Abstract:
According to an aspect of the present invention, there is provided an abnormality judgment device including: a change amount calculator configured to calculate a change amount between currently-obtained and previously-obtained steering angles; a storage section configured to store a threshold value; a reference setting section configured to set a reference steering angle; an incrementing section configured to continue gradually incrementing the threshold value after the change amount exceeds the threshold value, for a judgment time; a deviation comparator configured to compare an absolute deviation between the currently-obtained steering angle and the reference steering angle with the threshold value, and to count a counter when the absolute deviation exceeds the threshold value; and a judgment section configured to judge that the steering angle sensor is abnormal when the counter reaches a predetermined value.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority from Japanese Patent Application No. 2011-022101 filed on Feb. 3, 2011, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The present invention relates to an abnormality judgment device capable of diagnosing whether a steering angle sensor for detecting a steering angle is normal and to a vehicle controller equipped with such abnormality judgment device. 
     BACKGROUND 
     For example, JP-2003-042754-A proposes a vehicle controller capable of diagnosing a steering angle sensor. The vehicle controller judges that the steering angle sensor is abnormal when the angular velocity calculated from the output value of the steering angle sensor exceeds an allowable maximum angular velocity. 
     In the above-mentioned vehicle controller, when the calculated angular velocity even once exceeds the allowable maximum angular velocity, the steering angle sensor is judged as abnormal. Hence, the steering angle sensor may be misjudged as abnormal, even when the angular velocity becomes more than the allowable maximum angular velocity temporarily due to noise or the like (even when the angular velocity becomes more than the allowable maximum angular velocity momentarily but then returns to its original value), for example. 
     SUMMARY 
     According to an aspect of the present invention, there is provided an abnormality judgment device having a first diagnosing section configured to perform a first diagnosis for judging whether a steering angle sensor is normal, the first diagnosing section periodically obtaining a steering angle from the steering angle sensor, the first diagnosing section including: a first change amount calculator configured to calculate an absolute difference between a currently-obtained steering angle and a previously-obtained steering angle, as a change amount; a first storage section configured to store a maximum value of the change amount which is calculable by the first change amount calculator when the steering angle sensor is normal, as a normal threshold value; a reference setting section configured to set the previously-obtained steering angle as a reference steering angle when the change amount exceeds the normal threshold value; an incrementing section configured to continue gradually incrementing the normal threshold value after the change amount exceeds the normal threshold value, for a first judgment time; a deviation comparator configured to compare an absolute deviation between the currently-obtained steering angle and the reference steering angle with the gradually-incremented normal threshold value, and to count a first counter when the absolute deviation exceeds the normal threshold value, for the first judgment time; and a first judgment section configured to judge that the steering angle sensor is abnormal when the first counter reaches a predetermined value within the first judgment time. 
     With this configuration, even when the change amount temporarily becomes more than the normal threshold value, if the value of the first counter has not reached the predetermined value, the steering angle sensor is not judged as abnormal. Hence, in the diagnosis for the steering angle sensor, misjudgment can be prevented. In particular, the condition for judging that the steering angle sensor is abnormal becomes stricter as the normal threshold value to be used as a counting condition is made larger gradually by the incrementing section, whereby the possibility of misjudgment can be reduced. When abnormality occurs because the steering angle is maintained, fixed or offset to an abnormally high value, the value of the first counter reaches the predetermined value, whereby the abnormality can be judged securely. 
     The incrementing section may continue adding a constant value to the normal threshold value each time the deviation comparator performs a comparison so that the normal threshold value becomes proportional to the number of comparisons. 
     With this configuration, the normal threshold value can be determined by simple increment, whereby it is not necessary to prepare complicated calculating formulas and complicated maps. 
     After a passage of the first judgment time, the first judgment section may judge whether the change amount is kept below the normal threshold value for a first preparatory judgment time, and may reset the first counter when the change amount is kept below the normal threshold value for the first preparatory judgment time. 
     With this configuration, even after the first preparatory judgment time has passed, the value of the first counter is not reset but maintained until the first preparatory judgment time passes. Hence, even when the change amount and the deviation return to their normal values temporarily and the steering angle sensor is not judged as abnormal, when the change amount becomes more than the normal threshold value again during the first preparatory judgment time, the abnormality can be judged easily. 
     According to another aspect of the present invention, there is provided an abnormality judgment device having a second diagnosing section configured to perform a second diagnosis for judging whether a steering angle sensor is normal, the second diagnosing section periodically obtaining a steering angle from the steering angle sensor, the second diagnosing section including: a second change amount calculator configured to calculate an absolute difference between a currently-obtained steering angle and a previously-obtained steering angle, as a change amount: a second storage section configured to store a maximum value of the change amount which is calculable by the second change amount calculator when the steering angle sensor is normal, as a normal threshold value; a change amount comparator configured to compare the change amount with the normal threshold value, and to count a second counter when the change amount exceeds the normal threshold value; and a second judgment section configured to judge whether the second counter reaches a predetermined value each time the change amount exceeds the normal threshold value, to judge that the steering angle sensor is abnormal when the second counter reaches the predetermined value, and to reset the second counter when a second judgment time has passed while the second counter is kept below the predetermined value after the second counter is last counted. 
