on-board virtual instrument to ethernet control of an...

ON-BOARD VIRTUAL INSTRUMENT TO ETHERNET CONTROL OF AN UNDERGROUND DRILLING MACHINE FOR DRAINAGE PIPING LAY-DOWN

REV 2007 - www.rev-conference.org

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On-board virtual instrument to Ethernet control of an underground drilling machine for drainage

piping lay-down V. Belotti, R.C. Michelini

PMARlab – Laboratory of Design and Measurement for Automation and Robotics. DIMEC – Department of Mechanics and Machines Design

University of Genova Via all’Opera Pia 15 A - 16145 Genoa, Italy

Abstract— Nowadays, the constant and regular evolution of electronics and computer technologies make their products competitive and attractive in different industrial applications; despite that there are industrial fields of application having the electromechanical components as leading supplier.

The European Council has knowledge of the fact that pollution control and landfill remediation are urgent incumbents and in Directive 97/C_76/01 requests the members to make secure their landfill from possible leakages or environment contaminations. Robot technology with remote intelligence and distributed measurement are effective means to supply safe and worthy solutions; but the drilling equipment industries are diffident to change their technologies.

With the present research, initially financed by European Community, we realize a compact drilling robot, develop the instrumental architecture for the measurement and actuation equipment and to elaborate the suited remote sensing and control environment, based on an innovative client-server lay-out. The resulting drilling robot prototype was successfully tested both at the workshop and on site.

Index Terms—distributed measurement, drilling robot, remote sensing, virtual instrument

I. INTRODUCTION The European Council, in the Directive 97/C_76/01,

[1] requests the member states to take the necessary measures to ensure, to fullest practicable extent, in order to make those old-landfills and polluting-sites should be rehabilitated. This request is specifically addressed, with the Microdrainage project, EVK4-CT-2002-30012, successfully achieved [2-8], building the robotic prototype here recalled, properly operative from mid 2005.

The present project overcomes the limitations of current solutions for landfill remediation with resort to a mixed technique, mainly based on a robotic equipment, capable of creating a draining manifold through remotely operated fixtures.

The technique combines microtunnelling technology, to create proper collecting lines under the landfill, with implantation in the waste bulk of the patented draining elements, to obtain a cost effective system for safe and final remediation of landfills. The draining pipes consist of hollow rods with draining slots covered by water soluble plastic caps, to prevent occlusion by the debris during drilling.

The landfill drilling operations and the successive draining tasks take place in extremely dangerous working condition. Due to this, the human presence in the tunnel is not allowed and the drilling robot has to be completely controlled and monitored from the outside of the tunnel. The first step of the project was the mechanical design of the first highly compact drilling robot. Due to compactness, this project used innovative technical solution for its components design, some of which are patent pending. The set-up, design and implementation, of the remote control of the drilling robot started with the definition of the all operation procedures (each composed of several elementary actions); thereafter, for each procedure, the normal working condition and the emergency state were identified and detailed.

In the design phase of the project, the main discussion between partners was about the reliability of remotely operated controls and sensors. Indeed in the drilling equipment field the reliability is an essential requirement for every component. At last the innovative and the conservative parts reached a compromise that led to the realization of a truly innovative product.

The paper starts with the overview of the mechanical project of the drilling robot, and then it carries out some aspect about the measuring and controlling system architecture. Later the remote on-board controlling virtual instrument is presented with its three operation levels: automatic, for the normal working condition; manual, for drilling task or for overcoming some unexpected difficulties; and emergency-self-management, for halting and keeping in safe the machine in case of critical situations.



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II. MECHANICAL DESIGN The project work-site, Fig. 1, assumes the realization

of a microtunnel (patented technology) below the landfill at safely distance. The designed drilling robot will travel along the 1.6 m diameter microtunnel of concrete-wall with the following duties [2]:

• to reach the assigned location on the path, performing proper levelling and attitude trimming;

• to rotate the mast at the prescribed slope, operating the concrete wall boring with the special tool;

• to accomplish the drilling duty, on-progress leaving the special-purpose draining rods, as planned;

• to fulfil the draining train insertion, properly pushing the last rod up to the tunnel inner surface.

