Apparatus and method for extrapolating the angular position of a rotating body

• US 4,081,995 A
• Filed: 02/22/1977
• Issued: 04/04/1978
• Est. Priority Date: 02/22/1977
• Status: Expired due to Term

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: Watson, George A., Griffith, Glen R., Sandusky, Zane A.
• Primary Examiner(s): Ciarlante, Anthony V.
• Application Number:
  US05/771,056
• Time in Patent Office: 406 Days
• Field of Search: 73/116, 73/117.3, 123/117 D, 324/16 T, 235/150.21, 340/271
• US Class Current: 73/114.63
• CPC Class Codes: F02P 3/0456 using digital techniques
• CPC Class Codes: F02P 5/15 Digital data processing
• CPC Class Codes: F02P 5/1514 with means for optimising the use of registers or of memories, e.g. interpolation
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An apparatus and method for predicting the time occurrence of the desired angular position of a rotating body, such as the crankshaft of an internal combustion engine. The apparatus includes means for storing a nonlinearly changing count that is set to a known starting value when the rotating body is at a known angular position. A computing means is included for computing the value of the count that corresponds to the time when the rotating body will be at the desired angular position. The computation is achieved by extrapolating from known count information based upon prior periods of angular displacement of the rotating body during periods of known duration. In addition, the apparatus includes means for reducing the error associated with extrapolating the desired angular position of a rotating body undergoing either acceleration or deceleration by basing the extrapolation on a known period of angular displacement that occurred earlier than the most recent period of rotation immediately prior to the extrapolation process.

Claims

1. In a timing control system having a sensor device that provides a reference pulse at least once during each period of rotation of a rotatable member to indicate that the rotatable member is at a known angular position, a clock source for generating a periodic clockpulse signal, a counter responsive to the clock source for producing a pulse-count signal the value of which is a function of the number of clock-pulses generated, a computing device for receiving a plurality of signals that indicate a corresponding plurality of parameters for computing a count corresponding to a desired angular position of the rotatable member and for generating a signal representative of the desired angle count, and a comparator for receiving the pulse-count signal and the desired angle count signal and for producing a function initiating signal when the pulse-count signal and the desired angle count signal are equal;

an improved position extrapolation device comprising;

means in said counter for generating a count signal that is a non-linear function of time and for resetting said counter to a known starting count at each occurrence of said reference pulse,

means for sequentially storing the final non-linear count signal to occur immediately prior to each said resetting, and

means in said computing device responsive to said storing means and to said parameter indicating signals for computing and generating a signal representing the non-linear count corresponding to a subsequent desired angular position for producing a function signal, whereby a function signal is produced at a desired angular position that is based upon a non-linear extrapolation of a known angular position.

2. The position extrapolation device of claim 1 in which said non-linear count signal generating means comprises means for generating an exponentially decaying count X(t) that, between the occurrence of said references pulses, varies with time t substantially in accordance with

3. The position extrapolation device of claim 2 in which said exponentially decaying count generating means comprises:

means for storing a signal representing said starting count K,

means for dividing said stored signal by a signal representing said constant τ

to form a quotient signal,

means for subtracting said quotient signal from said stored signal and replacing said stored signal with a substitute stored signal representing the remainder of the subtraction, and

means controlling said storing means, said dividing means, and said subtraction means for cyclically dividing said substitute stored signal by the signal representing τ

, subtracting the resultant quotient signal from said substitute signal and replacing said substitute stored signal with another substitute signal representing the remainder of the last-mentioned subtraction.

