Abstract:
Disclosed are an apparatus for diagnosing a relay contact of an electric vehicle and a method thereof. The method includes measuring a first voltage input from a high-voltage battery to an inverter; comparing the first voltage with a second voltage output through the high-voltage battery; identifying a detection time point of the first voltage when the first voltage is greater than the second voltage; and determining whether a high-voltage relay, which intermits an output voltage of the high-voltage battery, is malfunctioned based on the identified detection time point.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Pursuant to 35 U.S.C.§119 (a), this application claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2012-0054264, filed on May 22, 2012, the contents of which are hereby incorporated by reference in their entirety. 
       BACKGROUND 
       [0002]    The embodiment relates to a diagnostic apparatus connected to an inverter for an electric vehicle. More particularly, the embodiment relates to an apparatus for diagnosing a relay contact, which is installed at a power line connected to a motor controller to diagnose fusion of a high voltage relay contact that switches a main power source on or off, and a method thereof. 
         [0003]    An inverter serving as a motor controller employed in an eco-friendly vehicle is an electric/electronic sub-assembly (ESA) to convert high-voltage DC power into AC power or DC power for the purpose of controlling a motor. The inverter is a main component serving as an electric driving device of a vehicle. 
         [0004]    In such an eco-friendly vehicle, a high-voltage relay is connected to a power line for each motor and each motor controller including an inverter such that the high-voltage relay switches on or off of the battery serving as a main power source. The high-voltage relay is equipped with an emergency operation control function for driving a vehicle through the motor and the power cutoff function even when an emergency operation is performed caused by the failure of two motors and two motor controller from among three motors and three motor controllers. 
         [0005]    That is, when dielectric breakdown or a problem occurs in an IGBT (Insulated Gate Bipolar Transistor), which is an inverter included in the motor controller, due to an overvoltage or overcurrent while the vehicle is being operated, the high-voltage relay connected to the power line cuts off the power being supplied to the corresponding motor and motor controller and performs an emergency operation using other motors and motor controllers which remain in a normal state. 
         [0006]    Since large current flows bilaterally through the high-voltage relay which controls the power supply to the motor and the motor controller, the possibility of the fusion of the high-voltage relay is very high due to a temperature increase and a fault component. Since it is impossible in the fusion state to cut off the power supply to the motor and the motor controller subject to troubles, the counter electromotive force generated due to the rotation of the motor having the trouble exerts effect on other normal motors and motor controller so that a continuous current flow occurs. 
         [0007]      FIG. 1  is a flowchart illustrating a method of diagnosing a relay contact point according to the related art which is disclosed in Korean Patent Application No. 10-2009-0118728. 
         [0008]    Referring to  FIG. 1 , in a state that a fuel cell vehicle is operated in step S 101 , it is determined in step S 102  whether a fuel cell stack is normally shut down in response to a stop of the vehicle. 
         [0009]    In step S 102 , if the fuel cell stack is normally shut down, a main controller primarily turns off the first to third relays Ry 1 , Ry 2  and Ry 3  such that the output powers of the fuel cell stack and the super capacitor are primarily shut down and then turns off the fourth relay which is a high-voltage relay, so that the power supply to the motor controller is blocked. 
         [0010]    In this case, although a periphery complementary apparatus blocks the hydrogen supplied to the anode of the fuel cell stack and supplies oxygen to remove residual hydrogen, since power is not normally supplied, energy of an internal capacitor C is used to drive the periphery complementary apparatus so that a voltage variation occurs. 
         [0011]    In addition, if the power supplied to the motor controller is shut off as the fourth relay Ry 4  is turned off, a voltage drop of a capacitor C 1  is constantly caused by an internal resistance R. 
         [0012]    Thus, a main controller detects a voltage variation (Δ(LDC) of the internal capacitor C in step S 103 , detects a voltage variation (Δ(MCU)) of the internal capacitor C 1  in step S 104 , and then compares the two detected voltage variation values with each other in step S 105 . 
         [0013]    It is determined in step S 106  whether the detected main voltage values are equal to each other. If the voltage values are not equal to each other, it is determined in step S 109  that the high-voltage relay Ry 4  connected to the power line is normal. 
