The purpose of this study is to develop with low cost, high precision, low contact force micro-CMM that has fiveaxis scanning touch probe. In this study, the measurement performance of the proposed system is enhanced through the use of a rigid aluminum double-arch-bridge structure to support the five-axis scanning touch probe. Furthermore, the reliability of the scanning probe mechanism of three degrees of freedom was analyzed and validated. in addition two axis (A-axis and C-axis) was added on the scanning probe. This design can be achieved independent of measurement, and minimize the dynamic error. In terms of software, a PC-Based controller was integrates five-axis motion systems with the measurement system through a five-axis control card and a data acquisition card. It also completed the functional modules of Set, Manual and Measurement. In the measurement system, we used our own developed coordinate measurement software, with the XYZ platforms system, rotating mechanism and scanning probe to achieve complex surface measurements. The micro-CMM has a working volume the micro-CMM has a working volume of 80×80×40 mm3 , and the overall dimensions is 486 × 486 × 448 mm.
KEYWORDS: Signal processing, Optical design, Sensors, Structural design, Semiconductor lasers, Beam splitters, 3D scanning, Computer programming, Position sensors, 3D metrology
The purpose of this study is to develop a five-axis scanning touch probe with high precision and low contact force. The development of scanning touch probe is consisted of three parts: mechanism design, optical path design, and rotation structure design. The mechanism design contains three parts, Z-axis system, XY-axis system, and probe mechanism. The Z-axis system applies the characteristic of the thin sheet spring to move vertically. In the design of XY-axis system, a micro-beam is employed, through which length, width, and thickness of the micro-beam and corresponding dimensions of the leaf spring are designed according to the selected contact force. The freedom degree is limited to three. And the center of the mechanism is equipped with a stylus to inhibit displacement of the Z-axis. The contact between the probe and the work piece only leads to change in the angles of X- and Y-axes, achieving the feature of 2-degree freedom. To enable rapid change for the probes, this study designs a probe mechanism, reliability of which is analyzed and validated with ANSYS software, so that the design of 3-degree freedom mechanism is completed. The sensor has a laser diode to coordinate with Position Sensor Detector (PSD) which works with the optical path designed to measure placement of Z-axis and angle placement of XY-axis. The rotation structure refers to the principle of 5-axis machining design, and the two rotary axes (A- and C-axis) to join the self-developed scanning probe. This design can achieve independent measurements and eliminate the dynamic measurement error that three-axis scanning systems typically have. By validation through an experiment, the three-dimensional scanning touch probe developed by this study has a measuring range of ±1mm×±1mm×1mm, and unidirectional repeatability of 0.6μm.
This paper presents a three-degree-of-freedom hybrid vibration isolation system integrated with an active sky-hook damper and a passive weight support mechanism for highly sensitive measurement equipment, e.g. atomic force microscopes, suffering from building vibration. Active sky-hook damper applies proportional controller incorporated with an adaptive filter to reduce the resonance of the passive weight support mechanism at nature frequency. The absolute vibration velocity signal acquired from an accelerator and being processed through an integrator is input to the controller as a feedback signal, and the controller output signal drives the voice coil actuator to produce a sky-hook damper force. The adaptive filter is used to compensate the phase error between the measuring input signal and the absolute vibration velocity. An analysis of this active vibration isolation system is presented, and model predictions are compared to experimental results. The results show that the system could effectively reduce transmissibility at resonance without the penalty of increased transmissibility at higher frequencies both in vertical and horizontal directions.
This study develops a micro-CMM incorporating a scanning touch probe and a high-precision coplanar platform. The measurement performance of the proposed system was enhanced through the use of a rigid aluminum double-arch-bridge structure to support the scanning touch probe. For the working stage, a linear motor was used for long-stroke positioning and a piezoelectric actuator was then employed to fine-tune the positioning so as to achieve a requirement of highprecision. The platform has two characteristics: (i) the driving and measuring axes are designed along the same line so that Abbe error of the stage can be eliminated; (ii) the coplanar design makes the X and Y axes reach a goal of two-axis concurrent. The aforementioned two designs can reduce the error of the platform so that the micro-CMM reaches a positioning accuracy of ±0.1μm for a working volume of 80×80×40 mm3. Furthermore, the reliability of the probe mechanism of three degrees of freedom was analyzed and validated. The sensor coordinates a laser diode with Position Sensor Detectors (PSD) working with an optical path to measure placement of Z-axis and angle placement of XY-axis. By validation through an experiment, the three dimensional scanning touch probe developed by this study has a measuring range of ±1mm × ±1mm × 1mm with a unidirectional repeatability of 0.6μm.
An active vibration isolation system that applies proportional controller incorporated with an adaptive filter to reduce the transmission of base excitations to a precision instrument is proposed in this work. The absolute vibration velocity signal acquired from an accelerator and being processed through an integrator is input to the controller as a feedback signal, and the controller output signal drives the voice coil actuator to produce a sky-hook damper force. In practice, the phase response of integrator at low frequency such as 2~5 Hz deviate from the 90 degree which is the exact phase difference between the vibration velocity and acceleration. Therefore, an adaptive filter is used to compensate the phase error in this paper. An analysis of this active vibration isolation system is presented, and model predictions are compared to experimental results. The results show that the proposed method significantly reduces transmissibility at resonance without the penalty of increased transmissibility at higher frequencies.
