Road paving machine with feedback control of screed height adjustment
The feedback control system for road paving machines maintains a constant screed attack angle, addressing uneven pavement issues by continuously adjusting screed height and angle, thereby improving pavement quality and uniformity.
Patent Information
- Application Number
- JP2024108666
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-07-14
- Filing Date
- 2024-07-05
- Publication Date
- 2025-01-24
AI Technical Summary
Existing road paving technologies struggle to maintain a constant screed attack angle during operation, leading to uneven pavement quality due to changes in screed height, laying speed, and material characteristics, resulting in inferior pavement results.
A road paving machine equipped with a feedback control system that continuously measures and adjusts the screed attack angle and height using sensors and actuators, automatically responding to changes in paving materials and environmental conditions to ensure uniformity and reliability.
The system improves pavement quality by maintaining a constant screed attack angle, enhancing the uniformity of paved materials in both longitudinal and transverse directions, reducing errors, and increasing the reliability of the paving process.
Smart Images
Figure 2025013238000001_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to the technical field of road pavers, in particular to a road paver equipped with a screed for compacting paving material, and to a method for controlling such a road paver. [Background technology]
[0002] From DE 10 2021 107 447 A1 a method is known for determining the change in the attack angle of a screed. DE 19 647 150 A1 shows a method for controlling the screed height of a screed. From EP 2 366 831 B1 a method is known for controlling the pavement thickness and the quality of asphalt paving material.
[0003] In the height adjustment feedback control known from the prior art, the screed height of the screed is detected and adjusted with the aid of a height adjustment cylinder. During paving, the screed lifting cylinder is usually in a floating position. To perform static compaction, a constant pressure can be set on the rod side of the screed lifting cylinder. The underside of the screed is inclined to the subgrade. This inclination is called the attack angle and is adjusted to a predefined value at the start by, inter alia, the screed lifting cylinder. The attack angle influences the quality of the paving result, in particular the compaction of the paving material and the resulting surface appearance. It is therefore advantageous for the attack angle to be constant during operation.
[0004] A change in screed height, a change in the laying speed of the road paver, and / or a change in paving material can result in a change in the screed's angle of attack. An angle of attack that is too high or too low can result in poor paving results. Particularly for road pavers with extension screeds, an undesirable angle of attack can result in different screed heights between the base screed and the extensions, which can result in unevenness across the road.
[0005] In systems known from the prior art, only the screed height is continuously adjusted by adjusting the leveling cylinder. However, this means that the attack angle is not constant but depends on the current position of the leveling cylinder as well as the properties of the paving material and other environmental conditions. The attack angle is geometrically defined by the position of the leveling cylinder and the layer thickness. Summary of the Invention [Problem to be solved by the invention]
[0006] The invention aims to keep the screed's angle of attack as constant as possible during operation, thereby improving paving quality. [Means for solving the problem]
[0007] This object is solved by the use of a road paver according to claim 1, a method for feedback controlling the position of a screed assembly according to claim 8 or a feedback control device according to claim 14.
[0008] The paving results can be significantly improved with the present invention. The longitudinal uniformity of the paved material can be improved by continuously checking and adjusting the angle of attack of the screed assembly. When using an extended screed, the transverse uniformity of the paved material can also be improved with the present invention. In addition, the compaction results can be improved with a constant angle of attack. The reliability of the process can also be increased with the present invention, since manual monitoring or manual adjustment of the angle of attack is not required. The system can automatically react to changes in the paving material, which reduces paving errors.
[0009] A first aspect of the invention relates to a road paver comprising a towing vehicle, at least one towing arm, a screed assembly, a height adjustment cylinder, a screed lift 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 towing vehicle via at least one towing arm. The height adjustment cylinder adjusts the position, in particular the height, of the towing point. The screed lift cylinder adjusts the ground pressure of the screed assembly. The ground pressure refers to the pressure that the screed assembly exerts on the paving material, in particular due to its own weight. The ground pressure of the screed assembly may result from the weight of the screed assembly and from a force coming from the screed lift cylinder. The force coming from the screed lift cylinder may have the effect of applying or removing a load. The first measuring device determines the screed height of the screed assembly. The second measuring device determines the attack angle of the screed assembly. The feedback control device controls the height adjustment cylinder and the screed lift cylinder.
[0010] The screed assembly together with the towing vehicle may constitute a road paver. The screed assembly may be attached to the towing vehicle. The screed assembly may be configured to be towed behind the towing vehicle in a paving direction. The screed assembly may be configured to compact paving material, particularly asphalt paving material, onto a subgrade. The screed assembly may be configured to level paving material, particularly asphalt paving material, onto a subgrade.
[0011] The cross direction is defined as the direction extending in a horizontal plane perpendicular to the paving direction. The paving direction is the direction in which the road paver moves during paving. The transverse or width direction may be the direction parallel to the cross direction.
