Non-contact laser displacement sensors are used to measure the thickness of polystyrene foam-extruded insulation boards in a continuous manufacturing environment. The boards are composed of foam sandwiched between plastic film. The rigid boards are continuously produced and cut to length at subsequent stages in the process.
The manufacturer needs a reliable and accurate thickness profile of the foam insulation boards for quality control and material waste projects. The system is composed of two, opposing laser displacement sensors that act as non-contact calipers for thickness measurement. The integrator plans to install this measurement system on a motorized, traversing linear slide so surface profiles can be collected. They know that a full thickness profile will help them to tighten the manufacturing process inputs and save on expensive petroleum-based polystyrene. Their goal is to produce panels to more strict dimensional tolerances.
In the above video, a pair of Acuity AR700 laser sensors measure the thickness of polystyrene board as it passes by. The sensors interface with a smart Touch Panel Display which calculates the thickness at 100 Hz based on the individual sensor distance measurements. This calculated thickness is transmitted via RS485 to a nearby PC computer for archiving purposes.
Once the sensors were properly fixtured directly above each other, with their emitted laser spots aligned, the demo took only 10 minutes to begin. The customer plans to use the solution with a linear stage to profile the thickness of board material in sections measuring 4 X 16 feet.
Profilometers provide high-quality measurements of pavement deformations at highway speeds. The equipment measures the longitudinal and transverse road profiles, International Roughness Index (IRI), wheel path rut depth, Ride Number (RN) and macro texture of asphalt and concrete surfaces.
Road profilers use multiple laser sensors to measure longitudinal and transverse road profiles at highway speeds
Road profiling equipment can be installed on a variety of vehicles. The system has 5 or more laser distance meters installed in the front of the vehicle. Each laser sensor measures the height between the vehicle body and the pavement surface at rates up to 3,500 measurements per second with a precision superior to 0.06mm. Measurements are made at the current transit speeds on city and highway roads ranging from 25 up to 140 km/hr.
Two encoder sensors provide measurements of the distances traveled by the vehicle, two accelerometers measure the vertical body bounce that the vehicle and the lasers experience when going over the pavement deformations, and a GPS device collects the geographic coordinates of the route traveled by the vehicle. The computer inside the vehicle simultaneously collects the measurements of all lasers, distance linear chainage, accelerometers and georeference.
Each laser measurement is influenced by the instant vertical movement of each sensor when driving over the pavement. Because of this, the accelerometers measure this movement and the computer program removes its influence when generating reports with the longitudinal and transversal profile of the pavement.
Each laser meter obtains a longitudinal pavement profile composed by more than 40,000 measures on each kilometer, approximately one measurement for every 2.54cm of travel!
With the simultaneous measurement of the 5 or more lasers, a transvere profile is obtained, which is used to calculate the rut depth for both wheel paths. This value reflects the structural weakness of the pavement produced by the transit load.
The international standard ASTM E950-98 dictates this type of measurements and classifies these types of Road Profilers within Class 1, which corresponds to the greatest precision. The IRI is calculated in accordance to the World Bank requirements.
The Block Qualifier is a height measurement device, used in the concrete brick and block industry. The Block Qualifier, uses non-contact laser measuring sensor technology to gauge the size of concrete bricks.
The concrete wall or paver blocks are manufactured in a similar way. Large steel molds are filled with a moist concrete mix, similar to wet sand. The material is heavily compressed while the entire mold is heavily vibrated. The green blocks are slid onto a steel palette which moves along a conveyor system.
The Block Qualifier system is an archway that places several laser displacement sensors above the moving palette. As the bricks travel under the archway, the sensors profile the height of the empty palette surface and the centerline of the blocks. Measurement statistics are captured for each palette and alarms are set for acceptable MINIMUM / MAXIMUM dimensions.
The manufacturing environment is particularly rough for precision sensors due to the heavy vibrations from the casting machine. The Block Qualifier design insulates the sensors from measurement noise created by the floor vibrations.
For more information about the Block Qualifier system for measuring concrete brick and block heights, please contact Rampf Molds, Inc.
A faculty member of the Agricultural Sciences Department at Aarhus University (Germany) uses a laser rangefinder in the Mobilas mobile canopy sensor.
Precision agriculture requires reliable technology to acquire accurate information on crop conditions. Based on this information, the amount of fertilizers and pesticides for the site-specific crop management can be optimized. Farmers turn to university research departments to assist in developing technology to help acquire this data.
