Abstract:
Apparatus of a power driven wheelchair for displaying operational parameters thereof comprises: a programmed controller operative to monitor a plurality of operational parameters of the wheelchair; a joystick unit coupled to the programmed controller; and a display screen integral to the joystick unit. The programmed controller is operative to interact with the joystick unit to display a user selected operational parameter of the plurality on the display screen of the joystick unit. In addition, a method of displaying operational parameters of a power driven wheelchair on a display screen integral to a joystick unit of the wheelchair comprises the steps of: monitoring a plurality of operational parameters of the wheelchair by a programmed controller; coupling the joystick unit to the programmed controller; utilizing the joystick unit to select an operational parameter of the plurality; and operating the programmed controller to interact with the joystick unit to display the selected operational parameter of the plurality on the display screen of the joystick unit.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to the field of power driven wheelchairs, in general, and more particularly to an integral joystick display therefor and a method of operating the same. 
     Power driven wheelchairs which may be of the type manufactured by Invacare Corporation of Elyria, Ohio, for example, generally include right and left side drive wheels driven by a motor controller via respectively corresponding right and left side drive motors, all of which being disposed on the wheelchair. An exemplary illustration of such a motor drive arrangement is shown in the schematic of  FIG. 1 . Referring to  FIG. 1 , a motor drive controller  10  which may be an Invacare MK IV™ controller, for example, controls drive motors  12  and  14  which are mechanically linked respectively to the right side and left side drive wheels of the wheelchair. The controller  10  includes a microcontroller  15  which may be programmed with a plurality of drive programs, each suited for a particular operating environment of the wheelchair. 
     A user interface  16  Which may include a joystick  18  and selection switches (not shown) operable by a user is also disposed on the Wheelchair in a convenient location to the user. The user interface  16  is generally interfaced to the microcontroller  15  over a two wire serial coupling  20  to permit the user to select a drive program appropriate for operating the wheelchair in its environment and to adjust the direction and speed of the wheelchair within the selected drive program. In the present example, a main program of the microcontroller  15  which may contain the plurality of drive programs is stored in a non-volatile memory  19 , like a read only memory (ROM), for example, -which may be integrated into the microcontroller  15  or may be a separate component thereof. 
     The motor controller  10  is generally powered by a battery source  22 , which may be 24 volts, for example, also disposed on the wheelchair. The drive motors  12  and  14  may be of the permanent magnet type and may be either a gearless, brushless AC motor or a brush type DC motor. The microcontroller  15  is interfaced and responsive to the user interface  16  to control drive signals  24  and  26  to motors  12  and  14 , respectively, via a power switching arrangement configured in accordance with the motor type being driven. The power switching arrangement may be powered by the 24V battery  22 . Thus, as the user adjusts the speed and direction of the wheelchair via the joystick of interface  16 , appropriate drive signals  24  and  26  are controlled by motor controller  10  via microcontroller  15  to drive the motors  12  and  14  accordingly. 
     Motor controller  10  generally controls motor speed to the user setting utilizing a closed loop controller programmed in the microcontroller  15 . Actual speed of each motor  12  and  14  may be derived from signals  28  and  30  respectively sensed therefrom. For example, for AC motors, a Hall Effect sensor may be disposed at the motor for sensing and generating a signal representative of angular position. The signals  28  and  30  are coupled to the microcontroller  15  which may be programmed to derive motor speed from a change in angular position for use as the actual speed feedback signal for the closed loop speed control of the motor. For DC motors, the voltage Va across the armature and armature current Ia may be sensed from each motor  12  and  14  and provided to the microcontroller  15  via lines  28  and  30 , respectively. Microcontroller  15  may under programmed control derive the actual speed of each motor  12  and  14  from the respective voltage Va and current Ia measurements thereof for use as the speed feedback signal for the respective closed loop speed control of each motor  12  and  14 . 
