Autonomous Mower Path Planning for Slope Traction and Obstacle Avoidance
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Solution Overview
Problem
Autonomous lawn mowers face challenges in maintaining traction and avoiding obstacles, particularly on steep slopes and uneven terrains, leading to potential stalling and damage, which reduces their effectiveness and increases maintenance needs.
Innovation Solution
Implementing a path planning system that uses a predetermined terrain map to plan rotations and orientations of the machine, allowing it to traverse problem areas in optimal directions and avoid obstacles by analyzing the terrain and using sensors for real-time adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a level detector is used to sense steep grades and trigger evasive actions, then the machine can respond to terrain variations, but the machine may already have lost the ability to reverse or turn away from the boundary by the time the steep grade is sensed
Solution Approach 1:
The path planning system proactively identifies problem areas such as steep slopes and boundaries on the terrain map before the machine reaches them. The system plans rotations and orientation changes in advance to occur at optimal locations (e.g., flat areas before the slope) rather than waiting to sense the steep grade. This preliminary action ensures the machine maintains traction by being properly oriented before entering problematic terrain, eliminating the response time delay inherent in reactive level detector systems.
2Reliability
If evasive actions are taken when already on the steep grade, then the machine can attempt to exit the problem area, but the loss of traction may impede the ability of the autonomous mower to continue cutting grass throughout an intended work region
Solution Approach 1:
The system plans rotations to occur in flat areas before the machine enters steep slopes or problematic terrain. By preparing the correct orientation in advance on stable ground, the machine maintains traction when traversing the slope and can continue working without getting stuck, thereby preserving productivity and work region coverage.
Solution Approach 2:
The path planning system uses the terrain map as an intermediary to identify suitable rotation locations (flat areas) between the current position and the problem area. This intermediary flat area serves as a safe zone where the machine can reorient without losing traction, enabling successful traversal of steep grades and maintaining continuous work coverage.
3Reliability
If evasive actions are repeatedly taken on steep grade, then the machine may exit the problem area temporarily, but the actions will eventually wear down the surface so subsequent evasive actions in that area may eventually fail and the robot may become stuck
Solution Approach 1:
The system proactively plans rotations in flat areas before the machine enters steep slopes, eliminating the need for repeated evasive actions on the slope itself. By preparing the correct orientation in advance on stable ground, the machine traverses the slope without damaging the surface, preserving both traction conditions and surface integrity for future operations.
Solution Approach 2:
The path planning system prevents the harmful action of repeated evasive maneuvers on steep grades by proactively orienting the machine before entering the problem area. This preliminary anti-action avoids the wear and surface damage that would otherwise occur from repeated attempts to exit steep slopes, thereby maintaining long-term reliability and surface integrity.
4Device complexity
If the machine uses a differential drive system with only two powered wheels, then the power train is simplified compared to a four-wheel or all-wheel drive system, but the machine may become stuck on slopes with steep grades sufficient to cause a loss of traction
Solution Approach 1:
The path planning system compensates for the limited traction capability of the differential drive system by proactively planning rotations in flat areas before steep slopes. This ensures the machine approaches and traverses problem areas in optimal orientations, maximizing the effectiveness of the two powered wheels and preventing stalls without requiring a more complex four-wheel drive system.
Data Source
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AI summary
Operating an autonomous grounds maintenance machine includes determining a travel path for the machine to reach a destination waypoint in a zone of a work region. The travel path is analyzed for problem areas based on a predetermined terrain map. Rotations of the machine may be planned even before the machine begins to travel down the path to proactively prevent the machine from becoming trapped.