Miniature pan/tilt tracking mount

• US 5,802,412 A
• Filed: 04/11/1997
• Issued: 09/01/1998
• Est. Priority Date: 05/24/1993
• Status: Expired due to Term

• Current Assignee: FLIR Systems, Inc. (Teledyne Technologies Incorporated)
• Original Assignee: Philip Kahn
• Inventors: Kahn, Philip
• Primary Examiner(s): Gray, David M.
• Application Number:
  US08/827,843
• Time in Patent Office: 508 Days
• Field of Search: 396/419, 396/427, 396/428, 396/429, 352/243, 352/38, 352/44, 352/53
• US Class Current: 396/427
• CPC Class Codes: F16M 11/10 around a horizontal axis F16M11/12 takes precedence
• CPC Class Codes: F16M 11/18 with mechanism for moving the apparatus relatively to the stand
• CPC Class Codes: F16M 11/2014 around a vertical axis F16M11/2035 takes precedence
• CPC Class Codes: G01S 3/7864 T.V. type tracking systems
• CPC Class Codes: G08B 13/1963 Arrangements allowing camera rotation to change view, e.g. pivoting camera, pan-tilt and zoom [PTZ]

Abstract

The invention is directed to a computer-controlled miniature pan/tilt tracking mount for the precise control of position, velocity, and acceleration of small payloads (e.g., a video camera). The invention consists of a motorized rotational tilt axis mounted atop a motorized rotational pan axis. For both axes, a worm gear mounted upon the motor shaft bidirectionally rotates a worm wheel mounted upon the orthogonal load axis shaft. A large ratio of motor size to armature weight provides high relative torque, speed, and accuracy. The worm gears provide compact reduction with minimal backlash and they can hold position without energized motors to conserve power for battery-operated uses. The invention includes integrated motor drive power electronics and microcontroller execution of host computer commands to effect precise control of pan/tilt mount speed, acceleration, position, configuration, and motor and electronics power consumption. Superior motor drive capabilities are achieved by the use of pulse-width modulation (PWM).

Claims

1. A method for one or more host computers to dynamically control and query the precise position, speed, and state of one or more pan/tilt mounts, comprising the steps of:

providing a pan/tilt controller, including a dedicated embedded processor for executing real-time pan/tilt control functions and processing of communications and commands from said one or more distinct and separate host computers, said embedded pan/tilt controller processor sharing no computational resources with said one or more host computers;

providing a motorized pan/tilt mount with minimal drivetrain backlash, motors and gearing that can precisely rotate the pan and tilt axes over a wide speed and acceleration range, and incorporating pan and tilt limit position detection sensors that are precise and highly repeatable;

said pan-tilt mount is electrically connected to the pan/tilt controller,

regulating either the current or voltage to windings of a pan motor and a tilt motor of said pan/tilt mount using said controller, and said controller receiving a set of pan and tilt position sensor feedback signals from said pan/tilt mount;

communicating between each of a set of one or more pan/tilt controllers and said one or more host computers, where each said host computer electrically is connected by a standard digital communications interface to provide a bi-directional communications link to each said pan-tilt controller;

wherein each of said one or more host computers can issue command signals to said controller to effect desired pan/tilt mount movement, and each of said one or more host computers can issue command signals to said one or more controllers to query current pan/tilt mount movement, position, status, and configuration;

calibrating absolute pan and tilt mount positions relative to a pan/tilt mounting point so that absolute pan and tilt positions may be precisely repeated;

wherein said calibrating step is initiated by at least one of the following events;

upon power being supplied to said pan-tilt controller, upon receiving a calibrate command signal from at least one of said one or more host computers;

setting precisely the absolute rotational speed and direction for pan and tilt movements according to a setting command signal received by said controller from at least one of said one or more host computers such that said controller can precisely and repeatably position the pan and tilt axes relative to said pan/tilt mounting point;

controlling the movements of said pan and tilt mount independently and concurrently according to signals from at least one of said one or more host computers and the particular pan/tilt controller of said one or more pan/tilt controllers associated with said pan and tilt mount;

parsing and executing incoming host computer commands by said one or more controllers concurrent with the execution by said controller of pan-tilt mount movements; and

executing position and speed command signals received by said pan/tilt controller from one of said one or more host computers without delay such that said command signals preempt the instructions of previous position and speed command signals that may not have yet completed.

