Patent Publication Number: US-10776542-B2

Title: Method and device for calibrating physics engine of virtual world simulator to be used for learning of deep learning-based device, and a learning method and learning device for real state network used therefor

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority to U.S. Provisional Patent Application No. 62/798,691, filed on Jan. 30, 2019, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to a virtual world simulator to be used for learning of a deep learning-based device; and more particularly, to the method and the device for calibrating a physics engine of a virtual world simulator to be used for learning of the deep learning-based device by using a real state network capable of modeling a next state in a real world, and a learning method and a learning device for real state network used therefor. 
     BACKGROUND OF THE DISCLOSURE 
     Deep learning-based devices, such as autonomous vehicles, generally determine the next action to be taken by a short-term planning based on information from several frames to dozens of frames of recent images inputted. 
     For example, in the case of the autonomous vehicles, based on segmentation images or meta data like bounding boxes and left/right direction of detected objects, which are information obtained from each frame, actions of three dimensional real-valued vectors, i.e., (i) an amount of change in a steering angle, (ii) a pressure on a brake pedal, (iii) a pressure on an accelerator pedal, are outputted, and accordingly, the autonomous vehicles will autonomously drive themselves in response to the actions. 
     This deep learning-based device should be learned to determine appropriate actions according to the input state, and there are various learning methods, but currently, on-policy reinforcement learning is generally used. 
     Also, the deep learning-based device can be learned in a real world, but it is difficult to acquire diversified training data, and it is time-consuming and costly. 
     Therefore, a method for learning the deep learning-based devices in a virtual world has been proposed. 
     However, when learning in the virtual world, there is a problem in a reliability of the learning results due to a gap between virtual environment and real environment. 
     For example, in case of the deep learning-based device is an autonomous vehicle, the physics engine of a virtual world simulator may be configured to output “a next state with a changed velocity, a location, and surroundings of the vehicle” if “actions of rotating a steering wheel by a certain angle and stepping on the brake pedal with a certain pressure” are taken in response to “a state of a current velocity and its surroundings”, thereby learning the autonomous vehicle. 
     However, the larger a discrepancy between the next state created by the physics engine of the virtual world simulator and the next state of a real world is, the less optimal the optimal action having been learned in the virtual world is in the real world. 
     For example, in the case of the autonomous vehicle, the vehicle has learned a proper action that can avoid an accident in a dangerous situation in the virtual world, but nevertheless an accident in the real world occurs even though the vehicle takes the proper action in a same situation. 
     SUMMARY OF THE DISCLOSURE 
     It is an object of the present disclosure to solve all the aforementioned problems. 
     It is another object of the present disclosure to allow a physics engine of a virtual world simulator to output a next state that minimizes a gap between a virtual world and a real world. 
     It is still another object of the present disclosure to calibrate the physics engine of the virtual world simulator such that the virtual world more closely mimics the real world. 
     In accordance with one aspect of the present disclosure, there is provided a method for calibrating a physics engine of a virtual world simulator to be used for learning of a deep learning-based device, including steps of: (a) if virtual current frame information corresponding to a virtual current state in a virtual environment is acquired from the virtual world simulator, a calibrating device performing (i) a process of transmitting the virtual current frame information to the deep learning-based device, to thereby instruct the deep learning-based device to apply its operation using previous learned parameters to the virtual current frame information, and thus to output virtual action information corresponding to the virtual current frame information, (ii) a process of transmitting the virtual current frame information and the virtual action information to the physics engine of the virtual world simulator, to thereby instruct the physics engine to apply its operation using previous calibrated parameters to the virtual current frame information and the virtual action information, and thus to output virtual next frame information corresponding to the virtual current frame information and the virtual action information, and (iii) a process of transmitting the virtual current frame information and the virtual action information to a real state network which has been learned to output multiple pieces of predicted next frame information in response to real action information on a real action performed in multiple pieces of real recent frame information by the deep learning-based device in a real environment, to thereby instruct the real state network to apply its operation using learned prediction parameters to the virtual action information and multiple pieces of the virtual recent frame information corresponding to the virtual current frame information and thus to output predicted real next frame information; and (b) the calibrating device performing a process of calibrating and optimizing the previous calibrated parameters of the physics engine, such that at least one loss is minimized which is created by referring to the virtual next frame information and the predicted real next frame information, to thereby generate current calibrated parameters as optimized parameters. 
     As one example, the method further comprises a step of: (c) the calibrating device performing a process of transmitting the virtual next frame information and reward information corresponding to the virtual action information to the deep learning-based device, to thereby instruct the deep learning-based device to update the previous learned parameters via on-policy reinforcement learning which uses the virtual next frame information and the reward information. 
