WO2023113067A1

WO2023113067A1 - Building energy management system

Info

Publication number: WO2023113067A1
Application number: PCT/KR2021/019057
Authority: WO
Inventors: 남주현
Original assignee: 주식회사 엔엑스테크놀로지
Priority date: 2021-12-15
Filing date: 2021-12-15
Publication date: 2023-06-22
Also published as: KR102443443B1

Abstract

A building energy management system of the present invention may comprise: a server including a communication unit which transmits/receives data to/from a plurality of modules, a storage unit which stores data received from the plurality of modules, and a control unit which controls, through the plurality of modules, devices connected to the respective modules; a first module which is connected to a first device to control the first device and communicates with the server by using a first communication scheme; and a second module which is connected to a second device to control the second device and communicates with the server by using a second communication scheme different from the first communication scheme, wherein: the server transmits, to the fist module, first control data for controlling the first device and transmits, to the second module, second control data for controlling the second device; and the first control data includes a first control command and a first delay for delaying the time when the first device is controlled by the first control command.

Description

building energy management system

The present invention relates to a building energy management system, and more particularly, to a building energy management system for regulating the control of devices disposed in a building.

Recently, many countermeasures for controlling carbon emissions have been in the limelight. Regarding carbon emissions, there is a growing need to efficiently consume and manage the energy of devices deployed in buildings, in particular. A building energy management system is needed to comprehensively manage building energy by grafting efficient IoT technology and machine learning technology to devices deployed in buildings.

One object of the present invention relates to a building energy management system for efficiently controlling devices disposed in a building.

According to an embodiment of the present invention, a building energy management system for efficiently controlling devices disposed in a building may be provided.

1 is a diagram for explaining devices and modules disposed in a building.

2 is an environmental diagram of a building energy management system according to an embodiment.

3 is a diagram for explaining pattern data according to an exemplary embodiment.

4 is a diagram illustrating an example of pattern data according to an exemplary embodiment.

5 is a diagram for explaining control data and delay measurement according to an exemplary embodiment.

Building energy management system according to an embodiment is a building energy management system for managing the energy of a building by collecting information of modules connected to a plurality of devices disposed in a building, a communication unit for transmitting and receiving data with a plurality of modules, the plurality A server including a storage unit for storing data received from the module and a control unit for controlling a device connected to each module through the plurality of modules; a first module connected to a first device, controlling the first device, and communicating with the server in a first communication method; and a second module connected to a second device to control the second device and to communicate with the server in a second communication method different from the first communication method, wherein the server is configured to control the first device. First control data is transmitted to the first module, and second control data for controlling the second device is transmitted to the second module, the first control data being a first control command and the first control command. may include a first delay for delaying the time at which the first device is controlled by

Here, the server transmits a first reference signal to the first module and a second reference signal to the second module, and transmits a response to the first reference signal from the first module at a first point in time. 1 Receive a response signal, receive a second response signal that is a response to the second reference signal at a second time point from the second module, and receive the first response signal based on a difference between the first time point and the second time point. Delay can be set.

Here, the first module transmits first performance data including the first delay as a response to the first control data to the server, and the second module transmits a response to the second control data to the server. Transmits the second performance data, and the server can simultaneously process the first performance data and the second performance data at a point in time based on the first delay included in the received first performance data.

Here, the first module may control the first device based on the first control command after a time corresponding to the first delay has elapsed from the time of receiving the first control data.

Here, the first control command may include information for controlling at least one of power, illumination, temperature, and humidity of the first device.

Here, the first communication method may be Wi-Fi or Bluetooth, and the second communication method may be ZigBee.

Here, the second control data includes a second control command and a second delay for delaying a time at which the second device is controlled by the second control command, wherein the second delay includes the first delay and the second delay. It may be set based on the first transmission time point, which is the time when the first control data is transmitted, and the second transmission time point, which is the time point when the second control data is transmitted.

A building energy management method according to an embodiment is a building energy management method for managing energy of a building by collecting information of modules connected to a plurality of devices disposed in a building, comprising transmitting a first reference signal to a first module. ; transmitting a second reference signal to a second module; receiving a first response signal that is a response to the first reference signal at a first point in time from the first module; receiving a second response signal that is a response to the second reference signal at a second point in time from the second module; setting a first delay based on a difference between the first time point and the second time point; and generating and transmitting first control data including a first control command for controlling a first device and the first delay to the first module.

