Road Paver Screed Height Control to Limit Overshoot and Oscillation
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Solution Overview
Problem
Existing road paver control systems impose rigid height adjustment limits that are impractical in certain installation situations, limiting flexibility and potentially causing undesirable effects like overshoot and excessive oscillations.
Innovation Solution
A road paver with a control system that includes a height sensing device and an actuating cylinder, capable of adjusting the drawbar point height relative to a reference, with a control system that limits the actuator stroke based on a proportional maximum value derived from the control error, minimizing inertia-related issues and accommodating varying installation conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid height adjustment limit is imposed on the actuator cylinder, then the control system stability is improved, but the adaptability to different installation situations deteriorates
Solution Approach 1:
The patent applies dynamics by making the stroke limit dynamic rather than fixed. The control system calculates a time-varying stroke limit based on real-time control error magnitude, allowing the system to adapt the adjustment range according to current operating conditions. This resolves the contradiction by enabling large adjustments when needed (improving adaptability) while preventing excessive adjustments that cause instability (maintaining reliability).
Solution Approach 2:
The patent changes the parameter of stroke limit from a constant value to a variable value that depends on control error. By making the stroke limit proportional to the control error magnitude, the system automatically adjusts the allowed adjustment range based on current conditions. This parameter change enables the system to be both stable (by limiting strokes during normal operation) and adaptable (by allowing larger strokes when large adjustments are needed).
2Stability of the object's composition
If the actuator stroke is limited to a fixed maximum value, then the system oscillations are reduced, but the response speed to large height adjustments deteriorates
Solution Approach 1:
The patent makes the stroke limit dynamic based on control error magnitude. When large height adjustments are needed (large control error), the system allows larger strokes, enabling fast response. When small adjustments are sufficient (small control error), the system limits strokes to prevent oscillations. This dynamic approach resolves the contradiction between response speed and oscillation control.
Solution Approach 2:
The system prevents oscillations by anticipating them through real-time monitoring of control error magnitude. By setting appropriate stroke limits based on current error levels, the system prevents excessive adjustments that would cause oscillations before they occur. This preliminary anti-action allows the system to maintain stability while enabling fast response when needed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system allows for flexible operation by automatically adjusting to specific paving conditions, reducing overshoot and vibrations, thereby improving the precision and stability of the paving process.
Implementation Method 1
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.
Implementation Method 2
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.
Implementation Method 3
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
Implementation Method 4
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
Data Source
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AI summary
A road paver (1) comprises a tractor (2), a material hopper (3) arranged at the front of the tractor (2) in a direction of travel (R) and configured to receive paving material (4), and a screed (5) mounted on the tractor (2) by means of drawbars (6) so as to pivot about a drawbar point (7), allowing the screed (5) to be towed behind the tractor (2) in the direction of travel (R). The road paver further comprises a control system (11) comprising a height sensing device (10) configured to detect vertical movements of the screed (5) relative to a height reference (9) and to generate a height signal (12) based thereon, and an actuating cylinder (8) connected to the tractor (2) and to one of the drawbars (6) and configured to adjust the height of the drawbar point (7) relative to the tractor (2).The control system (11) is configured to compare the altitude signal (12) with a setpoint (13) and thereby calculate a control error (14), to limit a stroke (20) of the actuator (8) to a maximum value (17) based on the control error (14), wherein the maximum value (17) is proportional to the control error (14), and to adjust the actuator (8) based on the control error (14) and taking into account the maximum value (17).