Vehicle Pitching Reduction via Wheelbase and Pivot Geometry
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Solution Overview
Problem
Handle-type electric wheelchairs face challenges in maintaining driving performance and ride comfort, particularly on unpaved roads and bumps, due to the trade-off between wheel diameter and wheelbase length, which can lead to pitching during acceleration and deceleration.
Innovation Solution
The vehicle design incorporates a short wheelbase with specific geometric relationships between the wheelbase, wheel diameter, and seat height to optimize the moment acting on the pivot, including a wheelbase to wheel diameter ratio of WB/Dw ≤ 2.5, and height ratios such as 3.0 ≤ Hs/Hp ≤ 6.0, to reduce pitching by adjusting the position of the center of gravity relative to the pivot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer diameter of the wheels is increased to improve running performance on unpaved roads and bumps, then the driving performance is improved, but the wheelbase becomes short which causes pitching during acceleration and deceleration
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships between wheelbase (WB), wheel outer diameter (Dw), pivot height (Hp), and center of gravity position (Hs). The conditions WB/Dw ≤ 2.5 and 3.0 ≤ Hs/Hp define optimal parameter ranges that simultaneously achieve good running performance on unpaved roads and reduce pitching during acceleration and deceleration.
2Length of moving object
If the wheelbase is shortened to accommodate larger wheels within limited vehicle length, then the vehicle fits size constraints, but pitching occurs during acceleration and deceleration reducing passenger comfort
Solution Approach 1:
The patent resolves this contradiction by changing the parameter relationships through specific ratios. By maintaining WB/Dw ≤ 2.5 and 3.0 ≤ Hs/Hp, the design achieves compact vehicle length while larger wheels are accommodated, and simultaneously reduces pitching to maintain passenger comfort through optimized center of gravity positioning relative to the pivot.
3Length of moving object
If the wheelbase is shortened to improve maneuverability and compactness, then the vehicle becomes more compact, but pitching during acceleration and deceleration increases causing discomfort
Solution Approach 1:
The patent applies parameter changes by defining the relationship 3.0 ≤ Hs/Hp where Hs is the distance from the upper end portion of the front portion of the seat to the line of action of the driving force reaction at the pivot. This parameter optimization allows the wheelbase to be shortened for compactness while the specific center of gravity positioning compensates for pitching effects.
Data Source
AI summary
A vehicle includes a seat on which a passenger is to be seated, a rear suspension to support rear wheels, and a drive source to drive the rear wheels. Pivots of the rear suspension are located forward relative to a rotation shaft of the rear wheels. A relationship WB/Dw≤2.5 is satisfied, where WB is a wheelbase of the vehicle, and Dw is an outer diameter of the rear wheels. A relationship 3.0≤Hs/Hp is satisfied, where Hp is a height from a level road surface to the pivots, and Hs is a distance in an up-down direction between an upper end portion of a front portion of the seat and a line of action where a reaction of a driving force that the rear wheels receive from the road surface acts on the pivots.