[0012] The screed assembly may comprise a base screed and at least one extension, preferably two extensions. The base screed is also referred to in the context of the present invention as a main screed. The extension is also referred to in the context of the present invention as a secondary screed. The extension may be arranged laterally to the left and right of the base screed in the cross direction. The extension may be arranged behind the base screed in the paving direction. Alternatively, the extension may be arranged in front of the base screed in the paving direction.
[0013] The base screed may comprise a base screed levelling sheet in contact with the paving material. The extension may comprise a levelling sheet support and an extension levelling sheet. The extension levelling sheet may be configured to contact the paving material. The extension levelling sheet may be tiltably attached to the levelling sheet support about a tilting axis. The screed assembly may comprise a height adjustment device. The screed assembly may comprise a tilting device. The height adjustment device may raise and lower the extension relative to the base screed. The height adjustment device may raise and lower the levelling sheet support relative to the base screed. The tilting device may be configured to change a tilting angle of the extension levelling sheet about the tilting axis. The tilting axis may extend in a transverse direction. The tilting axis may extend in a horizontal direction.
[0014] The screed height of the screed assembly may refer to the vertical distance between the rear edge of the screed assembly, in particular the rear edge of the screed assembly's planarizing sheet, and a reference point, for example, on the subgrade. The screed height of the base screed may refer to the vertical distance between the rear edge of the base screed, in particular the rear edge of the base screed planarizing sheet, and a reference point, for example, on the subgrade. The screed height of the extension may refer to the vertical distance between the rear edge of the extension, in particular the rear edge of the extension planarizing sheet, and a reference point, for example, on the subgrade. The term rear edge refers to the rearmost edge of the base screed or extension in the paving direction. The height of the rear edge or screed height determines the laying height of the paving material.
[0015] The angle of attack of the screed assembly may refer to the inclination of the screed assembly relative to the inclination of the subgrade, in particular the inclination of the planarizing sheet of the screed assembly. In the case of a horizontal subgrade, the angle of attack of the screed assembly corresponds to the absolute inclination of the planarizing sheet. The term "absolute inclination" indicates that the inclination is determined relative to a horizontal plane. In the case of a sloped subgrade, the angle of attack corresponds to the difference between the absolute inclination of the planarizing sheet and the absolute inclination of the subgrade.
[0016] The angle of attack of the base screed may refer to the inclination of the base screed, in particular the inclination of the base screed leveling sheet, relative to the inclination of the subgrade. The angle of attack of the extension may refer to the inclination of the extension, in particular the inclination of the extension leveling sheet, relative to the inclination of the subgrade.
[0017] The screed assembly may be rotatably attached to the towing point of the road paver, in particular to the towing point of the towing vehicle of the road paver, via at least one towing arm. The screed assembly may be attached to the towing point of the road paver, in particular to the towing point of the towing vehicle, via two towing arms. The towing arms may be arranged on the sides of the towing vehicle. One towing arm may be arranged on each of the sides of the towing vehicle. The height of the towing point may be adjusted by means of a heightening cylinder. The road paver may have two towing arms and two heightening cylinders. Each heightening cylinder may be assigned to a towing arm. The heightening cylinders may be connected to the respective towing arms. The heightening cylinders and the towing arms may be connected directly or via an intermediate member. The heightening cylinders and the towing arms may be arranged transversely to the cross direction of the road paver. The road paver may have a towing arm and a heightening cylinder on both sides. The features described below in the application with respect to the heightening cylinders also relate to both heightening cylinders, even if not explicitly mentioned.
[0018] The screed assembly, in particular the base screed, may be connected to the towing vehicle by a screed lifting cylinder. The screed assembly, in particular the base screed, may be connected to the towing vehicle by two screed lifting cylinders. One or more screed lifting cylinders may be used to raise or lower the screed assembly vertically. One or more screed lifting cylinders may be used to adjust the ground pressure of the screed assembly against the paving material. The features described below with respect to the screed lifting cylinders also apply to both screed lifting cylinders, even if not explicitly mentioned.
[0019] The screed lifting cylinder may be directly connected to the screed assembly or to the base screed. The screed lifting cylinder may be indirectly connected to the screed assembly or to the base screed. The screed lifting cylinder may be attached to the towing arm, in particular to the rear region of the towing arm.
[0020] The road paver may have a material hopper that may contain the paving material and may be disposed in front of the screed assembly in the paving direction.
[0021] The road paver may have a controller. The controller may control the screed lift cylinder. The controller may control the levelling cylinder. The controller may control the screed lift cylinder and the levelling cylinder. The controller may be part of a feedback controller.