     With this configuration, even when the change amount temporarily becomes more than the normal threshold value, if the value of the second counter has not reached the predetermined value, the steering angle sensor is not judged as abnormal. Hence, in the diagnosis for the steering angle sensor, misjudgment can be prevented. When the value obtained from the steering angle sensor oscillates or continuous noise is generated, since the value of the second counter reaches the predetermined value, the abnormality can be judged securely. 
     Both of the first diagnosis and the second diagnosis may be performed simultaneously while commonly using the steering angle and the change amount for each diagnosis. 
     With this configuration, the first diagnosis and the second diagnosis can be performed collaterally by using the common values as the steering angle and the change amount. Hence, the abnormality can be judged rapidly by using two different diagnosing methods according to information on a single steering angle. 
     The above-mentioned abnormality judgment device may be provided in a vehicle controller, for example. 
     For example, the steering angle sensor may also have a diagnosis function. With this configuration, even when the steering angle sensor is misjudged as normal due to the abnormality of the diagnosis function therefor, or even when the value output from the steering angle sensor becomes abnormal before reaching the vehicle controller due to the transmission error, the diagnosis can be performed using the abnormality judgment device inside the vehicle controller. As a result, the accuracy of abnormality judgment can be improved. 
     With the present invention, misjudgment can be prevented when diagnosing the steering angle sensor. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a vehicle equipped with a vehicle controller; 
         FIG. 2  illustrates a brake hydraulic circuit of the vehicle controller; 
         FIG. 3  illustrates a control unit according to a first embodiment; 
         FIG. 4  illustrates the operation of the control unit of  FIG. 3 ; 
         FIGS. 5A to 5G  illustrate a diagnosis example when the steering angle of the vehicle is fixed to a large value; 
         FIGS. 6A to 6G  illustrate a diagnosis example when the steering angle is offset in two steps; 
         FIGS. 7A to 7G  illustrate a diagnosis example when the steering angle is not changed very largely; 
         FIGS. 8A to 8G  illustrate a diagnosis example when noise is input temporarily from the steering angle sensor of the vehicle; 
         FIGS. 9A to 9G  illustrate a diagnosis example after noise is input temporarily from the steering angle sensor and when the steering angle becomes abnormally large and is fixed to the abnormally large value during the increment of the value of a first preparatory timer; 
         FIG. 10  illustrates a control unit according to a second embodiment; 
         FIG. 11  illustrates the operation of the control unit of  FIG. 10 ; 
         FIGS. 12A to 12E  illustrate a diagnosis example when the steering angle is changed largely while having a large amplitude; and 
         FIGS. 13A to 13E  illustrate a diagnosis example when the steering angle is changed to an abnormally large value at first and then returns to a normal value. 
     
    
    
     DETAILED DESCRIPTION 
     [First Embodiment] 
     A first embodiment will be described below. 
     As shown in  FIG. 1 , a vehicle controller  100  is configured to appropriately control a braking force (brake fluid pressure) applied to each wheel W of a vehicle CR. For example, the vehicle controller  100  is provided inside the engine room of the vehicle. The vehicle controller  100  has a hydraulic unit  10  and a control unit  20 . The hydraulic unit  10  includes fluid passages (hydraulic passages) and various components, and the control unit  20  controls the components of the hydraulic unit  10 . 
     The control unit  20  is, for example, equipped with a CPU, a RAM, a ROM and input/output circuits, and performs control with various arithmetic processing based not only on the input from a wheel speed sensor  91 , a steering angle sensor  92 , a lateral acceleration sensor  93  and a yaw rate sensor  94 , but also on programs and data stored in the ROM. 
     The wheel speed sensor  91  is provided for each wheel W to detect the rotation speed thereof. 
     The steering angle sensor  92  is provided on the rotation shaft of the steering wheel ST to detect the steering angle thereof. 
     The lateral acceleration sensor  93  is integrally provided on the control unit  20  to detect the acceleration (lateral acceleration) exerted in the lateral direction of the vehicle CR. 
     The yaw rate sensor  94  is integrally provided on the control unit  20  to detect the turning angular velocity (actual yaw rate) of the vehicle CR. 
     Each of wheel cylinders H is a hydraulic device for converting the brake fluid pressure generated by a master cylinder MC and the vehicle controller  100  into the actuating force of each of the wheel brakes FR, FL, RR and RL provided for each wheel W. The wheel cylinders H are respectively connected to the hydraulic unit  10  via pipes. 
     As shown in  FIG. 2 , the hydraulic unit  10  is disposed between the master cylinder MC and the wheel brakes FR, FL, RR and RL. The master cylinder MC serves as a hydraulic source for generating brake fluid pressure depending on the driver&#39;s depressing force applied to the brake pedal BP. The hydraulic unit  10  is formed of a pump body  10   a  serving as a base body having fluid passages through which brake fluid flows, plural input valves  1  and plural output valves  2  disposed in the fluid passages, etc. 
     The pump body  10   a  has inlet ports  121  and outlet ports  122 . The inlet ports  121  are connected to two output ports M 1  and M 2  of the master cylinder MC, and the outlet ports  122  of the pump body  10   a  are respectively connected to the wheel brakes FR, FL, RR and RL. In the pump body  10   a , the inlet ports  121  and the outlet ports  122  are usually communicated so that the depressing force applied to the brake pedal BP is transmitted to each wheel brake FL/RR/RL/FR. 
