EP3148757A1

EP3148757A1 - Device and method for compensating the gravitational force

Info

Publication number: EP3148757A1
Application number: EP15728438.1A
Authority: EP
Inventors: Franz Ehrenleitner
Original assignee: Huber Diffraktionstechnik GmbH and Co KG
Current assignee: Huber Diffraktionstechnik GmbH and Co KG
Priority date: 2014-06-02
Filing date: 2015-05-27
Publication date: 2017-04-05
Also published as: US10500725B2; US20170113347A1; WO2015185397A1; DE102014210348A1

Abstract

The invention relates to a method and a device (1) for compensating the gravitational force (G) acting on a manipulator (2), generating a variable counterforce (F), the counterforce generated (F) being applied to the manipulator (2) by a kinematic assistance system (12) which contacts the manipulator at a force application region (22), a value of the counterforce (F) corresponding at least essentially to a value of the gravitational force (G) acting upon the force application region due to gravitational acceleration, the counterforce (F) being at least essentially oriented in a parallel and opposite direction to the gravitational acceleration. The invention further relates to a system comprising a device (1) and a manipulator (2).

Description

Device and method for compensating the weight

Field of application and state of the art

The application relates to a method and a device for compensating the weight force on a manipulator.

As a manipulator in connection with the application, a device or machine is understood which has a series of largely rigid components, which are connected by joints. Manipulators serve the purpose of gripping or picking up, positioning and / or moving loads such as tools or workpieces, measuring devices or other objects and / or humans or animals. The components are referred to as arms or links. A manipulator usually has a plurality of degrees of freedom. The joints can have both rotational and translatory degrees of freedom. The entirety of the links and the joints is referred to in connection with the application as kinematics of the manipulator.

For example, the use of manipulators is known as a goniometer. In this case, the transducers and samples are positioned in the room by different manipulators and measured in different solid angles. For a precise measurement, it is necessary that the measuring center is maintained as accurately as possible at a desired angle change of the sample. To achieve the required precision, a minimum eccentricity of the axes of rotation is first required.

The weight force influences the behavior of the manipulator, whereby the influence of the weight force is inter alia also dependent on the orientation of the manipulator. In order to minimize an influence of the weight of the manipulator and possibly a recorded load on a positioning, it is known to design the kinematics of the manipulator as stiff as possible, so that a deflection of the links due to the weight is as low as possible.

Alternatively or additionally, it is known from DE 10 2009 035 877 A1 to provide a compensating actuator for performing translatory compensation movements in a first, in a second spatial direction, and preferably also in a third spatial direction. The compensating actuator comprises a movement unit translatable in the first and second, preferably also in the third spatial direction, at least one actuator The first solid-body joint assembly with a mechanically coupled to the movement unit, a first simple lever forming the first Festkorpergelenkanordnung, wherein by means of the at least one actuator, the first Festkorpergelenkanordnung deflectable and thus due to this first coupling, the movement unit is translationally deflected in the first spatial direction, and a second solid-body hinge assembly with a mechanically coupled to the movement unit and / or the first solid-state joint assembly, a toggle lever forming second Festkorpergelenkanordnung, wherein by means of the at least one actuator, the second Festkorpergelenkanordnung deflectable and thus the movement unit is translationally deflected in the second spatial direction due to this second coupling. By Ausgleichsaktorik a high positioning accuracy should be achieved.

It is also known to apply a moment to compensate for the weight on the limbs of the manipulator, which counteracts a load on the members due to the weight. For example, from WO 2007/054327 a holding device for a medical-optical instrument with a support arm for receiving a load is known, wherein the support arm is pivotally mounted in a first pivot relative to a holding unit. The holding device comprises means, in particular spring elements, for generating a longitudinal force which acts on the support arm to compensate for a load torque occurring in the first pivot of the support arm, wherein the means for generating a longitudinal force is pivotally mounted on the support unit and a force a cam carrier exerts, which is in operative connection with the support arm. The pivotal mounting is to ensure that the weight of the means for generating the longitudinal force is not loaded on the support arm and thus the means for generating the longitudinal force to compensate for a load torque in the pivot joints of the support arm does not have to compensate its own weight.

