Abstract:
An electric car includes a remote control calling system includes a transmitter and a car, and both of which have an electronic compass for detecting the terrestrial magnetism to obtain an azimuth and calculating the azimuth difference of the two by simple computations. The system automatically controls the direction of the car driving towards a user, and achieves the purposes of simplifying the car structure and facilitating its use.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an electric car having a remote control calling system, and more particularly to a system having a transmitter and a car, and both having an electronic compass for detecting the terrestrial magnetism to obtain an azimuth and calculating the azimuth difference of the two by a simple computation.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the structure of a prior art golf car, the golf car is designed to have a function of automatically following a golfer. The golfer just needs to send a signal to the golf car, and the processor of the golf car processes the signal to drive a driving motor, such that the golf car will move according to the position of the golfer. At present, a prior art structure comprises a tracker and. a guider. The guider is carried by the golfer, and the tracker is installed onto the golf car, wherein the tracker includes a first processor, at least two encoders for producing encoded signals, and each encoder includes a control input and is connected to the first processor. The control of the direction of the prior art system works with the tracker having several infrared transmitters which are the devices capable of detecting directions and encoding, and each transmitter can transmit signals at the same time, and the guider sends a feedback RF signal to the tracker and indicates a signal of a particular transmitter is detected, and then the processor will determine the direction. However, the golf car of the prior art system will follow the golfer, and if the golfer walks through a bunk or a pit, the golf car will detour around the bunk. While the golfer has detoured around the bunk and the golf car is still in the middle of the bunk, the golf car will turn accordingly if the golfer makes a turn, and thus the golf car will drop into the bunk. Furthermore, it is not practical for the golf car to follow the golfer all the time during the course of striking the golf ball. As long as the golfer moves, the golf car will move accordingly, and it will affect the golfer or other golfers to strike the golf balls. In addition, the prior art system requires the golf car to transmit signals and the guider to receive signals, and these components consume power all the time, and thus such prior art is not cost efficient.  
         [0003]     There is another prior art system that comprises a fixed position receiver, a stepping motor, an infrared detector, and a processor, and the infrared detector is driven to rotate within a wide angle by the stepping motor. Once the infrared detector receives a signal from the transmitter, the infrared detector will determine the direction and drive the servo turner to make turns for the golf car so as to fix the position after the fixed position receiver has received the signal. The processor will compute and memorize the distance between the golf car and the golfer, and then execute the instructions for moving the golf car according to the position and distance and repeating the positioning, detecting, memorizing, and executing processes. However, this prior art system still has the same shortcoming of following the golfer all the time as described above. Obviously, it is not necessary for the golf car to follow the golfer during the course of striking the golf ball. Once the golfer moves, the golf car will move accordingly, and such arrangement will affect the golfer or other golfers striking the golf galls. The prior art system requires fine and complicated components, and thus increasing the cost, and exhausting the components easily.  
       SUMMARY OF THE INVENTION  
       [0004]     Therefore, it is a primary objective of the present invention to provide a car having a transmitter and a position receiver, and both transmitter and car have an electronic compass module for detecting the terrestrial magnetism to confirm their azimuths. The transmitter sends its azimuth to the car, and the processor of the car compares the two azimuths to compute the azimuth difference. The driving controller drives the driving motor to rotate, so that the car is turned to the zero azimuth difference, and then the car is driven towards the transmitter. The invention can achieve the effects of simplifying the structure, improving the precision, and lowering the cost.  
         [0005]     The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a schematic view of a basic structure of a car according to the present invention;  
         [0007]      FIG. 2  is a schematic view of an architecture of a system of the present invention;  
         [0008]      FIG. 3  is a schematic view of an azimuth relation according to a first preferred embodiment of the present invention; and  
         [0009]      FIG. 4  is a schematic view of an azimuth relation according to a second preferred embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]     The present invention provides a remote control electric car used for wheelchairs, transportation cars, dining cars or golf cars. Refer to  FIGS. 1 and 2  for a golf car having a containing rack for storing golf balls and equipments according to a preferred embodiment of the invention. The present invention involves a caller and a car  20 , and the caller caries a position transmitter  10  for producing and transmitting the azimuth data of the caller, wherein the position transmitter  10  comprises an electronic compass module  11 , having a sensor for detecting the terrestrial magnetism and producing a first azimuth data of the caller. A first microprocessor  12  converts the first azimuth data into a first azimuth signal. An encoder  13  encodes the first azimuth signal and a radio frequency transmitter  14  which transmits the first azimuth signal.  
         [0011]     The car  20  comprises a car body  21  having at least one front wheel  22  installed at the front end of the car body  21  and two driving wheels  23  are installed on both sides of the car body  21 . An electronic compass  24  detects the terrestrial magnetism and produces a second azimuth data for the driving direction of the car. A position receiver  25  receives the first azimuth signal comes from the radio frequency transmitter  14 . A decoder  26  decodes the received first azimuth signal and a second microprocessor  27  which converts the second azimuth data into a second azimuth signal, and a driving controller  28 . At least one electric motor  29  which drives the driving wheel  23  to rotate and at least one battery  30  which supplies the required power.  
