# Gesture Tracking and Recognition Algorithm for Dynamic Human Motion Using Multimodal Deep Learning

Authors: Zhonghua Xia; Jinming Xing; Xiaofeng Li
Journal: Security and Communication Networks
 (2022)

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## Abstract

To address the problems of the traditional human motion gesture tracking and recognition methods, such as poor tracking effect, low recognition accuracy, high frame loss rate, and long-time cost, a dynamic human motion gesture tracking and recognition algorithm using multimode deep learning was proposed. Firstly, the collected human motion images are repaired in the three-dimensional (3D) environment, and the multimodal 3D human motion model is reconstructed using the processed images. Secondly, according to the results of model reconstruction, the camera gesture and other parameters of the keyframe are used to construct the target tracking optimization function so as to achieve the purpose of accurate tracking of human motion. Finally, for multimodal human motion gesture learning, a convolutional neural network (CNN) is developed. The trained CNN is utilized to complete dynamic human motion recognition after convolutional and pooling calculations. The results demonstrate that the proposed algorithm is effective in tracking human motion gestures. The average recognition accuracy is 96%, the average frame loss rate is 8.8%, the time cost is low, and the proposed algorithm has a high F-measure and much lower power consumption than other algorithms, indicating that the proposed algorithm is effective.


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## Body

## 1. Introduction

The development of machine vision is inseparable from the wide application of Artificial Intelligence (AI) technology, and at present, the tracking and recognition of motion targets is a hotspot in the research on target tracking [1, 2]. Relevant researchers worldwide have made some achievements in the research of this field, which have been applied to various other fields [3]. For instance, in robot vision, the camera can be used to recognize objects; thus, finally, the target object can be grasped [4]. In addition, in some disaster rescue, accurate positioning of the trapped can be realized through target tracking, thus shortening the time for search and rescue [5].Human motion gesture means to determine the specific gesture of human motion by capturing the position of limbs. The realization process includes various modal information such as human motion trajectory, road signs, and gesture. In the multimodal interaction fusion, in order to make the Artificial Intelligence understand the external environment information and human gesture information, it must be given the ability to understand things; thus, the multimodal deep learning technology is proposed, through which the multimodal deep learning can effectively obtain various modal data, complete the conversion between different modalities, and then realize dynamic human motion gesture analysis. Multimodal deep learning has shown certain advantages in cognitive ability and information interaction and is very effective in the research of the human motion field. Literature [6] used multimodal deep neural networks to recognize human motion and design fine vision systems for target detection based on deep neural networks to accomplish real-time spatial occupancy perception and human motion analysis, but it is time-consuming. Literature [7] explored a deep learning system combining CNN and long short-term memory networks with visual signals to accurately predict human motion, which creatively extracts the temporal patterns of human motion and automatically outputs the prediction results before the motion occurs, improving the efficiency of feature extraction, but the accuracy is still low. Literature [8] proposed deep learning and applied it to daily human activities, detecting falls and monitoring gait abnormality detection in the context of data-driven motion classification, which discussed enhanced deep learning classification performance by comparison. However, time-consuming is long. Literature [9] proposed a multimodal deep learning model to achieve heterogeneous traffic data inference, which involves the use of two parallel stacked autoencoders that can consider both spatial and temporal dependencies; a hierarchical training approach was introduced in order to train the proposed computational model, the performance of which was verified through evaluation, but the algorithm runs with high power consumption. Literature [10] is based on a deep learning approach for multimodal complex activity recognition, which is an end-to-end model, which designs specific subnetwork architectures for different sensor data, merges the outputs of all subnetworks to extract fused features, and then uses neural networks to learn human motion sequence information, which is overall more complex and time-consuming. Based on multimodal deep learning, the main contributions of this paper are as follows: (1) The dynamic 3D image is restored by reconstructing the multimodal human 3D motion model, which provides a reference for target tracking and recognition and lays a solid foundation for subsequent tracking and recognition. (2) The target tracking optimization function is constructed by using the camera gesture and other parameters of the keyframe to improve the tracking accuracy of human motion gesture. (3) In the process of motion recognition, in order to ensure the effect of deep learning and reduce the corresponding training cost, CNN is introduced after convolutional computation and pool computation to reduce the computational complexity of multimodal training samples and improve the algorithm performance.


## 2. Related Works

At present, some achievements have been made in researches to track and recognize human motion gesture. Literature [11] proposed a dynamic gesture recognition method based on evidence theory that separates gestures from complex backgrounds and accurately tracks and locates gesture movements. However, time-consuming is long. Literature [12] used the concept of dynamic mapping for human motion recognition using pretrained models to encode the spatial, temporal, and structural information contained in video sequences as dynamic motion images simultaneously; based on CNN to accomplish dynamic motion recognition, the algorithm was able to generate effective flow-guided dynamic maps, but accuracy is low. Literature [13] applied augmented reality to 3D human motion recognition technology and proposed a sensor-based visual inertial initialization algorithm integrated into two-frame image intervals, which improved the accuracy of computing pose. However, the integrity was poor. Literature [14] proposed a human motion target recognition algorithm based on CNN and global constraint block matching, which achieves human motion target recognition by matching block scores and spatial constraint weight calculation, but power consumption is high. In literature [15], a target tracking recognition system was developed using an intelligent framework system with accurate camera positioning, fast image processing, multimodal information fusion capabilities, and an optimized neural network-based target recognition algorithm with strong robustness, but the fineness is not enough. Literature [16] relocated human motion in a complex environment with large displacements and introduced a new approach to human tracking using three deep CNN-based architectures with cascade learning, thus improving the overall efficiency of the model, but the time delay is large. Literature [17] proposed a small-sample human motion tracking recognition method based on carrier-free ultra-wideband radar. The human motion features are extracted using a combination of principal component analysis and discrete cosine transform, and a support vector machine optimized by an improved grid search algorithm is used to track and recognize human motion with small-sample data, which has a long running time.In the process of human motion tracking and recognition using the above methods, because the algorithms all use the general recognition and tracking algorithm to recognize the human motion and do not consider a variety of factors to optimize the tracking results of human motion gesture, the tracking and recognition effect of human motion is not good. Therefore, this paper proposes a dynamic human motion gesture tracking and recognition algorithm using multimodal deep learning.