     The fluid passage starting from the output port M 1  leads to the front left wheel brake FL and the rear right wheel brake RR, and the fluid passage starting from the output port M 2  leads to the front right wheel brake FR and the rear left wheel brake RL. In the following description, the fluid passage starting from the output port M 1  is referred to as a “first system,” and the fluid passage starting from the output port M 2  is referred to as a “second system.” 
     The first system of the hydraulic unit  10  includes two control valve units V respectively corresponding to the wheel brakes FL and RR. Similarly, the second system of the hydraulic unit  10  includes two control valve units V respectively corresponding to the wheel brakes RL and FR. Each of the first and second systems includes a reservoir  3 , a pump  4 , an orifice  5 , a pressure regulating unit (regulator) R and a suction valve  7 . A common motor  9  is provided for driving the pump  4  of the first system and the pump  4  of the second system. The rotation speed of the motor  9  is controllable. In the first embodiment, a pressure sensor  8  is provided only for the second system. 
     In the following description, the fluid passage from the output port M 1 /M 2  of the master cylinder MC to the pressure regulating unit R is referred to as an “output hydraulic passage A 1 .” The fluid passage from the pressure regulating unit R to the corresponding wheel brakes (“FL and RR” or “RL and FR”) is referred to as a “wheel hydraulic passage B.” The fluid passage from the output hydraulic passage A 1  to the pump  4  is referred to as a “suction hydraulic passage C.” The fluid passage from the pump  4  to the wheel hydraulic passage B is referred to as a “discharge hydraulic passage D.” And, the fluid passage from the wheel hydraulic passage B to the suction hydraulic passage C is referred to as an “open passage E.” 
     The control valve unit V controls the flow of the fluid under pressure between the master cylinder MC or the pump  4  and each wheel brake FL/RR/RL/FR (each wheel cylinder H), and can increase, retain or decrease the pressure of the wheel cylinder H. The control valve unit V includes an inlet valve  1 , an outlet valve  2  and a check valve  1   a.    
     The inlet valve  1  is a normally-open solenoid valve provided between the master cylinder MC and each wheel brake FL/RR/RL/FR, that is, in the wheel hydraulic passage B. Since the inlet valve  1  is normally open, the pressure of the brake fluid is allowed to be transmitted from the master cylinder MC to each wheel brake FL/RR/RL/FR. When the wheel W is likely to lock, the inlet valve  1  is closed by the control unit  20 , so that the transmission of the brake fluid pressure from the brake pedal BP to each wheel brake FL/RR/RL/FR is shut off. 
     The outlet valve  2  is a normally-closed solenoid valve provided between each reservoir  3  and each wheel brake FL/RR/RL/FR, that is, between the wheel hydraulic passage B and the open passage E. Although the outlet valve  2  is normally closed, it is opened by the control unit  20  when the wheel W is likely to lock, so that the brake fluid pressure applied to each wheel brake FL/RR/RL/FR is relieved to each reservoir  3 . 
     The check valve  1   a  is connected in parallel with each inlet valve  1 . The check valve  1   a  is a one-way valve for allowing the brake fluid to flow only from each wheel brake FL/RR/RL/FR to the master cylinder MC. Even when the input from the brake pedal BP is released while the inlet valve  1  is closed, the check valve  1   a  allows the brake fluid to flow from each wheel brake FL/RR/RL/FR to the master cylinder MC. 
     The reservoir  3  is provided in the open passage E to absorb the brake fluid pressure that is relieved when each outlet valve  2  is opened. A check valve  3   a  is provided between the reservoir  3  and the pump  4  to allow the brake fluid to flow only from the reservoir  3  to the pump  4 . 
     The pump  4  is provided between the suction hydraulic passage C communicating with the output hydraulic passage A 1  and the discharge hydraulic passage D communicating with the wheel hydraulic passage B to suck the brake fluid stored in the reservoir  3  and to discharge the brake fluid to the discharge hydraulic passage D. As a result, the brake fluid sucked from the reservoir  3  can be returned to the master cylinder MC. Even when the driver does not operate the brake pedal BP, brake fluid pressure is generated, and a braking force can be applied to the wheel brakes FL, RR, RL and FR. 
     The discharge amount of the brake fluid from the pump  4  depends on the rotation speed of the motor  9 . For example, when the rotation speed of the motor  9  becomes high, the discharge amount of the brake fluid from the pump  4  increases. 
     The orifice  5  attenuates the pulsation of the pressure of the brake fluid discharged from the pump  4 . 
     Since the pressure regulating unit R is normally open, the brake fluid can flow from the output hydraulic passage A 1  to the wheel hydraulic passage B. When the pressure on the side of the wheel cylinder H is raised by the pump  4 , the pressure regulating unit R adjusts the pressure on the side of the discharge hydraulic passage D, the wheel hydraulic passage B and the wheel cylinder H to a preset value or less while shutting off the flow of the brake fluid. The pressure regulating unit R includes a change-over valve  6  and a check valve  6   a.    
