Method for evaluating mounting stability of articulated arm coordinate measurement machine using inclinometers

• US 9,009,000 B2
• Filed: 01/14/2011
• Issued: 04/14/2015
• Est. Priority Date: 01/20/2010
• Status: Expired due to Fees

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: York, Frederick John, Bailey, Brent
• Primary Examiner(s): Henson, Mischita
• Assistant Examiner(s): STIFTER JR, TERENCE E
• Application Number:
  US13/006,455
• Publication Number:
  US 20110178766A1
• Time in Patent Office: 1,551 Days
• Field of Search: 702/154
• US Class Current: 702/154
• CPC Class Codes: G01B 11/007 feeler heads therefor
• CPC Class Codes: G01B 21/047 Accessories, e.g. for positioning, for tool-setting, for measuring probes
• CPC Class Codes: G01B 5/012 Contact-making feeler heads therefor
• CPC Class Codes: G05B 19/401 characterised by control arrangements for measuring, e.g. calibration and initialisation, measuring workpiece for machining purposes G05B19/19 takes precedence
• CPC Class Codes: G05B 19/406 characterised by monitoring or safety G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/24067 Processor stores variables, events and date in eeprom, for external monitor
• CPC Class Codes: G05B 2219/37193 Multicoordinate measuring system, machine, cmm
• CPC Class Codes: G05B 2219/40233 Portable robot
• CPC Class Codes: G05B 2219/40596 Encoder in each joint
• CPC Class Codes: G05B 2219/45061 Measuring robot

Abstract

A portable articulated arm coordinate measurement machine can include a base, a manually positionable articulated arm portion having opposed first and second ends, the arm portion including a plurality of connected arm segments, an electronic circuit that receives the position signals from the transducers, a first inclinometer coupled to the base, wherein the inclinometer is configured to produce a first electrical signal responsive to an angle of tilt of the base and an electrical system configured to record a first reading of the first inclinometer and a second reading of the first inclinometer, wherein the first reading is in response to at least one of a first force applied to the base and a third force applied to the mounting structure, wherein the second reading is in response to at least one of a second force applied to the base and a fourth force applied to the mounting structure.

Claims

1. A method of evaluating and adjusting mounting stability of a portable articulated arm coordinate measuring machine (AACMM), the method comprising the steps of:

providing the AACMM, the AACMM having a manually positionable articulated arm portion, a base, a measurement probe, and a balance device, the arm portion having opposed first and second ends, the arm portion including a plurality of connected arm segments, each arm segment including at least one angular encoder for producing an angle of rotation signal, the arm portion being coupled to the base at the first end and to the measurement probe at the second end, wherein the base is configured to be attached to a structure, and wherein the balance device provides a balance force between the base and the first end;

providing an electronic circuit that receives the angle of rotation signals and determines a three dimensional coordinate of the measurement probe;

providing a first inclinometer coupled to the base, wherein the first inclinometer is configured to produce a first electrical signal responsive to an angle of tilt of the base with respect to a gravity vector;

providing an electrical system configured to receive the first electrical signal and measure the angle tilt of the base;

attaching the base to the structure;

moving by an operator a first arm segment to a first location, producing a first angle of rotation of a first of the encoders, a first balance force, and a first angle of tilt of the base;

measuring the first angle of rotation;

measuring the first angle of tilt of the base;

moving by the operator the first arm segment to a second location, producing a second angle of rotation of the first of the encoders, a second balance force, and a second angle of tilt of the base;

measuring the second angle of rotation;

measuring the second angle of tilt of the base;

determining a parameter related to the stability of the AACMM based at least in part on the measured first angle of rotation, the measured second angle of rotation, and a difference between the measured first angle of tilt of the base and the measured second angle of tilt of the base;

determining a source of error between the base and the structure based on the parameter;

indicating to the operator the source of error;

performing by the operator a step selected from the group consisting of adjusting the attaching of the base to the structure, and adjusting stability of the structure;

providing a second inclinometer configured to be mounted external to and separate from the AACMM and produce a second electrical signal responsive to an angle of tilt of the second inclinometer with respect to the gravity vector;

providing an I/O port of the AACMM to receive the second electrical signal and measure the angle of tilt of the second inclinometer;

measuring a first angle of tilt of the second inclinometer; and

wherein the step of determining a parameter is further based on the measured first angle of tilt of the second inclinometer.

2. The method of claim 1, wherein in the step of providing a manually positionable articulated arm, the balance device is a spring.

3. The method of claim 1, wherein:

in the step of providing a first inclinometer, the first electrical signal is responsive to the angle of tilt in two directions; and

in the step of providing an electrical system, the electrical system is further configured to measure the angle of tilt of the base in the two directions.

4. The method of claim 1, wherein in the step of determining a parameter, the parameter differentiates between the base and the structure as a source of error.

5. The method of claim 1, wherein in the step of determining a parameter, changes in tilts that are common mode to the first inclinometer and the second inclinometer are removed from the parameter.

6. The method of claim 1, wherein in the step of determining a parameter, the parameter is an indication of wobble of the base.

7. The method of claim 1, wherein in the step of determining a parameter, the parameter is an indication of wobble of the second inclinometer.