## 3. Methodology

### 3.1. Reconstruction of Multimodal 3D Motion Model of Dynamic Human Motion

In the tracking and recognition of human motion gesture, we must first rely on the camera to collect the moving image of humans, carry out modeling and analysis in the background of tracking and recognition, and search for moving targets. Then, the camera gesture in the shooting process is determined, and the image is repaired according to the obtained moving image. Camera gesture refers to the motion of the camera with the dynamic human motion during shooting, including camera position and transformation. The sparse feature point algorithm is used to obtain the rough gesture and then minimize the distance from point to plane and the difference of pixel values to obtain the accurate gesture [18]. In 3D space, the obtained human motion model is a point cloud state. In order to realize human motion tracking and recognition, it is also necessary to reconstruct the point cloud and complete local optimization. According to the time sequence of the point cloud image, the point cloud is divided into active and inactive parts. The points reconstructed earlier are inactive points, but these points belong to more accurate points after optimization [19, 20]. The newly reconstructed points are active points and also belong to the points to be optimized. According to the position of the current frame, the point cloud is reconstructed by backprojection to obtain the depth image, including the depth image corresponding to active and inactive points. The two parts of point data are constrained and optimized to obtain a new gesture. Local optimization can keep the 3D reconstruction model results of human motion with high accuracy.After the local optimization is completed, global optimization is also needed. In this process, a keyframe database needs to be established to provide data for global optimization and closed-loop tracking and recognition. When there is enough parallax between the image frame and the previous keyframe and the matching points are less than a certain number, the current frame is added to the keyframe database as a keyframe. Global optimization uses all current keyframes, corresponding point cloud data, and camera gesture to construct an optimization problem to optimize camera gesture. Closed-loop detection of tracking and recognition is a judgment mechanism to detect whether the human motion has made previous motion. For the current frame, if the similarity with a keyframe in the keyframe database exceeds a certain value, it is determined that the closed loop is generated so as to keep the same keyframe at the same position successively.Point cloud refers to the collection of 3D points obtained from 3D reconstruction converted to the same coordinate system. The corresponding 3D point coordinates are calculated by using the obtained point cloud image. The transformation matrix coordinate system is transformed according to the previously determined camera gesture and fused with the original point according to the weight. Each 3D point contains not only location information but also semantic information. On this basis, the category probability needs to be saved and updated according to the Bayesian strategy. The original probability of human motion constructed by the current point cloud can be expressed as(1)Pli|I1,⋯,k−1,where li represents the category of human motion, Ii denotes the exact action associated with a specified number of frames during the motion, and the corresponding point probability of the current frame can be expressed as(2)POu=li|Ik,where Ou refers to the number of frames and Ik refers to the corresponding specific motion of a specific number of frames during motion. The calculation Equation is as follows (3).(3)Pli|I1,⋯,k=1ZPli|I1,⋯,k−1POu=li|Ik,where Z is a normalized constant. In this paper, the multimodal human 3D motion model is reconstructed by obtaining the 3D point cloud and fitting the plane in the 3D space, then reprojecting and filling the cavity area, and repairing the depth image.


### 3.2. Tracking Object of Determined

In order to change the new image frame into a keyframe, it is necessary to perform a global optimization operation to determine the tracking target. The camera gesture, 3D point coordinates, and their associated data of all the current keyframes are constructed into a target tracking optimization problem. It is shown in Figure1.Figure 1
Relationship between human motion trajectory, road signs, and gesture.According to Figure1. In the process of human motion gesture, a series of gestures will be generated and then connected through some observations to form the human motion trajectory. And what has been observed through the trajectory is the 3D spatial points that can be expressed by x1, x2, x3, and x4. First, the objects z1 and z2 in the surrounding environment are measured; then, the distance between the dynamic human motion and the marker is calculated to achieve targeting localization, and finally, the human localization of motion, object localization, and the 3D spatial information e2 are accurately calculated. At the moment k, from the estimated camera gesture zk, the results are shown in (4).(4)zk=hxk,where xk refers to the gesture of the current camera and h is the observation function.Supposezk∧ is the camera equipment observation of the current gesture. Due to the existence of error, the two observations may be inconsistent, so the error of this part needs to be calculated.(5)e=zk∧−zk.In the 3D modeling of wireless propagation without spatial segmentation acceleration, the original ray tracing algorithm is used to track and simulate the propagation process. According to the relationship between gesture and road signs, the human target tracking function is constructed, as shown in (6):(6)minx∑k=1nexk,zkTΩexk,zk,where Ω is the weight matrix, T is the error coefficient, and k=1,...,n refers to the number of points in the 3D space.The target tracking optimization function is constructed by using the camera gesture and other parameters of the keyframe so as to achieve the purpose of accurate tracking of human motion gesture. The function is actually a least square problem. Therefore, equation (6) needs to be expanded by the first-order Taylor equation and solved by the Gaussian Newton algorithm to obtain the final result, that is, the moving target tracking result.


