DE102009007181A1 - Method for inputting commands into controller of e.g. multi-axis robot, involves comparing detected force with stored force, and outputting commands associated with stored force to controller if detected force corresponds to stored force - Google Patents

Abstract

The method involves detecting a force that acts on a manipulator in a direction. The detected force is compared with stored force in a command input mode, where a command is assigned to the stored force. The commands associated with the stored force are outputted to a controller of the manipulator if the detected force corresponds to the stored force. The command input mode is activated by pressing an input device. Movement of the manipulator is compared with stored movements in the command input mode. An independent claim is also included for a device for inputting commands into a control of a manipulator.

Description

The The present invention relates to a method for tracing a predetermined path through an end effector of a manipulator, in particular one Robot, a control device for carrying out such a method and a manipulator, in particular a robot, with such Control device.

A typical task of a manipulator is with its end effector to depart a predetermined path. It can, for example, the train through direct programming, i. e. manual guiding the end effector in desired Laying in a learning mode, or through indirect programming ("off-line programming "), i. e. the creation of desired gradients of joint angles accordingly the inverse kinematics of the desired End effector layers have been specified.

The position includes a position and / or orientation of the end effector, which can be described for example by a vector x ∈ R ⁿ of dimension n. The path of the end effector can then be parameterized, for example, via a path parameter s (x = x (s)) which the manipulator executes in normal operation according to a time profile ds / dt (t), so that the end effector processes the path with a corresponding path velocity dx / dt leaves.

There Manipulators, in particular industrial and lightweight robots such as the robots of the LBR I-IV series of the German Aerospace Center Aerospace (DLR), very fast in normal operation can and this is a direct examination of a train or a timely one Manual emergency stop is difficult for faulty railways, it is internal to the company already known, the web speed during the departure of the train manually by an operator to change For example, to reduce to investigate certain sections of track or to check the interaction with other manipulators. On the other side can through targeted enlargement of the Web speed over the Normal operation also advantageously successively the dynamic Limits of the manipulator are tested.

So far will this change the web speed during operation ("override") manually by a control on a control board in the controller entered by the manipulator. However, this is awkward in particular, if an operator, for example, a joining process Close up of a robot investigate and reduce the web speed accordingly want. Because in this case he has to control the operating element with one hand actuate.

Additionally or As an alternative to web speed, it may be desirable to include other process variables of the Manipulator and / or the process carried out by him to change. So for example, when directly programming a joint or welding process a pressure force of the manipulator or a welding current be adjustable by the operator an operating point.

task Therefore, the present invention is a more comfortable change to allow at least one process variable.

These The object is achieved by a method according to claim 1. claim 13 shows an apparatus for carrying out a method according to the invention, Claim 15, a manipulator with such a control device under protection.

One Manipulator points a predetermined path of its end effector a solution space which encompasses all manipulator positions, the same end effector position assigned. The manipulator can not have an end effector posture represent, the solution space degenerates to the empty amount. For example, is a three-dimensional position and orientation of the end effector in the space, each by three coordinates, about Cartesian or polar coordinates or Euler or gimbal angle can be described by a six-axis manipulator one-to-one feasible, contains the solution space accordingly only one position.

However, if the number f of the degrees of freedom of a manipulator exceeds the dimension n of the predetermined position of the end effector by at least 1 (f> n), this manipulator is redundant with respect to this predetermined path, possibly multiple times, ie its solution space comprises at least two manipulator positions assigned to the same end effector position. Such a solution space extended by multiple positions is referred to below as "zero space". On the one hand, this can result from the fact that the manipulator has seven or more degrees of freedom, such as the above-mentioned lightweight robot LBR III or IV of the DLR. On the other hand, the dimension n of the predetermined position of the end effector may also be less than six, if, for example, the orientation of the end effector with respect to a spatial axis does not matter, for example when drilling in the direction of the last axis of rotation of a six-armed industrial robot. In this case, the manipulator is task redundant with respect to the path and contains infinitely many manipulator positions assigned to the same end effector position x ∈ R ⁵ .

