Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
  • B25J13/00—Controls for manipulators
  • B25J13/02—Hand grip control means
  • B25J13/025—Hand grip control means comprising haptic means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
  • B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
  • B25J19/0004—Braking devices
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S901/00—Robots
  • Y10S901/19—Drive system for arm
  • Y10S901/23—Electric motor
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S901/00—Robots
  • Y10S901/27—Arm part
  • Y10S901/28—Joint

Definitions

• the present invention relates to a hinge for a robot arm intended more particularly for haptic and / or cobotic applications.
• the haptic is a robotics in which robots are used as feedback interface of effort per ⁇ to simulate interactions with physi- Siques virtual environments.
• Cobotics is a field of robotics in which robots assist the user, by sharing with him the same tool or the same task, to guide the user, to compensate the weight of the tool, to increase the force, to suppress the movements unwanted or unwanted user.
• Such a robot arm articulation generally comprises a first segment and a second segment which are articulated to each other by a connection to a degree of freedom and which are connected by an actuator arranged to move the second segment relative to the first segment.
• An area of the second segment is manipulated directly by the user (haptic) or is provided with an element such as a user-manipulated tool (cobotics).
• a robot arm generally comprises a plurality of such joints, the number of which depends on the number of parts of the arm movable relative to each other necessary to achieve all the desired movements.
• the invention relates more particularly to applications in which it is not sought to increase the strength of the user but simply to guide his movements or counter if they became undesirable, to improve the safety of the gesture.
• the actuation of the arm must be transparent to the user, that is to say that the user must not feel resistance or parasitic movements to the movement that he wishes to achieve, but must allow if necessary the development of significant efforts to oppose the movement of the arm and thus prevent the user from achieving a displacement that would be unwanted.
• This ability to develop significant reaction forces is for example used to simulate shock or contact with a virtual surface (when the arm is used as an interface with a virtual reality software) or to define boundaries of a work area in which must be maintained a tool attached to the end of the arm.
• the actuator must therefore be both fast and powerful. In haptics and cobotics, these two behaviors can be described using two quantities characterizing the performances of an actuator:
• the range in front of to be as big as possible the range of the mechanical impedance range that can be provided by the actuator (the mechanical impedance being the resistance that the actuator opposes to the movement of the arm under the effect of an external force), the range in front of to be as big as possible,
• actuators pneumatic cylinders, hydraulic cylinders or electric motors, however, none of them fully satisfies the above conditions.
• electric motors the most powerful are also those with the greatest inertia and the most friction thus leading to prohibitive transition times for the intended application. This observation can be extrapolated to other types of actuators.
• a motorized robot arm joint be provided to improve the safety of haptic or cobotic applications without sacrificing ergonomics and performance.
• This motorized articulation comprises a first segment, a second segment mounted to move on the first segment, an actuator arranged to reversibly transmit a movement to the second segment relative to the first segment and locking means which are interposed between the first segment and the first segment. second segment and which are controllable to temporarily render the movement transmission temporarily irreversible.
• the actuator is integral with a support which carries a first friction element and which is mounted on the first segment to be movable, under the effect of a motor force greater than a predetermined threshold, so as to apply the first element.
• the locking means of rotation The second segment acts in parallel with the actuator to create a reaction force opposing the motion that is to be avoided.
• the actuator is thus used to move the second segment relative to the first segment or to impose limits on its movement. In this second case, if the external forces exerted on the second segment are greater than a predetermined force, then the locking means is added to the actuator to provide the missing resisting force.
• the friction elements form relatively effective locking means but are difficult to adjust.
• An object of the invention is to provide such a joint whose locking means are simple to use while being effective.
• a motorized articulation of a robot arm comprising a first segment, a second segment mounted to move on the first segment and driven by an actuator connected to a control unit and secured to a support. which carries a first friction element and which is mounted on the first segment to be movable, under the effect of a motor force greater than a predetermined threshold, so as to apply the first friction element against a second integral friction element of the second segment.