Farming tractor with laser rangefinder from Acuity
Laser range measurements are made at a 50 degree off perpendicular angle. From 1024 range measurements canopy height and leaf area index (LAI) are calculated. The customer chose the AR4000 laser rangefinders from Acuity because of their high sampling rates and their ability to accurately measure in sunlit conditions. The AR4000 samples up to 50 KHz using an external high speed interface card that resides in a PC computer in the cab of the tractor.
A new manufacturer of foundation testing equipment developed the PileTrac Pile Set Monitor (PSM). The system improves the process for collecting and reporting pile set measurements during pile driving. Pile set is used to confirm pile driving requirements and for input into signal matching programs for prediction of static pile capacity.
Conventional pile set measurements (typically at end-of-initial drive or beginning of re-strike) are performed by placing a worker in close proximity to the pile and manually marking the pile between hammer impacts (see companion video). Conventional pile set measurement are often inaccurate with missed blows and/or marks or marks made without a fixed reference point.
The PileTrac Pile Set Monitor consists of an Acuity AR1000 laser rangefinder in combination with data acquisition and processing software to collect pile set data. The rangefinder is affixed to a stationary base and measures the The automated equipment is set up prior to starting of the hammer and does not require the use of manual recording methods.
Since data is acquired at a rate much faster than the hammer impacts, stable distance readings between the pile mounted target and ground mounted laser are achieved between hammer impacts which permits accurate computation of permanent set and blow count.
The PSM may be used for many other engineering and construction applications such as bridge deck deflection monitoring, confirmation of rod penetration during SPT sampling or for distance or displacement measurements to confirm performance of foundations or structural systems under loading.
For more information about this application or to get a quotation on a Piletrac PSM system, please contact Piletrac.
Design and implementation of a 3D laser scanner is no simple task, but the engineers at Ocular Robotics have done a commendable job with theirs. They have developed the RobotEye™ sensor pointing platform for use in mining applications, civil and defense UAV applications, homeland security applications and general robotics applications that are directly dependent on the dynamic performance.
Revolutionary 3D scanner to generate point clouds
RobotEye’s agility and responsiveness, its viewing range in both azimuth and elevation, and its reliability offers a ground- breaking contribution to robotic platform capability unmatched by current solutions. The RobotEye RE02 is a high performance, short range two-axis laser range scanner. The scanner has a signal path altered to accommodate the output and return signals of a commercial laser range finder which samples up to 200kHz to generate dense point clouds of the environment in the vicinity of robotic vehicles both indoors and outdoors, as well as object and environment reconstruction tasks.
The scan path flexibility of the RobotEye RE02 is unmatched by any other laser range scanning technology. All other laser range scanners have fixed pattern scans alterable only by changing the rotation rate of each axis. The RE02 is able to continuously vary its velocity controlled scan pattern to attain the desired point density and frame rate for a given situation as well as switch instantaneously to its arbitrary or structured path mode where regions may be scanned with any arbitrarily defined scan path.
These behaviours are made possible by the dynamic performance capabilities of the RobotEye technology and are implemented using the motion modes available on the controller such as 2D contouring, linear and circular interpolated vector segments and direct velocity control. In addition the controller has ample I/O to control and synchronise with system events.
RobotEye system components such as the brushless DC direct drive torque motors and high resolution magnetic encoders were selected to meet the performance and operational environment requirements of the demanding environments in the defense, natural resources exploration and homeland security sectors. The sensors, drive components and control electronics remain stationary and below the housing of the platform to which the system is mounted. The portion of the system that protrudes above the housing is environmentally sealed to a high degree, preventing entry of contaminants into the system. The system is designed to require little preventative maintenance in the harshest of environments.
Above is a Full Field and Region Scan Demo – shows RobotEye initially executing full field and region scanning behaviors with a laser pointer used to assist in visualising the motion (the actual rangefinder uses an infrared laser diode), followed by display of a point cloud dataset acquired by a RobotEye RE02 executing the same motion. The dataset is displayed raw as acquired from the sensor and was collected at a sample rate of 10kHz with the maximum possible sample rate from the sensor being 200kHz.
For more information about the laser rangefinder used in the RobotEye scanning system, please contact the manufacturer, Acuity.
For more information about the RobotEye system, please directly contact Ocular Robotics:
Sag of roofing shingle material to be measured by Acuity AR1000 laser distance sensor
A global manufacturer of fibreglass-based asphalt roofing shingles requested a demonstration of the AR1000 laser distance sensor to improve the performance of their production lines. The roofing shingle product is a laminated material produced in a continuous process where long stretches of material are draped between rollers while the material cures and is advanced towards automatic cutting stations.