     The change-over valve  6  is a normally-open linear solenoid valve provided between the output hydraulic passage A 1  communicating with the master cylinder MC and the wheel hydraulic passage B communicating with each wheel brake FL/RR/RL/FR. When the valve element of the change-over valve  6  is electromagnetically energized to the side of the wheel hydraulic passage B and the wheel cylinder H and when the pressure of the wheel hydraulic passage B becomes higher than the pressure of the output hydraulic passage A 1  by a predetermined value (this predetermined value depends on the energization degree of the change-over valve  6 ) or more, the brake fluid escapes from the wheel hydraulic passage B to the output hydraulic passage A 1 , whereby the pressure on the side of the wheel hydraulic passage B is adjusted, although the details are not shown in the figure. 
     The check valve  6   a  is connected in parallel with each change-over valve  6 . The check valve  6   a  is a one-way valve for allowing the brake fluid to flow from the output hydraulic passage A 1  to the wheel hydraulic passage B. 
     The suction valve  7  is a normally-closed solenoid valve provided in the suction hydraulic passage C. The suction valve  7  switches the suction hydraulic passage C to an open state or a closed state. When the change-over valve  6  is closed, that is, when the brake fluid pressure is to be applied to each wheel brake FL/RR/RL/FR while the driver does not operate the brake pedal BP, the suction valve  7  is opened by the control unit  20 . 
     The pressure sensor  8  detects the brake fluid pressure of the output hydraulic passage A 1  of the second system, and its detection result is input to the control unit  20 . 
     Next, the details of the control unit  20  will be described below. 
     As shown in  FIGS. 1 to 3 , the control unit  20  controls the open/close operations of the control valve unit V, the change-over valve  6  (the pressure regulating unit R) and the suction valve  7  and the operation of the motor  9  inside the hydraulic unit  10  based on the signals input from the sensors  91  to  94 , for example, thereby controlling the operation of each wheel brake FL/RR/RL/FR. In the first embodiment, the control unit  20  functions as an abnormality judgment device for judging whether the steering angle sensor  92  is normal. 
     In the first embodiment, the steering angle sensor  92  includes known judging means thereinside for judging whether the steering angle sensor  92  is normal. The judging means outputs a signal (“sensor side signal”) indicating whether the steering angle sensor  92  is normal (see  FIG. 5A ) to the control unit  20 . In other words, in the first embodiment, each of the steering angle sensor  92  and the control unit  20  performs abnormality judgment for the steering angle sensor  92 . 
     As shown in  FIG. 3 , the control unit  20  includes a first diagnosing section  21  configured to perform a first diagnosis for judging whether the steering angle sensor  92  is normal and a behavior controller  22  for controlling the behavior of the vehicle CR. The first diagnosing section  21  includes a first change amount calculator  21 A, a first storage section  21 B, a reference setting section  21 C, a first timer  21 D, an incrementing section  21 E, a deviation comparator  21 F, a first counter  21 G, a first preparatory timer  21 J, and a first judgment section  21 H. 
     The first change amount calculator  21 A calculates the absolute difference between the current value and the previous value of the steering angle obtained from the steering angle sensor  92  and outputs the calculated change amount to the reference setting section  21 C. 
     The first storage section  21 B is a storage device, such as a memory, for storing, as a normal threshold value, the maximum change amount that can be calculated by the first change amount calculator  21 A when the steering angle sensor  92  is normal. “The maximum change amount that can be obtained by the first change amount calculator  21 A when the steering angle sensor  92  is normal” can be determined by experiments, simulations, etc. 
     The reference setting section  21 C compares the change amount obtained from the first change amount calculator  21 A with the normal threshold value obtained from the first storage section  21 B, and sets the previous value (the steering angle at time t 1  in  FIG. 5B ) of the steering angle to a reference steering angle when the change amount becomes more than the normal threshold value (time t 2  in  FIG. 5D ). The reference setting section  21 C sets the reference steering angle, and then outputs the set reference steering angle to the deviation comparator  21 F and activates the first timer  21 D. At this time, the reference setting section  21 C counts up the value of the first counter  21 G and resets the value of the first preparatory timer  21 J. 
     When the change amount is less than the normal threshold value, the reference setting section  21 C transmits a signal indicating this state to the first judgment section  21 H and activates the first preparatory timer  21 J. 
     The first timer  21 D sets a first judgment time, and gradually decrements the set first judgment time (see  FIG. 5F ) upon receiving an activation signal from the reference setting section  21 C. 
     The incrementing section  21 E gradually increments the normal threshold value at a predetermined timing during a period until the set first judgment time becomes zero (a period until the first judgment time passes from the time when the change amount became more than the normal threshold value) referring to the value of the first timer  21 D (see  FIG. 5C ). More specifically, the incrementing section  21 E adds a constant value to the normal threshold value each time the deviation comparator  21 F performs comparison so that the normal threshold value becomes proportional to the number of comparisons performed by the deviation comparator  21 F. 
     In other words, the incrementing section  21 E adds the constant value to the normal threshold value each time the time corresponding to the cycle of the comparison by the deviation comparator  21 F passes referring to the value of the first timer  21 D. The incrementing section  21 E outputs the normal threshold value obtained from the first storage section  21 B or the normal threshold value obtained by adding the constant value each time the comparison is performed. 