TASK AND SOLUTION

It is an object of the invention to provide a method and a device for compensating the weight force on a manipulator, wherein a compensation is certainly possible regardless of a position of the manipulator.

This object is achieved by a method having the features of claim 1, a device having the features of claim 2 and a system having the features of claim 1. Further advantages will be apparent from the subclaims. According to a first aspect, a method is provided for compensating the weight force on a manipulator, wherein a variable counterforce is generated and the generated counterforce is applied to the manipulator by means of a support kinematics contacting the manipulator in a force application area. The variable counterforce is chosen such that an amount of the counterforce corresponds at least substantially to an amount of the force acting on the force application area due to the gravitational acceleration and the counterforce is directed at least substantially parallel and oppositely to the gravitational acceleration.

According to a second aspect, a device for compensating the weight force is provided on a manipulator, comprising a force generating arrangement, by means of which a variable reaction force can be generated, and a support kinematics, wherein the manipulator can be acted upon by the support kinematics in at least one force application area with the generated counterforce and an amount of the counterforce corresponds at least substantially to an amount of the force acting on the force application area due to the gravitational acceleration and the counterforce is directed at least substantially parallel and oppositely to the gravitational acceleration.

By applying a counter force by means of a support kinematics, it is possible to counteract a deformation of the manipulator due to the gravitational acceleration. This ensures that the manipulator is supported, while a kinematic over-determination, which would result from a support by means of a stationary support, is avoided. The transmission kinematics is suitably designed depending on the available space or other requirements. The necessary force is preferably generated by means of a spring arrangement. Alternatively, a power generation by means of other devices, which allows a constant force generation, such as magnets, pneumatic devices, engine torque controls or the like, conceivable. The counterforce preferably takes into account all the relevant masses of the manipulator and a possibly recorded load. The support kinematics may have a low inherent rigidity, as long as it is ensured that the force is conducted to the force application area.

In advantageous embodiments, the support kinematics has at least one support section, by means of which the support kinematics contacts the manipulator in the at least one force application region. The at least one support section contacts the manipulator at a location suitable for this purpose. In advantageous embodiments, it is provided that the support portion of the manipulator at an effective range, ie at a free end or contacted to a recorded load. As a result, an effect of the positioning inaccuracy due to the weight force in the relevant region can be reduced particularly advantageously. However, it is also conceivable to support a manipulator with a plurality of links on one of the links by means of the counterforce.

In advantageous embodiments, all three translatory degrees of freedom are bound to the support section.

In a further development it is provided that the support kinematics comprises a base and at least two links, wherein the force generation arrangement is arranged on the base and the support kinematics directs the counterforce to the at least one support section. The limbs are coupled with each other and with the base via joints, in particular rotary joints.

As mentioned, all three translatory degrees of freedom are bound to the support section in advantageous embodiments. For this purpose, it is provided in one embodiment that the links of the support kinematics are arranged pivotable about a common, virtual pivot point, wherein the support section lies in the virtual pivot point. On the support kinematics applied weight forces therefore do not lead to a shift in the support kinematics, but are compensated by the applied counterforce.

Alternatively, it is provided that at least one joint of the support kinematics is associated with an additional drive. By means of the at least one additional drive, the support kinematics is held in a desired position, wherein the counterforce for a compensation of the weight force by means of the force generating arrangement is applied.

In advantageous embodiments, all three rotational degrees of freedom are bound to the base. By means of the force generation arrangement, therefore, no rotational movements are introduced into the support kinematics.

In advantageous embodiments, it is provided that the support kinematics is designed according to a kinematics of the manipulator and is arranged in or on the kinematics of the manipulator. This ensures that the support kinematics does not hinder the manipulator in its movement and / or does not obstruct a working space of the manipulator. For a movement of the support kinematics with the manipulator, the support kinematics in one embodiment driving elements for coupling with the manipulator. The support kinematics preferably has a low weight and joints with low friction, so that no or only small additional forces are necessary for a movement of the support kinematics.

