Road paver

Abstract

The utility model relates to a road paver (1). Comprising a tractor (2), at least one traction arm (4), a screed assembly (3) attached to a traction point (5) of the tractor (2) via the at least one traction arm (4), a leveling cylinder (8) adapted to adjust the position, in particular height, of the traction point (5), a screed lift cylinder (10) adapted to adjust the contact pressure of the screed assembly (3), a first measuring device (59) adapted to determine the screed height (55) of the screed assembly (3), second measuring means (61) adapted to determine the angle of attack (14) of the screed assembly (3); and feedback control means (50) adapted to control the leveling cylinder (8) and the screed lift cylinder (10).

Description

Technical Field

[0001] The utility model relates to the technical field of road pavers. In particular, the utility model relates to a road paver having a screed for compacting paving material. Background Art

[0002] A method for determining the change in the attack angle of a screed is known from DE 10 2021 107 447 A1. DE 19647 150 A1 shows a method for controlling the screeding height of a screed. A method for controlling the paving thickness and quality of asphalt paving material is known from EP 2 366 831 B1.

[0003] In the leveling feedback control known in the prior art, the screeding height of the screed is detected and adjusted by means of leveling cylinders. During the paving process, the lifting cylinders of the screed are usually in a floating position. In order to influence the static compaction, a constant pressure can be set on the rod side of the lifting cylinders of the screed. The bottom surface of the screed is inclined towards the roadbed. This inclination is called the attack angle and is adjusted to a predetermined value at the beginning by means of the lifting cylinders of the screed, etc. The attack angle affects the quality of the paving result, especially the degree of compaction of the paving material and the resulting surface appearance. Therefore, it is advantageous to maintain a constant attack angle during operation.

[0004] Changes in the screeding height, changes in the installation speed of the road paver, and / or changes in the paving material may all affect the change in the attack angle of the screed. An overly large or small attack angle may result in poor paving effects. Especially for road pavers with an extended screed, a poor attack angle may cause different screeding heights between the bottom screed and the extension, resulting in an uneven road surface in the transverse direction.

[0005] In the systems known in the prior art, the screeding height is continuously adjusted only by adjusting the leveling cylinders. However, this means that the attack angle is not constant but is determined by the current position of the leveling cylinders as well as the paving material characteristics and other environmental conditions. The attack angle is geometrically defined by the position of the leveling cylinders and the layer thickness. Summary of the Utility Model

[0006] The object of the utility model is to keep the attack angle of the screed as constant as possible during operation, thereby improving the paving quality.

[0007] The paving effect can be significantly improved by the utility model. By continuously checking and adjusting the attack angle of the screed assembly, the longitudinal flatness of the paving material can be improved. When using an extended screed, the transverse flatness of the paving material can also be improved by the utility model. In addition, the compaction effect can be improved by a constant attack angle. Since there is no need for manual monitoring or manual readjustment of the attack angle, the utility model can also improve the process reliability. The system can automatically respond to changes in the paving material, thereby reducing paving errors.

[0008] A first aspect of the present utility model relates to a road paver, which has a tractor, at least one towing arm, a screed assembly, a leveling cylinder, a screed lifting cylinder, a first measuring device, a second measuring device, and a feedback control device. The screed assembly is attached to a towing point of the tractor via at least one towing arm. The leveling cylinder is used to adjust the position of the towing point, especially the height. The screed lifting cylinder is used to adjust the contact pressure of the screed assembly. The contact pressure refers to the pressure exerted by the screed assembly (especially due to its own weight) on the paving material. The contact pressure of the screed assembly may come from the self-weight of the screed assembly and the force of the screed lifting cylinder. The force from the screed lifting cylinder may produce a loading or unloading effect. The first measuring device is adapted to determine the screeding height of the screed assembly. The second measuring device is adapted to determine the attack angle of the screed assembly. The feedback control device is adapted to control the leveling cylinder and the screed lifting cylinder.

[0009] The screed assembly can be configured to form a road paver together with the tractor. The screed assembly can be attached to the tractor. The screed assembly can be configured to be towed behind the tractor in the paving direction. The screed assembly can be configured to compact the paving material on the roadbed, especially asphalt paving material. The screed assembly can be configured to level the paving material on the roadbed, especially asphalt paving material.