         [0014]    However, if the voltage values are equal to each other, it is determined in step S 107  that the periphery complementary apparatus uses the voltage of the internal capacitor C 1  of the motor controller due to the fusion of the high-voltage relay Ry 4  connected to the power line of the motor controller. 
         [0015]    As described above, if it is determined that the fusion of the high-voltage relay Ry 4  connected to the power line occurs, a diagnostic code is stored in a memory such that a driver can rapidly exchange the relay. 
         [0016]    The method of diagnosing a relay contact according to the related art is performed when the ignition is shut down through a separated electric component (LDC; low voltage DC-DC converter) in order to detect a fusion of a relay. 
         [0017]    However, the method of diagnosing a relay contact according to the related art requires the connection with the separated electric component (LDC) and is performed upon the shutdown. When the separated electric component is out of order upon the shutdown, the relay diagnosis is not normally performed, so that a driver may be subject to the dangerous situation. 
       SUMMARY 
       [0018]    The embodiment provides an apparatus for diagnosing a relay contact which can diagnose the relay contact using only a motor controller without a separated electric component and a method thereof. 
         [0019]    The embodiment provides an apparatus for diagnosing a relay contact, capable of preventing an emergency situation due to malfunction of vehicular components by diagnosing the relay contact state upon the ignition-on state other than the shutdown state. 
         [0020]    Meanwhile, the objects accomplished by the embodiments may not be limited to the above object, and those skilled in the art can clearly understand other objects from following description. 
         [0021]    According to the embodiment, there is provided a method of diagnosing a relay contact of an electric vehicle. The method includes measuring a first voltage input from a high-voltage battery to an inverter; comparing the first voltage with a second voltage output through the high-voltage battery; identifying a detection time point of the first voltage when the first voltage is greater than the second voltage; and determining whether a high-voltage relay, which intermits an output voltage of the high-voltage battery, is malfunctioned based on the identified detection time point. 
         [0022]    According to the embodiment, there is provided an apparatus for diagnosing a relay contact of an electric vehicle. The apparatus includes a high-voltage battery serving as a main power source; an inverter receiving a DC (direct current) electrical power from the high-voltage battery and driving a motor by changing a phase of the DC electrical power; and a high-voltage relay between the high-voltage battery and the inverter, the high-voltage relay intermitting the DC electrical power output through the high-voltage battery, wherein the inverter determines whether the high-voltage relay is malfunctioned based on a time point at which a DC link voltage value according to the supplying of the DC electrical power is equal to or greater than a voltage value of the high-voltage battery and intermits a power input to the motor according to a diagnosis result. 
         [0023]    According to the embodiment, it is diagnosed whether the high-voltage relay installed on the power line of the electric vehicle is fused and the diagnosis result is indicated to the driver, so that a rapid repair or exchange can be performed before driving the vehicle, thereby improving stability and reliability. 
         [0024]    According to the embodiment, an inverter may diagnose the fusion of a relay without interworking with other electric components so that a user may take necessary measures against a dangerous situation based on the fusion state of the relay. 
         [0025]    Further, according to the embodiment, it is diagnosed upon the ignition-on state of the electric vehicle whether the relay is fused, so that the electric vehicle can be prevented from being driven at the fusion state of the electric vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a flowchart illustrating a method of diagnosing a relay contact point according to the related art; 
           [0027]      FIG. 2  is a circuit diagram showing an electric vehicle according to the embodiment; 
           [0028]      FIG. 3  is a block diagram showing in detail the inverter depicted in  FIG. 2 ; 
           [0029]      FIG. 4  is a graph illustrating a voltage variation in a normal operation according to the embodiment; 
           [0030]      FIG. 5  is a graph illustrating a voltage variation in an abnormal operation according to the embodiment; and 
           [0031]      FIG. 6  is a flowchart illustrating a method of diagnosing a relay contact step by step according to the embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0032]    The principle of the embodiments will be described below. Therefore, although not specifically described and depicted in the specification, a person having the ordinary skill in the art may realize the principle of the embodiments and may invent various apparatuses within the concept and scope of the embodiments. Further, in principle, conditional terms and embodiments mentioned in the specification shall be obviously intended to understand the concept of the embodiments and may not limit the scope of the embodiments. 