The basis of the present invention ing idea is to exploit such a redundancy of a manipulator to change or specify one or more process variables of the manipulator.

there can they be process variables determine a process performed by the manipulator. For example, the welding current is one from the manipulator while a welding process out welding gun and whose web speed determines (with) the welding process Process variables. In a joining process For example, represents the pressure force with which the manipulator a workpiece adds, one the joining process (with) determining process variable. In a painting process in turn set the web speed the end effector of the manipulator and the color output the painting process (with) determining process variables. In the following, the present invention is based on the web speed as an example for one to be changed Process variable explained in more detail. The however, the present invention is not limited thereto, but rather can be any Process variables are changed. The term "process variable" in the sense The present invention therefore includes any, especially physical, Size that by a user in connection with a manipulator. or changeable is, for example, the brightness of a light source, that of the manipulator is worn and / or illuminates the work area, a temperature a working cell of the manipulator, an optical and / or acoustic Display or the like.

In a preferred embodiment According to the present invention, the end effector is constituted by a control device according to the invention in a conventional manner always in the predetermined position accordingly the predetermined path moves. For this purpose, the control device for example, have a corresponding position control for the end effector. In the present case, the term "control" therefore also includes a regulation i. e. an output of control variables below consideration of nominal and actual sizes and a control difference between these.

Also at change the manipulator position in zero space by an operator can thereby continue to follow the predetermined path. These are different versions known from admittance regulations and impedance regulations, the one Allow movement of the manipulator by the operator. For example a six-armed industrial robot with its end effector a train nachfahren, in which the orientation of the end effector with respect last rotation axis of the robot is not specified, a position control for this Rotary axis by appropriate choice of the proportionality factor a pure proportional controller are switched so soft that an operator can manually rotate the end effector around this axis. Does that drive The aforementioned seven-axis LBR III trajectory may include Users with appropriate admittance control, for example the Manually push elbows out of its position, taking the admittance control the end effector continues in one by three position and three Angular coordinates uniquely predetermined position along the given Train leads. Such a movement of the manipulator by the operator thus leads always to a filing of the manipulator in its zero space, i. e. a difference between two manipulator positions of the null space.

According to the invention will now when traveling a predetermined path through an end effector of a Manipulator referring to the predetermined path a null space with at least two of the same Endeffektorlage having associated manipulator positions, i. e. regarding the predetermined path is redundant, a filing of the manipulator in the zero space detected and at least one process variable, for example the web speed of the end effector corresponding to the detected Filing changed.

hereby can therefore, without the position of the end effector with respect to the trajectory to change, the process size to simple and changed direct way be by the storage of the manipulator in the zero space as a measure of desired process variable change is being used. The operator can touch the manipulator directly and has to process variable change do not operate an operating element of a control board or the like.

A such command input can advantageously be operated intuitively. For example, moving the manipulator in the direction of Train to increase speed reduce or even change their sign, so that the end effector moves backwards on the given path. Likewise for example, pressing of the elbow of the LBR III or turning an end flange of a Industrial robot in its last swivel in one direction one Speed or Pressure increase, pulling in the opposite direction cause a decrease in the web speed or the pressing force.

The change of the web speed dx / dt can be realized in different ways. For example, in order to increase the speed, a predefined speed trapezoidal profile ds / dt (s) can be proportionately shortened in the direction of the time axis and stretched for speed reduction. Similarly, a simple proportional-derivative control, the next to be approached position of the given path early or spä ter be supplied as a setpoint to increase or reduce the speed.

Prefers For each Endeffektorlage the predetermined path is one of the manipulator positions of the Nullraumes as a target manipulator position specified. For this purpose, for example, in the railway planning a the manipulator positions of the null space correspondingly suitable Criteria selected be, such as the manipulator position whose start a minimal Time or energy required, or their difference to one previous position is the lowest. The latter criterion may, for example, an undesired jump between different robot positions when approaching the next position avoid. In direct programming by manually guiding the Manipulator ("direct teaching ") if the nominal position results automatically from the respective position, in which the operator brings the manipulator while teaching.

When Filing can then be the difference between this setpoint and the actual one Manipulator position are detected. If the manipulator by the Operator moved from its nominal position, this leads to a corresponding permanent storage, as long as the manipulator is not back in the desired position is. For example, is a certain, constant angular position of the end effector of a six-axis robot with respect to it given last axis of rotation as a target position, so leads a permanent twisting of the end effector in this axis of rotation the operator to a constant filing and a corresponding change the process size, for example the web speed.

The Process size can in a first embodiment correspond to the present invention, the detected storage, for example be proportional to this. For this purpose, a specific size of the tray, for example, the amount of a difference vector of the joint angle be assigned to the manipulator a corresponding process size. Im above example mentioned may be about the web speed through the angular position of the end effector, i. e. corresponds to every angle a certain speed dx / dt.

