YOLOv11模型改进-注意力-引入简单无参数注意力模块SimAM 提升小目标和遮挡检测

            本篇文章将介绍一个新的改进机制——卷积和注意力融合模块SimAM ，并阐述如何将其应用于YOLOv11中，显著提升模型性能。首先，SimAM 是一种用于卷积神经网络的简单且无参数的注意力模块，它基于神经科学理论定义能量函数来计算 3-D 注意力权重，能有效提升网络的表征能力，且具有轻量级、高效等优势。随后，我们将详细讨论他的模型结构，以及如何将SimAM 模块与YOLOv11相结合，以提升目标检测的性能。

1. SimAM 结构介绍          

      SimAM 的核心结构围绕其独特的注意力机制构建，以下是其主要结构特点：

        1. 能量函数计算部分：基于视觉神经科学理论，为每个神经元定义能量函数通过最小化这个能量函数，找到目标神经元与其他神经元的线性可分性，从而确定神经元在视觉处理中的重要程度。

        2. 特征精炼部分：缩放算子应用：根据哺乳动物大脑中注意力调制表现为对神经元反应的增益效应，使用缩放算子进行特征精炼。具体来说，通过来实现，其中包含所有通道和空间维度的（即每个神经元的最小能量），函数用于限制中的过大值，以确保特征精炼的合理性。

2. YOLOv11与SimAM 的结合

       本文将YOLOv11模型的C3K2模块相结合 ，组合成C3k2_simam模块。利用SimAM 能够推断 3 - D 注意力权重，同时考虑空间和通道维度的能力。这有助于C3K2模块更全面地关注目标的不同特征维度。

3. SimAM 代码部分

import torch
import torch.nn as nn
from .conv import Conv
from .block import C2f, C3, Bottleneck


class simam_module(torch.nn.Module):
    def __init__(self, channels=None, e_lambda=1e-4):
        super(simam_module, self).__init__()

        self.activaton = nn.Sigmoid()
        self.e_lambda = e_lambda

    def __repr__(self):
        s = self.__class__.__name__ + '('
        s += ('lambda=%f)' % self.e_lambda)
        return s

    @staticmethod
    def get_module_name():
        return "simam"

    def forward(self, x):
        b, c, h, w = x.size()

        n = w * h - 1

        x_minus_mu_square = (x - x.mean(dim=[2, 3], keepdim=True)).pow(2)
        y = x_minus_mu_square / (4 * (x_minus_mu_square.sum(dim=[2, 3], keepdim=True) / n + self.e_lambda)) + 0.5

        return x * self.activaton(y)



class Bottleneck_simam(nn.Module):
    """Standard bottleneck."""

    def __init__(self, c1, c2, shortcut=True, g=1, k=(3, 3), e=0.5):
        """Initializes a standard bottleneck module with optional shortcut connection and configurable parameters."""
        super().__init__()
        c_ = int(c2 * e)  # hidden channels
        self.cv1 = Conv(c1, c_, k[0], 1)
        self.cv2 = simam_module(c_)
        self.add = shortcut and c1 == c2

    def forward(self, x):
        """Applies the YOLO FPN to input data."""
        return x + self.cv2(self.cv1(x)) if self.add else self.cv2(self.cv1(x))

class C3k(C3):
    """C3k is a CSP bottleneck module with customizable kernel sizes for feature extraction in neural networks."""

    def __init__(self, c1, c2, n=1, shortcut=True, g=1, e=0.5, k=3):
        """Initializes the C3k module with specified channels, number of layers, and configurations."""
        super().__init__(c1, c2, n, shortcut, g, e)
        c_ = int(c2 * e)  # hidden channels
        # self.m = nn.Sequential(*(RepBottleneck(c_, c_, shortcut, g, k=(k, k), e=1.0) for _ in range(n)))
        self.m = nn.Sequential(*(Bottleneck_simam(c_, c_, shortcut, g, k=(k, k), e=1.0) for _ in range(n)))

# 在c3k=True时，使用Bottleneck_simam特征融合，为false的时候我们使用普通的Bottleneck提取特征
class C3k2_simam(C2f):
    """Faster Implementation of CSP Bottleneck with 2 convolutions."""