[0022] The feedback control device may comprise a first controller. The first controller may control one or more height adjustment cylinders based on a control deviation of the screed height. The control deviation of the screed height is the difference between a target value of the screed height, e.g. a desired laying height, and an actual value of the screed height. The control deviation of the screed height may be determined from 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 may be specified by manual input by the user. The target value of the screed height may be specified or suggested by the control system, in particular depending on the paving material. The target value of the screed height may be determined based on values recorded in past building operations. The target value of the screed height may be derived from the road construction plan. The target value of the screed height may be entered manually. The target value may also be taken directly from digital plan data.
[0023] The feedback control device may have a second controller. The second controller may control one or more screed lifting cylinders based on a control deviation of the angle of attack. The control deviation of the angle of attack is the difference between a target value of the angle of attack, e.g. a desired angle of attack, and an actual value of the angle of attack. The control deviation of the angle of attack may be determined from the desired value of the angle of attack and the actual angle of attack determined by the second measuring device. The second controller may calculate the required pressure in the screed lifting cylinder based on the determined actual angle of attack. The target value of the angle of attack may be specified by manual input by the user. The target value of the angle of attack may be specified or suggested by the control system, in particular depending on the paving material. The target value of the angle of attack may be determined based on values recorded in past construction operations. The target value of the angle of attack may be selected to match the height setting of the extension. This allows for good compaction regulation, which may result in a good paving pattern.
[0024] The feedback control device may have a first controller. The first controller may control the height adjustment cylinder based on the control deviation of the screed height. The feedback control device may have a second controller. The second controller may control the screed lifting cylinder also based on the control deviation of the screed height.
[0025] 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 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 controller.
[0026] The feedback control device may comprise a multivariable controller, which may control the height adjustment cylinder and the screed lifting cylinder based on the control deviation of the screed height and the control deviation of the attack angle. Both feedback control variables, the attack angle and the screed height, may be controlled with one controller, the multivariable controller. This makes it possible to take into account the interaction between the two controlled variables (the attack angle and the screed height) and the two actual variables (the height adjustment cylinder and the screed lifting cylinder). The multivariable controller may also be referred to as a MIMO controller (multiple input multiple output controller). The multivariable controller may be an H-infinity controller, an LQ controller or an LQG controller.
[0027] In systems known in the prior art, the current laying speed is usually included in the feedback control. With the feedback control device according to the invention, this is not necessary. The feedback control device, in particular the multivariable controller, may be adapted to output no other control variables than the attack angle and the screed height. The feedback control device, in particular the multivariable controller, may control the screed lifting cylinder and the height adjustment cylinder solely on the basis of the attack angle and the screed height, in particular on the basis of a target / actual attack angle comparison and a target / actual screed height comparison. The feedback control device, in particular the multivariable controller, may control the screed lifting cylinder and the height adjustment cylinder solely on the basis of the measurements from the first and second measuring devices. The feedback control device, in particular the multivariable controller, may control the screed lifting cylinder and the height adjustment cylinder without taking into account the laying speed. The feedback control device may select the control parameters depending on the laying speed. The feedback control device may control the screed lifting cylinder and the height adjustment cylinder depending on the laying speed. The feedback control device may apply a large controller amplification at high laying speeds and a small controller amplification at low laying speeds. The terms high, low, large and small should be understood in relation to each other.
[0028] The first measuring device may be a range finder, for example a laser range finder, a mechanical probe or an acoustic range finder.
[0029] The second metrology device may include a first inclination sensor. The second metrology device may include a second inclination sensor. The second metrology device may include a first inclination sensor and a second inclination sensor. The first inclination sensor may be located on the screed assembly. The second inclination sensor may be located on the tow vehicle.
[0030] The first inclination sensor may determine an inclination angle of the screed assembly relative to a horizontal plane. The second inclination sensor may determine an inclination angle of the tow vehicle relative to a horizontal plane. The second measurement device may determine an angle of attack of the screed assembly from the inclination angle of the screed assembly and the inclination angle of the tow vehicle.
[0031] The first inclination sensor may determine the inclination angle of the base screed relative to a horizontal plane. The first inclination sensor may determine the inclination angle of the extension relative to a horizontal plane. The inclination angle of the towing vehicle may correspond to the inclination of the roadbed. Alternatively, the inclination of the roadbed or the inclination angle of the towing vehicle may be determined from a digital terrain model. A second inclination sensor in the towing vehicle is not required in this case. The inclination angle may be calculated based on the measured inclination angle of the first inclination sensor and the inclination of the roadbed determined from the terrain model. A number of first inclination sensors may be mounted such that the inclination angle of the screed assembly is determined and controlled at a number of points, for example at two extensions. A number of second inclination sensors may be mounted such that the inclination angle of the towing vehicle is determined from an average value of the second inclination sensors.