Near the end of the process, before the material is cut into individual sheets, there is a large sag created by the mismatch of speeds between two rollers controlled by variable frequency drives. It is important to properly control this “slack”. If there is no sag, the material is held in tension and this could alter the product thickness or at worst, tear it. If there is too much sag in the material loop, the product collects on the floor and could ruin the product prior to packaging.
Current solution
The speed of the take-up roller is currently controlled using a series of two photo eyes at different heights. If the top photo eye does not detect the presence of the sag loop, it speeds up the delivery of material. If one photo eye detects the material, the delivery and take-up speeds are equal. If the bottom photo eye detects the loop, it means that the loop is too long (low) and the take-up needs to be sped up. The production process creates considerable dust and airborne debris which collected on the photo eye lenses and caused detection problems.
Process improvement using a non-contact distance meter
AR1000 distance sensor measures down to the bottom of the concave sag in fiberglass / asphalt roofing shingle
This customer wants better control over this process and needs a more precise measurement of the depth of the sag in material. The AR1000 was installed above the web process and aimed downward so that the laser spot measures to the bottom of the loop. A 4-20 mA analog signal transmits to a PLC which controls the speeds of the variable frequency drives. Although these laser rangefinders have been successfully implemented in similar applications, the integration engineers wanted to verify that the optical sensor could accurately measure to the dark asphalt material. The asphalt laminate is impregnated with colored granules and their presence offered an ideal measurement surface for excellent reflection of the laser. The device accurately measured the length of the sag loop to within a few millimeters at 5 Hz sampling speed. The orientation of the laser sensor was downward so little dust or debris could find its way up the dust protection tube of the AR1000 and obstruct the sensor lens.
A major North American propeller manufacturer and service company selected a long-range triangulation sensor to measure the profile of its propellers and controllable tip blades during the manufacturing process. Non-contact measuring, like that afforded by laser sensors, is desirable in propeller manufacturing because the fixed measuring device can be installed with a large standoff away from bulky and/or moving parts.
Propeller profiling using laser sensors
In this case, the customer chose a laser sensor that had the best resolution while allowing them to measure the greatest pitch of the largest propellers and blades (difference in height between the leading and trailing edge). The typical surface finish of the propellers was a shiny, ground appearance, and was no problem for the Acuity AR700 sensor with its highly-sensitive, digital CMOS detector array technology.
A recent journey to India brings us a novel application for a laser distance sensor. Even in a part of the world that tends to value the manual efforts of its laborforce, there is a strong recognition for precision, non-contact measurements afforded by the latest in sensor technology.
The Center for Rural Development and Technology at the Indian Institute of Technology Delhi thoroughly investigated the use of laser displacement sensors to measure the strain of samples during a particular materials testing experiment. Specifically, the Center was tasked with the evaluation of bamboo as a primary construction support material for use in projects in the most rural parts of India. Students within the Mechanical Engineering Department devised an experiment to test the compressive strength of bamboo.
Currently in their setup, they were using dial gauges which tended to “jump” as the force was increased during the experiment. The group investigated the laser sensor (Acuity model AR700) to measure the relative movement of two plates that moved together as the sample became compressed. They required a laser sensor with a long standoff so that it would not get harmed if the bamboo failed and shattered. The optoelectronic laser sensor with its analog output permitted the continuous acquisition of the distance output relative to other experimental variables.
Below is a video that shows the setup of the experiment. In the footage, the engineer adjusts the load by controlling the speed of a hydraulic piston controlled by an electric motor. The instantaneous position of the sample chuck is indicated on the visual Touch Panel Display.
Although now discountinued and replaced by the AR700 series, Michigan state selected the AR600-6 with a 150 mm measurement range. The laser has a 5mW visible laser spot and has excellent sensitivity for measuring to shiny targets. The sensor was mounted to dual rotational stages to allow two degrees of freedom. Their system swept the laser spot across the target surface to create polar cordinates for a 3D profile.
Acuity sensor on dual rotational stages
Graduate students developed software to control the laser, scan edges with specified step sizes. Output is distance, theta’, and phi’; convert laser coordinates to spherical coordinates; correct position for off axis rotation; and combine different reference systems; convert positions to final lab reference frame of choice. For each 0.01° step in angle, the position resolution was ~0.2mm.
Posted on May 26th, 2010 by admin
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