Abstract:
An electric powered vehicle and warning system wherein changes in operator demand and vehicle speed are monitored and warning is given to the operator when it is sensed or determined that the sensed speed may be in error.

Description:
BACKGROUND OF INVENTION  
       [0001]     This invention relates to an electrically driven vehicle and control device and method therefore.  
         [0002]     There are a wide variety of electrically driven vehicles and they are put to a wide variety of purposes and travel over or in various terrains. In many of these applications it is desirable to control their operation automatically to avoid potentially dangerous situations. By way of example, golf carts are often electrically powered for environmental and other reasons.  
         [0003]     As is well known, a golf cart travels over varying terrains having both moderate and steep grades. It is common, therefore, to provide some form of speed limiting device so that the speed will not become to grate for the condition, regardless of the operator demand. For example to avoid over speed when going down a steep grade.  
         [0004]     Such a speed limiter obviously requires a sensor for determining vehicle speed. Generally the speed sensor cooperates with a driven shaft or wheel and is comprised of a device that generates electrical pulses the number of which in a determined time interval indicates vehicle speed. Such a system is shown in Japanese Published application Hei 10-309005 (A).  
         [0005]     However both the environment over which the vehicle operates and other factors such as shocks encountered when riders get on or off the vehicle or place or remove loads from the vehicle may cause the speed sensor or its connections to become damaged or fail totally. This obviously can cause false or incorrect signals resulting in an undesirable condition.  
         [0006]     It is, therefore, a principal object of this invention to provide an apparatus and methodology that will monitor the output of a vehicle speed sensor and compare it with the operator&#39;s speed demands and give a warning to the operator when the sensor output is deemed to be erroneous.  
       SUMMARY OF THE INVENTION  
       [0007]     A first feature of the invention is adapted to be embodied in a vehicle having a propulsion device driven by an electric motor. The vehicle has a rider operated speed control for controlling the driving speed of the electric motor. There is also a device for providing signals indicating the vehicle traveling speed. Devices sense both changes in the position of the rider operated speed control and changes in the indicated vehicle speed in respective time periods. A warning operation is performed when the vehicle speed change in the time period is equal to a first value or greater and the change in position of the rider operated speed is a second value or less.  
         [0008]     Another feature of the invention is adapted to be embodied in a warning method for a vehicle having a propulsion device driven by an electric motor. The vehicle has a rider operated speed control for controlling the driving speed of the electric motor. There is also a device for providing signals indicating the vehicle traveling speed. The method comprises the steps of sensing both changes in the position of the rider operated speed control and changes in the indicated vehicle speed in respective time periods. A warning operation is performed when the vehicle speed change in the time period is equal to a first value or greater and the change in position of the rider operated speed is a second value or less.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a partially schematic top elevational view of an electric powered vehicle constructed and operated in accordance with the invention.  
         [0010]      FIG. 2  is a schematic electrical diagram of the vehicle and its control.  
         [0011]      FIG. 3  is a diagram showing the conditions for determining vehicle speed sensor variations and operator vehicle control position variations on increases in speed determination.  
         [0012]      FIG. 4  is a diagram showing the conditions for determining vehicle speed sensor variations and operator vehicle control position variations on decreases in speed determination.  
         [0013]      FIG. 5  is a block diagram showing the control methodology. 
     
    
     DETAILED DESCRIPTION  
       [0014]     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.  
         [0015]     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.  
         [0016]     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 .  
         [0017]     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 .  
         [0018]     A vehicle speed sensor  39  is provided in association with the electric motor  25  and generates a high-frequency pulse signal according to the rotational speed of the motor  25  and the signal is inputted into the controller  34 . Alternatively the vehicle speed sensor  39  may be associated with any vehicle wheel or other shaft that drives a wheel such as a rear axle  41 .  
