ROAD PAVERS AND METHOD FOR REGULATING OPERATIONS

Description

[0001] The invention relates to road pavers with automatic leveling and to methods for controlling the operation of such road pavers.

[0002] Road pavers are known that include a screed for compacting paving materials, such as asphalt, and a tractor for towing this screed. The screed is typically mounted on the tractor so that it can pivot around a towing point. The height of the towing point can be adjusted, for example, by a hydraulic cylinder. A so-called tarring machine is known from DE 10 2011 001 542 A1. A smoothing bar is disclosed that is attached to the machine at a towing point. The stroke of this towing point can be adjusted by a towing point cylinder. The amount of adjustment that can be made over a distance of 5 m traveled by the machine is to be limited to 3 mm. Furthermore, a calculated stroke / lower value is to be set by the cylinder only if it is greater than 1 mm.The disclosed control system is based on the assumption that the drag point cylinder must never be adjusted by more than 3mm over a distance of 5 m.

[0003] DE 100 25 474 A1 shows a road paver with a similar control system.

[0004] However, in some installation situations, such rigid limits can be impractical. Therefore, it is an object of the invention to provide an improved road paver and an improved method for controlling its operation, which enables more flexible operation.

[0005] This problem is solved by a road paver having the features of claim 1 and by a method having the features of claim 8.

[0006] A road paver is disclosed, comprising a tractor and a material hopper located at the front of the tractor in one direction of travel and configured to hold paving material. The road paver further comprises a screed mounted on the tractor by means of drawbars pivoting about a drawbar point, allowing the screed to be towed behind the tractor in the direction of travel, and a control system comprising a height sensing device configured to generate a height signal and an actuating cylinder connected to the tractor and to one of the drawbars, configured to adjust the height of the drawbar point relative to the tractor.The control system is configured to compare the altitude signal with a setpoint and thereby calculate a control error, to limit a stroke, in particular an actually set stroke, of the actuator cylinder to a maximum value based on the control error, where the maximum value is proportional to the control error, and to adjust the actuator cylinder based on the control error and taking into account the maximum value.

[0007] Advantageously, the height detection device can be configured to detect vertical movements of the installation screed relative to a height reference and, in particular, to generate the height signal based on this.

[0008] Examples of height references include a wire, a curb, the edge of an existing asphalt layer, or a laser beam. The height detection device can be configured accordingly to detect the respective height reference and may include a height sensor, such as a probe arm, an ultrasonic sensor, a camera, or a laser sensor. A height detection device with a laser sensor can be configured to detect a laser beam as a height reference and / or to detect an edge by emitting and receiving a line laser. In the latter case, the height detection device may also contain its own laser source.

[0009] Alternatively or additionally, the height sensing device can include one or more tilt sensors. The tilt sensor can be configured to detect the tilt, in particular the cross tilt, of the screed. Several tilt sensors can be configured, for example, to detect the tilt of screed sections. When generating the height signal based on an output from a tilt sensor, a length, in particular a length defined perpendicular to the direction of travel, of the screed or a section of the screed whose tilt is detected by the tilt sensor can be taken into account. This can serve to convert an angular signal into a height signal, preferably a vertical one. Particularly in embodiments where the height sensing device is not configured to detect vertical movements of the screed relative to a height reference, the height of the screed can be manually adjusted on one side.The height on the side of the installation screed opposite the direction of travel can then be controlled by a height detection device with tilt sensors, as explained in more detail above.

[0010] Alternatively or additionally, the height sensing device can include a processing unit. The processing unit can be configured to generate the height signal based on an output from one or more of the aforementioned sensors, in particular a height sensor, a probe arm, an ultrasonic sensor, a camera, a laser sensor, and an inclinometer. A height signal can be generated, in particular, based on an output from a height sensor and one or more inclinometers, for example, by adding the height signals generated by the individual sensors as described above.

[0011] Limiting the travel range to a maximum value proportional to the control deviation allows for automatic adjustment of the maximum value to the specific installation situation. Simultaneously, undesirable effects of inertia in the control loop, such as overshoot or excessive oscillations, can be avoided. It can happen that a change in the pull point only affects the height measured by the height sensing device after a delay. Without limiting the travel range, this could undesirably increase or decrease due to a prolonged control deviation. Additionally, for small control deviations, which may only be caused by temporary and / or short-term disturbances such as vibrations, the travel range can also be limited to minimize the impact on the installation result.The control system can contain suitable electronic components and / or assemblies, particularly for calculating, comparing, and generating signals. Individual assemblies or components can each perform one or more of the aforementioned functions. It is conceivable that a central control unit for the road paver could perform these functions.