     As one example, in the process of (iii) at the step of (a), the calibrating device performs a process of transmitting the virtual current frame information and the virtual action information to the real state network, to thereby instruct the real state network to generate the multiple pieces of the virtual recent frame information by referring to the virtual current frame information and k pieces of virtual previous frame information received beforehand. 
     As one example, at the process of (iii), the calibrating device performs a process of transmitting the virtual current frame information and the virtual action information to the real state network, to thereby instruct the real state network to (iii-1) (iii-1-1) generate a 1-st dimension vector by applying convolution operation to a virtual current frame state sum created by concatenating the virtual current frame information and the k pieces of the virtual previous frame information and (iii-1-2) generate a 2-nd dimension vector by applying fully-connected operation to the virtual action information, and (iii-2) generate the predicted real next frame information by applying deconvolution operation to a concatenation of the 1-st dimension vector and the 2-nd dimension vector. 
     As one example, the virtual current frame state sum is an H×W×(K+1) tensor created by concatenating (i) the k pieces of the virtual previous frame information and (ii) the virtual current frame information which is an H×W×C tensor, wherein the 1-st dimension vector is an HWC-dimension vector, and wherein, supposing that the 2-nd dimension vector is an L-dimension vector, the predicted real next frame information is an H×W×C tensor created by applying deconvolution operation to a 1×1×(HWC+L) tensor generated by concatenating the 1-st dimension vector and the 2-nd dimension vector. 
     As one example, at the step of (b), the calibrating device repeats, until the loss decreases, (i) a process of selecting one previous calibrated parameter among the previous calibrated parameters (ii) a process of calibrating the selected one previous calibrated parameter with a preset learning rate by using the loss, to thereby generate one current calibrated parameter as an optimized parameter, and (iii) (iii-1) a process of instructing the physics engine to apply its operation using said one current calibrated parameter and a rest of the previous calibrated parameters excluding said one previous calibrated parameter to the virtual current frame information and the virtual action information, to thereby generate new virtual next frame information and (iii-2) a process of determining whether the loss decreases by using at least one new loss created by referring to the new virtual next frame information and the predicted real next frame information. 
     As one example, if the loss is determined as not decreased for any of the previous calibrated parameters, the calibrating device decreases the preset learning rate and performs said process (i), said process (ii), and said process (iii). 
     In accordance with another aspect of the present disclosure, there is provided a method for learning a real state network capable of generating predicted next frame information corresponding to real action information on a real action performed in multiple pieces of real recent frame information by a deep learning-based device in a real environment, including steps of: (a) if multiple pieces of trajectory information corresponding to multiple pieces of the real action information on the real action performed by the deep learning-based device in the real environment are acquired as training data, a learning device performing a process of generating multiple pieces of recent frame information for training by referring to k pieces of previous real frame information and real current frame information at a point of time in specific trajectory information; (b) the learning device performing a process of inputting into the real state network the multiple pieces of the recent frame information for training and action information for training which is acquired by referring to real current action information of the specific trajectory information at the point of the time, to thereby allow the real state network to apply its operation using prediction parameters to the multiple pieces of the recent frame information for training and the action information for training and thus to output the predicted next frame information; and (c) the learning device performing a process of updating the prediction parameters such that the loss is minimized, by using at least one loss created by referring to the predicted next frame information and real next frame information which is next to the real current frame information in the specific trajectory information. 
     As one example, at the step of (b), the learning device performs (i) a process of inputting a current frame state sum for training created by concatenating the multiple pieces of the recent frame information for training into a convolutional neural network of the real state network, to thereby allow the convolutional neural network to output a 1-st feature by applying convolution operation to the current frame state sum for training and a process of inputting the action information for training into at least one fully connected layer of the real state network, to thereby allow said at least one fully connected layer to output a 2-nd feature by applying fully-connected operation to the action information for training and (ii) a process of inputting a concatenated feature created by concatenating the 1-st feature and the 2-nd feature into a deconvolutional layer, to thereby allow the deconvolutional layer to output the predicted next frame information by applying deconvolution operation to the concatenated feature. 
     As one example, the learning device performs a process of instructing the convolutional neural network to output the current frame state sum for training, which is an H×W×(K+1) tensor created by concatenating the multiple pieces of the recent frame information for training which are H×W×C tensors, as the 1-st feature which is an HWC-dimension vector, a process of instructing said at least one fully connected layer to output the action information for training, which is a 3-dimension vector, as the 2-nd feature which is an L-dimension vector, and a process of instructing the deconvolutional layer to output a 1×1×(HWC+L) tensor, created by concatenating the 1-st feature and the 2-nd feature, as the predicted next frame information which is an H×W×C tensor. 