[0032] The second measurement device may have an inclination sensor attached to the base screed or the extension. The inclination sensor may be configured to determine an inclination angle of the base screed or the extension relative to a horizontal plane. The road paver controller may determine the subgrade inclination based on the digital terrain model. The controller may determine an angle of attack of the base screed based on the determined inclination angle of the base screed and the subgrade inclination. The controller may determine an angle of attack of the extension based on the determined inclination angle of the extension and the subgrade inclination.
[0033] The second measurement device may comprise a rotation angle sensor. The rotation angle sensor may be arranged at the towing point of the towing vehicle. The rotation angle sensor may measure the inclination of the towing arm relative to the inclination of the towing vehicle. The screed assembly may be rigidly connected to the towing arm. The angle of attack of the screed assembly may then be determined via the inclination of the towing arm. The rotation angle measured at the towing point may correspond to the angle of attack.
[0034] The second measurement device may have a first rotation angle sensor on a first towing arm mounted on a side of the towing vehicle and a second rotation angle sensor on a second towing arm mounted on another side of the towing vehicle. The angle of attack of the screed assembly may then be determined based on an average value of the first and second rotation angle sensors.
[0035] The feedback controller and / or the controller may be configured to filter environmental influences. The feedback controller and / or the controller may be configured to filter influences due to vibrations and / or temperature variations. Advanced signal processing methods such as Kalman filters or state observers may be used for this purpose.
[0036] The screed assembly may have a base screed and at least one extension. The extension may be arranged at least partially offset from the base screed in the paving direction of the road paver. The extension may be arranged at least partially in front of or behind the base screed in the paving direction of the road paver. The extension may be arranged completely in front of or behind the base screed in the paving direction of the road paver. The base screed and the extension may have the same angle of attack. The extension may be arranged transversely to the cross direction adjacent to the base screed. The screed assembly may have two extensions. The extensions may be arranged on both sides of the base screed in the cross direction. The extensions may be laterally contractible and extendable to change the width of the screed assembly. The width of the screed assembly corresponds to the extension of the screed assembly in the cross direction. The extension may have a vertical offset with respect to the base screed. The vertical offset may be adjusted by a height adjustment device. Due to the geometric arrangement of the base screed and the extensions, the vertical offset is only optimal for a certain angle of attack. If the angle of attack is changed, the vertical offset must be adjusted, otherwise the base screed and the extensions will have different screed heights. This can leave marks of the extensions in the laid layer and cause non-uniformities in the cross direction. The screed assembly can also consist of only the base screed and no extensions.
[0037] The screed lift cylinder may have a pressure control on the piston side. The screed lift cylinder may be adapted to allow for unloading or loading of the screed assembly. This allows for correction of both under and over-angles of attack. A feedback control may adjust for under and over angles of attack.
[0038] A second aspect of the invention relates to a method for feedback controlling a position of a screed assembly of a road paver, the screed assembly being attached to a tow point of the road paver, in particular by at least one tow arm. The method comprises the steps of determining a screed height of the screed assembly and determining an attack angle of the screed assembly. The method further comprises adjusting the position, in particular the height, of the tow point based on the determined screed height. The method further comprises adjusting the ground pressure of the screed assembly based on the determined attack angle.
[0039] Adjusting the position of the tow point may include adjusting the height, vertical position, of the tow point.
[0040] The step of determining the screed height may be performed continuously. The step of determining the angle of attack may be performed continuously. The step of determining the screed height may be performed simultaneously with the step of determining the angle of attack. The steps of determining the screed height and / or the angle of attack may be performed at regular intervals.
[0041] The step of adjusting the position of the traction point may be performed continuously. The step of adjusting the ground contact pressure may be performed continuously. The step of adjusting the position of the traction point may be performed simultaneously with the step of adjusting the ground contact pressure. The step of adjusting the position of the traction point and / or the step of adjusting the ground contact pressure may be performed at regular intervals.
[0042] The step of adjusting the traction point position may occur after the step of adjusting the ground pressure. For example, the screed height may be determined first and the traction point position adjusted based thereon. The attack angle may then be determined and the ground pressure adjusted based thereon. The screed height may then be adjusted again and the traction point position adjusted. This iterative process may be repeated continuously.
[0043] The step of adjusting the position, in particular the height, of the towing point may be performed during operation of the road paver, in particular during laying of the paving material. The step of adjusting the contact pressure may be performed during operation of the road paver, in particular during laying of the paving material. The step of adjusting the position, in particular the height, of the towing point and the step of adjusting the contact pressure may be performed during operation of the road paver, in particular during laying of the paving material. During laying of the paving material, the road paver moves in the paving direction.
