Harvester Header Control for Uneven Terrain Tracking
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Solution Overview
Problem
Conventional harvesting machines face challenges in maintaining consistent cutting height over uneven terrain, as tilting motions affect supporting forces detected by ground pressure sensors, leading to potential header contact with the ground and unwanted cutting-height fluctuations, requiring a compromise between stability and reaction rate.
Innovation Solution
A self-propelled harvesting machine with a control unit featuring a first control loop for height correction and a second control loop for pressure correction, using proportional and integral controllers to rapidly adjust hydraulic pressure without destabilizing the header, and a low-pass filter to prevent extreme pressure spikes, allowing for rapid reaction to setpoint changes while minimizing tilting motions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the reaction rate of the control unit is increased to quickly track raised areas on the ground, then the header can negotiate uneven terrain more effectively, but the system becomes more sensitive to tilting motions causing instability and unwanted cutting-height fluctuations
Solution Approach 1:
The control unit is divided into two separate control loops: a first control loop that processes height sensor signals for cutting height control, and a second control loop that processes ground pressure potentiometer signals for tilting motion compensation. This segmentation allows each loop to operate independently with optimized response characteristics, enabling high reaction rate for terrain tracking while maintaining stability through dedicated tilting compensation.
Solution Approach 2:
The ground pressure potentiometers serve as intermediary sensors that detect tilting motions before they affect the cutting height. By measuring the supporting forces on the header and feeding this information to the second control loop, the system can compensate for tilting motions in advance, preventing instability while allowing the first control loop to maintain high reaction rate for terrain negotiation.
2Speed
If the control unit uses extreme pressure reduction to quickly lower the header in response to ground sensing band detection, then the header can respond rapidly to terrain changes, but this causes load relief indistinguishable from actual ground contact, delaying the reaction
Solution Approach 1:
The second control loop continuously monitors the ground pressure potentiometer signals and provides feedback on the actual supporting forces. This feedback mechanism allows the control unit to distinguish between pressure changes caused by intentional header lowering and those caused by actual ground contact, enabling rapid response without the confusion that caused delays in conventional systems.
Solution Approach 2:
The system performs preliminary compensation for tilting motions and pressure changes through the second control loop before the header actually contacts the ground. By anticipating and counteracting pressure fluctuations in advance, the system avoids the confusion that previously caused reaction delays, allowing the first control loop to respond immediately to genuine terrain changes.
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
This solution enables a better combination of stability and high reaction rate, reducing the risk of header contact with the ground and unwanted cutting-height fluctuations, by rapidly tracking pressure changes and compensating for tilting motions without destabilizing the header.
Implementation Method 1
at least one hydraulic adjusting mechanism (5) for adjusting the cutting height of the header (3)
Implementation Method 2
at least one pressure sensor (7) for detecting the hydraulic pressure at the adjusting mechanism (5)
Data Source
AI summary
A self-propelled harvesting machine includes a header, a hydraulic adjusting mechanism for adjusting the cutting height of the header, a height sensor for detecting the cutting height, a pressure sensor for detecting the hydraulic pressure at the adjusting mechanism and a control unit for actuating the adjusting mechanism on the basis of values measured by the height sensor and the pressure sensor. The control unit has a first control loop for generating a height-correction signal (hkorr) on the basis of the actual cutting height (hist) detected by the height sensor (10) and a setpoint cutting height (hsoll) and, a second control loop for regulating pressure at the adjusting mechanism, the setpoint value of which follows changes in the height-correction signal.