Apparatus for sensing a failed position and velocity sensor

• US 4,864,284 A
• Filed: 12/08/1987
• Issued: 09/05/1989
• Est. Priority Date: 12/08/1987
• Status: Expired due to Fees

• Current Assignee: FMC Corporation
• Original Assignee: Caterpillar Incorporated
• Inventors: Kinas, Charles T., Crayton, John W., Sinn, Scott G.
• Primary Examiner(s): Orsino, Joseph A.
• Assistant Examiner(s): JACKSON, JILL
• Application Number:
  US07/130,060
• Time in Patent Office: 637 Days
• Field of Search: 340/670-672, 340/658, 340/635, 340/870.25, 324/163, 324/161, 73/488, 73/493, 73/510, 73/514, 318/605, 318/661, 361/236, 361/239, 361/242
• US Class Current: 340/635
• CPC Class Codes: G01P 21/02 of speedometers
• CPC Class Codes: G05D 1/0077 using redundant signals or controls
• CPC Class Codes: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00

Abstract

A self guided vehicle employs a highly accurate velocity sensor to determine vehicle speed and position. The velocity sensor includes a resolver connected to and rotatable with a ground engaging wheel. A resolver to digital converter (R/D) provides a highly accurate 8-bit digital signal representative of the angle of wheel rotation. A second less expensive and less accurate velocity sensor also receives the modulated sine and cosine signals from the resolver and produces a series of pulses representative of vehicle speed. The pulses are produced by detecting the zero crossings of the sine, cosine, and combinations of the sine and cosine signals. The velocity information present in the second velocity sensor signal is not used to actually guide the vehicle, but merely to generally validate the information present in the R/D signal.

Claims

1. An apparatus for detecting a failed velocity sensor of a work vehicle, the velocity sensor having a resolver connected to and rotatable with a ground engaging wheel of the work vehicle so that the resolver continuously delivers a signal and respectively deriving first and second periodic signals therefrom having rotational wheel position encoded therein, and a resolver to digital converter electrically connected to the resolver so that the resolver to digital converter continuously delivers a digital signal having a magnitude correlative to the wheel'"'"'s rotational position, the apparatus comprising:

a second velocity sensor electrically connected to the resolver and adapted for comparing the magnitude of the first periodic signal to a first preselected setpoint, comparing the magnitude of the second periodic signal to a second preselected setpoint, comparing the magnitudes of the first and second periodic signals, comparing the magnitude of the sum of the first and second periodic signals to a third preselected setpoint, differentiating the signals derived from the comparisons, and delivering a signal correlative to the rate of change of the first and second periodic signals; and

processor means for receiving the second velocity sensor signals and the resolver to digital converter signals, computing the rate of change of the digital signals, computing the rate at which the second velocity sensor signals are received, comparing the digital signal rate of change to the rate at which the second velocity sensor signals are received, and discontinuing operation of the vehicle in response to the difference in rates being outside a preselected range.

2. An apparatus, as set forth in claim 1, wherein the second velocity sensor includes first and second demodulators electrically connected to the resolver and adapted for receiving the resolver signal and respectively deriving the first and second periodic signals therefrom, first and second low pass filters configured for receiving the demodulated first and second periodic signals and passing signals within a preselected range, and wherein the second velocity sensor signal is delivered by means for generating pulses at a rate correlative to the frequency of the first and second periodic signals.

3. An apparatus for detecting a failed velocity sensor of a work vehicle, the velocity sensor having a resolver connected to and rotatable with a ground engaging wheel of the work vehicle so that the resolver continuously delivers a signal having rotational wheel position encoded therein, and a resolver to digital converter electrically connected to the resolver so that the resolver to digital converter continuously delivers a digital signal having a magnitude correlative to the wheel'"'"'s rotational position, the apparatus comprising:

a second velocity sensor having first and second demodulators electrically connected to the resolver and adapted for receiving the resolver signal and respectively deriving sine and cosine signals therefrom, and wherein the second velocity sensor signal includes;

means for receiving the sine signal, comparing the magnitude of the sine signal to a first preselected setpoint, and delivering a pulse in response to the magnitude of the sine signal being substantially equivalent to the first preselected setpoint;

means for receiving the cosine signal, comparing the magnitude of the cosine signal to a second preselected setpoint, and delivering a pulse in response to the magnitude of the cosine signal being substantially equivalent to the second preselected setpoint;

means for receiving the sine and cosine signals, comparing the magnitudes of the two signals, and delivering a pulse in response to the magnitude of the sine and cosine signals being substantially equivalent;

means for receiving the sine and cosine signals, adding the magnitudes of the two signals, and delivering a signal being the summation of the magnitudes of the sine and cosine signals;

means for receiving the summation signal, comparing the magnitude of the summation signal to a third preselected setpoint, delivering a pulse in response to the magnitude of the summation signal being substantially equivalent to the third preselected setpoint, and the second velocity sensor adapted for delivering a signal correlative to the rate of change of the resolver signal; and

processor means for receiving the second velocity sensor signals and the resolver to digital converter signals, computing the rate of change of the digital signals, computing the rate at which the second velocity sensor signals are received, comparing the digital signal rate of change to the rate at which the second velocity sensor signals are received, and discontinuing operation of the vehicle in response to the difference in rates being outside a preselected range.

