Fuzzy controls of towed objects

• US 9,323,236 B2
• Filed: 12/17/2012
• Issued: 04/26/2016
• Est. Priority Date: 12/05/2012
• Status: Active Grant

• Current Assignee: AAI Corporation (Textron Inc)
• Original Assignee: AAI Corporation (Textron Inc)
• Inventors: Plough, Matthew Hewit
• Primary Examiner(s): Patel, Ramesh
• Application Number:
  US13/716,850
• Publication Number:
  US 20140172173A1
• Time in Patent Office: 1,226 Days
• US Class Current: 1/1
• CPC Class Codes: G05B 13/024 in which a parameter or coefficient is automatically adjusted to optimise the performance
• CPC Class Codes: G05B 15/02 electric

Abstract

A fuzzy logic controller for controlling towed objects includes comprises a winch controller to control extension or retraction of a tow cable based on a control signal. A fuzzy logic controller controls a speed at which the tow cable is extended or retracted. The fuzzy logic controller includes an altitude controller storing a membership function defining ranges for a delta altitude variable and determines an altitude control signal based on the range for the measured delta altitude variable. A gain controller stores respective membership functions defining ranges for speed, heading rate, and cable length variables and determines a gain control signal based on the ranges for the determined speed, heading rate, and cable length variables. A command controller determines the control signal based on the gain control signal and the altitude control signal.

Claims

1. A controller for controlling objects towed by a vessel, comprising:

a winch controller to control extension or retraction of a tow cable based on a control signal;

a fuzzy logic controller coupled to the winch controller to control a speed at which the tow cable is extended or retracted, the fuzzy logic controller including;

an altitude controller storing a membership function defining ranges for a delta altitude variable and to determine an altitude control signal based on the range for the measured delta altitude variable;

a gain controller storing respective membership functions defining ranges for speed, rate of turn of the vessel, and cable length variables and to determine a gain control signal based on the ranges for the determined speed, rate of turn of the vessel, and cable length variables; and

a command controller to determine the control signal based on the gain control signal and the altitude control signal.

2. The controller of claim 1, wherein the fuzzy logic controller further comprises:

a speed sensor for sensing a speed of the vessel;

and

a cable length sensor to determine a length of the tow cable.

3. The controller of claim 1, wherein the fuzzy logic controller further comprises an altitude normalizer for normalizing the altitude control signal output of the altitude controller.

4. The controller of claim 1, wherein the fuzzy logic controller further comprises a gain normalizer for normalizing the gain control signal output of the gain controller.

5. The controller of claim 1, wherein the control signal is a product of the output of the gain control signal and the altitude control signal.

6. The controller of claim 1, wherein the fuzzy logic controller further comprises a control signal normalizer for normalizing the control signal.

7. The controller of claim 1, wherein the delta altitude variable defines a difference between a desired altitude and a measured altitude.

8. The controller of claim 1, wherein the fuzzy logic controller further comprises:

a speed controller, wherein when it is not possible to maintain an altitude of a towed object by retracting the tow cable, a full speed ahead request is made to the speed controller.

9. A method of fuzzy logic control of objects towed by a vessel, comprising:

determining ranges for a delta altitude, speed, rate of turn of the vessel, and cable length variables;

dividing the respective ranges into a plurality of regions defining respective membership functions;

measuring current values for each of the delta altitude, speed, rate of turn of the vessel, and cable length variables;

determining an altitude control signal based on the region of the membership function including the current values for the delta altitude variable;

determining a gain control signal based on the region of the membership function including the current values for the speed, rate of turn of the vessel, and cable length variables; and

determining a control signal for a winch controller to control extension or retraction of a tow cable based on the altitude control signal and the gain control signal.

10. The method of claim 9 further comprising:

sensing a speed of the vessel with a speed sensor;

and

determining a length of the tow cable with a cable length sensor.

11. The method of claim 9 further comprising normalizing the altitude control signal output of the altitude controller.

12. The method of claim 9 further comprising normalizing the gain control signal output of the gain controller.

13. The method of claim 9 further wherein the control signal is a product of the output of the gain control signal and the altitude control signal.

14. The method of claim 9 further comprising normalizing the control signal.

15. The method of claim 9, further comprising:

requesting full speed ahead when it is not possible to maintain an altitude for a towed object and a winch bandwidth has been exceeded.