This study aims to develop a three dimensional scanning touch probe with high precision and low contact force. The overall design has two parts, mechanism design and optical path design. The mechanism design contains three parts, Zaxis system, XY-axis system, and probe mechanism. The Z-axis system applies the characteristic of the thin sheet spring to move vertically. In the design of XY-axis system, a micro-beam is employed, through which length, width, thickness of the micro-beam and corresponding dimensions of the leaf spring are designed according to the selected contact force. The freedom degree is limited to three. And the center of the mechanism is equipped with a stylus to inhibit displacement of the Z-axis. The contact between the probe and the workpiece only leads to change in the angles of Xand Y-axes, achieving the feature of 2-degree freedom. To enable rapid change for the probes, this study designs a probe mechanism, reliability of which is analyzed and validated with ANSYS software, so that the design of 3-degree freedom mechanism is completed. The sensor has a laser diode to coordinate with Position Sensor Detector (PSD) which works with the optical path designed to measure placement of Z-axis and angle placement of XY-axis. By validation through an experiment, the three dimensional scanning touch probe developed by this study has a measuring range of ±1mm×±1mm×1mm, and unidirectional repeatability of 0.6um.
This study develops a low-cost three-dimensional touch trigger probe for micro-CMM using micro spherical stylus
machining by micro-EDM. The tip ball of the stylus, with a diameter smaller than 100 μm, is made by a micro electro
discharge machine with the method of wire electro discharge grinding (WEDG). The current study uses tungsten
carbide (WC) as the material for the stylus. Experimental results show that, the tip ball roundness could amount to 2
μm. Since the tip ball is not easily observable by naked eyes, we designed a micro imaging system to observe the
probing in real time. This system is created with modified commercial webcam and microscope.
The general design of the touch trigger probe is combined the stylus and suspension structure. When the stylus touches
workpiece, it can be determined the time of probe trigger by measuring the motion of suspension structure. The stylus
machined by micro-EDM was very fragile and the stylus handle of the tip ball was very thin. Therefore, the stylus handle
bends easily that would result in the large measurement error or stylus break when the stylus touched workpiece. In this
study we designed a measuring probe using a small chuck and an electrical circuit to measure the probe trigger. When
the stylus touches the workpiece, the parallel circuit will switch on immediately and pick up the voltage variation of the
resistor. Because the transistor always turns ON, it can avoid the problems of excessive energy and electrical noise.
This study develops a low-cost, highly-sensitive, three-dimensional optical accelerometer in which the seismic mass
comprises four rectangular blocks attached to the ends of a cross-form aluminum structure suspended on four thin steel
strips. It is shown through ANSYS finite element (FE) simulations that the thin-strip suspension system restricts the
seismic mass to just three degrees of motional freedom, namely one translational motion in the vertical direction and two
rotational motions. These displacements are detected using two novel optical sensors based on commercial DVD optical
pick-up heads. When the accelerometer experiences a vibrational force, the relative motion between the seismic mass
and the base results in a change in the distribution of the reflected light spots on the surfaces of the four-quadrant
photodetectors within the two pick-up heads. The resulting changes in the output voltage signals of the two pick-up
heads are then used to calculate the corresponding acceleration of the base. The experimental results indicate that the
resonance frequencies of the accelerometer in the X, Y and Z-axis directions are 130.51 Hz, 130.63 Hz and 130.90 Hz,
respectively. Meanwhile, the sensitivities of the accelerometer in the X, Y and Z-axis directions are 21.28 V/g, 22.94 V/g
and 22.75 V/g, respectively.
This study develops a novel optical encoder based on two commercially available DVD optical pick-up heads and a
single reflective grating with a sinusoidal surface profile. In the proposed configuration, the laser beams output from the
two pick-up heads are passed through a beam splitter and an objective lens and are focused on the surface of the grating.
By adjusting the distance of the two DVD pick-up heads from the grating and carefully controlling their angles of
rotation in the X-Y plane, the distance between the two focus spots on the grating surface is regulated such that it equals
one quarter of the grating pitch. When the grating is displaced, the laser spots trace the surface of the grating, causing a
shift in the position of the reflected light beams on the four-quadrant photodiodes within the DVD pick-up heads. The
resulting quadrature sinusoidal signals output by the pick-up heads are processed to generate two square-wave signals
with a 90° phase difference and a triangular waveform, respectively. By counting the zero crossings of the square waves
and interpolating the triangular waveform, both the direction and the value of the grating displacement can be derived.
This study develops a low-cost, highly sensitive two-dimensional optical accelerometer based on a commercially available DVD optical pick-up head. Vibrations of the structure of interest cause a change in the angle of the seismic mass within the accelerometer. The relative movement between the seismic mass and the base produces a change in the distribution of a focused light spot on the surface of a four-quadrant photodetector. The resulting change in the voltage signals output by the photodetector is then used to calculate the corresponding acceleration of the base. The experimental results indicate that the sensitivities of the accelerometer in the X- and Y-axis directions are 22.9 V/g and 21.3 V/g, respectively.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.