The embodiments described in this specification are intended to clearly explain the spirit of the present invention to those skilled in the art to which the present invention belongs, so the present invention is not limited to the embodiments described in this specification, and the The scope should be construed to include modifications or variations that do not depart from the spirit of the invention.

The terms used in this specification have been selected as general terms that are currently widely used as much as possible in consideration of the functions in the present invention, but these may vary depending on the intention of those skilled in the art, precedents, or the emergence of new technologies to which the present invention belongs. can However, in the case where a specific term is defined and used in an arbitrary meaning, the meaning of the term will be separately described. Therefore, the terms used in this specification should be interpreted based on the actual meaning of the term and the overall content of this specification, not the simple name of the term.

The drawings accompanying this specification are intended to easily explain the present invention, and the shapes shown in the drawings may be exaggerated as necessary to aid understanding of the present invention, so the present invention is not limited by the drawings.

If it is determined that a detailed description of a known configuration or function related to the present invention in this specification may obscure the gist of the present invention, a detailed description thereof will be omitted if necessary.

1 is a diagram for explaining devices and modules disposed in a building. FIG. 1(a) is a diagram for explaining a device disposed in a building, and FIG. 1(b) is a diagram for explaining a module connected to the device.

Referring to Fig. 1(a), a plurality of devices disposed in a building are shown. BACKGROUND OF THE INVENTION In general, a plurality of devices including an access device, a lighting device, a cooling/heating device, a circulation device, and a power supply device are disposed inside and outside of a building.

The access device disposed in the building may include a door lock, a door locking device, an automatic door device, an automatic revolving door, or an authentication device through supplementation. Lighting devices included in buildings may include devices that output light, such as light bulbs, LED lights, emergency lights, and the like, some of which may have adjustable illumination.

Air-conditioning and heating devices disposed in buildings may include devices for controlling indoor temperature, such as air conditioners, heaters, heaters, and radiators, some of which may also control indoor humidity. The circulation device disposed in the building may include a device capable of circulating air in the building, such as a circulator and a ventilation fan. A power supply unit disposed in a building may include a power supply, an outlet, and the like.

Referring to FIG. 1(b), a module connected to an outlet disposed in a building is shown. In FIG. 1(b), an example of a device is an outlet, but a device that can be connected to a module may be an access device, a lighting device, a cooling/heating device, a circulation device, and each device included in a power supply device.

The module may be connected to the device, collect information related to energy of the device, and control the device. Specifically, the module may be connected to a wire or circuit inside the device to collect data and transmit the collected data to a server. A detailed description of the module is described in FIG. 2 .

Referring to FIG. 2 , a building energy management system according to an embodiment may include a server 1000, one or more modules, and one or more devices.

As shown in FIG. 1(b), the

modules

100 and 200 may be connected to a device to collect device data. Specifically, the module may collect information related to the device's energy.

According to one embodiment, the module may collect voltage, current, power amount or power factor information of the device. The module may collect the parameters in real time or periodically or non-periodically by a control command of the server 1000 . In addition, the module may also collect information about whether or not arcing of the device and arc current when arcing occurs.

According to another embodiment, the module may collect information about control of the device. Specifically, the module may collect information on who controlled the device, where, for which item, and with what content.

For example, for a lighting device in a room, the module may collect information about when the lighting device was powered off by a person inside the room at one point in time. Also, for an air conditioner, for example, the module may collect information about the fact that the power of the air conditioner is turned off by a reservation function of the air conditioner at a point in time.

Also, for example, for a heater in a room, the module may collect information about a decrease in the set temperature of the heater by a user terminal outside the room at a point in time. Also, for example, for an outlet in a room, the module may collect information about the outlet being turned off by an external device at a point in time.

The server 1000 is a central component of the building energy management system and may serve as an overall controller of the building energy system.

The server 1000 may be connected to the first module 100 and the second module 200 . In addition, the server 1000 may be connected to the first module 100 and the second module 200 to exchange communication signals.