### 3.3. Algorithm of Dynamic Human Motion Recognition

After the reconstruction of the multimodal human 3D motion model, the spatiotemporal representation of human motion multimodal data can be obtained. Therefore, it is necessary to use this result as the research basis to realize multimodal deep learning by using CNN in the process of human motion gesture recognition, which can reduce the computational cost to a certain extent [21]. Before convolution, the obtained moving image should be scaled. The scaling equation is(7)M′=floor255∗M−vminvmax−vmin,where M′ refers to the normalized matrix, M refers to the image matrix after preprocessing, vmin refers to the minimum value of pixel matrix in the image, vmax refers to the maximum value of the pixel matrix in the image, and floor. refers to the fuzzy function. After the linear transformation processing of equation (7), multiple captured human motion images can be scaled into gray images; that is, the gray value can be reduced from 0 to 255. The processed image is normalized into the input format of CNN and input into CNN [15, 16]. After convolution operation, the output error can be minimized in the process of image processing and in the process of learning. It is shown in Figure 2.Figure 2
Convolution process.With the characteristic map as the input, after convolution calculation, conduct 3 × 3 transformation of the input image to obtain the transformed block and the feature map. It can be seen that, after the convolution calculation process, the output depth of the obtained characteristic map increases. After the output of the feature image, it is also necessary to maximize the correlation between local data points [17]. In the CNN, the ultimate goal is to realize human motion gesture tracking and recognition [18]. Therefore, in the process of deep learning, it is necessary to design multimodal training samples:(8)xi,yii=1N,where xi and yi mean the different training sample sequences. When the value of yi is smaller than 1, the training sample refers to the modal C1, and when the value of yi is larger than 1, the training sample refers to the modal C2. In the process of classification, it is necessary to use the decision hyperplane equation:(9)gx=wTx+b,where x refers to the column vector, w refers to the decision vector of the hyperplane, and b refers to the decision bias of the hyperplane. The hyperplane can classify two categories of motion modes.(10)wTx+b=0.Then, the defined function interval can be written as(11)γi=yiw⋅xi+b.The corresponding geometric interval is as follows:(12)χi=1w⋅yiw⋅xi+b.In the actual convolution neural network, the above parameters are calculated, and the full connection layer is trained. Setting appropriate ratio parameters can reduce the coadaptation of neurons in the convolution neural network and ensure the training effect while preventing overfitting [19, 20]. The trained CNN is used to recognize human motion so as to achieve the relevant research objectives, as shown in Figure 3.Figure 3
The proposed algorithm process.


### 3.4. Experimental Environment and Data Set

In the process of tracking and recognition of dynamic human motion, the human motion data set is used as the basis. Therefore, this paper mainly relies on the smartwatch in the process of data acquisition. The relevant hardware equipment is needed to complete the tracking and recognition calculation, and the configuration of the relevant experimental equipment and parameters are shown in Table1.Table 1
Experimental environment parameters.
TypeModelParameterIntelligent watchTicWatch 1Built-in inertial sensor, 1.2 GHz Quad coreCameraTQ200240 GB SATA 3SensorMPU605050 × 22 mmHard diskSEAGATE3 TB, 64 M SATA3In the experiment process, multimodal deep learning needs a certain data set as support. This paper selects the public WISDM data set of wireless sensor data mining laboratory and the acceleration UCIHAR data set collected by smartwatch. For the WISDM data set, it includes different human motion gestures made by 30 volunteers, including walking, jogging, sitting, standing, going upstairs, and going downstairs. The behavior distribution of the above volunteers is shown in Figure4.Figure 4
Data of WISDM data set.The data set mainly collected volunteers’ forward and horizontal leg motion and body motion under different motions. Based on the WISDM data set, the UCIHAR data set collects the linear acceleration data of the leg forward, and horizontal motion decomposes the linear acceleration according to the angular velocity collected by the three-axis gyroscope sensor and obtains two types of motion: gravity and body activity. The data in the UCIHAR data set is collected by AirText equipped with smartwatch. Volunteers wear smartwatches in turn and then command volunteers to complete specified motions such as walking and standing. The sampling frequency can collect 50 data per second. The evaluation data set is separated into two parts: training and testing. Eighty percent of the data is utilized for training, while twenty percent is used for testing.


### 3.5. Evaluation Criteria

Experiment with literature [11] algorithm, literature [12] algorithm, literature [13] algorithm, literature [14] algorithm, literature [15] algorithm, and the proposed algorithm to validate the application effect of different algorithms.1
The motion trajectory tracking results and the similarity between the motion trajectory tracking results of different algorithms and the real trajectory are used as experimental criteria to verify the tracking effects of different algorithms, where the similarity is quantified and calculated by the equation.(13)η=1r−r′s−s′t−t′,where r,s,t are the point coordinates of the original trace and r′,s′,t′ are the point coordinates of the tracking trace.(2)
The dynamic human motion recognition accuracy is used as another evaluation criteria, and the higher the value, the more the accuracy of the recognition results, which is calculated as follows:(14)ω=ItI,whereIt refers to the number of accurate recognition and I refers to the total number of recognition. After calculation, the recognition accuracy of the two algorithms is obtained.(3)
In the overall recognition process, in order to verify the tracking and recognition of different algorithms, the process indicators under different tracking and recognition methods are selected for statistics and comparison. The calculation equation of frame loss rate is as follows:(15)FLR=Nsr−NarNtf,whereNsr refers to the number of image frames that should be received during recognition, Nar refers to the number of image frames received in actual recognition, and Ntf refers to the total image frames received.(4)
Calculate the time cost of different algorithms. The lower the time cost, the higher the calculation efficiency.(5)
F-measure is the weighted average of recall and precision. To verify the performance of the proposed algorithm, different algorithms are selected for analysis, and the equation is calculated as follows:(16)F−measure=Rec⋅AccuRec+Accu,whereRec represents the recall rate of human motion gesture recognition. Accu represents the recognition accuracy of human motion gesture.(6)
The computational performance of the proposed algorithm is compared with different literature algorithms using power consumption as an indicator.