     In addition, interaction with the motor controller  10  is performed through a remote programmer  34  which may be electrically coupled to a port of the microcontroller  15  via signal lines  36 , for example. Each remote programmer  34  may include a screen  38  for displaying interactive text and graphics and a plurality of pushbuttons  40  for communicating with the microcontroller  15  which is programmed to interact with the programmer  34 . A dealer is generally provided with one or more remote programmers for rendering the wheelchair unique to the user&#39;s safe operating capabilities. 
     Present joystick interface units  16 , like the joystick unit interfaced to Invacre&#39;s MK IV controller, for example, do not have an interactive display, but rather are only capable of displaying an indication of battery discharge which may be a line bar representative of the charge remaining on the battery  22 , for example. It is desirable from both a user and dealer standpoint to have a display which may selectively display screen images of current operational parameters of the wheelchair. Display of such operational parameters of the wheelchair will enhance the ability to know when to replace and service certain components of the wheelchair. 
     The present invention provides such a display integral to a joystick unit which is already interfaceable to and operable with the microcontroller  15  for hands-on control to render a more convenient and less costly add-on display. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, apparatus of a power driven wheelchair for displaying operational parameters thereof comprises: a programmed controller operative to monitor a plurality of operational parameters of the wheelchair; a joystick unit coupled to the programmed controller; and a display screen integral to the joystick unit, wherein the programmed controller being operative to interact with the joystick unit to display a user selected operational parameter of the plurality on the display screen of the joystick unit. 
     In accordance with another aspect of the present invention, a method of displaying operational parameters of a power driven wheelchair on a display screen integral to a joystick unit of the wheelchair comprises the steps of: monitoring a plurality of operational parameters of the wheelchair by a programmed controller; coupling the joystick unit to the programmed controller; utilizing the joystick unit to select an operational parameter of the plurality; and operating the programmed controller to interact with the joystick unit to display the selected operational parameter of the plurality on the display screen of the joystick unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram schematic illustration of an exemplary motor drive arrangement for a power driven wheelchair. 
         FIG. 2  is a block diagram illustration of an interactively operated integral joystick display suitable for embodying the principles of the present invention. 
         FIG. 2A  is an exemplary screen image suitable for display on the integral joystick display. 
         FIG. 3  is a block diagram schematic of an exemplary joystick unit with an integral display suitable for use in the embodiment of  FIG. 2 . 
         FIG. 4  is a software flowchart of an exemplary program suitable for use in the embodiment of  FIG. 2 . 
         FIGS. 5A–5F  are exemplary screen images suitable for display on the integral joystick display in a predetermined sequence. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 2  is a block diagram illustration of an interactively operated integral joystick display suitable for embodying the principles of the present invention. Referring to  FIG. 2 , a joystick unit  50  having an integral image screen display  52 , which may be a liquid crystal display (LCD), for example, interfaces with the microcontroller  15  utilizing signals serially transmitted over the two wire serial cable connection  20  to interactively control the operation of the wheelchair. More specifically, the joystick unit  50  includes a rotary knob  54  located at the front of the unit near the LCD  52  for setting the maximum speed of the wheelchair. In the present embodiment, the microcontroller  15  detects a clockwise rotation of the knob  54  via signals over cable  20  and increases the maximum speed of the wheelchair in response thereto. The microcontroller  15  also detects movement of a joystick  56 , located at the middle of the unit  50 , via signals over cable  20  and provides smooth control of the speed and direction of the wheelchair. 
     The microcontroller  15  further responds to movement of a drive select momentary switch  58  via signals over the cable  20  to control the wheelchair in a drive program selected by the user. The unit  50  additionally includes a one-eighth inch diameter phono plug or jack  60  located at the rear of the unit. In the present embodiment, a momentary switch  62 , which may be an ability switch, for example, may be plugged into the jack  60  such that when the contacts of switch  62  are closed a representative signal is conducted over the cable  20  to the microcontroller  15 . Usually, an ability switch includes a flexible stem and an integral switch which is normally open. Moreover, a bending of the flexible stem momentarily closes the integral switch thereof. 
