Position control of a boom tip

Abstract

A large manipulator includes a boom arm with a turntable and a plurality of boom segments, which are configured to be pivoted at respective articulation joints with respect to an adjacent boom segment or the turntable. The boom arm further includes at least one inertial sensor configured to measure inclination and/or acceleration of at least one of the plurality of boom segments.

Claims

1. A large manipulator comprising: a boom arm configured to be folded out and comprising: a turntable configured to be rotated about a vertical axis, a plurality of boom segments configured to be pivoted at respective articulation joints about respective horizontal bending axes with respect to an adjacent boom segment or the turntable by means of a drive assembly, wherein a last of the plurality of boom segments includes a boom tip, and a first inertial sensor arranged at the boom tip and configured to measure acceleration of the last boom segment and generate a responsive sensor signal; and a position control system configured to control a vertical position of the boom tip based, at least in part, on either measured inclinations of the plurality of boom segments or measured angular positions of the respective articulation joints, in combination with a double chronological integration of the measured acceleration, in a vertical direction, sensed by the first inertial sensor.

2. The large manipulator of claim 1, wherein each of the boom segments includes a first end portion, a second end portion, and a center portion extending between the first and the second end portions, wherein a second inertial sensor is positioned substantially in a center of the center portion.

3. The large manipulator of claim 1, further comprising: a computer configured to calculate the vertical position of the boom tip.

4. The large manipulator of claim 1, further comprising: an angle sensor arranged on one of the articulation joints and configured to sense angular position of the articulation joint.

5. The large manipulator of claim 1, further comprising: an angle sensor arranged on each of the articulation joints, wherein each angle sensor is configured to sense angular position of one of the respective articulation joints.

6. The large manipulator of claim 1, wherein the position control system is further configured to damp oscillations of the plurality of boom segments.

7. The large manipulator of claim 6, wherein the position control system includes a proportional-integral-differential controller.

8. The large manipulator of claim 1, wherein the first inertial sensor comprises both a two-axis acceleration sensor and a rotational speed sensor.

9. The large manipulator of claim 8, further comprising: an observer configured to combine measurement signals of the two-axis acceleration sensor with a chronologically integrated measurement signal of the rotational speed sensor.

10. The large manipulator of claim 9, wherein the observer is an extended Kalman filter.

11. The large manipulator of claim 1, further comprising: at least one inertial sensor arranged on each of the plurality of boom segments.

12. A concrete pump comprising: a vehicle chassis; a thick matter pump arranged on the vehicle chassis; and the large manipulator of claim 1.

13. A method for use with a large manipulator including a boom arm with a plurality of boom segments pivotable at respective articulation joints, the last of the plurality of boom segments including a boom tip, and an inertial sensor positioned on the boom tip, the method comprising: measuring, via the inertial sensor, acceleration of the last of the plurality of boom segments; measuring one or more of: inclinations of the plurality of boom segments and angular positions of the respective articulation joints; and calculating, via a computer, a vertical position of the boom tip based, at least in part on, either the measured inclinations of the plurality of boom segments or the measured angular positions of the respective articulation joints, in combination with a double chronological integration of the measured acceleration, in a vertical direction, sensed by the inertial sensor.

14. The method of claim 13, wherein the inertial sensor comprises a two-axis acceleration sensor and a rotational speed sensor, the method further comprising: calculating, via the computer, the vertical position of the boom tip based, at least in part, on acceleration sensed by the two-axis acceleration sensor.

15. The method of claim 13, further comprising: controlling, via a position control system, the vertical position of the boom tip based, at least in part, on the measured inclinations.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 shows a schematic view of a boom arm according to the invention in a first configuration,

(3) FIG. 2 shows a schematic view of a boom arm according to the invention in a second configuration,

(4) FIG. 3 shows a schematic view of a boom arm according to the invention in a third configuration,

(5) FIG. 4 shows a schematic view of a boom arm according to the invention in a fourth configuration, and

(6) FIG. 5 shows a schematic closed-loop control circuit according to an embodiment of the invention.

DETAILED DESCRIPTION

(7) FIG. 1 shows a schematic illustration of a boom arm 10 according to the invention with means 34, 36, 38 for measuring the inclination in a first configuration. The large manipulator has a boom arm 10 which can be folded out and which has a turntable 12 which can be rotated about a vertical axis and a multiplicity of boom segments 14, 16, 18. The boom segments 14, 16, 18 can be pivoted to a limited extent with respect to an adjacent boom segment 14, 16, 18 or the turntable 12, in each case by means of one drive assembly 26, 28, 30. The boom arm 10 preferably has between three and five boom segments 14, 16, 18. The large manipulator according to the invention has at least one inertial sensor 34, 36, 38 for sensing the inclination of the boom segments 14, 16, 18 with respect to the earth. The inertial sensors 34, 36, 38 are each preferably composed of a two-axis acceleration sensor and a rotational speed sensor. The axis of the rotational speed sensor is ideally positioned orthogonal on the acceleration axes of the acceleration sensor. Since the translatory movements only have a very small influence on the rotational speed sensors, the measurements thereof are used to detect and correct falsifications of the angles of inclination which are determined from the acceleration measurements and to correct them. As a result, a measurement error during movements of the boom is reduced.