In a second embodiment can be a specific size of the tray instead, a change as well assigned to the process variable so that the manipulator, for example, his speed elevated, as long as an operator creates a tray. Again, the change proportional to the filing, i. e. larger shelves change the process size more. A return to the original Process size required in this case, unlike the first embodiment, not just a return the filing, but in addition a subsequent one Storage in the opposite direction.

There the storage, in particular of a nominal position unknown to the operator, is recognized by this difficult intuitive, is advantageously a Control to reduce the filing performed. The operator leaves the manipulator go, this returns then as a result of the scheme independently in his Reference position in zero space back. This is on the one hand advantageous if the debit positions, for example specified for collision avoidance of the redundant manipulator become. On the other hand, it simplifies the second one described above Execution, because the manipulator returns to its nominal position in null space, if the operator no longer exerts any force on him, so that the process size as long changed is active as long as the operator from the manipulator in the null space moves its nominal position, and then the manipulator with the changed one Process size continues.

alternative can also be a regulation being a user-changed position is based in zero space as a new setpoint. This is special advantageous in connection with the first embodiment described above, in which the operator by selecting one of the possible manipulator positions specify a process variable in zero space can. You can do this for example, based on a mathematical replacement model of the manipulator and the new, given by the operator manipulator position motor moments calculated and supplied as nominal values of a force control, substantially compensate for weight, friction and / or dynamic forces and hold the manipulator in the new predetermined position.

Prefers becomes the process size, for example the web speed according to a size and / or direction of the detected Filing changed. A change according to the magnitude, for example the amount of a difference vector in the joint angles, allows the shutdown the web at different speeds, intuitive by the operator by larger or smaller Trays can be specified. A change according to the direction allows in particular a departure of the predetermined path in the reverse direction.

Of the Manipulator can leave the predetermined path position-controlled. For this can For example, the desired positions in the zero space to be specified and by Proportional differential integral (PID) controller successively be approached.

Likewise, the manipulator can also be force-controlled. For example, this can be done calculated on the basis of a mathematical replacement model of the manipulator for driving the predetermined paths required torques in the motors of the manipulator and fed as set values force regulators of the motors.

Either with position-controlled and force-controlled manipulators, it is advantageous to regulate this yielding, so that an operator can manually adjust the position of the Change Manipulator in Null Space can. This can, for example, in conventional industrial robots with PID single-joint control by reducing the proportional component and deactivating the integral controller can be realized. For force-controlled manipulators can Force regulators of the engine setpoints are given, which are essentially only the inertia, Friction and weight forces of the manipulator.

The Storage can be based on movements and / or forces in joints of the manipulator be recorded. As a rule, the axes of motion have a Manipulator over a position detection, for example via encoders or the like. Based on the change in the individual joints can then be a filing of the manipulator be detected in the null space. Likewise, provided appropriate force sensors are present, forces an operator applies the manipulator to him to move in its null space. In the present case opposing pairs of forces, i. e. Generalizing torques also referred to as forces.

In a preferred embodiment The present invention provides a guide handle which fixed or detachable attached to the manipulator. At this guide handle can be an operator specifically cause a storage of the manipulator in its zero space, by moving the manipulator by means of the guide handle. By such a leadership becomes an attack option created, which intuitively clarifies the operator, where and in which direction he has to move the manipulator to create a tray. Prefers can in the guide handle Be provided controls, such as a security element, that actively must be operated to a procedure of the manipulator, a movement of the manipulator in neutral space by the operator, or a manual change of To allow process size.

Further Objects, features and advantages emerge from the dependent claims and the following embodiments. This shows, partially schematized:

1 a six-axis manipulator according to an embodiment of the present invention;

2 a seven-axis manipulator according to another embodiment of the present invention.

3 a lightweight robot according to another embodiment of the present invention; and

4 a flowchart of a method according to an embodiment of the present invention.

1 shows a manipulator in the form of a six-axis robot 1 according to an embodiment of the present invention. Its position is described by the joint angles q = [q1, q2, ... q6].

The end effector of the robot 1 , symbolized by the tool center point TCP, is to descend a given horizontal trajectory x (s), which in 1 is indicated by dashed lines. In this case, the angle q6 of the end effector TOP is not predetermined, since a tool attached thereto (not shown) is rotationally symmetrical to the sixth, last movement axis of the robot 1 is. The position x ∈ R ^{5 of} the end effector TOP can therefore be determined, for example, by three Cartesian coordinates and the two angles to the plane of the drawing or to the horizontal in the plane of the drawing 1 to be discribed.

