Patent Publication Number: US-8983695-B2

Title: Electric vehicle and method for controlling same

Description:
TECHNICAL FIELD 
     The present invention relates to an electric vehicle and a method for controlling the same, and more particularly to an electric vehicle which determines the presence or absence of a malfunction in a memory region storing data therein using a plurality of controllers or detects the presence or absence of an operation error of the controllers so as to control vehicle traveling on the basis of the determined result, detects an error encountered in a motor control unit (MCU) using a main controller (vehicle control module: VCM), controls vehicle traveling by detecting a vehicle state, calculates torque values encountered in different memory regions of the MCU, and controls vehicle traveling, and to a method for controlling the same. 
     BACKGROUND ART 
     Electric vehicles (EVs) have been actively studied because they are the most promising solution to pollution and energy problems. 
     Electric vehicles (EVs) are mainly powered by an AC or DC motor using power of a battery. The electric vehicles are broadly classified into battery powered electric vehicles and hybrid electric vehicles. In the battery powered electric vehicles, a motor is driven using power of a battery, and the battery is recharged after stored power is consumed. In hybrid electric vehicles, a battery is charged with electricity generated via engine driving, and an electric motor is driven using the electricity to realize vehicle movement. 
     The hybrid electric vehicles may further be classified into serial and parallel types. In the case of serial hybrid electric vehicles, mechanical energy output from an engine is changed into electric energy via a generator, and the electric energy is fed to a battery or motor. Thus, the serial hybrid electric vehicles are always driven by a motor similar to conventional electric vehicles, but an engine and generator are added for the purpose of increasing range. Parallel hybrid electric vehicles may be driven using two power sources, i.e. a battery and an engine (gasoline or diesel). Also, the parallel hybrid electric vehicles may be driven using both the engine and the motor according to traveling conditions. 
     With recent gradual development of motor/control technologies, small high-output and high-efficiency systems have been developed. Owing to replacing a DC motor by an AC motor, electric vehicles have accomplished considerably enhanced output and power performance (acceleration performance and maximum speed) comparable to those of gasoline vehicles. As a result of promoting a higher output and higher revolutions per minute, a motor has achieved reduction in weight and size, and consequently reduction in the weight and size of a vehicle provided with the motor. 
     The electric vehicle includes a central controller for controlling a variety of functions. Assuming that only one controller is used, it is very difficult to detect abnormality of a non-volatile memory and abnormality of torque operation. In addition, assuming that abnormality or malfunction occurs in the MCU configured to control a motor upon receiving a command from the central controller, the motor may be wrongly driven in a different way from the command generated by the controller. 
     DISCLOSURE 
     Technical Problem 
     Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide an electric vehicle including a plurality of controllers and a motor control unit (MCU), which can allow the plurality of controllers to control vehicle traveling by monitoring data of a non-volatile memory and calculated torque values, can control vehicle traveling by monitoring torque values calculated by the controllers and the MCU, or can also control vehicle traveling by monitoring torque values calculated in a plurality of memory regions of the MCU, and a method for controlling the same. 
     It will be appreciated by persons skilled in the art that the objects that can be achieved through the present invention are not limited to what has been particularly described hereinabove and the above and other objects that the present invention can achieve will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. 
     Technical Solution 
     In accordance with one aspect of the present invention, the above and other objects can be accomplished by a method for controlling an electric vehicle including: calculating a first torque value using first data by a first memory; calculating a second torque value using second data by a second memory having a memory address different from that of the first memory; and determining the presence or absence of abnormality in torque calculation by comparing the first torque value with the second torque value. 
     In accordance with another aspect of the present invention, an electric vehicle includes: a motor control unit (MCU) for calculating a torque value upon receiving an input value for torque calculation; and a motor for generating torque corresponding to a torque value calculated by the motor control unit (MCU), wherein the motor control unit (MCU) includes: a first memory having a specific memory address; and a second memory having a specific memory address different from that of the first memory, whereby the motor control unit (MCU) receives the input value and calculates a first torque value at the first memory and a second torque value at the second memory, and the motor generates torque using the first torque value or the second torque value as a final torque value when the first torque value is identical to the second torque value. 
