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Figure 1. A Transmin XXHD 100/70 rock breaker at a mine site in the Pilbara.
Figure 1. A Transmin XXHD 100/70 rock breaker at a mine site in the Pilbara.
 









Pioneering a robotic breaker system

Remote operation and automation technology is becoming more prevalent in the mining industry and there are spin-offs for the quarrying industry too. Adrian Boeing and Angie Kings-Lynne discuss the latest developments in rock breaking automation, with the award-winning Rocklogic system.

The Australian mining industry has recognised the benefits in automation and remote operation technology and is leading the world in the adoption of these technologies. A report by BAEconomics identified the main operational benefits as improved safety, efficiency and environmental outcomes with wider economic benefits to Australia overall (Brian et al, 2012). In recognition of these benefits there has been an increased uptake of autonomous and remotely operated equipment, with a major focus on mobile equipment including autonomous trucks, loaders, drills and trains. The mining industry continues to demand safe, efficient and reliable remote operation and automation technology.

It is widely recognised that the full benefits of automation will only be realised once the entire mine site processes are integrated into a cohesive system (Cordova et al, 2008; Cunningham et al, 2012). This requires significant advances in sensing and understanding the overall mine site geology and terrain (Vasudevan et al, 2010) but also requires all equipment on the site to be autonomous or remotely operated (Cordova et al, 2008).

A comprehensive study of Codelco’s Teniente mine site analysed the operation to determine how the mine could be fully automated and identified major disruptions to production. Equipment found to have the greatest impact on production were the secondary crusher, the rock breakers and load-haul-dump (LHD) vehicles. Crusher automation is typically achieved through a commercial product or via the plant’s SCADA system (Burger, 2006). Similarly, LHD vehicle automation has been a subject of research for over a decade (Roberts et al, 2000) and a number of commercial products are available (Larsson et al, 2008).

Rock breakers remain the last piece of mining equipment to make a major impact on production, and yet the uptake of rock breaker automation technology is relatively recent, with only a handful of major suppliers leading in this field.

ROCK BREAKER AUTOMATION

Rock breakers are large hydraulic machines used in hard rock mining applications to reduce oversize rocks into smaller parts that can then be processed by a crusher. A rock breaker consists of two main components: a boom assembly and a hammer. Either is mobile (eg attached to an excavator) or stationary. Stationary rock breakers are typically fixed on a pedestal above a run-of-mine (ROM) bin or a grizzly at the primary or secondary crusher. Figure 1 illustrates a pedestal rock breaker in a typical open pit mining environment.




An early project investigating rock breaker automation was undertaken by the CSIRO (Corke, Roberts and Winstanley, 1998) where a prototype hydraulic control system was constructed for testing in a laboratory environment. In addition, a 3D sensing system was developed to detect oversize material on a grizzly using a custom-built actuated laser range finder. Field tests for the 3D sensing system were completed at an underground site, and the authors proposed a set of requirements for a semi-automated rock breaker.

Corke, Roberts and Winstanley identified several key challenges to controlling rock breakers. Rock breaker booms are highly compliant with significant joint flex and high payload to self-mass ratios. This makes rock breaker control a challenging task. In addition, rock breakers are hydraulically powered, requiring different control techniques to more common and well understood electric motor-based robots. Overall, it was found that it was not feasible to automate a rock breaker at the time (Corke et al, 1998).

Over a decade later, further work in rock breaker automation was undertaken by Rio Tinto, Transmin and CSIRO to investigate remote operation (Duff et al, 2009; Cunningham et al, 2012). Duff et al investigated 3D rock sensing via stereo vision as well as a user interface for tele-operated rock breaking. A field trial connecting the West Angeles mine site to a Perth operator demonstrated that remote rock breaker operation was possible over vast distances, and that it is desirable to have an integrated interface providing full situational awareness to an operator (Duff et al, 2009).

Transmin trialled a direct remote control system for an underground rock breaker,
where it was found that remote operators had difficulties controlling the machine due to limited visibility, poor depth perception, latency and crude machine control. This trial identified a strong need for computer supervised rock breaker control and collision avoidance
technology.

