TRIMBLE ATS TOTAL STATION ADVANCED TRACKING SYSTEMS FOR HIGH-PRECISION CONSTRUCTION APPLICATIONS

Transcription

1 TRIMBLE ATS TOTAL STATION ADVANCED TRACKING SYSTEMS FOR HIGH-PRECISION CONSTRUCTION APPLICATIONS BY MARTIN WAGENER APPLICATIONS ENGINEER, TRIMBLE EUROPE

2 OVERVIEW Today s construction industry demands more and more applications require high-precision positioning for earthmoving construction machines such as graders and dozers. The Trimble Advanced Tracking Sensors (ATS) Total Station helps contractors meet these increasingly stringent job specifications. INTRODUCTION The Trimble ATS Total Station is an Advanced Tracking Sensor that is based on the concept of optical surveying total stations. The ATS Total Station is a robotic total station designed to remotely track and measure a kinematic moving target, continuously sending the measured data to a controlling computer and operating software. To operate as a robotic total station, the Trimble ATS offers the standard features of traditional total stations. The ATS total station also has servo drives for endless motion, a special tracker unit which ensures the correct prism is detected, allowing the system to follow the target, and a built-in telemetric radio which provides low-latency, two-way communication with the controlling computer. Figure 1: Trimble ATS Total Station POSITIONING Robotic operation in combination with real time kinematic measurements provides the Positioning operation, where the system tracks and measures the moving target delivering the 3D position continuously to the controlling computer. In most applications, the target s positioning information relative to a definition point on the moving machine is used to deliver location information, which is then combined with information from other sensors, such as laser scanners, echo beams, or atmospheric condition sensors by the controlling computer. CONVENTIONAL AND 3D MACHINE CONTROL Construction applications are categorized into conventional Machine Control and 3D-Machine Control operations. In the conventional operation, lasers normally are only required to work to a defined height and/or sloping plane. For these applications over the past 40 years, rotating lasers have been a very common and beneficial way of controlling a construction machine. Within the last few years, 3D-Machine Control operations have become increasingly important. The 3D digital data from the design software is used onboard the machine and complete site control is done from inside the machine. The same measurements performed in the Positioning operation are sent to the on-machine controlling computer which calculates in real time the correction values for the blade of the earthmoving machine. The controlling software compares the actual position of the edges of the blade, or any other definition point, against the design at that specific position when measured. With manual operation, the machine operator gets a visual indication of the corrections for both sides of the blade. Based on this information, he then can change the blade to the finished design. With an automatic machine control system, the controlling computer controls the whole system and automatically changes the position of the blade to the design position by sending the relevant information to machine s hydraulic valve control system in real time. 2

3 In construction operations, several machine types can be equipped with a machine control system. Graders and dozers have been the typical earthmoving machines which were controlled and monitored by the systems. More recently, pavers, rollers and excavators are also being controlled. However, machine control systems are not limited only to construction machines. 3D-Control systems are also used in hydrographical marine applications and in real-time kinematic railroad measurements. Ongoing Trimble ATS Total Station development was driven by: (1) specific demands for a highly reliable tracking station able to perform kinematic and tracking operations for a full day, and (2) the need for total remote-controlled operation from inside the machine cab. Despite its special features for construction applications, the Trimble ATS Total Station can be used in all standard surveying applications. Contractors have benefited from Trimble s extensive experience and reputation for consistent, high-quality and reliability. SYNCHRONIZED DATA MEASUREMENTS Standard total stations are optimized for static prism measurement. In contrast, synchronization of data from the angle and distance measurement sensors allows output data to be computed for a single instantaneous location of the moving machine. This results in higher 3D position accuracy for dynamic measurements or machine tracking applications. Figure 2: Trimble ATS Total Station in Machine Control operation TRIMBLE ATS TOTAL STATION FEATURES AND BENEFITS Although the Trimble ATS looks like an ordinary Robotic total station, the following features and benefits differentiate it from any other optical total station. TRIMBLE ATS EVOLUTION In early 1995, the first tests were performed for a machine control operation using a standard optical Robotic total station Geodimeter Immediate test results indicated that, for kinemetic operations compared to standard surveying applications, the instrument had to improve the way it measured and sent data to the control computer. Specifically, higher output rate of measurement and synchronized angle and distance reading were required. Figure 3: Principle of synchronized measurement data Synchronization is a measure of how closely together in time the various polar coordinates that form the data packet are measured. If the data is not synchronized, the sensor gives an incorrect position. The size of the error depends on how far apart in time the various components (angles and slope distance) are measured, and the speed and direction of the moving target. LOW LATENCY FOR COMPLETE TRANSMISSION The precise position of the machine at any given time depends on the age or latency of the positioning data received. If the age of the data is recent and specific, 3