The drilling robot distinguishes into two main units: • the tracked vehicle with the power units and the

oil tank, carrying the operation effectors and the fixtures buffer;

• the multi-purpose operation unit, with vices and actuation contrivances, with the fixture buffer and related manipulation device for loading/unloading duties;

For the first unit, a set of off-the-shelf components are addressed, properly adapted to grant the location of the other unit, during the translation along the microtunnel. The research focuses on the multipurpose operation unit, Fig. 2, which requires task-driven innovation. This unit is fixed on a frame able to rotate of 90 degrees from the azimuth in both directions; this gives the robot the working capability of three degrees-of-freedom.

The drilling unit is provided by a radial mobility, hydraulically actuated through a multiple-chain transmission. In order to fulfil both the concrete boring task, with high speed and low torque; and the landfill drilling task, with low speed and high torque; the drilling head was designed with a two speed gear box.

The realized drilling unit has the following features: 1 m of radial stroke; 60 kN @ 70 rpm in low speed gear, and up to 600 rpm in high speed.

The buffer is able to store the rods needed to complete a 20 m draining pipe; moreover it is designed to make possible the quick rod-refill after the drilling task.

Finally the multi-purpose operation unit operating was provided of a two degrees-of-freedom arm able to pickup the rods from the buffer and to load them on the drilling unit mast. For some special rods, the boring one and the levelling one, and for unforeseeable events the arm is also capable to make the opposite operation, i.e. from the drilling unit back to the buffer magazine.

Figure 1. Remediation methodology of a landfill by micro-tunneling



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Figure 2. The drilling robot with multipurpose unit details.

III. THE ONBOARD CONTROLLER

A. Overview The powerfulness of virtual instrument and distributed

measurement permits to achieve the key aspects of the present research are:

• the reliability, for the above mentioned facts; • the autonomic management of emergency, due to

the operator absence and the working site inaccessibility;

• the human perception, due to the fact that the operator has only a monitor to control the remote machine, and he hasn’t any physical feedback from it.

The drilling robot was instrumented with a total of 32 sensors and 52 actuators; only a remote intelligence with an on-board processing could manage efficiently this great number of input and output signals.

According to the distributed measurement principles we developed a virtual instrument on remote intelligence able to

• acquire and process the sensor’ signals, • elaborate data and output the operating actuator’

signals, • communicate to the remote operator the processed

telemetry and interact with him for commands.

The virtual instrument architecture is a state machine with two main parallel threads: the first is the acquiring-processing-actuating task, which has the highest priority; the latter is the communicating task, with lower priority [7].

Several environmental, mechanical and hydraulic quantities are measured and these data are used by the control system. The most significant ones are reported to the operator. Two onboard cameras, showing the working scene, provide valuable help to supervise the positioning of the robot in the tunnel, the development of the drilling operations and the functioning of the rod manipulator. The feedback working parameters and the camera images will increase the working perception of the operator [8,9].

B. Communication architecture The communication architecture between the Human

Machine Interface, HMI, of the remote operator and the robot onboard intelligence is designed with the following objectives:

• to minimize the data overflow and time lag; • to cover a distance up to 500 m; • to have an open source protocol.

The first aim was reached using a client-server architecture with a hierarchy of transmitted data. The onboard instrumentation has a 188 MHz real-time processor with 64 MB of SDRAM; on it we implemented



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two main components: a server and a primary pc. The server tasks are transmission of telemetry to the HMI, transmission of video data to HMI from the two on-board cameras, the HMI messages reception and delivery according their hierarchy. The primary pc takes care of sensors acquisition, data processing, actuators control, emergencies management, telemetry formatting, remote operator messages interpretation and execution.

We distributed the communication tasks on the server and the working tasks on the primary pc: we will preserve the effectiveness and the reliability of the robot also in case of communication data overflow. If this critical condition happens, the robot will autonomously complete the executing operation and will wait for the normal communication re-establishment.

We implemented a two level of message hierarchy: emergency message, the highest priority one, and command message, the normal priority one. If, while a batch queue of command is waiting to be executed, an emergency message arrives on the server, this will be immediately sent and to the primary pc to be processed.

In this way the operator could act and emergency stop of the machine with the highest possible speed.