## 3.1. Reconstruction of Multimodal 3D Motion Model of Dynamic Human Motion

In the tracking and recognition of human motion gesture, we must first rely on the camera to collect the moving image of humans, carry out modeling and analysis in the background of tracking and recognition, and search for moving targets. Then, the camera gesture in the shooting process is determined, and the image is repaired according to the obtained moving image. Camera gesture refers to the motion of the camera with the dynamic human motion during shooting, including camera position and transformation. The sparse feature point algorithm is used to obtain the rough gesture and then minimize the distance from point to plane and the difference of pixel values to obtain the accurate gesture [18]. In 3D space, the obtained human motion model is a point cloud state. In order to realize human motion tracking and recognition, it is also necessary to reconstruct the point cloud and complete local optimization. According to the time sequence of the point cloud image, the point cloud is divided into active and inactive parts. The points reconstructed earlier are inactive points, but these points belong to more accurate points after optimization [19, 20]. The newly reconstructed points are active points and also belong to the points to be optimized. According to the position of the current frame, the point cloud is reconstructed by backprojection to obtain the depth image, including the depth image corresponding to active and inactive points. The two parts of point data are constrained and optimized to obtain a new gesture. Local optimization can keep the 3D reconstruction model results of human motion with high accuracy.After the local optimization is completed, global optimization is also needed. In this process, a keyframe database needs to be established to provide data for global optimization and closed-loop tracking and recognition. When there is enough parallax between the image frame and the previous keyframe and the matching points are less than a certain number, the current frame is added to the keyframe database as a keyframe. Global optimization uses all current keyframes, corresponding point cloud data, and camera gesture to construct an optimization problem to optimize camera gesture. Closed-loop detection of tracking and recognition is a judgment mechanism to detect whether the human motion has made previous motion. For the current frame, if the similarity with a keyframe in the keyframe database exceeds a certain value, it is determined that the closed loop is generated so as to keep the same keyframe at the same position successively.Point cloud refers to the collection of 3D points obtained from 3D reconstruction converted to the same coordinate system. The corresponding 3D point coordinates are calculated by using the obtained point cloud image. The transformation matrix coordinate system is transformed according to the previously determined camera gesture and fused with the original point according to the weight. Each 3D point contains not only location information but also semantic information. On this basis, the category probability needs to be saved and updated according to the Bayesian strategy. The original probability of human motion constructed by the current point cloud can be expressed as(1)Pli|I1,⋯,k−1,where li represents the category of human motion, Ii denotes the exact action associated with a specified number of frames during the motion, and the corresponding point probability of the current frame can be expressed as(2)POu=li|Ik,where Ou refers to the number of frames and Ik refers to the corresponding specific motion of a specific number of frames during motion. The calculation Equation is as follows (3).(3)Pli|I1,⋯,k=1ZPli|I1,⋯,k−1POu=li|Ik,where Z is a normalized constant. In this paper, the multimodal human 3D motion model is reconstructed by obtaining the 3D point cloud and fitting the plane in the 3D space, then reprojecting and filling the cavity area, and repairing the depth image.


## 3.2. Tracking Object of Determined

In order to change the new image frame into a keyframe, it is necessary to perform a global optimization operation to determine the tracking target. The camera gesture, 3D point coordinates, and their associated data of all the current keyframes are constructed into a target tracking optimization problem. It is shown in Figure1.Figure 1
Relationship between human motion trajectory, road signs, and gesture.According to Figure1. In the process of human motion gesture, a series of gestures will be generated and then connected through some observations to form the human motion trajectory. And what has been observed through the trajectory is the 3D spatial points that can be expressed by x1, x2, x3, and x4. First, the objects z1 and z2 in the surrounding environment are measured; then, the distance between the dynamic human motion and the marker is calculated to achieve targeting localization, and finally, the human localization of motion, object localization, and the 3D spatial information e2 are accurately calculated. At the moment k, from the estimated camera gesture zk, the results are shown in (4).(4)zk=hxk,where xk refers to the gesture of the current camera and h is the observation function.Supposezk∧ is the camera equipment observation of the current gesture. Due to the existence of error, the two observations may be inconsistent, so the error of this part needs to be calculated.(5)e=zk∧−zk.In the 3D modeling of wireless propagation without spatial segmentation acceleration, the original ray tracing algorithm is used to track and simulate the propagation process. According to the relationship between gesture and road signs, the human target tracking function is constructed, as shown in (6):(6)minx∑k=1nexk,zkTΩexk,zk,where Ω is the weight matrix, T is the error coefficient, and k=1,...,n refers to the number of points in the 3D space.The target tracking optimization function is constructed by using the camera gesture and other parameters of the keyframe so as to achieve the purpose of accurate tracking of human motion gesture. The function is actually a least square problem. Therefore, equation (6) needs to be expanded by the first-order Taylor equation and solved by the Gaussian Newton algorithm to obtain the final result, that is, the moving target tracking result.