4. An apparatus for detecting a failed velocity sensor of a work vehicle, the velocity sensor having a resolver connected to and rotatable with a ground engaging wheel of the work vehicle so that the resolver continuously delivers a signal having rotational wheel position encoded therein, and a resolver to digital converter electrically connected to the resolver so that the resolver to digital converter continuously delivers a digital signal having a magnitude correlative to the wheel'"'"'s rotational position, the apparatus comprising:

first and second demodulators electrically connected to the resolver and adapted for receiving the resolver signal and respectively deriving sine and cosine signals therefrom;

means for receiving the sine signal, comparing the magnitude of the sine signal to a first preselected setpoint, and delivering a pulse in response to the magnitude of the sine signal being substantially equivalent to the first preselected setpoint;

means for receiving the cosine signal, comparing the magnitude of the cosine signal to a second preselected setpoint, and delivering a pulse in response to the magnitude of the cosine signal being substantially equivalent to the second preselected setpoint;

means for receiving the sine and cosine signals, comparing the magnitudes of the two signals, and delivering a pulse in response to the magnitudes of the sine and cosine signals being substantially equivalent;

means for receiving the sine and cosine signals, adding the magnitudes of the two signals, and delivering a signal being the summation of the magnitudes of the sine and cosine signals;

means for receiving the summation signal, comparing the magnitude of the summation signal to a third preselected setpoint, and delivering a pulse in response to the magnitude of the summation signal being substantially equivalent to the third preselected setpoint; and

processor means for receiving the pulses and the digital signals, computing the rate of change of the digital signals, computing the rate at which the pulses are received, comparing the digital signal rate of change to the rate at which the pulses are received, and discontinuing operation of the vehicle in response to the difference in rates being outside a preselected range.

5. An apparatus for detecting a failed velocity sensor of an automatic guided vehicle having at least three wheels, and at least one of which is a powered drive wheel, the velocity sensor having a resolver connected to and rotatable with a ground engaging wheel other than the powered drive wheel so that the resolver continuously delivers a signal having rotational wheel position encoded therein, and a resolver to digital converter electrically connected to the resolver so that the resolver to digital converter continuously delivers a digital signal having a magnitude correlative to the wheel'"'"'s rotational position, the apparatus comprising:

first and second demodulators electrically connected to the resolver and adapted for receiving the resolver signal and respectively deriving sine and cosine signals therefrom;

means for receiving the sine signal, comparing the magnitude of the sine signal to a first preselected setpoint, and delivering a pulse in response to the magnitude of the sine signal being substantially equivalent to the first preselected setpoint;

means for receiving the cosine signal, comparing the magnitude of the cosine signal to a second preselected setpoint, and delivering a pulse in response to the magnitude of the cosine signal being substantially equivalent to the second preselected setpoint;

means for receiving the sine and cosine signals, comparing the magnitudes of the two signals, and delivering a pulse in response to the magnitudes of the sine and cosine signals being substantially equivalent;

means for receiving the sine and cosine signals, adding the magnitudes of the two signals, and delivering a signal being the summation of the magnitudes of the sine and cosine signals;

means for receiving the summation signal, comparing the magnitude of the summation signal to a third preselected setpoint, and delivering a pulse in response to the magnitude of the summation signal being substantially equivalent to the third preselected setpoint; and

processor means for receiving the pulses and the digital signals, computing the rate of change of the digital signals, computing the rate at which the pulses are received, comparing the digital signal rate of change to the rate at which the pulses are received, and discontinuing operation of the vehicle in response to the difference in rates being outside a preselected range.

6. A method for detecting a failed velocity sensor of a work vehicle, the velocity sensor having a resolver connected to and rotatable with a ground engaging wheel other than the powered drive wheel, so that the resolver continuously delivers a signal having rotational wheel position encoded therein, and a resolver to digital converter electrically connected to the resolver so that the resolver to digital converter continuously delivers a digital signal having a magnitude correlative to the wheel'"'"'s rotational position, the method comprising the steps of:

demodulating the resolver signal and respectively deriving sine and cosine signals therefrom;

comparing the magnitude of the sine signal to a first preselected setpoint, and delivering a pulse in response to the magnitude of the sine signal being substantially equivalent to the first preselected setpoint;

comparing the magnitude of the cosine signal to a second preselected setpoint, and delivering a pulse in response to the magnitude of the cosine signal being substantially equivalent to the second preselected setpoint;

comparing the magnitudes of the two signals, and delivering a pulse in response to the magnitudes of the sine and cosine signals being substantially equivalent;

receiving the sine and cosine signals, adding the magnitudes of the two signals, and delivering a signal being the summation of the magnitudes of the sine and cosine signals;

comparing the magnitude of the summation signal to a third preselected setpoint, and delivering a pulse in response to the magnitude of the summation signal being substantially equivalent to the third preselected setpoint; and

computing the rate of change of the digital signals, computing the rate at which the pulses are received, comparing the digital signal rate of change to the rate at which the pulses are received, and discontinuing operation of the vehicle in response to the difference in rates being outside a preselected range.