NON-LINEAR ELASTIC JOINT WITH AN ELASTIC MECHANISM AND DRIVES

Description

[0001] The invention relates to nonlinear elastic joints with an elastic mechanism and drives.

[0002] German patent application DE 10 2012 214 094 B3 discloses a robot joint system comprising two joint units, each with one joint, two drive motors, an energy storage device, and an auxiliary energy storage device. The auxiliary energy storage device, located between the two joint units, enables energy transfer from one joint unit to the other, and thus from one joint to the other. This robot joint system is only feasible with considerable effort. In particular, four drive motors are required.

[0003] German patent application DE 10 2006 016 958 A1 discloses an antagonistic pivoting device. This device has a joint element that pivots about a pivot axis and is connected to two drive units via two power transmission devices. A passively acting stiffness adjustment device, which is not adjustable, is integrated into both power transmission devices.

[0004] German patent application DE 10 2016 226 174 A1 describes a nonlinear vibration mechanism with several rigid elements, wherein individual segments are connected to each other via a joint, in particular a rotary joint. A vibration element is provided between each segment for force and / or motion transmission. The sum of the interacting vibration elements results in nonlinear vibration behavior without the need for an actuator. Adjustment of the nonlinear vibration behavior is not provided.

[0005] A robot manipulator joint drive with torque support is disclosed in publication EP 2 006 055 B1. The torsional stiffness of the elastic joint varies via the rotation angle of a cam disc.

[0006] German patent application DE 10 2007 014 023 A1 discloses a robot manipulator arm articulated drive, which has a drive motor and a drive gearbox, the latter comprising a torque arm rotatable about an axial plane and an output shaft. The torque arm has a cam disk lying in a cylindrical plane, on which a cam wheel preloaded by an axial tension spring runs.

[0007] An actuator with variable stiffness and a large stiffness range is disclosed in European Patent EP 2 989 345 B1. A spring with an adjustable spring constant comprises a bending rod that can be connected to a rotating shaft and has at least one curved section. At least one driven rotating element is in contact with this section, so that the connection stiffness between a rotating shaft and a connecting element can be varied.

[0008] Document US 10,751,887 B2 describes a mechanism with two main linkages coupled by a joint. A connecting mechanism includes a pivot rod on which a sliding piece is mounted. The sliding piece is connected to the joint via a movement mechanism with lever mechanisms.

[0009] Document US 2019 / 0 126 498 A1 discloses a variable-stiffness actuator comprising a bending plate. The bending plate includes a first cantilever beam extending inward from an outer circumference of the bending plate. A housing and the bending plate are rotatably mounted about a common pivot axis. A first contact piece is pivotally attached to the housing via a hinge. The first contact piece rotates about the hinge around a first axis of rotation, which is offset on the housing relative to the pivot axis. The first contact piece engages the first cantilever beam at a variable angle about the axis of rotation to adjust the stiffness of a mechanical connection between the bending plate and the housing.

[0010] Publication JP 2014-097 548 A describes a variable-stiffness mechanism, a variable-stiffness drive device, and a joint drive device. The mechanism comprises a driven arm, a solid cam with a cam surface, and driven cam tappets that move in accordance with the displacement of the output arm relative to the solid cam. Furthermore, the mechanism incorporates helical compression springs that press the cam tappets against the cam surface, providing stiffness corresponding to the angle of inclination of the cam surface. The cam surface is designed such that the curvature of its cross-section varies depending on the position of the cam tappets perpendicular to the surface.

[0011] The stiffness of the mechanisms of these printed materials is not adjustable.

[0012] German patent application DE 10 2018 008 378 A1 discloses elastic joints with a drive, an elastic mechanism, and a driven element. The elastic, and therefore compliant, joint represents a combination of cam and lever technology. Stiffness is adjusted by means of an actuating mechanism connected to the pivot of the lever mechanism. The transmissible torque is limited by springs acting on rollers.

[0013] The invention is based on the objective of creating an elastic joint with variable stiffness.

[0014] This problem is solved by the features listed in the independent patent claim.

[0015] Nonlinear elastic joints with an elastic mechanism and drives are characterized in particular by variable stiffness.

[0016] A control disk connected to a first drive has recesses or protrusions arranged at intervals along at least one circular path, each recess or protrusion forming a track for a roller. The rollers are pivotally connected to the first lever arms of two-sided levers. The second lever arms of the two-sided levers are pivotally connected via a connecting element to the first end of a compression spring. The second end of the compression spring is connected to the rollers and the first lever arms.

[0017] Furthermore, the pivots of the double-sided levers are coupled to an adjustment mechanism with a second drive to change the position of the pivots parallel to the control disk and thus the stiffness.