## 3.3. Algorithm of Dynamic Human Motion Recognition

After the reconstruction of the multimodal human 3D motion model, the spatiotemporal representation of human motion multimodal data can be obtained. Therefore, it is necessary to use this result as the research basis to realize multimodal deep learning by using CNN in the process of human motion gesture recognition, which can reduce the computational cost to a certain extent [21]. Before convolution, the obtained moving image should be scaled. The scaling equation is(7)M′=floor255∗M−vminvmax−vmin,where M′ refers to the normalized matrix, M refers to the image matrix after preprocessing, vmin refers to the minimum value of pixel matrix in the image, vmax refers to the maximum value of the pixel matrix in the image, and floor. refers to the fuzzy function. After the linear transformation processing of equation (7), multiple captured human motion images can be scaled into gray images; that is, the gray value can be reduced from 0 to 255. The processed image is normalized into the input format of CNN and input into CNN [15, 16]. After convolution operation, the output error can be minimized in the process of image processing and in the process of learning. It is shown in Figure 2.Figure 2
Convolution process.With the characteristic map as the input, after convolution calculation, conduct 3 × 3 transformation of the input image to obtain the transformed block and the feature map. It can be seen that, after the convolution calculation process, the output depth of the obtained characteristic map increases. After the output of the feature image, it is also necessary to maximize the correlation between local data points [17]. In the CNN, the ultimate goal is to realize human motion gesture tracking and recognition [18]. Therefore, in the process of deep learning, it is necessary to design multimodal training samples:(8)xi,yii=1N,where xi and yi mean the different training sample sequences. When the value of yi is smaller than 1, the training sample refers to the modal C1, and when the value of yi is larger than 1, the training sample refers to the modal C2. In the process of classification, it is necessary to use the decision hyperplane equation:(9)gx=wTx+b,where x refers to the column vector, w refers to the decision vector of the hyperplane, and b refers to the decision bias of the hyperplane. The hyperplane can classify two categories of motion modes.(10)wTx+b=0.Then, the defined function interval can be written as(11)γi=yiw⋅xi+b.The corresponding geometric interval is as follows:(12)χi=1w⋅yiw⋅xi+b.In the actual convolution neural network, the above parameters are calculated, and the full connection layer is trained. Setting appropriate ratio parameters can reduce the coadaptation of neurons in the convolution neural network and ensure the training effect while preventing overfitting [19, 20]. The trained CNN is used to recognize human motion so as to achieve the relevant research objectives, as shown in Figure 3.Figure 3
The proposed algorithm process.


## 3.4. Experimental Environment and Data Set

In the process of tracking and recognition of dynamic human motion, the human motion data set is used as the basis. Therefore, this paper mainly relies on the smartwatch in the process of data acquisition. The relevant hardware equipment is needed to complete the tracking and recognition calculation, and the configuration of the relevant experimental equipment and parameters are shown in Table1.Table 1
Experimental environment parameters.
TypeModelParameterIntelligent watchTicWatch 1Built-in inertial sensor, 1.2 GHz Quad coreCameraTQ200240 GB SATA 3SensorMPU605050 × 22 mmHard diskSEAGATE3 TB, 64 M SATA3In the experiment process, multimodal deep learning needs a certain data set as support. This paper selects the public WISDM data set of wireless sensor data mining laboratory and the acceleration UCIHAR data set collected by smartwatch. For the WISDM data set, it includes different human motion gestures made by 30 volunteers, including walking, jogging, sitting, standing, going upstairs, and going downstairs. The behavior distribution of the above volunteers is shown in Figure4.Figure 4
Data of WISDM data set.The data set mainly collected volunteers’ forward and horizontal leg motion and body motion under different motions. Based on the WISDM data set, the UCIHAR data set collects the linear acceleration data of the leg forward, and horizontal motion decomposes the linear acceleration according to the angular velocity collected by the three-axis gyroscope sensor and obtains two types of motion: gravity and body activity. The data in the UCIHAR data set is collected by AirText equipped with smartwatch. Volunteers wear smartwatches in turn and then command volunteers to complete specified motions such as walking and standing. The sampling frequency can collect 50 data per second. The evaluation data set is separated into two parts: training and testing. Eighty percent of the data is utilized for training, while twenty percent is used for testing.


## 3.5. Evaluation Criteria

Experiment with literature [11] algorithm, literature [12] algorithm, literature [13] algorithm, literature [14] algorithm, literature [15] algorithm, and the proposed algorithm to validate the application effect of different algorithms.1
The motion trajectory tracking results and the similarity between the motion trajectory tracking results of different algorithms and the real trajectory are used as experimental criteria to verify the tracking effects of different algorithms, where the similarity is quantified and calculated by the equation.(13)η=1r−r′s−s′t−t′,where r,s,t are the point coordinates of the original trace and r′,s′,t′ are the point coordinates of the tracking trace.(2)
The dynamic human motion recognition accuracy is used as another evaluation criteria, and the higher the value, the more the accuracy of the recognition results, which is calculated as follows:(14)ω=ItI,whereIt refers to the number of accurate recognition and I refers to the total number of recognition. After calculation, the recognition accuracy of the two algorithms is obtained.(3)
In the overall recognition process, in order to verify the tracking and recognition of different algorithms, the process indicators under different tracking and recognition methods are selected for statistics and comparison. The calculation equation of frame loss rate is as follows:(15)FLR=Nsr−NarNtf,whereNsr refers to the number of image frames that should be received during recognition, Nar refers to the number of image frames received in actual recognition, and Ntf refers to the total image frames received.(4)
Calculate the time cost of different algorithms. The lower the time cost, the higher the calculation efficiency.(5)
F-measure is the weighted average of recall and precision. To verify the performance of the proposed algorithm, different algorithms are selected for analysis, and the equation is calculated as follows:(16)F−measure=Rec⋅AccuRec+Accu,whereRec represents the recall rate of human motion gesture recognition. Accu represents the recognition accuracy of human motion gesture.(6)
The computational performance of the proposed algorithm is compared with different literature algorithms using power consumption as an indicator.