     In accordance with another aspect of the present invention, an electric vehicle includes: a vehicle control module (VCM) for generating a torque command to control vehicle driving; and a motor control unit (MCU) for calculating a first torque value in response to the torque command and controlling a motor on the basis of the calculated first torque value, and feeding back raw data regarding the first and second torque values to the vehicle control module (VCM), wherein the vehicle control module (VCM) calculates a second torque value using the raw data, and determines a current vehicle state by comparing the torque command with the first and second torque values. 
     In accordance with another aspect of the present invention, an electric vehicle includes: a first memory for storing data; a second memory for storing data; a first controller for storing data of the vehicle in the first memory, determining the presence or absence of abnormality in the data stored in the first memory and the second memory, and calculating a first torque value for controlling the vehicle; and a second controller for storing data of the vehicle in the second memory independently from the first controller, determining the presence or absence of abnormality in the data stored in the first memory and the second memory, and calculating a second torque value for controlling the vehicle, wherein the first controller and the second controller compare the first torque value with the second torque value to determine the presence or absence of abnormality in torque calculation, and control vehicle driving according to the presence or absence of abnormal torque calculation or abnormal data. 
     Advantageous Effects 
     In accordance with the embodiments of the present invention, an electric vehicle and a method for controlling the same have the following advantages. The electric vehicle includes a plurality of controllers to monitor a non-volatile memory, determines the presence or absence of abnormal data in a non-volatile memory while simultaneously correcting the abnormal data, and performs mutual monitoring of torque values calculated by a plurality of controllers, such that it can control torque values using one or more controllers having no errors. 
     The electric vehicle monitors torque values calculated by the controller and the motor control unit (MCU), such that unexpected problems such as erroneous operation of the MCU occur. As a result, although unexpected errors occur in torque values actually applied to the motor whereas the calculated torque value is correctly output, the electric vehicle can recognize the errors. 
     The electric vehicle monitors torque values calculated in different memory regions of the motor control unit (MCU), such that it can recognize calculation errors of torque values of the MCU. 
     As a result, reliability of torque values of the motor can be increased, such that the electric vehicle properly copes with unexpected situations such as sudden unintended acceleration by preventing sudden change of torque, and prevents sudden stop of the running vehicle or a control disabled state thereof, resulting in a guarantee of the safety of the electric vehicle. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. 
         FIG. 1  is a block diagram illustrating constituent components of an electric vehicle according to an embodiment of the present invention. 
         FIG. 2  is a block diagram illustrating constituent components of an electric vehicle according to an embodiment of the present invention. 
         FIG. 3  is a diagram illustrating a motor control unit (MCU) of the electric vehicle according to an embodiment of the present invention. 
         FIG. 4  is a conceptual diagram illustrating a vehicle control method for monitoring the electric vehicle according to an embodiment of the present invention. 
         FIG. 5  is a conceptual diagram illustrating mutual monitoring using a plurality of controllers according to an embodiment of the present invention. 
         FIG. 6  is a conceptual diagram illustrating a method for controlling the electric vehicle through mutual monitoring of the first controller and the second controller according to an embodiment of the present invention. 
         FIG. 7  is a flowchart illustrating a method for controlling the electric vehicle according to an embodiment of the present invention. 
         FIG. 8  is a flowchart illustrating a method for controlling the electric vehicle according to an embodiment of the present invention. 
         FIG. 9  is a flowchart illustrating a method for controlling vehicle traveling on the basis of a state of the electric vehicle according to an embodiment of the present invention. 
         FIG. 10  is a flowchart illustrating a method for controlling the electric vehicle according to an embodiment of the present invention. 
     