         [0019]     The configuration of a drive control device according to the present invention for the golf cart  21  will now be described by reference to  FIG. 2 . The drive control device is comprised mainly the speed sensor  39  and the controller  34  for detecting a sensor failure based on the output condition of the speed sensor  39  and performing the processes described later by reference to  FIGS. 3-5 .  
         [0020]     As has been noted, the accelerator opening degree sensor  36  is operatively connected to the accelerator pedal  28  and outputs a voltage corresponding to the amount the accelerator pedal is depressed by the driver to the controller  34 . The controller  34  has a processing unit (MPU)  42 , indicated by the broken line box, that receives a speed signal (high frequency pulse) and an accelerator position signal (voltage) from the speed sensor  39  and the accelerator opening degree sensor  36 , respectively. The processing unit  42  performs calculations for driving the motor  25  through a motor drive circuit  43  for outputting current for driving the motor  25 . Also the processing unit  42  transfers data to a memory (EEPROM)  44  for storing data, as will be described later.  
         [0021]     A power source circuit  45  supplies power from the batteries  37  to the processing unit (MPU)  42 , the motor drive circuit  43 , and the accelerator opening degree sensor  36 . In this embodiment, the power source circuit  45  supplies 48 volts to the motor drive circuit  43  and 5 volts to the processing unit  42  when the main switch  32  is turned on.  
         [0022]     Signals from the accelerator opening degree sensor  36  are delivered to the processing unit  42  via a signal line  46 , and signals from the speed sensor  39  are delivered to the processing unit  42  via a signal line  47 .  
         [0023]     The processing unit  42 , as indicated by the boxes in  FIG. 2 , performs a speed sensor failure determination process, and obtains an average of accelerator opening degree sensor values (accelerator opening degree sensor averaging process), calculates a motor driving current and a duty ratio using the accelerator average value and provides them as PWM outputs to the motor drive circuit  43 . The motor drive circuit  43  has a function of detecting the motor driving current currently outputted (current detection circuit), and the detected motor current value is provided as feedback to the processing unit  42 .  
         [0024]     The system also has a device for issuing a warning to the operator of the golf cart  21  such as an alarm buzzer  48  for warning the driver when the speed sensor has a failure determined as will be described later by reference to  FIGS. 3-5 . The alarm buzzer  48  is connected to the processing unit  42 , which performs a sensor failure determination process.  
         [0025]     If the signal line  47  connected to the speed sensor  39  has a break or the speed sensor  39  shows a value different from the actual running speed due to the influence of noise or other disturbances, the controller  34  of this embodiment can find the failure immediately, and stop the golf cart  21  and warns the driver of the failure with the alarm buzzer  48 .  
         [0026]     More specifically, the controller  34  monitors the changes in the vehicle speed value obtained from the speed sensor  39  compared with changes in the displacement of the accelerator pedal  28 , that is, the output value from the accelerator opening degree sensor  36  and the direction of the accelerator pedal  28  (acceleration or deceleration). Then, when the change in the vehicle speed within a short period of time does not correspond to the change in the output from the accelerator opening degree sensor  36 , the controller  34  determines that the speed sensor  39  has a failure.  
         [0027]     Referring next to  FIG. 3 , this schematically illustrates the regions in which the speed sensor is determined to be normal or abnormal relation to the change in the accelerator opening degree sensor output and the change in the vehicle speed during acceleration. In this embodiment, two threshold values Vup 1  and Vup 2  are set in the increase of the vehicle speed and a threshold value Aup is set in the increase of the accelerator opening degree sensor output as shown in the drawing, and the speed sensor is determined to be normal or abnormal based on a plurality of operation regions indicated at “a” to “f” and defined by the threshold values Vup 1 , Vup 2  and Aup.  