     As one example, the learning device performs a process of updating at least one parameter of at least one of the convolutional neural network, said at least one fully connected layer, and the deconvolutional layer according to a gradient descent using the loss. 
     In accordance with still another aspect of the present disclosure, there is provided a calibrating device for calibrating a physics engine of a virtual world simulator to be used for learning of a deep learning-based device, including: at least one memory that stores instructions; and at least one processor configured to execute the instructions to perform or support another device to perform: (I) if virtual current frame information corresponding to a virtual current state in a virtual environment is acquired from the virtual world simulator, (i) a process of transmitting the virtual current frame information to the deep learning-based device, to thereby instruct the deep learning-based device to apply its operation using previous learned parameters to the virtual current frame information, and thus to output virtual action information corresponding to the virtual current frame information, (ii) a process of transmitting the virtual current frame information and the virtual action information to the physics engine of the virtual world simulator, to thereby instruct the physics engine to apply its operation using previous calibrated parameters to the virtual current frame information and the virtual action information, and thus to output virtual next frame information corresponding to the virtual current frame information and the virtual action information, and (iii) a process of transmitting the virtual current frame information and the virtual action information to a real state network which has been learned to output multiple pieces of predicted next frame information in response to real action information on a real action performed in multiple pieces of real recent frame information by the deep learning-based device in a real environment, to thereby instruct the real state network to apply its operation using learned prediction parameters to the virtual action information and multiple pieces of the virtual recent frame information corresponding to the virtual current frame information and thus to output predicted real next frame information, and (II) a process of calibrating and optimizing the previous calibrated parameters of the physics engine, such that at least one loss is minimized which is created by referring to the virtual next frame information and the predicted real next frame information, to thereby generate current calibrated parameters as optimized parameters. 
     As one example, the processor further performs: (III) a process of transmitting the virtual next frame information and reward information corresponding to the virtual action information to the deep learning-based device, to thereby instruct the deep learning-based device to update the previous learned parameters via on-policy reinforcement learning which uses the virtual next frame information and the reward information. 
     As one example, in the process of (iii), the processor performs a process of transmitting the virtual current frame information and the virtual action information to the real state network, to thereby instruct the real state network to generate the multiple pieces of the virtual recent frame information by referring to the virtual current frame information and k pieces of virtual previous frame information received beforehand. 
     As one example, at the process of (iii), the processor performs a process of transmitting the virtual current frame information and the virtual action information to the real state network, to thereby instruct the real state network to (iii-1) (iii-1-1) generate a 1-st dimension vector by applying convolution operation to a virtual current frame state sum created by concatenating the virtual current frame information and the k pieces of the virtual previous frame information and (iii-1-2) generate a 2-nd dimension vector by applying fully-connected operation to the virtual action information, and (iii-2) generate the predicted real next frame information by applying deconvolution operation to a concatenation of the 1-st dimension vector and the 2-nd dimension vector. 
     As one example, the virtual current frame state sum is an H×W×(K+1) tensor created by concatenating (i) the k pieces of the virtual previous frame information and (ii) the virtual current frame information which is an H×W×C tensor, wherein the 1-st dimension vector is an HWC-dimension vector, and wherein, supposing that the 2-nd dimension vector is an L-dimension vector, the predicted real next frame information is an H×W×C tensor created by applying deconvolution operation to a 1×1×(HWC+L) tensor generated by concatenating the 1-st dimension vector and the 2-nd dimension vector. 
     As one example, at the process of (II), the processor repeats, until the loss decreases, (II-1) a process of selecting one previous calibrated parameter among the previous calibrated parameters (II-2) a process of calibrating the selected one previous calibrated parameter with a preset learning rate by using the loss, to thereby generate one current calibrated parameter as an optimized parameter, and (II-3) (II-3a) a process of instructing the physics engine to apply its operation using said one current calibrated parameter and a rest of the previous calibrated parameters excluding said one previous calibrated parameter to the virtual current frame information and the virtual action information, to thereby generate new virtual next frame information and (II-3b) a process of determining whether the loss decreases by using at least one new loss created by referring to the new virtual next frame information and the predicted real next frame information. 
     As one example, if the loss is determined as not decreased for any of the previous calibrated parameters, the processor decreases the preset learning rate and performs said process (II-1), said process (II-2), and said process (II-3). 