[0018] The elastic joint is thus advantageously a nonlinear elastic joint with variable stiffness. This elastic, and therefore compliant, joint represents a combination of a control disk and levers to implement a nonlinear mechanism. The stiffness is adjusted by means of the adjustment mechanism connected to the pivots of the two-sided levers. To ensure a progressive, nonlinear torque curve, the roller tracks are formed by recesses or protrusions on the control disk, which acts as a cam. The control disk is a circular disk or an annular disk with recesses or protrusions on a base. Rotating the control disk produces a nonlinear torque curve. The remaining stiffness is achieved via the levers and the compression spring.Multiple levers distribute the forces, allowing for a greater torque to be absorbed.

[0019] The operating principle is based on the fact that when the control disc rotates, the rollers, the joints of the first lever arms, and the second end of the compression spring are moved away from the control disc. Simultaneously, the connecting piece, and thus the first end of the compression spring, is moved towards the control disc. The compression spring is compressed. The stiffness of the mechanism can be adjusted using the sliding pivots. This adjustment changes the compliance, which is achieved by increasing the compression of the compression spring.

[0020] The levers in the elastic mechanism enable progressive, nonlinear angular torque characteristics. Furthermore, the torque required to adjust the stiffness is small. The stiffness can be set from soft to infinitely rigid, with the pivots of the levers being located at one of the end positions of the displacement in the latter case.

[0021] This makes the nonlinear elastic joint with its elastic mechanism and drives particularly suitable for robots. Controllable stiffness ensures safe human-robot interaction. At the same time, sufficiently high contact forces can be applied as needed. This makes robots safer and enables them to perform various assembly tasks or physically demanding service tasks, for example.

[0022] Advantageous embodiments of the invention are specified in the dependent patent claims.

[0023] The depressions or elevations advantageously have an arc shape, or the cross-sections of the depressions or elevations are circular segments.

[0024] The compression spring can be arranged, at least partially, within a cup-shaped body with a rim, with the second end of the compression spring located on the base of the cup. The rollers and the first lever arms are connected to the rim of the cup-shaped body. This results in a compact assembly comprising the rollers, the double-sided levers, the connecting element, the compression spring, and the cup-shaped body.

[0025] The compression spring is preferably a helical compression spring.

[0026] The adjustment mechanism can include a disc with openings for guiding the pivots. This disc is positioned parallel to the control disc at a distance from the pivots. By means of these openings and by rotating the disc, the pivots of the two-sided levers can be easily adjusted together. Each pivot is designed as part of an angle bracket or a T-piece. In the latter configuration, each lever has two parallel lever arms, so that the crossbar of the T-piece acts as the pivot for these lever arms.

[0027] The adjustment mechanism can advantageously have the second drive either with a worm shaft in conjunction with a worm gear. The disc is a worm wheel or has a worm gear. A worm gear implemented in this way is advantageously self-locking, so that a secure position is ensured after movement of the pivots.

[0028] The control disc, as the first component of the elastic mechanism, is connected to the first drive. The second component of the elastic mechanism includes the rollers, the connecting piece, the double-sided levers, the compression spring, the cup-shaped body, and the adjustment mechanism. The second component of the elastic mechanism is the output of the nonlinear elastic joint.

[0029] The first component of the elastic mechanism and the drive can be the components of a cup-shaped housing, with at least a portion of the rotatably mounted control disc forming the base of the cup-shaped housing. The rollers, the connecting element, the double-sided levers, the compression spring, the cup-shaped body, and at least the disc of the adjusting mechanism are the components of a cylinder, which is located at least partially within the cup-shaped housing. This results in a compact design for the nonlinear elastic joint equipped with a drive.

[0030] The rollers, in conjunction with the first lever arms, can be designed as fixed casters, each with a frame and a roller inserted therein. The frames are articulated to the first lever arms of the double-sided levers. Furthermore, the second end of the compression spring is connected to the first lever arms and the frames of the fixed casters.

[0031] The first drive, the control disc, the second drive, the disc and / or the first drive is or are optionally connected individually or in combination with a rotary encoder or encoders.

[0032] The rotary encoder(s) can be connected to a control unit. This allows the stiffness to be precisely adjusted.

[0033] The output shaft can be or become connected to a robot component. Furthermore, the first drive shaft, in conjunction with the control disc, and the output shaft can each be or become connected to a robot component.

[0034] To realize the invention, it is also advantageous to combine the aforementioned configurations, embodiments and features of the claims in each arrangement.

[0035] An embodiment of the invention is shown in principle in the drawings and is described in more detail below.

[0036] They show: Fig. 1 a principle of an elastic mechanism with a control disc, double-sided levers and a compression spring in a first position, Fig. 2 the principle of the elastic mechanism with the components in a second position, Fig. 3 an elastic mechanism, Fig. 4 a disc of an adjustment mechanism for positioning pivots of the levers and Fig. 5 an elastic joint with an elastic mechanism and drives.