         [0033]    Further it shall be understood that all detailed descriptions, which teach a specific embodiment as well as a principle, an aspect and embodiments, are intended to include structural and functional equivalents. Further, it should be understood that the equivalents may include equivalents to be developed in the future as well as known equivalents and may include all devices invented for performing the same functions regardless of the structure thereof. 
         [0034]    According to the embodiment, an inverter may diagnose the fusion of a relay without interworking with other electric components so that a user may take necessary measures against a dangerous situation based on the fusion state of the relay. 
         [0035]      FIG. 2  is a circuit diagram showing an electric vehicle according to the embodiment. 
         [0036]    Referring to  FIG. 2 , the electric vehicle  200  includes a high-voltage battery  210 , a high-voltage relay  220 , an inverter  230  and a motor  240 . 
         [0037]    The high-voltage battery  210  supplies a driving electrical power to the electric vehicle  200 . Specifically, the high-voltage battery  210  supplies a DC electrical power to a capacitor C in the electric vehicle  200 . 
         [0038]    The high-voltage battery  210  may include a set of a plurality of unit cells. The unit cells may be managed by a BMS (Battery Management System) in order to maintain a constant voltage. Thus, the unit cells may output the constant voltage by the BMS. 
         [0039]    For example, the BMS may detect a voltage of the high-voltage battery  210  and may transfer the detected voltage to an electronic control unit (not shown) or the inverter in the electric vehicle  200 . The BMS may supply a DC electrical power stored in a capacitor of the electric vehicle to the battery when the battery voltage is dropped down below a lower limit value. Further, when the battery when the battery voltage is increased to or over an upper limit value, a DC electrical power may be supplied to the capacitor C of the electric vehicle  200 . 
         [0040]    Preferably, the high-voltage battery  210  includes a secondary battery which is capable of being charged or discharged, but the embodiment is not limited thereto. 
         [0041]    The high-voltage relay  220  is connected to a predetermined power line connected to the high-voltage battery  210 , such that the high-voltage relay  220  intermits the DC electrical power output through the high-voltage battery  210 . 
         [0042]    Specifically, the high-voltage relay  220  may include first and second high-voltage relays  220 . The first high-voltage relay is connected to a positive terminal of the high-voltage battery  210  such that a DC power source is intermitted. The second high-voltage relay is connected to a negative terminal of the high-voltage battery  210  such that the DC power source is intermitted. 
         [0043]    The DC electrical power is provided from the high-voltage battery  210  to the inverter  230  according to a state of the high-voltage relay  220 . The inverter  230  converts the DC electrical power into an AC electrical power and provides the AC electrical power to the motor  240 . Preferably, the AC electrical power converted by the inverter  230  includes a three-phase AC electrical power. 
         [0044]    The inverter  230  provides the three-phase AC electrical power to the motor  240  through a three-phase cable. The three-phase cable may be composed of separated three cables. To the contrary, three cables may be included in a single three-phase cable. 
         [0045]    Specifically, the inverter  230  includes an IGBT (Insulated Gate Bipolar Transistor) and executes a PWM (Pulse Width Modulation) switching operation according to a control signal applied thereto by a control unit which will be described below, such that a phase of the electrical power supplied to the high-voltage battery  210  is converted to drive the motor  240 . 
         [0046]    The motor  240  includes a stator (not shown), which is in a stationary state without rotation, and a rotor (not shown) rotating. The motor  240  receives AC voltage that is supplied through the inverter  230 . For example, the motor  240  may be a three-phase motor. When each phase AC electrical power, which has a variable voltage/frequency, is applied to each stator coil in each phase, a rotation speed of the rotor varies depending on the applied frequency. 
         [0047]    The motor  240  may include various types of motors such as an induction motor, a BLDC (blushless DC) motor, or a reluctance motor. 
         [0048]    Meanwhile, the motor  240  may be provided at one side thereof with a driving gear (not shown). The driving gear converts the rotational energy of the motor  240  according to a gear ratio. The rotational energy of the driving gear is transferred to a front wheel and/or a rear wheel so that the electric vehicle  200  moves. 
         [0049]    Meanwhile, although not shown, the electric vehicle may further include an electronic controller to control whole electronic devices of the electric vehicle. The electronic controller (not shown) controls the operation and the displaying of each device. The electronic controller (not shown) may control the BMS. 