Transmin had previously developed boom automation systems for waste materials handling applications. These systems included a collision avoidance system and automated movement functionality to automatically dump material into a hopper (Macdonald, 2009). Users found that automated movements overcame limited visibility and poor control issues while subsequently improving operational efficiency. In addition, automation provided uniform machine performance, regardless of the operator’s training or experience.

Overall, these studies identified that rock breaker computer control was possible, despite compliant mechanics and hydraulic control concerns. Industry demand for remote operation and subsequently collision avoidance and automated movement technology was identified.

ROCKLOGIC OVERVIEW

Rocklogic is a rock breaker automation system that provides remote operation, automatic parking and collision avoidance functionality. It is designed to increase the safety and efficiency of operations and integrate tightly to existing control and automation infrastructure on-site.
Rocklogic has a number of operational modes. A remote operator can initiate an automated movement with the press of a button to automatically park or deploy the rock breaker. Alternatively, Rocklogic can operate in a “drive-by-wire” mode where all inputs by the user are modified by the system into safe and smooth control commands to the machine. If there is a failure with the site communications network then the system can be operated from a local portable radio control console.

As shown in Figure 2, Rocklogic consists of four major components:
1.    A remote operator workstation, consisting of a remote joystick control console and a PC equipped with the rock breaker user interface, plant control software and audio/visual feedback (eg CCTV). This is typically located in a control room many kilometres away from the rock breaker.
2.    The Rocklogic panel, which contains a high performance military grade computer, a programmable safety system and plant devices. This panel is located on-site, usually in an equipment room close to the rock breaker.
3.    A rock breaker input/output (I/O) panel, located directly on the base of the rock breaker. This houses a specialised I/O controller responsible for interfacing with all instruments, sensors and actuators on the rock breaker.
4.    Rock breaker position sensors. This includes specialised in-cylinder sensors for determining the extension of the hydraulic cylinders.

A remote operator issues instructions to the Rocklogic computer from the operator console via the site’s communications backbone (eg fibre or ethernet). The Rocklogic computer then executes the higher level control algorithms and issues lower level motion commands to the I/O controller. These commands are executed using real time algorithms that control the position of the valves of the rock breaker. The I/O controller also reads the sensor signals from the rock breaker and provides feedback to the Rocklogic computer which subsequently calculates the 3D geometry of the rock breaker and updates the higher level control algorithms. The Rocklogic computer also receives information from the plant control system and fleet management systems. Finally, the Rocklogic system processes all this information and presents it to the operator. Figure 3 illustrates a typical operator workstation.


The Rocklogic collision avoidance system monitors the position and velocity of the rock breaker relative to its surroundings
at all times, and pre-emptively reduces the speed of the machine as it approaches any obstacles. The site structure is
pre-programmed into the Rocklogic system using either existing as-built 3D CAD drawings, surveyor data, or laser scan information. A custom collision detection and collision avoidance algorithm ensures no collision between the rock breaker and the structure can occur, regardless of the user’s input.

Rocklogic’s automated movement system plans safe and efficient paths to any desired location. For example, a user may select a destination above a grizzly aperture and the automated movement system will manoeuvre the rock breaker out of its park position past any obstacles to the desired goal. Alternatively, an automated movement can be initiated by the plant in response to an event. For example, as a vehicle approaches to dump, the rock breaker can automatically retract, ensuring that the vehicle achieves right of way.

Since the Rocklogic system provides remote operation and automated movement functionality, it is essential that site and legislative safety requirements are met. Typically a site will aim to isolate the machine from operators through the use of safety devices such as gates, light curtains and proximity sensors. This is accommodated through a dedicated programmable safety system which provides emergency
shutdown functionality.
 
CASE FOR REMOTE BREAKER USE

The typical (non-automated) use-case for a rock breaker is that an operator will identify oversize rocks at the crusher. The operator will then travel to the rock breaker, request that the control room stops the vehicles from dumping and starts the machine. Using local controls, the rock breaker will be manually manoeuvred from its parked position to the location of an oversize rock. The operator will then manipulate and break the oversize material, eventually completing the task and then parking the rock breaker. The operator will then notify the control room that the task is complete and permit vehicles to resume dumping.

