Active Noise Cancellation in Agricultural Cabins
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Solution Overview
Problem
Self-propelled agricultural working machines, such as tractors and combine harvesters, face significant noise levels in the driver's cab due to uncoordinated noise damping, leading to annoying conditions for the driver, especially during noisy operations.
Innovation Solution
A compensator element with adjustable phase and amplitude is introduced to cancel out vibrations transmitted from outside the cab, utilizing a second transmission path with adjustable phase shift and damping to reduce noise levels, complemented by a frequency sensor and tunable frequency generators to target specific noise frequencies, and a control circuit for closed-loop noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive cavity resonators are used for noise reduction in the driver's cab, then high-frequency noise can be damped, but low-frequency vibrations cannot be effectively dampened and the overall noise reduction performance is limited
Solution Approach 1:
The patent replaces passive mechanical resonators with an active electronic system consisting of sensors, frequency generators, and speakers. This substitution enables the system to generate anti-phase sound waves that actively cancel vibrations across a broader frequency range, particularly effective for low-frequency vibrations that passive resonators cannot handle.
Solution Approach 2:
The system dynamically adjusts the frequency and amplitude parameters of the compensator element based on the detected vibration characteristics. By tuning the frequency generator to match the noise source frequency and adjusting the phase to 180 degrees, the system optimizes noise cancellation effectiveness across different operating conditions and frequency ranges.
2Productivity
If the working machine is used for noisy work, then productivity is improved, but the noise level in the cab reaches levels that are annoying for the driver
Solution Approach 1:
The system employs a feedback mechanism where sensors continuously monitor vibrations in the driver's cab, and the control unit adjusts the compensator element in real-time. This closed-loop control enables the system to maintain effective noise cancellation during various work operations, allowing the driver to operate the machine productively without being exposed to annoying noise levels.
3Loss of energy
If cavity resonators are coupled strongly to the cabin, then more vibration energy enters the resonators, but the quality of the resonators decreases and less vibration energy is destroyed
Solution Approach 1:
The patent replaces the passive resonator system with an active electronic compensation system. Instead of relying on mechanical coupling between resonators and the cabin, the system uses sensors to detect vibrations and speakers to generate anti-phase sound waves. This eliminates the trade-off between coupling strength and resonator quality, as the electronic system can achieve effective energy dissipation without compromising system quality.
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 approach significantly reduces noise levels in the cab by canceling out vibrations and noise, achieving a lower noise level than single-path transmission, while maintaining perceptibility of critical operating noise changes for the driver.
Implementation Method 1
a compensator element (38) with a phase and amplitude of the transmitted vibration adapted Phase and amplitude is drivable to emit a sound vibration that compensates for the vibration transmitted into the driver's cab
Implementation Method 2
the transmitter comprises a frequency sensor (20) arranged on a periodically moving element of the noise source and a first frequency generator that can be tuned using a frequency of the element detected by the frequency sensor
Data Source
Figure 1~2
Figure 3~4
AI summary
The machine has a driver's cab (18) and a chopping gear that is present outside the cab. The gear transmits vibration on a transmission path (21) into the cab. A loudspeaker (38) is driven with a phase and amplitude adapted to a phase and amplitude of the transferred vibration to emit a sound vibration for compensating the transferred vibration. Another path includes an angle transmitter (20) arranged at a periodically moved element of the gear, a voltage controlled oscillator (24) and frequency dividers (26a, 26b), which are tuned based on a frequency of the element.