Finally, the problem is also solved by a system comprising a manipulator and a device according to the invention.

In one embodiment, the manipulator comprises two members, which are arranged around two at an angle of about 0 ° to about 90 ° to each other arranged axes, in particular two at an angle of about 5 ° to about 90 ° to each other, each other in one common virtual pivot intersecting axes, are pivoted. The manipulator has a high positioning accuracy and can be used for example as a goniometer. By means of the support kinematics, a displacement of the manipulator resulting from the gravitational acceleration, in particular at its active section, is prevented or at least further reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and aspects of the invention will become apparent from the claims and from the following description of preferred embodiments of the invention, which are explained below with reference to the figures. Here are shown schematically:

1 shows a device for compensating the weight force on a manipulator according to a first embodiment;

2 shows a system comprising a device and a manipulator according to a second exemplary embodiment in a perspective view;

FIG. 3 shows the system according to FIG. 2 in a side view; FIG.

4 shows the system according to FIG. 2 in a sectional side view;

5 shows the device for the system according to FIG. 2 in a perspective representation;

FIG. 6 shows a detail VI according to FIG. 5; FIG. FIG. 7 shows a system comprising a device and a manipulator according to a third exemplary embodiment in a sectional side view similar to FIG. 4; FIG.

FIG. 8 shows the device for the system according to FIG. 7 in a perspective view; FIG.

9 shows a system comprising a device and a manipulator according to a fourth exemplary embodiment in a sectional side view similar to FIG. 4;

Fig. 10 shows the device for the system of FIG. 9 in a perspective view and

FIG. 11 shows a detail XI according to FIG. 10.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 shows a first embodiment of a device 1 for compensating the weight on a manipulator 2, wherein only one member 20 is shown by the manipulator. The weight 20 acts on the member 20.

The device 1 comprises a force generating arrangement 10, by means of which a variable reaction force F can be generated. The illustrated force generating assembly 10 is designed as a spring arrangement. The device 1 further comprises a support kinematics 12, wherein the manipulator 2 on the member 20 by means of the support kinematics 12 in a force application region 22 with the generated counterforce F can be acted upon. An amount of the counterforce F corresponds at least substantially to an amount of the weight force G acting on the force application area due to the gravitational acceleration, but the counterforce F is directed counter to the gravitational acceleration. A force application region 22 is selected such that the applied counterforce F passes through the center of gravity of the member 20 or the relevant masses of the manipulator 2 in its current position, so that no moments are entered. If a force application region 22 is not selectable in such a way that the counterforce acting on the manipulator 2 passes through the center of gravity, in an alternative embodiment torque-free support is provided by means of a support kinematics which contacts the manipulator 2 in two force application regions. The support kinematics 12 has a support section 120, with which it contacts the manipulator in a force application region 22. In the illustrated embodiment, a cylindrical support portion 120 is provided. Preferably, a spherical support portion 120 is provided for a punctiform contact.

The support kinematics 12 includes a base 122 on which the force generating assembly is disposed. The base 122 is supported by means of a bearing assembly 14 such that all three rotational degrees of freedom are locked. In addition, the translational degrees of freedom in the plane perpendicular to the gravitational acceleration (z and x direction in the illustration) are blocked. A movement parallel to the gravitational acceleration (y-direction in the illustration), however, is possible for a force introduction. 2 to 4 show a system 3 comprising a device 1 and a manipulator 2 according to a second embodiment in a perspective view, a side view and a sectional side view. FIG. 5 shows the device 1 for the system 3 and FIG. 6 shows a detail VI according to FIG. 5.