The speed at which this task is completed is highly dependent on the skill of the operator and the communications between the rock breaker operator, the control room and vehicle operators. Often vehicles are interrupted from dumping due to rock breaking operations, and the rock breaking process takes much longer than necessary due to novice or badly trained operators.


With a rock breaker automation system, an operator has an integrated interface that provides information on the vehicle status, as well as the ability to remotely start and deploy the rock breaker. The operator will deploy the machine by selecting a destination from the user interface.

The automation system will automatically drive the rock breaker to the desired location and notifies approaching vehicles that the rock breaker is deployed. Once the rock breaker reaches its destination, the operator can begin breaking rocks. During this process the collision avoidance system ensures the machine is operated safely.

If a vehicle approaches during rock breaking, the system will automatically retract and permit the vehicle to dump, before returning to its previous location. When the operator has completed breaking the rock he can request the rock breaker to be automatically parked.

In contrast to local manual operation, the automation system removes the operator from on-site hazards, eliminates user-error (eg collisions, damaging cylinders), reduces operator variability (via automatic deploy and park), and formalises operations procedures (eg interactions between vehicles and the rock breaker). In addition, remote operation with an automation system is far more efficient as operator perception and control issues are overcome by automated movements and collision avoidance technology.

AUTOMATION BENEFITS
Rock breaker automation provides similar benefits to automation for other mining equipment, primarily increased safety, improved efficiency and reduced costs.

The key benefits include:
•    Improved working conditions for operators who can now be located in safe and comfortable control rooms. This results in reduced occupational injuries and improves staff retention.
•    Improved planning and collaboration between the rock breaker operators and other operators (eg LHD operators) that lead to significant improvements in cycle times and throughput.
•    Lower maintenance costs due to smoother operation and the elimination of collision damage to equipment. In addition, remote condition monitoring enables accurate preventative maintenance, further cutting maintenance expenses.
•    Less downtime and reduced delays to dumping, resulting in higher throughput.
•    Lower labour costs and on-costs as the rock breaking role can be shared between control room operators or multiple machines can be controlled by a single operator. Remote operation further reduces costs for remote sites by eliminating on-site accommodation and flight costs.

Rock breaker technology has seen major advancements in the last decade. As the demand for safe and efficient remote operation and automation technology increases, new systems will provide a step-change in how mine sites will operate their rock breakers. Rocklogic represents a rock breaking system that provides the key technologies required to realise the goals of future mining operations.

The major remaining challenge is to achieve fully autonomous rock breaking. To reach this goal, further work is required in reliably sensing and classifying oversize material, as well as scheduling and planning rock breaking activities. In addition, automated rock breaking poses new challenges to the design of future mine sites to support improved methods of rock breaking. •

Adrian Boeing is a senior engineer for Transmin and an adjunct at The University of Western Australia and Edith Cowan University. Angie Kings-Lynne is the control and automation manager
for Transmin.This article was first published in The AusIMM Bulletin, October 2012 and is reprinted with kind permission.

Acknowledgements
The authors acknowledge the engineers that have devoted their efforts to rock breaker automation: Doug Adam, Daniel Adams, Greg Haydon, John Heard, Dirk Horn, Michael Kradolfer and Tane Pendragon.
References
Burger DJ. Integration of the mining plan in a mining automation system using state of-the-art technology at De Beers Finsch Mine. The Journal of The Southern
African Institute of Mining and Metallurgy 106; 2006.
Cordova, FM, Canete L, Quezada LE, Yanine F. An intelligent supervising system for the operation of an underground mine. International Journal of Computers, Communications and Control 3(3); 2008: 259-269.
Corke PI, Roberts JM, Winstanley GJ. Robotics for the mining industry. In: Autonomous Robotic Systems; 1998: 163-181. ISBN: 978-1-85233-036-1.
Cunningham J, Fraser SJ, Gipps ID, Widzyk-Capehart E, Ralston J, Duff E. Development and future directions in
mine-site automation. AusIMM Bulletin No 2, April 2012: 40-45.
Duff E, Caris C, Bonchis A, Taylor K, Gunn C, Adcock M. The development of a telerobotic rock breaker. In: Proceedings 7th International Conference on Field and Service Robotics; 2009: 411-420.
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