The six-axis robot 1 is therefore redundant with respect to the given path x (s). I. e., He can a predetermined position x (s) of the end effector TOP, which is determined only by the joint angle q1, ... q5, by infinitely many different manipulator positions [q1, ... q5, q6 ∈ [0, 2π]), which emerge apart by rotation of the end effector TOP about the sixth axis of movement and together the zero space of the robot 1 form x (s) with respect to the given path.

Two of these manipulator positions, which are all associated with the same end effector position, are in 1 shown. In this case, a first position q is pulled through, a second position q 'shown by dashed lines. Each position is described by a vector of joint angles: q = [q1, q2, ... q6 = 0]; q '= [q1', q2 ', ... q6' = π].

As nominal position qsoll in null space is the in 1 solid position (q6 = 0) given because the end effector TOP was performed accordingly during teaching.

By default, the robot travels the predetermined path x (s) with its end effector TOP in operation at a constant speed dx / dt = v. For this purpose, proportional integral controllers (not shown) are supplied with new setpoint values q1soll, ... q5soll every 10 ms for the first five axes of motion leads, so the robot 1 each moved to the new position q while its end effector TOP along the path x (s) moves.

Of the sixth axis is a pure proportional controller (not shown) switched, whose proportionality constant is chosen so low that an operator manually the end effector TOP around the sixth axis of movement can twist.

In a control device (not shown) of the robot 1 Among other things, the joint angle q6 is detected. Now the operator twists the end effector TOP, while the robot 1 If the path x (s) leaves, the control device records the bin qist - qsoll, which forms a vector [0,... 0, q6act-q6set] in the exemplary embodiment. Whose amount | q6is - q6soll | is linearly scaled so that a rotation from the target position by 0 ° corresponds to a factor K = 1, a rotation by + 180 ° to a factor K = 2 and a rotation by -180 ° to a factor K = 0. The control device now moves the end effector at a constant speed K × v, for example, at K = 2, supplying the regulators for the first five axes of movement every 5 ms with the next setpoint values q1soll, ... q5soll. If the operator twists the end effector by -180 °, the robot stops 1 the end effector TOP at times completely. If the operator twists the end effector even further, for example by a total of 360 °, the end effector TOP moves the predetermined path x (s) backwards at the speed -v, by reversing the already traveled desired positions in reverse for the first five movement axes every 10 ms Sequence successively as new setpoints are specified.

Leaves the Operator loses the end effector TOP, the proportional controller rotates for the sixth Axis the end effector back to the desired position q6soll = 0, the control device changes the Path speed accordingly back to v, since the factor K on 1 goes back.

2 shows in 1 corresponding representation of a manipulator in the form of a seven-axis robot 1 according to another embodiment of the present invention. Its position is described by the joint angles q = [q1, q2, ... q7]. In this case, the execution according to 1 corresponding elements are denoted by the same reference numerals, so that reference may be made to the above statements to explain them and will be discussed below only on the distinction.

In the further embodiment, the end effector TOP is again intended to travel the web x (s), this time, however, also being given its orientation around the dashed web in order, for example, to guide a grinding wheel (not shown) along a surface. The position x ∈ R ^{6 of} the end effector TOP is therefore described, for example, by the position of the end effector in space and its orientation, defined by three Euler angles.

Because the robot 1 However, it has seven joints, it is redundant, ie the predetermined position x of the end effector can be represented by an infinite number of different manipulator positions that apart by rotation of the rest of the robot 1 around the last axis of movement of a held end effector 6 emerge at inertial solid base and together form the null space. As a target position in zero space is in the path planning, the energy-optimal position in which the robot 1 the least static and dynamic forces must be applied.

The robot 1 has an admittance control which makes it possible to manually move the elbow formed by the fourth joint with the joint angle q3, the end effector TCP maintaining its predetermined position x.

The operator now moves the elbow in the direction of the predetermined path, ie to the right in 2 Thus, as described above, the control device increases the speed dx / dt at which the end effector departs from the predetermined path x (s) according to the storage, ie, the amount of the difference vector qact-qsoll. When the operator releases the elbow, the admittance control returns him to the set position, which reduces the web speed back to its original value. On the other hand, the operator moves his elbow against the predetermined path (to the left in 2 ), ie, "holds" the web-departing robot at the elbow, the controller reduces the velocity dx / dt at which the end-effector approaches the predetermined path x (as described above) according to the bin, ie the magnitude of the difference vector qact-qsoll. s) leaves. If the operator moves the elbow correspondingly far in the opposite direction to the given path, the robot stops 1 completely, ie it reduces its speed to zero, or even traverses the already traversed path x (s) even backwards.