    
    
     BEST MODE 
     Advantages and features of the present invention and a method of achieving the advantages and features of the present invention will be clearly understood from embodiments described hereinafter in conjunction with the accompanying drawings. However, the present invention is not limited to the following embodiments and may be realized in various different forms. These embodiments are provided only to completely disclose the present invention and for a person having ordinary skill in the art to which the present invention pertains to completely understand the category of the invention. That is, the present invention is defined only by the category of the claims. The same reference numbers will be used throughout this specification to refer to the same parts. 
     Embodiments of the present invention will be described below with reference to the attached drawings. The electric vehicle and a method for controlling the same according to embodiments of the present invention will hereinafter be described with reference to the attached drawings. 
       FIG. 1  is a block diagram illustrating constituent components of an electric vehicle according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the electric vehicle includes a vehicle control module (VCM)  110 , a motor control unit (MCU)  120 , a motor  130 , a sensor unit  140 , a power relay assembly (PRA)  150 , a battery  160 , a battery management system  170 , and an interface unit  180 . 
     The electric vehicle includes the battery  160 , operates using power charged in the battery  160 , and charges the battery  160  upon receiving power from a charging station, a vehicle charging installation, a home or an external part. 
     The battery  160  includes a plurality of high-voltage battery cells. In this case, the electric vehicle further includes a battery management system (BMS)  170 . The BMS  170  controls a charging operation of the battery  160 , determines the remaining battery capacity and the presence or absence of charging necessity, and performs a management operation for providing the charging current stored in the battery  160  to each part of the electric vehicle. 
     When charging and using the battery, the BMS  170  maintains a regular voltage difference between cells of the battery  160 , and controls the battery not to be overcharged or overdischarged, resulting in increased battery lifespan. 
     The BMS  170  measures the remaining battery lifespan of the battery  160  and a voltage of the battery  160 , and outputs the measured result to the VCM  110 . 
     A Power Relay Assembly (PRA)  150  includes a plurality of relays and a sensor to perform switching of a high voltage, so that it receives an operating power of a high voltage from the battery  160 , and applies the received power to the MCU  120  or prevents the received power from being applied to the MCU  120 . In this case, the PRA  150  operates the relays upon receiving a control command from the VCM  110 . 
     When the vehicle starts or stops driving, the PRA  150  switches a plurality of relays according to a predetermined order upon receiving a control command from the VCM  110 , such that the operating power of a high voltage stored in the battery  160  can be applied to individual parts of the vehicle. 
     The PRA  150  prevents battery power from being applied to the MCU  120 , and also prevents power from being applied to the motor  130 , such that the motor  130  stops operation and thus the vehicle also stops driving. 
     The MCU  120  generates a control signal for driving at least one motor  130  connected thereto, generates a predetermined signal for controlling the motor  130 , and applies the generated signal to the motor  130 . In this case, the MCU  120  includes an inverter (not shown) and a converter (not shown), so that it can control the motor  130  by controlling the inverter or converter. 
     The MCU  120  calculates a torque value on the basis of various input values, and the motor  130  generates a torque on the basis of the calculated torque value. 
     The MCU  130  calculates a torque value upon receiving a torque command from the MCU  110 , and drives the motor  130  in response to a torque command using battery power received through the PRA  150 . 
     The VCM  110  controls vehicle traveling and overall operations of the electric vehicle. The VCM  110  generates and outputs a predetermined command to the MCU  120  in such a manner that predetermined operations corresponding to input data of the interface unit  180  and the sensor unit  140  are carried out, such that input/output (I/O) of data is controlled. 
     The VCM  110  outputs a torque command for driving the motor  130  to the MCU  120 , and monitors the presence or absence of an operation error in the MCU  120 . 
