching the translational/rotational direction change-over
 switch to the rotational direction, it becomes possible to change only the
 attitude of robot 111 without changing the welding position of welding
 torch 112. Thus teaching of the welding line of a complicated
 configuration can be performed easily and correctly in a reduced time.
 FIG. 14 is a view showing a structure of a control system of the present
 embodiment. The control system of the present embodiment will be described
 with reference to FIG. 14. (See other figures for symbols not shown in
 this figure).
 Contact force produced at the time when handle 123 of teaching tool 121 was
 forced to contact with work 113, and manipulation force in the
 translational direction and in the rotational direction produced when
 operator 114 holds and manipulates the handle, are detected by force
 detector 122 of teaching tool 121, and the sum of the contact force and
 the manipulation force is transformed by force control system 126 into an
 angle directive for each articulation. Angle directives are inputted to
 position control system 127 to drive robot 111 through amplifier 123.
 Here, for teaching the working point in space, the manipulation force of
 the operator in the translational direction and the rotational direction
 are inputted into force detector 122 by switching translational/rotational
 direction change-over switch 125, force control in the translation
 direction and in the rotational direction are performed corresponding to
 these force thereby leading the robot to teach the working point.
 A role of force translational/rotational direction control change-over
 switch 125 is to fix the position or attitude. For example, if
 manipulation force 125a in the translational direction is selected, the
 rotational direction (attitude) is fixed and hence this mode is selected
 when the position of the work is moved while fixing the attitude. If
 manipulation force 125b in the rotational direction is selected, the
 translational direction (position) is fixed and hence this mode is
 selected when the attitude of the work is changed while fixing the
 position. If manipulation force c is selected, then the manipulator leaves
 both the position and attitude unfixed and hence this mode is selected to
 make both the position and the attitude change. With the selection as
 above, it becomes possible to perform the teaching of the working tool
 only for the position or only for the attitude with reference to the work.
 Enter key 129 sores position/attitude data into storage 130 in the robot
 controller only when the key 129 is pushed, and is provided as a switch on
 the teaching manipulator 120 or handle 123.
 When the operator teaches the working point on the work, said manipulation
 force and the contact force produced when handle 123 makes contact with
 work 113 are detected by force detector 122, and then force control is
 performed corresponding to the sum of both force to lead the robot for
 teaching the working point.
 It is to be noted that it is allowable to dispose translational/rotational
 direction change-over switch 125 behind force detector 122.
 In the present embodiment structured as above, when teaching of the working
 point is performed with the direct teaching method, the operator detaches
 the teaching tool from the teaching manipulator and fixes its to the wrist
 or the arm or the working tool and the like of the robot, and by holding
 and moving the handle of the teaching tool in the optional direction,
 leads the robot in accordance with the manipulation force thereby
 performing the teaching of the position and the attitude of the working
 tool.
 When teaching of the working point is performed with the indirect teaching
 method, the operator attaches the teaching tool to the teaching
 manipulator and by holding and moving the handle of the teaching tool in
 the particular direction, leads the robot in accordance with the
 manipulation force thereby performing the indirect teaching of he position
 and the attitude of the working tool. Further, by switching the force
 control between the manipulation force in the translational direction and
 the manipulation force in the rotational direction on the teaching
 apparatus, it becomes possible to perform teaching of the working tool
 only for the position or only for the attitude with reference to the work.
 Therefore, teaching manipulation becomes simple without requiring any
 skill and the physical/mental fatigue of the operator is considerably
 reduced.
 Further, when one teaching tool is commonly used among a plurality of
 robots, it becomes unnecessary to lay the wiring from the teaching tool to
 respective robot controllers directly, thereby allowing the construction
 of teaching apparatus of a simple structure and of a low cost.
 Next, a fourth embodiment of the present invention will be described. The
 teaching apparatus of the present embodiment comprises, as shown in FIG.
 15, force detector 415, teaching handle 416 fixed to said detector and
 held by the operator for leading the robot, and simple teaching apparatus
 417. On simple teaching apparatus 417, there are provided an input switch
 for inputting data such as the position of the robot and means for showing
 the state of the robot.