4 the onboard application software can compensate for the errors associated with the data age to output a more accurate location of the machine in real time. The latency via a direct RS232 connection is transmitted by 83ms ± 1ms and by 183ms ±1ms including the Georadio UHF modem transmission through the air. RADIO CHANNELS SETTINGS In the field, the operator can choose one of up to twelve different radio channels for the communication between the Trimble ATS Total Station and the controlling computer. The choice depends on different licenses in different countries. To eliminate interference or disturbances from other users transmitting data on the same frequency band, the operator can easily switch to another channel and operate the systems on its own channel. Figure 4: Latency Latency is a measure of how old or late the data is when it reaches the control computer. The delay is measured from the mid-point of the distance measurement when the whole data packet has been delivered. Different radio links can cause different delays. The latency depends on the data transfer rate if the modem has error correction or not. HIGH DATA OUTPUT RATE The operator and system integrator can choose an output rate from 1 to 6 Hz, which also will be transmitted in the same rate to the controlling computer. This is based on different applications and the need for more or less updated data of the synchronized angle and distance reading. PACKED BINARY DATA TRANSMISSION To ensure a low latency of the data transmission and the high update rate, the Trimble ATS Total Station sends out the data in a packed format based on binary data. This transmission method quickly delivers a large amount of data in a short time. REMOTE CONTROL FUNCTIONALITY Using the special Control & Command Software, integrators and programmers can control all Trimble ATS system functions from their third-party software application. This allows complete integration of Trimble ATS operations in the control software, and enables the user to run all settings and controls from the third-party software. DISTANCE METER CALIBRATION The distance meter is internally calibrated at regular intervals to ensure distance accuracy for the duration of operation even with a repeat of up to six measurements per second. This capability provides distance measurement with the same accuracy throughout the entire operation. The calibration starts on request from the controller and completes in less than two seconds. 3D POSITIONING ACCURACY Total 3D positioning accuracy for the system is less than 2mm at 200m. The superior accuracy is based on the high-accuracy specifications of a motorized, selftracking and prism that follows the total station with an extremely precise angle reading system, accurate in both horizontal and vertical to 1 arc second (0.3 mgon). Additionally, the distance measurement provides an accuracy of ±2mm + 14ppm. 4

