Measurement control device, contour measuring instrument and measurement control method

• US 20070266781A1
• Filed: 05/14/2007
• Published: 11/22/2007
• Est. Priority Date: 05/16/2006
• Status: Active Grant

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Nemoto, Kentaro, Yamamoto, Takeshi
• Granted Patent: US 7,784,333 B2
• Time in Patent Office: Days
• US Class Current: 73/105
• CPC Class Codes: G01B 21/04 by measuring coordinates of points
• CPC Class Codes: G01B 3/008 Arrangements for controlling the measuring force
• CPC Class Codes: G01B 5/012 Contact-making feeler heads therefor

Abstract

An approach controller (234) of a coordinate measuring instrument enables a position control loop (RP) and drives an actuator (133) so that a force sensor (1) is brought to a close position under a position control. When recognizing that the force sensor (1) reaches the close position, a contact controller (235) controls a switch (227) to enable a force control loop (RF) and drives the actuator (133) to bring the force sensor (1) into contact with a workpiece under a force control.

Claims

1. A measurement control device, comprising:

a probe including a force sensor that detects a measuring force generated when the probe contacts with a workpiece and outputs the measuring force as a force detection signal, a position detector that detects a measuring position of the workpiece detected by the force sensor and outputs the measuring position as measuring position information, and a force sensor moving unit that moves the force sensor relative to the workpiece;

a force control loop that compares the force detection signal from the force sensor as a force fed-back signal with a set force value and drives the force sensor moving unit such that the force fed-back signal becomes equal to the set force value;

a position control loop that compares the measuring position information from the position detector as a position fed-back signal with a set position value and drives the force sensor moving unit such that the position fed-back signal becomes equal to the set position value;

a control loop switcher that enables one of the force control loop and the position control loop;

an approach controller that controls the control loop switcher to enable the position control loop and drives the force sensor moving unit to position the force sensor in a close position that is close to the workpiece in such a manner that the position fed-back signal becomes equal to the set position value; and

a contact controller that, when recognizing that the force sensor is brought to the close position to the workpiece under the control of the approach controller, controls the control loop switcher to enable the force control loop and drives the force sensor moving unit to bring the force sensor into contact with the workpiece in such a manner that the force fed-back signal becomes equal to the set force value.

2. The measurement control device according to claim 1, wherein the force sensor includes a stylus having a contact section on a tip end thereof, a vibrating element that vibrates the stylus and a detecting element that detects a vibration state of the stylus and outputs the vibration state as a detection signal.

3. A contour measuring instrument, comprising:

a measurement control device that includes;

a probe including a force sensor that detects a measuring force generated when the probe contacts with a workpiece and outputs the measuring force as a force detection signal, a position detector that detects a measuring position of the workpiece detected by the force sensor and outputs the measuring position as measuring position information, and a force sensor moving unit that moves the force sensor relative to the workpiece;

a force control loop that compares the force detection signal from the force sensor as a force fed-back signal with a set force value and drives the force sensor moving unit such that the force fed-back signal becomes equal to the set force value;

a position control loop that compares the measuring position information from the position detector as a position fed-back signal with a set position value and drives the force sensor moving unit such that the position fed-back signal becomes equal to the set position value;

a control loop switcher that enables one of the force control loop and the position control loop;

an approach controller that controls the control loop switcher to enable the position control loop and drives the force sensor moving unit to position the force sensor in a close position that is close to the workpiece in such a manner that the position fed-back signal becomes equal to the set position value; and

a contact controller that, when recognizing that the force sensor is brought to the close position to the workpiece under the control of the approach controller, controls the control loop switcher to enable the force control loop and drives the force sensor moving unit to bring the force sensor into contact with the workpiece in such a manner that the force fed-back signal becomes equal to the set force value;

a probe holder that holds the probe of the measurement control device;

a probe-relative-movement unit that relatively moves the probe holder and the workpiece;

a probe position controller that controls the probe-relative-movement unit to position the force sensor of the probe and the workpiece such that the force sensor and the workpiece are positioned remoter as compared to the close position in the control of the approach controller of the measurement control device, wherein

when recognizing that the force sensor and the workpiece are positioned remoter as compared to the close position in the control of the probe position controller, the approach controller positions the force sensor and the workpiece close to each other.

4. A measurement control method using a measurement control device including:

a probe that includes a force sensor that detects a measuring force generated when the probe contacts with a workpiece and outputs the measuring force as a force detection signal, a position detector that detects a measuring position of the workpiece detected by the force sensor and outputs the measuring position as measuring position information, and a force sensor moving unit that moves the force sensor relative to the workpiece;

a force control loop that compares the force detection signal from the force sensor as a force fed-back signal with a set force value and drives the force sensor moving unit such that the force fed-back signal becomes equal to the set force value;

a position control loop that compares the measuring position information from the position detector as a position fed-back signal with a set position value and drives the force sensor moving unit such that the position fed-back signal becomes equal to the set position value; and

a control loop switcher that enables one of the force control loop and the position control loop, the method comprising;

controlling the control loop switcher to enable the position control loop and driving the force sensor moving unit to move the force sensor to a close position to the workpiece in such a manner that the position fed-back signal becomes equal to the set position value; and

controlling, when recognizing that the force sensor is brought to the close position to the workpiece, the control loop switcher to enable the force control loop and driving the force sensor moving unit to bring the force sensor into contact with the workpiece in such a manner that the force fed-back signal becomes equal to the set force value.