         [0050]    In addition, the electronic controller may generate a driving instruction value according to various operation modes (driving mode, rearward mode, neutral mode, and parking mode) based on detection signals transferred from an inclination angle detector (not shown) to detect the inclination angle of the electric vehicle, a speed detector (not shown) to detect the speed of the electric vehicle, a brake detector (not shown) according to the operation of a brake pedal, or an acceleration detector according to the operation of an acceleration pedal. In this case, for example, the driving instruction value may include a torque instruction value or a speed instruction value. 
         [0051]    Meanwhile, the electric vehicle  200  according to one embodiment may include a pure electric vehicle employing a battery and a motor, and a hybrid electric vehicle employing a battery and a motor together with an engine. 
         [0052]    In this case, the hybrid electric vehicle may include a switching unit to select at least one of the battery and the engine, and a transmission. Meanwhile, the hybrid electric vehicle is classified into a series hybrid electric vehicle, which converts mechanical energy output from an engine into electrical energy to drive the motor, and a parallel hybrid electric vehicle which uses both of the mechanical energy output from the engine and the electrical energy output from the battery. 
         [0053]      FIG. 3  is a block diagram showing in detail the inverter depicted in  FIG. 2 . 
         [0054]    The contact diagnosis technique according to the embodiment will be described with reference to  FIG. 3 . 
         [0055]    Referring to  FIG. 3 , the inverter  230  includes a digital power source  231 , a DC link input unit  232 , a memory  233 , a main control unit  234 , a motor control output unit  235  and a display  236 . 
         [0056]    The digital power source  231  allows a DC electrical power supplied through the high-voltage battery  210  to be dropped down so that a driving electric power is provided to the main control unit  234  and the memory  233 . 
         [0057]    The digital power source  231  may be a DC-DC converter. That is, the digital power source  231  which is a low DC/DC converter, converts the high voltage supplied from the high-voltage battery  210  into a low voltage and provides the low voltage to various electronic components mounted on the electric vehicle  200 . 
         [0058]    The DC link input unit  232 , which is an input of the DC electrical power, is connected to the high-voltage battery  210 , so that the DC link input unit  232  receives the high-voltage DC electrical power provided from the high-voltage battery  210 . 
         [0059]    Data, which are required to operate the inverter  230  and data which are generated while the inverter  230  is operated, are stored in the memory  233 . The memory  233  may be implemented with a memory medium such as EEPROM. 
         [0060]    Specifically, the memory  233  stores diagnosis information about a result of a diagnosis performed while the inverter  230  is operated. 
         [0061]    The main control unit  234  controls the overall operation related to the voltage generation of the high-voltage battery  210  and controls the overall operation of the electric vehicle  200  the high-voltage relay  220  by controlling the high-voltage relay  220  and the inverter  230 . 
         [0062]    At the time point at which the electric vehicle  200  is turned on, the main controller  234  controls the operation of the high-voltage relay  220  to allow the high-voltage battery  210  to output the DC electrical power to the inverter  230 . 
         [0063]    At the time point at which the electric vehicle  200  is turned off, the main controller  234  controls the operation of the high-voltage relay  220  to block the electrical power output to the inverter  230 . 
         [0064]    That is, at the time point at which the electric vehicle  200  is turned on, the main controller  234  compares the first voltage input to the DC link input unit  232  with the second voltage output through the high-voltage battery  210  to diagnose the contact state of the high-voltage relay  220 . 
         [0065]    That is, at the time point at which the electric vehicle  200  is turned on, the main controller  234  allows the high-voltage relay  220  to be turned on to allow the DC electrical power charged in the high-voltage battery  210  to be provided to the inverter  230 . 
         [0066]    In this case, the main controller  234  compares the levels of the first voltage input to the DC link input unit  232  and the second voltage output through the high-voltage battery  210  with each other, and diagnoses whether the high-voltage relay  220  is fused based on the comparison result. 
         [0067]    That is, when the high-voltage relay  220  is turned on, the DC electrical power charged in the high-voltage battery  210  is provided to the inverter  230 . In this case, the DC electrical power, which is initially provided to the inverter  230  (at the time point at which the high-voltage relay  220  is turned on), has the first voltage lower than the second voltage. 