     In accordance with still yet another aspect of the present disclosure, there is provided a learning device for learning a real state network capable of generating predicted next frame information corresponding to real action information on a real action performed in multiple pieces of real recent frame information by a deep learning-based device in a real environment, including: at least one memory that stores instructions; and at least one processor configured to execute the instructions to perform or support another device to perform: (I) if multiple pieces of trajectory information corresponding to multiple pieces of the real action information on the real action performed by the deep learning-based device in the real environment are acquired as training data, a process of generating multiple pieces of recent frame information for training by referring to k pieces of previous real frame information and real current frame information at a point of time in specific trajectory information, (II) a process of inputting into the real state network the multiple pieces of the recent frame information for training and action information for training which is acquired by referring to real current action information of the specific trajectory information at the point of the time, to thereby allow the real state network to apply its operation using prediction parameters to the multiple pieces of the recent frame information for training and the action information for training and thus to output the predicted next frame information, and (III) a process of updating the prediction parameters such that the loss is minimized, by using at least one loss created by referring to the predicted next frame information and real next frame information which is next to the real current frame information in the specific trajectory information. 
     As one example, at the process of (II), the processor performs (i) a process of inputting a current frame state sum for training created by concatenating the multiple pieces of the recent frame information for training into a convolutional neural network of the real state network, to thereby allow the convolutional neural network to output a 1-st feature by applying convolution operation to the current frame state sum for training and a process of inputting the action information for training into at least one fully connected layer of the real state network, to thereby allow said at least one fully connected layer to output a 2-nd feature by applying fully-connected operation to the action information for training and (ii) a process of inputting a concatenated feature created by concatenating the 1-st feature and the 2-nd feature into a deconvolutional layer, to thereby allow the deconvolutional layer to output the predicted next frame information by applying deconvolution operation to the concatenated feature. 
     As one example, the processor performs a process of instructing the convolutional neural network to output the current frame state sum for training, which is an H×W×(K+1) tensor created by concatenating the multiple pieces of the recent frame information for training which are H×W×C tensors, as the 1-st feature which is an HWC-dimension vector, a process of instructing said at least one fully connected layer to output the action information for training, which is a 3-dimension vector, as the 2-nd feature which is an L-dimension vector, and a process of instructing the deconvolutional layer to output a 1×1×(HWC+L) tensor, created by concatenating the 1-st feature and the 2-nd feature, as the predicted next frame information which is an H×W×C tensor. 
     As one example, the processor performs a process of updating at least one parameter of at least one of the convolutional neural network, said at least one fully connected layer, and the deconvolutional layer according to a gradient descent using the loss. 
     In addition, recordable media readable by a computer for storing a computer program to execute the method of the present disclosure is further provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and features of the present disclosure will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which: 
       The following drawings to be used to explain example embodiments of the present disclosure are only part of example embodiments of the present disclosure and other drawings can be obtained based on the drawings by those skilled in the art of the present disclosure without inventive work. 
         FIG. 1  is a drawing schematically illustrating a calibrating device for calibrating a physics engine of a virtual world simulator to be used for learning of a deep learning-based device in accordance with one example embodiment of the present disclosure. 
         FIG. 2  is a drawing schematically illustrating a method for calibrating the physics engine of the virtual world simulator to be used for learning of the deep learning-based device in accordance with one example embodiment of the present disclosure. 
         FIG. 3  is a drawing schematically illustrating a learning device for learning a real state network capable of generating predicted next frame information corresponding to real action information on a real action performed in multiple pieces of real recent frame information by the deep learning-based device in a real environment in accordance with one example embodiment of the present disclosure. 
         FIG. 4  is a drawing schematically illustrating a learning method for learning the real state network capable of generating the predicted next frame information corresponding to the real action information on the real action performed in the multiple pieces of the real recent frame information by the deep learning-based device in the real environment in accordance with one example embodiment of the present disclosure. 
         FIG. 5  is a drawing schematically illustrating a method for generating at least one trajectory for learning the real state network in accordance with one example embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Detailed explanation on the present disclosure to be made below refer to attached drawings and diagrams illustrated as specific embodiment examples under which the present disclosure may be implemented to make clear of purposes, technical solutions, and advantages of the present disclosure. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. 
     Besides, in the detailed description and claims of the present disclosure, a term “include” and its variations are not intended to exclude other technical features, additions, components or steps. Other objects, benefits and features of the present disclosure will be revealed to one skilled in the art, partially from the specification and partially from the implementation of the present disclosure. The following examples and drawings will be provided as examples but they are not intended to limit the present disclosure. 
