Dynamic Band-Stop Filter for Road Surface Detection
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Solution Overview
Problem
Existing suspension control devices fail to accurately determine road surface conditions and adjust damping forces accordingly, leading to suboptimal vehicle performance and ride comfort.
Innovation Solution
A road surface determining device using a band-stop filter on wheel speed signals to assess road conditions, which informs a suspension control device to calculate and adjust damping forces based on these determinations, allowing for precise control of suspension damping in response to varying road surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed cutoff frequency band is used in the band-stop filter, then the device structure is simple, but the road surface condition determination accuracy deteriorates under varying wheel speeds
Solution Approach 1:
The band-stop filter's cutoff frequency band is made dynamically adjustable based on wheel speed signal characteristics. The control section changes the cutoff frequency band according to the detected wheel speed, allowing the filter to adapt to different operating conditions and maintain accurate road surface condition determination across varying speeds.
Solution Approach 2:
The cutoff frequency parameter of the band-stop filter is changed in response to wheel speed variations. By adjusting this critical parameter based on real-time wheel speed data, the system maintains optimal filtering performance for road surface condition detection without requiring a completely different filter structure.
2Measurement precision
If the cutoff frequency band is changed in accordance with wheel speed signal, then the road surface condition determination accuracy is improved, but the device complexity increases
Solution Approach 1:
The control section performs multiple functions: it detects wheel speed signals, analyzes their characteristics, and adjusts the band-stop filter cutoff frequency accordingly. This multi-functionality is achieved within a single control unit, avoiding the need for separate dedicated components for each function and thereby limiting the increase in overall device complexity.
3Speed
If steering torque is used for suspension control, then the response to steering maneuvers is improved, but the road surface condition adaptation capability deteriorates
Solution Approach 1:
The suspension control system merges steering torque-based control with band-stop filter-based road surface condition detection. By combining these two control strategies, the system maintains the rapid response to steering maneuvers provided by torque-based control while adding the road surface adaptability through frequency-based filtering and control adjustments.
Solution Approach 2:
The system uses feedback from the band-stop filter analysis of wheel speed signals to continuously adapt suspension control parameters. This feedback mechanism allows the suspension to adjust its behavior based on detected road surface conditions while maintaining responsiveness to driver steering inputs.
Data Source
AI summary
A road surface condition is determined appropriately. A road surface determining section (84) configured to determine a road surface condition with reference to a wheel speed signal indicative of wheel speeds includes a band-stop filter (841) which acts on the wheel speed signal and has a cutoff frequency band which is changed in accordance with the wheel speed signal.