Paper · 2026 · Sensors

Star Lightweight Convolution and NDT-RRT: An Integrated Path Planning Method for Walnut Harvesting Robots

Xiangdong Liu; Xuan Li; Bangbang Chen; et al.

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Open access · cc-by

Abstract

To address issues such as slow response speed and low detection accuracy in fallen walnut picking robots in complex orchard environments, this paper proposes a detection and path planning method that integrates star-shaped lightweight convolution with NDT-RRT. The method includes the improved lightweight detection model YOLO-FW and an efficient path planning algorithm NDT-RRT. YOLO-FW enhances feature extraction by integrating star-shaped convolution (Star Blocks) and the C3K2 module in the backbone network, while the introduction of a multi-level scale pyramid structure (CA_HSFPN) in the neck network improves multi-scale feature fusion. Additionally, the loss function is replaced with the PIoU loss, which incorporates the concept of Inner-IoU, thus improving regression accuracy while maintaining the model's lightweight nature. The NDT-RRT path planning algorithm builds upon the RRT algorithm by employing node rejection strategies, dynamic step-size adjustment, and target-bias sampling, which reduces planning time while maintaining path quality. Experiments show that, compared to the baseline model, the YOLO-FW model achieves precision, recall, and mAP@0.5 of 90.6%, 90.4%, and 95.7%, respectively, with a volume of only 3.62 MB and a 30.65% reduction in the number of parameters. The NDT-RRT algorithm reduces search time by 87.71% under conditions of relatively optimal paths. Furthermore, a detection and planning system was developed based on the PySide6 framework on an NVIDIA Jetson Xavier NX embedded device. On-site testing demonstrated that the system exhibits good robustness, high precision, and real-time performance in real orchard environments, providing an effective technological reference for the intelligent operation of fallen walnut picking robots.

Abstract from the paper’s OpenAlex record; open copy licensed cc-by. Read at the source ↗

The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.

Claims 7

Method / resourceobservedoriginal resultpositivemeasured

Claim · model-written summary

YOLO-FW achieved 90.6% precision against the baseline.

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Walnutt0
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precisione0
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90.6%e0
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baseline modele0

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e0

“compared to the baseline model, the YOLO-FW model achieves precision, recall, and mAP@0.5 of 90.6%, 90.4%, and 95.7%, respectively”

✓ located verbatim in the source · abstract, characters 1085–1215 · show in text ↑
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“Walnut”

✓ located verbatim in the source · title, characters 81–87 · show in text ↑
Method / resourceobservedoriginal resultpositivemeasured

Claim · model-written summary

YOLO-FW achieved 90.4% recall against the baseline.

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Walnutt0
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recalle0
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90.4%e0
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baseline modele0

Verbatim

e0

“compared to the baseline model, the YOLO-FW model achieves precision, recall, and mAP@0.5 of 90.6%, 90.4%, and 95.7%, respectively”

✓ located verbatim in the source · abstract, characters 1085–1215 · show in text ↑
t0

“Walnut”

✓ located verbatim in the source · title, characters 81–87 · show in text ↑
Method / resourceobservedoriginal resultpositivemeasured

Claim · model-written summary

YOLO-FW achieved 95.7% mAP@0.5 against the baseline.

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Walnutt0
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mAP@0.5e0
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95.7%e0
Comparator
baseline modele0

Verbatim

e0

“compared to the baseline model, the YOLO-FW model achieves precision, recall, and mAP@0.5 of 90.6%, 90.4%, and 95.7%, respectively”

✓ located verbatim in the source · abstract, characters 1085–1215 · show in text ↑
t0

“Walnut”

✓ located verbatim in the source · title, characters 81–87 · show in text ↑
Method / resourceobservedoriginal resultpositivemeasured

Claim · model-written summary

YOLO-FW had a volume of 3.62 MB.

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Walnutt0
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volumee0
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3.62 MBe0

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e0

“with a volume of only 3.62 MB and a 30.65% reduction in the number of parameters”

✓ located verbatim in the source · abstract, characters 1217–1297 · show in text ↑
t0

“Walnut”

✓ located verbatim in the source · title, characters 81–87 · show in text ↑
Method / resourceobservedoriginal resultpositivemeasured

Claim · model-written summary

YOLO-FW reduced parameter count by 30.65%.

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Walnutt0
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number of parameterse0
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reductione0
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30.65%e0

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e0

“a 30.65% reduction in the number of parameters”

✓ located verbatim in the source · abstract, characters 1251–1297 · show in text ↑
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“Walnut”

✓ located verbatim in the source · title, characters 81–87 · show in text ↑
Method / resourceobservedoriginal resultpositivemeasured

Claim · model-written summary

NDT-RRT reduced search time by 87.71% with relatively optimal paths.

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Walnutt0
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search timee0
Direction
reducese0
Value
87.71%e0
Qualifier
relatively optimal pathse0

Verbatim

e0

“The NDT-RRT algorithm reduces search time by 87.71% under conditions of relatively optimal paths”

✓ located verbatim in the source · abstract, characters 1299–1395 · show in text ↑
t0

“Walnut”

✓ located verbatim in the source · title, characters 81–87 · show in text ↑
Method / resourceobservedoriginal resultpositivemeasured

Claim · model-written summary

On-site testing found the system robust, precise, and real-time in orchards.

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Walnutt0
Outcome
good robustness, high precision, and real-time performancee0
Setting
real orchard environmentse0

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e0

“On-site testing demonstrated that the system exhibits good robustness, high precision, and real-time performance in real orchard environments”

✓ located verbatim in the source · abstract, characters 1534–1675 · show in text ↑
t0

“Walnut”

✓ located verbatim in the source · title, characters 81–87 · show in text ↑