2 to 4 comprises two members 24, 26, which are arranged about two axes A1, which are arranged at an angle of approximately 60 ° to one another and which intersect in a common virtual pivot P (see FIG. A2 are pivotable. In other embodiments, the axes are arranged at a different angle to each other. The first member 24 is L-shaped with two legs 240, 241. The first leg 240 is coupled to a foundation, not shown, so that the member 24 about a horizontal axis A1 (x-axis in Fig. 2) is pivotable. The second member 26 is disposed on the second leg 241 and pivotable about the axis A2. The manipulator 2 is designed such that a pivoting about the axes A1 and A2 in each case by 360 ° is possible. The second member 26 is V-shaped. On the second member 26, a load to be positioned 28 is arranged. The load 28 is arranged in the virtual pivot point P and changes its orientation in space during a movement of the manipulator 2, but not its position.

Depending on the application, very high positioning accuracies are required. Thus, applications are known in which a maximum deviation of the position at a recorded load of 5 kg 50 μηη. Due to a mass of the members 24, 26 and the load 28 may cause deformation and thus positioning inaccuracies.

According to the invention, a device 1 with a force-generating arrangement 10 and a support kinematics 12 is provided, which acts on the manipulator 2 with an opposing force. The illustrated support kinematics 12 is constructed in accordance with the manipulator 2 and also includes two members 124, 126. The support kinematics 12 is shown in FIG arranged the manipulator 2 and is moved with this. The second member 126 is coupled at its free end to the load 28 by means of a support portion, not shown, so that the load 28 is acted upon in the virtual pivot point P by means of the counterforce in a force application region 22. All three translational degrees of freedom are bound to the support section arranged in the virtual pivot P.

As best seen in FIG. 5, the support kinematics 12 further includes a base 128 in addition to the two members 124, 126. The force generating assembly 10 is disposed on the base 128. The support kinematics 12 directs the counterforce to the support section. The base 128 is supported by means of a bearing assembly 14 on the foundation of the manipulator 2, not shown. On the support kinematics 12 further preferably not shown driver or the like are provided, so that the movement of the manipulator is transferable to the support kinematics. The joints of the support kinematics 12 are preferably low friction, so that only low frictional forces are opposed to the movement.

The bearing assembly 14 is shown in detail in FIG. The illustrated bearing assembly 14 is designed as a so-called delta kinematics. A delta kinematics is a parallel kinematics comprising a working body and a base body, in which the working body is movable relative to the main body in all three translational degrees of freedom, while all three rotational degrees of freedom are locked. As a result of the bearing arrangement 14, movements of the base 128 in all three rotational degrees of freedom are blocked. Movement of the base 128 in the z and x directions is permitted to avoid tension. The movement in the y-direction is used for the introduction of force.

7 shows a system 3 comprising a device 1 and a manipulator 2 according to a third exemplary embodiment in a sectional side view similar to FIG. 4. FIG. 8 shows the device 1 for the system 3 according to FIG. 7 in a perspective view. The system 3 is similar to the system 3 shown in FIGS. 2 to 6, and the same or similar components use the same reference numerals.

The manipulator 2 is identical in construction to the manipulator according to FIGS. 2 to 4. However, the device 1 is designed such that the counterforce is not applied in the region of the virtual pivot, but on a leg 260 of the second member 26. The support kinematics 12 comprises a support section 129, by means of which it makes contact with the second leg 260 at the force application region 22. The support portion 129 is designed as a ball joint.

In order to bind all three translational degrees of freedom to the support section 129, which is arranged at a location suitably selected by space requirements or the like, a drive 16 is provided at each of the two joints, which act as brakes and apply moments which correspond to a displacement of the support section 129 counter. However, the drives 16 do not serve to position the links 24, 26 of the manipulator 2.

In Figs. 7 and 8, a real ball joint is provided as the support portion 129. However, embodiments are also conceivable in which the real ball joint is replaced by a virtual ball joint. 9 shows a system 3 comprising a device 1 and a manipulator 2 according to a fourth exemplary embodiment in a sectional side view similar to FIG. 4. FIG. 10 shows the device 1 for the system 3 according to FIG. 9 in a perspective illustration and FIG. FIG. 1 shows a detail XI according to FIG. 10. The system 3 is similar to the system 3 according to FIGS. 2 to 6 and the same or similar components use the same reference numbers. In particular, the manipulator 2 is identical to the manipulator according to FIGS. 2 to 4.

