Abstract:
A motor control for an electric motor powered vehicle having an accelerator control connected to a control circuit for supplying the desired driving power that senses possible errors of various types and stops the supply of driving power until normal operation resumes.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to a drive controlling device of an electric motor-driven vehicle such as an electric motor-driven golf car or the like ands more particularly to an arrangement for protecting against inadvertent application of power due to a failure in the accelerator control system.  
         [0002]     In recent years, there have been proposed a wide variety of electric motor powered vehicles for a variety of purposes. For example, electrically powered golf cars are widely used in golf courses. In such applications controls have been incorporated for accommodating the various terrains over which these vehicles are operated. As a specific example golf carts frequently employ sensors for determining the slope of the ground on which the cart is operating to provide the appropriate power to compensate for changes in grade. An example of such a control arrangement is shown in Japanese Published application JP-A-Hei 10-309005.  
         [0003]     In this arrangement, the electric motor-driven golf car, like an ordinary road vehicle, is provided with an accelerator pedal and a brake pedal for operation by the driver to control running of the golf car. Specifically, operation of the accelerator pedal by a driver, for example, is transmitted to an accelerator switch and an accelerator sensor connected to a controller that appropriately controls the drive of a shunt-wound type motor of the vehicle.  
         [0004]     However, the electric motor-driven golf car of this type is often subjected to irregular shocks from outside due to particularity of its use. These shocks may be caused from various unique conditions such as the loading and unloading of golf bags or operation over rough ground surfaces. It is not uncommon for these shocks to cause breakage of wire of the accelerator sensor resulting in an abnormality of its output. In such a case, the motor controller fails to read the actual position of the accelerator pedal operated by the driver and the golf car may run against the driver&#39;s intention.  
         [0005]     It is, therefore, a principal object of this invention to provide in arrangement for insuring against undesired operation in the event of a failure in the accelerator control mechanism.  
       SUMMARY OF THE INVENTION  
       [0006]     A first feature of this invention is adapted to be embodied in a drive controlling device of an electric motor driven vehicle having an electric motor driving a propulsion device of the vehicle in response to the operation of an accelerator pedal by a driver. The controlling device includes a an accelerator control operated by the vehicle operator and an accelerator sensor for outputting a signal corresponding to the operating position of the accelerator pedal. The signal outputted from the accelerator sensor is transmitted to a control for calculating a motor driving current in response to the signal. In the event of an abrupt change in the output signal from the accelerator sensor, the output value of the acceleration sensor is replaced by a given value at which the motor is stopped. After a first given period of time has elapsed the output value of the accelerator sensor is read again for a second given period of time. If at that time the predetermined stoppage canceling condition is satisfied driving current supply from the control means to the electric motor is resumed.  
         [0007]     Another feature of this invention is adapted to be embodied in a method of controlling the electric motor of an electric motor driven vehicle having an electric motor driving a propulsion device driven by the electric motor in response to the operation of an accelerator pedal by a driver. The method comprises the sensing of the position of the accelerator pedal and calculating a motor driving current in response to the signal. In the event of an abrupt change in the output signal from the accelerator sensor, the output value of the acceleration sensor is replaced by a given value at which the motor is stopped. After a first given period of time has elapsed the output value of the accelerator sensor is read again for a second given period of time. If at that time the predetermined stoppage canceling condition is satisfied driving current supply from the control means to the electric motor is resumed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a top plan view of an electric powered vehicle in the example of a golf cart constructed and operated in accordance with the invention.  
         [0009]      FIG. 2  is a block diagram of a drive controlling device for a golf car in accordance with the invention;  
         [0010]      FIG. 3  is a schematic wiring drawing of wiring around the input section of the accelerator sensor and the controller of the controlling device.  
         [0011]      FIG. 4  is a flowchart showing operations of the controlling device.  
         [0012]      FIG. 5  is graph showing one occurrence of an abnormality in the accelerator sensor such as an example of change in the sensor output when the GND line of the accelerator sensor is broken.  
         [0013]      FIG. 6  is a graph showing another occurrence of an abnormality in the accelerator sensor such as an example of change in the sensor output when a power source line or a signal line of the accelerator sensor is broken.  
         [0014]      FIG. 7  is still another graph showing an occurrence of an abnormality in the accelerator sensor such as a change in the sensor output when chattering occurs between the power source line and the signal line of the accelerator sensor; and  
         [0015]      FIG. 8  is a further graph showing an occurrence of an abnormality in the accelerator sensor as occurs when chattering occurs between the signal line and the GND line of the accelerator sensor. 