 FIG. 16 is a block diagram showing a structure of a control system for
 computing positional data or a speed directive based on the output data of
 force detector 415 and a motion model.
 The control system shown in FIG. 16 comprises motion model operation part
 301, speed/position servo system 302 for computing motor generation torque
 based on said positional data or said speed directive, compliance
 mechanism 310 which produces a buffering effect of such as that of a RCC
 (Remote Center Compliance) mechanism or a floating mechanism being
 provided between teaching handle 416 (FIG. 15) and the tip of the robot or
 a fixed position on the working tool to be used for attaching the teaching
 handle, means 311 for changing a signal at the time when said compliance
 mechanism is subjected to a fixed amount of displacement, and means for
 stopping the motion of the robot upon receiving said signal.
 Also, the above teaching apparatus is structured such that, after the robot
 is urgently stopped by the electric brake, mechanical braking operation
 will not be applied to the three wrist shafts and a shaft on which gravity
 has no effect.
 Further, the above teaching apparatus includes manipulation buttons 306
 provided on teaching handle 416, means 308 disposed between 306 and 307
 for recognizing that teaching handle 416 is attached to the tip of the
 robot or to the fixed place on the working tool, and means 307 for
 attaching the teaching handle onto said simple input unit.
 FIG. 17 shows the state in which the teaching handle is detached from the
 robot to manipulate and also shows a structural mechanism in which a
 teaching handle attachment recognition switch can be manipulated by means
 of a remote manipulation jig 421.
 The embodiment of the present invention will be described below in detail.
 First, a simple teaching apparatus which is used in the direct teaching of
 the present embodiment will be described with reference to a plan in FIG.
 18(a) and a perspective view in FIG. 18(b) which show the simple teaching
 apparatus set in a jig which is used in remote manipulation.
 Simple teaching apparatus 461 is of approximately palm size and structured
 such that the operator can manipulate each switch holding it by one hand
 (since the other hand of the operator must hold a later described teaching
 handle, the simple teaching apparatus must be of a one-hand portable
 size). Here, each switch means servo power retention switch 464, emergency
 stop button 465, input switch 466, memory data editing key 467, and
 further state indication lamp 468 is also included therein.
 The operator can input the servo power by holding servo power retention
 switch 464 with a fixed level of force. By continuously holding the switch
 during teaching operation, servo power active condition can be maintained.
 Also, when the operator feels danger during the direct teaching operation,
 operator 411 can stop the motion of the robot by releasing the hold of
 servo power retention switch 464 or by pushing emergency stop button 465.
 Input switch 466 is provided for storing the position of the robot in the
 controller only when the switch is pushed with the position data of just
 that time, and hence it is pushed every teaching time at every teaching
 position.
 Memory data editing key 467 is used for performing editing such as
 addition, change or erasing of storage data. By using this key, it becomes
 possible to perform such as editing of teaching points.
 State indication lamp 462 is a lamp for indicating that teaching is in
 progress.
 With the teaching apparatus structured as above, when the operator performs
 direct teaching of a working point by holding the teaching tool and the
 simple teaching apparatus thereby leading the robot, the robot never moves
 contrary to the operator's intention so far as the manipulation button on
 the teaching handle is not pushed. Also when the signal from the handle
 attachment recognition switch is not inputted, the robot does not move.
 Moreover, when the signal from a displacement switch which belongs to the
 compliance mechanism is changed, the robot's motion is suddenly stopped.
 Further, by attaching the teaching handle to he simple teaching apparatus,
 it becomes possible to perform remote control. In addition, since no
 mechanical brake is activated after the robot is stopped by the electric
 brake in an emergency mode, there is no risk that the operator is kept
 constrained between the robot and the work.
 Next, the teaching handle to be used in the direct teaching of the present
 invention will again be described with reference to FIG. 16.
 The teaching handle is structured such that it has a form which can fast be
 grasped by hand having a manipulation button provided on a grip, and the
 operator can move the robot by pushing the manipulation button. Also on a
 handle attachment jig portion, there is provided a handle attachment
 recognition switch, and with which a signal can be recognized only when
 the teaching handle is attached.
 Next, the compliance mechanism to be used in the direct teaching of the
 present invention will be described. The compliance mechanism is provided
 between the teaching handle and the tip of the robot or between the
 working tool attached with the teaching handle and the tip of the robot.
