Road Paver Screed Height Sensor Placement and Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for ensuring accurate layer thickness in road finishing are inefficient due to high costs and inaccuracies caused by multiple height sensors and complex signal processing, with a risk of leveling cylinders hitting the stop during correction.
Innovation Solution
Placing height sensors near the rear edge of the screed for precise measurements, using slope sensors for indirect height measurement, and implementing a self-learning control system that adjusts leveling cylinders via absolute strokes, automatically learning and correcting zero points to prevent overcorrection and ensure precise leveling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple height sensors are installed at different positions (front end, rear end, cross-distributing device, screed, drawbars) to measure thickness and control layer uniformity, then the accuracy of layer thickness control is improved, but the device complexity and cost increase significantly
Solution Approach 1:
The patent extracts the essential measurement function to a single critical location - the trailing edge of the screed. Instead of distributing multiple sensors throughout the system, only one height sensor is placed at the trailing edge where it directly measures the installation height. This extraction principle reduces the sensor network from multiple distributed sensors to a single critical measurement point, simplifying the system while maintaining control accuracy.
Solution Approach 2:
The patent introduces a longitudinal inclination sensor (slope sensor) as an intermediary device that indirectly provides height information through slope measurement. Rather than relying solely on direct height measurements from multiple sensors, the slope sensor acts as a mediator that, when combined with the single height sensor at the trailing edge, enables accurate determination of screed position and layer thickness without requiring multiple direct height measurement points.
2Reliability
If the leveling cylinder is actuated until the target slope is reached (as in conventional methods), then the slope control is achieved, but the leveling cylinder may reach its limit and fail to correct height deviations properly
Solution Approach 1:
The patent implements a feedback mechanism where the single height sensor at the trailing edge continuously monitors the actual installation height and compares it with the target height. The control system uses this feedback to determine when the trailing edge has reached the correct height, at which point the leveling cylinder is stopped. This feedback loop ensures that the leveling cylinder does not reach its limit unnecessarily, preventing both over-correction and failure to correct, thereby maintaining reliable slope control while ensuring accurate layer thickness.
3Manufacturing precision
If height sensors are positioned between the trailing edge of the screed and the leveling cylinder to achieve a compromise between accuracy and flatness, then some measurement capability is maintained, but the correction accuracy is reduced and the system requires considerable effort
Solution Approach 1:
The patent segments the control function by separating the measurement location (trailing edge of screed) from the actuation location (leveling cylinder). The single height sensor is positioned at the trailing edge to directly measure the installation height, providing maximum measurement accuracy. The control system then calculates the required correction and actuates the leveling cylinder accordingly. This segmentation allows the measurement to be as accurate as possible while the actuation system handles the correction, eliminating the need for sensors positioned in compromise locations.
Data Source
Figure 1
AI summary
The method involves calculating an absolute stroke for a leveling cylinder (Z) from a new actual differential measurement value and from an input construction ratio factor. The ratio factor is adjusted for the calculation of the absolute stroke by a self-learning construction ratio controller (R1) until a predetermined minimum value of the differential measurement value is reached. A new leveling cylinder adjustment position is selected as a new zero point (NP), and the predetermined minimum value is set to zero in a regulating system (R), when the predetermined minimum value is reached. An independent claim is also included for a regulating system for adjusting elevation position of a road paver, comprising a paving screed.