• One of the friction elements has a wedge shape having a bisecting plane substantially parallel to a plane of movement of the second segment so that it can be engaged between two jaws of the other of the friction elements, the jaws having surfaces arranged to take contact punctually with the wedge shape.
• having surfaces providing a point contact makes the locking means more tolerant of manufacturing defects and in particular relative positioning defects.
• the surfaces of the jaws are spherical.
• the surfaces are then relatively simple to produce, for example by machining.
• the jaws are mounted with a game in a direction substantially normal to the bisecting plane.
• the second segment is mounted on the first segment to pivot about an axis perpendicular to the first segment and is integral with a second wheel coaxial with the pivot axis so that the second wheel forms the driving element of the second segment and, preferably, the support is mounted to pivot along an axis parallel to said axis.
• the second segment rotates freely (the support is then in a position called inactivation).
• this tangential force is greater than the threshold, the support of the motor is rotated until the support puts in contact the friction elements (the support is then in the so-called activation position). Blocking is thus achieved by exerting a force directly on the second segment.
• the residual movement of the segment between its position at the moment of release and its position where the blockage is effective can be adjusted by adjusting the space between the friction elements when the carrier is in the inactivation position. The smaller the space, the higher the accuracy.
• the predetermined threshold is defined by calibrating at least one spring mounted to exert on the support a force opposing a displacement thereof to bring into contact the friction elements.
• the threshold which is lower than the maximum torque developed by the engine, is extremely simple.
• the threshold can be simply adjusted by adjusting the spring preload.
• FIG. 1 is a schematic view of an arm according to the second embodiment of the invention.
• FIG. 2 is an enlarged perspective view of zone II of FIG. 1 and FIG. 2a is a detail view of FIG.
• FIG. 3 is a view similar to FIG. 2 according to another angle of view
• FIG. 4 is a partial perspective view, with cutaway, of the hinge according to the invention, in the absence of force exerted on the second segment,
• FIG. 5 is a view from above of this articulation, in the presence of a force exerted on the second segment,
• FIG. 6 is an enlarged view of zone VI of FIG. 4,
• FIG. 7 is a view schematically illustrating the friction elements of the joint of the invention.
• FIGS. 8a and 8b are views similar to FIG. 7 showing the contact of the friction elements in the event of a height shift
• - Figures 9a, 9b are views similar to Figure 7 showing the engagement of the friction elements in case of angular offset.
• the motorized articulation according to the invention is here described in a surgical application.
• the free end of the arm is equipped with a bur that a surgeon manipulates to remove diseased parts of a patient 's body without touching the healthy parts.
• the arm joint according to the invention comprises a first segment 1 and a second segment 2 q i extend on either side of the joint to form parts of the arm.
• the segments can thus be in one piece with the arm parts, or else be definitively fixed or removable thereon.
• the first segment 1 has a first end 1.1 connected to a base 101 and a second end 1.2 which is secured to a shaft 3 on which is pivotally mounted a first end 2.1 of the second segment 2 which has at the opposite a second end 2.2 provided of a tool not shown.
• the articulation comprises a support 5 mounted on the first segment 1 for pivoting about an axis 7 parallel to the axis of articulation of the second segment 2 on the first segment 1.
• the support 5 is here carried by a tubular frame 6 , of substantially frustoconical shape, which is fixed by its large section on the segment 1.
• a motor 8 is mounted on the support 5 in such a way that its output shaft coincides with the axis 7.
• the balancing of the support assembly 5 and the motor 8 is relatively simple because of the coaxiality.
• the force exerted by the motor 8 on the support 5 is furthermore independent of the orientation of the arm relative to the gravitational field, in particular when the axis of rotation of the support 5 is not parallel to gravity.
• the output shaft of the motor 8 is engaged via a cable with a wheel sector 9 secured to the end 2.1 of the second segment 2.
• the output shaft may carry a toothed wheel meshing with a toothing arranged on the wheel sector 9.
• the support 5 has an end 5.1 provided with a friction element, generally designated 10, extending facing a friction element, generally designated 11, secured to the end 2.1.