     The sensor unit  140  detects signals generated when the vehicle runs or performs a predetermined operation, and inputs the detected signals to the VCM  110 . The sensor unit  140  includes a plurality of sensors inside or outside of the vehicle so that it can detect a variety of signals. In this case, different types of sensors may be used according to installation positions. The sensor unit  140  includes a wheel sensor for sensing a wheel speed to calculate a torque value, and a slope sensor for sensing a slope of the vehicle. 
     The sensor unit  140  includes a plurality of sensors, and measures an input current of the motor  130  and a rotor angle of the motor  130 , such that it can transmit the measured values to the MCU  120 . 
     The interface unit  180  includes an input unit configured to input a predetermined signal by a vehicle driver&#39;s manipulation, and an output unit for outputting current operation state information of the electric vehicle. 
     The input unit may include manipulators such as a steering wheel, an accelerator, a brake, etc. The accelerator outputs acceleration information for calculating a torque value, and the brake outputs brake information for calculating a torque value. 
     The input unit includes a plurality of switches and a plurality of buttons to operate a turn signal, a tail lamp, a head lamp, brushes, etc. 
     The output unit includes a display for displaying information, a speaker for outputting music, sound effects, and warning sounds, and various state indicator lamps, etc. 
       FIG. 2  is a block diagram illustrating constituent components of an electric vehicle according to an embodiment of the present invention. 
     Referring to  FIG. 2 , the electric vehicle includes a first controller  210 , a second controller  220 , a first memory  215 , a second memory  225 , a motor control unit (MCU)  230 , a motor  240 , a power relay assembly (PRA)  250 , a battery  260 , a battery management system (BMS)  270 , and a sensor unit  280 . Compared to the electric vehicle of  FIG. 1 , the electric vehicle shown in  FIG. 2  includes a plurality of vehicle control modules (VCMs). 
     The same elements as those of  FIG. 1 , i.e., the motor  240 , the PRA  250 , the battery  260 , and the BMS  270 , will herein be omitted for convenience of description and better understanding of the present invention. 
     Each of the first memory  215  and the second memory  225  stores data of the electric vehicle. Data of the first memory  215  is identical to that of the second memory  225 . However, assuming that error or noise occurs in a signal transmission step, the first memory  215  and the second memory  225  may have different data. Each of the first memory  215  and the second memory  225  is any of non-volatile memories, for example, ROM, hard disc, flash memory, EEPROM, etc. 
     The first controller  210  stores data related to vehicle traveling in the first memory  215 . Data related to vehicle travelling is stored in the second memory  225  independently from the first controller  210 . The first controller  210  determines the presence or absence of a malfunction in data stored in a non-volatile memory. If a malfunction occurs in the stored data, the first controller  210  corrects abnormal data, and calculates a first torque value using data stored in the first memory  215 . 
     The second controller  220  determines the presence or absence of a malfunction in data stored in the first memory  215  and the second memory  225 . If a malfunction occurs in the stored data, the second controller corrects abnormal data, and calculates a second torque value using data stored in the second memory  225 . 
     The first controller  210  compares a first torque value with a second torque value received from the second controller  220 , determines the presence or absence of a malfunction in the torque value, and transmits a control command to the MCU  230 , the PRA  250 , and the BMS  270  so as to control vehicle traveling. 
     The second controller  220  compares a second torque value with a first torque value received from the first controller  210 , determines the presence or absence of a malfunction in the torque value, and transmits a control command to the MCU  230 , the PRA  250 , and the BMS  270  so as to control vehicle traveling. 
     The MCU  230  is operated in response to a control command from either the first controller  210  or the second controller  220 . 
     The sensor unit  280  detects signals generated when the vehicle runs or performs a predetermined operation, and inputs the detected signals to the first controller  210  and the second controller  220 . The sensor unit  280  includes a plurality of sensors inside or outside of the vehicle so that it can detect a variety of signals. In this case, different types of sensors may be used according to installation positions. 
     The sensor unit  280  may include an accelerator position sensor (APS), a brake position sensor (BPS), a vehicle speed sensor, etc. The APS is a sensor indicating an acceleration state, and the BPS is a sensor indicating the degree of stepped-on brake. The vehicle speed sensor is a sensor for measuring the speed of vehicle 
