Mobile Robot Drive Wheel Pivot Geometry for Traction Balance
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Solution Overview
Problem
Existing mobile robot drive systems face challenges in balancing braking and acceleration performance due to the fixed nature of their support wheels, which do not provide driving or braking force, leading to inefficient traction and potential wheel spin during acceleration or braking.
Innovation Solution
A suspension system with a drive assembly that includes a control arm pivotably coupled to the chassis, allowing the drive wheel to adjust its engagement with the ground surface independently of the load, by altering the pivot location's height to balance braking and acceleration forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive wheel is engaged with the ground surface using a fixed support wheel configuration, then the mobile robot can maintain stable support, but the traction efficiency deteriorates during acceleration and braking due to wheel spin and lack of independent engagement adjustment
Solution Approach 1:
The mobile robot's wheel system is segmented into two independent subsystems: fixed support wheels for stable support and a drive assembly with suspension for active traction. This segmentation allows each subsystem to perform its specialized function without compromising the other, resolving the contradiction between stable support and traction efficiency.
Solution Approach 2:
The drive assembly incorporates a suspension system with a control arm that allows dynamic adjustment of the drive wheel's engagement with the ground surface. This dynamic capability enables the drive wheel to independently adjust its position and engagement force during acceleration and braking, improving traction efficiency while the fixed support wheels maintain stable support.
2Force
If the pivot location height is increased to improve braking performance through increased moment arm, then the braking power improves, but the acceleration power decreases due to increased drive load on the drive wheel
Solution Approach 1:
The system optimizes the pivot location height as a critical parameter to balance braking and acceleration performance. By carefully selecting the pivot location height, the design achieves an optimal compromise where the moment arm provides sufficient braking power while the drive load during acceleration remains manageable, allowing the suspension system to effectively engage the drive wheel with the ground surface.
3Force
If the drive wheel engagement force is increased to improve braking performance, then the frictional engagement increases providing additional braking power, but the drive load increases causing wheel spin during acceleration
Solution Approach 1:
The suspension system enables the drive wheel to dynamically adjust its engagement force with the ground surface based on operational conditions. During braking, the control arm allows increased engagement force for enhanced frictional engagement and braking power. During acceleration, the system modulates the engagement to prevent excessive drive load and wheel spin, thus resolving the contradiction between braking power and preventing wheel spin.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves improved braking performance without compromising acceleration by adjusting the pivot location, ensuring optimal traction and reducing wheel spin, thus enhancing the mobile robot's overall mobility.
Implementation Method 1
As the mobile robot accelerates or decelerates, the drive wheel exerts a drive force on the ground surface that creates a moment on the control arm about the pivot location. The moment can increase or decrease frictional engagement between the drive wheel and the ground surface
Implementation Method 2
The moment can increase or decrease frictional engagement between the drive wheel and the ground surface, depending on the direction of forces on the drive wheel. Increased frictional engagement can provide additional braking power or acceleration power
Implementation Method 3
A biasing member can have an upper end and a lower end. The lower end can be coupled with the chassis at a connection location and the upper end can be coupled with the control arm. The biasing member can be configured to bias the drive wheel to a disengaged configuration
Data Source
AI summary
A mobile robot can include a chassis and support wheels configured to support the chassis on a ground surface. The mobile robot can have a drive assembly that includes a drive wheel mounted to a control arm for moving the mobile robot. The control arm can pivot about a pivot axis. The pivot axis can be rearward of the axis of rotation of the drive wheel. The pivot axis can be lower than the axis of rotation of the drive wheel. The pivot axis can be lower than the axis of rotation for one or more of the support wheels. A biasing member can bias the control arm downward. Braking using the drive wheel can increase the force of the drive wheel against the ground. Accelerating using the drive wheel can decrease the force of the drive wheel against the ground.