Alternatively, when a device has a communication function, the server 1000 may directly exchange communication signals with each device without going through a module. However, since it is rare that a device has a communication function, an example in which the server 1000 collects device information through a module will be mainly described in this specification.

Although not shown in FIG. 1 , a device for relaying communication between the server 1000 and the first module 100 and the second module 200 may exist. For example, another module may exist between the server 1000 and the first module 100, and the another module may transmit a communication signal between the server 1000 and the first module 100.

Also, for example, a sub-server or edge computing may exist between the server 1000 and the first module 100 to transmit a communication signal between the server 1000 and the first module 100 . That is, the server 1000 and each module can communicate with each other without limiting distance.

According to an embodiment, the server 1000 may include a control unit 1100, a communication unit 1200, a storage unit 1300, and an analysis unit 1400.

1 illustrates four components included in the server 1000, the illustrated components are not essential, and the server 1000 may have more or fewer components. In addition, each component of the server 1000 may be physically included in one server or may be a distributed server distributed for each function.

The controller 1100 may oversee operations of the server 1000 . Specifically, the controller 1100 may send control commands to the communication unit 1200, the storage unit 1300, and the analysis unit 1400 to execute operations of each department.

Unless otherwise noted below, the operation of the server 1000 may be interpreted as being performed under the control of the controller 1100 .

The communication unit 1200 may connect the server 1000 and an external device to communicate with each other. That is, the communication unit 1200 can transmit/receive data with an external device. For example, the communication unit 1200 may exchange data with the first module 100 or the second module 200 .

According to an embodiment, the communication unit 1200 may receive energy information of a device connected to the module from the module. For example, the communication unit 1200 may receive energy information of the first device from the first module 100 . A detailed description thereof will be described below with reference to FIG. 3 .

The communication unit 1200 may be a communication module supporting at least one of a wired communication method and a wireless communication method. For example, the communication unit may acquire data from an external device through communication methods such as WiFi, Bluetooth, Zigbee, Bluetooth Low Energy (BLE), and RFID.

The storage unit 1300 may store various data and programs necessary for the server 1000 to operate. The storage unit 1300 may store information acquired by the server 1000 .

For example, the storage unit 1300 may store information about energy of a device received by the communication unit 1200 through a module. Also, the storage unit 1300 may store information about control of each device.

The storage unit 1300 may temporarily or semi-permanently store data. Examples of the storage unit 1300 include a hard disk drive (HDD), a solid state drive (SSD), a flash memory, a read-only memory (ROM), and a random access memory (RAM). Or there may be Cloud Storage. However, it is not limited thereto, and the storage unit 1300 may be implemented with various modules for storing data.

The storage unit 1300 may be provided in a form built into the wearable device 1000 or in a detachable form.

The analysis unit 1400 may analyze data acquired by the communication unit 1200, classify the data, and generate new data. In this case, the analysis unit 1400 may input data into the learned machine learning model and analyze data related to the device. The analyzer 1400 may analyze the reason for controlling the device at each point in time through a machine learning model. The analysis unit 1400 may continuously train the machine learning model through data input to the machine learning model.

According to an embodiment, the analysis unit 1400 may analyze or classify device data acquired by the communication unit 1200 . Specifically, the analysis unit 1400 may analyze or classify information related to energy of the device.

For example, the analysis unit 1400 may analyze the power status of the device by analyzing the voltage, current, power amount, and the like of the device. In addition, the pumice unit 1400 may analyze the arc generation status of the device by analyzing whether or not arc generation of the device and the arc current.

Also, in detail, the analyzer 1400 may analyze or classify information related to device control. For example, the analyzer 1400 may analyze data on how the device controlled which item by whom at a point in time. In addition, the analysis unit 1400 may classify control data according to the 5-W-W principle.

For a specific example, the analyzer 1400 may classify the control of the device into a control subject, a control place, a control item, and a control content, and generate control information according to the classification.

The analyzer 1400 may generate pattern data including information related to device energy and control information according to classification. Also, the analyzer 1400 may establish a control policy for the device thereafter based on the pattern data. Pattern data generated by the analysis unit will be described in detail below with reference to FIG. 3 .