[0044] The step of adjusting the position, in particular the height, of the traction point may be performed automatically, in particular by a feedback control device or a control device. The step of adjusting the ground pressure may be performed automatically, in particular by a feedback control device or a control device. The step of adjusting the position, in particular the height, of the traction point and the step of adjusting the control device may be performed automatically, in particular by a feedback control device or a control device.
[0045] The determined screed height may be fed to a feedback controller or controller. The determined angle of attack may be fed to a feedback controller or controller. The determined screed height and the determined angle of attack may be fed to a feedback controller or controller.
[0046] The feedback control device may have a common multivariable controller for feedback controlling the screed height and the angle of attack. The multivariable controller may be an H-infinity controller, an LQ controller (Linear Quadratic Controller) or an LQG controller.
[0047] The feedback control may have two separate controllers. The feedback control may have a first controller for feedback controlling the screed height. The feedback control may have a second controller for feedback controlling the angle of attack.
[0048] The step of adjusting the position, particularly the height, of the traction point may additionally be based on the determined angle of attack. The step of adjusting the ground pressure of the screed assembly may additionally be based on the determined screed height.
[0049] The step of adjusting the position, in particular the height, of the towing point may be performed by means of a height adjustment cylinder, in particular two height adjustment cylinders. The height adjustment cylinders may be attached to the towing vehicle and to the towing point of the road paver. The position of the towing point may be changed by extending and retracting the height adjustment cylinders. The screed assembly may be attached to the towing point by means of a towing arm, in particular two towing arms. The screed height of the screed assembly may therefore be changed by extending and retracting the height adjustment cylinder or the height adjustment cylinders.
[0050] The adjustment of the ground pressure of the screed assembly may be performed by a screed lift cylinder, in particular two screed lift cylinders. The screed lift cylinders may be attached to the screed assembly and to the towing vehicle of the road paver. The pressure in the screed assembly may be varied by extending and retracting the screed lift cylinders. A pressure control valve may be used to adjust, in particular regulate, the pressure in the screed lift cylinders. The screed lift cylinders may have a rod side and a piston side. A pressure control valve may be used to adjust, in particular regulate, the pressure in the screed lift cylinders. The screed lift cylinders may be used to vary the pressure in the screed assembly. The pressure in the screed assembly may be varied with the pressure control valve. The screed lift cylinders may be adapted to remove and / or additionally apply a load on the screed assembly. The attack angle of the screed assembly may be adjusted by extending and retracting one or more screed lift cylinders. A higher ground pressure may result in a larger attack angle. A lower ground pressure may result in a smaller attack angle.
[0051] The screed lift cylinder may have a piston-side pressure control mechanism that may be used to increase the angle of attack.
[0052] A third aspect of the invention relates to the use of a feedback control device for feedback control of the angle of attack of a screed assembly of a road paver and for feedback control of the screed height of the screed assembly.
[0053] The feedback control device may be adapted to provide feedback control of the angle of attack and the screed height during operation of the road paver, in particular during laying of the paving material. The feedback control may be provided automatically. The feedback control may be provided continuously. The feedback control may be provided at regular intervals.
[0054] The feedback controller may receive and process measurements from the first measurement device determining the screed height and measurements from the second measurement device determining the angle of attack, and may provide feedback control based on the transmitted measurements of the screed height and the angle of attack.
[0055] The feedback control device may control the height adjustment cylinders, in particular the two height adjustment cylinders, which may change the position, in particular the height, of the towing arm connected to the screed assembly. The feedback control device may change the screed height by controlling the height adjustment cylinders.
[0056] The feedback control device may control the screed lifting cylinders, in particular the two screed lifting cylinders. The screed lifting cylinders may modify the ground pressure of the screed assembly on the paving material. The ground pressure may be used to adjust the angle of attack of the screed assembly. The feedback control device may modify the ground pressure of the screed assembly by controlling the screed lifting cylinders, in particular the screed lifting cylinders. The feedback control device may modify the angle of attack of the screed assembly by controlling the screed lifting cylinders, in particular the screed lifting cylinders.
[0057] The feedback control device may comprise a multivariable controller, which may be used for feedback controlling the angle of attack of the screed assembly and for feedback controlling the screed height of the screed assembly. The multivariable controller may use the determined angle of attack and the determined screed height as input parameters. The multivariable controller may control the height adjustment cylinders, in particular the height adjustment cylinders, and the screed lifting cylinders, in particular the screed lifting cylinders, in particular based on the determined screed height and the determined angle of attack.
[0058] The feedback control device may have a first controller and a second controller. The first controller may be used to feedback control a screed height of the screed assembly. The second controller may be used to feedback control an attack angle of the screed assembly. The first controller may be used to control a height adjustment cylinder, in particular a height adjustment cylinder. The second controller may be used to control a screed lifting cylinder, in particular a screed lifting cylinder.
