Abstract:
A method of limiting speed of a light-weight utility vehicle is provided. The method includes receiving a terrain roughness signal generated from a motion sensor. The signal indicates a roughness of a terrain over which the utility vehicle is traversing. The method additionally includes determining a peak-to-peak amplitude of the terrain roughness signal and limiting the speed of the utility vehicle if the peak-to-peak amplitude is greater than a maximum threshold.

Description:
FIELD 
       [0001]    The present teachings relate to limiting the speed of a vehicle in accordance with terrain operating conditions. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0003]    It is common for operators of electric golf cars and utility vehicles to drive these vehicles into areas of rough terrain. For example, an operator of a golf car may choose to follow his errant tee shot into the woods or rough. Traveling in areas of rough terrain at high speeds causes damage to the vehicle suspension, chassis, and can be uncomfortable or even dangerous for passengers. 
         [0004]    Conventional methods of preventing such damage rely on golf car operators to recognize rough terrain conditions and reduce vehicle speed accordingly. If and when an operator determines the terrain is too rough for the existing speed, the operator may not react in sufficient time to prevent adverse consequences. Automatically detecting rough terrain conditions and limiting vehicle speed during vehicle travel through such terrains will help to protect vehicle components and passengers. 
       SUMMARY 
       [0005]    Accordingly, a method for limiting the speed of a light-weight utility vehicle is provided. The method includes receiving a terrain roughness signal generated from a motion sensor. The terrain roughness signal is representative of a roughness of a terrain over which the utility vehicle is traversing. The method additionally includes determining a peak-to-peak amplitude of the terrain roughness signal and limiting speed of the vehicle if the peak-to-peak amplitude is greater than a maximum threshold. 
         [0006]    In other features, a system for limiting the speed of a light-weight utility vehicle while driving on rough terrain is provided. The system includes a motion sensor mounted to a suspension member of the utility vehicle. The motion sensor generates a terrain roughness signal that varies in accordance with a deflection of the suspension member. A controller receives the terrain roughness signal, determines a peak-to-peak amplitude of the terrain roughness signal and controls the speed of a vehicle motor based on the amplitude. 
         [0007]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0008]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present teachings in any way. 
           [0009]      FIG. 1  is a block diagram illustrating an exemplary vehicle including a terrain monitoring and motor control system, in accordance with various embodiments. 
           [0010]      FIG. 2  is a side view of a front wheel suspension, knuckle and hub assembly of the exemplary vehicle shown of  FIG. 1  including a motion sensor of the terrain monitoring and motor control system, in accordance with various embodiments. 
           [0011]      FIG. 3  illustrates an exemplary terrain roughness signal generated by the motion sensor mounted to the front wheel suspension, knuckle and hub assembly shown in  FIG. 2 , in accordance with various embodiments. 
           [0012]      FIG. 4  is a flowchart illustrating a speed limiting application of the terrain monitoring and motor control system of  FIG. 1 , in accordance with various embodiments. 
           [0013]      FIG. 5  is a flowchart illustrating a speed limiting application of the terrain monitoring and motor control system of  FIG. 1 , in accordance with various other embodiments. 
           [0014]      FIG. 6  is a flowchart illustrating a speed limiting application of the terrain monitoring and motor control system of  FIG. 1 , in accordance with yet various other embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The following description is merely exemplary in nature and is in no way intended to limit the present disclosure, application, or uses. For purposes of clarity, like reference numbers will be used in the drawings to identify like elements. 
         [0016]      FIG. 1  is a block diagram illustrating components of a non-limiting, exemplary vehicle  10 , including a terrain monitoring and motor control system  11 , in accordance with various embodiments. As can be appreciated, vehicle  10  can be any vehicle type including but not limited to, gasoline, electric, and hybrid. The vehicle  10  includes a motor  12  that is operatively coupled to a drive shaft  14  operatively coupled to rear axles  17 A and  17 B, via a differential  18 . The vehicle  10  additionally includes a pair of rear wheels  16 A and  16 B that are operatively coupled to the rear axles  17 A and  17 B such that the motor  12  drives, i.e., provides torque to, the rear wheels  16 A and  16 B via the drive shaft  14 , differential  18  and axles  17 A and  17 B. The motor  12  can be any known motor, and/or motor generator technology, including, but not limited to, gas powered engines or motors, AC induction machines, DC machines, synchronous machines, and switched reluctance machines. The vehicle  10  further includes a pair of front wheels  24 A and  24 B operatively coupled to a respective pair of wheel knuckle and hub assemblies  26 A and  26 B that allow the front wheels  24 A and  24 B to rotate and laterally pivot. The wheel knuckle and hub assemblies  26 A and  26 B are operatively mounted to a pair of respective suspension arms  30 A and  30 B that operatively connect to respective vehicle  10  frame members  28 A and  28 B. 
