Vehicle Motion Control System for Reducing Pedal Bob and Wheel Lift
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Solution Overview
Problem
Existing bicycle suspension systems, such as single-pivot and Horst link designs, suffer from pedal bob and rear wheel lift due to uneven terrain, leading to loss of energy and control issues during pedaling and acceleration.
Innovation Solution
A motion control system with a geometric arrangement that connects the forward and rear frame portions of a vehicle, using a combination of sliding elements and rigid links to maintain equilibrium between forces from the drivetrain and user acceleration, preventing rear wheel lift and energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single-pivot rear suspension is used to cushion the rider from uneven terrain, then comfort and control are improved, but pedal bob and rear wheel lift occur causing energy loss
Solution Approach 1:
The suspension system is divided into multiple independent links (front link, rear link, fourth link) that can move independently to handle different forces. The front link handles braking forces while the rear link handles driving forces, preventing the pedal bob effect while maintaining comfort.
Solution Approach 2:
A fourth link is introduced as an intermediary element connecting the front and rear links to the swingarm. This intermediate component helps isolate and manage the complex forces from pedaling and braking, preventing energy loss while maintaining suspension function.
2Object-generated harmful factors
If a Horst link suspension with four-bar linkage is used to isolate pedal forces, then pedal bob is reduced, but the system complexity increases
Solution Approach 1:
The four-bar linkage is segmented into distinct functional links (front link for braking, rear link for driving forces) with clear separation of responsibilities. This modular approach reduces complexity by making each link's function explicit and manageable.
Solution Approach 2:
The suspension system incorporates dynamic elements including a shock absorber that can adjust its characteristics, and links that can move relative to each other to adapt to different riding conditions, reducing the need for overly complex fixed-geometry mechanisms.
3Loss of energy
If the rear suspension compresses during acceleration to provide anti-squat, then energy loss from squat is reduced, but the suspension restricts movement acting like a rigid frame
Solution Approach 1:
The shock absorber is configured to provide progressive resistance to compression, allowing free movement during normal riding while providing increasing anti-squat support during hard acceleration. This dynamic adjustment prevents the suspension from acting like a rigid frame while maintaining energy efficiency.
Solution Approach 2:
The suspension system changes its mechanical parameters (lever arm positions, link orientations) as it moves through its range of motion, providing different levels of anti-squat at different points in the travel to balance energy conservation with movement freedom.
Data Source
AI summary
A vehicle includes a forward frame portion, a rear frame portion, and a motion control system that movably interconnects the forward frame portion and the rear frame portion. A forward acceleration of the rear frame portion resulting from a driving force imparted by a wheel supported by the rear frame portion imparts a first force onto the motion control system that counters a second force imparted on the motion control system by an acceleration of a payload supported by the forward frame portion as a result of the forward acceleration.