[0059] The road paver according to the first aspect of the invention may be used with the method steps of the method according to the second aspect of the invention. The method according to the second aspect of the invention may be carried out on a road paver according to the first aspect of the invention. The use of the feedback control device according to the third aspect of the invention may be carried out on a road paver according to the first aspect of the invention and / or with the method steps of the method according to the second aspect of the invention.
[0060] The designations "first," "second," "third," and "fourth" should be understood as mere determination of a particular element or component, and do not necessarily imply a particular ordering of said components or elements. For example, the presence of a second component does not necessarily imply the presence of a first component, and vice versa.
[0061] The invention is explained in more detail below with reference to embodiments. [Brief description of the drawings]
[0062] [Figure 1] FIG. 1 shows a schematic side view of a road paver including a screed assembly according to an embodiment of the present invention. [Diagram 2] FIG. 2 shows a schematic top view of a road paver including a screed assembly according to an embodiment of the present invention. [Diagram 3] FIG. 3 shows a schematic side view of the screed assembly and tow arm in a first laying situation according to an embodiment of the invention. [Figure 4] FIG. 4 shows a schematic side view of the screed assembly and tow arm in a second installation situation according to an embodiment of the invention. [Diagram 5] FIG. 5 shows a schematic side view of the screed assembly and towing arm in a third installation situation according to an embodiment of the invention. [Figure 6] FIG. 6 illustrates a feedback control circuit known in the prior art for feedback controlling the position of the screed assembly. [Figure 7]FIG. 7 illustrates a feedback control circuit for feedback controlling the position of a screed assembly according to an exemplary embodiment of the present invention. [Figure 8] FIG. 8 illustrates a feedback control circuit for feedback controlling the position of a screed assembly according to an exemplary embodiment of the present invention. [Figure 9] FIG. 9 illustrates a feedback control circuit for feedback controlling the position of a screed assembly according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0063] FIG. 1 shows a road paver 1 according to an embodiment of the present invention. The road paver 1 comprises a towing vehicle 2 and a screed assembly 3. The screed assembly 3 is connected to the towing vehicle 2 by two towing arms 4 each extending laterally on the road paver 1. The towing arms 4 are pivotally connected to the towing vehicle 2 at a towing point 5. The screed assembly 3 is arranged behind the towing vehicle 2 with respect to the paving direction 100 and is towed behind the towing vehicle 2 by the towing arms 4. A material hopper 6 for containing paving material is arranged in the front area of the road paver 1. The paving material is transported backward in the paving direction 100 by a material transport device of the towing vehicle 2 and supplied to the screed assembly 3. A cross-direction distributor 7 for distributing the paving material perpendicular to the paving direction 100 in front of the screed assembly 3 may be provided in the rear area of the towing vehicle 2.
[0064] Height adjustment cylinders 8 are arranged on each side of the road paver 1. The height adjustment cylinders 8 are each connected to a towing arm 4 via an intermediate member 9. The position, in particular the height, of the towing point 5 can be adjusted by means of the height adjustment cylinders 8. Two screed lifting cylinders 10 are arranged in the rear region of the road paver 2. The screed lifting cylinders 10 are attached to the rear region of each towing arm 4. Alternatively, the screed lifting cylinders 10 may also be directly connected to the screed assembly 3. The screed lifting cylinders 10 can be used to adjust the position, in particular the height, and the ground pressure of the screed assembly 3.
[0065] FIG. 2 shows a top view of a road paver 1 according to an embodiment of the invention. The towing arm 4 is arranged on the side of the towing vehicle 2. The screed assembly 3 comprises a base screed 11 and two extensions 12. The extensions 12 are arranged behind the base screed 11 in the paving direction 100. Alternatively, the extensions 12 may be arranged in front of the base screed 11 in the paving direction 100. The extensions 12 are arranged laterally adjacent to the base screed 11 in the cross direction 200. The extensions 12 can be contracted and extended in the cross direction 200 so that the width of the screed assembly 3 varies. The width of the screed assembly 3 is the extension of the screed assembly 3 in the cross direction 200. The width of the screed assembly can be increased by assembling a widening part on the extension.
[0066] Figure 3 shows a schematic side view of the screed assembly 3 and towing arm 4 on a flat subgrade 13 in a first laying situation. The extension 12 is arranged behind the base screed 11 in the paving direction 100. The extension 12 and the base screed 11 have the same angle of attack 14. The dashed line represents the desired laying height 15 of the finished paving material. The base screed 11 and the extension 12 are arranged with a vertical offset. The vertical offset 16 between the base screed 11 and the extension 12 is adjusted so that the extension height 18 corresponds to the base screed height 17. This is usually adjusted manually before laying.