       FIG. 3  is a diagram illustrating a motor control unit (MCU) of the electric vehicle according to an embodiment of the present invention. 
     Referring to  FIG. 3 , the MCU  120  of the electric vehicle includes a first memory  121  for calculating a first torque value, a second memory  122  for calculating a second torque value, and a comparator  124  for determining whether the first torque value is identical to the second torque value. 
     The first memory  121  and the second memory  122  are used as memory regions having different memory addresses. The first memory  121  and the second memory  122  calculate a first torque value and a second torque value using the same input values and the same logic units at the same time. Torque values of the first memory  121  and the second memory  122  may be simultaneously calculated by performance of the processor, or may be calculated at intervals of a predetermined time. Although torque values of the first memory  121  and the second memory  122  are calculated at intervals of a predetermined time, the first memory  121  and the second memory  122  are calculated using the same input values at the same time. 
     Input values needed for calculating torque values in the first memory  121  and the second memory  122  may be acceleration information of an accelerator of the interface unit  180 , braking information, and a wheel speed sensed by the wheel sensor of the sensor unit  140 . In addition, the input values may further include the remaining battery lifespan and the battery voltage measured by the BMS  170 , a vehicle slope detected by the slope sensor of the sensor unit  140 , and a torque control value for performing an economy (ECO) mode or an electronic stability control (ESC). 
     The comparator  123  compares a first torque value obtained from the first memory  121  with a second torque value obtained from the second memory  122 . If the first and second torque values are identical to each other, the comparator  123  outputs the final torque value. If the first and second torque values are different from each other, the comparator  123  outputs a signal indicating a calculation error. 
     If the comparator  123  outputs a torque value, the PRA  150  and the motor  130  are controlled in a manner that the motor  130  can output the final torque value. If the comparator  123  outputs the calculation error signal, the output unit of the interface unit  180  outputs the calculation error signal to the outside, and the motor  130  does not generate the first torque value and the second torque value. 
       FIG. 4  is a conceptual diagram illustrating a vehicle control method for monitoring the electric vehicle according to an embodiment of the present invention. 
     Referring to  FIG. 4 , the VCM  110  outputs a torque command for driving the motor  130  to the MCU  120 . In response to the torque command, the MCU  130  feeds back not only the first torque value calculated on the basis of the torque command but also raw data related to the first torque value to the VCM  110 . 
     The raw data may include a U-phase current value, a V-phase current value, and a W-phase current value to be input to the motor  130 . The raw data may further include a torque ID, a rotor angle of the motor  130 , a rated torque of the motor  130 , and a current at the rated torque of the motor  130 . 
     The VCM  110  calculates a second torque value using the raw data, such that the MCU  120  can monitor whether a torque value actually applied to the motor  130  has a malfunction in response to the torque command. 
     The VCM  110  performs comparison among the torque command applied to the MCU  120 , the first torque value received from the MCU  120 , and the second torque value calculated using the raw data, such that it recognizes a vehicle state and controls vehicle traveling. 
       FIG. 5  is a conceptual diagram illustrating mutual monitoring using a plurality of controllers according to an embodiment of the present invention. 
     Referring to  FIG. 5 , the first controller  210  determines the presence or absence of an error in data stored in the first memory  215  and the second memory  225 . If the error occurs in the stored data, the first controller  210  corrects abnormal data. 
     The second controller  220  determines the presence or absence of an error in data stored in the first memory  215  and the second memory  225 . If the error occurs in the stored data, the second controller  220  corrects abnormal data. 
     The first controller  210  transmits data stored in the first memory  215  to the second memory  225 , and the second controller  220  transmits data stored in the second memory  225  to the first memory  215 . 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                 Equal to or different 
                 Normal or 
               