[0010] The transverse direction is defined as the direction extending on a horizontal plane and perpendicular to the paving direction. The paving direction is the direction along which the paver moves during the paving process. The lateral direction or the width direction can be a direction parallel to the transverse direction.

[0011] The screed assembly may include a bottom screed and at least one extension, preferably including two extensions. In the context of the present utility model, the bottom screed is also referred to as the main screed. In the context of the present utility model, the extension is also referred to as the secondary screed. The extensions can be laterally arranged on the left and right sides of the bottom screed in the transverse direction. The extensions can be arranged behind the bottom screed in the paving direction. Alternatively, the extensions can also be arranged in front of the bottom screed in the paving direction.

[0012] The bottom screed may include a planing sheet of the bottom screed for contacting the paving material. The extension may include a planing sheet support and an extension planing sheet. The extension planing sheet may be configured to contact the paving material. The extension planing sheet may be attached to the planing sheet support so as to be tiltable about a tilt axis. The screed assembly may include a height adjustment device. The screed assembly may include a tilting device. The height adjustment device may be adapted to lower or raise one or more extensions relative to the bottom screed. The height adjustment device may be configured to lower or raise the planing sheet support relative to the bottom screed. The tilting device may be configured to change the tilt angle of the extension planing sheet about the tilt axis. The tilt axis may extend in the transverse direction. The tilt axis may extend horizontally.

[0013] The screeding height of the screed assembly may represent the vertical distance between the rear edge of the screed assembly (in particular the rear edge of the planing sheet of the screed assembly) and a reference point (such as a reference point on the roadbed). The screeding height of the bottom screed may represent the vertical distance between the rear edge of the bottom screed (in particular the rear edge of the planing sheet of the bottom screed) and a reference point (such as a reference point on the roadbed). The screeding height of the extension may represent the vertical distance between the rear edge of the extension (in particular the rear edge of the planing sheet of the extension) and a reference point (such as a reference point on the roadbed). The term "rear edge" refers to the rearmost edge of the bottom screed or the extension in the paving direction. The height of the rear edge or the screeding height determines the installation height of the paving material.

[0014] The attack angle of the screed assembly may represent the inclination of the screed assembly (in particular the planing sheet of the screed assembly) relative to the roadbed. For a horizontal roadbed, the attack angle of the screed assembly corresponds to the absolute inclination of the planing sheet. The term "absolute inclination" means that the inclination is determined relative to the horizontal plane. For an inclined roadbed, the attack angle is equivalent to the difference between the absolute inclination of the planing sheet and the absolute inclination of the roadbed.

[0015] The attack angle of the bottom screed may represent the inclination of the bottom screed (in particular the planing sheet of the bottom screed) relative to the roadbed. The attack angle of the extension may represent the inclination of the extension (in particular the planing sheet of the extension) relative to the roadbed.

[0016] The screed assembly can be rotatably attached to a towing point of a road paver, in particular to a towing point of a towing vehicle of the road paver, via at least one towing arm. The screed assembly can be rotatably attached to a towing point of a road paver, in particular to a towing point of a towing vehicle, via two towing arms. The towing arms can be arranged at the sides of the towing vehicle. One towing arm can be arranged on each side of the towing vehicle. The height of the towing point can be adjusted with leveling cylinders. The paver can have two towing arms and two leveling cylinders. Each leveling cylinder can be assigned to a towing arm. The leveling cylinder can be connected to the corresponding towing arm. The connection between the leveling cylinder and the towing arm can be made directly or via an intermediate member. The leveling cylinder and the towing arm can be arranged laterally on the road paver relative to the transverse direction of the road paver. There can be a towing arm and a leveling cylinder on each side of the road paver. The features related to the leveling cylinder described in the further course of this application also relate to these two leveling cylinders, even if not explicitly mentioned.

[0017] The screed assembly (in particular the bottom screed) can be connected to the towing vehicle via screed lifting cylinders. The screed assembly (in particular the bottom screed) can be connected to the towing vehicle via two screed lifting cylinders. One screed lifting cylinder or a plurality of screed lifting cylinders can be used to vertically raise or lower the screed assembly. One screed lifting cylinder or a plurality of screed lifting cylinders can be used to adjust the contact pressure of the screed assembly on the paving material. The features related to the screed lifting cylinders described below also apply to two screed lifting cylinders, even if not explicitly mentioned.