## 4. Results and Discussion

### 4.1. Dynamic Human Motion Tracking Effects Experiment

In the above experimental environment, the dynamic human motion tracking effects of the proposed algorithm and other literature algorithms are compared under different trajectory tests, respectively. The tracking results obtained are shown in Figure5.Figure 5
Comparison of motion trajectory tracking results.According to Figure5, the proposed algorithm and the other comparison algorithms are compared in different motion trajectories, and the results show that the motion trajectory tracking results of the proposed algorithm have a high overlap with the real trajectory, and it has superior performance in all four trajectories. In trajectory one, the overlap between the algorithm of literature [11], the algorithm of literature [12], the algorithm of literature [13], the algorithm of literature [14], and the algorithm of literature [15] and the actual path trajectory is low. In trajectory two, the literature [12] has a relatively high degree of overlap with the actual path trajectory but shows a large offset in the edge portion, while the rest of the remaining literature shows a much larger deviation. The distribution of trajectory three is irregular, and it is obvious that the proposed algorithm basically overlaps with the actual path trajectory, while the other literature algorithms all show large deviations. In trajectory four, the overlap between the literature [12] and the actual path trajectory is high. However, there is still a small deviation compared to the proposed algorithm. The comprehensive analysis above can verify the effectiveness of motion trajectory tracking of the proposed algorithm.After calculation, the results of motion trajectory tracking of different algorithms are compared with the real trajectory similarity, as shown in Table2.Table 2
Comparison of similarity results.
Dynamic human motionLiterature [11] algorithmLiterature [12] algorithmLiterature [13] algorithmLiterature [14] algorithmLiterature [15] algorithmThe proposed algorithmWalking56.385.545.546.353.394.7Jogging53.884.142.845.854.195.3Sitting56.983.241.348.552.394.7Standing58.482.023.049.253.496.1Going upstairs59.281.537.441.057.695.2Going downstairs52.383.538.345.356.694.7Average value56.283.338.146.054.695.1According to Table2, the average similarity between the motion trajectory tracking results of the algorithm in literature [11] and the real trajectory is 56.2%, and the average similarity between the motion trajectory tracking results of the algorithm in literature [12] and the real trajectory is 83.3%. The average similarity between the motion trajectory tracking results of the algorithm in the literature [13] and the real trajectory is 38.1%, which is the lowest among the four algorithms. The average similarity between the motion trajectory tracking results of the algorithm in literature [14] and the real trajectory is 46.0%, and the average similarity between the motion trajectory tracking results of the algorithm in literature [15] and the real trajectory is 54.6%. Compared with other algorithms, the average similarity between the motion trajectory tracking results of the proposed algorithm and the real trajectory is 95.1%, which indicates that the proposed algorithm has a better dynamic human motion tracking effect and verifies the effectiveness of the proposed algorithm for multimodal analysis.


### 4.2. Dynamic Human Motion Recognition Accuracy Experiment

The dynamic human motion recognition results of different algorithms are shown in Table3.Table 3
Comparison of dynamic human motion recognition results of different algorithms.
Dynamic human motionLiterature [11] algorithmLiterature [12] algorithmLiterature [13] algorithmLiterature [14] algorithmLiterature [15] algorithmThe proposed algorithmWalking90.382.367.086.673.595.3Jogging81.483.468.085.374.297.1Sitting86.786.474.484.570.195.6Standing91.580.265.786.371.697.2Going upstairs82.082.668.282.575.994.5Going downstairs79.484.470.388.276.896.5Average value85.283.268.985.673.796From the recognition results in Table3, it can be seen that, in the case of multiple motion modes, the average of dynamic human motion recognition accuracy for the algorithm in literature [11] is 85.2%, and the average of dynamic human motion recognition accuracy for the algorithm in literature [12] is 83.2%. The average dynamic human motion recognition accuracy of the algorithm in literature [13] is 68.9%, the average dynamic human motion recognition accuracy of the algorithm in literature [14] is 85.6%, the average dynamic human motion recognition accuracy of the algorithm in literature [15] is 73.7%, and the average dynamic human motion recognition accuracy of the proposed algorithm is 96%, which is the highest accuracy of the six methods, indicating that proposed algorithm can realize accurate recognition of human motion gesture and the actual application effect is better.


### 4.3. Frame Loss Rate Test Results Experiment

The frame loss rate test results of different algorithms are shown in Table4.Table 4
Comparison of frame loss rate test results.
Number of experimentsLiterature [11] algorithmLiterature [12] algorithmLiterature [13] algorithmLiterature [14] algorithmLiterature [15] algorithmThe proposed algorithm1019.622.321.320.521.39.32019.520.425.325.418.68.63018.925.625.028.030.29.34018.528.124.421.422.08.65017.925.020.022.826.47.96018.625.124.826.425.79.1Average value18.824.423.524.124.08.8According to Table4, the average frame loss rate of the proposed algorithm is only 8.8%, which is the lowest rate among the six methods. The average frame loss rate of literature [12], literature [14], and literature [15] algorithms is higher, with the average value above 24%, and the average frame loss rate of literature [13] algorithm is 23.5%. The average frame loss rate of the algorithm in the literature [11] is relatively low. However, it is still 10% higher than that of the proposed algorithm, which shows that using multimodal deep learning to compute human motion gesture data can complete human motion image analysis and then realize motion gesture tracking and recognition.


