Open Cut » Maintenance & Equipment
The project's objective was to develop a tele-operated manipulator prototype, in order to separate workers from the hazards of heavy maintenance, in particular, dragline jewellery maintenance. Dragline jewellery maintenance presents a high level of HSEC risk to maintenance personnel. By physically separating workers from the actual work during many of these tasks, the consequences of uncontrolled energy release can be reduced. This will result in the a reduction of overall risk.
The manipulator's physical design concept is that of a multi-axis device capable of a wide span of reachable positions and orientations. This supports the requirement for a field device that does not require a long setup time. This mechanical framework was supported by an equally broad software framework based on Robot Operating System (ROS) software libraries. In addition, due to the complexity of the device, effort focused on producing an operator interface that would simplify and make safe the operation of a potentially hazardous machine. Significant time was spent developing simulation in order to understand the core task requirements and to assist in the development of the control code for the machine.
Two main dragline jewellery maintenance tasks were targeted: rotation of hoist chains, and insertion of a pin into a clevis. Simulations were developed of the tasks and of the manipulator. The simulations modelled forces, collisions and actuator dynamics. These simulations were also the environments by which the operator interfaces would be tested. Three main interfaces were tested on coal mine workers. The definitive preference was for a joystick-based interface that controlled the manipulator tool in task-space coordinates. Successful achievement of the tasks in simulation, demonstrated the validity of the design decisions.
The successful interface allows an operator to specify a particular movement directions and causes the software to determine the required movements within the joints to achieve that direction goal. The software algorithms reduced the considerable mental effort that would otherwise have been required to correctly produce that transformation. The operator is then freed to concentrate on the task at hand and in maintaining a safe work environment. The successful development of an intuitive interface annulled one of the key project risks: that a manipulator would be developed without an interface with which to operate it safely.
A physical manipulator prototype was constructed so that field testing of the desired tasks could be undertaken. The development was challenged by the demanding specification. Particularly in the physical arrangement of of all the components to fit the size, strength and range of movement requirements. The key specification for the manipulator was a 250kg lift at a reach of 2.4m. The manipulator partially met its specifications, with some mechanical and control aspects requiring further attention. Nevertheless the manipulator was sufficiently rugged to support itself throughout its range of movement and is positioned to support further development.
This project developed the concept of a tele-operated heavy manipulator for maintenance tasks to a proof-of-concept prototype. Whilst the current level of capability is far from commercial, the project achieved some key capability milestones. The first being the development of an intuitive interface, which allows non-expert operators to effectively control the device. The second milestone is a full scale manipulator that partially achieved its design goals. This prototype is suitable for the continued development of technologies that support the manipulator concept.