     Moreover, the present disclosure covers all possible combinations of example embodiments indicated in this specification. It is to be understood that the various embodiments of the present disclosure, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein in connection with one embodiment may be implemented within other embodiments without departing from the spirit and scope of the present disclosure. In addition, it is to be understood that the position or arrangement of individual elements within each disclosed embodiment may be modified without departing from the spirit and scope of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled. In the drawings, like numerals refer to the same or similar functionality throughout the several views. 
     Any images referred to in the present disclosure may include images related to any roads paved or unpaved, in which case the objects on the roads or near the roads may include vehicles, persons, animals, plants, buildings, flying objects like planes or drones, or any other obstacles which may appear in a road-related scene, but the scope of the present disclosure is not limited thereto. As another example, said any images referred to in the present disclosure may include images not related to any roads, such as images related to alleyway, land lots, sea, lakes, rivers, mountains, forests, deserts, sky, or any indoor space, in which case the objects in said any images may include vehicles, persons, animals, plants, buildings, flying objects like planes or drones, ships, amphibious planes or ships, or any other obstacles which may appear in a scene related to alleyway, land lots, sea, lakes, rivers, mountains, forests, deserts, sky, or any indoor space, but the scope of the present disclosure is not limited thereto. 
     To allow those skilled in the art to carry out the present disclosure easily, the example embodiments of the present disclosure by referring to attached diagrams will be explained in detail as shown below. 
       FIG. 1  is a drawing schematically illustrating a calibrating device for calibrating a physics engine of a virtual world simulator for learning a deep learning-based device in accordance with one example embodiment of the present disclosure. By referring to  FIG. 1 , the calibrating device  1000  may include a memory  1100  for storing instructions to calibrate the physics engine of the virtual world simulator for learning of the deep learning-based device and a processor  1200  for performing processes corresponding to the instructions in the memory  1100  to calibrate the physics engine of the virtual world simulator for learning of the deep learning-based device. 
     Specifically, the calibrating device  1000  may typically achieve a desired system performance by using combinations of at least one computing device and at least one computer software, e.g., a computer processor, a memory, a storage, an input device, an output device, or any other conventional computing components, an electronic communication device such as a router or a switch, an electronic information storage system such as a network-attached storage (NAS) device and a storage area network (SAN) as the computing device and any instructions that allow the computing device to function in a specific way as the computer software. 
     The processor of the computing device may include hardware configuration of MPU (Micro Processing Unit) or CPU (Central Processing Unit), cache memory, data bus, etc. Additionally, the computing device may further include OS and software configuration of applications that achieve specific purposes. 
     However, such description of the computing device does not exclude an integrated device including any combination of a processor, a memory, a medium, or any other computing components for implementing the present disclosure. 
     A method for calibrating the physics engine of the virtual world simulator for learning of the deep learning-based device by using the calibrating device  1000  in accordance with one example embodiment of the present disclosure is described by referring to  FIG. 2  as follows. 
     First, the virtual world simulator  100  may generate virtual current frame information I t  corresponding to a virtual current state in a virtual environment predetermined for learning of the deep learning-based device  300 , i.e., an agent. Herein, the virtual current state may include operating state information, surrounding environment information, operating conditions, etc. of the deep learning-based device  300 , and the deep learning-based device  300  may include any device capable of operating according to conditions learned by deep learning algorithm, such as autonomous vehicles, autonomous airplanes, robots, etc. For example, if the deep learning-based device is an autonomous vehicle, the virtual current state may include various driving information such as autonomous vehicle information, surrounding vehicle information, road information, traffic signal information, the surrounding environment information, etc. 
     Next, if the virtual current frame information I t  corresponding to the virtual current state in the virtual environment is acquired from the virtual world simulator  100 , the calibrating device  1000  may transmit the acquired virtual current frame information I t  to the deep learning-based device  300 , to thereby allow the deep learning-based device  300  to apply its operation using previous learned parameters to the virtual current frame information I t  and thus to output virtual action information a t  corresponding to the virtual current frame information I t  at a step of S 2 . 
     Also, the calibrating device  1000  may transmit the virtual current frame information I t  acquired from the virtual world simulator  100  and the virtual action information a t  outputted from the deep learning-based device  300  to the physics engine F  110  of the virtual world simulator  100 , to thereby allow the physics engine F  110  to apply its operation using previous calibrated parameters to the virtual current frame information I t  and the virtual action information a t  and thus to output virtual next frame information I t+1  corresponding to the virtual action information a t  and the virtual current frame information I t  at a step of S 3 . 