 When the signal from a switch or a sensor incorporated in the compliance
 mechanism is changed due to a fixed amount of displacement of the
 compliance mechanism, motion of the robot is immediately stopped.
 Next, a remote manipulation jig to be used for direct teaching of the
 present invention will be described with reference to FIG. 18.
 The remote manipulation jig is structured so that a simple teaching
 apparatus and a teaching handle can be attached thereon, and also has a
 structure which allows the operator to easily hold the simple teaching
 apparatus by one hand and performs remote control of the robot by using
 the teaching handle by the other hand.
 FIG. 16 is a block diagram showing a control system of the present
 invention. The control method executed in the embodiment will be described
 below. According to the control method of the present embodiment, force
 detector 309 detects the leading force of teaching handle 306 held by the
 operator, and based on the detector detection data, motion model operation
 part 301 computes the position directive on the rectangular Cartesian
 coordinate system which is established according to the motion model
 prepared by using imaginary inertia and viscosity. Motion model operation
 part 301 further inversely transforms the computed position directive to
 the data on a revolute mode system to obtain an articulation angle
 directive of each articulation. Position/speed servo system 302 calculates
 the motor generation torque based on this articulation angle directive and
 the articulation angle as well as the articulation speed detected by
 articulation angle detector 305 provided on each driving unit or on each
 articulation part of the robot, and accordingly the servo motor of the
 robot is driven by the servo amplifier.
 When the operator leads the tool portion of the robot to a working point of
 a working object and pushes the input switch provided on the simple
 teaching apparatus, teaching of the working point is performed with
 reference to the working object.
 FIG. 19 and FIG. 20 show embodiments of the welding work in the direct
 teaching method of the robot of the present invention. Operator 441
 fixedly attaches teaching handle 443 on the welding torch or the like
 provided at the wrist portion of robot 442, and then supplies the servo
 power by holding the servo power retention switch (464 in FIG. 18) on
 simple teaching apparatus 444. If there is no change in the signal from
 the handle recognition switch, the servo power can not be inputted.
 As shown in FIG. 19, it becomes possible for the operator to lead the robot
 by holding the teaching handle fixed to the force detector and pushing the
 manipulation button, and after leading the robot, the operator performs
 teaching of important points of working object 445 which is to be welded.
 At this time, if the welding torch or the teaching handle makes contact
 with the working object, the compliance mechanism provided between the
 wrist portion of the robot and the welding torch is deformed by the force,
 thereby preventing deformation of the welding torch or the teaching
 handle, and at the same time according to a signal outputted from the
 compliance mechanism when its deformation reaches a fixed level, the
 motion of the robot is stopped.
 When the configuration of the working object is complex and there is a
 probability of danger such as that the operator's arm may come into
 contact with another object when teaching is performed with a teaching
 handle fixed to the welding torch, the teaching handle is detached from
 the handle attachment jig on the welding torch and attached to a remote
 manipulation jig together with the simple teaching apparatus (FIG. 20).
 Then the operator holds the simple teaching apparatus on the remote
 manipulation jig by one hand and holds the teaching handle by the other
 hand to perform remote control for leading the robot for performing the
 teaching of the working point.
 Further, the data from force detector 451, the directives from simple
 teaching apparatus 452, the data from the articulation angle detector
 attached to each driving shaft of robot 453 are stored in robot controller
 454, and processed there to drive the robot.
 As described above, according to the present embodiment, when the operator
 holds the teaching tool and the simple teaching apparatus and leads the
 robot to perform the direct teaching of the working point, even if the
 output force is released from the force detector, the robot never moves
 contrary to the operator's intention so far as the manipulation button on
 the teaching handle is not pushed. Also even if the teaching handle is not
 attached by a miss, when the signal from the handle attachment recognition
 switch is not inputted, the robot does not move. Further, even if the
 handle or the working tool makes contact with the work or the like, then
 the signal from a switch or a sensor of the compliance mechanism is
 inputted to urgently stop the motion of the robot. Moreover, when the
 teaching is performed for a narrow portion, by attaching the teaching
 handle to the simple teaching apparatus, it becomes possible to perform
 the remote control. In addition, if the worst case occurs such that the
 operator is caught by the robot at the time of emergency stop, by
 previously preparing the system that no mechanical brake is activated in
 such a case, the operator can easily escape from the robot. Therefore,
 with this embodiment, the operator can perform the direct teaching in
 extreme safety to the good effect of the present invention.