     
    
     DETAILED DESCRIPTION  
       [0016]     Referring now in detail to the drawings and initially to  FIG. 1 , an electrically powered vehicle such as a golf cart, as an example of vehicle with which the invention may be practiced is identified generally by the reference numeral  21 . This golf cart  21  is provided with a body, frame  22  that rotatably supports in any desired manner paired front wheels  23  and rear wheels  24 . In the illustrated embodiment, the rear wheels  24  are driven by a shunt type electric motor  25  through a transmission  26 . Associated with some or all of the wheels  23  and  24  (only the front wheels  23  in the illustrated embodiment) are brakes  27  of any desired type.  
         [0017]     An operator may be seated on a suitable seat (neither of which are shown) behind an accelerator pedal  28 , for controlling the speed of the electric motor  25 , a brake pedal  29 , for operating the wheel brakes  27 , and a steering wheel  31 , for steering the front wheels  23  in any desired manner.  
         [0018]     Also juxtaposed to the operator&#39;s position is a main switch  32 , and a direction control switch  33 , for controlling the direction of travel of the golf cart  21  by controlling the direction of rotation of the motor  25 . The main switch  32  and the direction control switch  33  are connected to a controller  34 . Operation of the accelerator pedal  28  is transmitted to an on off pedal switch  35  and an accelerator opening degree sensor  36  connected to the controller  34 , to send on or off state of the accelerator  28  and its degree of opening to the controller  34 .  
         [0019]     A plurality of batteries  37  (48 V in total, for example) as power sources are mounted suitably on the body frame  22  and are connected through a relay  38  to the controller  34 .  
         [0020]     The construction of a drive controlling device of a golf car according to this invention will now be described by reference to  FIG. 2 .  
         [0021]     The drive controlling device of the golf car  21  is indicated generally by the reference numeral  42  cooperates with the accelerator sensor  36 , and includes the controller  34  in which an abnormality of the accelerator sensor  36  is detected based on the condition of the output from the accelerator sensor  36  in accordance with the procedures as will be described later.  
         [0022]     As has already been noted, the accelerator sensor  36  is connected to the accelerator pedal  28  and outputs to the controller  34  a voltage corresponding to the amount of depression of the accelerator pedal  28  by the driver.  
         [0023]     The controller  34  is provided with a processing unit (MPU)  43  that receives a voltage from the accelerator sensor  36  for performing a given calculation for the drive of the motor; a memory (EEPROM)  44  for storing data; a motor driving circuit  45  for outputting a current for the drive of the motor  25 ; and a power source circuit  46  for supplying electric power from batteries  37  to the MPU  43 , motor driving circuit  45  and accelerator sensor  36 . In this embodiment, the power source circuit  46  is arranged such that it supplies electric power of 48V to the motor driving circuit  45  in response to main switch  32  being switched on, electric power of 5V to the processing unit  43 , and likewise, electric power of 5V to the accelerator sensor  36 , as an example. The accelerator sensor  36  and the power source circuit  46  are connected by a power source line  47  and a ground (GND) line  48 . The accelerator sensor  36  is connected to the processing unit  43  through a signal line  49  for outputting a voltage corresponding to the position of the accelerator pedal  28 .  
         [0024]     The controlling device  42  is provided with a warning device such as a buzzer  28  for warning the driver of occurrence of an abnormality at the time of determination of an abnormality in the manner to be described later. The warning buzzer  51  is connected to the processing unit  43  for judging the abnormality of the accelerator sensor  36 .  
         [0025]     Referring now to  FIG. 3 , the processing unit  43 , shown by a broken line, internally performs a judgment of abnormality of the accelerator sensor  36 , averages read values of the accelerator sensor (accelerator sensor averaging process), and further calculates a driving current and a duty ratio of the motor by using the accelerator average value obtained, for the PWM output to the motor driving circuit  45 . The motor driving circuit  45  has internally the function (current detection circuit) of detecting the motor driving electric current being outputted at present, and the value of the detected motor current is fed back to the processing unit  43 .  
         [0026]     As shown in  FIG. 3 , the signal line  49  from the accelerator sensor  36  is connected to the input section of the processing unit  43  of the controller  34  through resistors  52 ,  53 . The signal line  49  is dropped to the ground (GND) through a resistor  31  having a resistor value (for example, 1MΩ) much larger than that of the resistor  52  or  53 , and located closer to the accelerator sensor  36  than the resistors  52 ,  53 .  