         [0012]     If the caller aims the position transmitter  10  at the car  20 , the electronic compass module  11  of the position transmitter  10  will obtain a first azimuth data of the caller, and the first microprocessor  12  converts the first azimuth data into a first azimuth signal. The first azimuth signal is encoded by the encoder  13  and then transmitted by the radio frequency transmitter  14  to the car  20 . The position receiver  25  of the car  20  receives the signal and the decoder  26  decodes the signal. The decoded signal is inputted into the second microprocessor  27  of the car  20  and the second azimuth data produced by the electronic compass  24  of the car  20  is also inputted to the second microprocessor  27  and converted into a second azimuth signal. The second microprocessor  27  compares the first azimuth signal and the second azimuth signal and computes the azimuth difference between the caller and the driving direction of the car  20 . If the azimuth difference is zero, the driving direction of the car  20  will aim at the caller, and the second microprocessor  27  will send the forward signal to the driving controller  28 . The driving controller  28  will control the motor  29  to rotate and drive the car  20  forward. If the azimuth difference is not zero, the second microprocessor  27  will send out a turning signal to the driving controller  28 , and the driving controller  28  will control the motor  29  to rotate and turn the car  20  from its original position until the azimuth difference becomes zero, and then will control the car  20  to go forward.  
         [0013]     In a preferred embodiment of the present invention, the car  20  has two motors  29  and each motor  29  is responsible for driving a corresponding driving wheel  23 . The driving controller  28  can output two different control signals to the two motors  29  so that the two driving wheels  23  can produce a relative rotary speed difference to turn the direction of the car  20  from its original position.  
         [0014]     In a preferred embodiment of the present invention, the position receiver  25  of the car  20  includes a receiving antenna  250  for improving the capability of receiving signals.  
         [0015]     Referring to  FIGS. 1 and 2  for the operating procedure of the present invention, the caller uses a position transmitter  10  to aim at a desired car  20 , such that the transmitter  10  produces a first azimuth data and the processor  12  converts a first azimuth signal and encodes the signal. The transmitter  10  then transmits the first azimuth signal to the car  20 . The car produces a second azimuth data and the processor  27  converts the data into a second azimuth signal. If the car  20  receives the first azimuth signal come from the transmitter  10  of the caller, then the first azimuth signal will be decoded. The second azimuth signal will be compared to compute a azimuth difference and the azimuth difference will be used as a signal for controlling the movements of the car  20 . The principle of its control is described as follows:  
         [0016]     (a) If the azimuth difference is zero, it means that the driving direction of the car  20  aims at the caller, and the car  20  will move forward; and  
         [0017]     (b) If the azimuth difference is not zero; then car  20  will turn its direction from the original position until the azimuth difference becomes zero, and then the car  20  will move forward.  
         [0018]     Referring to FIGS.  1  to  4  for the rules of computing the azimuth difference, two examples are used for the description.  
       EXAMPLE 1  
       [0019]     If the transmitter  10  aims at the car  20 , the first azimuth A is equal to 60 degrees, and if the car  20  aims at the second azimuth B which is equal to 135 degrees, then the first azimuth signal will be transmitted to the car  20 . The processor  27  of the car  20  will find the inverted angle C of the first azimuth to be 240 degrees, and the second azimuth B is subtracted from the inverted angle C (i.e. 240−135=105 degrees). The azimuth difference C is 105 degrees. The processor  27  will send a turning instruction to the driving controller  28  according to the azimuth difference signal and the driving controller  28  will control the motor  29  to rotate, so that the car  20  will turn  105  degrees counterclockwise from the original position. Therefore, the car  20  will aim at the caller and then an instruction will be sent to control the car  20  to move forward in the direction of the caller.  
       EXAMPLE 2  
       [0020]     If the transmitter  10  aims at the car  20 , the first azimuth A is equal to 60 degrees and the car  20  will aim at the second azimuth B which is equal to 315 degrees. The first azimuth signal is transmitted to the car  20  and the processor  27  of the car  20  computes the inverted angle C of the first azimuth which is equal to 240 degrees. The second azimuth B is subtracted from the inverted angle (i. e. 315−240=−75 degrees) to obtain the azimuth difference C′ which is equal to −75 degrees. The processor  27  will send a turning instruction to the driving controller  28  according to the azimuth difference signal, so that the driving controller  28  is controlled to rotate the motor  29  and the car  20  is turned 75 degrees clockwise from the original position. Therefore the car  20  will aim at the caller, and an instruction is sent to control the car  20  to move forward in the direction of the caller.  
         [0021]     In the foregoing two examples, the first azimuth data and second azimuth data uses the pointing line of the electronic compass module as the base, and the azimuth difference is obtained by subtracting the second azimuth from the inverted angle of the first azimuth. If the azimuth difference is positive, then the car will be turned counterclockwise from the original position until the azimuth difference becomes zero. If the azimuth difference is negative, then the car will be turned clockwise from the original position until the azimuth difference becomes zero.  
         [0022]     Further, the transmitter  10  of the invention includes a turning control button  15  connected to the first microprocessor  12  for controlling the turning direction of the car  20 . If the user finds that there is an obstacle in front of the car  20 , the user can press the turning control button  15  to change the driving direction of the car  20  to avoid the obstacle. The transmitter  10  can further includes a speed control button  16  connected to the first microprocessor  12  for controlling the driving speed of the car  20 . The transmitter  10  can further includes a parking control button  17  connected to the first microprocessor  12  for controlling the parking of the car  20 .  
         [0023]     While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.