               
                   
                   
                 Data of  
                 from Predefined 
                 abnormal 
               
               
                   
                 Address 
                 Memory 
                 checksum 
                 state 
               
               
                   
                   
               
             
            
               
                   
                 1 
                 Data1 
                 Agreement 
                 Normal 
               
               
                   
                 2 
                 Data2 
                 Agreement 
                 Normal 
               
               
                   
                 3 
                 Data3 
                 Disagreement 
                 Normal 
               
               
                   
                 4 
                 Data4 
                 Agreement 
                 Normal 
               
               
                   
                 . . . 
                 . . . 
                 . . . 
                 . . . 
               
               
                   
                   
               
            
           
         
       
     
     Table 1 shows a process for allowing a plurality of controllers to determine whether a malfunction or error occurs in data stored in a plurality of memories. 
     Referring to Table 1, if a checksum value prestored in the first controller  210  is identical to a checksum value calculated using the data stored in the first memory  215 , the first controller  210  determines a normal state. If the two checksum values are different from each other, the first controller  210  determines an abnormal state. If the abnormal state has occurred, abnormal data can be corrected using previous data and the next data of the abnormal data. 
     In this case, a linear interpolation method may be used as a data correction method. The abnormal data can be corrected using an average value of the previous data and the next data of the abnormal data. 
     The first controller  210  receives data stored in the second memory  225  from the second controller  220 , and determines whether a malfunction (or abnormality) occurs in data stored in the second memory  225  using the same method as described above. If a malfunction occurs in data stored in the second memory  225 , the first controller  210  can correct the abnormal data. 
     After the second controller  220  receives data stored in the first memory  215  from the first controller  210 , and receives data stored in the second memory  225 , it determines whether abnormality occurs in the data stored in the first memory  215 . If the abnormality occurs in the stored data, the second controller  220  can correct the abnormal data. 
     The first controller  210  and the second controller  220  detects how many times such abnormality occurs in the first memory  215  and the second memory  225 , and store the detected number of times. 
       FIG. 6  is a conceptual diagram illustrating a method for controlling the electric vehicle through mutual monitoring of the first controller  210  and the second controller  220  according to an embodiment of the present invention. 
     Referring to  FIG. 6 , the electric vehicle receives information needed for vehicle control from the sensor unit  140 , and the first controller  210  stores the received information in the first memory  215 , and the second controller  220  stores the received information in the second memory  225 . Input data from the sensor unit  270  may include an accelerator, a brake, a vehicle speed, etc. 
     The first controller  270  calculates a first torque value using data stored in the first memory  215 , and the second controller  220  calculates a second torque using data stored in the second memory  225 . 
     The first controller  210  and the second controller  220  perform mutual transmission of the first torque value and the second torque value, compare a checksum of the first torque value with a checksum of the second torque value for a predetermined time so as to determine the presence or absence of abnormality or malfunction in torque values, and performs torque control according to the comparison result. If abnormality occurs in torque values, the electric vehicle runs with limited torque values not exceeding a predetermined value. 
       FIG. 7  is a flowchart illustrating a method for controlling the electric vehicle according to an embodiment of the present invention. 
     Referring to  FIG. 7 , a variety of input values for torque calculation (for example, acceleration information, braking information, a wheel speed, etc.) are input to the MCU  120  in step S 310 . Acceleration information of the accelerator and braking information of the brake are input to the MCU through the interface unit  180 , and a wheel speed detected by the wheel sensor is transmitted from the VCM  110  to the MCU  120 . In addition, the remaining battery charge and the battery voltage measured by the BMS  180 , a vehicle slope detected by the slope sensor of the sensor unit  140 , and a torque control value for activating an economy (ECO) mode or an electronic stability control (ESC) may be transmitted from the VCM  110  to the MCU  120 . 
     The MCU  120  calculates the first torque value for the first memory  121  using input values in step S 320 . In more detail, the MCU  120  calculates a first torque value for use in the first memory  121  having a specific memory address using input values such as acceleration information, brake information, wheel speed, etc. 
     The MCU  120  calculates the second torque value for use in the second memory  122  using input values in step S 330 . The MCU  120  calculates a second torque value for use in the second memory  122  having a specific memory address using input values such as acceleration information, brake information, wheel speed, etc. 
     The second torque value is calculated using the same input values and the same logic units at the same time as that of the first torque value. Step S 320  and Step S 330  can be performed at the same time or different times. If Step S 320  and Step S 330  are performed at different times, they are performed using the same input values obtained from the same time. 
     The comparator  123  compares the first torque value is identical with the second torque value in step S 340 , such that it can determine whether the first torque value calculated by the first memory  121  is identical to the second torque value calculated by the second memory  122 . 
     If the first torque value is identical to the second torque value, the comparator  125  outputs the final torque value in step S 350 . The comparator outputs the final torque value (i.e., the first and second torque values identical to each other) to the VCM  110 , the motor  130  or the PRA  150 . 
     The PRA  150  and/or the motor  130  are controlled in a manner that the motor  130  can generate the final torque value in step S 360 . The PRA  150  controls the operating power of a high voltage supplied from the battery  160  in such a manner that the motor  130  can generate the final torque value, and provides the resultant operating power to the MCU  120  or cuts off the same. 
     If the first torque value is different from the second torque value, the comparator  123  outputs a calculation error signal in step S 370 . The comparator  123  outputs the calculation error signal to the MCU  110  when the first torque is different from the second torque value, such that the output unit of the interface unit  180  outputs the calculation error signal to the outside and the motor  130  does not generate a torque based on the calculated first and second torque values. 
       FIG. 8  is a flowchart illustrating a method for controlling the electric vehicle according to an embodiment of the present invention. 
     Referring to  FIG. 8 , the VCM  110  generates a torque value to control vehicle traveling on the basis of input signals, and outputs the torque command to the MCU  120 . In this case, the MCU  120  calculates the first torque value upon receiving the torque command from the MCU  110 , and controls the motor  130  in step S 410 . 
     The MCU  120  feeds back not only the calculated first torque value but also raw data related to the first torque value to the MCU  110  in step S 420 . 
     The VCM  110  calculates a second torque value upon receiving the raw data from the MCU  120  in step S 430 . 
     The second torque value can be calculated using the following equation 1. 
     
       
         
           
             
               
                 
                   
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     In Equation 1, i u  is a U-phase current value applied to the motor  130 , i v  is a V-phase current value applied to the motor  130 , i w  is a W-phase current value applied to the motor  130 , and θ is a rotor angle. 
     The calculation resultant values derived from Equation 1 include a current (i des ) of a d-axis rotation coordinate system and a current (i qse ) of a q-axis rotation coordinate system. 
     