[0012] It is conceivable that the maximum value is defined relative to a reference value. For example, a specific extension position of the actuator cylinder could serve as the reference value. For instance, the reference value could be set to an extension position that is 160 mm longer than the fully retracted position of the actuator cylinder. If the travel is now limited to a maximum value of 5 mm relative to the reference value, the adjustment of the actuator cylinder can be limited to extension positions within a range of 155 mm to 165 mm.

[0013] It can be advantageous if the reference value is adjustable by the operator. This can be particularly useful at the start of an installation run, for example, to specify an initial reference value. It is especially beneficial if the control system is configured to adjust the reference value automatically. For example, the reference value can be automatically adjusted when the control system detects that it has reached a steady state. A steady state can be defined as one in which the height signal matches the setpoint and / or the control deviation is zero, close to zero, or less than 2 mm. This allows the reference value to track a changing extension position.

[0014] It is conceivable that the maximum value is defined by multiplying the control deviation by a proportionality factor, e.g., 2. The proportionality factor can be adjustable, e.g., by an operator of the paver.

[0015] It is conceivable that an upper limit for the maximum value is defined. This allows, for example, the extension range of the actuator cylinder to be taken into account, i.e., preventing the actuator cylinder from extending to its end stops. The upper limit can be defined depending on the reference value, in particular the currently set reference value. For example, with a maximum possible extension position of the actuator cylinder of 200 mm and a currently set reference value of 150 mm, the upper limit for the maximum value could be set at 45 mm to prevent the actuator cylinder from reaching its end position.

[0016] Furthermore, a method for controlling the operation of a road paver is disclosed. The road paver comprises a tractor, a material hopper arranged at the front of the tractor in one direction of travel and configured to receive paving material, a screed mounted on the tractor by means of drawbars pivoting about a drawbar point, thereby allowing the screed to be towed behind the tractor in the direction of travel, and a control system with a height sensing device and an actuating cylinder connected to the tractor and one of the drawbars.The procedure includes generating a height signal by the height sensing device, calculating a control deviation by comparing the height signal with a setpoint, limiting a stroke of the actuator cylinder to a maximum value proportional to the control deviation, calculating a control signal based on the control deviation taking into account the maximum value for the stroke, and setting a height of the pull point based on the control signal by the actuator cylinder.

[0017] It can be advantageous if the method further comprises detecting the movement of the screed relative to a height reference by the height detection device, wherein the height signal can preferably be generated based on the detected movement of the screed relative to the height reference. All explanations given above with reference to the disclosed road paver may also be applicable to the disclosed method.

[0018] As mentioned above in relation to the road paver, limiting the stroke to a maximum value proportional to the control deviation allows for automatic adjustment of the maximum value to the specific paving situation. At the same time, undesirable effects of inertia in the controlled system, such as overshoot or excessive vibrations, can be avoided. Additionally, in the case of small control deviations, which may only be caused by temporary and / or short-term disturbances such as vibrations, the stroke can also be limited to minimize the impact on the paving result. The control system can include suitable electronic components and / or assemblies, particularly for calculating, comparing, and generating signals. Individual assemblies or components can each perform one or more of these functions.It is conceivable that a central control system for the road paver performs these functions.

[0019] It is conceivable that the maximum value is defined relative to a reference value. As explained above, for example, a specific extension position of the actuator cylinder could be considered the reference value.

[0020] It can be advantageous if the reference value is adjustable by an operator. As explained above, this can be particularly useful at the beginning of an installation run, for example, to specify an initial reference value. It is especially beneficial if the procedure includes automatic adjustment of the reference value by the control system. For example, the reference value can be automatically adjusted when the control system detects that it has reached a steady state. This allows the reference value to be tracked to reflect a changing extension position.

[0021] It is conceivable that the maximum value is defined by multiplying the control deviation by a proportionality factor, e.g., 2. The proportionality factor can be adjustable, e.g., by an operator of the paver.