     A block diagram schematic of an exemplary joystick unit  50  suitable for use in the embodiment of  FIG. 2  is shown in  FIG. 3 . Referring to  FIG. 3 , the joystick unit  50  comprises a microcontroller  300  which may be of the type manufactured by Toshiba under the part no. TMPN3150B, for example. In the present embodiment, the Toshiba microcontroller  300  is designed for serial communication using a proprietary protocol developed by Echelon Corporation, for example. It has serial driver circuits  302  for interacting with the serial cable  20  and internal firmware stored in a read only memory (ROM)  304  executable to send and receive serial data over cable  20 . Received serial data from cable  20  may be further processed by application firmware of the microcontroller  300  which may also be stored in ROM  304 . The ROM  304  may be external to the microcontroller  300  or integrated therewith. 
     An external analog to digital converter (A/D)  306  may be used to read and digitize voltage signals from the joystick  56  and rotary knob  54  of the unit  50 . The digitized signals are received by the microcontroller  300  which transmits them serially over cable  20 . Also, input/output (I/O) circuits  308  of the microcontroller  300  are coupled to the switches  58  and  62  for reading the states thereof which may be also transmitted serially over cable  20  by the microcontroller  300 . Additional I/O circuits  310  of the microcontroller  300  are coupled to the LCD  52  which is controlled by address (A), data (D), and control (C) lines of the microcontroller  300 . At times, data may be temporarily stored in a scratch pad or random access memory (RAM)  312  of the microcontroller  300 . Serial protocols, such as CAN and RS 232 , for example, may be used by the microcontroller  300  for serial communication. 
     In the present embodiment, the LCD  52  may be of the type manufactured by Hantronix under the part no. HDM12216L, for example. As will become more evident from the following description, all of the data that appears on the display  52  is determined by the microcontroller  15  and transmitted to the joystick unit  50  over cable  20 . In the unit  50 , the microcontroller  300  receives and translates the serial data from cable  20  and delivers the data directly to the LCD  52  for display in an appropriate screen image format. In the alternative, the microcontroller  300  may receive data from the microcontroller  15  via serial lines  20 , process and/or store it in the RAM  312 , then transfer it to the LCD  52  for display. 
     Returning to  FIG. 2 , the microcontroller  15  receives sensor signals  28  and  30  through an analog-to digital converter unit (A/D)  64  which may be part of the microcontroller  15 . The A/D unit  64  may sample and digitize the sensor signals  28  and  30  and store the sampled digitized data in a memory  66  which may also be part of the microcontroller  15 . In the present embodiment, the microcontroller  15  is operative under program control to derive from one or both of the sampled, digitized sensor signals: (1) a current speed of the wheelchair in parametric units of miles per hour (mph) or kilometers per hour (kmh) or both; (2) a trip distance traveled since the wheelchair was last powered on in parametric units of miles (MI) or kilometers (KM) or both; and (3) a total distance traveled by the wheelchair. All of the resultant derivations may be stored in designated registers of memory  66 . 
     Still further, a battery circuit  68 , which may be part of the motor controller  10 , for example, may be connected to the battery  22  for monitoring certain operational parameters thereof, like voltage and current, for example. In the present embodiment, circuit  22  may generate signals representative of the current battery voltage and battery current being used, and provide such signals to the AID unit  64  wherein such signals may be sampled and digitized. The sampled, digitized voltage and current data of the battery  22  may be stored in memory  66 . The microcontroller  15  is also programmed to derive from the battery voltage and current data trip battery consumption or battery capacity consumed since the wheelchair was last powered on in parametric units of amp-hours (AH). The derived and measured values may be stored in designated registers of memory  66 . 