[0018] The screed lifting cylinder can be directly connected to the screed assembly or the bottom screed. The screed lifting cylinder can be indirectly connected to the screed assembly or the bottom screed. The screed lifting cylinder can be attached to the towing arm, in particular to the rear region of the towing arm.

[0019] The road paver can have a material hopper. The material hopper can be adapted to receive paving material. The material hopper can be arranged in front of the screed assembly in the paving direction.

[0020] The road paver can have a control device. The control device can be adapted to control the screed lifting cylinders. The control device can be adapted to control the leveling cylinders. The control device can be adapted to control the screed lifting cylinders and the leveling cylinders. The control device can be part of a feedback control device.

[0021] The feedback control device may have a first controller. The first controller may be adapted to control one leveling cylinder or a plurality of leveling cylinders based on a control deviation of the screed height. The control deviation of the screed height is the difference between the target value of the screed height (e.g., the desired installation height) and the actual value of the screed height. The control deviation of the screed height can be determined based on the target value of the screed height and the actual screed height determined by the first measuring device. The target value of the screed height can be specified by manual input of the user. The target value of the screed height can be specified or suggested by the control system (especially according to the paving material). The target value of the screed height can be determined based on the values stored in the previous construction measurements. The target value of the screed height can be derived from the road construction plan. The target value of the screed height can be manually input. The target value can be directly taken from the digital planning data.

[0022] The feedback control device may have a second controller. The second controller may be adapted to control one screed lift cylinder or a plurality of screed lift cylinders based on a control deviation of the attack angle. The control deviation of the attack angle is the difference between the target value of the attack angle (e.g., the desired attack angle) and the actual value of the attack angle. The control deviation of the attack angle can be determined based on the desired value of the attack angle and the actual attack angle determined by the second measuring device. The second controller may be adapted to calculate the required pressure in the screed lift cylinder based on the determined actual attack angle. The target value of the attack angle can be specified by manual input of the user. The target value of the attack angle can be specified or suggested by the control system (especially according to the paving material). The target value of the attack angle can be determined based on the values stored in the previous construction measurements. The target value of the attack angle can be selected to match the height setting of the extension. This allows for adjustment of good compaction, thus obtaining a good paving pattern.

[0023] The feedback control device may have a first controller. The first controller may be adapted to control the leveling cylinder based on a control deviation of the screed height. The feedback control device may have a second controller. The second controller may be adapted to also control the screed lift cylinder based on a control deviation of the screed height.

[0024] The first controller may be a SISO controller (single input single output controller), such as a P controller (proportional controller), a PI controller (proportional integral controller), or a PID controller (proportional integral derivative controller). The first controller may be a robust controller, such as an H-infinity (H∞) controller. The second controller may be a SISO controller, such as a P controller, a PI controller, or a PID controller. The second controller may be a robust controller, such as an H-infinity (H∞) controller.

[0025] The feedback control device may have a multivariable controller. The multivariable controller may be adapted to control the leveling cylinder and the screed lifting cylinder based on the control deviation of the screed height and the control deviation of the angle of attack. Two feedback control variables, namely the angle of attack and the screed height, can both be controlled by one controller (i.e., the multivariable controller). In this way, the interaction between the two control variables (the angle of attack and the screed height) and the two drive variables (the leveling cylinder and the screed lifting cylinder) can be considered. The multivariable controller can also be referred to as a MIMO controller (multi-input multi-output controller). The multivariable controller can be an H-infinity controller, an LQ controller, or an LQG controller.

[0026] In the systems known in the prior art, the current installation speed is usually included in the feedback control. However, with the feedback control device according to the present invention, this is not necessary. The feedback control device (especially the multivariable controller) can be adapted to not output any other control variables except for the angle of attack and the screed height. The feedback control device (especially the multivariable controller) may be adapted to control the screed lifting cylinder and the leveling cylinder only based on the angle of attack and the screed height (especially based on the target / actual comparison of the angle of attack and the target / actual comparison of the screed height). The feedback control device (especially the multivariable controller) may be adapted to control the screed lifting cylinder and the leveling cylinder only based on the measured values from the first measuring device and the second measuring device. The feedback control device, especially the multivariable controller, can be applicable to controlling the screed lifting cylinder and the leveling cylinder without considering the installation speed. The feedback control device may be adapted to select control parameters according to the installation speed. The feedback control device may be adapted to control the screed lifting cylinder and the leveling cylinder according to the installation speed. The feedback control device may be adapted to apply a large controller magnification at a high installation speed and a small controller magnification at a low installation speed. The terms high, low, large, and small should be understood in relation to each other.