         [0068]    When a time which is taken enough to stabilize the voltage is elapsed, the DC electrical power input to the inverter  230  is consistent with the DC electrical power output through the high-voltage battery  210 . 
         [0069]    In other words, before the voltage is stabilized, the first voltage input to the inverter  230  is lower than the second voltage output through the high-voltage battery  210 , and the first and second voltages are maintained at the same level while the voltage is being stabilized. 
         [0070]    However, when a fault of a contact point is caused due to the fusion of the high-voltage relay  220 , before the voltage is stabilized, the first voltage is equal to the second voltage. 
         [0071]    This signifies that even before the electric vehicle  200  is turned on, due to the fusion of the high-voltage relay  220 , the DC electrical power charged in the high-voltage battery  210  is continuously applied to the inverter  230 . 
         [0072]    Thus, the main control unit  234  diagnoses whether the high-voltage relay  220  is fused based on the time point at which the first voltage is equal to or higher than the second voltage. 
         [0073]    If the time point at which the first voltage is equal to or higher than the second voltage occurs on or after the time point of stabilization, the main control unit  234  determines that the high-voltage relay  220  is normal. 
         [0074]    However, if the time point at which the first voltage is equal to or higher than the second voltage occurs before the time point of stabilization, the main control unit  234  determines that the high-voltage relay  220  is fused so that necessary measures may be followed according to the determination result. 
         [0075]    That is, when the main control unit  234  determines that the high-voltage relay  220  is normal, the main control unit  234  outputs a control signal to the motor control output unit  235  such that a driving electrical power is provided to the motor  240 . 
         [0076]    However, when the main control unit  234  determines that the high-voltage relay  220  is fused, the main control unit  234  allows the motor  240  to be stopped (the electrical power supplied to the motor is blocked) and then, stores the diagnosis information about the fusion of the high-voltage relay  220 . 
         [0077]    Further, the main control unit  234  displays the information about necessary measures against the fusion of the high-voltage relay  220  on the display  236 . Thus, the display  236  informs a driver of the information provided from the main control unit  234  about the fusion of the high-voltage relay  220 . The display  236  may be provided on a cluster. 
         [0078]      FIG. 4  is a graph illustrating a voltage variation in a normal operation according to the embodiment. 
         [0079]    Referring to  FIG. 4 , the first voltage (DC link voltage) input to the inverter  230  is gradually increased from the time point at which the electric vehicle is turned on at the state that the high-voltage relay  220  is normally operated. 
         [0080]    That is, as time elapses from the first time point  1 T to the seventh time point  7 T, the first voltage is gradually increased. In this case, the first voltage is gradually increased in the lower range than the second voltage (battery voltage). 
         [0081]    Then, when it reaches the time point of the voltage stabilization as time elapses, the first voltage may be equal to the second voltage. 
         [0082]      FIG. 5  is a graph illustrating a voltage variation in an abnormal operation according to the embodiment. 
         [0083]    Referring to  FIG. 5 , the first voltage (DC link voltage) input to the inverter  230  is abruptly increased from the time point at which the electric vehicle is turned on at the state that the high-voltage relay  220  is abnormally operated. This signifies that the DC electrical power is continuously supplied to the inverter  230  even before the electrical vehicle  200  is started. 
         [0084]    As time elapses, the first voltage arrives at the same level as that of the second voltage in advance of the time point at which the voltage is stabilized. 
         [0085]    That is, the voltage output from the inverter  230  has the same level as that of the voltage supplied from the high-voltage battery  210  before the voltage is stabilized. 
         [0086]    Thus, in the embodiment, based on the time points that the first voltage is equal to or higher than the second voltage and the voltage is stabilized, it is diagnosed whether the high-voltage relay  220  is fused and according to the diagnosis result, the driving voltage is selectively supplied to the motor  240 . 
         [0087]    According to the embodiment, it is diagnosed whether the high-voltage relay installed on the power line of the electric vehicle is fused and the diagnosis result is indicated to the driver, so that a rapid repair or exchange can be performed before driving the vehicle, thereby improving stability and reliability. 