• the friction elements 10, 11 form a locking member of the rotation of the segment 2 relative to the segment 1.
• the friction element 11 is more precisely fixed to the wheel sector 9 and extends arcuate to the axis 3.
• the friction element 11 has the shape of an annular sector having a profile. wedge shape delimited laterally by two frustoconical surfaces 11.1, 11.2 which are coaxial with the axis 3 and meet by forming a circumferential edge directed radially outwards.
• the friction element 11 has a bisecting plane P which is substantially parallel to the plane parallel to which the segment 2 moves, that is to say a plane perpendicular to the axis 3.
• the friction element 10 comprises a jaw carrier 12 integral with the support 5 and provided with two pairs of jaws 13.1, 13.2 (for convenience, the pair 13.1 of the jaws and the jaw 13.2 the pair 13.2 of jaws) will be called jaws 13.1.
• the jaws 13.1, 13.2 are spaced from each other in a plane perpendicular to the axis 7 so that they extend each on one side of the longitudinal direction of the support 5 (the longitudinal direction of the support 5 crosses the middle of the end 5.1 and the axis 7).
• the jaws 13.1, 13.2 are mounted on the jaw carrier 12 to slide parallel to the axis 3.
• Each jaw 13.1, 13.2 has contact surfaces 14 which extend each on one side of the bisecting plane P and which have a curved shape in two directions to contact punctually with the surfaces 11.1, 11.2.
• the contact surfaces 14 may for example be in the form of a spherical cap.
• the support 5 has a position of inactivation of the locking member and two positions of activation of the locking member on each side of the inactivation position.
• the support 5 is in the inactivation position when the longitudinal direction of the support 5 extends radially with respect to the wheel sector 9 and the friction element 11. In this position, there is a space between the contact 14 of the jaws 13.1, 13.2 of the friction element 10 and the surfaces 11.1, 11.2 of the friction element 11.
• the support 5 is in the activation position when the contact surfaces 14 of one of the jaws 13.1, 13.2 of the friction element 10 are in contact with the surfaces 11.1, 11.2 of the friction element 11.
• the support 5 (more precisely the plane containing the axis 7 and the point of contact of the contact surfaces 14 with the surfaces 11.1, 11.2) then forms an angle with the radial plane of the friction element 11 passing through the point of contact of the contact surfaces 14 with (see Figure 5).
• ⁇ the coefficient of friction of the material pair of the contact surfaces 14 and surfaces 11.1, 11.2, and has as a half-angle at the top of the V formed by the surfaces 11.1 and 11.2, it is necessary to have tan ( ⁇ ) sin ( ⁇ ) ⁇ as a blocking condition and tan ()> ⁇ to avoid a jamming which would oppose the unlocking of the segment 2.
• the support 5 is returned to the inactivation position by a functioning return spring 15 in compression to exert on the support 5 a force opposing a movement thereof to activate 1 'locking member.
• the return spring 15 extends radially with respect to the wheel sector 9 having one end bearing against the frame 6 and an opposite end pushing a finger 16 received in a V-shaped slot 17 formed in the end 5.2 of the support 5 opposite to the end 5.1 of the support 5.
• the angle of the V makes it possible to adjust the law of force produced by the spring 15 when it opposes the displacement of the support 5. It will be noted that it is easy to prestress the spring 15 to adjust the triggering threshold of the locking device. For example, it is possible to provide a nut coaxially mounted on the finger 16 to shorten the length of the spring 15.
• the motor 8 is of course sized to be able to move the segment 2 relative to the segment 1 and is connected to a control unit 20.
• the control unit 20 is a computer arranged to execute a control program of said motor.
• the control program delineates a work area delimited by a boundary envelope defined from medical imaging.
• the control unit 20 controls the motor 8 so that the arm follows the movements of the cutter manipulated by the surgeon within the confines of the boundary envelope and blocks the motor 8 to oppose the movement of the cutter outside the limits of the border envelope.
• the motor 8 will be controlled to resist (first increase in torque) before the blocking device is activated (1 'activation causing a second increase in torque).