[0027] The first measuring device may be a rangefinder, such as a laser rangefinder, a mechanical probe, or an acoustic rangefinder.

[0028] The second measuring device may have a first tilt sensor. The second measuring device may have a second tilt sensor. The second measuring device may have a first tilt sensor and a second tilt sensor. The first tilt sensor may be arranged on the screed assembly. The second tilt sensor may be arranged on the towing vehicle.

[0029] The first tilt sensor may be adapted to determine the tilt angle of the screed assembly relative to the horizontal plane. The second tilt sensor may be adapted to determine the tilt angle of the towing vehicle relative to the horizontal plane. The second measuring device may be adapted to determine the angle of attack of the screed assembly based on the tilt angle of the screed assembly and the tilt angle of the towing vehicle.

[0030] The first tilt sensor may be adapted to determine the tilt angle of the bottom screed relative to the horizontal plane. The first tilt sensor may be adapted to determine the tilt angle of the extension relative to the horizontal plane. The tilt angle of the tractor may correspond to the gradient of the roadbed. Alternatively, the gradient of the roadbed or the tilt angle of the tractor may be determined based on a digital terrain model. In this case, a second tilt sensor on the tractor is not necessary. The tilt angle may be calculated based on the tilt angle measured by the first tilt sensor and the gradient of the roadbed determined according to the terrain model. A plurality of first tilt sensors may be attached to determine and control the tilt angle of the screed assembly at a plurality of points (e.g., at two extensions). A plurality of second tilt sensors may be attached such that the tilt angle of the tractor may be determined based on the average value of the second tilt sensors.

[0031] The second measuring device may have a tilt sensor attached to the bottom screed or the extension. The tilt sensor may be configured to determine the tilt angle of the bottom screed or the extension relative to the horizontal plane. The control device of the paver may be adapted to determine the roadbed gradient based on a digital terrain model. The control device may be adapted to determine the attack angle of the bottom screed based on the determined tilt angle of the bottom screed and the roadbed gradient. The control device may be adapted to determine the attack angle of the extension based on the determined tilt angle of the extension and the roadbed gradient.

[0032] The second measuring device may have a rotation angle sensor. The rotation angle sensor may be arranged at the towing point of the tractor. The rotation angle sensor may be adapted to measure the inclination of the towing arm relative to the inclination of the tractor. The screed assembly may be rigidly connected to the towing arm. Then, the attack angle of the screed assembly may be determined via the inclination of the towing arm. The rotation angle measured at the towing point may correspond to the attack angle.

[0033] The second measuring device may have a first rotation angle sensor on a first towing arm attached to one side of the tractor, and a second rotation angle sensor on a second towing arm attached to the other side of the tractor. Then, the attack angle of the screed assembly may be determined based on the average value of the first and second rotation angle sensors.

[0034] The feedback control device and / or the control device may be configured to filter out environmental influences. The feedback control device and / or the control device may be configured to filter out the influences from vibrations and / or temperature fluctuations. Advanced signal processing methods, such as a Kalman filter or a state observer, may be used to achieve this purpose.

[0035] The screed assembly may have a bottom screed and at least one extension. The extension may be arranged to deviate at least partially from the bottom screed in the paving direction of the road paver. The extension may be arranged at least partially in front of or behind the bottom screed in the paving direction of the road paver. The extension may be completely arranged in front of or behind the bottom screed in the paving direction of the road paver. The bottom screed and the extension may have the same attack angle. The extension may be laterally arranged adjacent to the bottom screed with respect to the transverse direction. The screed assembly may have two extensions. The extensions may be arranged on both sides of the bottom screed with respect to the transverse direction. The extensions may be laterally telescopic, so that the width of the screed assembly can be changed. The width of the screed assembly corresponds to the extension of the screed assembly in the transverse direction. The extension may have a vertical offset with respect to the bottom screed. The vertical offset can be adjusted by a height adjustment device. Due to the geometric arrangement of the bottom screed and the extension, the vertical offset is optimal only at a specific attack angle. If the attack angle changes, the vertical offset must be adjusted. Otherwise, the bottom screed and the extension will have different screeding heights. This will result in indentations of the extension in the installed layer and unevenness in the transverse direction. The screed assembly may also consist only of the bottom screed without extensions.