         [0028]     In a similar manner  FIG. 4  schematically illustrates the regions in which the speed sensor is determined to be normal or abnormal in the relationship between the change in the accelerator opening degree sensor output and the change in the vehicle speed during deceleration. As in the case of acceleration, two threshold values Vdown 1  and Vdown 2  are set in the decrease of the vehicle speed and a threshold value Adown is set in the decrease of the accelerator opening degree sensor output. The speed sensor is determined to be normal or abnormal based on a plurality of operation regions indicated by “g” to “l” and defined by the threshold values Vdown 1 , Vdown 2  and Adown.  
         [0029]     The control routine will now be described by reference to  FIG. 5 . The program for performing the flowchart is stored in a memory in the controller  34  and executed every predetermined time period t 1  (5 ms. for example) by the processing unit  42 . The program starts at the step S 1  where the displacement of the accelerator pedal position per one cycle of this routine, that is, the moving average Aave of the changes in the accelerator opening degree sensor outputs within a short period of time t 1  is calculated.  
         [0030]     Then at the step S 2  it is determined whether the accelerator opening degree sensor moving average Aave obtained in step S 1  is a positive value, which indicates that the vehicle is accelerating, or a negative value, which indicates that the vehicle is decelerating. If the accelerator opening degree sensor moving average Aave is greater than 0 (Yes), it is determined that the vehicle is accelerating, and the routine goes to step S 3 . If the accelerator opening degree sensor moving average Aave is smaller than 0 (No), it is determined that the vehicle is decelerating, and the routine goes to step S 7 .  
         [0031]     Assuming that the operator is calling for an increase in speed, at the step S 3  it is determined if vehicle is operating in a generally allowable acceleration range. Thus, a threshold value Vup 1  is set as a first acceleration threshold value and the vehicle speed is obtained from the speed sensor  39 . Then, it is determined whether the change AV in the vehicle speed within the short period of time t 1  (acceleration) is greater than the threshold value Vup 1 . If the change ΔV is greater than the threshold value Vup 1  (Yes), the vehicle determines that there is a possibility that the speed sensor has a failure and the routine goes to step S 4 . If the change ΔV is smaller than the threshold value Vup 1  (No), it is determined that the output from the speed sensor is normal. Then, the routine skips the following steps and goes to step S 11 . That is, within the regions “a” and “b” in  FIG. 3  described before correspond to this.  
         [0032]     At the step S 4  id is determined whether the driver has depresses the accelerator pedal  28  quickly or relatively slowly depending on the conditions under which the golf cart is used. Here, it is determined whether the accelerator was depressed quickly. More specifically, a threshold value Aup of the increase in the accelerator opening degree sensor output is set as a boundary between quick and slow depressions, and it is determined whether the moving average Aave calculated in step S 1  is greater than the threshold value Aup. If the moving average Aave is greater than the threshold value Aup (Yes), there is a possibility that the accelerator pedal was depressed quickly by the driver. In this case, the routine goes to step S 5 . If the moving average Aave is smaller than the threshold value Aup (No), since the increase in the accelerator opening degree sensor output is small although the golf cart  21  is accelerated quickly, it is determined that the output from the speed sensor  39  is abnormal. Then, the routine skips the following step S 5  and goes to step S 6 . This is the vehicle condition corresponding to the region “c” in  FIG. 3 .  
         [0033]     If the operator has depressed the accelerator pedal  28  quickly, at the step  5  it is determined if the vehicle speed calculated from the output value from the speed sensor  39  may show an abnormal value because of a failure of the speed sensor  39 . Thus, it is determined whether the change ΔV in the vehicle speed calculated in the process of step S 3  is attributed to a quick depression of the accelerator pedal. This is done by setting a second threshold value Vup 2  is set as an increase in the speed based on an appropriate change in the vehicle speed corresponding to such a “quick depression” obtained in advance by experiment. Then it is determined whether the change ΔV in the vehicle speed (acceleration) is smaller than this second threshold value Vup 2 .  