         [0027]     In the operation of the controlling device  42  according to this invention, if a breaking of wire occurs in any of the power source line  47 , the ground (GND) line  48  or the signal line  49  connected to the accelerator sensor  36 , or an abnormality happens in the signal output from the accelerator sensor due to chattering, such an abnormality is detected immediately, and running of the golf car  21  itself is stopped and warning of the abnormality is issued to the driver with the warning buzzer  51 . This will now be described by reference to the control routine shown in  FIG. 4  and the various types of failures that may occur, as shown in  FIGS. 5-8 .  
         [0028]     For example, if the GND line  48  connecting the accelerator sensor  36  and the power source circuit  46  is completely broken by some external force as shown in  FIG. 5 , the signal line  49  is dropped to the ground (GND) through a resistor  54  having a much larger resistor value than the resistor inside the accelerator sensor  36  and the voltage detected by the processing unit  43  in the construction shown in  FIG. 3  is fixed to a value around 5V, and as illustrated by the solid line in  FIG. 5 . The broken line in  FIG. 5  shows an example of the change in the output voltage of the accelerator sensor  36  at the time of depression of the accelerator pedal when the accelerator sensor is normal. Thus if the GND line  48  of the accelerator sensor  36  has been broken, an abrupt voltage rise in the output of the accelerator sensor  36  results, as well as a subsequent state of constant voltage (fixed voltage). Detection of this change in voltage allows detection of breaking of a wire in the GND line  48  by the voltage monitoring in the processing unit  43 .  
         [0029]     Also if the power source line  47  or the signal line  49  were to be completely broken, the voltage value detected by the processing unit  43  in the construction of  FIG. 3  drops to 0V, resulting in the voltage drop as shown in  FIG. 6 .  
         [0030]     If a so-called chattering occurs in which connection and breaking of wire are repeated within a very short time between the signal line  49  and the power source line  47  of the accelerator sensor  36 , the voltage value of the accelerator sensor is an alternate output of 5V and an output value corresponding to the current accelerator position, showing output behavior represented by  FIG. 7 . Further, if there is chattering between the signal line  49  and the GND line  48  of the accelerator sensor  36 , the voltage value of the accelerator sensor is an alternate output of 0V and an output value corresponding to the current accelerator position, showing output behavior represented by  FIG. 8 .  FIG. 7  and  FIG. 8  are drawings when it is assumed that chattering continues for a relatively long time.  
         [0031]     In the event of the abnormality of the accelerator sensor  36  in any of these manners, the controlling device  42  according to this invention performs a control of immediately stopping the drive of the motor  25  to stop running of the golf car  21  and performs a control of preventing stoppage of running of the golf car  21  when a normal output of the accelerator sensor  36  can be regained.  
         [0032]     How this is accomplished will now be described by reference to the control routine shown in  FIG. 4  and stored in a given memory in the controlling device  42  and executed by the processing unit  43  at set intervals for example, every 5 msec. The program starts at the step S 1  where the change in the output voltage of the accelerator sensor  36  per unit time dv/dt is calculated to judge whether or not the calculated value is larger than a predetermined threshold value per one cycle.  
         [0033]     If larger than the predetermined value (Yes), a judgment is made that there is the possibility of occurrence of an abnormality in the accelerator sensor  36  and the routine proceeds to the step S 3 . If not larger than the predetermined value (No), a judgment is made that the accelerator sensor  36  is normal and the routine proceeds to the step S 2 .  
         [0034]     Assuming that the value is No the program moves to the step S 2 . This is done because there is the possibility that because of judging time of one cycle is too short depending on the detection timing and voltage change being small, although an abnormality has occurred actually in the accelerator sensor  36 . This prevents a misjudgment that the procedure is judged to be Yes at the step S 1 , there might be a misjudgment that “the system is normal.” 
         [0035]     This is prevented at the step S 2 , where the amount of voltage change (absolute value of dv/dt) of the output of the accelerator sensor per two routine cycles is calculated in a prolonged judging time. Thus it is judged at this step whether or not the calculated value is larger than a predetermined threshold value (dv2/dt2) per two cycles.  