[0036] The screed lift cylinder may have a pressure control device on the piston side. The screed lift cylinder can be adjusted so that it allows the screed assembly to be released and loaded. This can correct too small or too large an attack angle. If the attack angle is too small or too large, the feedback control device will adjust the attack angle.

[0037] The expressions "first", "second", "third" and "fourth" should be understood as only defining specific elements or components and do not necessarily imply a specific order of the said components or elements. For example, the presence of the second component does not necessarily mean the presence of the first component, and vice versa. Description of the Drawings

[0038] The present utility model will be described in more detail below in conjunction with embodiments.

[0039] Figure 1 A schematic side view of a road paver with a screed assembly according to an embodiment of the present utility model is shown.

[0040] Figure 2 A schematic top view of a road paver with a screed assembly according to an embodiment of the present utility model is shown.

[0041] Figure 3 A schematic side view of a screed assembly and a traction arm in a first installation position according to an embodiment of the present utility model is shown.

[0042] Figure 4Shows a schematic side view of a screed assembly and a traction arm in a second mounting position according to an embodiment of the present invention.

[0043] Figure 5 Shows a schematic side view of a screed assembly and a traction arm in a third mounting position according to an embodiment of the present invention.

[0044] Figure 6 shows a feedback control circuit known in the prior art for feedback controlling the position of a screed assembly.

[0045] Figure 7 Shows a feedback control circuit for feedback controlling the position of a screed assembly according to an exemplary embodiment of the present invention.

[0046] Figure 8 Shows a feedback control circuit for feedback controlling the position of a screed assembly according to an exemplary embodiment of the present invention.

[0047] Figure 9 Shows a feedback control circuit for feedback controlling the position of a screed assembly according to an exemplary embodiment of the present invention. Detailed Description

[0048] Figure 1 Shows a road paver 1 according to an embodiment of the present invention. The road paver 1 includes a tractor 2 and a screed assembly 3. The screed assembly 3 is connected to the tractor 2 by means of two traction arms 4, each traction arm 4 extending laterally on the road paver 1. The traction arm 4 is pivotally connected to the tractor 2 at a traction point 5. The screed assembly 3 is arranged behind the tractor 2 with respect to the paving direction 100 and is towed behind the tractor 2 by the traction arms 4. A material hopper 6 for receiving paving material is arranged in the front region of the road paver 1. The paving material is transported by a material transport device of the tractor 2 rearward against the paving direction 100 and sent to the screed assembly 3. A transverse distribution device 7 can be provided in the rear region of the tractor 2, which distributes the paving material orthogonally to the paving direction 100 in front of the screed assembly 3.

[0049] A leveling cylinder 8 is arranged on each side of the road paver 1. The leveling cylinder 8 is connected to the corresponding traction arm 4 via an intermediate member 9. The position (especially the height) of the traction point 5 can be adjusted by the leveling cylinder 8. A screed lifting cylinder 10 is arranged in the rear region of the road paver 2. The screed lifting cylinder 10 is attached to the rear region of the corresponding traction arm 4. Alternatively, the screed lifting cylinder 10 can also be directly connected to the screed assembly 3. The screed lifting cylinder 10 can be used to adjust the position (especially the height and contact pressure) of the screed assembly 3.

[0050] Figure 2The top view of a road paver 1 according to an embodiment of the present utility model is shown. The traction arm 4 is arranged on the side of the tractor 2. The screed assembly 3 includes a bottom screed 11 and two extensions 12. The extensions 12 are arranged behind the bottom screed 11 along the paving direction 100. Alternatively, the extensions 12 can be arranged in front of the bottom screed 11 along the paving direction 100. The extensions 12 are arranged laterally adjacent to the bottom screed 11 along the transverse direction 200. The extensions 12 can be retracted and extended along the transverse direction 200, so that the width of the screed assembly 3 changes. The width of the screed assembly 3 is the extension of the screed assembly 3 in the transverse direction 200. By assembling widening parts on the extensions, the width of the screed assembly can be increased.

