Gantry Crane Auto-Steering System

The crane control system – a key component of the port’s management system – has been developed to improve container-handling productivity and operational safety at a busy container terminal. It comprises the anti-sway system, which helps operators accurately position a crane’s spreader to grab containers; the position detection system, used to identify and cross-check the positions of stacked/unstacked containers; and the auto-steering system, which keeps the wheels of a rubber-tired gantry crane (RTGC) moving along a track either a painted line or an electrical guide wire and prevents it from hitting containers or other cranes in the tightly packed yard. For that purpose the auto-steering system must consistently identify the line mark and calculate the corresponding deviations of the RTGC’s front and rear wheels.

How does the crane auto-steering system work?

In an automated system, a programmable logic controller (PLC) is usually the central part of a process control system which comprises a group of electronic devices and equipment. With execution of a program stored in program memory, the PLC continuously monitors the status of the system through signals from input devices. Based on the logic implemented in the program, the PLC determines which actions the output devices need to execute. In an RTGC auto-steering system, the calculated deviations of the front and rear wheels are fed into the PLC so that it can adjust the speed of the left and right wheels to keep the crane on track. (Operators turn the crane’s wheels only to make ninety degree changes to its direction of movement and only when the crane is stationary at special low-friction turning pads.)

What is the problem with conventional technologies?

Several technologies for identifying the line mark – such as the induction-loop, transponders, and charge-coupled device (CCD) cameras – have been adopted for RTGC auto-steering systems. Although these technologies have been employed successfully, there is a growing concern that they may not provide the greatest possible system reliability and economic efficiency. Induction-loop and transponder systems have a limited effective range of about 10 centimeters. If a crane exceeds this range for some reason, there is no way to get it back on track easily. Furthermore, these systems require frequent maintenance. CCD systems are highly dependent on environmental factors (such as surface reflection and line mark condition) which cannot be overcome completely by the system’s hardware and software. Also, CCD systems suffer the same limited range problem as the induction-loop and transponder systems and both the CCD hardware subsystem and the line marks require continuous maintenance to guarantee the performance of the auto-steering system.

What is new in our crane auto-steering system?

An auto-steering control system which is independent of environmental factors requires a technology not based on physical line marks in the container yard. This can be accomplished by an electronic map with virtual lines and a GPS receiver to precisely locate an RTGC on the map. The control system can then compare the crane’s position as reported by the GPS receiver with the virtual lines and steer the crane accordingly. Actually, there are two GPS receivers on each crane so that the control computer on the crane can determine the crane's orientation as well as its position. GPS RTK technology provides the most efficient and reliable way to accomplish this.

Cranes in Action (Videos)

• System Overview

                      Mov format [10.9 Mb]                        Mpeg format [15.9 Mb]

• System performance

                      Mov format [8.3 Mb]                          Mpeg format [10.5 Mb]

News Articles

• The Daily Gleaner

• Times & Transcript

• The Chronicle-Herald

• Port Technology International

• Space Daily

• Canadian Centre for Marine Communication (CCMC)

• News@UNB

• UNB GGE News

References

• Kim, D. (2004). “Integration of GPS and pseudolites for improving the availability of GPS RTK-based navigation and guidance system of rubber-tired gantry cranes and ground vehicles.” Proposal report for Seoho Electrical Co., Ltd., 18 November.

• Kim, D. (2004). “Enhancement of the Seoho’s GPS RTK system for improving reliability and safety of an RTGC.” Proposal report for Seoho Electrical Co., Ltd., 5 May.

• Kim, D. and R. B. Langley (2003). “Gantry crane auto-steering: Ultrahigh-precision GPS positioning and navigation.” GIM International, Vol. 17, No. 10, October, pp. 48-51.

• Kim, D. and R. B. Langley (2003). “A dual-mode GPS real-time kinematic system for seamless ultrahigh-precision positioning and navigation.” Proceedings of ION GPS/GNSS 2003, 16th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, 9-12 September, pp. 2120-2128.

• Kim, D. and R.B. Langley (2003). “On ultrahigh-precision positioning and navigation.” Navigation: Journal of the Institute of Navigation, Vol. 50, No. 2, Summer, pp. 103-116.

• Kim, D., R. B. Langley, J. Kim and S. Kim (2003). “A gantry crane auto-steering system based on GPS RTK technology.” Proceedings of GNSS 2003, European Navigation Conference, Graz, 22-25 April.

• Kim, D. and R.B. Langley (2003). “Ultrahigh-precision GPS applications using real-time kinematic technology.” Poster presentation. EGS-AGU-EUG Joint Assembly, Nice, France, 6-11 April. Abstract published in Geophysical Research Abstracts, Vol. 5, 06331.

• Kim, D., R.B. Langley, and S. Kim (2002). “High-precision crane guidance: Shipyard giants.” GPS World, Vol. 13, No. 9, September, pp. 28-34.

• Kim, D. and R.B. Langley (2002). “On ultrahigh-precision positioning and navigation.” Proceedings of ION GPS 2002, 15th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, 24-27 September, pp. 904-913.

• Kim, D. and R. B. Langley (2002). “Development of RTK-based GPS data processing software for the gantry crane auto-steering system at Korea International Terminal’s Kwangyang port.” University of New Brunswick. Technical report for Seoho Electrical Co., Ltd., 16 August.

• Kim, D. (2002). “Ultra-high precision GPS positioning and navigation.” Viewgraphs presentation. Department of Geoinfomatic Engineering, Inha University, Incheon, Korea, 30 April.

• Kim, D. (2001). “RTK-based GPS system.” Viewgraphs presentation. Workshop on precise RTK GPS for positioning and steering gantry cranes. Korea Container Terminal Authority, Pusan, Korea, 22 November.

• Kim, J., D. Kim, S. Kim and E. Won (2001). “Precise RTK GPS for positioning and steering gantry crane. (Korean)” Kyeong-Nam University. Technical report for CIIPMS (Center for Intelligent and Integrated Port Management Systems), Dong-a University, Pusan, Korea, 28 February.

• Kim, D. (2000). “Gantry crane auto-steering system based on GPS RTK technology.” Viewgraphs presentation. GPS Research Group Meeting, University of New Brunswick, Fredericton, NB, Canada, 15 December.

• Kim, J., D. Kim, S. Kim and E. Won (2000). “Precise RTK GPS for positioning and steering gantry crane. (Korean)” Viewgraphs presentation. Workshop on Intelligent and Integrated Port Management Systems, CIIPMS, Dong-a University, Pusan, Korea, 7 December.