     The deviation comparator  21 F obtains the steering angle (the current value) and the reference steering angle from the reference setting section  21 C, and calculates the absolute deviation (“deviation”) between the steering angle and the reference steering angle. Also, the deviation comparator  21 F compares the calculated deviation with the normal threshold value obtained from the incrementing section  21 E, and counts up the value of the first counter  21 G when the deviation is larger than the normal threshold value (see  FIGS. 5C and 5E ). And, the deviation comparator  21 F performs the above-mentioned comparison between the deviation and the normal threshold value and the above-mentioned counting up only during the first judgment time referring to the value of the first timer  21 D. 
     The first preparatory timer  21 J increments the value thereof upon receiving the activation signal from the reference setting section  21 C (see  FIG. 7G ). After being incremented to a first preparatory judgment time, the value of the first preparatory timer  21 J is not incremented further. 
     The first judgment section  21 H judges whether the steering angle sensor  92  is abnormal by judging whether the value of the first counter  21 G has reached a predetermined value referring to the value of the first counter  21 G. When the value of the first counter  21 G has reached the predetermined value, the first judgment section  21 H judges that the steering angle sensor  92  is abnormal. 
     Also, the first judgment section  21 H determines whether the value of the first counter  21 G is reset referring to the signal (the signal indicating that the change amount is less than the normal threshold value) transmitted from the reference setting section  21 C, the value of the first timer  21 D and the value of the first preparatory timer  21 J. More specifically, the first judgment section  21 H judges whether the first judgment time has passed referring to the value of the first timer  21 D and also judges whether the change amount is less than the normal threshold value referring to the signal from the reference setting section  21 C. 
     When the first judgment time has passed and that the change amount is less than the normal threshold value, the first judgment section  21 H judges whether the first preparatory judgment time has passed after the passage of the first judgment time referring to the value of the first preparatory timer  21 J. And, the first judgment section  21 H resets the value of the first counter  21 G when the first preparatory judgment time has passed. 
     When the value of the first counter  21 G is less than the predetermined value even after the first judgment time has passed, the first judgment section  21 H resets the reference steering angle and the normal threshold value to their initial values (see  FIGS. 7B and 7C ). Then, the first judgment section  21 H outputs a signal (“judgment section side signal”) indicating whether the steering angle sensor  92  is abnormal to the behavior controller  22 . 
     The behavior controller  22  judges whether the known vehicle behavior control is to be performed based on the judgment section side signal obtained from the first judgment section  21 H and the sensor side signal transmitted from the steering angle sensor  92 . More specifically, the behavior controller  22  inhibits behavior control when at least one of the judgment section side signal and the sensor side signal indicates abnormality, and performs behavior control when both the judgment section side signal and the sensor side signal indicate normality. 
     Hence, for example, even when the steering angle sensor  92  is misjudged as normal due to the abnormality of the judging means thereinside and the sensor side signal indicating normality is output, or even when the value output from the steering angle sensor  92  becomes abnormal before reaching the vehicle controller  100  due to the transmission error, the first diagnosing section  21  inside the control unit  20  can perform a judgment again as to whether the steering angle sensor  92  is abnormal. As a result, the accuracy of abnormality judgment can be improved. 
     Next, the operation of the control unit  20  will be described below referring to  FIG. 4 . 
     As shown, in  FIG. 4 , the control unit  20  calculates the change amount based on the current value and die previous value of the steering angle (at S 1 ), and judges whether the value of the first timer  21 D is more than 0 (at S 2 ). When the value of the first timer  21 D is 0 (No) at step S 2 , the control unit  20  resets the reference steering angle and the normal threshold value (at S 3 ) and judges whether the change amount calculated at step S 1  is more than the normal threshold value (at S 4 ). 
     When the change amount is more than the normal threshold value at step S 4  (Yes), the control unit  20  sets the previous value of the steering angle obtained at the time as the reference steering angle and sets the first judgment time (at S 5 ). After step S 5 , the control unit  20  resets the value of the first preparatory timer  21 J (at S 6 ) and counts up the value of the first counter  21 G (at S 7 ). 
     When the value of the first timer  21 D is more than 0 at step S 2  (Yes), the control unit  20  decrements the value of the first timer  21 D (at S 8 ), and increments the normal threshold value by a constant value (at S 9 ). After step S 9 , the control unit  20  judges whether the deviation (absolute difference) between the current value of the steering angle and the reference steering angle is more than the normal threshold value (at S 10 ). 
     When the deviation is more than the normal threshold value at step S 10  (Yes), the control unit  20  counts up the value of the first counter  21 G (at S 11 ), and the processing advances to step S 12 . When the deviation is less than the normal threshold value at step S 10  (No), the control unit  20  does not count up the value of the first counter  21 G, and the processing advances to step S 12 . 
     At step S 12 , the control unit  20  judges whether the value of the first counter  21 G has become equal to or more than the predetermined value (has reached the predetermined value). When the value of the first counter  21 G is less than the predetermined value at step S 12  (No), the processing of the control unit  20  returns to step S 1 . 
     When the value of the first counter  21 G is equal to or more than the predetermined value at step S 12  (Yes), the control unit  20  judges that the steering angle sensor  92  is abnormal (at S 13 ). 