[0051] Figure 3 The schematic side view of the screed assembly 3 and the traction arm 4 in the first installation case on the flat roadbed 13 is shown. The extensions 12 are arranged behind the bottom screed 11 along the paving direction 100. The extensions 12 have the same attack angle 14 as the bottom screed 11. The dashed line represents the desired installation height 15 of the finished paving material. The bottom screed 11 and the extensions 12 are arranged with an offset in the vertical direction. The vertical offset 16 between the bottom screed 11 and the extensions 12 is adjusted so that the extension height 18 corresponds to the bottom screed height 17. This is usually manually adjusted before installation.

[0052] Figure 4 The screed assembly 3 and the traction arm 4 in the second installation case are shown. Compared with Figure 3 the traction point 5 is higher. This results in a larger attack angle 14. The attack angles 14 of the bottom screed 11 and the extensions 12 are still the same. As can be seen from Figure 4 the bottom screed height 17 corresponds to the desired installation height 15. Since the extensions 12 are arranged behind the bottom screed 11 in the paving direction 100, the rear edge of the extensions 12 sinks deeper than the rear edge of the bottom screed 11. Therefore, the extension height 18 is less than the bottom screed height 17. This results in unevenness of the finished paving material in the transverse direction.

[0053] Figure 5 The screed assembly 3 and the traction arm 4 in the third installation case are shown. The roadbed 13 has a roadbed inclination 19. Figure 5 Only the bottom screed 11 is shown in Figure 5In the position of the screed assembly 3 shown, the bottom screed height 17 corresponds to the desired installation height 15. The bottom screed 11 has an absolute bottom screed inclination 20. The absolute bottom screed inclination 20 is the inclination of the bottom screed 11 relative to the horizontal plane. The angle of attack 14 of the bottom screed 11 is calculated by subtracting the subgrade inclination 19 from the absolute bottom screed inclination 20.

[0054] Figure 6 shows a feedback control circuit known in the prior art, which has a feedback control device 50 for feedback controlling the position of the screed assembly 3. The screed transfer behavior 51 is affected by the screed lift cylinder pressure 52, the subgrade height 53, and the leveling cylinder position 54. The screed lift cylinder pressure 52 and the subgrade height 53 are external input parameters. Another input parameter is the required installation height 15. The screed height 55 and the angle of attack 14 are determined based on the screed lift cylinder pressure 52, the subgrade height 53, and the leveling cylinder position 54. The screed height 55 is measured by a measuring device 56 and transmitted to a controller 57. The controller 57 compares the desired installation height 15 with the measured screed height 55 and, if necessary, changes the leveling cylinder position 54. The controller 57 only reacts to changes in the screed height 55. The controller 57 does not react to changes in the angle of attack 14.

[0055] Figure 7 A control circuit according to an exemplary embodiment of the present invention is shown, which has a feedback control device 50 for feedback controlling the position of the screed assembly 3. As shown in Figure 6, the screed transfer behavior 51 is affected by the screed lift cylinder pressure 52, the subgrade height 53, and the leveling cylinder position 54. Compared with the control circuit shown in Figure 6, only the subgrade height 53 is an external input parameter. The desired installation height 15 and the desired angle of attack 58 are specified as target values. The target value of the installation height 15 and / or the target value of the angle of attack 58 can be specified by manual input by the user. The target value of the installation height 15 and / or the target value of the angle of attack 58 can be specified or suggested by the control system (especially according to the paving material). The target value of the installation height 15 and / or the target value of the angle of attack 58 can be determined based on the values stored in previous construction surveys. The screed height 55 and the angle of attack 14 of the screed assembly 3 are adjusted based on the screed lift cylinder pressure 52, the subgrade height 53, and the leveling cylinder position 54. The screed height 55 of the screed assembly 3 is measured by a first measuring device 59 and transmitted to a first controller 60. The first controller 60 compares the desired installation height 15 with the measured screed height 55 and, if necessary, changes the leveling cylinder position 54. The angle of attack 14 of the screed assembly 3 is measured by a second measuring device 61 and transmitted to a second controller 62. The second controller 62 compares the desired angle of attack 58 with the measured angle of attack 14 and, if necessary, changes the screed lift cylinder pressure 52. The first controller 60 responds to changes in the screed height 55, while the second controller 62 responds to changes in the angle of attack 14.

