Vehicle Suspension Roll Stiffness Control via Actuator Feedback
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Solution Overview
Problem
Existing vehicle suspension systems face challenges in maintaining intended steer characteristics due to insufficient driving performance of actuators, leading to undesirable changes in roll stiffness distribution between the front-wheel and rear-wheel sides, causing either oversteer or understeer.
Innovation Solution
A suspension system with a roll stiffness distribution control device that adjusts target roll stiffness based on actual roll stiffness correspondence amounts, using a dependent target roll stiffness determining portion to ensure appropriate roll stiffness distribution ratios, even when actuator performance is insufficient, by determining target values for either the front or rear roll stiffness changing devices based on the counterpart's actual values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the actuator size is increased to improve driving performance, then the roll stiffness control capability is improved, but the installation space and permissible weight are exceeded
Solution Approach 1:
The control device determines the target roll stiffness correspondence amount in advance based on the actual roll stiffness correspondence amount of the counterpart side, before the actuator operates. This preliminary determination allows the system to account for actuator performance limitations and adjust control targets proactively, ensuring that the intended roll stiffness distribution is achieved even with limited actuator capability.
Solution Approach 2:
The system continuously monitors the actual roll stiffness correspondence amount and uses this feedback to adjust the target roll stiffness correspondence amount. By comparing the actual performance with the target and iteratively adjusting based on the counterpart side's actual values, the system compensates for insufficient actuator driving performance without requiring larger actuators.
2Productivity
If the actuator response speed is increased to improve operation amount, then the roll stiffness control responsiveness is improved, but the actuator complexity and power requirements increase
Solution Approach 1:
The control device calculates and determines the target roll stiffness correspondence amount in advance, before the actuator needs to execute the operation. This preliminary calculation allows the system to plan the required operation amount based on current vehicle state and counterpart side performance, reducing the need for high-speed response while maintaining control effectiveness.
Solution Approach 2:
The system determines the target roll stiffness correspondence amount based on the actual performance of the counterpart actuator, allowing for partial compensation when one actuator has insufficient response. By adjusting the target values dynamically, the system achieves acceptable roll stiffness distribution without requiring both actuators to have excessive performance capabilities.
3Stability of the object's composition
If the roll stiffness distribution is adjusted to maintain steer characteristic, then the vehicle handling stability is improved, but the control system complexity increases due to dependent target determination
Solution Approach 1:
The control device uses feedback from the actual roll stiffness correspondence amount of one actuator to determine the target roll stiffness correspondence amount of the other actuator. This feedback mechanism maintains the intended roll stiffness distribution ratio and steer characteristics by continuously adjusting targets based on actual performance, without requiring complex multi-variable control algorithms.
Solution Approach 2:
The target roll stiffness correspondence amount acts as an intermediary variable that mediates between the actual actuator performance and the desired roll stiffness distribution. By using this intermediate parameter, the system simplifies the control logic while maintaining stability, avoiding the need for complex direct control of multiple actuators simultaneously.
4Ease of manufacture
If both front and rear roll stiffness changing devices are made identical, then the manufacturing cost is reduced, but the driving performance of at least one actuator becomes insufficient
Solution Approach 1:
The control device applies different target roll stiffness correspondence amounts to the front and rear actuators based on their respective actual performance characteristics. By allowing local differences in control targets while using identical hardware, the system compensates for performance variations and ensures that each actuator operates within its capabilities to achieve the overall desired roll stiffness distribution.
Solution Approach 2:
The system changes the control parameters (target roll stiffness correspondence amounts) rather than the physical actuator parameters. By adjusting the target values dynamically based on actual performance, the system achieves differentiated control效果 with identical actuators, maintaining manufacturing simplicity while ensuring sufficient driving performance for each position.
Data Source
AI summary
In a target rotational angle determining routine, based on a roll moment and longitudinal acceleration that are calculated, target rotational angles of actuators on a subject side (one of front-wheel and rear-wheel sides) and a counterpart side are obtained using a common map. An actual rotational angle on the counterpart side is read. It is determined whether the absolute value of a difference obtained by subtracting the actual rotational angle supplied from the counterpart side from the target rotational angle on the counterpart side that is obtained by the subject side is equal to or greater than a set angle difference Δθ0. If YES, it is determined that roll stiffness on the counterpart side is insufficient, and the target rotational angle on the subject side is changed so that a roll stiffness distribution ratio between the front-wheel side and the rear-wheel side comes close to a set distribution ratio.