Patent Publication Number: US-2005128128-A1

Title: Real-time object motion detection system and related method

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a real-time object motion detection system and a related method.  
      2. Description of the Related Art  
      Currently, real-time object motion detection systems (such as a ball velocity detection device) mainly utilize CCD cameras, ultrasonic sensors or lasers for detection. However, these types of detecting devices are very expensive, and as such are typically only available to a small cross-section of the public.  
      The propagation speed of electromagnetic waves equals the speed of light, whereas the speed of ultrasonic waves is much slower than the speed of light. Therefore, determining how to utilize the speed difference between electromagnetic waves and ultrasonic waves to obtain motion information of an object is a relatively important endeavor.  
      Therefore, it is desirable to provide a real-time object motion detection system and related method to mitigate and/or obviate the aforementioned problems.  
     SUMMARY OF THE INVENTION  
      An objective of the present invention is to provide a real-time object motion detection system and related method that reduces manufacturing costs.  
      In accordance with one aspect of the present invention, there is provided a real-time object motion detection system which includes a first object and a second object in relative movement, wherein: the first object sequentially sends a plurality of signal pairs at continuous time points, every signal pair comprising a first signal and a corresponding second signal, and a first propagation speed of the first signal is faster than a second propagation speed of the second signal; and the second object receives the plurality of first signals and second signals, wherein after receiving one first signal, the second object starts to count until receiving the corresponding second signal to obtain a time difference, and then utilizes the time difference to calculate a relative movement distance and speed.  
      In accordance with another aspect of the present invention, there is provided a moving objecting detection method for detecting relative motion information between a first object and a second object, which includes the steps of: (A) the first object sequentially sending a plurality of signal pairs at continuous time points, every signal pair comprising a first signal and a corresponding second signal, and a first propagation speed of the first signal being faster than a second propagation speed of the second signal; (B) the second object receiving the plurality of first signals and second signals, wherein after receiving one first signal, the second object starts to count until receiving the corresponding second signal to obtain a time difference; and (C) the second object utilizing the time difference to calculate the motion information.  
      Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a function block drawing of a moving object in accordance with a first embodiment of the present invention.  
       FIG. 2  is a function block drawing of a fixed object in accordance with the first embodiment of the present invention.  
       FIG. 3  is a flowchart of a method of the present invention.  
       FIG. 4  is a message flow chart in accordance with the present invention.  
       FIG. 5  is a function block drawing of a moving object in accordance with a second embodiment of the present invention.  
       FIG. 6 a  function block drawing of a fixed object in accordance with the second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Please refer to  FIG. 1 .  FIG. 1  is a function block drawing of a moving object according to a first embodiment of the present invention. The moving object  1  comprises a first signal transmitting unit  11 , a second signal transmitting unit  12  and a motion detection unit  13 . The motion detection unit  13  is used for detecting whether or not the moving object  1  is moving. If the object  1  is in motion, the first signal transmitting unit  11  and the second signal transmitting unit  12  are switched on to send respective signals; otherwise, the first signal transmitting unit  11  and the second signal transmitting unit  12  are disabled so as to place the moving object  1  into a power saving mode.  
      The first signal transmitting unit  11  is an RF transmitter for sending a plurality of first signals; the first signals are sent by way of electromagnetic waves. The second signal transmitting unit  12  is an ultrasonic transmitter for sending a plurality of second signals; the second signals are sent by way of ultrasonic waves. When the moving object  1  is moving, the first signal transmitting unit  11  and the second signal transmitting unit  12  respectively send the first signal and the second signal, and every first signal corresponds with one second signal. In other words, the first signal and the second signal are transmitted at the same time, and every first signal and every second signal has time information which is encoded and used for distinguishing the first signal and the second signal. In this embodiment, the moving object is a ball.  
      Please refer to  FIG. 2 .  FIG. 2  is a function block drawing of a fixed object according to the first embodiment of the present invention. The fixed object  2  comprises a first signal receiving unit  21 , a second signal receiving unit  22 , a timer unit  23 , a computing unit  24  and a display unit  25 . The first signal receiving unit  21  is used for receiving first signals, and the second signal receiving unit  22  is used for receiving second signals. The timer unit  23  starts to count when the first signal receiving unit  21  receives a first signal, and stops counting when the second signal receiving unit  22  receives the corresponding second signal. In this embodiment, the timer unit  23  is capable of counting time for a plurality of signal pairs (including the first and second signals). Alternatively, a plurality of timer units  23  may also be used for counting time for the plurality of signal pairs.  
      Please refer to  FIG. 3  and  FIG. 4 .  FIG. 3  is a flowchart of a method of the present invention.  FIG. 4  is a message flow chart according to the present invention. When the moving object  1  is thrown out, it sequentially sends a plurality of signal pairs at continuous time points t i  (where i=1, 2, 3 . . . ). Every signal pair includes a first signal SE i  and a second signal SS i  (step  301 ). At time t 1 , the moving object  1  simultaneously sends the first signal SE 1  and the second signal SS 1 , after which the first signal receiving unit  21  receives the first signal SE 1  of the first signal pair and the timer unit  23  is consequently activated to count. The propagation speed of the electromagnetic wave equals the speed of light, and the propagation speed of the electromagnetic wave is much faster than the propagation speed of the ultrasonic wave. Therefore, the corresponding second signal SS 1  arrives at the fixed object  2  later than the first signal SE 1 . When the second signal receiving unit  22  receives the corresponding second signal SS 1  of the first signal pair, the timer unit  23  stops counting to obtain the time difference Δt 1  of the signal pair. By this method, at continuous time points t 2 , t 3 , t 4 , . . . , the first signal receiving unit  21  and the second signal receiving unit  22  receive a plurality of first signals SE i  and second signals SS i  (i=2, 3, 4 . . . ) as signal pairs, and the timer unit  23  counts time for the plurality of signal pairs until the moving object  1  stops (step  302 ), obtaining a plurality of time differences Δt i  (i=2, 3, 4 . . . ).  
      The computing unit  24  reads the time differences Δt i , and obtains motion information including a relative distance between the moving object  1  and the fixed object  2  and the speed of the moving object  1  by utilizing the following equations: 
 