A long transmission distance was achieved using a 100 Mbit/s Ethernet communication on optical fiber: it permits a connection over a distance up to 550 m; we adopt an extremely robust fiber optic: it withstand to 50 tons of accidental pressure.

The adopted transmission protocol is an ASCII based telemetry string, with alpha-numeric values semicolon separated; this open source data coding allows the licence-free development of operator interface.

C. Command architecture The primary pc has the core duty: operate the drilling

robot; this implies acquiring the signals from sensors to check the actual machine state and, on the basis of this, controlling the actuator to execute the operator command.

We designed a three-level command architecture: • the zero-level commands are completely manual

and the operator uses them only in case of failure of other higher level commands; for safety purposes these command are not directly accessible by the operator

• the one-level commands are automatic one, the operator set only the start and awaits for their conclusion; these commands are freely accessible by the operator, but not used in normal operating conditions;

• the two-level commands are the macro sequences, these are one-level commands organized together in a predetermined succession to execute a machine task, e.g. “load the boring tool”; the machine is normally operated using this high level commands.

The only exception from the above explained architecture is the drilling command: this command has

to be a manual command, because the pressure and the thrust are continuously varied by the operator, a specialised worker in drilling task, on the basis both of the hole waste composition (visible with the on-board cameras) and of the rotation and advance speed measurement. So this is a zero-level command, i.e. completely manual, and it is directly accessible to the operator.

Moreover the two-level commands could be nested as deeper as wanted, so the operator creates elementary macros and then uses these to create more complex macros and so on.

The machine tasks are organized in nine main duty cycles:

1) the robot moves longitudinally along the microtunnel, to reach the planned location;

2) the robot rotate the frame, to orient the drilling unit along the required radial direction;

3) the robot levels itself and firmly fasts to the tunnel wall, in order to accomplish the planned drilling;

4) the boring tool is handled, the robot perforates the microtunnel reinforced-concrete wall and the tool is returned in the buffer;

5) the first rod with a drilling head is loaded, and the lay-down of the drain piping is started;

6) the rod series are loaded, and the landfill drilling carried on, leaving out the rods (this is a repetitive task up to all 26 rods are used for a total length of 20 m);

7) the last rod is loaded, and the drain piping is fulfilled, with proper bottom sealing;

8) the levelling rod is handled, and the drain piping is pushed, to not jut out of the wall;

9) the robot keeps the standby position, and the buffer refilling is accomplished.

An explanatory example of duty cycle flow chart is shown in Fig.3.

Figure 3. Drilling machine duty cycles



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D. Emergency architecture The on-board intelligence module, supervising the

normal and the emergency cycles, surmounts the risk coming from a black-out (temporary or lagged) in the communication between the robot and the remote control station, which would make the operator blind and unable to command the system, in a straight line. Moreover, this intelligence module filters the information sent back to the operator, to avoid the overload of the communication band.

Also the emergencies are organised in a two-level hierarchy architecture: the alarm level and the emergency level. In the first group we find the illegal robot movements, the feasible dangerous situations, the temporary connection falls down and temporary electrical black-outs. In the second group there are the connections definitive interruptions, the electrical black-outs, and the unpredictable events.

The connection interruptions and electrical black-out are considered temporary if they are shorter then 30 minutes, otherwise they are considered definitive.

The on-board intelligence normally manages the alarms with two operations: firstly stop the currently executing robot action, and then send a message to the operator advising him of the occurring alarm.

On the contrary, in the emergency situation the adopted solution depends on the duty cycle which the robot is at: if the robot is in the duty cycles 1, 2 or 9, it will stop and await for human assistance; if the robot is in duty cycle 3, first it will autonomously retract the holding jacks, then it stops and await for human assistance; finally if the robot is in the duty cycle from 4 to 8, autonomously it will cut the on-progress piping line, then it will retract the holding jacks, finally it will stop and await for human assistance.

Fig.4 shows both the flow charts of emergency and alarm management by the on-board intelligence.

Figure 4. Emergency/alarm flow chart



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IV. ROBOT TESTING

A. Overview The overall robot assembly was completed and settled

up in the workshop; the final test took place with two test campaign, with real boring and drilling operations, took place on-site.

Main problems, encountered during the workshop tests, concern the arm and buffer alignment during the rod picking and unpicking operations, and the drilling head position: the overall working machine functionality is very sensible to both movements.

