Dual Bumper Detection for Autonomous Mowers to Avoid False Stops
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Solution Overview
Problem
Autonomous self-propelled mowing vehicles face issues with their impact detectors being triggered by plants to be mowed, leading to unnecessary stalls, and existing solutions are either ineffective or unsafe due to legal and safety concerns.
Innovation Solution
The implementation of a dual impact detection system, comprising a rigid first impact detector and a deformable second impact detector, allows the vehicle to differentiate between plant contact and hard obstacles, enabling safe operation and preventing unnecessary stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the impact detector is positioned at normal height to detect hard obstacles, then collision detection capability is improved, but the detector is triggered by plants causing unnecessary stalls
Solution Approach 1:
The impact detection function is segmented into two separate detectors: a first impact detector for hard obstacles and a second impact detector for plants. This segmentation allows each detector to be optimized for its specific detection target, preventing false triggering while maintaining reliable collision detection.
Solution Approach 2:
The second impact detector is designed with locally depressible elements that are softer and more compliant specifically for plant contact, while the first impact detector remains rigid for hard obstacle detection. This local quality differentiation enables selective response to different obstacle types.
2Reliability
If the impact detector is made more sensitive to prevent missing hard obstacles, then safety is improved, but it becomes overly triggered by plant contact
Solution Approach 1:
The detection system is segmented into two sensitivity levels: the first impact detector with high sensitivity for hard obstacles and the second impact detector with lower sensitivity calibrated for plant contact. This segmentation resolves the contradiction by providing appropriate sensitivity for each obstacle type.
Solution Approach 2:
The physical parameters of the impact detectors are changed: the first detector uses a rigid structure with high sensitivity settings, while the second detector uses softer, more compliant material with adjusted sensitivity thresholds. This parameter differentiation allows each detector to respond appropriately to its target obstacle type.
3Productivity
If the impact detector is positioned higher above plants to avoid plant triggering, then false triggering is reduced, but collision detection capability is reduced
Solution Approach 1:
The detection system is segmented vertically and functionally: the first impact detector is positioned higher for hard obstacle detection while the second impact detector is positioned lower near the mowing elements for plant contact detection. This segmentation allows both detection capabilities to coexist without interference.
Solution Approach 2:
The solution moves from a single-point detection approach to a distributed detection approach across multiple spatial dimensions. The two impact detectors are positioned at different heights and locations, creating a multi-dimensional detection network that can distinguish between plant contact and hard obstacles based on spatial information.
Data Source
AI summary
An autonomous self-propelled mowing vehicle includes a frame fitted with a drive mechanism, a mowing device for mowing plants, a bumper device, and a control unit. The bumper device includes a first and a second impact detector. The first impact detector is depressible up to a stop and is provided with a first switch which emits a first signal to the control unit at a first switching point, if the first impact detector is depressed beyond the switching point. The second impact detector is deformable and locally depressible, and is provided with a second switch which emits a second signal to the control unit if the second impact detector is depressed at least beyond a predetermined depression threshold. The control unit is configured to stop the drive mechanism upon receiving the second signal, and to regulate the drive mechanism in such a way that the speed of the mowing vehicle is reduced to a lower mowing speed upon receiving the first signal without receiving the second signal. This prevents plants to be mowed from pushing the bumper away across the bumper width beyond the switching point of the first impact detector, without losing its long depressibility, because the second impact detector, which itself has a much smaller depressibility, detects obstacles at the lower (mowing) speed by being depressed itself.