3 is a diagram for explaining pattern data generated by a server according to an exemplary embodiment. 4 is a diagram illustrating an example of pattern data according to an exemplary embodiment.

Referring to FIG. 3 , pattern data may include energy information and control information.

The energy information included in the pattern data is information related to energy of the device and may include power data and/or arc data.

As shown in FIG. 4 , the power data may include voltage, current, power amount, and/or power factor information of the device. The voltage, current, power and power factor of the device change over time, and the device transmits the time-varying corresponding information to the module. The device may transmit the information to the module in real time, periodically, transmit only when there is a change, or may transmit the information non-periodically at the request of the module.

As shown in FIG. 4 , the arc data may include information about whether an arc is generated in the device and arc current when an arc is generated. Arcing can occur due to external shocks and internal circuit problems in the device. The device continuously monitors arcing and can sense arc current when arcing occurs. The device may transmit arc-related information to the module in real time, periodically, transmit it only when there is a change, or transmit it non-periodically at the request of the module.

The control information included in the pattern data is information related to device control, and may include information related to a control subject, a control place, a control item, and/or control content.

As shown in FIG. 4 , a control entity controlling a device may be a person, an application, an internal device, or an external device. Specifically, the device may be controlled by a person operating a switch, an application on a user terminal, a reservation system inside the device, or manipulation by an external device.

In addition, the place where the device is controlled may be a place where the control subject is located according to the controlling subject. Specifically, when the control subject is a person, the control place becomes a place where a switch is placed, and when the control subject is an application, the control place may be determined based on GPS sensing information of the user terminal. Further, when the control subject is an internal device, the control place may be a place where the device is located, and when the control subject is an external device, the control place may be a place where the external device is located.

In addition, control items and contents controlling the device may vary depending on the type of device. For example, if the device is an air conditioner, the control items may be power, temperature, and humidity, and the control content may be on, off, increase, or decrease. Also, for example, when the device is a lighting device, the control items may be power and illuminance, and the control content may be on, off, increase, or decrease.

Referring to FIG. 4 , the server 1000 may generate pattern data according to time. The pattern data of FIG. 4 is pattern data generated by the server 1000 for the lighting device.

For example, the server 1000 may generate pattern data including control information and energy information of the device according to the first time point (01:00). In this case, the control information of the first view may include information indicating that a person in room 1 has turned on the power of the lighting device. Also, at this time, the energy information of the first time point may include information about that the lighting device had a voltage, b current, c power amount, and d power factor at the first time point, and no arc was generated.

Also, the pattern data may include control information and energy information of the device according to the second time point (02:00). In this case, the control information of the second view may include information about an increase in illuminance of the lighting device by the user terminal in room 1. Also, at this time, the energy information of the second time point may include information indicating that the lighting device had e voltage, f current, g power factor, and h power factor at the second time point, and no arc was generated.

The server 1000 may analyze the pattern data and then establish a policy for building energy. Specifically, by analyzing the energy information of the device according to the control information, a policy to be controlled by the device at a specific time point may be established. In addition, in detail, by analyzing the energy information of the device according to the control information, a policy to be controlled by the device according to a specific control subject may be established.

For example, based on information included in the pattern data, when the server 1000 determines that a lighting device is turned on by a person at 9:00 am, the server 1000 automatically activates the lighting device every 9:00 am. It is possible to set the control for the lighting device so that it can be turned on.

Also, for example, based on the information included in the pattern data, when the server 1000 recognizes that the set temperature reduction control is repeatedly performed on the air conditioner after the indoor temperature reaches 25 degrees or higher, the server 1000 determines that the indoor temperature is 25 degrees or more. The set temperature can be adjusted so that the temperature does not exceed 25 degrees.

In addition, after establishing a policy, the server 1000 may transmit a control command to each device through a module according to the policy.

For example, the server 1000 may transmit a control command to turn off the power of a lighting device and power off an air conditioner at 6:00 pm according to an office leave policy to each module. In this case, each module may control the power of a device connected to each module to be turned off based on the received control command.

Also, for example, the server 1000 may transmit a control command for setting a set temperature of a heater to 24 degrees for a certain period of time according to a winter policy to each module. At this time, each module can be controlled so that the set temperature of the heater connected to each module is 24 degrees based on the received control command.