[0067] Figure 4 shows the screed assembly 3 and the towing arm 4 in a second laying situation. In comparison with Figure 3, the towing point 5 is higher. This results in a larger angle of attack 14. The angles of attack 14 of the base screed 11 and of the extension 12 are still equal. As can be seen from Figure 4, the base screed height 17 corresponds to the desired laying height 15. Due to the extension 12 being arranged behind the base screed 11 in the paving direction 100, the rear edge of the extension 12 is further down than the rear edge of the base screed 11. The extension height 18 is therefore smaller than the base screed height 17. This results in unevenness of the finished paving material in the cross direction.
[0068] FIG. 5 shows the screed assembly 3 and the towing arm 4 in a third laying situation. The subgrade 13 has a subgrade slope 19. In FIG. 5 only the base screed 11 is shown. The height adjustment cylinder 8 is attached to the front region of the towing arm 4 and adjusts the position of the towing point 5. The screed lifting cylinder 10 is attached to the rear region of the towing arm 4 and adjusts the ground pressure of the screed assembly 3 on the paving material. In the position of the screed assembly 3 shown in FIG. 5 the base screed height 17 corresponds to the desired laying height 15. The base screed 11 has an absolute base screed slope 20. The absolute base screed slope 20 is the slope of the base screed 11 relative to the horizontal plane. The attack angle 14 of the base screed 11 is calculated by subtracting the subgrade slope 19 from the absolute base screed slope 20.
[0069] FIG. 6 shows a feedback control circuit known from the prior art with a feedback control device 50 for feedback control of the position of the screed assembly 3. The screed transition behavior 51 is influenced by the screed lift cylinder pressure 52, the subgrade height 53 and the levelling cylinder position 54. The screed lift cylinder pressure 52 and the subgrade height 53 are external input parameters. Another input parameter is the desired laying height 15. The screed height 55 and the attack angle 14 are determined depending on the screed lift cylinder pressure 52, the subgrade height 53 and the levelling 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 laying height 15 with the measured screed height 55 and, if necessary, changes the levelling cylinder position 54. The controller 57 only reacts to changes in the screed height 55 and not to changes in the attack angle 14.
[0070] FIG. 7 shows a control circuit according to an exemplary embodiment of the present invention, comprising a feedback control device 50 for feedback controlling the position of the screed assembly 3. As shown in FIG. 6, the screed transition behavior 51 is influenced by the screed lift cylinder pressure 52, the subgrade height 53 and the leveling cylinder position 54. In comparison with the control circuit shown in FIG. 6, only the subgrade height 53 is an external input parameter. The desired laying height 15 and the desired attack angle 58 are specified as target values. The target values for the laying height 15 and / or the attack angle 58 may be specified by manual input by the user. The target values for the laying height 15 and / or the attack angle 58 may be specified or suggested by the control system, depending in particular on the paving material. The target values for the laying height 15 and / or the attack angle 58 may be determined based on values recorded in past building operations. 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 levelling cylinder position 54. The screed height 55 of the screed assembly 3 is measured by a first measuring device 59 and sent to a first controller 60. The first controller 60 compares the desired laying height 15 with the measured screed height 55 and changes the levelling cylinder position 54 as required. The attack angle 14 of the screed assembly 3 is measured by a second measuring device 61 and sent to a second controller 62. The second controller 62 compares the desired attack angle 58 with the measured attack angle 14 and changes the screed lift cylinder pressure 52 as required. The first controller 60 responds to the changes in the screed height 55 and the second controller 62 responds to the changes in the attack angle 14.
[0071] Figure 8 shows a control circuit according to a further exemplary embodiment of the present invention with a feedback control device 50 for feedback controlling the position of the screed assembly 3. In comparison with the control circuit shown in figure 7, the control circuit in figure 8 only comprises a first measuring device 59. The first measuring device 59 measures the screed height 55 of the screed assembly 3 and transmits it to a first controller 60 and a second controller 62. The first controller 60 compares the desired laying height 15 with the measured screed height 55 and changes the height adjustment cylinder position 54 if necessary. The second controller 62 compares the desired laying height 15 with the measured screed height 55 and changes the screed lift cylinder pressure 52 if necessary.
[0072] Fig. 9 shows a control circuit according to a further exemplary embodiment of the present invention, comprising a feedback control device 50 for feedback controlling the position of the screed assembly 3. In comparison with the control circuit shown in Fig. 7, the control circuit in Fig. 9 has a multivariable controller 63. A first measuring device 59 measures the screed height 55 of the screed assembly 3 and transmits it to the multivariable controller 63. A 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 laying height 15 with the measured screed height 55 and uses this to calculate the control deviation of the screed height. The multivariable controller 63 compares the desired attack angle 58 with the measured attack angle 14 and uses this to calculate the control deviation of the attack angle. Based on the control deviation of the screed height and the control deviation of the attack angle, the multivariable controller 63 changes the screed lifting cylinder pressure 52 and the height adjustment cylinder position 54 as required. The multivariable controller 63 can be a MIMO controller (multiple input multiple output controller).