     When the change amount is less than the normal threshold value at S 4  (No), the control unit  20  increments the value of the first preparatory timer  21 J (at S 14 ) and judges whether the value of the first preparatory timer  21 J is equal to or more than the first preparatory judgment time (whether the first preparatory judgment time has passed after the passage of the first judgment time) (at S 15 ). 
     When the value of the first preparatory timer  21 J is less than the first preparatory judgment time at step S 15  (No), the processing of the control unit  20  directly returns to step S 1 . When the value of the first preparatory timer  21 J is equal to or more than the first preparatory judgment time (Yes), the control unit  20  resets the value of the first counter  21 G (at S 16 ), and the processing returns to step S 1 . 
     Next, referring to  FIGS. 5A to 5G  to  FIGS. 9A to 9G , examples of diagnosis (normal/abnormal judgment) for the steering angle sensor  92  using the control unit  20  will be described. 
     In an example of  FIGS. 5A to 5G , the output steering angle of the steering angle sensor  92  is changed and fixed to a large value (see  FIG. 5B ) different from the actual steering angle although the sensor side signal indicates normality (see  FIG. 5A ). In such case, as shown in  FIGS. 5C to 5G , when the change amount becomes more than the normal threshold value (at time t 2 ), the steering angle at time t 1  is set as the reference steering angle and the difference between the steering angle and the reference steering angle is calculated. In addition, at this time, the value of the first preparatory timer  21 J being incremented to the first preparatory judgment time is reset. 
     Then, since the deviation is fixed to the large value, even when the normal threshold value becomes larger gradually during the first judgment time, the deviation always exceeds the normal threshold value. Hence, the value of the first counter  21 G reaches the predetermined value (at time t 3 ) during the first judgment time. As a result, the steering angle sensor  92  is judged as abnormal. 
     In an example of  FIGS. 6A to 6G , the output steering angle of the steering angle sensor  92  is different from the actual steering angle, and the output steering angle is offset to a larger value and to a further larger value in two steps (see  FIG. 6B ), although the sensor side signal indicates normality (see  FIG. 6A ). In such case, as shown in  FIGS. 6C to 6F , during a predetermined time (between time t 4  to time t 5 ) from the time (time t 4 ) when the change amount becomes more than the normal threshold value, since the deviation is more than the normal threshold value, the value of the first counter  21 G is counted up. 
     After time t 5 , that is, after the normal threshold value being incremented gradually becomes equal to or more than the deviation, the value of the first counter  21 G is not counted up and the value of the first timer  21 D is decremented. Then, when the deviation is changed to the further larger value at time t 6 , the deviation becomes more than the normal threshold value, and the counting up of the value of the first counter  21 G is resumed. Thereafter, when the value of the first counter  21 G reaches the predetermined value (at time t 7 ), the steering angle sensor  92  is judged as abnormal. 
     In an example of  FIGS. 7A to 7G , the output steering angle of the steering angle sensor  92  is different from the actual steering angle, and the output steering angle is not changed largely, although the sensor side signal indicates normality (see FIG  7 A). In such case, as shown in  FIGS. 7B to 7G , during a predetermined time (between time t 9  to time t 10 ) from the time (time t 9 ) when the change amount becomes more than the normal threshold value, since the deviation is more than the normal threshold value, the value of the first counter  21 G is counted up. 
     After time t 10 , that is, after the value of the normal threshold value being incremented gradually becomes equal to or more than the deviation, the value of the first counter  21 G is not counted up and the value of the first timer  21 D is decremented. Then, when the value of the first timer  21 D becomes zero (at time t 11 ) while the value of the first counter  21 G does not reach the predetermined value, the calculation of the deviation is ended, the reference steering angle and the normal threshold value are reset, and the value of the first preparatory timer  21 J is incremented. 
     Then, when the value of the first preparatory timer  21 J reaches the first preparatory judgment time (at time t 12 ), the value of the first counter  21 G is reset. Hence, the steering angle sensor  92  is not judged as abnormal. 
     In an example of  FIGS. 8A to 8G , noise is input temporarily from the steering angle sensor  92 , although the sensor side signal indicates normality (see  FIG. 8A ). In such case, as shown in  FIGS. 8B to 8G , during a predetermined time (between time t 13  to time t 14 ) from the time (time t 13 ) when the change amount becomes more than the normal threshold value, since the deviation is more than the normal threshold value, the value of the first counter  21 G is counted up. 
     After time t 14 , that is, after the noise is not input and when the deviation having been more than the normal threshold value becomes equal to or less than the normal threshold value, the value of the first counter  21 G is not counted up, and the value of the first timer  21 D is decremented. Then, when the value of the first timer  21 D becomes zero (at time t 15 ) while the value of the first counter  21 G does not reach the predetermined value, the calculation of the deviation is ended, the reference steering angle and the normal threshold value are reset, and the value of the first preparatory timer  21 J is incremented. 
     Then, when the value of the first preparatory timer  21 J reaches the first preparatory judgment time (at time t 16 ), the value of the first counter  21 G is reset. Hence, the steering angle sensor  92  is not judged as abnormal. 
     In an example of  FIGS. 9A to 9G , noise is input temporarily from the steering angle sensor  92  and then the steering angle becomes abnormally large and fixed to the abnormally large value while the value of the first preparatory timer  21 J is incremented, although the sensor side signal indicates normality (see  FIG. 9A ). In such case, as shown in  FIGS. 9B to 9G , during a predetermined time (between time t 17  to time t 18 ) from the time (time t 17 ) when the change amount becomes more than the normal threshold value, since the deviation is more than the normal threshold value, the value of the first counter  21 G is counted up. 