[0037] A nonlinear elastic joint essentially consists of an elastic mechanism and actuators 18, 19. The elastic mechanism includes a control disc 1, rollers 3, double-sided levers 4, an adjusting mechanism 12, a connecting part 5, a compression spring 6 and a cup-shaped body 7.

[0038] They show the Fig. 1 a principle of an elastic mechanism with a control disc 1, double-sided levers 4 and a compression spring 6 in a first position and the Fig. 2 the principle of the elastic mechanism with the components in a second position in principal representations.

[0039] The control disk 1 has recesses 8 arranged at intervals along at least one circular path, each recess 8 forming a path for a roller 3. The rollers 3 are pivotally connected to the first lever arms 9 of the two-sided levers 4. The second lever arms 10 of the two-sided levers 4 are pivotally connected via the connecting element 5 to a first end of the compression spring 6. The second end of the compression spring 6 is connected to the rollers 3 by means of the cup-shaped body 7. For this purpose, the cup-shaped body 7 has a rim that is connected to the rollers 3. The second end of the compression spring 6 is located on the bottom of the cup. The compression spring 6 can be a helical compression spring. The recesses 8 can have an arc shape or the cross-sections of circular segments. Pivots 11 of the two-sided levers 4 are coupled to the adjusting mechanism 12 for changing the position of the pivots 11 parallel to the control disk 1.

[0040] The Fig. 3 shows an elastic mechanism in a simplified representation.

[0041] The rollers 3, in conjunction with the first lever arms 9, can be fixed casters 2, each with a frame 14 and a roller 3 inserted therein. The frames 14 are pivotally connected to the first lever arms 9 of the double-sided levers 4. Furthermore, the second end of the compression spring 6 is connected to the first lever arms 9 and the frames 14 of the fixed casters 2.

[0042] The adjustment mechanism 12 is a disk 13 connected to a second drive 19, with openings 17 for guiding the pivots 11. The disk 13 is arranged parallel to the control disk 1 at a distance from the control disk 1. The pivots 11 of the two-sided levers 4 can be easily adjusted together by means of the openings 17 and by rotation. Each pivot 11 is designed as part of an angled piece or a T-piece 15. In the latter variant, two lever arms 9, 10 arranged parallel to each other are provided for each two-sided lever 4, such that the crossbar of the T-piece 15 forms the pivots 11 of the two-sided levers 4. Furthermore, the T-pieces 15 with the pivots 11 are guided parallel to the control disk 1 by means of a guide 16.

[0043] The swivel casters 2 are designed as non-swivel casters 3, each consisting of the frame 14 and the caster 3 inserted therein.

[0044] The Fig. 4 shows a disk 13 of an adjustment mechanism 12 for positioning pivots 11 of the double-sided levers 4 in a schematic representation.

[0045] The disc 13 of the adjustment mechanism 12 has, for example, three openings 17 for guiding the T-pieces 15 of the pivots 11. The disc 13 is arranged parallel to the control disc 1 at a distance from each other.

[0046] The Fig. 5 shows an elastic joint with an elastic mechanism, a first drive 18 and a second drive 19 in a schematic representation.

[0047] The second drive 19 for the disk 13 is an electric motor connected to a worm shaft that engages with a worm gear. The disk 13 is either a worm gear or has a worm gear. A self-locking worm gear designed in this way is known. The electric motor and the worm shaft can be spaced apart from each other and connected via a tension member.

[0048] The control disc 1, as a first component of the elastic mechanism, is connected to the first drive 18. The first drive 18 can be an electric motor with a gearbox. A second component of the elastic mechanism essentially comprises the casters 2, the connecting part 5, the double-sided levers 4, the compression spring 6, the cup-shaped body 7, and the adjusting mechanism 12. The second component of the elastic mechanism is the output of the non-linear elastic joint.

[0049] Furthermore, the first component of the elastic mechanism and the first drive 18 can be components of a cup-shaped housing 20, wherein at least a portion of the rotatably mounted control disk 1 forms the base of the cup-shaped housing 20. The caster wheels 2, the connecting part 5, the double-sided levers 4, the compression spring 6, the cup-shaped body 7, and at least the disk 13 of the adjusting mechanism 12 can be arranged in a cylinder 21, which is located at least partially within the cup-shaped housing 20. For this purpose, the portion of the cylinder 21 within the housing 20 can be mounted, for example, with at least one rolling element bearing, so that the cylinder 21, together with the second component of the elastic mechanism, is rotatable relative to the housing 20 and thus forms the output of the elastic mechanism.