• the tracking of the envelope is possible before the second increase of the couple.
• any effort exerted by the engine on the second segment 2 creates a reaction force transmitted to the support 5 which tends to pivot and to bring one or the other of the jaws 13.1, 13.2 against the surfaces 11.1, 11.2 (according to the relative direction of rotation of the segments 1 and 2 and the direction of rotation of the motor 8). Lateral shifting of the jaws 13; 1, 13.2 relative to the longitudinal direction of the support 5 also creates the conditions of a jamming reinforcing the blocking.
• the resisting force provided by the spring 15 opposing the pivoting of the support 5 constitutes a threshold force for the activation of the locking member. This force is determined in such a way that the friction elements 10, 11 come into contact against each other before the motor 8 has produced its maximum effort.
• the locking member is relatively tolerant to the relative positioning errors of the jaws 13 and 1 'friction element 11.
• the friction element 11 is offset in height by a distance Ah upwards relative to the support 5.
• the locking member is activated, one of the jaws 13.1, 13.2 here, the jaw 13.1 is brought closer to the friction element 11 and only the upper contact surface 14 comes into contact with the surface 11.1.
• the upper contact surface 14 rubs on the surface 11.1 and causes vertical sliding of the jaw 13.1 until the lower contact surface 14 comes into contact with the surface 11.2 causing the relative locking segments.
• the friction element 11 is angularly offset by an angle ⁇ in a radial plane with respect to the support 5.
• one of the jaws 13.1, 13.2, here the jaw 13.1 is close to the friction element 11 and alone the upper contact surface 14 comes into contact with the surface 11.1.
• the upper contact surface 14 rubs on the surface 11.1 and causes vertical sliding of the jaw 13.1 until the lower contact surface 14 comes into contact with the surface 11.2 causing the relative locking segments.
• the first segment may be formed by a section of the arm, a trunk or a robot base.
• the second segment may for example be mobile in translation relative to the first segment.
• the actuator may be a jack driving a rack which meshes with a toothed wheel or a motor driving a wheel rolling on a rectilinear track or not.
• a kinematic inversion is also possible.
• the arm may comprise an actuator for each of the joints or for one or more of them (trunk, shoulder, elbow, wrist %) only.
• the segments may have different shapes from those shown.
• the axis of the motor may not be confused with the pivot axis of the support.
• the male friction element may be mounted on the support and the female friction element on the second segment.
• the bracket can be mounted to slide instead of pivoting.
• one of the friction elements may have contact surfaces defining a cross-sectional V overlap (as in a grooved pulley) or any other shape.
• the jaws 13 may be mounted on the jaw carrier 12 to rotate each about an axis perpendicular to the axis 7 instead of being mounted to slide parallel thereto.
• the jaws 13 may alternatively be mounted on the jaw carrier 12 to slide each along an axis perpendicular to the axis 7 instead of being mounted to slide parallel thereto.
• the return spring may extend tangentially to a path of the support to oppose a movement of the support to bring the friction elements into contact.
• the spring may also be a flexible leaf spring pushing a V-shaped piece
• the friction element may comprise only one pair of jaws if the locking is to occur only for one direction of rotation.
• the invention applies to any articulation "i" between two segments that can be located in the middle of an articulated mechanism having a number "n” of joints numbered from 1 to n.

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• Engineering & Computer Science (AREA)
• Robotics (AREA)
• Mechanical Engineering (AREA)
• Human Computer Interaction (AREA)
• Manipulator (AREA)

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• 2014
  • 2014-02-21 FR FR1451425A patent/FR3017816B1/fr not_active Expired - Fee Related
• 2015
  • 2015-02-20 WO PCT/EP2015/053579 patent/WO2015124711A1/fr not_active Ceased
  • 2015-02-20 EP EP15706000.5A patent/EP3107696A1/de not_active Withdrawn
  • 2015-02-20 US US15/108,946 patent/US20160325436A1/en not_active Abandoned

Non-Patent Citations (1)

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