       
         
           
             
               
                 
                   
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                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     In Equation 2, i qse  is a q-axis rotation coordinate system current calculated by Equation 1, T rate  is the rated torque of the motor  130 , and i rate  is a current at the rated torque. 
     T vcm-cal  is a second torque value calculated by the VCM  110 . 
     The VCM  110  performs comparison among the torque command, the first torque value received from the MCU  120 , and the second torque value calculated using raw data, and analyzes the comparison result in step S 440 . 
     When the VCM  110  compares the torque command sent therefrom with a second torque value calculated using raw data, there is a delay time between the transmission time and the reception time, such that it is impossible for the VCM  110  to perform correct comparison. In order to solve the above problem, the VCM  110  assigns a torque ID to the torque command, and transmits the resultant torque command. In addition, when the MCU  110  feeds back the raw data to the MCU, the MCU  110  assigns the same torque ID as a torque ID assigned to the torque command to the raw data, and feeds back the resultant raw data. The MCU  110  compares the torque command with the second torque value calculated using raw data to which the same torque ID is allocated, such that there is no time delay between the transmission time and the reception time and the MCU  110  can perform correct comparison without any time delay. 
     It is determined whether the MCU  120  operates within the normal range in step S 450 . 
     If the MCU  120  is in a normal state, the MCU  120  normally operates without limitation in output and torque in step S 460 . Unless the MCU  120  is in the normal state, the electric vehicle does not stop and is driven within the limited range of the output and torque of the motor  130  in step S 470 . In this case, the limited range may have the output range of 35 kW˜45 kW and the torque range of 110 Nm˜120 Nm. 
       FIG. 9  is a flowchart illustrating a method for controlling vehicle traveling on the basis of a state of the electric vehicle according to an embodiment of the present invention. 
     Referring to  FIG. 9 , the VCM  110  calculates a difference between a torque command and a first torque value, and a difference between a torque command and a second torque value in step S 510 . 
     The VCM  110  determines whether each of the difference between the torque command and the first torque value and the difference between the torque command and the second torque value is higher than a first reference value in step S 520 . 
     In this case, the first reference value may be established within the range of 55 Nm˜65 Nm. 
     If at least one of the difference between the torque command and the first torque value and the difference between the torque command and the second torque value is not higher than the first reference value, the VCM  110  determines a normal state of the MCU  120  and controls the motor  130  to normally operate without limitation in output and torque of the motor  130  in step S 530 . 
     If each of the difference between the torque command and the first torque value and the difference between the torque command and the second torque value is higher than the first reference value, the VCM  110  determines whether at least one of the difference between the torque command and the first torque value and the difference between the torque command and the second torque value is higher than the second reference value higher than the first reference value in step S 540 . 
     Preferably, the second reference value may be established within the range of 110 Nm˜120 Nm. 
     If each of the difference between the torque command and the first torque value and the difference between the torque command and the second torque value is not higher than the second reference value, the VCM  110  does not stop the electric vehicle and controls the electric vehicle to operate within the limited range of the output and torque of the motor  130  in step S 550 . 
     As described above, the limited range may have the output range of 35 kW˜45 kW and the torque range of 110 Nm˜120 Nm. 
     If at least one of the difference between the torque command and the first torque value and the difference between the torque command and the second torque value is higher than a second reference value, the VCM  110  determines whether each of the difference between the torque command and the first torque value and the difference between the torque command and the second torque value is higher than a second reference value in step S 560 . 
     If any one of the difference between the torque command and the first torque value and the difference between the torque command and the second torque value is not higher than the second reference value, the VCM  110  determines whether the output current of the battery  160  is higher than a predetermined limit value in step S 570 . In this case, if the output current of the battery  160  is not higher than the limit value, the VCM  110  does not stop the electric vehicle and establishes the limited output and torque values of the motor  130 , such that it controls the electric vehicle to be driven within the limited range in step S 550 . In this case, if the output current of the battery  160  is higher than the limit value, the VCM  110  transmits a stop command to the MCU  120  and cuts off power supplied from the battery  160  to the MCU  120  in step S 580 . 
     In this case, the limited output current of the battery  160  may be established within the range of 125 A˜135 A. If the output and torque of the motor  130  are limited, the output current of the battery  160  is generally reduced. Although the output and torque of the motor  130  are limited, if the output current of the battery  160  exceeds the limited output current, the VCM  110  determines the occurrence of abnormality in the MCU  120  and stops the electric vehicle. 
     If each of the difference between the torque command and the first torque value and the difference between the torque command and the second torque value is higher than the second reference value, the VCM  110  transmits a stop command to the MCU  120  and cuts off power supplied from the battery  160  to the MCU  120  in step SS 580 . 