2. The pan/tilt controller as in claim 1, further comprising the step of:

controlling the timing of when said one or more pan/tilt controllers begin executing desired pan/tilt actions to achieve coordinated multiaxis movements by said one of said one or more host computers.

3. The pan/tilt controller as in claim 2, further comprising the step of:

querying said pan/tilt controller to determine the current rotational speed and current absolute position of the pan and tilt axes even when said pan or tilt movements are in progress, using said one of said one or more host computers.

4. The pan/tilt controller as in claim 3, further comprising the step of:

providing one of said one or more host computers with communications feedback from said pan/tilt controller when a desired pan position has been attained when commanded to provide such communications feedback by such a one of said one or more host computers.

5. The pan/tilt controller as in claim 3, further comprising the step of:

providing one of said one or more host computers with communications feedback from said pan/tilt controller when a desired tilt position has been attained when commanded to provide such communications feedback by such a one of said one or more host computers.

6. The pan/tilt controller as in claim 3, further comprising the step of:

providing one of said one or more host computers with communications feedback from said pan/tilt controller when a desired pan position and a desired tilt position has been attained when commanded to provide such communications feedback by such a one of said one or more host computers.

7. The pan/tilt controller as in claim 3, further comprising the step of:

providing one of said one or more host computers with communications feedback from said pan/tilt controller when a desired pan speed has been attained when commanded to provide such communications feedback by such a one of said one or more host computers.

8. The pan/tilt controller as in claim 3, further comprising the step of:

providing one of said one or more host computers with communications feedback from said pan/tilt controller when a desired tilt speed has been attained when commanded to provide such communications feedback by such a one of said one or more host computers.

9. The pan/tilt controller as in claim 3, further comprising the step of:

providing one of said one or more host computers with communications feedback from said pan/tilt controller when a desired pan speed and a desired tilt speed has been attained when commanded to provide such communications feedback by such a one of said one or more host computers.

10. The pan/tilt controller as in claim 3, further comprising the step of:

precisely setting of a desired pan and tilt rotational speed as an offset from the current pan or tilt speed by the pan/tilt controller upon receiving a command signal from said one or more host computers.

11. The pan/tilt controller as in claim 1, further comprising the step of:

precisely setting of a desired pan and tilt rotational position as an offset from the current pan or tilt position by the pan/tilt controller upon receiving a command signal from said one or more host computers.

12. The pan/tilt controller as in claim 1, further comprising the steps of:

precisely setting of a desired pan and tilt rotational speed as an offset from the current pan or tilt speed by the pan/tilt controller upon receiving a command signal from said one or more host computers, and precisely setting of a desired pan and tilt rotational position as an offset from the current pan or tilt position by the pan/tilt controller upon receiving a command signal from said one or more host computers.

13. The pan/tilt controller as in claim 1, further comprising the step of:

precisely controlling changes in pan and tilt speed using said pan-tilt controller vary a rate of pan acceleration and tilt acceleration, according to command signals from said one or more host computers.

14. The pan/tilt controller as in claim 1, further comprising the step of:

varying the current levels applied to pan/tilt mount pan motor windings and tilt motor windings by said pan/tilt controller, according to command signals from said one or more host computers;

wherein the current applied to a stationary pan/tilt mount pan motor winding an be set independent from the current applied to a pan/tilt mount motor pan motor winding when the pan motor is turning,

wherein the current applied to a stationary pan/tilt mount tilt motor winding can be set independent from the current applied to a pan/tilt mount motor tilt motor winding when the tilt motor is turning, and wherein said one or more host computers can command said pan/tilt/controller to provide different magnitudes of motor winding currents to said pan motor and to said tilt motor when said motors are stationary as compared to when said pan and said tilt motors are turning.

15. The pan/tilt controller as in claim 1, further comprising the step of:

assigning a unique identifier to each pan/tilt controller, such that a first of said one or more host computers can communicate command signals and receive feedback signals from a selected controller, wherein said first of said one or more host computers may broadcast command signals to one or more of said one or more pan/tilt controllers.