(8) The boom arm 10 according to the invention as illustrated in FIG. 1 has an inertial sensor 34, 36, 38 on each boom segment 14, 16, 18. The inertial sensors 34, 36, 38 are arranged essentially in the center of the boom segments 14, 16, 18. As a result of such an arrangement of the sensors 34, 36, 38, the difference between the measured inclinations of two successive boom segments 14, 16, 18 includes not only the precise articulation angle but also a portion of the elastic deformation. This can adversely affect the kinematics of the boom arm approximately as a rigid body problem.

(9) FIG. 2 shows a schematic illustration of a boom arm 10 according to the invention with means for measuring the inclination in a second configuration. The boom segments 14, 16, 18 each have an inertial sensor 34, 36, 38 which is arranged essentially in the center thereof. In order to improve the measurement of the height of the boom tip 32 further, in particular in the case of rapid movements with large accelerations, an additional measurement of the accelerations is made directly on the boom tip 32. The double chronological integration of the portion of the acceleration in the vertical direction supplies a measurement signal which has a good degree of correspondence with the dynamic portions of the movement sequence in the upper frequency band. For this purpose, the boom segment 18, whose outer end constitutes the boom tip 32, has an additional sensor 40 at its outer end, of the boom tip 32.

(10) However, for sufficiently precise measurements it is also sufficient if just one sensor is arranged on the boom tip.

(11) FIG. 3 shows a schematic illustration of a boom arm 10 according to the invention with the means for measuring the inclination in a third configuration. The boom segments 14, 16 each have an inertial sensor 34, 36 which are arranged essentially in the center thereof. The boom segment 18 has an inertial sensor 40 at the outer end thereof, of the boom tip 32. Since the influence of the beam curvature of the last boom segment 18 on the height of the boom tip is small in relation to that of the preceding boom segments 14, 16, such an arrangement gives rise to a sufficiently precise measurement result. It is therefore possible to dispense with an additional sensor 38.

(12) FIG. 4 shows a schematic view of a boom arm 10 according to the invention in a fourth embodiment. The boom segments 14, 16, 18 each have an angle sensor 48, 50, 52. The angle sensors 48, 50, 52 sense the angular positions of the individual articulation joints 20, 22, 24. In addition, an inertial sensor 40, which senses the vertical acceleration of the boom tip 32, is arranged on the boom tip 32. By combining the signals of the angle sensors 48, 50, 52 with the signals of the inertial sensor 40 it is possible to implement a very precise determination of the continuous height of the boom tip 32.

(13) With the illustrated sensor concept it is possible to implement an effectively acting control of the height of the jib tip. This is shown schematically in FIG. 5.

(14) It is assumed here that a control of the articulation angles is implemented in order to damp the oscillation of the boom arm 10. The angular speeds of the individual joints 20, 22, 24 are here the manipulated variables U1, U2, U3 of the system.

(15) According to the invention, a position control on the basis of a PID controller 46 and a module 47 for controlling the lifting movement or lowering movement of the boom tip 32 is superimposed on the damping of the oscillation. The instantaneous height H of the boom tip is determined by means of a computer 42 from the measurement signals of the inertial sensors 34, 36, 38, 40 arranged on the boom 10 (see FIG. 2) or from the signals of the angle sensors 48, 50, 52 in combination with the signal of the inertial sensor 40 (see FIG. 4) as described above. The position control determines, by means of the control error (deviation of the actual value of the height of the boom tip 32 from its set point value), a controller output A which is predefined as a set point value in the form of a lifting movement or a lowering movement of the boom tip for the module 47. Said position controller calculates the control signals which are applied to the manipulated variables U1, U2 and U3 of the individual joints 20, 22 and 24.

(16) The set point value for the height of the boom tip 32 is determined during practical operation by the method of the operator and therefore arises from the position of rest for the respective current position of the boom arm 10. A precise calculation of the position of rest of the height of the boom tip 32 by means of the current stationary values of the articulation angles is not possible because of the complexity of the overall system and the only imprecise knowledge of the model parameters for the practical operation, and it is not necessary either.

(17) Therefore, a simple high-pass filter 44 with a suitably selected cutoff frequency is used for the PID controller 46 for determining the control error. Drifting away of the height from the original position as a result of the controller intervention is prevented by the underlying oscillation-damping control, which includes control of the articulation positions. As a result of the illustrated control, vertical movements of the boom tip 32, e.g. of an auto concrete pump, can be effectively reduced during the pumping operation.

LIST OF REFERENCE NUMBERS

(18) 10 Boom arm

(19) 12 Turntable

(20) 14 First boom segment

(21) 16 Second boom segment

(22) 18 Third boom segment

(23) 20 First articulation joint

(24) 22 Second articulation joint

(25) 24 Third articulation joint

(26) 26 First drive element

(27) 28 Second drive element

(28) 30 Third drive element

(29) 32 Boom tip

(30) 34 First inertial sensor

(31) 36 Second inertial sensor

(32) 38 Third inertial sensor

(33) 40 Inertial sensor of boom tip

(34) 42 Computer

(35) 44 High-pass filter

(36) 46 PID controller

(37) 47 Module for controlling the lifting and lowering movement of the boom tip

(38) 48 First angle sensor

(39) 50 Second angle sensor

(40) 52 Third angle sensor