[0022] It is conceivable that an upper limit for the maximum value is defined. As explained above, this can, for example, take into account the extension range of the actuator cylinder, i.e., preventing the actuator cylinder from extending to its end stops. The upper limit can be defined depending on the reference value, in particular the currently set reference value.

[0023] The invention relates to a road paver and to a method of the type described above. An advantageous embodiment is explained below by way of example with reference to drawings.

[0024] Figure 1shows a schematic side view of a road paver.

[0025] Figure 2 shows a schematic, perspective view of a road paver during a paving run guided by a height reference.

[0026] Figure 3 shows a schematic view of components of a control system for a road paver.

[0027] In Figure 1 Figure 1 shows a schematic side view of a road paver 1. The road paver includes a tractor unit 2. Furthermore, the road paver includes a material hopper 3. The material hopper 3 is located at the front of the tractor unit 2 in a direction of travel R. The material hopper 3 is also configured to hold paving material 4 (see Figure 1). Figure 2The road paver 1 further comprises a screed 5. The screed 5 is mounted to the tractor 2 by means of towing arms 6. As shown in the exemplary embodiment, the screed 5 is pivotably mounted to the tractor 2 about a towing point 7. The tractor 2 is configured to tow the screed 5, preferably floating on an asphalt layer to be compacted. The road paver can further comprise an actuating cylinder 8. The actuating cylinder 8 can be connected to the tractor 2 on one side. It can also be connected to the towing arm 6, in particular at the towing point 7. The actuating cylinder 8 can be configured to adjust the height of the towing point 7 relative to the tractor 2.

[0028] In Figure 2 The road paver 1 is shown in a schematic, perspective view from the front and above. Figure 2Figure 1 also schematically shows a subgrade on which an asphalt layer is to be laid, as well as a height reference 9. As in the present embodiment, the height reference 9 can be a wire reference. The paver 1 can include a height sensing device 10. As in the present embodiment, the height sensing device 10 can be an ultrasonic sensor that can be configured to detect the wire reference 9. The height sensing device 10 can be rigidly connected to the screed 5 and / or to the traction arm 6. This allows the height sensing device 10 to be configured to detect essentially vertical movements of the screed 5 relative to the height reference 9. To adjust the height of the traction point 7 by means of the actuating cylinder 8, the paver includes a control system 11, which is described below with reference to Figure 3 will be explained in more detail.

[0029] In Figure 3Figure 11 is a schematic diagram illustrating the operation of the control system. The control system 11 comprises the height sensing device 10. The control system 11 also comprises the actuating cylinder 8. The height sensing device 10 is configured to generate a height signal 12 based on the detection of the height reference 9. The height signal 12 can, in particular, represent the height of the screed 5 above the subgrade. The control system 11 is configured to compare the height signal 12 with a setpoint 13. The control system 11 is further configured to calculate a control deviation 14 based on the comparison of the setpoint 13 with the height signal 12.

[0030] The control system 11 can further comprise a computing unit 15. The computing unit 15 can be configured to calculate a raw control signal 16 based on the control deviation 14. In parallel, the control system 11 can be configured to calculate a maximum value 17 based on the control deviation 14. The control system 11 can further comprise a limiter 18. The limiter 18 can be configured to adjust a control signal 19 sent to the actuator 8 such that the actual set travel 20 of the actuator 8 is appropriately limited, in particular to the calculated maximum value 17. The limiter 18 can be configured to generate the control signal 19 based on the raw control signal 18 and the maximum value 17.

[0031] When generating the control signal 19, a reference value 21 can also be taken into account. If the reference value 21 is not taken into account when generating the control signal 19, the control signal 19 can represent a set travel distance of the actuator cylinder 8. Based on the control signal 19, the actuator cylinder 8 can then be moved by the set travel distance. If the reference value 21 is taken into account, the control signal 19 can represent a set extension position of the actuator cylinder. In the latter case, the actuator cylinder 8 can then be moved to this position.

[0032] The actuator must be configured to automatically adjust the extension position to be set based on the control signal 19 transmitted to it. In both procedures, the actual set travel 20 of the actuator 8 can be limited to the calculated maximum value 17. A difference lies in the method of controlling the actuator 8.