         [0034]     If at the step S 5  the change ΔV is smaller than the second threshold value Vup 2  (Yes), it is determined that this increase in the vehicle speed is attributed to a “quick depression” of the accelerator pedal by the driver and the output from the speed sensor  39  is normal. Then, the routine skips step S 6  and goes to step S 11 . This is the operating condition corresponding to the region “d” in  FIG. 3 .  
         [0035]     However if at the step S 5  it is determined that the change ΔV is greater than the second threshold value Vup 2  (No), that is, when the output from the accelerator opening degree sensor  36  shows a rapid increases (since the result is “Yes” in step S 4 ) and the change ΔV in the vehicle speed (acceleration) obtained from the speed sensor  39  is too large even if the increase is taken into account, it is determined that there is a possibility that the speed sensor has a failure.  
         [0036]     In this case, the routine goes to step S 6 . This is the vehicle condition corresponding to the regions “e” and “f” in  FIG. 3 . The failure determination in step S 5  is made by comparing the change in the vehicle speed and the second threshold value Vup 2  regardless of the change in the output from the accelerator opening degree sensor  36 . Thus, when the accelerator opening degree sensor  36  has a failure and the information from the accelerator opening degree sensor  36  is unreliable, it is possible to make a determination whether the speed sensor  39  has a failure. This is determined at the step S 11 , as will be described later. In this case, a vehicle speed abnormal increase flag Finc is set to 1 and a vehicle speed abnormal decrease flag Fdec is cleared to 0. At the same time, a timer for counting the time which has elapsed after the flag setting is started.  
         [0037]     Returning back now to step S 2 , if the determination is made that the operator of the cart  21  is calling for deceleration, the program moves to the step S 7  where it is determined if the cart  21  has a generally allowable deceleration range, the same as was done in the case of accelerating. Thus, a threshold value Vdown 1  is set as a first deceleration threshold value and the vehicle speed is obtained from the speed sensor  39 . From this information, it is determined whether the change ΔV in the vehicle speed within the short period of time t 1  (deceleration) is greater than the threshold value Vdown 1 .  
         [0038]     If the change ΔV is greater than the threshold value Vdown 1  (Yes), the controller  34  determines that there is a possibility that the speed sensor has a failure and the routine goes to step S 8 . If the change ΔV is smaller than the threshold value Vdown 1  (No), it is determined that the output from the speed sensor  39  is normal. Then, the routine skips the following step S 8  and goes directly to step S 10 . That is, the cart  21  is operating in the regions “g” and “h” in  FIG. 4 .  
         [0039]     The driver releases his/her foot from the accelerator pedal  28  depending on the running conditions. However, when the driver quickly releases the accelerator pedal  28  for a very short period of time such as 5 msec during running, the vehicle speed does not suddenly decreased to zero.  
         [0040]     This condition is determined at the step S 8 . Here, in order to determine whether the driver quickly released the accelerator pedal  28 , it is determined whether the moving average Aave of the accelerator opening degree sensor  36  calculated in step S 1  is greater than a predetermined decrease threshold value Adown indicating an appropriate decrease in the accelerator opening degree sensor output.  
         [0041]     If the moving average Aave of the accelerator opening degree sensor  36  is greater than the decrease threshold value Adown (Yes), there is a possibility that the driver quickly released the accelerator pedal  28 . Then, the routine goes to step S 9 . If the moving average Aave of the accelerator opening degree sensor  36  is smaller than the decrease threshold value Adown (No), that is, when the accelerator opening degree sensor output shows a small decrease (that is, gentle deceleration) although it is determined that the golf cart  21  was quickly decelerated, it is determined that the output from the speed sensor  39  is abnormal. Then, the routine skips step S 9  and goes directly to step S 10 . This is the vehicle condition corresponding to the region “i” in  FIG. 4 .  