     Further yet, the battery circuit  68  may be controlled by the microcontroller  15  to perform a load test on the battery  22  from time to time and measure the current battery condition (BATT) based on each load test. In the present embodiment, the battery load test is performed automatically and without user intervention. For example, the microcontroller  15  may execute a routine which monitors the battery voltage, time and current load on the battery. During the routine, when the right sequence of events occurs during normal usage of the wheelchair, the load test data is captured and the display is updated as will become more evident from the description below. Factors in the sequence are: battery fully charged, a five minute rest period before the load test, a load on the batteries of 30–40 amperes, and the load is stable long enough for the data to be considered valid. 
     A voltage difference or drop between the rest battery voltage and the loaded battery voltage is read by the microcontroller  15  via A/D  64  and stored in a non-volatile portion of the memory  66 , which may be EEPROM, for example. In the present battery load test routine, if the voltage drop under load is in the approximate range of 0–2.0V, the battery or batteries are considered good. If the voltage drop under load is in the range of 2–2.5V, the battery is considered poor, and if the voltage drop is more that 2.5V, the battery is considered bad. The resulting measured battery status of “GOOD”, “POOR” or “BAD” is stored in memory  66  for display when selected as will become better understood from the following description. 
     In accordance with the present invention, certain operational parameters of the wheelchair, like current speed (speedometer), trip miles or kilometers (trip odometer), total distance in miles or kilometers (odometer), battery capacity consumed since the chair was last powered on (trip amp-hour meter), current battery voltage (battery volts), battery current being used (battery amps), and load test results (good, poor or bad), for example, may be selectively displayed on the integral joystick display  52  via communication over the serial communication cable  20 . 
     An exemplary screen image displayed by the microcontroller  15  on the LCD  52  via microcontroller  300  of unit  50  is shown in  FIG. 2A . Referring to  FIG. 2A , in the present embodiment, the screen image is a two line (top and bottom) by twelve character length back lighted display which is separated into left side and right side image sections,  80  and  82 , respectively. The drive program selected by the user is displayed on the top line of the left side image section  80 . Displayed on the bottom line of the left side image section  80  is a battery discharge indicator comprising a line of five character blocks going from E (empty) to F (full). At full charge, all of the blocks are darkened or filled in. As the battery  22  becomes discharged, the furthest right blocks will progressively become unfilled or disappear a half block at a time until no blocks or segments appear between E and F. At this battery level, the word “RECHARGE” will appear on the second line of the left side image section  80 . 
     To accomplish the foregoing described left side image screen display, the microcontroller  15  is pre-programmed to function in accordance with the following steps. The microcontroller  15  determines the drive program selected by the switch  58  of the joystick unit  50  and stored in memory  66 , and sends serial data over cable  20  to render the selected drive program displayed on the top line of the left side screen image section  80  as shown in  FIG. 2A . In addition, the microcontroller  15  calculates battery capacity from the battery voltage using a predetermined table of battery voltage vs. battery capacity relationships, which may be stored in memory  66 , for example, and uses a time averaging filter algorithm to obtain a present battery capacity. Data of the present battery capacity is transmitted serially over the cable  20  to the joystick unit  50  to update the line block battery indicator displayed on the bottom line of the left side screen image section  80  as shown in  FIG. 2A . 
     On the right side section  82  of the exemplary screen image of  FIG. 2A , which is referred to as an information center, is displayed a selected one of the aforementioned operational parameters of the wheelchair on the top and bottom lines thereof. In the example image of  FIG. 2A , a preprogrammed factory default odometer reading is displayed in the right side section  82  with the parametric unit of miles (MI) displayed on the top line and the total miles traveled by the wheelchair numerically displayed on the bottom line. It is understood that the total distance traveled by the wheelchair may also be displayed in kilometers (KM) just as well. As noted above, data representative of all of the operational parameters which are to be displayed are stored in memory  66  in parametric unit format. 
     The selection between English and metric units may be made with the programmer  34  described in connection with the embodiment of  FIG. 1  and saved in a non-volatile portion of memory  66 . In the present embodiment, the factory default selection is English, but in countries other than the U.S., like Canada, for example, metric units are preferred. The dealer can perform a change in metric units via the programmer  34  before delivering the wheelchair to the user. 