[0056] Figure 8 shows a control circuit according to another exemplary embodiment of the present invention, which has a feedback control device 50 for feedback control of the position of the screed assembly 3. Compared with Figure 7 the control circuit shown, Figure 8 the control circuit in [reference] only has a first measuring device 59. The first measuring device 59 measures the screeding height 55 of the screed assembly 3 and transmits it to the first controller 60 and the second controller 62. The first controller 60 compares the desired installation height 15 with the measured screeding height 55 and, if necessary, changes the leveling cylinder position 54. The second controller 62 compares the desired installation height 15 with the measured screeding height 55 and, if necessary, changes the screed lifting cylinder pressure 52.

[0057] Figure 9 shows a control circuit according to another exemplary embodiment of the present invention, which has a feedback control device 50 for feedback control of the position of the screed assembly 3. Compared with Figure 7 the control circuit shown, Figure 9 the control circuit in [reference] has a multivariable controller 63. The first measuring device 59 measures the screeding height 55 of the screed assembly 3 and transmits it to the multivariable controller 63. The second measuring device 61 measures the attack angle 14 of the screed assembly 3 and transmits it to the multivariable controller 63. The multivariable controller 63 compares the desired installation height 15 with the measured screeding height 55 and uses this comparison to calculate the control deviation of the screeding height. The multivariable controller 63 compares the desired attack angle 58 with the measured attack angle 14 and uses this comparison to calculate the control deviation of the attack angle. Based on the control deviation of the screeding height and the control deviation of the attack angle, the multivariable controller 63 changes the screed lifting cylinder pressure 52 and the leveling cylinder position 54 if necessary. The multivariable controller 63 can be a MIMO controller (multi-input multi-output controller).

Claims

1. A road paver (1), comprising: A tractor (2), At least one towing arm (4), A screed assembly (3) attached to a towing point (5) of the tractor (2) via at least one towing arm (4), and A leveling cylinder (8) adapted to adjust the position of the towing point (5), A screed lifting cylinder (10) adapted to adjust the contact pressure of the screed assembly (3), A first measuring device (59) adapted to determine the screed height (55) of the screed assembly (3), A second measuring device (61) adapted to determine the attack angle (14) of the screed assembly (3), and A feedback control device (50) adapted to control the leveling cylinder (8) and the screed lifting cylinder (10).

2. The paver according to claim 1, wherein, The leveling cylinder (8) is adapted to adjust the height of the towing point (5).

3. The road paver according to claim 1, wherein, The feedback control device (50) has a first controller (60) and a second controller (62), the first controller (60) being adapted to control the leveling cylinder (8) based on a control deviation of the screed height (55), and the second controller (62) being adapted to control the screed lifting cylinder (10) based on a control deviation of the attack angle (14).

4. The paver for road according to claim 1, wherein, The feedback control device (50) has a first controller (60) and a second controller (62), the first controller (60) being adapted to control the leveling cylinder (8) based on a control deviation of the screed height (55), and the second controller (62) being adapted to control the screed lifting cylinder (10) based on a control deviation of the screed height (55).

5. The paver according to claim 1, wherein, The feedback control device (50) has a multivariable controller (63), the multivariable controller (63) being adapted to control the leveling cylinder (8) and the screed lifting cylinder (10) based on a control deviation of the screed height (55) and a control deviation of the attack angle (14).

6. The road paver according to any one of claims 1 to 5, wherein, The second measuring device (61) has a first tilt sensor disposed on the screed assembly (3) and a second tilt sensor disposed on the tractor (2), wherein the first tilt sensor is adapted to determine the tilt angle of the screed assembly (3) relative to the horizontal plane, wherein the second tilt sensor is adapted to determine the tilt angle of the tractor (2) relative to the horizontal plane, wherein the second measuring device is adapted to determine the attack angle (14) of the screed assembly (3) based on the tilt angle of the screed assembly (3) and the tilt angle of the tractor (2).

7. The paver according to any one of claims 1 to 5, wherein The second measuring device (61) has a rotation angle sensor disposed at the towing point (5) of the tractor (2).

8. The road paver according to any one of claims 1 to 5, wherein, The screed assembly (3) has a bottom screed (11) and at least one extension (12), wherein the extension (12) is arranged to deviate at least partially from the bottom screed (11) in the paving direction (100) of the road paver (1), and wherein the bottom screed (11) and the extension (12) have the same attack angle (14).

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