 L   i   =V′×t   i , 
 
and
 
 V =( L   i   −L   i−1 )/Δ t   i , 
 
 wherein L i  is a distance between the first object  1  and the second object  2  at time t i , V′ is a transmission speed of the second signal (an ultrasonic wave), Δt i  is a time difference determined by the timer unit  23  at time t i , and V is a speed of the first object  1  (step  303 ). 
 
      After the above-mentioned calculations, the distances between the moving object  1  and the fixed object  2 , and the speed of the moving object  1  at continuous time points (t i , i=1, 2, 3 . . . ), are obtained, and this motion information can be displayed on the display unit  25 , or be summarized and displayed at a predetermined time after the moving object  1  comes to a stop.  
      According to the above description, the present invention utilizes the moving object to send a plurality of first signals by way of electromagnetic waves, and second signals by way of ultrasonic waves, to the fixed object. When the fixed object first receives the first signals sent along the electromagnetic waves, the timer unit starts to count, and when the fixed object receives second signals sent along the ultrasonic waves the timer unit stops counting, thereby obtaining a time difference. Next, the computing unit calculates the motion information of the moving object according to the time differences and a speed of the ultrasonic wave. Therefore, the present invention provides a simple detection system that reduces manufacturing costs.  
      Please refer to  FIG. 5  and  FIG. 6 .  FIG. 5  is a function block drawing of a moving object according to a second embodiment of the present invention.  FIG. 6 a  function block drawing of a fixed object according to the second embodiment of the present invention. This embodiment is similar to the previous embodiment except that the fixed object  2  sends a plurality of first signals by way of electromagnetic waves, and second signals by way of ultrasonic waves, to the moving object  1 , and the moving object  1  obtains the motion information according to the first signal and the second signal. As shown in the drawings, the fixed object  2  comprises a first signal transmitting unit  11 , a second signal transmitting unit  12 , a motion information receiving unit  15 , a control unit  14  and a display unit  25 . The first signal transmitting unit  11  is an RF transmitter, for sending a plurality of first signals; the first signals are sent via electromagnetic waves. The second signal transmitting unit  12  is an ultrasonic transmitter, for sending a plurality of second signals; the second signals are sent via ultrasonic waves. The first signal transmitting unit  11  and the second signal transmitting unit  12  respectively send the first signals and the second signals simultaneously. The motion information receiving unit  15  is used for receiving motion information, the control unit  14  processes the motion information, and the display unit  25  shows the results. The moving object  1  comprises a first signal receiving unit  21 , a second signal receiving unit  22 , a timer unit  23 , a computing unit  24  and a motion information transmission unit  26 . The first signal receiving unit  21  is used for receiving the first signal, and the second signal receiving unit  22  is used for receiving the second signal. The timer unit  23  starts to count when the first signal receiving unit  21  receives the first signal, and stops counting when the second signal receiving unit  22  receives the corresponding second signal. The computing unit  24  reads the time differences Δt i , and obtains a relative distance between the moving object  1  and the fixed object  2 , and the speed of the moving object  1  by way of the same equations described above. The motion information transmission unit  26  sends the motion information to the motion information receiving unit  15  for display by the display unit  25  of the motion information of the fixed object  2 .  
      Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.