Abstract:
The present invention allows the simple measurement of position and orientation with low cost setup and simple calibration using a small set of transmitting nodes and a simple handheld wand. This can be used in place of measuring tools such as non contact reflection based ultrasonic measurement tools or traditional tools such as tape measures and rulers where multiple high precision measurements are needed with minimal set up time. The present invention also provides true three dimensional output and orientation calculation.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claim the benefit of U.S. Provisional Patent Application 60/975,797 filed on Sep. 27, 2007, all of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to measuring devices such as those used by contractors to determine square footage of house for carpet delivery, measurement of surfaces for counter cutting such as granite slabs, or for use in industry so that robots and industrial machinery can accurately track their end effector positions. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0003]      FIG. 1  Shows an overall depiction of the present invention. 
           [0004]      FIG. 2 . Depicts an alternate simple setup for the invention reference platform. 
           [0005]      FIG. 3 . Shows a handheld wand which contains an internal connection between its end effectors used in transmitting delay information from one end to the other. 
           [0006]      FIG. 4 . Shows a handheld wand with a delay measurement circuit in the middle. 
           [0007]      FIG. 5 . Shows a block diagram of a delay measurement circuit. 
           [0008]      FIG. 6 . Shows a single portion of a wire line delay element. 
           [0009]      FIG. 7 . Depicts several delay elements, here modeled as box elements with a wave traveling from element to element. 
           [0010]      FIG. 8 . Depicts several delay elements each with an output tap. 
           [0011]      FIG. 9 . Depicts two waves traveling towards each other along the taps. 
           [0012]      FIG. 10 . Represents the element where upon the two traveling waves have intersected. 
           [0013]      FIG. 11 . Represents a symbolic representation of an intersection test circuit. 
           [0014]      FIG. 12 . Represents an overview of the block diagram of the computational system. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0015]    The present invention works by setting 3 or more (preferable 4 or more) transmitting nodes and two receiving nodes. The transmitting nodes should be fixed in orientation, such as part of attached to a walls in a room, or as part of a single apparatus such as on a tripod like assembly as depicted 
         [0016]      FIG. 1 . The nodes are depicted by the circles with the letter M, while the receiving nodes are depicted by the nodes W on a portable wand. Electronics in the wand determine the time difference of a signal emanating from each of the individual nodes to the two endpoints on the wand. By measuring the four delta times of pulse from each given node to the two endpoints a simultaneous system of equations allows the deduction of the two endpoints of the wand in free space relative to the nodes on the tripod. The system allows one set of fixed emitters to function with multiple receivers as is possible in a factory environment. 
         [0017]      FIG. 1  A portable tripod  100  contains several transmitters  110  which each emit a signal from the nodes marked M ( 100 ), to a wand  105  which receives said signal is received at the nodes marked W  120 . Based on the received signal&#39;s relative delay from each node M to each node W, the position and orientation of the wand can be calculated. 
         [0018]    Error! Reference source not found. Depicts a lower cost portable Tripod setup  200  where merely positioning the tripod in a room requires no extending arms. The only requirement for the emitter nodes is that they be placed as far apart as possible and that set of 4 emitters is not coplanar. 
         [0019]      FIG. 3  shows depicts the wand  105  with an internal path for taking the received signal from the receiving nodes  120 . 
         [0020]      FIG. 4  shows the wand with a circuit  125  which measures the relative delay of the received signal from each of receiver nodes. 
         [0021]      FIG. 5  shows a block diagram of the circuit  125   FIG. 4 . Here the receiving gyrator ( 500 ) which could be receiving acoustic or RF energy is conducted via node  505  to amplifier  510  and sent to delay line  515 . A similar set of circuits takes the energy received at the other end of the wand  535  to combiner  540  and amplifier  530  where that energy is then sent to delay line  525 . The delay is calculated by the difference calculator  520 . The relative pulse-waves  545  and  550  depict the information transmitted from the receiving end of the wands towards the pulse delay calculator  520 . 
         [0022]    If RF energy is used (e.g. RF pulses) instead of ultrasonic pulses it may be necessary to find alternate means by which to measure the time differences as the resolution needed may require prohibitively expensive circuitry for mass market applications. Using a delay line in the body of the wand to slow down RF based signals can accomplish this. This is necessary since RF energy travels near the speed of light. Assuming the to wand endpoints to be ⅓ of a meter then the time propagation from 1 end to the other is on the order ins which is a very small time period to accurately measure with low cost electronics. This can be enhanced by delaying the time it takes the signal to propagate and then measuring where on the wand the signal from the two ends meet. Error! Reference source not found.  FIG. 6  shows a small loop of wire for this case. Here rather then moving a single mm forward, a loop of X mm in diameter will induce a delay of X*Pi times longer a propagation. Combined with a pitch of Y loops per mm, we can make a delayline which stretches the time out for a pulse to propagate from one end to the other by X*Y*Pi times. For example a 10 mm diameter coiled transmission line with a pitch of 4 turns per mm, will induce a delay of 10*4*Pi which is about 120 times longer so our 1 ns delta becomes 120 ns. This allows us to use low cost electronics by tapping the transmission line and comparing where the pulse arriving at the two ends of the wand meet as shown in  FIG. 7 ,  FIG. 8 , and  FIG. 9 . By using the delay lines and using simple circuitry to see where to arriving pulses meet we can determine what the actual delta time delay is from a pulse sent from a given transmitting node to each end node is.  FIG. 10  depicts a single delay line where the two signals from each end have met. A circuit for detecting the two pulses meeting up is shown in block diagram form in  FIG. 11 . 
         [0023]    Each delay from each transmitting nodded is measured sequentially. This is accomplished by having each transmitting node emit its signal in turn followed by the next and then the next. The combined delta delays of the received signal for each transmitting node combine to produce a set of equations which can be solved to compute the position of each of the two wand endpoints relative to the set of transmitting nodes and the relative orientation of the two wand endpoints to each of the transmitting nodes.  FIG. 11  depicts a block diagram of a CPU system which provides the measurement output. The transmitting nodes can use ultrasound or RF energy as methods of sending fixed time constant waves to the receiving wand.