Differential Traction Steering for Obstacle-Resistant Robotic Mowers
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Solution Overview
Problem
Traditional robotic mowers face difficulties in steering over obstructions due to the traction wheel sinking, leading to steering faults and motor over-current issues, and lack of coordinated traction force, resulting in easy stalling and getting stuck.
Innovation Solution
A system and method for differential traction drive and steering axis coordination that calculates and applies left and right wheel speeds based on target forward speed, steering rotational speed, and wheel distances, using independent traction motors to assist steering, reducing motor stress and enabling continuous steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single steering motor controls the steering axle, then the steering mechanism is simple, but the motor experiences over-current and stalls when the traction wheel sinks into obstructions
Solution Approach 1:
The patent divides the steering control into two independent parts: a steering motor that controls the steering axle angle, and two independent traction motors that control the left and right wheel speeds separately. This segmentation allows the traction motors to provide differential traction forces that assist steering without overloading the steering motor, preventing stalls and over-current conditions.
Solution Approach 2:
The traction motors serve dual functions: they provide forward motion and simultaneously assist in steering by creating differential traction forces. This self-service approach eliminates the need for additional steering assistance mechanisms while improving steering reliability and reducing the burden on the dedicated steering motor.
2Device complexity
If traditional steered caster wheel design is used, then the steering structure is simple, but the device gets stuck easily when encountering obstructions
Solution Approach 1:
The patent implements dynamic speed control of the left and right traction wheels based on real-time steering requirements and obstacle conditions. By continuously adjusting the differential speed between wheels, the system adapts to varying terrain and obstacles, enabling the device to navigate over curbs, slopes, and irregular surfaces that would stall traditional fixed-gear designs.
3Reliability
If additional differential lock mechanism is added, then steering performance improves, but device complexity and reliability issues increase
Solution Approach 1:
The patent replaces mechanical differential lock mechanisms with an electronic control system that independently regulates the speed of left and right traction motors. This substitution eliminates complex mechanical linkages, moving parts, and locking mechanisms while achieving superior differential steering performance through electronic speed modulation, thereby reducing mechanical complexity and potential failure points.
Data Source
AI summary
A system and method for differential traction drive and steering axis coordination for an autonomous mower or other turf device includes initiating a steering motion based on determining a target forward speed and a steering rotational speed, calculating a left wheel speed and a right wheel speed, and applying the left and right wheel speeds, wherein the steering rotational speed is driven by a steering motor and the traction wheels associated with the autonomous mower, and the left and right wheel speeds are based on the target forward speed, a distance from a steering axle to the center of the respective wheel, and the steering rotational speed.