By the present invention thus enables the speed, with the one regarding a predefined course of redundant robots this leaves, simply and to change it directly and thus comfortably.

3 shows in a highly schematic perspective view of a lightweight robot LBR of the German Aerospace Center on the departure of a predetermined path x (s) the Tool Center Point of his gripper. The illustrated gripper position can realize the LBR by several manipulator positions, which are uniquely determined by its joint angle, and of which in 3 a first, defined by the joint angle q manipulator position dashed lines, a second, through the joint angle q 'defined manipulator position pulled through and a third, by the joint angle q''defined manipulator position are shown dotted.

As a shelf in this embodiment, the angle a between the vertical and the perpendicular from the elbow of the LBRs on the connecting line between shoulder and carpal joint is selected, which in the first manipulator position in 3 0 °, in the second manipulator position is 30 ° and in the third manipulator position 180 °.

The operator can now grip the LBR in a compliance control at the elbow and place it along an in 3 dashed curve in its zero space move without the Endeffektorlage changes.

In a control device 2 of the LBR, the joint angles q 'which occur in the manipulator position into which the operator moves the LBR are now detected during the travel of the predetermined path x (s) in a step S10. The control device calculates from this 2 based on the known kinematics of the LBRs the angle a and opens the gripper to a clear width A, which is obtained by the angle a multiplied by an operator set in advance constant k. If the operator moves the LBR at the elbow along the dashed curve in its zero space with the end effector position remaining the same from the first to the second manipulator position, the initially closed gripper opens. If the operator moves the LBR at the elbow along the dashed curve with the end effector position remaining the same, from the second to the third manipulator position, the gripper opens even further. As an alternative to the gripper opening, the speed along the path x (s) can of course also be changed as a process variable, as in the preceding embodiments.

1

robot

2

control device

LBR

lightweight robot

q1, q2, ... q7

joint angle

TCP

tool Center Point

x (s)

set path

Claims (15)

Method for traversing a predetermined path (x (s)) through an end effector (TCP) of a manipulator, in particular a robot ( 1 ; LBR), wherein the manipulator with respect to the predetermined path a zero space with at least two of the same Endeffektorlage associated manipulator positions (q, q ', q''), comprising the steps: - Detecting a filing (q-q'; a) of the manipulator in the null space (S10, S20); - Changing at least one process variable (dx / dt; A) according to the recorded file (S30). Method according to claim 1, characterized in that that in the zero space for each Endeffektorlage a desired manipulator position (qsoll) is specified and as a difference the difference (qist - qsoll) the target to the actual Manipulator position is detected. Method according to claim 2, characterized in that that a scheme for reducing the storage is performed. Method according to one of the preceding claims, characterized characterized in that the process size corresponding to a size and / or Direction of the recorded filing changed becomes. Method according to claim 4, characterized in that that the process size is proportional changed to the recorded storage becomes. Method according to one of the preceding claims, characterized characterized in that the manipulator is position-controlled. Method according to one of the preceding claims 1 to 5, characterized in that the manipulator is force-controlled. Method according to claim 6 or 7, characterized that the manipulator is relentlessly regulated. Method according to one of the preceding claims, characterized characterized in that the tray is based on movements and / or forces in Joint of the manipulator is detected. Method according to claim 9, characterized in that that the filing by forces in joints of the manipulator based on a mathematical replacement model of the manipulator is detected. Method according to one of the preceding claims, characterized characterized in that the web speed by a shelf in the Essentially reducible to zero. Method according to one of the preceding Claims, characterized in that the passage sense of the predetermined path can be changed by a tray. Control device ( 2 ) for a manipulator, in particular a robot ( 1 ; LBR), having an end effector (TCP), for carrying out a method according to one of the preceding claims, having - a detection device for detecting a storage (q-q '; a) of the manipulator in the null space; and changing means for changing a process quantity (dx / dt; A) according to the bin detected by the detecting means. Control device according to claim 13, characterized in that it comprises a guide handle to move the manipulator ( 1 ) to move in null space from a manipulator positions in another manipulator positions, which is assigned to the same Endeffektorlage. Manipulator ( 1 ), in particular robots, with a control device according to claim 13 or 14, characterized in that the manipulator has at least seven degrees of freedom.