Active Wheel Damping via Anti-Causal Prediction
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Solution Overview
Problem
Conventional vehicle suspension systems fail to effectively reduce wheel hop and vertical displacement of the sprung mass due to their passive nature, which leads to undesirable wheel contact loss with the road, affecting handling and braking, and existing solutions with damping masses add weight and complexity.
Innovation Solution
The implementation of an active suspension system with an anti-causal filter and nonlinear filters that detect road disturbances ahead of the wheel, calculate an estimated response, and apply a scaled force before the wheel encounters the disturbance, using a controllable force source to reduce vertical motion of both the unsprung and sprung masses, without the need for damping masses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional passive suspension systems are used, then the system structure is simple, but the system fails to effectively reduce wheel hop and vertical displacement of the sprung mass
Solution Approach 1:
The anti-causal filter predicts future road disturbances and calculates the required suspension force in advance, allowing the controllable force source to prepare and apply the optimal force before the wheel actually encounters the disturbance, thereby preemptively preventing wheel hop and vertical displacement
Solution Approach 2:
The system uses sensors to detect actual wheel and sprung mass motion, feeds this information back to the controller, and continuously adjusts the controllable force source to maintain optimal suspension performance, creating a closed-loop control system that adapts to real-time conditions
2Reliability
If damping masses are added to reduce wheel hop, then wheel hop reduction improves, but vehicle weight and system complexity increase
Solution Approach 1:
The system replaces passive mechanical damping masses with an active electromagnetic controllable force source that can generate equivalent or superior damping effects through controlled electromagnetic forces, eliminating the need for additional physical mass while achieving the same wheel hop reduction
Solution Approach 2:
The controllable force source dynamically adjusts suspension stiffness and damping parameters in real-time based on predicted road conditions and actual vehicle response, allowing the system to achieve optimal wheel hop reduction without fixed mechanical damping components
3Reliability
If causal filters are used for road disturbance detection, then the system responds to actual disturbances, but the response occurs after wheel contact loss has already begun
Solution Approach 1:
The anti-causal filter processes sensor data to predict future road profile disturbances before the wheel encounters them, allowing the controller to calculate and prepare the optimal counteracting force in advance, so that when the disturbance occurs, the force is already applied or ready to be applied immediately, preventing wheel hop before it starts
Solution Approach 2:
The system applies a predictive counter-force that is the opposite of the anticipated disturbance effect, calculated using anti-causal filtering of road profile data, thereby creating a preemptive anti-action that neutralizes the disturbance before it can cause wheel hop or sprung mass displacement
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
An active wheel damper. An active suspension damps vertical displacement of an unsprung mass in a frequency range and reduces vertical displacement of a sprung mass in another frequency range.