### 4.4. Time Cost Experiment

The time cost test results of different algorithms are shown in Figure6.Figure 6
Comparison of time cost results.According to Figure6, literature [12] method has the highest time cost, and the time cost of the proposed algorithm is above 3 seconds in several experimental tests. The mean value of the time cost of the algorithm in literature [11] is 3 seconds, and the time cost of the algorithms in literature [13], literature [14], and literature [15] is below 3 seconds. From Figure 6, it is obvious that the time cost of the method in this paper is much lower than that of other literature algorithms, which is always below 1 second and sometimes even below 0.5 seconds, indicating that the time cost of the proposed algorithm is less compared with other algorithms, and the operation efficiency is higher. This is because this paper builds a CNN to analyze the multimodal human motion gesture, which improves the operation efficiency of the algorithm.


### 4.5. F-Measure Test Results Experiment

The F-measure comparison test results of different algorithms are shown in Figure7.Figure 7
Comparison of F-measure of different algorithms.Analysis of the F-measure of different algorithms in Figure7 shows that the curves of the algorithms of literature [11], literature [12], literature [13], literature [14], and literature [15] are relatively smooth with no significant growth trend during the first 7 min, and the F-measure of the algorithms of literature [11] and literature [14] is relatively high at around 0.7. With the extension of time, the F-measure of five literature algorithms showed a certain magnitude of increase, the algorithms of literature [12], literature [13], and literature [15] increased more, the F-measure reached about 0.92 at the time of 10 min, and the F-measure of the proposed algorithm was about 0.96 at this time, which was higher than that of the algorithms of literature [12], literature [13], and literature [15]. It can be seen from the curve in Figure 7 that the F-measure of the proposed algorithm is always higher than that of other algorithms in the literature, which shows the superiority of the proposed algorithm, and good results are obtained by tracking and recognizing the human running gesture using the trained CNN.


## 4.1. Dynamic Human Motion Tracking Effects Experiment

In the above experimental environment, the dynamic human motion tracking effects of the proposed algorithm and other literature algorithms are compared under different trajectory tests, respectively. The tracking results obtained are shown in Figure5.Figure 5
Comparison of motion trajectory tracking results.According to Figure5, the proposed algorithm and the other comparison algorithms are compared in different motion trajectories, and the results show that the motion trajectory tracking results of the proposed algorithm have a high overlap with the real trajectory, and it has superior performance in all four trajectories. In trajectory one, the overlap between the algorithm of literature [11], the algorithm of literature [12], the algorithm of literature [13], the algorithm of literature [14], and the algorithm of literature [15] and the actual path trajectory is low. In trajectory two, the literature [12] has a relatively high degree of overlap with the actual path trajectory but shows a large offset in the edge portion, while the rest of the remaining literature shows a much larger deviation. The distribution of trajectory three is irregular, and it is obvious that the proposed algorithm basically overlaps with the actual path trajectory, while the other literature algorithms all show large deviations. In trajectory four, the overlap between the literature [12] and the actual path trajectory is high. However, there is still a small deviation compared to the proposed algorithm. The comprehensive analysis above can verify the effectiveness of motion trajectory tracking of the proposed algorithm.After calculation, the results of motion trajectory tracking of different algorithms are compared with the real trajectory similarity, as shown in Table2.Table 2
Comparison of similarity results.
Dynamic human motionLiterature [11] algorithmLiterature [12] algorithmLiterature [13] algorithmLiterature [14] algorithmLiterature [15] algorithmThe proposed algorithmWalking56.385.545.546.353.394.7Jogging53.884.142.845.854.195.3Sitting56.983.241.348.552.394.7Standing58.482.023.049.253.496.1Going upstairs59.281.537.441.057.695.2Going downstairs52.383.538.345.356.694.7Average value56.283.338.146.054.695.1According to Table2, the average similarity between the motion trajectory tracking results of the algorithm in literature [11] and the real trajectory is 56.2%, and the average similarity between the motion trajectory tracking results of the algorithm in literature [12] and the real trajectory is 83.3%. The average similarity between the motion trajectory tracking results of the algorithm in the literature [13] and the real trajectory is 38.1%, which is the lowest among the four algorithms. The average similarity between the motion trajectory tracking results of the algorithm in literature [14] and the real trajectory is 46.0%, and the average similarity between the motion trajectory tracking results of the algorithm in literature [15] and the real trajectory is 54.6%. Compared with other algorithms, the average similarity between the motion trajectory tracking results of the proposed algorithm and the real trajectory is 95.1%, which indicates that the proposed algorithm has a better dynamic human motion tracking effect and verifies the effectiveness of the proposed algorithm for multimodal analysis.


## 4.2. Dynamic Human Motion Recognition Accuracy Experiment

The dynamic human motion recognition results of different algorithms are shown in Table3.Table 3
Comparison of dynamic human motion recognition results of different algorithms.
Dynamic human motionLiterature [11] algorithmLiterature [12] algorithmLiterature [13] algorithmLiterature [14] algorithmLiterature [15] algorithmThe proposed algorithmWalking90.382.367.086.673.595.3Jogging81.483.468.085.374.297.1Sitting86.786.474.484.570.195.6Standing91.580.265.786.371.697.2Going upstairs82.082.668.282.575.994.5Going downstairs79.484.470.388.276.896.5Average value85.283.268.985.673.796From the recognition results in Table3, it can be seen that, in the case of multiple motion modes, the average of dynamic human motion recognition accuracy for the algorithm in literature [11] is 85.2%, and the average of dynamic human motion recognition accuracy for the algorithm in literature [12] is 83.2%. The average dynamic human motion recognition accuracy of the algorithm in literature [13] is 68.9%, the average dynamic human motion recognition accuracy of the algorithm in literature [14] is 85.6%, the average dynamic human motion recognition accuracy of the algorithm in literature [15] is 73.7%, and the average dynamic human motion recognition accuracy of the proposed algorithm is 96%, which is the highest accuracy of the six methods, indicating that proposed algorithm can realize accurate recognition of human motion gesture and the actual application effect is better.