         [0036]     If larger than the threshold value (Yes), a judgment is made that there is the possibility of occurrence of an abnormality in the accelerator sensor  36  and the routine proceeds to the step S 3 . If not larger than the threshold value (No), a judgment is made that the accelerator sensor  36  is normal and the routine proceeds to the step S 4 .  
         [0037]     Even if a judgment is made at the steps S 1  and S 2  that there is the possibility of occurrence of an abnormality in the accelerator sensor  36 , the accelerator sensor  36  may return to a normal output condition again in case of a momentary output rise, for example, due to noise or the like. Therefore, at the step S 3  a timer is started to see the output change over time from the initial rise.  
         [0038]     The present time on the timer which has been started at the step S 3  is read at the step S 4  to judge whether or not a minute time T 1  has elapsed corresponding to the length of time required for the noise to terminate after the beginning of its development. If it is judged that time T 1  has elapsed (Yes), the routine proceeds to the step S 5 . On the other hand, if it is judged that the time has not elapsed yet (No), this routine is terminated to wait till the time T 1  has elapsed and the next routine is started.  
         [0039]     If the abnormal change in the output of the accelerator sensor  36  determined at the steps S 1  and S 2  is due to noise, for example, the output of the accelerator sensor  36  is normalized at the time the minute time T 1  has elapsed at the Step S 5  and in the mean time, the output of the acceleration sensor must be changed significantly in association with its restoration. Therefore, at this step, the amount of change in the acceleration sensor value is read to judge whether or not the change is minute.  
         [0040]     If not minute (No), that is, if it is judged that the output has returned to a normal condition because the sensor output is changed significantly by the time that a time T 1  has elapsed after the judgment of there being the possibility of occurrence of an abnormality of the accelerator sensor, the routine proceeds to the step S 6 .  
         [0041]     On the other hand, if the amount of change in the output of the accelerator sensor is minute (Yes) at the step S 5 , it is judged that the abnormality of the accelerator sensor is determined and the routine proceeds to the step S 7 .  
         [0042]     At the step S 6 , on the premise that the foregoing output change is due to noise, time measurement started at the step S 3  is stopped to clear the timer counter and terminate this routine.  
         [0043]     On the other hand, if it is not minute at the step S 7  the value of the accelerator sensor in the processing unit  43  of  FIG. 2  is replaced by a value of the 0 level for a certain specified time T 2 , to stop operation of the motor  25 , based on the judgment of the abnormality of the accelerator sensor. The “0 level” used here is set at a very small voltage value (for example, 0.5V), at which the motor is not driven, from the viewpoint of discrimination from the condition in which the driver hasn&#39;t stepped on the accelerator pedal  28  at all (in this case, the sensor output is 0V).  
         [0044]     Then at the step S 8  the duration of the accelerator sensor value of 0 level in the procedure executed at the previous step S 7  is checked to judge whether or not a certain specified time T 2  has elapsed at present. If judged that the time T 2  has elapsed (Yes), the routine proceeds to the step S 9  and if the time T 2  has not elapsed yet (No), the routine returns to the step S 5  and the foregoing procedure of 0-level replacement is maintained.  
         [0045]     At the step S 9  to avoid erroneous abnormality detection by the accelerator sensor  36 , the output value from the accelerator sensor  36 , which has been on the 0 level till now, is read again and at the same time, the operation of the golf car is set to the stop running mode. This is provisionally called a setting of condition A (or flag A).  
         [0046]     At the step S 10  a certain period of time T 3  is provided and if periods of conditions A occupy a small part within the period of time T 3 , that is, in the case of light chattering, a procedure is performed to cancel the condition A to restore a condition in which the accelerator pedal can be used (condition in which running is possible). Therefore, at this step S 10 , counting the time of condition A [n: number of times of condition A] is started, or if the counting was started at the previous routine, the number of times [n] of condition A is increased by 1. In connection with the counting of the condition A, since portions a, b, c in the models of output changes shown in  FIG. 7  and  FIG. 8  are located at positions within the period T 2  after the abnormal change and the accelerator sensor values are changed in response to the actual movement of the accelerator pedal  28 , the routine at the previous step S 5  is judged to be No, resulting in no counting of the condition A.  
         [0047]     Then at the step S 11  the number of times [n] of condition A at present is checked to judge whether or not the number of times is smaller than a specified number of times N (for example, three) within a given period T 3  as a threshold determined in advance corresponding to the abnormality of the accelerator sensor  36 . If the number of times n of condition A at present is larger than the specified number of times N (No), breaking of wire or chattering has occurred in the accelerator sensor  36  and therefore, the routine proceeds to the step S 12 .  
