US 4,905,207 A · Measuring distances using a plurality of frequencies

Abstract

Distance measurements are made using two or more signal frequencies. Ultrasonic energy is transmitted from a transducer to an object. Returned ultrasonic energy is received by the transducer and processed to provide an accurate determination of the distance between the transducer and the point on the object receiving the ultrasonic energy. In connection with the processing, a number of relationships are utilized. Using certain of the relationships, a range of integers is determined using high and low frequency ultrasonic energy, as well as propagation time. A time-related phase shift determination is also made for each of the high and low frequencies using certain of the other known relationships. Using a range of distance values and the measured time-related values, an accurate determination of distance from the transducer to the object can be made. In one application, a number of different distance values are obtained to define the surface plane of the object, such as a wheel or tire.

Claims27

Dependent claims

A method for measuring the distance to an object, comprising:

transmitting to the object a transmitted signal having a first frequency;
a transmitting to the object a transmitted signal having a second frequency, said second frequency being different from said first frequency;
receiving from the object a returned signal having said first frequency;
receiving from the object a returned signal having said second frequency;
determining a first magnitude relating to a coarse distance which relates to the coarse time taken by at least one of said first frequency signal and said second frequency signal to make a round trip to and from the object;
determining a second magnitude relating to a first fine distance and a first fine time, both of said first fine distance and said first fine time being associated with said first frequency signal;
determining a third magnitude relating to a second fine distance and a second fine time, both of said second fine distance and said second fine time being associated with said second frequency signal;
determining a whole number of signal cycles taken by said first frequency signal to make the round trip distance relative to the object and determining a whole number of signal cycles taken by said second frequency signal to make the round trip distance relative to the object, using at least said first magnitude;
and
using said second magnitude, said third magnitude, said whole number of signal cycles taken by said first frequency signal and said whole number of signal cycles taken by said second frequency signal in making a single determination of the distance to the object.

7 more elements

An apparatus for measuring distance to an object, comprising:

means for transmitting a transmitted signal having a first frequency and a transmitted signal having a second frequency;
means for receiving a returned signal having said first frequency and a returned signal having said second frequency;
and
means for processing responsive to said means for receiving for determining the distance to the object, said processing means including means:
for determining a first magnitude relating to propagation time using at least one of said first signal frequency and said second frequency,
for determining a second magnitude relating to a time difference between said transmitted signal and said returned signal, each having said first frequency,
for determining a third magnitude relating to a time difference between said transmitted signal and said returned signal, each having said second frequency,
for determining a whole number of signal cycles taken by said first frequency signal to make the round trip distance relative to the object and for determining a whole number of signal cycles taken by said second frequency signal to make the round trip distance relative to the object, using said first magnitude;
and wherein said processing means uses said second magnitude, said third magnitude, said first whole number of signal cycles and said second whole number of signal cycles to make a single determination of the distance to the object.

6 more elements

Dependencies are inferred from the claim text.

Measuring distances using a plurality of frequencies

Life of this patent

Measuring distances using a plurality of frequencies

Life of this patent

Abstract

Claims27