Angle of rotation detector

• US 5,455,498 A
• Filed: 05/09/1991
• Issued: 10/03/1995
• Est. Priority Date: 05/09/1990
• Status: Expired due to Term

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Takahashi, Kuniyoshi, Nishina, Teruya, Kakimoto, Tatsumi, Fujisaki, Akiyoshi, Kubo, Takeshi
• Primary Examiner(s): Martin, David S.
• Application Number:
  US07/697,335
• Time in Patent Office: 1,608 Days
• Field of Search: 318/369, 318/600, 318/601, 318/604-605, 318/608, 318/638, 318/652-653, 318/656, 318/661, 341/111-117
• US Class Current: 318/605
• CPC Class Codes: G01D 5/243 influencing the phase or frequency of ac

Abstract

An angle of rotation detector has a drive unit which supplies 90 degree phase shifted signals to a pair of stator coils and measures an analog output from a rotor coil in a resolver. A calculating device calculates the rotational angle of the resolver using the output of an analog to digital converter receiving the analog output of the rotor. In one embodiment, the calculating device performs a Fourier transform to compute the phase of a fixed frequency component contained in the output of the rotor coil. In another embodiment, the drive unit supplies signals wherein f(T/2+t)=-f(t) and the calculating device performs a Fourier transform using data from successive half periods of the drive waveform. In another embodiment, the output of the rotor is sampled at 1/4 period of an excitation signal from the drive unit and the calculating device determines the phase difference between the excitation signal and the rotor output. In still another embodiment, the calculating device compares the outputs at two or more points having a fixed time relationship and compares the results to stored reference data to arrive at the angle of rotation.

Claims

1. An angle of rotation detector comprising:

a resolver having a rotor and two stators;

a drive unit connected to supply excitation signals phase-shifted by 90°

from each other to said two stators;

an analog to digital converter, connected to receive at an input of said converter an analog output of said rotor, said analog to digital converter having a digital output; and

means for calculating a rotational angle of said resolver, said calculating means being connected to receive said digital output, said calculating means being arranged to perform a Fourier transform to compute the phase of a fixed frequency component output by said rotor using an inverse trigonometric relationship.

2. An angle of rotation detector comprising:

a resolver having a rotor and two stators;

a drive unit connected to supply to said stators excitation signals wherein f(T/2+t)=-f(t), where t is time and T is period, Such that said excitation signals contain no even order harmonics, said excitation signals being phase-shifted 90°

from each other;

an analog to digital converter, connected to receive at an input of said converter an analog output of said rotor, said analog to digital converter having a digital output; and

means for calculating the rotational angle of the resolver, said calculating means receiving said digital output and being arranged to perform a Fourier transform using data from successive half-periods of the waveform of one of said drive signals to compute the phase of a fixed frequency component output by said rotor.

3. An angle of rotation detector comprising:

a resolver with a rotor and two stators;

a drive unit connected to supply to said stators excitation signals phase-shifted by 90°

from each other;

a sampler for sampling the output of said rotor each 1/4 period of the aforesaid said excitation signals;

an analog to digital converter, connected to receive at an input of said converter an analog output of said rotor from said sampler, said analog to digital converter having a digital output; and

means for calculating the rotational angle of the resolver by determining the phase difference between one of said excitation signals and said digital output.

4. The angle of rotation detector recited in claim 3 wherein said calculating means employs straight line interpolation based on two output samples, one of said samples taken before and the other after a zero crossing of said digital output.

5. The angle of rotation detector recited in claim 3 wherein said calculating means calculates the angle of rotation by determining a quotient of two data points sampled successively and then calculating an inverse tangent of said quotient.

6. The angle of rotation detector recited in claim 3 wherein said calculating means further comprises:

a detector for determining whether the outputs of the aforementioned A/D conversion device are above or below a specified value within an amplitude range for the rotor output, and in which of the four quadrants of the cycle the rotor outputs lie; and

means for determining the rotational angle of the resolver by calculating the inverse of the sine from the quadrant of the rotor output and a sampled data point.

7. An angle of rotation detector comprising:

a resolver having a rotor and two stators;

a drive unit connected to supply excitation signals phase-shifted by 90°

from each other to said two stators;

a sampler connected to sample at least two points of an output waveform of said rotor said points being different from each other and having a fixed time relationship with respect to the waveforms of said excitation signals;

an analog to digital converter, connected to receive at an input of said converter an analog output of said rotor from said sampler, said analog to digital converter having a digital output;

a memory for storing as reference data previously measured relationships between rotor output and angle of rotation; and

means for comparing the output of said A/D converter with said reference data in order to determine the resolver'"'"'s angle of rotation.

8. An angle of rotation detector comprising:

a resolver having a rotor and two stators,

a drive unit connected to supply excitation signals phase-shifted by 90°

from each other to the said two stators;

a sampler connected to sample an output waveform of said rotor at at least two points different from each other and having a fixed time relationship with respect to the waveforms of said excitation signals;

an analog to digital converter, connected to receive at an input of said converter an analog output of said rotor from said sampler, said analog to digital converter having a digital output;

a memory for storing as constants values which have been previously input for amplitude and phase of harmonic components of said excitation signals contained in the said rotor output; and

means for calculating an inverse trigonometric function using said digital output and the said constants in order to determine the rotational angle of the resolver.