         [0048]     At the step S 12  a procedure for taking measures against occurrence of an abnormality of the accelerator sensor is that running of the vehicle is stopped while the warning buzzer  51  is operated to warn the driver that an abnormality has occurred in the output of the accelerator sensor. In this connection, occurrence of an error may also be preserved in an external storage device (not shown) such as a non-volatile memory.  
         [0049]     On the other hand, if at the step S 11  the number of times n of condition A at present is smaller than the specified number of times N (Yes), there is the possibility that the accelerator sensor  36  has returned to a normal operation again and therefore, the routine proceeds to the step S 13 .  
         [0050]     At the step  13  it is judged whether or not there has been any significant change in the output of the accelerator sensor  36  corresponding to the actual accelerator position from the time the condition A (restoration of the input value of the accelerator sensor) was set at the step S 9 , or whether or not it is in a condition in which the driver hasn&#39;t stepped on the accelerator pedal  28  at all (that is, in the condition of the 0-level output of the accelerator sensor  36 ).  
         [0051]     If there at the step S 13  there has been no significant change in the accelerator sensor output or no 0-level output of the accelerator sensor up to the present, this corresponds to the condition in which the sensor output is fixed to 5V or 0V as shown in  FIG. 5  and  FIG. 6  (not at the 0 level) and therefore, the routine proceeds to the step S 14  for a judgment of whether or not the given time T 3  has elapsed.  
         [0052]     On the other hand, if there has been a significant change in the accelerator output up to the present or if the output of the accelerator sensor  36  is on the 0 level (Yes) at the step S 13 , the routine proceeds to the step S 15 .  
         [0053]     At the step S 14  it is judged whether or not the given time T 3  has elapsed in the present condition of condition A. If it has not elapsed (No), the routine returns to the step S 13  and the judgment is continued of the change in the accelerator sensor, or the existence of the 0 level.  
         [0054]     On the other hand, if the given time T 3  has elapsed (Yes) at the step S 14 , this corresponds to the condition in which there has been no significant change in the accelerator sensor output or no 0 levels in spite of the elapse of this time T 3  and therefore, the abnormality of the accelerator sensor is determined an the routine proceeds to the step S 12 .  
         [0055]     If the program has moved to the step S 15  from the step S 13 , a canceling operation (for example, resetting of the flag) of the condition A set at the step S 9  is performed corresponding to the condition in which the output of the accelerator sensor  36  has returned to a normal condition. However, even if the condition A is canceled, it is possible that the accelerator sensor output changes again to 5V or 0V before the given time T 3  has elapsed as shown in  FIGS. 7 and 8 . Therefore, this routine proceeds to the step S 16 .  
         [0056]     Then at the step S 16  it is judged whether or not the given time T 3  has elapsed in the present condition of condition A, as in the case of the step S 14 . If it has not elapsed (No), the routine returns again to the step S 1  for the judgment of the change in the accelerator sensor output.  
         [0057]     On the other hand, if the given time T 3  has elapsed at the step S 16  in the condition in which the condition A is canceled (Yes), the routine proceeds to the step S 17  where, since the condition A was canceled at the step S 15 , the count number n of the condition A measured up to now is decreased and the routine returns to the step S 1 .  
         [0058]     Thus from the foregoing description of procedures executed by the processing unit  43  in the controlling device  42 , if there is an abrupt change in the accelerator sensor output (electric current value) to the controller  34 , no current is supplied to the motor  25  to replace the value by a value on the 0 level. Thus, even if there is an abrupt output change due to breaking of wire of the accelerator sensor or chattering during stoppage of the golf car  21 , for example, the golf car  21  will not start moving. Also, according to this embodiment, since the 0 level of the accelerator sensor  36  is set to be a little higher than 0V, the accelerator sensor output of 0V as a result of breaking of wire of the power source line  47  or the signal line  49  in the accelerator sensor  36  can be discriminated from the case in which the accelerator pedal  4  is not depressed. Further, in the embodiment, since the number of times of 0-level setting of the sensor output within an given time as described above is provided as a requirement for cancellation of the judgment of the accelerator sensor error, an erroneous judgment from the detection failure due to noise can be avoided.  
         [0059]     Of course those skilled in the art will readily understand that the described embodiment is only of a exemplary form that the invention may take and that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.