When the server 1000 transmits control data including a control command to each module according to a policy, the time at which device control is performed may vary depending on the communication method of each module. Specifically, the first module 100 communicates with the server 1000 in a first communication method, and the second module 200 communicates with the server 1000 in a second communication method different from the first communication method. can

The reason why modules have different communication methods may be due to a device connected to the module. Alternatively, a communication method may be different for each place where each device is installed. For example, a module connected to an outlet may communicate with the server 1000 through Wi-Fi or Bluetooth, and a module connected to a lighting device may communicate with the server 1000 through ZigBee. In this case, the ZigBee communication method may be slower than the Wi-Fi or Bluetooth communication method.

Due to differences in communication methods, even if the server 1000 transmits the same control command to the module, control performed by the control command may be performed differently in each device.

For example, the server 1000 applies the same control data to a first module connected to the first lighting device and a second module connected to the second lighting device so that the first lighting device and the second lighting device are turned on. can transmit

In this case, the first module communicating with the server 1000 through the first communication method may change the power of the first lighting device to an on state at a first time point based on the received control data. However, the second module communicating with the server 1000 through the second communication method may change the power of the second lighting device to an on state at a second time point later than the first time point based on the received control data. there is.

Externally, although the server 1000 transmits control data at the same time, it can be confirmed that the power of each lighting device is not simultaneously turned on but turned on separately. This may be seen as an error in the building energy management system included in the server 1000 .

Also, internally, the server 1000 needs to process data related to each module with the same time stamp. If the server 1000 processes data related to each module that does not come in uniformly according to the difference in communication speed, the server 1000 cannot process the data in batches, so it is necessary to manage it with one time stamp. there is.

Therefore, there is a need for a building energy management system that can consider the speed difference of the communication method. The speed difference of the communication method can be solved by including a delay in the control data.

5 is a diagram for explaining control data and delay measurement according to an exemplary embodiment. 5(a) is a diagram for explaining control data, and FIG. 5(b) is a diagram for explaining an example of measuring a delay.

Referring to FIG. 5(a) , control data transmitted by the server 1000 to each module may include a delay (D) and a control command (M, information). For example, when the control data is 255 bits, the server 1000 may allocate a delay to 2 bits and allocate a control command to the remaining bits.

When control data including a delay is transmitted to the module, the module may operate in a buffer state for a time corresponding to the delay. That is, the module may not process data for a time corresponding to the delay, and may process data after the time elapses. In this case, processing the data may mean controlling the device by transmitting a control command to the device.

Referring to FIG. 5( b ), an example of a method of setting a delay included in control data is shown. The server 1000 may send a signal to the first module and the second module in advance, identify a time at which the signal is received by the module, and set a delay based on a difference between the times at which the signal is received.

For example, the server 1000 may transmit a first reference signal R1 to a first module in a first communication method and transmit a second reference signal R2 to a second module in a second communication method. At this time, the reference signal may be a basic communication signal that does not include a control command. Also, the first reference signal R1 may be the same as the second reference signal R2.

At this time, as shown in FIG. 5( b ), the server 1000 may simultaneously transmit the first reference signal R1 and the second reference signal R2 at the reference point in time t0. However, the server 1000 is not limited thereto, and the server 1000 may determine the speed difference between the communication methods of each module in another method without simultaneously transmitting the first reference signal R1 and the second reference signal R2.

For example, by transmitting a first reference signal R1 at a first time point and receiving a response to the first reference signal R1 at a second time point, the first reference signal R1 is transmitted based on the first time point and the second time point. You can grasp the speed of the communication method. In addition, the second communication method is based on the third and fourth points of view by transmitting the second reference signal R2 at a third time point and receiving a response to the second reference signal R2 at a fourth time point. speed can be found.

Upon receiving the first reference signal R1, the first module may transmit the first response signal Rp1, which is a response to the first reference signal R1, to the server 1000 again. At this time, the first response signal Rp1 may be a simple ACK signal. The server 1000 may receive the first response signal Rp1 at a first time point t1.