     In addition to this, the calibrating device  1000  may transmit the virtual current frame information I t  acquired from the virtual world simulator  100  and the virtual action information a t  outputted from the deep learning-based device  300  to the real state network  200 , to thereby allow the real state network  200  to apply its operation using learned prediction parameters to the virtual action information a t  and multiple pieces of virtual recent frame information corresponding to the virtual current frame information I t  and thus to output predicted real next frame information Î t+1  at a step of S 5 . That is, the real state network  200  may output next frame information predicted to happen in the real world by referring to the multiple pieces of the virtual recent frame information and the virtual action information. Throughout the present disclosure, the multiple pieces of the virtual recent frame information may be k+1 pieces of the virtual recent frame information, but the scope of the present disclosure is not limited thereto. 
     Herein, the real state network  200  may have been learned to output the multiple pieces of the predicted next frame information corresponding to the real action information on the real action in the multiple pieces of the real recent frame information performed by the deep learning-based device in the real environment, a process of which will be described in detail later. Throughout the present disclosure, the multiple pieces of the predicted next frame information may be k+1 pieces of the predicted next frame information, and the multiple pieces of the real recent frame information may be k+1 pieces of the real recent frame information, but the scope of the present disclosure is not limited thereto. 
     And, the calibrating device  100  may perform a process of transmitting the virtual current frame information and the virtual action information to the real state network  200 , to thereby instruct the real state network  200  to generate the multiple pieces of the virtual recent frame information by referring to the virtual current frame information and k pieces of virtual previous frame information received beforehand. As another example, the calibrating device  1000  may generate the multiple pieces of the virtual recent frame information by referring to the virtual current frame information and the k pieces of the virtual previous frame information received beforehand, to thereby transmit the virtual recent frame information to the real state network  200 . 
     That is, the calibrating device  1000  may perform a process of transmitting the virtual current frame information and the virtual action information to the real state network  200 , to thereby instruct the real state network  200  to generate a virtual current frame state sum created by concatenating the virtual current frame information and the k pieces of the virtual previous frame information. As another example, the calibrating device  1000  may generate the virtual current frame state sum created by concatenating the virtual current frame information and the k pieces of the virtual previous frame information, to thereby transmit the virtual current frame state sum to the real state network  200 . 
     Herein, the virtual current frame state sum s t  may be represented as [I t−K , I t−K+1 , . . . , I t−1 , I t ] and the predicted real next state Î t+1  may be represented as S(s t ,a t ). 
     Meanwhile, the real state network  200  may (i) (i-1) generate a 1-st dimension vector by applying convolution operation to the virtual current frame state sum s t  and (i-2) generate a 2-nd dimension vector by applying fully-connected operation to the virtual action information, and (ii) generate the predicted real next frame information by applying deconvolution operation to a concatenation of the 1-st dimension vector and the 2-nd dimension vector. 
     Herein, the virtual current frame state sum s t  may be an H×W×(K+1) tensor created by concatenating (i) the k pieces of the virtual previous frame information and (ii) the virtual current frame information which is an H×W×C tensor. Further, the 1-st dimension vector may be an HWC-dimension vector, and, supposing that the 2-nd dimension vector is an L-dimension vector, the predicted real next frame information may be an H×W×C tensor created by applying deconvolution operation to a 1×1×(HWC+L) tensor generated by concatenating the 1-st dimension vector and the 2-nd dimension vector. And, the virtual action information may be a 3-dimension vector, for example, if the deep learning-based device  300  is the autonomous vehicle, the virtual action information may correspond to [information on a degree of change in a steering angle, information on a pressure on a brake pedal, information on a pressure on an accelerator pedal]. 
     Next, the calibrating device  1000  may perform a process of calibrating and optimizing the previous calibrated parameters of the physics engine F  110 , such that at least one loss is minimized which is created by referring to the virtual next frame information outputted from the physics engine F  110  of the virtual world simulator  100  and the predicted real next frame information outputted from the real state network  200 , to thereby generate current calibrated parameters as optimized parameters, at a step of S 6 . As a result, the physics engine F  110  may plan a virtual next frame where a gap between the virtual environment and the real environment is minimized. 
     That is, the calibrating device  1000  may calculate one or more losses ∥I t+1 −Î t+1 ∥ F   2  by referring to the virtual next frame information I t+1  generated by the physics engine F  110  and the predicted real next frame information Î t+1  generated by the real state network  200 , or may instruct a loss layer to calculate the losses ∥I t+1 −Î t+1 ∥ F   2 , and may optimize the physics engine F  110  by referring to the losses ∥I t+1 −Î t+1 ∥ F   2 . 
     Meanwhile, if the physics engine F  110  of the virtual world simulator  100  is non-differentiable, the previous calibrated parameters may be optimized as follows. 