     After time t 18 , that is, after the noise input for the first time disappears and when the deviation having been more than the normal threshold value becomes equal to or less than the normal threshold value, the value of the first counter  21 G is not counted up, and the value of the first timer  21 D is decremented. Then, when the value of the first timer  21 D becomes zero (at time t 19 ) while the first counter  21 G does not reach the predetermined value, the calculation of the deviation is ended, the reference steering angle and the normal threshold value are reset, and the value of the first preparatory timer  21 J is incremented. 
     Then, when noise is input for the second time before the value of the first preparatory timer  21 J reaches the first preparatory judgment time (at time t 20 ), the value of the first preparatory timer  21 J is reset, and the value of the first timer  21 D is set to the first judgment time again. At this time, the reference steering angle is set again and the deviation is calculated. 
     Thereafter, when the deviation becomes more than the normal threshold value, the counting up of the value of the first counter  21 G is resumed. When the value of the first counter  21 G reaches the predetermined value (at time t 21 ), the steering angle sensor  92  is judged as abnormal. In other words, in the example of  FIGS. 9A to 9G , the abnormality judgment is interrupted once since the first judgment time for the first time has passed. At the time, the value of the first counter  21 G is not reset and the value of the first counter  21 G is maintained during the first judgment time. Hence, when the steering angle becomes abnormal again during the first preparatory judgment time, the value of the first counter  21 G can be counted up from the maintained value, whereby the abnormality can be judged easily. 
     Accordingly, the first embodiment can provide the following effects. 
     Even when the change amount temporarily becomes more than the normal threshold value, if the value of the first counter  21 G has not reached the predetermined value, the steering angle sensor  92  is not judged as abnormal (see  FIGS. 7A to 7G ). Hence, in the diagnosis for the steering angle sensor  92 , misjudgment can be prevented. When abnormality occurs because the steering angle is maintained, fixed or offset to an abnormally high value, the value of the first counter  21 G reaches the predetermined value (see  FIGS. 5A to 5G  and  FIGS. 6A to 6G ), whereby the abnormality can be judged securely. 
     The normal threshold value is determined by simple increment wherein the normal threshold value is incremented by a constant value. Hence, it is not necessary to prepare complicated calculating formulas and complicated maps. 
     Even when the steering angle sensor  92  is misjudged as normal due to the abnormality of the diagnosis function (judging means) therefor, or even when the value output from the steering angle sensor becomes abnormal before reaching the vehicle controller  100  due to the transmission error, the diagnosis can be performed by the control unit  20  (abnormality judgment device) inside the vehicle controller  100 . Hence, the accuracy of abnormality judgment can be improved. 
     [Second Embodiment] 
     Next, a second embodiment will be described below. This embodiment is obtained by modifying part of the structure of the control unit  20  according to the first embodiment. Components similar to those in the first embodiment are designated by the same reference codes, and their descriptions are omitted. 
     As shown in  FIG. 10 , a control unit  30  according to the second embodiment has a behavior controller  22  and a second diagnosing section  31 . While the behavior controller  22  is similar to that in the first embodiment, a second diagnosing section  31  performs second diagnosis different from the first diagnosis in the first embodiment. The second diagnosing section  31  includes a second change amount calculator  31 A, a second storage section  31 B, a change amount comparator  31 C, a second counter  31 D, a second judgment section  31 E, and a second timer  31 F. 
     The second change amount calculator  31 A calculates the change amount as the first change amount calculator  21 A, and outputs the calculated change amount to the change amount comparator  31 C. 
     The second storage section  31 B stores, as the normal threshold value, the maximum change amount that can be calculated by the second change amount calculator  31 A when the steering angle sensor  92  is normal, as the first storage section  21 B in the first embodiment. 
     The change amount comparator  31 C compares the change amount obtained from the second change amount calculator  31 A with the normal threshold value obtained from the second storage section  31 B, and counts up the value of the second counter  31 D when the change amount becomes more than the normal threshold value. Also, the change amount comparator  31 C restarts increment of the value of the second timer  31 F from zero each time the value of the second counter  31 D is counted up. 
     The second judgment section  31 E judges whether the value of the second counter  31 D has reached the predetermined value each time the value of the second counter  31 D is counted up, and judges that the steering angle sensor  92  is abnormal under the condition that the value has reached the predetermined value. Also, the second judgment section  31 E judges whether a second judgment time has passed after the current counting of the value of the second counter  31 D, and resets the value of the second counter  31 D under the condition that the second judgment time has passed. More specifically, the second judgment section  31 E judges whether the value of the second counter  31 D has reached the predetermined value and also judges whether the second judgment time has passed after the count-up time referring to the values of the second counter  31 D and the second timer  31 F. 
     When the value of the second counter  31 D has reached the predetermined value before the second judgment time passes, the second judgment section  31 E judges that the steering angle sensor is abnormal (see  FIGS. 12D and 12E ). When the second judgment time has passed, the second judgment section  31 E resets the value of the second counter  31 D (returns the value to zero, see  FIGS. 13D and 13E ). 
