Industrial position sensor

• US 6,057,777 A
• Filed: 07/31/1997
• Issued: 05/02/2000
• Est. Priority Date: 07/31/1997
• Status: Expired due to Term

• Current Assignee: Kama-Tech (HK) Limited
• Original Assignee: Laser Technology
• Inventors: Dunne, Jeremy G., Delohery, Patrick J.
• Primary Examiner(s): Hofsass, Jeffery A.
• Assistant Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US08/903,904
• Time in Patent Office: 1,006 Days
• Field of Search: 340/686.1, 340/686.2, 340/686.3, 340/686.4, 340/686.5, 340/686.6, 340/685, 340/436, 212/276, 414/273
• US Class Current: 340/686.1
• CPC Class Codes: B66C 13/46 Position indicators for suspended loads or for crane elements

Abstract

A sensor for determining the position of a movable object along a selected axis. The system includes a target positioned at a location aligned with the selected axis. An optical energy emitter is mounted on the movable object and has a beam dispersion greater than two degrees directed at the target. An optical energy receiver is mounted on the movable object and aligned to receive optical energy reflected by the target. The optical energy detector generates a receive signal indicating reception of the optical energy. A time of flight circuit coupled to the emitter and receiver generates a flight time signal indicating the elapsed time from emission of the optical energy to reception of reflected optical energy. A control circuit monitors the flight time signal and outputs a position signal indicating position of the movable object with respect to the target.

Claims

1. A spatial positioning system for determining the linear position of a movable object along a selected axis, comprising:

a target positioned at a location aligned with the selected axis;

a broad beam optical energy emitter mounted on the movable object and directed at the target;

an optical energy receiver mounted on the movable object and aligned to receive optical energy reflected by the target, the optical energy detector generating a receive signal indicating reception of the optical energy;

a time of flight circuit coupled to the emitter and receiver and generating a flight time signal indicating the elapsed time from emission of the optical energy to reception of reflected optical energy; and

a control circuit coupled to monitor the flight time signal and output a position signal indicating position of the movable object with respect to the target wherein the receive signal comprises a first signal indicating when the received power is greater than a preselected threshold and a second signal delayed from the first signal by an amount indicating the power of the received signal.

2. A spatial positioning system for determining the linear position of a movable object along a selected axis, comprising:

a target positioned at a location aligned with the selected axis;

a broad beam optical energy emitter mounted on the movable object and directed at the target;

an optical energy receiver mounted on the movable object and aligned to receive optical energy reflected by the target, the optical energy detector generating a receive signal indicating reception of the optical energy;

a time of flight circuit coupled to the emitter and receiver and generating a flight time signal indicating the elapsed time from emission of the optical energy to reception of reflected optical energy; and

a control circuit coupled to monitor the flight time signal and output a position signal indicating position of the movable object with respect to the target, said system further comprising;

integrity monitoring circuitry optically coupled to the optical energy receiver and generating optical energy, wherein the optical energy receiver indicates optical energy received from the integrity monitor.

3. A spatial positioning system for determining the linear position of a movable object along a selected axis, comprising:

a target positioned at a location aligned with the selected axis;

a broad beam optical energy emitter mounted on the movable object and directed at the target;

an optical energy receiver mounted on the movable object and aligned to receive optical energy reflected by the target, the optical energy detector generating a receive signal indicating reception of the optical energy;

a time of flight circuit coupled to the emitter and receiver and generating a flight time signal indicating the elapsed time from emission of the optical energy to reception of reflected optical energy; and

a control circuit coupled to monitor the flight time signal and output a position signal indicating position of the movable object with respect to the target wherein the receiver receives a signal comprising the reflected signal superimposed on optical energy background noise and the circuit further comprises;

a programmable reference voltage generator programmed to output a reference voltage indicating the background noise level, wherein the optical energy receiver generates the receive signal only after the power of the received optical energy is greater than the reference voltage.

4. A spatial positioning system for determining the linear position of a movable object along a selected axis, comprising:

a target positioned at a location aligned with the selected axis;

a broad beam optical energy emitter mounted on the movable object and directed at the target;

an optical energy receiver mounted on the movable object and aligned to receive optical energy reflected by the target, the optical energy detector generating a receive signal indicating reception of the optical energy;

a time of flight circuit coupled to the emitter and receiver and generating a flight time signal indicating the elapsed time from emission of the optical energy to reception of reflected optical energy; and

a control circuit coupled to monitor the flight time signal and output a position signal indicating position of the movable object with respect to the target wherein the position signal comprises a plurality of pulse width modulated (PWM) signals and the system further comprises;

a weighting network having inputs coupled to receive each of the PWM signals from the controller and having an output generating a signal comprising a weighted combination of the PWM signals;

an low pass filter coupled to the output of the weighting network and generating a voltage signal indicating position of the movable object with respect to the target.

5. A method for operating a spatial positioning system for determining the linear position of a movable object along a selected axis wherein the movable object is an overhead crane moving along rails defining a fixed span comprising the steps of:

mounting a reflective target at a location on the selected axis;

providing an optical energy emitter adjustably mounted on the movable object;

providing an optical energy receiver adjustably mounted on the movable target;

aiming the optical energy emitter at the target;

monitoring the power received by the optical energy receiver while adjusting the alignment; and

rigidly fixing the emitter and receiver to the movable object when the power received is above a preselected threshold, further comprising the step of positioning the movable object midway through the fixed span before the step of aiming the emitter at the target.

6. A spatial positioning system for determining a position of a movable object, comprising:

a target positioned at a reference location;

a first optical energy emitter mounted on the movable object and directed at the target;

a first optical energy receiver mounted on the movable object and aligned to receive optical energy reflected by the target, the first optical energy receiver generating a receive signal indicating reception of the optical energy;

a second optical energy emitter optically coupled with the first optical energy receiver;

a second optical energy receiver optically coupled with the first optical energy emitter, the second optical energy receiver generating a receive signal indicating reception of optical energy from the first optical energy emitter; and

an integrity monitor generating stimulus signals to the first and second optical energy emitters and monitoring the response of the first and second optical energy receivers to detect failure of either the first optical energy receiver or the first optical energy emitter.