         [0042]     If the program has moved to the step S 9  from the step S 8  because the driver released the accelerator pedal  28  to decelerate the vehicle quickly, the vehicle speed will not decreased to zero within a short period of time. However, if the signal line  47  of the speed sensor  39  has a break, the output from the speed sensor  39  is fixed to a high or low level and, consequently, the calculated vehicle speed becomes zero. Thus at the step S 9  it is determined whether the change ΔV calculated in the process in step S 3  is attributed to a release of the accelerator pedal. More specifically, a second threshold value Vdown 2  is set as a decrease in the speed based on an appropriate change in the vehicle speed corresponding to such a “quick release” obtained in advance by experiment, and it is determined whether the change ΔV in the vehicle speed (deceleration) is smaller than the second decrease threshold value Vdown 2 .  
         [0043]     If the change ΔV is smaller than the second decrease threshold value Vdown 2  (Yes), it is determined that this decrease in the vehicle speed is attributed to a “quick release” of the accelerator pedal by the driver and the output from the speed sensor  39  is normal. Then, the routine skips step S 10  and goes directly to step S 11 . This is the vehicle condition corresponding to the region “j” in  FIG. 4 .  
         [0044]     However if the change ΔV is greater than the second decrease threshold value Vdown 2  (No), that is, when the output from the accelerator opening degree sensor  36  shows a rapid decreases (since the result is “Yes” in step S 8 ) and the change ΔV in the vehicle speed (deceleration) obtained from the speed sensor  39  is too large even if the decrease is taken into account, it is determined that there is a possibility that the speed sensor has a break. Then, the routine goes to step S 10 . This is the vehicle condition corresponding to the regions “k” and “l” in  FIG. 4 . The failure determination in step S 9  is made by comparing the change in the vehicle speed and the second threshold value Vdown 2  regardless of the change in the output from the accelerator opening degree sensor  36  as in the case with step S 5 . Thus, when the accelerator opening degree sensor  36  has a failure and the information from the accelerator opening degree sensor  36  is unreliable, it is possible to make a determination whether the speed sensor  39  has a failure.  
         [0045]     At the step S 10 , the vehicle speed abnormal increase flag Finc is cleared to 0 and a vehicle speed abnormal decrease flag Fdec is set to 1 in contrast to step S 6 . At the same time, the timer for counting the time which has elapsed after the flag setting is started.  
         [0046]     Referring now to the condition the routine has moved to the step S 11  from any of steps S 3 , S 5 , S 6 , S 7 , S 9  or S 10 , the current set or clear state of the flags is checked. In this program, the vehicle speed abnormal increase flag Finc and the vehicle speed abnormal decrease flag Fdec are set or cleared depending on the change in the speed within a short period of time.  
         [0047]     As has already been noted, if the signal line  47  of the speed sensor  39  has a break and the output pulse from the sensor  39  suddenly disappears (the vehicle speed becomes zero), since no change in the speed is detected in the routine after the flag Finc or Fdec has been set to 1 at the time of a change in the speed, “No” is selected in step S 3  or S 7  and the routine has gone to step S 11 . If the vehicle speed abnormal increase flag Finc or the vehicle speed abnormal decrease flag Fdec has not set (No), the routine skips the following step S 12  and comes to an end.  
         [0048]     However, if the vehicle speed abnormal increase flag Finc or the vehicle speed abnormal decrease flag Fdec is set to 1 (Yes), the routine goes to step S 12 . In this step, a predetermined time period t 2  (for example, a time period corresponding to 200 cycles when the execution interval of this routine is 5 msec) is set as a flag set continuation time. Then it is determined whether the time period t 2  has elapsed after the first flag setting. If the time period t 2  has elapsed after the flag setting (Yes), the routine goes to step S 14 . If the time period t 2  has not elapsed yet (No), the routine goes to step S 13 .  
         [0049]     When the signal line  47  of the speed sensor  39  has a break or the connection is interrupted repeatedly the vehicle speed as the calculation product shows sudden changes within a short period of time. Thus, at the step S 13  it is determined whether the vehicle speed abnormal increase flag Finc or the vehicle speed abnormal decrease flag Fdec is set N times, that is, so many times that it is determined that chattering is occurring, within the time period t 2 . If the vehicle speed abnormal increase flag Finc or the vehicle speed abnormal decrease flag Fdec is not set N times (No), the routine is terminated.  