5 ACTIVE 360 TRACKER TARGET The Trimble ATS Total Station features a specially designed prism called Tracker Target 360 Multi- Channel. It allows a full circle operation over the complete side and full maximum range. The Tracker Target includes a combination of the set of standard corner prism which allows distance measuring from 15m to the maximum range. The active 360 Remote Target, below the prism circle, sends a specially coded signal to the ATS Tracker unit. The ATS Tracker is located below the optical scope of the instrument. The signal is detected and tracked after the Trimble ATS Tracker automatically indicates its location. The Trimble ATS Total Station checks the availability of both parts of the Tracker Target throughout the complete operation, and only tracks the combination of both parts. Figure 5: Tracker Target TRACKER TARGET IDENTIFICATION There are an increasing number of Trimble ATS Total Stations which are currently operating on construction sites. To ensure that only the Tracker Target to the Trimble ATS total station is continually detected and monitored, the Target features a channel-setting function. You set the Trimble ATS Total Station using the controlling software and the telemetric link to the specific indication channel. This multi-channel function lets you run up to four Trimble ATS total stations and operate up to four machines with Tracker Targets in the same view of each total station without confusing signals. This is done by setting different identifications for each combination of the Tracker Target and the Trimble ATS Total Station. The Trimble ATS Total Station outputs position information at 6Hz; this makes the unit ideal for moving machines or vessels travelling at speeds up to 50 km/h. The direction of the machine s movement is not limited over the full 360 working range. TRACKER TARGET SEARCH FUNCTIONALITY AND SETTINGS Traffic on construction sites can block the direct line of sight between the Trimble ATS Total Station and the Tracker Target. As a result, continual kinemetic tracking of the Target may be lost. The Trimble ATS can search for the Tracker Target with different search routines, as well as in a user-defined search area. This capability ensures that as soon as the correct 360 prism circle and the remote circle are found in the field of view, the Trimble ATS will regain lock and will follow the Target again. An intelligent, configurable search function ensures that the Tracker Target typically will be found from 2 to 10 sec. OPERATING ON ANY CONSTRUCTION SITE The Trimble ATS system can operate and deliver data to the controlling computer at virtually every construction site even in tunnels, under bridges, or inside buildings where Global Positioning System (GPS) signals cannot work. Weather and light conditions do not affect system operation. The active target recognition allows system operation in darkness and, similar to other optical total stations, can only be influenced by atmospheric disturbances. Even under these conditions, automatic tracking is superior to any other optical system. DAILY HANDLING AND OPERATION The Trimble ATS Total Station is easy to set up and learn. The complete system features step-by-step 5

6 instructions that guide the operator through setup and provide relevant trouble-shooting information. ADVANTAGES OF USING 3D-MACHINE CONTROL IN CONSTRUCTION Today, using 3D machine control systems on construction equipment is increasingly more important. The key benefits of using these systems are based on: (1) project demands, (2) increasing cost savings and efficiency, and (3) data management and workflow. MEETING PROJECT DEMANDS There is growing complexity in modern road design and traffic route guidance. This is particularly true in larger projects such as highways, railroads, airports and sports fields, golf courses, as well as construction site preparation for commercial industrial areas and buildings. Add to this growing demands for increased accuracy and meeting time schedules. To meet these project demands, contractors are turning to 3D Machine Control Systems. INCREASING COST SAVINGS AND PRODUCTIVITY From a competitive standpoint, contractors are using 3D-Machine Control systems to expand the depth and breadth of services they offer their customers. These expanded services reduce project costs, rework and machine labor costs which, in turn, reduce cost overruns and boost productivity. Additionally, a 3D Machine Control System helps the contractor build exactly what is planned for reduced material handling, decreased material removals and, most importantly, overall material savings. Machine Control Systems combine high-quality construction equipment and the computer- based design and planning functionality. The machine operates precisely from the planned design and the machine data in real time is used to control the project status. SUMMARY The Trimble ATS Total Station is the right choice when the requested data for a moving target requires a high data output rate and positioning accuracy better than 5-10mm. Multiple types of moving construction machines, marine vessels or measuring frames for railroad control measurements can be tracked, positioned and controlled. The Trimble ATS Total Station offers all the features of a surveying instrument, plus a guidance and positioning system that lets contractors increase their accuracy and productivity on the job site. The Trimble ATS Total Station offers outstanding benefits for all fine grading applications and can be used by a grade checker in combination with Trimble s SCS900 software to check the fine grading after the machine has completed its work. This very portable solution also can be used for smaller construction sites where a daily setup is more cost effective. Overall, the Trimble ATS can operate in narrow cuttings, in tunnels and under trees and bridges where other systems may have limitations. CONTROLLING DATA MANAGEMENT AND WORKFLOW The same state-of-the-art Computer Added Design software and Digital Terrain Models used in the office offer significant advantages when used directly in 3D machine control operations. These productivityenhancing data management tools can reduce the. number of stakes in the field by up to 90% and increase project design flexibility. In addition, 3D 6