May 2011

Robots go where men fear to tread

A progress report on robotic cavity surveying

By Greg Baiden, Yassiah Bissiri and Steffon Luoma

The Workbot (left) is fitted with an arm capable of raising, lowering, extending and retracting. The Combot (right) establishes wireless telecommunication links with the operation centre | Photo courtesy of Penguin Automated Systems Inc.

Here’s the situation. An unstable crown pillar has forced a mine to temporarily suspend operations, restricting access by personnel to the premises. However, it is crucial that measurements be taken from within the mine stope to ensure that it is not still moving. What do you do? When the risk is unacceptably high, you can always bring in the robots to do the job.

This was the challenge issued to Penguin Automated Systems Inc., contracted to develop a telerobotic system to help perform a cavity study beneath a potential failure zone. Their solution to the problem was to use a pair of robots designed to travel into the mine and survey the open stope cavity with a laser scanner. The robots are one metre in width, two metres in length, two metres in height and weigh 700 kilograms each.

Design considerations

One of Penguin’s first considerations was the condition of the mine ramp, which had deteriorated significantly due to the lack of maintenance over the two-year period since the shutdown. Taking this into account, they equipped each robotic platform with a six-wheeled chain drive system that was capable of flexing to ensure three-point ground contact. This system allowed the robots to manoeuver through deep ditches up to nearly a metre in depth, formed by water erosion. The platform also needed a reliable undercarriage, one with a low centre of gravity to provide robot stability.

Also required was a powerful, long-endurance drive system with low power consumption, a combination of low speed and high torque, an ability to run ancillary equipment (such as grinders, arms, laser scanners, telecommunications and networking equipment), and enough weight to counter-balance all this equipment.

Due to the long distances that needed to be traversed, a completely wireless system had to be created and installed. The wireless network had to be built telerobotically to supply 20 megabits of capacity for audio, data and video information. Both primary and supporting robots are controlled from a mobile teleoperation centre above ground, housed within a trailer and outfitted with two teleoperator workstations, a satellite uplink and an underground network link.

Each workstation consists of a main display and maintenance data display. The teleoperator interface consists of an industrial track ball and a pair of joysticks along with a keyboard. The computer bank has three computers, two of which control the robot workstations; the third is used to determine the condition of the underground network. A display is mounted between the main monitors so both teleoperators can monitor network health. The primary robot was designed to perform various tasks, including the survey, while the supporting robot was designed to ensure constant communication, with the robot performing tasks.


The communications robot, or “Combot,” establishes several wireless telecommunication links with the teleoperation centre, building a temporary network. Mounted on the Combot are a long-distance directional transmitter/receiver with up to 26 kilometres of wireless coverage and several other antennas set at different frequencies capable of establishing the network in different situations. The long-distance antenna has pitch and yaw directional motors to tune in the radio signal from the teleoperation centre.

The Combot also carries a number of portable temporary network extenders, each consisting of a battery-operated transceiver with a pair of antennas mounted in a pylon. Each extender lasts 24 hours and can increase the network capacity by an additional 500 metres.

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