    def __init__(self, c1, c2, n=1, c3k=False, e=0.5, g=1, shortcut=True):
        """Initializes the C3k2 module, a faster CSP Bottleneck with 2 convolutions and optional C3k blocks."""
        super().__init__(c1, c2, n, shortcut, g, e)
        self.m = nn.ModuleList(
            C3k(self.c, self.c, 2, shortcut, g) if c3k else Bottleneck(self.c, self.c, shortcut, g) for _ in range(n)
        )


if __name__ =='__main__':

    simam = simam_module(256)
    #创建一个输入张量
    batch_size = 1
    input_tensor=torch.randn(batch_size, 256, 64, 64 )
    #运行模型并打印输入和输出的形状
    output_tensor =simam(input_tensor)
    print("Input shape:",input_tensor.shape)
    print("0utput shape:",output_tensor.shape)

 4. 将SimAM 引入到YOLOv11中

第一: 将下面的核心代码复制到D:\bilibili\model\YOLO11\ultralytics-main\ultralytics\nn路径下，如下图所示。

第二：在task.py中导入SimAM 包

第三：在task.py中的模型配置部分下面代码

第四：将模型配置文件复制到YOLOV11.YAMY文件中

# Ultralytics YOLO , AGPL-3.0 license
# YOLO11 object detection model with P3-P5 outputs. For Usage examples see https://docs.ultralytics.com/tasks/detect

# Parameters
nc: 80 # number of classes
scales: # model compound scaling constants, i.e. 'model=yolo11n.yaml' will call yolo11.yaml with scale 'n'
  # [depth, width, max_channels]
  n: [0.50, 0.25, 1024] # summary: 319 layers, 2624080 parameters, 2624064 gradients, 6.6 GFLOPs
  s: [0.50, 0.50, 1024] # summary: 319 layers, 9458752 parameters, 9458736 gradients, 21.7 GFLOPs
  m: [0.50, 1.00, 512] # summary: 409 layers, 20114688 parameters, 20114672 gradients, 68.5 GFLOPs
  l: [1.00, 1.00, 512] # summary: 631 layers, 25372160 parameters, 25372144 gradients, 87.6 GFLOPs
  x: [1.00, 1.50, 512] # summary: 631 layers, 56966176 parameters, 56966160 gradients, 196.0 GFLOPs

# YOLO11n backbone
backbone:
  # [from, repeats, module, args]
  - [-1, 1, Conv, [64, 3, 2]] # 0-P1/2
  - [-1, 1, Conv, [128, 3, 2]] # 1-P2/4
  - [-1, 2, C3k2_simam, [256, False, 0.25]]
  - [-1, 1, Conv, [256, 3, 2]] # 3-P3/8
  - [-1, 2, C3k2_simam, [512, False, 0.25]]
  - [-1, 1, Conv, [512, 3, 2]] # 5-P4/16
  - [-1, 2, C3k2_simam, [512, True]]
  - [-1, 1, Conv, [1024, 3, 2]] # 7-P5/32
  - [-1, 2, C3k2_simam, [1024, True]]
  - [-1, 1, SPPF, [1024, 5]] # 9
  - [-1, 2, C2PSA, [1024]] # 10

# YOLO11n head
head:
  - [-1, 1, nn.Upsample, [None, 2, "nearest"]]
  - [[-1, 6], 1, Concat, [1]] # cat backbone P4
  - [-1, 2, C3k2_simam, [512, False]] # 13

  - [-1, 1, nn.Upsample, [None, 2, "nearest"]]
  - [[-1, 4], 1, Concat, [1]] # cat backbone P3
  - [-1, 2, C3k2_simam, [256, False]] # 16 (P3/8-small)

  - [-1, 1, Conv, [256, 3, 2]]
  - [[-1, 13], 1, Concat, [1]] # cat head P4
  - [-1, 2, C3k2_simam, [512, False]] # 19 (P4/16-medium)

  - [-1, 1, Conv, [512, 3, 2]]
  - [[-1, 10], 1, Concat, [1]] # cat head P5
  - [-1, 2, C3k2_simam, [1024, True]] # 22 (P5/32-large)

  - [[16, 19, 22], 1, Detect, [nc]] # Detect(P3, P4, P5)

第五：运行成功

from ultralytics.models import NAS, RTDETR, SAM, YOLO, FastSAM, YOLOWorld

if __name__=="__main__":


    # 使用自己的YOLOv11.yamy文件搭建模型并加载预训练权重训练模型
    model = YOLO(r"D:\bilibili\model\YOLO11\ultralytics-main\ultralytics\cfg\models\11\yolo11_simam.yaml")\
        .load(r'D:\bilibili\model\YOLO11\ultralytics-main\yolo11n.pt')  # build from YAML and transfer weights

    results = model.train(data=r'D:\bilibili\model\ultralytics-main\ultralytics\cfg\datasets\VOC_my.yaml',
                          epochs=100, imgsz=640, batch=8)