Claims
1. A road paver (1), comprising: Towing vehicle (2); At least one towing arm (4); a screed assembly (3) attached to a towing point (5) of the towing vehicle (2) via the at least one towing arm (4); and a height adjustment cylinder (8) for adjusting the position, in particular the height, of the traction point (5); a screed lifting cylinder (10) for adjusting the ground pressure of the screed assembly (3); a first measuring device (59) for determining a screed height (55) of said screed assembly (3); A second measuring device (61) for determining the angle of attack (14) of the screed assembly (3); and A feedback control device (50) for controlling the height adjustment cylinder (8) and the screed lifting cylinder (10). A road paver (1).
2. 2. The road paver according to claim 1, wherein the feedback control system (50) comprises a first controller (60) for controlling the height adjustment cylinder (8) based on a control deviation of the screed height (55) and a second controller (62) for controlling the screed lifting cylinder (10) based on a control deviation of the attack angle (14).
3. 2. The road paver according to claim 1, wherein the feedback control device (50) comprises a first controller (60) for controlling the height adjustment cylinder (8) based on a control deviation of the screed height (55), and a second controller (62) for controlling the screed lifting cylinder (10) based on a control deviation of the screed height (55).
4. 2. The road paver according to claim 1, wherein the feedback control device (55) comprises a multivariable controller (63) for controlling the height adjustment 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).
5. the second measurement device (61) comprises a first inclination sensor arranged on the screed assembly (3) and a second inclination sensor arranged on the towing vehicle (2); the first tilt sensor determines the tilt angle of the screed assembly (3) relative to a horizontal plane; the second tilt sensor determines an angle of inclination of the towing vehicle (2) relative to the horizontal plane; 5. The road paver according to claim 1, wherein the second measuring device determines the angle of attack (14) of the screed assembly (3) from the inclination angle of the screed assembly (3) and the inclination angle of the towing vehicle (2).
6. Road paver according to any one of claims 1 to 5, wherein the second measuring device (61) comprises a rotation angle sensor arranged at the towing point (5) of the towing vehicle (2).
7. 7. The road paver according to claim 1, wherein the screed assembly (3) comprises a base screed (11) and at least one extension (12), the extension (12) being arranged at least partially offset from the base screed (11) in a paving direction (100) of the road paver (1), and the base screed (11) and the extension (12) having the same angle of attack (14).
8. 1. A method for feedback controlling the position of a screed assembly (3) attached to a tow point (5) of a road paver (1), comprising: determining a screed height (55) of said screed assembly (3); determining an angle of attack (14) of the screed assembly (3); adjusting the position, in particular the height, of the traction point (5) based on the determined screed height (55); and adjusting the ground pressure of the screed assembly (3) based on the determined angle of attack (14).
9. 9. The method according to claim 8, wherein the adjustment of the position, in particular the height, of the traction point (5) and the adjustment of the ground pressure are performed during operation of the road paver (1).
10. 10. The method according to claim 8 or 9, wherein the adjustment of the position, in particular the height, of the traction point (5) and the adjustment of the ground pressure are performed automatically, in particular by a feedback control device (50).
11. The method according to any one of claims 8 to 10, wherein the determined screed height (55) and the determined angle of attack (14) are fed into a feedback control system (50) of the road paver (1), the feedback control system (50) comprising a multivariable controller (63) or two separate controllers (60, 61) for controlling the screed height (55) and for controlling the angle of attack (14).
12. The method according to any one of claims 8 to 11, wherein the adjustment of the position, in particular the height, of the traction point (5) is additionally based on the determined angle of attack (14) and the adjustment of the ground pressure of the screed assembly (3) is additionally based on the determined screed height (55).
13. The method according to any one of claims 8 to 12, wherein the adjustment of the position, in particular the height, of the traction point (5) is performed by a heightening cylinder (8) and the adjustment of the ground pressure of the screed assembly (3) is performed by a screed lifting cylinder (10).
14. Use of a feedback control device (50) for feedback control of an angle of attack (14) of a screed assembly (3) of a road paver (1) and for feedback control of a screed height (55) of said screed assembly (3).
15. 15. Use of a feedback control device according to claim 14, wherein the feedback control device (50) comprises a multivariable controller (63) used for feedback control of the angle of attack (14) of the screed assembly (3) and for feedback control of the screed height (55) of the screed assembly (3), or the feedback control device (50) comprises a first controller (60) and a second controller (62), wherein the first controller (60) is used for feedback control of the screed height (55) of the screed assembly (3) and the second controller (62) is used for feedback control of the angle of attack (14) of the screed assembly (3).