4. An apparatus for predicting the occurrence of a desired angular position of a rotating body, having a sensor for sensing when the body is at a known angular position;

the apparatus comprising;

a. means for generating an electrical reference signal in response to said sensor,

b. means for generating an electrical count signal that corresponds to a non-linearly decreasing count that is set to a known starting value at an occurrence of said reference signal,

c. means for storing the count signal that corresponds to the value of said decreasing count immediately prior to each occurrence of a reference signal,

d. means for resetting said count signal generating means to said known starting value upon each subsequent occurrence of a reference signal,

e. means for computing the value of said decreasing count corresponding to the time when said rotating body will be at the desired angular position, basing said computation on said stored count signal, and

f. means for comparing said computed value and said decreasing count and determining when said decreasing count is equal to said computed value.

5. An improved apparatus for determining the occurrence of a desired angular position of a body rotating at increasing or decreasing angular velocity acting in combination with a sensor used in conjunction with the rotating body for sensing when the body is in a known angular position;

the apparatus comprising;

a. means for generating an electrical reference signal in response to said sensor,

b. means for generating an electrical count signal that represents a changing count that is set to a known starting value at the occurrence of said reference signal,

c. means for storing the count signal that corresponds to the value of said changing count immediately prior to each occurrence of said reference signal,

d. means for resetting said count signal generating means to said known starting value upon each subsequent occurrence of said reference signal,

e. means for computing extrapolated values of said changing count corresponding to the time when the rotating body will be at the desired angular position, said computation being based upon said previously stored count,

f. means for computing the difference between said extrapolated value and said previous count signal,

g. means for adding the difference computed by said difference computing means to a currently stored count signal to form a corrected count, and

h. means for comparing said corrected count and said changing count and determining when said changing count is equal to said corrected count.

6. An improved method of determining the approximate time of occurrence of a desired angular position of a rotating body wherein a sensor is used in conjunction with the rotating body for sensing the time when the body is at a known angular position;

the method comprising the following steps;

a. generating an electrical reference signal in response to said sensor.

b. generating an electrical count signal that corresponds to a non-linearly decreasing count that is set to a known starting value at the occurrence of said reference signal,

c. storing the count immediately prior to each occurrence of a reference signal,

d. setting said count signal to said known starting value upon each subsequent occurrence of a reference signal,

e. computing the value of said decreasing count that corresponds to the time when said rotating body will be at the desired angular position, basing said computation on said stored count signal, and

f. comparing said computed value and said decreasing count for determining when said decreasing count is equal to said computed value.

7. An improved method of extrapolating a desired angular position of a rotatable member of an engine with reduction in extrapolation errors due to acceleration, the method comprising the following steps:

a. generating a reference signal each time said rotatable member is at a predetermined angular position, to produce a series of such reference signals, the period of time between each pair of said reference signals being dependent upon the rate of rotation of said rotatable member;

b. generating a series of period signals, each such period signal representing a corresponding period of time between reference pulses;

c. computing said desired angular position upon the basis of an extrapolation from one of said periods prior to the most recent and generating a result signal representing the result of said computation;

d. subtracting from the result signal of step c, the period signal representing the period used in step c, to produce a remainder signal representing the remainder of said subtraction; and

e. adding the remainder signal of step d to the period signal representing the most recent one of said periods.

8. An improved method of determining the approximate time of occurrence of the desired angular position of a body rotating at increasing or decreasing angular velocity, wherein a sensor is used in conjunction with the rotating body for sensing the time when the body is at a known angular position;

the method comprising the following steps;

a. generating an electrical reference signal in response to said sensor,

b. generating an electrical count signal that represents a changing count that is set to a known starting value at the occurrence of said reference signal,

c. storing the count signal that corresponds to the value of said changing count immediately prior to each occurrence of a reference signal,

d. resetting said count signal to said known starting value upon each subsequent occurrence of a reference signal,

e. computing an extrapolated value of said changing count that corresponds to the time when the rotating body will be at the desired angular position, basing said computation upon said previously stored count,

f. computing the difference between said extrapolated value and said previously stored count signal,

g. adding the difference calculated in step (f) to a currently stored count signal to form a corrected count, and

h. comparing said corrected count and said changing count and determining when said changing count becomes equal to said corrected count.