Center-of-mass height estimation using suspension bearing capacity
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Solution Overview
Problem
Existing center-of-mass estimation techniques for commercial vehicles are inaccurate due to varying load arrangements and masses, which change significantly when the vehicle stops at distribution bases, making it difficult to maintain a constant center of mass height estimation.
Innovation Solution
A center-of-mass height estimation device that includes a roll moment calculation unit, lateral acceleration measurement unit, mass measurement unit, transfer function calculation unit, and center-of-mass height calculation unit, which calculates the height from the roll center to the center of mass by dividing the gain of the transfer function by the mass of the sprung portion, using air suspensions to measure bearing capacities and displacements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the height of center of mass of occupant is considered constant as in Patent Literature 1, then the estimation process is simplified, but the estimation accuracy deteriorates when load arrangement or mass changes significantly
Solution Approach 1:
The invention dynamically adapts the center of mass height estimation by detecting whether the vehicle is in a loaded state (commercial vehicle with significant load) or unloaded state (passenger vehicle). Based on this detection, the system switches between different estimation approaches: using actual load center of mass height when loaded, and using occupant center of mass height when unloaded. This dynamic adaptation resolves the contradiction by selecting the appropriate model based on operating conditions.
Solution Approach 2:
The invention changes the estimation parameters based on vehicle state. When the vehicle is determined to be in a loaded state, it uses the center of mass height of the load (which can be significantly different from occupant height) as the estimation parameter. When unloaded, it reverts to using occupant center of mass height. This parameter switching allows accurate estimation across different operating conditions without overly complicating the system.
2Adaptability or versatility
If the vehicle is designed to handle varying load conditions, then versatility is improved, but the center of mass height estimation becomes less reliable
Solution Approach 1:
The system dynamically detects the vehicle's load state and adapts the estimation method accordingly. By using a state detection mechanism that identifies whether the vehicle is carrying significant load, the system switches between different center of mass height models, ensuring reliable estimation regardless of the vehicle's adaptability to different load conditions.
Solution Approach 2:
The invention incorporates feedback through state detection that monitors vehicle loading conditions. Based on this feedback, the system determines whether to use load-based or occupant-based center of mass height estimation, thereby maintaining reliability across varying load conditions that the vehicle is designed to handle.
3Measurement precision
If external facilities are used for accurate measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The invention enables the vehicle's existing suspension system to serve dual purposes: both supporting the vehicle and providing measurement data for center of mass height estimation. By utilizing bearing capacity information already available from the suspension system, the invention achieves accurate measurement without requiring additional external facilities, thereby maintaining measurement precision while avoiding increased device complexity.
Data Source
AI summary
A center-of-mass height estimation device includes a roll moment calculation unit for calculating roll moment of a sprung portion in a vehicle on the basis of bearing capacities of left and right suspensions provided on the vehicle, a lateral acceleration measurement unit for measuring lateral acceleration, which is acceleration in a width direction of the vehicle, a mass measurement unit for measuring mass of the sprung portion, a transfer function calculation unit for calculating a transfer function of the roll moment with respect to the lateral acceleration, and a center-of-mass height calculation unit for dividing the gain of the transfer function by the mass of the sprung portion to calculate a height from a roll center of the vehicle to a center of mass of the sprung portion.