Upon receiving the second reference signal R2, the second module may transmit the second response signal Rp2, which is a response to the second reference signal R2, to the server 1000 again. At this time, the second response signal Rp2 may be a simple ACK signal. The server 1000 may receive the second response signal Rp2 at a second time point t2.

The server 1000 may calculate a difference between the first time point t1 and the second time point t2. In this case, the difference may mean a speed difference between the first communication method and the second communication method. The server 1000 may set a delay to be included in the control data based on the difference.

In addition, when the delay is set based on the difference, not only the difference in communication speed but also the difference in data processing speed for each module can be reflected.

When the server 1000 simultaneously transmits control data to the first module and the second module, the first control data including the delay set based on the difference is transmitted to the first module, and the second data not including the delay is transmitted to the first module. can be transmitted to the second module.

Alternatively, when the server 1000 simultaneously controls the first device and the second device but does not simultaneously transmit control data to each module, the first control data including the first delay set based on the difference is transmitted to the first module. and transmits second control data including a second delay set based on a time point at which the first control data is transmitted, the first delay, and a time to transmit data to the second module, to the second module. That is, when the server 1000 does not simultaneously transmit control data to each module, the delay calculated for each control data transmitted to each module may be included and transmitted to each module.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. Program commands recorded on the medium may be specially designed and configured for the embodiment or may be known and usable to those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. - includes hardware devices specially configured to store and execute program instructions, such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter, as well as machine language codes such as those produced by a compiler. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

As described above, although the embodiments have been described with limited examples and drawings, those skilled in the art can make various modifications and variations from the above description. For example, the described techniques may be performed in an order different from the method described, and/or components of the described system, structure, device, circuit, etc. may be combined or combined in a different form than the method described, or other components may be used. Or even if it is replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents of the claims are within the scope of the following claims.

Claims

In the building energy management system for managing the energy of a building by collecting information on modules connected to a plurality of devices placed in a building,

A server including a communication unit for transmitting and receiving data with a plurality of modules, a storage unit for storing data received from the plurality of modules, and a control unit for controlling devices connected to each module through the plurality of modules;

a first module connected to a first device, controlling the first device, and communicating with the server in a first communication method; and

a second module connected to a second device to control the second device and to communicate with the server in a second communication method different from the first communication method;

The server transmits first control data for controlling the first device to the first module and transmits second control data for controlling the second device to the second module;

The first control data includes a first control command and a first delay for delaying a time at which the first device is controlled by the first control command.

Building Energy Management System.
According to claim 1,

The server,

transmits a first reference signal to the first module and a second reference signal to the second module;

A first response signal, which is a response to the first reference signal at a first time point, is received from the first module, and a second response signal, which is a response to the second reference signal at a second time point, is received from the second module. do,

Setting the first delay based on the difference between the first time point and the second time point

Building Energy Management System.
According to claim 1,

The first module transmits first performance data including the first delay in response to the first control data to the server,

The second module transmits second performance data to the server in response to the second control data,

The server simultaneously processes the first performance data and the second performance data at a point in time based on the first delay included in the received first performance data

Building Energy Management System.
According to claim 1,

The first module controls the first device based on the first control command after a time corresponding to the first delay has elapsed from the time of receiving the first control data.

Building Energy Management System.
According to claim 4,

The first control command includes information for controlling at least one of power, illumination, temperature, and humidity of the first device.

Building Energy Management System.
According to claim 1,

The first communication method is Wi-Fi or Bluetooth,

The second communication method is ZigBee.

Building Energy Management System.
According to claim 2,

The second control data includes a second control command and a second delay for delaying a time at which the second device is controlled by the second control command,

The second delay is set based on the first delay, the first transmission time when the first control data is transmitted, and the second transmission time when the second control data is transmitted

Building Energy Management System.
A building energy management method for managing energy of a building by collecting information of modules connected to a plurality of devices disposed in a building,

transmitting a first reference signal to the first module;

transmitting a second reference signal to a second module;

receiving a first response signal that is a response to the first reference signal at a first point in time from the first module;

receiving a second response signal that is a response to the second reference signal at a second point in time from the second module;

setting a first delay based on a difference between the first time point and the second time point; and

Generating and transmitting a first control command for controlling a first device and first control data including the first delay to the first module.

How to manage building energy.