In-Line Two-Wheel Robot Control for Roll Stability at Speed
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Solution Overview
Problem
Existing two-wheeled robots face limitations in stability and control authority, particularly on uneven terrain and at higher speeds, due to their characteristic dimension and reliance on balancing dynamics, which restricts their height and efficiency in various applications, including package delivery.
Innovation Solution
The development of modern in-line two-wheeled vehicles (Twills) equipped with a front-wheel with a substantially vertical steering axis, a rear-wheel with a horizontal axis of rotation, and a control module that stabilizes the roll angle using sensors and actuators, allowing for efficient navigation and delivery of packages across various terrains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If balancing robots use inverted pendulum control dynamics to increase height, then the height is improved, but the control authority is reduced at higher speeds
Solution Approach 1:
The patent applies dynamics by making the wheelbase length variable through telescopic mechanisms. The wheelbase can extend to increase stability and control authority at higher speeds, and retract to allow greater height when speed is not critical. This dynamic adjustment resolves the contradiction by adapting the wheelbase length to the operational requirements.
Solution Approach 2:
The patent changes the parameter of wheelbase length from fixed to variable. By using telescopic wheel assemblies that can extend and retract, the system dynamically alters its characteristic dimension to maintain optimal control authority across different operating conditions, particularly at higher speeds where longer wheelbase provides better stability.
2Stability of the object's composition
If robots use wider wheel base to increase height stability, then the roll stability is improved, but the height is limited by the characteristic dimension
Solution Approach 1:
The patent uses dynamic telescopic wheelbase adjustment to decouple the relationship between wheelbase width and height. When height is needed, the wheelbase retracts; when stability is needed, the wheelbase extends. This dynamic adaptation allows the robot to achieve both tall height and adequate roll stability at different times without being constrained by a fixed wide stance.
Solution Approach 2:
The patent introduces temporal dimension to the wheelbase configuration. Instead of being constrained in a single static configuration, the wheelbase can transition between extended and retracted states over time, allowing the robot to optimize for height in one moment and stability in another, effectively adding a time dimension to the spatial configuration.
3Reliability
If servo motors are used for balancing control, then the control authority at zero speed is improved, but the torque available drops as speed increases
Solution Approach 1:
The patent dynamically adjusts the wheelbase length based on operating speed. At higher speeds where servo torque naturally decreases, the wheelbase extends to provide passive geometric stability, compensating for the reduced active control authority. At zero or low speeds, the wheelbase retracts to allow the servo motors to operate in their high-torque regime, maintaining control authority when needed.
4Stability of the object's composition
If additional degree of freedom is added to correct roll displacement, then the roll stability is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the roll stabilization function from the control system and implements it through passive mechanical means - the telescopic wheelbase geometry itself provides roll stability through its length adjustment. This eliminates the need for additional active degrees of freedom or complex control algorithms, reducing device complexity while maintaining roll stability.
Data Source
AI summary
Techniques are disclosed for exploiting modern controls, sensors and actuators to realize a novel family of in-line two-wheeled vehicles (Twills) as robots. Each robot has a front-wheel with a substantially horizontal axis of rotation and a substantially vertical steering axis. The front-wheel with its substantially vertical steering axis has a steering-angle that can be sensed by one or more sensors. There is a rear-wheel with a substantially horizontal axis of rotation. A control module stabilizes the roll angle when the robot is in a forward motion or when it is stopped. There is an energy source to power the controls and to drive one or both the front and rear wheels.