     Next, the operation of the control unit  30  will be described below referring to  FIG. 11 . 
     As shown in  FIG. 11 , the control unit  30  calculates the change amount based on the current value and the previous value of the steering angle (at S 21 ) and judges whether the calculated change amount is more than the normal threshold value (at S 22 ). When the change amount is more than the normal threshold value at step S 22  (Yes), the control unit  30  counts up the value of the second counter  31 D (at S 23 ) and resets the value of the second timer  31 F (at S 24 ). 
     After step S 24 , the control unit  30  judges whether the value of the second counter  31 D has become equal to or more than the predetermined value (at S 25 ). When the value of the second counter  31 D has become equal to or more than the predetermined value at step S 25  (Yes), the control unit  30  judges that the steering angle sensor  92  is abnormal (at S 26 ). When the value is less than the predetermined value (No), the processing directly returns to step S 21 . 
     When the change amount is less than the normal threshold value at S 22  (No), the control unit  30  increments the value of the second timer  31 F (at S 27 ). After step S 27 , the control unit  30  judges whether the second judgment time has passed referring to the value of the second timer  31 F (at S 28 ). 
     When the second judgment time has passed (Yes) at step S 28 , the control unit  30  resets the value of the second counter  31 D. When the second judgment time has not passed (No), the processing returns to step S 21  without resetting the value of the second counter  31 D. 
     Next, referring to  FIGS. 12A to 5E  to  FIGS. 13A to 13E , examples of diagnosis (normal/abnormal judgment) for the steering angle sensor  92  using the control unit  30  will be described. 
     In an example of  FIGS. 12A to 12E , the output steering angle of the steering angle sensor  92  is different from the actual steering angle, and the output steering angle is changed largely while having a large amplitude (see  FIG. 12B ), although the sensor side signal indicates normality (see  FIG. 12A ). In such case, as shown in  FIGS. 12C to 12E , the value of the second counter  31 D is counted up and the value of the second timer  31 F is reset each time the change amount becomes more than the normal threshold value (between time t 31  to time t 35 ). Hence, since the change amount becomes more than the normal threshold value frequently, the value of the second counter  31 D reaches the predetermined value (at time t 35 ) before the value of the second timer  31 F reaches the second judgment time. As a result, the steering angle sensor  92  is judged as abnormal. 
     In an example of  FIGS. 13A to 13E , the output steering angle of the steering angle sensor  92  is different from the actual steering angle although the sensor side signal indicates normality (see  FIG. 13A ), but the steering angle has an abnormally large value only at first and becomes coincident with the actual steering angle thereafter (see  FIG. 13B ). In such case, as shown in  FIGS. 13B to 13E , the change amount becomes more than the normal threshold value only when the steering angle is changed largely at first (at time t 36 ) and only when the steering angle is returned to its original value (at time t 37 ). Hence, the value of the second counter  31 D is counted up and the value of the second timer  31 F is reset only at these times. 
     After time t 37 , the steering angle is changed so as to be coincident with the actual steering angle, whereby the change amount does not become more than the normal threshold value. Hence, the value of the second timer  31 F is not reset but is counted up. When the value of the second timer  31 F reaches the second judgment time (at time t 38 ), the value of the second counter  31 D is reset. Therefore, the steering angle sensor  92  is not judged as abnormal. 
     Accordingly, the second embodiment can provide the following effects. 
     Even when the change amount temporarily becomes more than the normal threshold value, if the value of the second counter  31 D has not reached the predetermined value, the steering angle sensor  92  is not judged as abnormal. Hence, in the diagnosis for the steering angle sensor  92 , misjudgment can be prevented (see  FIGS. 13A to 13E ). When the value obtained from the steering angle sensor  92  oscillates or continuous noise is generated, since the value of the second counter  31 D reaches the predetermined value, the abnormality can be judged securely (see  FIGS. 12A to 12E ). 
     The present invention is not limited to the above-mentioned embodiments but can be applied to various embodiments exemplified below. 
     In each embodiment described above, the control unit performs only the first diagnosis or only the second diagnosis. However, both the above-mentioned first diagnosing section  21  and the above-mentioned second diagnosing section  31  can be provided for one control unit. In this case, the first diagnosing section  21  and the second diagnosing section  31  may perform the first diagnosis and the second diagnosis simultaneously by using common values as the steering angle and the change amount. With this configuration, the first diagnosis and the second diagnosis can be performed collaterally by using the common values as the steering angle and the change amount. Hence, since two different diagnosing methods according to information on a single steering angle is used, for example, by judging the steering angle sensor to be abnormal when one of the two diagnosing section judges that the steering angle sensor is abnormal, the abnormality can be judged rapidly. Alternatively, by judging the steering angle sensor to be abnormal when both the two diagnosing section judge that the sensor is abnormal, careful judgment can be performed even in a situation where noise is likely to be introduced. 
     In each embodiment described above, the abnormality judgment device (the first diagnosing section  21  or the second diagnosing section  31 ) is provided in the vehicle controller  100 . However, the abnormality judgment devices may be provided inside the steering angle sensor, for example. 
     In the above-mentioned embodiments, the values of the first counter  21 G and the second counter  31 D are respectively counted up. However, the values thereof may be counted down.