     A benefit of integrating the display  52  in the joystick unit  50  is to allow the user to interact via the microcontroller  15  with the display  52  through movement of the joystick  56  and/or other switches on the unit  50 , for example. One of the user interactions is the selection of the operational parameter to be displayed as will become more evident from the following description. Thus, the microcontroller  15  is programmed to detect a command to enter a display select mode which is transmitted over cable  20  from the microcontroller  300  of joystick unit  50  to the microcontroller  15 . While in such mode, the microcontroller  15  is further programmed to detect commands transmitted over cable  20  from the microcontroller  300  of unit  50  to determine the operational parameter selected by the user for display in the information center  82 . And, in response, the microcontroller  15  is operative to send the associated operational parameter data serially over cable  20  to the microcontroller  300  of joystick unit  50  to render the units and value of the selected parameter displayed on the top and bottom lines of the information center  82  of the screen image as described above. 
     An exemplary program suitable for use in the microcontroller  15  for interacting with the joystick unit  50  and display  52  is shown in the flowchart of  FIG. 4  and typical screen images for the display  52  are shown in  FIGS. 5A–5F . Referring to  FIG. 4 , in decisional block  100 , the program monitors the cable  20 , for example, to determine if a command is present to enter the display select mode. The microcontroller  300  of unit  50  may generate this command over cable  20  in response to an activation of the switch  62 , for example. While the activation switch  62  is utilized to enter the display select mode in the present embodiment, it is understood that other switches may be utilized just as well without deviating from the principles of the present invention. Moreover, in the present embodiment, the microcontroller  15  may be default programmed to provide data to the unit  50  for displaying the wheelchair odometer reading such as shown in the screen image of  FIG. 3 . 
     When the display select mode is entered as determined by block  100 , decision block  102  determines if the joystick  56  is moved to a predetermined position, like to the left, for example. In the present embodiment, the microcontroller  300  of unit  50  detects a joystick movement to the left and sends a command to the microcontroller  15  over cable  20 , which command being identified by block  102 . If no command is present after a predetermined time period as determined by decision block  104 , then execution is returned to block  100  awaiting for the next command for entry into the display select mode. Otherwise, program execution continues at block  106  wherein data of the parametric units and value of an operational parameter next in a predetermined sequence is provided to the microcontroller  300  of unit  50  over cable  20  for display in the screen image of the display  52 . For example, if speed of the wheelchair is the next parameter in the predetermined sequence, then the screen image exhibited in  FIG. 5A  will appear on display  52 . Thereafter, the program is delayed for a short time period in block  108  and returned to block  102 . 
     If in block  102 , it is identified that the joystick  56  remains in the left position, then data of the operational parameter next in sequence is again provided to the microcontroller  300  of unit  50  for display in the information center of display  52 . If the next parameter is trip odometer, then the screen image will appear as shown in  FIG. 5B . So long as the joystick  56  is maintained in a left position, data will be provided by the microcontroller  15  to the microcontroller  300  of unit  50  to render a scrolling of the screen image of display  52  through the various operational parameters like trip-amp hour meter, battery volts, battery current, and load test results, for example, as shown in the screen images of  FIGS. 5C through 5F , respectively. During scrolling, each operational parameter screen image remains displayed for the time period set in the delay block  108  which may be on the order of two seconds, for example. Whenever, the user observes the desired parameter on the display  52 , he or she may move the joystick  56  to a position away from the left position which will be identified in block  102 . Thereafter, program execution will return to block  100  via blocks  102  and  104  and the current screen image will remain until re-entry into the display select mode by the user. During display of the selected parameter, it will be updated in value by the microcontroller  15  in a timely fashion. 
     While the present invention has been described herein above in connection with one or more embodiments, it is understood that such description is presented by way of example with no intent of limiting the invention in any way. Rather, the invention should be construed in breadth and broad scope in accordance with the recitation of the claims appended hereto.