Human Oriented Control of a Concrete Spraying Robot for Tunneling Work

MEYCO Robojet sc-30 / Logica

The Robojet® is a hydraulically actuated manipulator used in the tunneling construction work. Its task consists of spraying liquid concrete on the walls of new tunnels using a jet as its tool. This heavy and large manipulator with 8 degrees of freedom has been built for ten years now and is being used worldwide. So far the manipulator has been operated manually with a simple control unit allowing to control the 8 actuators independently. with that control it is difficult to guide the jet along the wall of the tunnel while optimizing the spraying process and minimizing the losses of concrete.

In a cooperation between industry and university, we developed a novel automatic and human oriented control system for this manipulator. The new tool enables the operator to manipulate the jet in various modes, from purely manual actuation of single joints to fully automated spraying of selected tunnel areas. In one of the modes the operator can guide the jet directly in world-coordinates, using a space mouse, i.e. a 6 dof joystick. the calculation of the redundant inverse kinematics and the closed-loop control of the 8 hydraulic actuators is performed by the control system, that is based on XOberon, running on a PowerPC.

A laser scanner that is mounted near the jet is used to scan an area, selected by the operator, within the robot's workspace. This information on the tunnel profile is used subsequently to automatically control the distance between the jet and the wall and to keep the jet orientation with respect to the wall within a certain angle. The operator needs only to guide the tool center point along the directions of the tunnel wall with the space mouse.

Further automation is possible by letting the manipulator itself optimize the trajectories along the tunnel wall within the selected area. In this operation mode it is still possible, however, for the operator to intervene with the space mouse in order to correct the motion of the jet manually, for example, in dealing with obstacles, sharp corners or holes which require human experience for an optimal behaviour of the robot.

The aim of this control system is not to automate the whole task of spraying concrete on walls of tunnels, and to replace the human operator, but to simplify the task and enable the operator to use the robot as an intelligent tool and to do it in an efficient way. The operator can concentrate his attention on the part of the work he regards as essential and which he himself chooses to do, i.e., the concrete spraying task, the planning and the supervising and he can delegate the less attractive parts, the heavy and repetitive work to the machine.



Contact:

Marcel Honegger


Institute of Robotics Homepage

Jun 1998, M. Honegger

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