         [0017]      FIG. 2  illustrates an exemplary front wheel suspension arm  30 A and knuckle and hub assembly  26 A, in accordance with various embodiments. The suspension arm  30 A is rotatably supported by a pin  32  to frame  28 A (shown in  FIG. 1 ) to permit a steering knuckle  34  and a wheel hub  36  to pivot at a distal end of suspension arm  30 A, as illustrated by a wheel deflection arc ‘L’. A spring/shock absorber assembly  44  couples to knuckle  34  and includes a coil  40  and a shock absorber  47 . Coil  40  and shock absorber  42  deflect to allow motion of spring/shock absorber assembly  44  in each of a compression direction ‘M’ and an expansion direction ‘N’. Shock absorber  42  can be fixedly connected at mounting pin  46  to a support structure (not shown) of vehicle  10 . Front wheel  24 A is fixedly mounted to wheel hub  36  which rotatably mounts to a shaft  47  along hub rotation axis  48 . A motion sensor  50  mounts to suspension arm  30 A and detects movement or deflection of arm  30 A along deflection arc ‘L’. Motion sensor  50  can be any known sensing device in the art including, but not limited to, a Hall-effect transducer and a strain gage. 
         [0018]    Referring now to  FIGS. 1   2 , and  3 , motion sensor  50  generates a terrain roughness signal  52  that varies in accordance with the movement of suspension arm  30 A along arc ‘L’. As can be appreciated, suspension arm  30 B and front wheel knuckle and hub assembly  26 B can be a mirror image of suspension arm  30 A and front wheel knuckle and hub assembly  26 A. Thus, a motion sensor  54 , coupled to the suspension arm  30 B also generates a terrain roughness signal  56  which varies in accordance with the movement of suspension arm  30 B along arc ‘L’. 
         [0019]    The vehicle  10  includes an accelerator assembly that includes an accelerator position sensor  58  and an accelerator pedal  60 . Accelerator position sensor  58  generates an accelerator signal  62  based on a sensed position of accelerator pedal  60 . The vehicle  10  also includes a brake pedal assembly that includes a brake pedal  64  and a brake position sensor  66 . Brake position sensor  66  generates a brake signal  68 , based on a sensed position of brake pedal  64 , that controls the operation of a brake  70  coupled to motor  12 . More particularly, a controller  72  receives the brake signal  68  and generates control signals to brake  70  to vary the braking force applied to motor  12 . 
         [0020]    Additionally, in accordance with various embodiments, the controller  72  controls voltage, current, and/or power provided to motor  12  from a battery pack  74  based on various signal inputs, such as accelerator signal  62  and/or terrain roughness signals  52  and  56 . The battery pack  74  can include any known battery technology, including but not limited to lead acid, lithium ion, and lithium polymer batteries. 
         [0021]    As can be appreciated, controller  72  may be any known microprocessor, controller, or combination thereof known in the art. In various embodiments, controller  72  includes a microprocessor having read only memory (ROM), random access memory (RAM), and a central processing unit (CPU). Microprocessor may include any number of software control modules that provide the functionality for speed limiting of vehicle  10 . In various other embodiments, controller  72  is an application specific integrated circuit (ASIC), an electronic circuit, a combinational logic circuit and/or other suitable components that provide the speed limiting functionality. 
         [0022]    As can be appreciated, the functionality of controller  72  may be partitioned into one or more controllers (not shown). For example, a controller (not shown) containing a microprocessor may be located external to controller  72 . The external controller may process accelerator signal  62  and brake signal  68  and controller  72  may control motor  12  and brake  70  based on processed signals received from the external controller. 
         [0023]      FIG. 3  illustrates an exemplary terrain roughness signal  52  or  56  generated from motion sensor  50  or  54 , in accordance with various embodiments. It should be understood that motions sensor  50  and  54  operate in substantially identical manners with regard to the respective suspension arms and knuckle and hub assemblies  30 A/ 26 A and  30 B/ 26 B. Accordingly, for simplicity and clarity, the operation of motion sensors  50  and  54  will be described and illustrated in  FIGS. 3 through 6  with respect to only motion sensor  50  and suspension arm and knuckle and hub assembly  30 A/ 26 A. Motion sensor  50  generates terrain roughness signal  52  that varies in accordance with the deflection of suspension arm  30 A along arc ‘L’. As the terrain becomes rough, the peak-to-peak amplitude of terrain roughness signal  52  becomes greater. An exemplary terrain roughness signal  52  generated from the vehicle  10  traversing a generally smooth terrain, where suspension arm  30 A deflection is small, is shown generally at  80 . As the roughness of the terrain traversed by the vehicle  10  increases, the peak-to-peak amplitude of roughness signal  52  will also increase. Similarly, as the terrain roughness decreases, e.g., smooths out, the peak-to-peak amplitude of roughness signal  52  will decrease or smooth out. An exemplary terrain roughness signal  52  generated from the vehicle  10  traversing a substantially rough terrain, where the deflection of suspension arm  30 A is significantly greater when traversing a generally smooth terrain, is shown generally at  82 . Once the peak-to-peak amplitude of the terrain roughness signal  52  exceeds a selectable threshold X, controller  72  generates output signals to motor  12  to limit the speed of vehicle  10 . 