     Therefore, the electric vehicle and a method for controlling the same according to embodiments of the present invention, under the condition that unexpected problems such as internal calculation errors of the MCU occur so that the first torque value is correctly output but there arises abnormality in the torque value actually applied to the motor, compares the second torque value calculated by the VCM with the torque command on the basis of the raw data actually applied to the motor, such that the presence or absence of abnormality in the MCU is determined and vehicle traveling can be controlled according to the determined result. 
       FIG. 10  is a flowchart illustrating a method for controlling the electric vehicle according to an embodiment of the present invention. 
     Referring to  FIG. 10 , the first controller  210  reads data stored in the first memory  215 , and the second controller  220  reads data stored in the second memory  225 . The first controller  210  and the second controller  220  perform mutual transmission of the read data in step S 610 . 
     The first controller  210  calculates a checksum of data stored in the first memory  215  using data read from the first memory  215 , and calculates a checksum of data stored in the second memory  225  using the output data of the second controller  220 . Likewise, the second controller  220  calculates a checksum of data stored in the second memory  225  using data read from the second memory  225 , and calculates a checksum of data stored in the first memory  215  using the output data of the first controller  210  in step S 620 . 
     The first controller  210  compares each of a checksum of data stored in the first memory  215  and a checksum of data stored in the second memory  225  with a checksum prestored in the first controller  210 , and determines whether each checksum is identical to the prestored checksum. 
     The second controller  220  compares each of a checksum of data stored in the first memory  215  and a checksum of data stored in the second memory  225  with a checksum prestored in the second controller  220 , and determines whether each checksum is identical to the prestored checksum in step S 630 . 
     The first controller  210  and the second controller  220  are configured to determine whether abnormality occurs in data stored in the first memory  215  and the second memory  225  on the basis of the above comparison result in step S 640 . 
     If the abnormal data occurs, each of the first controller  210  and the second controller  220  corrects abnormal data, counts the number of occurrences of such abnormal data, outputs at least one of warning sound, a warning lamp and a warning message, and displays an abnormal state in step S 650 . However, the first controller  210  and the second controller  220  display the abnormal state but maintain vehicle driving. 
     In order to correct the abnormal data, the previous or next data of the abnormal data is used for such data correction as described above. The first controller  210  and the second controller  220  may perform such data correction using an average value of the previous and next data of the abnormal data according to the linear interpolation method. 
     In this case, if the number of occurrences of abnormal data is equal to or higher than a predetermined limited number of times, the first controller  210  and the second controller  220  are configured to determine the presence of serious abnormality (or malfunction) in the vehicle, such that the vehicle stops motion. 
     If data stored in the first memory  215  and the second memory  225  is normal or if abnormal data is corrected and the number of occurrences of abnormal data is not higher than a predetermined limited number of times, the first controller  210  calculates a first torque value using data stored in the first memory  215 , and the second controller  220  calculates a second torque value using data stored in the second memory  225  in step S 660 . 
     The first controller  210  transmits the calculated first torque value to the second controller  220 , and the second controller  220  transmits the calculated second torque value to the first controller  210 . 
     The first controller  210  calculates a checksum of the first torque values calculated for a predetermined time, and compares a checksum of the second torque values received from the second controller  220  with a checksum of the first torque values. In addition, the second controller  220  calculates a checksum of the second torque values calculated for a predetermined time, and compares a checksum of the first torque values received from the first controller  210  with a checksum of the second torque values in step S 670 . 
     If a difference between the checksum of the first torque values and the checksum of the second torque values is equal to or higher than a predetermined value, the first controller  210  and the second controller  220  determine the presence of abnormality in torque calculation in step S 680 . 
     If the difference between the checksum of the first torque vales and the checksum of the second torque values is less than the predetermined value, torque calculation of the first and second controllers  210  and  220  is considered normal, such that the first controller  210  transmits a torque command for torque control to the MCU  230 , and controls vehicle driving in step S 690 . If abnormality occurs in torque values, each torque value is limited not to exceed a predetermined value so that the vehicle runs within the range of limited torque values in step S 695 . Then the electric vehicle outputs at least one of a warning sound, a warning lamp and a warning message so as to inform a vehicle driver of the abnormal state. 
     As is apparent from the above description, in accordance with the electric vehicle and the method for controlling the same, the electric vehicle includes a plurality of controllers configured to perform mutual monitoring therebetween, such that it determines the presence or absence of abnormality in torque calculation, resulting in prevention of sudden torque change. In addition, the electric vehicle can recognize whether abnormality occurs in data stored in memories through such monitoring, such that it can correct the abnormal data. As a result, the electric vehicle can be controlled in such a manner that reliability of torque values and stability of the electric vehicle are increased. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.