     That is, the calibrating device  1000  may perform (i) a process of selecting one previous calibrated parameter among the previous calibrated parameters of the physics engine F  110  and (ii) a process of calibrating the selected one previous calibrated parameter with a preset learning rate by using the loss, to thereby generate one current calibrated parameter as an optimized parameter. And, the calibrating device  1000  may repeat, until the loss decreases, (i) a process of instructing the physics engine F  110  to apply its operation using said one current calibrated parameter and a rest of the previous calibrated parameters excluding said one previous calibrated parameter to the virtual current frame information and the virtual action information, to thereby generate new virtual next frame information and (ii) a process of determining whether the loss decreases by using at least one new loss created by referring to the new virtual next frame information and the predicted real next frame information. 
     And, if the loss is determined as not decreased for any of the previous calibrated parameters, the calibrating device  1000  may decrease the preset learning rate and may perform the processes above. 
     Also, the calibrating device  1000  may perform a process of transmitting the virtual next frame information I t+1  outputted from the physics engine F  110  and reward information r t+1  corresponding to the virtual action information outputted from the deep learning-based device  300  to the deep learning-based device  300  at a step of S 4 , to thereby instruct the deep learning-based device  300  to update the previous learned parameters via on-policy reinforcement learning which uses the virtual next frame information I t+1  and the reward information r t+1 . Herein, the reward information may be result representing whether the virtual action information is appropriate which is performed by the deep learning-based device  300  in response to the virtual current frame information, and the reward information may be generated by the physics engine F  110  or the calibrating device  1000 . 
       FIG. 3  is a drawing schematically illustrating a learning device for learning the real state network capable of generating the predicted next frame information corresponding to the real action information on the real action performed in the multiple pieces of the real recent frame information by the deep learning-based device in the real environment in accordance with one example embodiment of the present disclosure. By referring to  FIG. 3 , the learning device  2000  may include a memory  2100  for storing instructions to learn the real state network capable of outputting the predicted next frame information corresponding to the real action information on the real action performed in the multiple pieces of the real recent frame information by the deep learning-based device in the real environment and a processor  2200  for performing processes corresponding to the instructions in the memory  2100  to learn the real state network capable of outputting the predicted next frame information corresponding to the real action information on the real action performed in the multiple pieces of the real recent frame information by the deep learning-based device in the real environment. 
     Specifically, the learning device  2000  may typically achieve a desired system performance by using combinations of at least one computing device and at least one computer software, e.g., a computer processor, a memory, a storage, an input device, an output device, or any other conventional computing components, an electronic communication device such as a router or a switch, an electronic information storage system such as a network-attached storage (NAS) device and a storage area network (SAN) as the computing device and any instructions that allow the computing device to function in a specific way as the computer software. The processor of the computing device may include hardware configuration of MPU (Micro Processing Unit) or CPU (Central Processing Unit), cache memory, data bus, etc. Additionally, the computing device may further include OS and software configuration of applications that achieve specific purposes. 
     However, such description of the computing device does not exclude an integrated device including any combination of a processor, a memory, a medium, or any other computing components for implementing the present disclosure. 
     A method for learning of outputting the predicted next frame information corresponding to the real action information on the real action performed in the multiple pieces of the real recent frame information by the deep learning-based device in the real environment by using the learning device  2000  in accordance with one example embodiment of the present disclosure configured as such is described as follows by referring to  FIG. 4 . In the description below, the part easily deducible from the explanation of  FIG. 2  will be omitted. 
     First, the learning device  2000  may acquire multiple pieces of trajectory information corresponding to multiple pieces of the real action information on the real action performed by the deep learning-based device in the real environment as training data. 
     Herein, by referring to  FIG. 5 , N pieces of the trajectory information may be generated by the agent, which is the deep learning-based device, in various environments like the real environment, and the deep learning-based device may generate the N pieces of the trajectory information by repeating: (i) a process of creating the current frame I t  which is information on the real environment, (ii) a process of creating the action a t  corresponding to the current frame I t , and (iii) a process of creating the next frame I t+1  changed according to the action a t . The N pieces of the trajectory information may be exemplarily represented as follows. 
     
       
         
           
             
               
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     Herein, each of lengths T 1 , . . . , T N , each of starting points I 1   (1) , . . . , I 1   (N)  of each of the N pieces of the trajectory information and action pattern p(a t |s t ) of the deep learning-based device, e.g., driving patterns of the autonomous vehicle, may be different. 
     And, the learning device  2000  may perform a process of generating multiple pieces of recent frame information for training by referring to k pieces of previous real frame information and real current frame information at a point of time in specific trajectory information among the multiple pieces of the trajectory information acquired as the training data. 