         [0024]    In various embodiments, as shown generally at  83 , if the peak-to-peak amplitude of terrain roughness signal  52  exceeds a second selectable threshold M, indicating a severe change in terrain roughness, controller  72  applies brake  70  to limit the speed of vehicle  10 . Once a smooth terrain is detected, controller  72  adjusts vehicle speed to the speed indicated by accelerator pedal  60  via motor  12 . It will be understood, that various embodiments may provide for vehicle  10  speed control only by controlling either motor  12  speed or braking force or in the opposite order as described above. 
         [0025]      FIG. 4  is a flowchart illustrating the operation of the terrain monitoring and motor control system  11  based on the sensed terrain that vehicle  10  is traversing, in accordance with various embodiments. As the vehicle  10  traverses the terrain, the suspension arm  30 A will move back and forth, i.e., up and down, along arc L in correlation to the roughness of the terrain. Simultaneously, the motion sensor  50 , mounted to the suspension arm  30 A, will move back and forth along arc L in correlation to the roughness of the terrain being traversed. As described above, the motion sensor  50  generates the terrain roughness signal  52  that is indicative of the terrain roughness. 
         [0026]    The roughness signal  52  is communicated to and processed by the controller  72  to monitor the peak-to-peak amplitude of the terrain roughness signal  52 , at  100 . By way of non-limiting example, terrain roughness signal  52  is processed. As can be appreciated, various embodiments can limit speed based on processing one or more terrain roughness signals, for example terrain roughness signals  52  and  56  can be substantially simultaneously processed. If the peak-to-peak amplitude between of terrain roughness signal  52  is greater than a maximum threshold X, as illustrated at  110 , the speed of vehicle  10  is limited, as illustrated at  120 . The maximum threshold X can be any predetermined value based on attributes of at least one of arm  30 A and motion sensor  50  such as, the position of the motion sensor  50 , the length of the suspension arm  30 A and/or motion and sensor resolution. If the peak-to-peak amplitude of terrain roughness signal  52  is less than the maximum threshold X, the terrain roughness signal  52  is continually monitored, as illustrated at  100 . 
         [0027]    In various other embodiments, the terrain roughness signal  52  generated from motion sensor  50  can be filtered in order to determine an average of peak-to-peak amplitudes value over a selected time period. Averaging the peak-to-peak values of terrain roughness signal  52  over a selected time period filters errors due to noise in the terrain roughness signal  52 . Accordingly, if the average of the peak-to-peak amplitudes is greater than a maximum threshold X, the speed of vehicle  10  is limited, as illustrated at  120 . The maximum threshold X can be a selectable value based on attributes of at least one of the suspension arm  30 A and the motion sensor  50 , as discussed above. 
         [0028]    After limiting the speed of vehicle  10 , as illustrated at  120 , the terrain roughness signal  52  continues to be processed to determine a subsequent peak-to-peak amplitudes of terrain roughness signal  52 , as illustrated at  130 . If the peak-to-peak amplitude is subsequent less than a minimum threshold Y (shown in  FIG. 3 ), as illustrated at  140 , the speed of vehicle  10  is adjusted back to a desired speed that is indicated by accelerator signal  62 , as illustrated at  150 . 
         [0029]    Adjustments to the speed of vehicle  10 , as controlled by the terrain monitoring and motor control system  11 , can be made at a predetermined rate to effect a smooth speed adjustment. If the peak-to-peak amplitude is greater than or equal to the minimum threshold Y, as indicated at  140 , the speed of vehicle  10  is continually limited, as indicated at  120 , until the peak-to-peak amplitude is below the minimum threshold Y, indicating that the terrain being traversed by the vehicle  10  is generally smooth. 