[0033] The maximum value 17 is proportional to the control deviation 14 and can preferably be calculated by multiplying it by a proportionality factor 22. The proportionality factor 22 can be adjustable, in particular by an operator of the paver 1. Specifically, the maximum value 17 can, for example, correspond to twice the control deviation 14. The reference value 21 can be adjustable by an operator. Alternatively or additionally, the control system 11 can be configured to adjust the reference value automatically. For example, it is conceivable that the reference value 21 is set by an operator at the beginning of a paving operation and is continuously adjusted automatically by the control system 11 during the paving operation.

[0034] Apart from the actuator cylinder 8, all in Figure 3The units shown can be understood as 15 logical units. These can be implemented as electronic circuits, in software, or a mixture of both. In particular, the height sensing device 10 can be implemented as a combination of electronic circuits and software.

Claims

1. Road finisher (1), comprising: a tractor (2), a material hopper (3) arranged at a front of the tractor (2) in a direction of driving (R) and configured to receive paving material (4), a screed (5) pivotably mounted on the tractor (2) about a towing point (7) by means of towing arms (6), whereby the screed (5) is towable behind the tractor (2) in the direction of driving (R), a control system (11) comprising a height detection device (10) configured to generate a height signal (12), and an adjustment cylinder (8) connected to the tractor (2) and to one of the towing arms (6) and configured to adjust a height of the towing point (7) relative to the tractor (2), wherein the control system (11) is configured to compare the height signal (12) with a target value (13) and thereby calculate a control difference (14), characterized in that the control system (11) is configured to limit an adjustment displacement (20) of the adjustment cylinder (8) to a maximum value (17) based on the control difference (14), wherein the maximum value (17) is proportional to the control difference (14), and to adjust the adjustment cylinder (8) based on the control difference (14) and taking into account the maximum value (17).

2. Road finisher according to claim 1, wherein the height detection device is configured to detect vertical movements of the screed (5) relative to a height reference (9) and to generate the height signal (12) based thereon.

3. Road finisher according to claim 1 or 2, wherein the maximum value (17) is defined relative to a reference value (21).

4. Road finisher according to claim 3, wherein the reference value (21) is adjustable by an operator.

5. Road finisher according to claim 3 or 4, wherein the control system (11) is configured to automatically adjust the reference value (11).

6. Road finisher according to one of the preceding claims, wherein the maximum value (17) is defined by multiplication of the control difference (14) with a proportionality factor (22), which is preferably adjustable.

7. Road finisher according to one of the preceding claims, wherein an upper limit for the maximum value (17) is defined.

8. Method for controlling the operation of a road finisher (1) comprising a tractor (2), a material hopper (3) arranged at a front of the tractor (2) in a direction of driving (R) and configured to receive paving material (4), a screed (5) pivotably mounted on the tractor (2) about a towing point (7) by means of towing arms (6), whereby the screed (5) is towable behind the tractor (2) in the direction of driving (R), and a control system (11) comprising a height detection device (10) and an adjustment cylinder (8) connected to the tractor (2) and one of the towing arms (6), the method comprising: generating a height signal (12) by the height detection device (10), and calculating a control difference (14) by comparing the height signal (12) with a target value (13), characterized by limiting an adjustment displacement (20) of the adjustment cylinder (8) to a maximum value (17) that is proportional to the control difference (14), calculating an adjustment signal (19) based on the control difference (14) taking into account the maximum value (17) for the adjustment displacement (20), and adjusting a height of the towing point (7) based on the adjustment signal (19) by the adjustment cylinder (8).

9. Method according to claim 8, further comprising detecting a movement of the screed (5) relative to a height reference (9) by the height detection device (10), wherein the height signal (12) is preferably generated based on the detected movement of the screed (5) relative to the height reference (9).

10. Method according to claim 8 or 9, wherein the maximum value (17) is defined relative to a reference value (21).

11. Method according to claim 10, wherein the reference value (21) is adjustable by an operator.

12. Method according to claim 10 or 11, further comprising automatically adjusting the reference value (21) by the control system (11).

13. Method according to any one of the claims 8 to 12, wherein the maximum value (17) is defined by multiplication of the control difference (14) with a proportionality factor (22), which is preferably adjustable.

14. Method according to any one of the claims 8 to 13, wherein an upper limit for the maximum value is defined (17).