基于序列图像学习的巷道掘进机定位方法

Sequentialimage learning-based localization for roadheaders

  • 摘要: 煤矿综掘工作面受限于狭小空间、工艺繁杂、环境恶劣等特殊条件,导致用工多、安全性差、效率低等问题,亟需研发更加安全高效的智能化掘进技术与装备。巷道掘进机作为综掘工作面的核心设备,对其智能化进行研究具有重要的社会价值和经济意义。为实现巷道掘进机的智能化作业,首先需要解决的关键问题是为掘进机机体定位,精确、鲁棒的机体位姿检测方法是保障巷道智能掘进有效性的首要条件。因此,针对巷道掘进机机体定位问题,提出了一种基于时间序列图像学习的机体绝对六自由度位姿实时检测方法。首先,通过在掘进机机体安装一台单目相机,并在掘进机后方设置人工特征对象,设计适用于巷道狭长、非结构化环境的视觉定位方案。然后,提出用于时间序列图像融合的深度学习模型,其中,使用一种训练好的多尺度变分自编码器辅助的卷积神经网络(MSVAE-CNN)的编码器模型提取时间序列图像中每个样本的多尺度潜在空间特征,以保证图像特征提取的鲁棒性;基于双向长短期记忆(LSTM)网络构建时间序列图像特征融合模型,并同时估计所有时间步图像样本对应的机体位姿参数,当推理某个时间步图像对应的位姿参数时,其他时间步的信息都可作为先验知识,通过学习图像样本之间的特征相关性,提高位姿估计的精度和可靠性;另外,使用多头自注意力机制进一步提高特征融合性能,使用张量训练分解压缩模型,实现在轻微损失位姿估计精度的前提下大幅降低模型参数数量。最后,基于一辆履带小车进行试验研究,使用NOKOV红外动捕系统获取小车机体实际位姿。试验结果显示,所提方法对中心偏距和方向角的估计平均绝对误差分别约为25 mm和0.36°,完全能够满足巷道掘进机的定位需求,并且定位精度明显优于MSVAE-CNN模型,验证了所提出的基于序列图像学习的机体定位方法的有效性与高性能。

     

    Abstract: The coalmine comprehensive excavation face is characterized by high labor, poor safety, and low efficiency due to the special conditions of narrow space, complex technics, and extreme environment. Thus intelligent excavation technology and equipment should be developed to improve the safety and efficiency of roadway excavation. The roadheader is the core equipment for roadway construction, and the research on its automation and intelligence is of great value to society and economy. In order to realize the automation of roadheader, the problem of pose detection of the roadheader body should be solved first, and an accurate and robust self-positioning method is the premise to guarantee the effectiveness of intelligent excavation. Therefore, aiming at the problem of localization for the roadheader body, this paper proposes a time-sequence image learning-based real-time absolute 6-DoF pose detection method. Firstly, the visual positioning scheme is designed for a narrow and unstructured roadway environment by mounting a monocular camera on the roadheader body and setting an artificial feature object at a certain distance behind the roadheader. Then, the time-sequence image fusion deep learning model is presented, in which the encoder model of the well-trained multi-scale variational autoencoder-aided convolutional neural network(MSVAE-CNN) is employed to obtain the multi-scale latent features of each sample in time-series images and guarantee the robustness of image feature extraction. The feature fusion model for the time series images is constructed based on the bidirectional long short-term memory(LSTM) network, and the body poses corresponding to all time-step images are estimated simultaneously. The information of all other time steps can be used as prior knowledge when inferring the pose parameters corresponding to a certain time step image. And the accuracy and reliability of pose estimation can be improved by learning the feature correlation between image samples. In addition, the multi-head self-attention mechanism is used to further improve the feature fusion performance, and the tensor train decomposition is employed to compress the model, which can greatly reduce the number of model parameters with a slight loss of pose estimation accuracy. Finally, a small crawler-type vehicle is used for experimental study, and the NOKOV Motion Capture System is utilized to obtain the actual pose of the vehicle. The experimental results show that the estimation mean absolute errors of the proposed method are about 25 mm and 0.36° for the center offset and the yaw angle, respectively, which are fully capable of meeting the positioning requirements for roadheaders and significantly better than that of the MSVAE-CNN model. Thus the effectiveness and high performance of the proposed sequential image learning-based localization method can be demonstrated.

     

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