Spatial RAM for high precision data acquisition systems

• US 6,266,581 B1
• Filed: 05/09/1997
• Issued: 07/24/2001
• Est. Priority Date: 05/10/1996
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Commerce
• Original Assignee: THE GOVERNMENT OF THE UNITED STATES OF AMERICA, AS REPRESENTED BY THE SECRETARY OF COMMERCE
• Inventors: Teague, E. Clayton, Wheatley, Thomas
• Primary Examiner(s): Grant, William
• Assistant Examiner(s): Robinson, Victoria
• Application Number:
  US08/853,586
• Time in Patent Office: 1,537 Days
• Field of Search: 364/528.37, 364/141, 364/148
• US Class Current: 700/302
• CPC Class Codes: G05B 21/02 electric

Abstract

A spatial RAM system uses the position of a data sensor to generate a clock pulse that is used to trigger data acquisition. As a consequence, the errors associated with time-based clock sampling are avoided. This enables more accurate sampling of data at locations desired in space and more easily allows for non-uniform sampling.

Claims

1. A method for activating a function of a system based on the position in space of a component of the system relative to an object of interest, using spatial position data output from a movable position sensor associated with and movable with said component, said method comprising the steps of:

(a) reading a memory address containing a first plurality of target bits representing a first target spatial position of the component;

(b) determining from spatial position data output from said position sensor a first actual position of the component in space relative to the object;

(c) representing said actual position by a second plurality of bits;

(d) comparing at least one of said first plurality of bits with a corresponding set of said second plurality of bits; and

(e) if said compared bits are equivalent, activating said function and then proceeding again beginning with step (a) using a further plurality of target bits, or

(f) if said compared bits are not equivalent, moving said component and the associated position sensor through a space to a further actual spatial position and proceeding again beginning with step (b) using said further actual position and a further plurality of actual position bits representing said further actual position.

2. A method according to claim 1 wherein said function comprises at least one function selected from the group consisting of (1) acquiring data using a data sensor, (2) emitting a first signal, and (3) emitting a second signal and receiving said second signal.

3. A method according to claim 2 further comprising resetting a state machine of the system after acquiring data in step (e) so as to be prepared to determine another representation of said actual position.

4. A method as claimed in claim 2 wherein said component comprises a data sensor and when said function is activated, said data sensor acquires data.

5. A method according to claim 1 wherein said comparing step further comprises comparing bits of lesser relative significance.

6. A method according to claim 5 further comprising upon a first successful match of said compared bits of lesser relative significance, comparing bits of greater relative significance, and upon a second successful match, proceeding to said acquiring step.

7. A method according to claim 6 wherein said first successful match of latches a flip-flop to enable said bits of greater significance to be compared.

8. A method according to claim 6 further comprising pulsing a count input if said second successful match is determined so as to acquire data.

9. A method according to claim 1 further comprising storing a plurality of target positions in said memory address.

10. A method according to claim 9 wherein said target positions are linearly spaced over said object.

11. A method according to claim 9 wherein said target positions are spaced non-linearly over said object.

12. A method according to claim 9 wherein said target positions are spaced in a non-uniform manner over said object.

13. A method according to claim 9 wherein said system is a data acquisition system and said acquiring step further comprises the step of sending a clock pulse to said data acquisition system to enable said data acquisition system to acquire data.

14. A method according to claim 9 further comprising stopping said method after acquiring data corresponding to a last target position.

15. A method according to claim 9 wherein said data acquisition proceeds uni-directionally across a surface of said object.

16. A method according to claim 9 wherein said data acquisition proceeds bi-directionally across a surface of said object.

17. A method according to claim 1 further comprising switching the counting direction of a counter if a last value is reached in a bi-directional mode.

18. A data acquisition system for acquiring data about an object of interest based on positional information regarding the relative position of the system with respect to the object, said system comprising:

a movable data sensor for acquiring data about the object of interest responsive to being activated based on the spatial position of said spatial data sensor relative to the object of interest;

a position sensor, movable with said data sensor, for sensing the actual position of said data sensor and for producing, responsive to the actual position sensed, a plurality of actual position data bits;

memory means for storing a plurality of target positions of said data sensor, each target position being represented by a plurality of bits;

means for comparing the plurality of actual position bits and a first of the plurality of the target position bits; and

a state machine, including a flip-flop, having a plurality of states for operating the system such that a first state causes both a first set of the first target position bits and a corresponding first first set of the plurality of the actual position bits to be read into the comparing means, a second state causes the comparing means to compare the first set of bits with the corresponding first portion of bits, and to latch the flip-flop upon a successful match that sends a clock pulse to the data sensor in order to acquire data from the object.

19. A system according to claim 18 wherein said function activating means is selected from the group consisting of (1) means for acquiring data, (2) means for emitting a signal and (3) means for emitting a sent signal and for receiving said sent signal.

20. A system according to claim 19 wherein said state machine further comprises a third state and a fourth state that are activated after the latch of said flip-flop and before said clock pulse is sent, wherein said third state, entered upon latching of the flip-flop, gathers a second portion of the first target position bits and a second corresponding portion of the actual position bits, and said fourth state compares the second portion bits with the second corresponding portion bits and sends said clock pulse upon a successful match of the comparison between the second portion bits and the second corresponding portion bits to the data acquiring means in order to acquire data from the object.

21. A system according to claim 20 wherein said state machine further comprises a counter having an up/down pin to indicate in a bi-directional data acquiring mode whether to count up or down to correspond to an up direction or a down direction, and a fifth state switches said up/down pin upon reaching a last value in either said up direction or said down direction.

22. A system according to claim 21 wherein said state machine further comprises a count input, and a sixth state that pulses said count input upon determining a successful match of both of said first portion with said first corresponding portion and of said second portion with said second corresponding portion.

23. A system according to claim 22 wherein said state machine further comprises a seventh state that resets said state machine to await another data sample from said data acquiring means.

24. A system according to claim 19 wherein said first portion and said first corresponding portion are the lower sixteen bits of a pair of 32 bit words, and said second portion and said second corresponding portion are the upper 16 bits of said pair of 32 bit words.

25. A method for acquiring data with respect to an object using a system including a data sensor and an associated position sensor movable with said data sensor based on the spatial position of said data sensor relative to the object, said method comprising the steps of:

(a) storing in a memory target spatial positions of said data sensor;

(b) loading one of said target spatial positions into a comparator from said memory;

(c) determining the actual spatial position of said data sensor based on position data received from said position sensor and producing a corresponding actual spatial position output;

(d) using said comparator to compare said one target spatial position and said actual spatial position; and

either

(e) if said one actual spatial position and said target spatial position are equivalent, acquiring data with said data sensor and then continuing with step (b), or

(f) if said one actual spatial position and said target spatial position are not equivalent, moving said data sensor and position sensor through space to a further actual position and continuing with step (c).