         [0050]     Returning now to the step S 12 , if the result was positive (yes) the program moves to the step S 14 . When the number of times the vehicle speed abnormal increase flag Finc or the vehicle speed abnormal decrease flag Fdec is set does not reach the number N within the time period t 2  and there is a large change in the speed during that period (within the time period t 2  after the first flag setting), it is considered that the flag was set because the speed sensor  39  picked up noise. Thus, in this step, it is determined whether the flag setting is attributed to noise by comparing the change ΔV in the speed obtained in step S 3  and a preset small value. If there is a change in the speed (No), it is determined that the flag setting is caused by noise, and the routine goes to step S 16 .  
         [0051]     The flag setting caused by noise is not a failure of the speed sensor  39 . Thus, it is determined at the step S 16  that the speed sensor is normal and the vehicle speed abnormal increase flag or the vehicle speed abnormal decrease flag, which has been set, is reset and the timer for counting the time which has elapsed after the flag setting is cleared. Then, the routine is terminated.  
         [0052]     However if at the step S 14  that the change in the speed is small (Yes), it is considered that the signal line  47  of the speed sensor  39  has a break, and the routine goes to step S 15  where a speed sensor failure handling process is executed. For example, the calculation of motor current in the processing unit  42  is stopped to stop the vehicle, and the alarm buzzer  48  shown in  FIG. 2  is activated to inform the driver of the sensor failure. Also, the occurrence of the sensor failure is recorded in an EEPROM  44  of the controller  34  as a failure history of the golf cart  21 .  
         [0053]     The foregoing steps are executed in the processing unit  42  of the control device  34  according to this embodiment. In this embodiment, the change in the vehicle speed obtained from the speed sensor  39  is monitored based on the change in the output value from the accelerator opening degree sensor  36  and the direction of the accelerator pedal (acceleration or deceleration) every short period of time. Then, when the vehicle speed detected by the speed sensor  39  has a change greater than a preset value, and when the vehicle speed does not have a change for a predetermined period of time after the change (Yes in step S 14 ) or the number of times of changes in the vehicle speed within a predetermined period of time is greater than a preset value (Yes in step S 13 ), it is determined that the speed sensor  39  has a failure. Then, the vehicle is stopped and the occurrence of the failure is informed to the driver. Thus, the golf cart, unlike a conventional golf cart, does not fall into a golf cart speed control mode based on erroneous information and is not decelerated so quickly that the driver feels uncomfortable. Further, in this embodiment, as a condition for determining whether or not the speed sensor has a failure, a change in the vehicle speed after a predetermined period of time after a speed sensor failure flag has been set is checked and, if there is a speed change, the speed sensor failure flag is reset. Thus, an erroneous failure handling process caused by noise picked up by the sensor can be excluded.  
         [0054]     Although the present invention has been described taking a drive control device which determines a failure of the speed sensor based on the relationship between the change in the vehicle speed and the change in the output from an accelerator opening degree sensor, the present invention is not limited to the example and can be variously modified. For example, the numbers of threshold values as shown in  FIG. 3  and  FIG. 4  may be increased to divide the regions for use in the determination of a failure of the speed sensor into smaller regions. In the flowchart in the embodiment, the change in the vehicle speed calculated from the speed sensor output value is used as one parameter for determination of a failure of the speed sensor. In addition to this, a step in which the speed sensor  39  detects the current vehicle speed and the calculation of the vehicle speed is stopped if the pulse frequency (vehicle speed) obtained from the speed sensor output value exceeds the maximum motor rotational speed (that is, the maximum vehicle speed) obtained from the battery voltage may be provided. Of course those skilled in the art will readily understand that the described embodiments are only exemplary of forms 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.