 Subsequently, another embodiment of the present invention will be
 described. FIG. 21 is a view showing a structure of another embodiment of
 the present invention.
 In FIG. 21, numeral 501 is a robot, 502 a wrist of the robot, 503 a
 compliance mechanism, 504 a tool support, 505 a tool (for example, a
 welding torch), 506 a force sensor and 507 a teaching handle.
 Wrist 502 of the robot is a movable shaft disposed at the tip of robot 501,
 and tool support 504 may be attached here according a case, however in
 this embodiment, tool support 504 is attached through compliance mechanism
 503. Compliance mechanism 503 has the elasticity to return, after
 collision, to the original position, and for example, it is made of a
 spring or the like. Tool support 504 may be of a type which is formed in a
 unit with tool 505, constituting a part of tool 505.
 Tool support 504 is attached with an integrated unit comprising force
 sensor 506 and teaching handle 507. However, as described later, this
 integrated unit is made with a mechanism to be detachable (such as a screw
 type or a hook type unit which can be attached/detached by hand without
 using any tool is allowable) at the time of playback operation.
 Force sensor 506 detects the force (direction and magnitude) to be applied
 by the operator to teaching handle 507 held by the operator, and includes
 the function to send the force data through signal line 508 to a robot
 controller not shown in the figure. Since the robot controller controls
 the motion so as to move robot 501 in the direction of the force, the
 operator performs teaching of the working position by applying force to
 teaching handle 507 with one hand in the direction he wants to make the
 robot move. In this case, by pushing a switch button not shown by the
 other hand, the position of motion at the time when the switch is pushed
 is inputted in the memory of the robot controller and stored as the
 teaching position.
 By the way, with an apparatus of this kind, when tool 505 has collided with
 the work during teaching operation, the elasticity of compliance mechanism
 503 absorbs the energy of collision and protects tool 505 and force sensor
 506. Further, when the teaching operator falls holding the teaching
 handle, although an excessive load is applied to the teaching handle
 portion, also in this case the elasticity of compliance mechanism 503
 absorbs the excessive load to prevent the erroneous motion of the robot.
 Furthermore, when operator sandwiching trouble is generated between tool
 505 and the robot arm, compliance mechanism 506 absorbs the energy of the
 robot within its capacity to avoid a dangerous sandwiching condition.
 Further, an integrated unit comprising force sensor 506 and teaching handle
 507 is arranged to be detachable from tool support 504, and as shown in
 FIG. 22 with a dotted line, it is held at unit holder 509 provided on a
 part of the robot arm or on the robot controller when playback operation
 is in progress. By means of this arrangement, force sensor 506 is
 protected and the working will not be disturbed by signal line 508 of the
 force sensor in playback operation. In this case, compliance mechanism 503
 is not always necessary and hence it can be omitted.
 FIG. 22 shows an example in which teaching handle 507 is situated
 perpendicular to the line L connecting the tip of the wrist of the robot
 and the teaching point P, standing outside the robot viewed from base 510
 of the robot.
 By arranging the robot in this way, teaching handle 507 faces the operator
 standing side (generally the operator stands outside the position of the
 tip of the robot arm viewed from the robot base) and the direction in
 which the operator pushes down teaching handle 507 is usually the
 direction in which tool 505 approaches the work (not shown), therefore
 manipulation of the teaching handle becomes very easy.
 As describe above and according to the present embodiment, it becomes
 possible, during teaching operation, to protect a tool or a force sensor
 or prevent the abnormal motion of the robot to be caused by the excessive
 load, and further since it becomes possible to avoid the danger of being
 sandwiched by the robot, the teaching operator can perform teaching at
 ease. Also since the force sensor and the teaching handle are detached in
 playback operation and held on the robot or on a part of the robot
 controller, the operator is not needed to pay consideration for the
 protection of the force sensor.