     Next, the learning device  2000  may perform a process of inputting into the real state network  200  the multiple pieces of the recent frame information for training and action information for training which is acquired by referring to real current action information of the specific trajectory information at the point of the time, to thereby allow the real state network  200  to apply its operation using prediction parameters to the multiple pieces of the recent frame information for training and the action information for training and thus to output the predicted next frame information. 
     As one example, the learning device  2000  may perform (i) a process of inputting a current frame state sum for training, created by concatenating the multiple pieces of the recent frame information for training, into a convolutional neural network of the real state network  200 , to thereby allow the convolutional neural network to output a 1-st feature by applying convolution operation to the current frame state sum for training and (ii) a process of inputting the action information for training into at least one fully connected layer of the real state network  200 , to thereby allow said at least one fully connected layer to output a 2-nd feature by applying fully-connected operation to the action information for training. And, the learning device  2000  may perform a process of inputting a concatenated feature created by concatenating the 1-st feature and the 2-nd feature into a deconvolutional layer, to thereby allow the deconvolutional layer to output the predicted next frame information by applying deconvolution operation to the concatenated feature. 
     Herein, the current frame state sum for training s t  may be represented as [I t−K , I t−K+1 , . . . , I t−1 , I t ] and the predicted next frame information Î t+1  may be represented as S(s t ,a t ). 
     That is, the learning device  2000  may perform (i) a process of instructing the convolutional neural network to output the current frame state sum for training, which is an H×W×(K+1) tensor created by concatenating the multiple pieces of the recent frame information for training which are H×W×C tensors, as the 1-st feature which is an HWC-dimension vector, (ii) a process of instructing said at least one fully connected layer to output the action information for training, which is a 3-dimension vector, as the 2-nd feature which is an L-dimension vector, and (iii) a process of instructing the deconvolutional layer to output a 1×1×(HWC+L) tensor, created by concatenating the 1-st feature and the 2-nd feature, as the predicted next frame information which is an H×W×C tensor. 
     Next, the learning device  2000  may perform a process of updating the prediction parameters such that the loss is minimized, by using at least one loss created by referring to the predicted next frame information and real next frame information which is next to the real current frame information in the specific trajectory information. 
     That is, the learning device  2000  may calculate one or more losses ∥I t+1 −Î t+1 ∥ F   2  by referring to the real next frame information I t+1  of the specific trajectory information and the predicted next frame information Î t+1  outputted from the real state network  200 , or may instruct a loss layer to calculate the losses ∥I t+1 −Î t+1 ∥ F   2 , and may learn the real state network  200  by referring to the losses ∥I t+1 −Î t+1 ∥ F   2 . 
     Herein, the learning device  2000  may perform a process of updating the prediction parameters of the real state network  200  according to a gradient descent, for example, may update at least one parameter of at least one of the convolutional neural network, said at least one fully connected layer, and the deconvolutional layer. 
     And, the learning device  2000  may repeat the learning processes above by using N real world trajectories, such that the losses of the real state network  200  converge. 
     The present disclosure has an effect of more reliably applying short-term planning of the deep learning-based device learned in the virtual world to the real world, by calibrating the physics engine of the virtual world simulator to minimize the gap between the virtual world and the real world. 
     The present disclosure has another effect of utilizing losses between the physics engine and a real environment model as a reliability measure, for validating a reliability of a given virtual environment. 
     The embodiments of the present disclosure as explained above can be implemented in a form of executable program command through a variety of computer means recordable to computer readable media. The computer readable media may include solely or in combination, program commands, data files, and data structures. The program commands recorded to the media may be components specially designed for the present invention or may be usable to a skilled human in a field of computer software. Computer readable media include magnetic media such as hard disk, floppy disk, and magnetic tape, optical media such as CD-ROM and DVD, magneto-optical media such as floptical disk and hardware devices such as ROM, RAM, and flash memory specially designed to store and carry out program commands. Program commands include not only a machine language code made by a complier but also a high level code that can be used by an interpreter etc., which is executed by a computer. The aforementioned hardware device can work as more than a software module to perform the action of the present invention and they can do the same in the opposite case. 
     As seen above, the present disclosure has been explained by specific matters such as detailed components, limited embodiments, and drawings. They have been provided only to help more general understanding of the present invention. It, however, will be understood by those skilled in the art that various changes and modification may be made from the description without departing from the spirit and scope of the disclosure as defined in the following claims. 
     Accordingly, the thought of the present disclosure must not be confined to the explained embodiments, and the following patent claims as well as everything including variations equal or equivalent to the patent claims pertain to the category of the thought of the present disclosure.