In contrast to the previous embodiments, a force transmission takes place on a virtual ball joint whose center forms a momentary pole M for the application of force to the manipulator 2. The virtual ball joint includes three rods 127, with axes of the rods 127 intersecting in the instantaneous pole M. The position of the instantaneous pole M is selected in advantageous embodiments such that the position corresponds to the center of gravity of the manipulator 2. In order to take into account changes in the position of the center of gravity during a movement of the manipulator 2, the rods 127 are arranged by means of ball joints on the member 126 of the support kinematics 12 in the illustrated embodiment. In other embodiments, the rods 127 are integrally or monolithically connected to a member, wherein - depending on the design of the manipulator 2 and the support kinematics - the deviations between the position of the instantaneous center M and the position of the center of gravity are negligibly small. The free ends of the rods 127 contact the manipulator 2 and serve as real support portions 129. In order to bind all three translatory degrees of freedom at the instantaneous pole M analogous to FIGS. 7 and 8, in one embodiment at the two joints each have a drive 16 provided, which act as brakes and apply torques, which are opposed to a displacement of the instantaneous center M.

Claims

claims

1 . Method for compensating the weight force (G) on a manipulator (2), wherein a variable counterforce (F) is generated, wherein the counterforce (F) generated on the manipulator (2) by means of a manipulator (2) in at least one force application area ( 22) contacting support kinematics (12) is applied, and wherein an amount of the counterforce (G) at least substantially equal to an amount of force acting on the force application area weight force (G) due to the gravitational acceleration and the counterforce (F) at least substantially parallel and opposite to Gravity directed.

2. A device for compensating the weight force (G) on a manipulator (2) comprising a force generating arrangement (10) by means of a variable counterforce (F) can be generated, and a support kinematics (12), wherein the manipulator (2) by means of the support kinematics (12) in at least one force application region (22) with the generated counterforce (F) can be acted upon and wherein an amount of the counterforce (F) at least substantially an amount of force due to the gravitational acceleration at the force application region (22) weight force (G) corresponds and the counterforce (F) is at least substantially parallel and directed counter to the gravitational acceleration.

3. A device according to claim 2, characterized in that the support kinematics (12) at least one support portion (120, 129), by means of which the support kinematics (12) contacts the manipulator in the at least one force application region (22).

4. Apparatus according to claim 3, characterized in that on the support portion (129) all three translational degrees of freedom are bound.

5. Apparatus according to claim 3 or 4, characterized in that the support kinematics (12) comprises a base (128) and at least two members (124, 126), wherein the force generating arrangement is arranged on the base and the support kinematics the counterforce to the at least a support portion (129) passes.

6. Apparatus according to claim 5, characterized in that the members are arranged pivotable about a common, virtual pivot point (P), wherein the support portion in the virtual pivot point (P).

7. The device according to claim 5, characterized in that at least one joint of the support kinematics (12) is associated with an additional drive (16).

8. Device according to one of claims 5 to 7, characterized in that at the base (128) all three rotational degrees of freedom are bound.

9. Device according to one of claims 2 to 8, characterized in that the support kinematics (12) is designed according to a kinematics of the manipulator (2) and is arranged in or on the kinematics of the manipulator (2).

10. The device according to claim 9, characterized in that the support kinematics (12) comprises entrainment elements for coupling with the manipulator.

1 1. System comprising a manipulator (2) and a device (1) according to one of claims 2 to 11.

12. System according to claim 1 1, wherein the manipulator (2) comprises two members which are arranged at two at an angle of about 0 ° to about 90 ° to each other arranged axes (A1 A2), in particular two at an angle of about 5 ° to about 90 ° to each other, each other in a common virtual pivot point (P) intersecting axes (A1 A2), are pivotable.