## 4.3. Frame Loss Rate Test Results Experiment

The frame loss rate test results of different algorithms are shown in Table4.Table 4
Comparison of frame loss rate test results.
Number of experimentsLiterature [11] algorithmLiterature [12] algorithmLiterature [13] algorithmLiterature [14] algorithmLiterature [15] algorithmThe proposed algorithm1019.622.321.320.521.39.32019.520.425.325.418.68.63018.925.625.028.030.29.34018.528.124.421.422.08.65017.925.020.022.826.47.96018.625.124.826.425.79.1Average value18.824.423.524.124.08.8According to Table4, the average frame loss rate of the proposed algorithm is only 8.8%, which is the lowest rate among the six methods. The average frame loss rate of literature [12], literature [14], and literature [15] algorithms is higher, with the average value above 24%, and the average frame loss rate of literature [13] algorithm is 23.5%. The average frame loss rate of the algorithm in the literature [11] is relatively low. However, it is still 10% higher than that of the proposed algorithm, which shows that using multimodal deep learning to compute human motion gesture data can complete human motion image analysis and then realize motion gesture tracking and recognition.


## 4.4. Time Cost Experiment

The time cost test results of different algorithms are shown in Figure6.Figure 6
Comparison of time cost results.According to Figure6, literature [12] method has the highest time cost, and the time cost of the proposed algorithm is above 3 seconds in several experimental tests. The mean value of the time cost of the algorithm in literature [11] is 3 seconds, and the time cost of the algorithms in literature [13], literature [14], and literature [15] is below 3 seconds. From Figure 6, it is obvious that the time cost of the method in this paper is much lower than that of other literature algorithms, which is always below 1 second and sometimes even below 0.5 seconds, indicating that the time cost of the proposed algorithm is less compared with other algorithms, and the operation efficiency is higher. This is because this paper builds a CNN to analyze the multimodal human motion gesture, which improves the operation efficiency of the algorithm.


## 4.5. F-Measure Test Results Experiment

The F-measure comparison test results of different algorithms are shown in Figure7.Figure 7
Comparison of F-measure of different algorithms.Analysis of the F-measure of different algorithms in Figure7 shows that the curves of the algorithms of literature [11], literature [12], literature [13], literature [14], and literature [15] are relatively smooth with no significant growth trend during the first 7 min, and the F-measure of the algorithms of literature [11] and literature [14] is relatively high at around 0.7. With the extension of time, the F-measure of five literature algorithms showed a certain magnitude of increase, the algorithms of literature [12], literature [13], and literature [15] increased more, the F-measure reached about 0.92 at the time of 10 min, and the F-measure of the proposed algorithm was about 0.96 at this time, which was higher than that of the algorithms of literature [12], literature [13], and literature [15]. It can be seen from the curve in Figure 7 that the F-measure of the proposed algorithm is always higher than that of other algorithms in the literature, which shows the superiority of the proposed algorithm, and good results are obtained by tracking and recognizing the human running gesture using the trained CNN.


## 5. Power Consumption Test Results Experiment

The comparative power consumption test results of different algorithms are shown in Table5.Table 5
Comparison of power consumption by different algorithms.
Number of experimentsLiterature [11] algorithmLiterature [12] algorithmLiterature [13] algorithmLiterature [14] algorithmLiterature [15] algorithmThe proposed algorithm10109.6112.391.380.5101.369.320102.5120.495.385.4118.068.330108.9125.095.188.7110.469.440104.7128.494.481.8112.768.650107.7125.090.482.0126.467.460118.6125.194.586.7125.870.1Average value108.7122.793.584.2115.868.9According to the power consumption comparison test results of different algorithms in Table5, the average power consumption of the proposed algorithm is only 68.9 w, which has obvious advantages and is much lower than that of other literature algorithms. In particular, the average power consumption of literature [11] algorithm is 108.7 w, and the highest is up to 118.6 w. It can be seen that the proposed algorithm first reconstructs the multimodal human 3D motion model and then introduces deep learning to calculate the data related to human motion gesture, which greatly reduces the computing hindrance.


## 6. Conclusions and Future Works

In view of the limitations of human motion gesture tracking and recognition algorithms that are currently in use, this paper proposes a new human motion gesture tracking and recognition algorithm based on multimodal deep learning. The algorithm mainly uses the point cloud data to reconstruct the 3D data model of the human, introduces the CNN for multimodal deep learning, reduces the complexity in the calculation process, and classifies the hyperplane and the trained CNN to complete the tracking and recognition of human motion gesture. The results show that the tracking and recognition algorithm proposed in this paper is better than the current algorithms in tracking accuracy, motion recognition, frame loss rate, and time cost, which verifies the effectiveness of the proposed algorithm. However, the proposed algorithm still has some defects, the modal analysis of human motion gesture is not enough, and the relevant factors affecting the modal features of human running images and the influence weights are not found, such that the occlusion conditions need to be considered. Therefore, there is a need for in-depth discussion and research in future work so as to provide more data support for computer vision research.



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*Source: 4387337-2022-03-11.xml*