[0050] This causes the rollers 3, the joints of the first lever arms 9, and the second end of the compression spring 6 to move away from the control disc 1 when the control disc 1 rotates. Simultaneously, the connecting part 5, and thus the first end of the compression spring 6, is moved towards the control disc 1. The compression spring 6 is compressed. The stiffness of the mechanism can be adjusted using the movable pivots 11. This adjustment results in a change in compliance, which is generated by greater compression of the compression spring 6. The frame 14 can advantageously be connected to the cylinder 21 as the output via a rotationally fixed guide, so that the frame 14, as part of the output, is movable towards or away from the disc 13.

[0051] Furthermore, the first drive 18, the control disk 1, the second drive 19, the disk 13, the first drive 18 can each be connected individually or in combination with a rotary encoder or encoders, which may advantageously be connected with a control device for a specific adjustment of the stiffness.

Claims

1. Nonlinear elastic joint with an elastic mechanism and actuators (18, 19), wherein a control disc (1) as a first component of the elastic mechanism is connected to a first actuator (18), wherein the control disc (1) has, on at least one circular path, recesses (8) or elevations arranged spaced apart from one another, wherein the recesses (8) or elevations form paths for respective rollers, in that the rollers are pivotably connected to first lever arms (9) of two-sided levers (4), in that second lever arms (10) of the two-sided levers (4) are pivotably connected via a connecting part (5) to a first end of a compression spring (6), in that a second end of the compression spring (6) is connected to the rollers and the first lever arms (9), and in that pivots (11) of the two-sided levers (4) are coupled to an adjustment mechanism (12) with a second actuator (19) for changing the position of the pivots (11) parallel to the control disc (1) and thereby the stiffness, such that, by actuating the control disc (1), the rollers, the joints of the first lever arms (9) and the second end of the compression spring (6) are moved away from the control disc (1), while simultaneously the connecting part (5), and thereby the first end of the compression spring (6), is moved towards the control disc (1), wherein by means of the displaceable pivot (11) a change in the amount of compression of the compression spring (6) is generated, wherein a second component of the elastic mechanism comprises the rollers, the connecting part (5), the two-sided levers (4), the compression spring (6) and the adjustment mechanism (12), and the second component of the elastic mechanism is the output of the nonlinear elastic joint.

2. Nonlinear elastic joint according to claim 1, characterized in that the recesses (8) or elevations have an arc shape, or in that the cross-sections of the recesses (8) or elevations are circular segments.

3. Nonlinear elastic joint according to claim 1 or 2, characterized in that the compression spring (6) is arranged at least in sections in a pot-shaped body (7) with a rim, wherein the second component of the elastic mechanism comprises the pot-shaped body (7), wherein the second end of the compression spring (6) is located on the bottom of the pot, and that the rollers and the first lever arms (9) are connected to the rim of the pot-shaped body (7).

4. Nonlinear elastic joint according to any one of claims 1 to 3, characterized in that the compression spring (6) is a helical compression spring.

5. Nonlinear elastic joint according to any one of claims 1 to 4, characterized in that the adjustment mechanism (12) comprises a disc (13) with openings (17) for guiding the pivots (11).

6. Nonlinear elastic joint according to claim 5, characterized in that the adjustment mechanism (12) comprises the second actuator (19) either with a worm shaft or in connection with a worm shaft, and in that the disc (13) is or comprises a worm wheel.

7. Nonlinear elastic joint according to any one of claims 1 to 6, characterized in that the first component of the elastic mechanism and the first actuator (18) are components of a pot-shaped housing (20), wherein at least a portion of the rotatably mounted control disc (1) is the bottom of the pot-shaped housing (20), that the rollers, the connecting part (5), the two-sided levers (4), the compression spring (6), the pot-shaped body (7), and at least the disc (13) of the adjustment mechanism (12) are parts of a cylinder (21), which is arranged at least in sections in the pot-shaped housing (20).

8. Nonlinear elastic joint according to at least one of claims 1 to 7, characterized in that the rollers, in connection with the first lever arms (9), are trolley rollers (2) each comprising a frame (14) and a therein mounted roller (3), that the frames (14) are pivotably connected to the first lever arms (9) of the two-sided levers (4), and that the second end of the compression spring (6) is connected to the first lever arms (9) and the frames (14) of the trolley rollers (2).

9. Nonlinear elastic joint according to at least one of claims 1 to 8, characterized in that the first actuator (18), the control disc (1), the second actuator (19), the disc (13), and / or the first actuator (18) are each connected individually or in combination with a rotary encoder or rotary encoders.

10. Nonlinear elastic joint according to claim 9, characterized in that the rotary encoder or the rotary encoders is or are connected to a control device.

11. Nonlinear elastic joint according to at least one of claims 1 to 10, characterized in that the output is connected to a link of a robot, or in that the first actuator, in connection with the control disc, and the output are each connected to a link of a robot.