         [0030]      FIG. 5  is a flowchart illustrating the operation of the terrain monitoring and motor control system  11  based on the sensed terrain that vehicle  10  is traversing, in accordance with various other embodiments. If the speed of vehicle  10  exceeds a selectable limit Z, as illustrated at  200 , the controller  72  adjusts the voltage, current, and/or power provided to motor  12  such that the speed of vehicle  10  is rapidly reduced to or below the limit Z, as illustrated at  210 . If the speed vehicle  10  is less than the selectable limit Z, as illustrated at  200 , the controller  72  maintains the voltage, current, and/or power provided to the motor  12 , such that the speed of vehicle  10  remains at or below the selectable limit Z, as indicated at  220 . The selectable limit Z can be determined based on a constant value for all levels, or severity, of terrain roughness, or can vary based on a value of the peak-to-peak amplitude of the terrain roughness signal  52 , indicating the roughness of the terrain over which vehicle  10  is traversing. 
         [0031]      FIG. 6  is a flowchart illustrating operation of the terrain monitoring and motor control system  11  to limit the speed of the vehicle  10  by controlling motor  12  and brake  70  of vehicle  10 , in accordance with yet various other embodiments. Terrain roughness signal  52  generated from motion sensor  50  is processed to determine the peak-to-peak amplitude of the roughness signal  52 , as illustrated at  300 . By way of non-limiting example, only terrain roughness signal  52  is processed. As can be appreciated, various embodiments can limit speed based on processing one or more terrain roughness signals, for example terrain roughness signals  52  and  56  can be substantially simultaneously processed. 
         [0032]    If the peak-to-peak amplitude of the roughness signal  52  is greater than the maximum threshold X, as illustrate at  310 , the speed of vehicle  10  is limited, as illustrated at  320 . As described above, the maximum threshold X can be a selectable value based on attributes of at least one of the suspension arm  30 A and the motion sensor  50 . The speed of vehicle  10  can be limited, as illustrated at  320 , by controlling voltage, current, and/or power provided to motor  12  such that the speed of vehicle  10  is not greater than a selectable limit. In various embodiments, the operations shown in  FIG. 5  can be implemented similarly to limit the speed of vehicle  10 , as illustrated at  320 . If the peak-to-peak amplitude is less than or equal to the maximum threshold X, as illustrated at  310 , terrain roughness signal  52  continues to be processed, as illustrated at  300 . 
         [0033]    In various other embodiments, the terrain roughness signal  52  generated from motion sensor  50  can be processed by the controller  72  in order to determine an average of peak-to-peak amplitude values for a selected time period. Averaging the peak-to-peak values of terrain roughness signal  52  over a selected time period filters error due to noise in terrain roughness signal  52 . If the average of the peak-to-peak amplitude values is greater than the maximum threshold X, the speed of vehicle  10  is limited, as illustrated at  120 . As described above, the maximum threshold X can be a selectable value based on attributes of at least one of the suspension arm  30 A and the motion sensor  50 . 
         [0034]    With further reference to  FIG. 6 , if the peak-to-peak amplitude of the terrain roughness signal  52  is greater than a second maximum threshold M, as illustrated at  330 , the brake  70  can be commanded to an apply state, as illustrated at  340 . After limiting the speed and applying brake  70 , the controller  72  continues to monitor the terrain roughness signal  52  in order to determine subsequent peak-to-peak amplitudes of the terrain roughness signal  52 , as illustrated at  350 . If subsequent peak-to-peak amplitudes is less than the minimum threshold Y, as illustrated at  360 , the brake  70  is commanded to a disengaged state, as illustrated at  370 , and the speed of vehicle  10  is adjusted back to a desired speed indicated by accelerator signal  62 , as illustrated at  380 . 
         [0035]    If the peak-to-peak amplitude of the terrain roughness signal  52  is greater than the minimum threshold Y, as illustrated at  360 , the speed of vehicle  10  is limited, as illustrated at  320 . The speed of vehicle  10  is limited and/or brake  70  is applied until the peak-to-peak amplitude of the roughness signal  52  is below the minimum threshold Y, indicating that the terrain being traversed by the vehicle  10  is generally smooth. Adjustments to the speed of vehicle  10 , as controlled by the terrain monitoring and motor control system  11 , can be made at a predetermined rate to effect a smooth speed adjustment. 
         [0036]    As can be appreciated, all comparisons made in various embodiments of  FIGS. 4 ,  5 , and  6  can be implemented in various other forms depending on the selected values for the peak-to-peak thresholds and the speed limit. For example, a comparison of “greater than” may be equivalently implemented as “greater than or equal to” in various embodiments. Or a comparison of “less than” may be equivalently implemented “as less than or equal to” in various embodiments. 
         [0037]    The description herein is merely exemplary in nature and, thus, variations that do not depart from the gist of that which is described are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.