         [0088]    According to the embodiment, the inverter may diagnose the fusion of a relay without interworking with other electric components so that a user may take necessary measures against a dangerous situation based on the fusion state of the relay. 
         [0089]    Further, according to the embodiment, when the electric vehicle is ignited, it is diagnosed whether the relay is fused, so that the electric vehicle can be prevented from being driven at the fusion state of the electric vehicle. 
         [0090]      FIG. 6  is a flowchart illustrating a method of diagnosing a relay contact step by step according to the embodiment. 
         [0091]    In step S 601 , the electric vehicle  200  is in the ignition-on state. At this time point, the electric vehicle is turned on by a driver. 
         [0092]    Then, in the step S 602 , the main control unit  234  measures the DC link voltage (first voltage) input to the inverter  230  according to the DC electrical power output through the high-voltage battery  210  at the time point at which the electric vehicle  200  is turned on. 
         [0093]    In step S 603 , when the first voltage is measured, the main control unit  234  compares the first voltage with the second voltage output through the high-voltage battery  210  to determine whether the first voltage is equal to or higher than the second voltage. That is, the main control unit  234  determines whether the first voltage is equal to or higher than the second voltage. 
         [0094]    As a determination result in step S 603 , when the first voltage is lower than the second voltage, the main control unit  234  determines in step S 604  that a current time point is before a time point at which the voltage is stabilized. In other words, when the first voltage is lower than the second voltage, the main control unit  234  is on standby for a predetermined time. Then, after the predetermined time ΔT elapses, the main control unit  234  returns to step S 602  such that the first voltage is measured again. 
         [0095]    Meanwhile, as the determination result in step S 603 , when the first voltage is equal to or higher than the second voltage, the main control unit  234  identifies the time point at which the first voltage is measured in step S 605 . In other words, when the first voltage is equal to or higher than the second voltage, the main control unit  234  identifies an elapsed time from the ignition-on time point to the current time point. 
         [0096]    In step S 606 , the main control unit  234  determines whether the measured time point is on or before the time point of the predetermined voltage stabilization. That is, the main control unit  234  determines whether the time point at which the first voltage is equal to or higher than the second voltage occurs on or before the time point of the stabilization. 
         [0097]    In step S 607 , when the first voltage reaches the same level as or higher than that of the second voltage after the stabilization time point, the main control unit  234  determines that the high-voltage relay  220  is normal. 
         [0098]    However, in step S 608 , when the first voltage is increased at the same level as or higher than that of the second voltage before the stabilization time point, the main control unit  234  determines that the high-voltage relay  220  is fused. 
         [0099]    In step S 609 , the main control unit  234  stores diagnosis information about the fusion of the high-voltage relay  220  in the memory  233 . 
         [0100]    In step S 610 , the main control unit  234  allows the information about the result of diagnosing the high-voltage relay  220  to be displayed. 
         [0101]    According to the embodiment, it is diagnosed whether the high-voltage relay installed on the power line of the electric vehicle is fused and the diagnosis result is indicated to the driver, so that a rapid repair or exchange can be performed before driving the vehicle, thereby improving stability and reliability. 
         [0102]    According to the embodiment, the inverter may diagnose the fusion of a relay without interworking with other electric components so that a user may take necessary measures against a dangerous situation based on the fusion state of the relay. 
         [0103]    Further, according to the embodiment, it is diagnosed upon the ignition-on state of the electric vehicle whether the relay is fused, so that the electric vehicle can be prevented from being driven at the fusion state of the electric vehicle. 
         [0104]    The above image processing method according to the embodiment may be prepared as a program for executing the method in the computer to be stored in the computer-readable recording medium and examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage, and the like and in addition, include a type of a carrier wave (e.g., transmission through the Internet). 
         [0105]    The computer-readable recording media are distributed on computer systems connected through the network, and thus the computer-readable recording media may be stored and executed as the computer-readable code by a distribution scheme. In addition, functional programs, codes, and code segments for implementing the method can be easily deduced by programmer skilled in the art. 
         [0106]    Further, as described above, although various examples have been illustrated and described, the present disclosure is not limited to the above-mentioned examples and various modifications can be made by those skilled in the art without departing from the scope of the appended claims. In addition, these modified examples should not be appreciated separately from technical spirits or prospects.