SURFACE PROPERTY MEASURING DEVICE AND CONTROL METHOD FOR SAME

• US 20200132428A1
• Filed: 10/04/2019
• Published: 04/30/2020
• Est. Priority Date: 10/24/2018
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: NAKAYAMA, Tatsuki
• Granted Patent: US 11,085,752 B2
• Time in Patent Office: Days
• CPC Class Codes: G01B 3/008 Arrangements for controlling the measuring force
• CPC Class Codes: G01B 5/0004 Supports G01B5/025 takes precedence
• CPC Class Codes: G01B 5/20 for measuring contours or curvatures
• CPC Class Codes: G01B 5/28 for measuring roughness or irregularity of surfaces

Abstract

A surface property measuring device includes a measuring arm that is supported so as to be capable of circular arced movement, a stylus that is provided to a distal end of the measuring arm, a position change detector that detects a change in position of the measuring arm, and a measurement force applier (voice coil motor) that biases the measuring arm in a circular arced movement direction and applies a measurement force. A control device includes a central controller that outputs a measurement force instruction that issues an instruction for an orientation and size of the measurement force, and a measurement force controller that controls the orientation and size of the measurement force produced by the measurement force applier. The measurement force controller monitors a position change detection, and when a position change speed of the measuring arm exceeds a predetermined threshold value, applies feedback.

Claims

1. A surface property measuring device comprising:

a surface property measuring instrument that measures a surface property of a measurable surface of a measurable object by performing tracing scanning of the measurable surface while in contact with the measurable surface, the surface property measuring instrument comprising;

a measuring arm capable of circular arced movement with a rotary shaft as a pivot point;

a stylus provided at a distal end of the measuring arm

a position change detector that detects a change in position due to the circular arced movement of the measuring arm; and

a measurement force applier that biases the measuring arm in a circular arced movement direction and applies a measurement force to the stylus;

a relative displacement motor that relatively displaces the surface property measuring instrument and the measurable object in three dimensions such that the surface property measuring instrument performs tracing scanning along the measurable surface; and

a controller that controls operations of the surface property measuring instrument and the relative displacement motor, the controller comprising;

a central controller comprising a memory that stores a set of executable instructions, and a processor which when executing the instructions, outputs a measurement force instruction that issues an instruction for an orientation and size of the measurement force; and

a measurement force control circuit that controls the orientation and size of the measurement force produced by the measurement force applier by applying a control signal to the measurement force applier, wherein the measurement force control circuit;

sets a predetermined threshold value for a position change speed of the measuring arm in accordance with the measurement speed of the surface property measuring instrument relative to the measurable object,

monitors a position change detection signal from the position change detector, and when the position change speed of the measuring arm is equal to or less than the predetermined threshold value, applies the control signal to the measurement force applier so as to produce a measurement force with an orientation and size corresponding to the measurement force instruction, and

applies feedback so as to produce in the measurement force applier a force in a direction that lifts the distal end of the measuring arm upward, when the position change speed of the measuring arm exceeds the predetermined threshold value.

2. The surface property measuring device according to claim 1, wherein the measurement control circuit comprises:

a measurement force instruction voltage generator that generates a measurement force instruction voltage that is a voltage signal that corresponds to a value of the measurement force instruction;

a feedback signal generator that generates a feedback signal that is a voltage signal that produces in the measurement force applier a force in a direction that lifts the distal end of the measuring arm upward;

a subtractor that subtracts the feedback signal from the measurement force instruction voltage; and

a decision circuit that, based on the position change detection signal from the position change detector, decides whether the position change speed of the measuring arm exceeds the predetermined threshold value, wherein when the decision circuit decides that the position change speed of the measuring arm exceeds the predetermined threshold value, the feedback signal is input to the subtractor.

3. The surface property measuring device according to claim 2, wherein the feedback signal generator comprises a frequency-voltage conversion circuit that generates a voltage signal that corresponds to a frequency value of the position change detection signal from the position change detector.

4. The surface property measuring device according to claim 2, wherein:

a switch is provided between the feedback signal generator and the subtractor, and the decision circuit;

sets the switch to ON when the position change speed of the measuring arm exceeds the predetermined threshold value, and

sets the switch to OFF when the position change speed of the measuring arm is equal to or less than the predetermined threshold value.

5. The surface property measuring device according to claim 3, wherein:

a switch is provided between the feedback signal generator and the subtractor, and the decision circuit;

sets the switch to ON when the position change speed of the measuring arm exceeds the predetermined threshold value, and

sets the switch to OFF when the position change speed of the measuring arm is equal to or less than the predetermined threshold value.

6. The surface property measuring device according to claim 4, wherein when the switch is OFF, the surface property measuring instrument measures the surface property of the measurable surface.

7. The surface property measuring device according to claim 5, wherein when the switch is OFF, the surface property measuring instrument measures the surface property of the measurable surface.

8. The surface property measuring device according to claim 1, wherein the measurement control circuit stores a threshold value table showing a correspondence between the measurement speed and the threshold value.

9. The surface property measuring device according to claim 2, wherein the measurement control circuit stores a threshold value table showing a correspondence between the measurement speed and the threshold value.

10. The surface property measuring device according to claim 3, wherein the measurement control circuit stores a threshold value table showing a correspondence between the measurement speed and the threshold value.

11. The surface property measuring device according to claim 4, wherein the measurement control circuit stores a threshold value table showing a correspondence between the measurement speed and the threshold value.

12. The surface property measuring device according to claim 5, wherein the measurement control circuit stores a threshold value table showing a correspondence between the measurement speed and the threshold value.

13. The surface property measuring device according to claim 6, wherein the measurement control circuit stores a threshold value table showing a correspondence between the measurement speed and the threshold value.

14. The surface property measuring device according to claim 7, wherein the measurement control circuit stores a threshold value table showing a correspondence between the measurement speed and the threshold value.

15. A control method for a surface property measuring device having a surface property measuring instrument having a measuring arm that is supported so as to be capable of circular arced movement with a rotary shaft as a pivot point, a stylus that is provided to a distal end of the measuring arm, a position change detector that detects a change in position due to the circular arced movement of the measuring arm, and a measurement force applier that biases the measuring arm in a circular arced movement direction and applies a measurement force to the stylus, the surface property measuring device further having a relative displacement mechanism that relatively displaces the surface property measuring instrument and a measurable object in three dimensions such that the surface property measuring instrument performs tracing scanning along a measurable surface of the measurable object, the method comprising:

controlling, via a controller, an orientation and size of the measurement force produced by the measurement force applier by applying to the measurement force applier a control signal that is based on a measurement force instruction that issues an instruction for the orientation and size of the measurement force;

setting, via the controller, a predetermined threshold value for a position change speed of the measuring arm in accordance with the measurement speed of the surface property measuring instrument relative to the measurable object;

monitoring, via the controller, a position change detection signal from the position change detector; and

applying, via the controller, the control signal to the measurement force applier so as to produce a measurement force with an orientation and size corresponding to the measurement force instruction, when the position change speed of the measuring arm is equal to or less than the predetermined threshold value and

applying, via the controller, feedback so as to produce in the measurement force applier a force in a direction that lifts the distal end of the measuring arm upward, when the position change speed of the measuring arm exceeds the predetermined threshold value.