Vehicle Suspension Control Using Three Accelerometers
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Solution Overview
Problem
Existing suspension systems for vehicles, particularly those with four semi-active suspensions, often require multiple accelerometers to control damping, leading to increased manufacturing costs and potential discomfort due to inappropriate damping selection during low-frequency events, which can cause undesired vibrations.
Innovation Solution
A control method using three accelerometers to estimate the vertical acceleration of all four semi-active suspensions, calculating damping coefficients based on both energizing frequency and energy entity, allowing for smoother transitions and reduced vibrations by minimizing vertical and pitch dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If four accelerometers are used to measure vertical acceleration at each suspension, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent uses three accelerometers to measure vertical accelerations at three corners of the vehicle body, then calculates the acceleration at the fourth corner through mathematical computation rather than using a fourth physical accelerometer. This copying approach reduces component count while maintaining measurement capability.
Solution Approach 2:
The control unit acts as an intermediary that processes the acceleration data from the three accelerometers and computes the fourth acceleration value. This intermediary computation replaces the need for a fourth physical sensor, reducing system complexity.
2Reliability
If maximum damping coefficient is selected based on body dynamics frequency, then ride comfort is improved for high-frequency events, but undesired vibrations occur during low-frequency events due to excessive damping
Solution Approach 1:
The patent dynamically adjusts the damping coefficient based on the measured acceleration characteristics. By analyzing the frequency content and magnitude of acceleration signals, the system selects appropriate damping values (minimum, intermediate, or maximum) to match the actual road conditions, avoiding excessive damping during low-frequency events.
Solution Approach 2:
The damping coefficient parameter is changed based on the analyzed acceleration characteristics. The system transitions between different damping states (minimum, intermediate, maximum) by comparing the measured acceleration magnitude and frequency against predetermined thresholds, optimizing performance for different road conditions.
3Ease of operation
If discontinuous damping coefficient selection is used, then control simplicity is maintained, but comfort is reduced due to abrupt transitions during low-frequency events
Solution Approach 1:
The patent introduces dynamic intermediate damping coefficients that are calculated based on the measured acceleration characteristics. This allows smooth transitions between minimum and maximum damping states, improving comfort during low-frequency events while maintaining a relatively simple control structure.
Solution Approach 2:
The damping coefficient is adjusted through multiple discrete levels (minimum, intermediate, maximum) selected based on acceleration analysis. This stepped parameter change approach provides smoother transitions than binary switching while keeping the control logic manageable.
Data Source
Figure 1~5
Figure 2
Figure 3~4
AI summary
A method for controlling four semi-active suspensions (5) of a vehicle (1) comprising the steps of: determining, for each semi-active suspension (5), a first and a second signal representative of the acceleration and speed of the sprung mass (Msi); determining, for a pair of semi-active suspensions (5) arranged on one side (Dx,Sx) of the vehicle (1) a third and a four signal representative of the acceleration and pitch speed (1); calculating for each semi-active suspension (5), a first damping coefficient (cHi) as a function of the difference between the first and second signal squared; calculating for each semi-active suspension (5), a second damping coefficient (cPi) as a function of the difference between the third and the four signal squared; for each semi-active suspension (5), comparing the first (cHi) and the second damping coefficient (cPi) for determining the higher coefficient; applying to each force generator device (7), an electronic control signal (Sci) indicative of the respective high damping coefficient (cTi).