B. Rod picking/unpicking fine-tuning The rod picking and unpicking operation needs three

fine-tuned movements: i. the arm rotates of an angle of 25° and get the

alignment with the radial direction of the buffer; ii. the buffer rotates of predetermined angle in order to

have the selected rod is in front of the arm grasps; iii. the arm rotates again of an angle of 45° and gets the

alignment with the drilling head mast. The involved components in the picking operation are

on the multipurpose unit, this implies that inclination respect to the azimuth, i.e. the gravity force, varies from 0 to 90 degrees depending on the selected drilling radial position; hence the load and consequently the effort of actuators is variable. It should also be noticed that an arm-buffer or arm-mast misalignment greater than 2 mm will fail the picking operation.

The performed tests evidenced the possibility that movements are not perfectly reproducible. Considering that a single draining pipe implies 33 picking and 2 unpicking operations, we decide to add proximity sensors and limit switches on mast and arm movements. Moreover we implement a redundant check based both on hydraulic oil pressure behaviour and sensors.

The adopted solution increases the correct movement reproducibility and, on the other hand, it grants an effectiveness alarm system to individuate the erroneous movement conclusion.

C. Drilling head position The drilling head has an overall stroke of 1.15 m: its

positioning along this stroke should be accurate, because there are 12 special positions to be reached during the screwing, unscrewing, loading, unloading and drilling operations.

Due to overall dimension limitations, we adopted an incremental angular encoder on the transmission chain to measure the head position with high accuracy.

The encountered problem was caused by the vibration, during the drilling operations, the electrical noise and the shocks, due to the unscrewing operations. All these factors deteriorate the measurement of encoder pulses up

to go down maximum allowed error of 5 mm, in the worst cases.

The problem has been successfully solved adding a limit switch on the stroke, changing the electronic counter module, implementing a redundant control on measurement based on hydraulic oil pressure behaviour and limit switch. The maximum expected error has been reduced to 2 mm.

V. CONCLUSION The first tests started in October 2005, when the first

complete realization and assembly of multipurpose unit was ready; the two final tests with the complete robot installation in working site took place in July and August 2006.

The research carried out an on-board intelligence able to manage all the machine measurements, all the machine actuators and all the emergencies in a reliable and autonomous way.

By this project, the successful deployment of these enabling technologies helps in developing the novel robotic device, capable to solve the de-pollution requirements of the EU environmental policy.

The prototype first tests gave results so newsworthy that it became the high tech staple of the EU partner industries.

ACKNOWLEDGMENT The project is developed with the co-financing of EU

Contract EVK4-CT-2002-30012. The fruitful contributions of the project partners are gratefully acknowledged.

REFERENCES [1] Council Resolution of 24 February 1997 on a Community strategy

for waste management (97/C 76/01) (celex 31997Y0311(01)). Official Journal C 076 , 11/03/1997 P. 0001 – 0004 http://eur-lex.europa.eu

[2] R.C. Michelini, R.P. Razzoli: “Progetto a ciclo di vita e fascicolo tecnico della costruzione”, Congr. AIAS, Milano, Sett. 14-17, 2005, pp.1-10.

[3] A.Barbieri, R.C.Michelini, M.Zoppi: “An underground robotic equipment for leachate draining and landfills remediation” 35th Intl. Symposium on Robotics, ISR 2004, Paris, March 23-26, 2004, p. 101 (5) 14-5.

[4] R.C.Michelini, M.Zoppi: “Under-actuated hands for rods balanced handling”, Intl. Conf. IMG-04, Intelligent Manipulation & Grasping, Genova, July 1-2, 2004, pp. 312-317, ISBN 88 900 426-1-3.

[5] R.C.Michelini, M.Zoppi: “Progetto di robot per tele-operazioni in ambienti ostili”, Convegno Naz. ADMAIAS: Innovazione nella progettazione industriale, Bari, 31 ago.- 2 sett. 2004, pp. 357-69, ISBN 88-900637-2-6.

[6] R.C.Michelini, R.P.Razzoli: “Product-service for environmental safeguard: a metric to sustainability”, Intl. J. Resources, Conservation and Recycling, vol. 42, n° 1, Aug. 2004, pp. 83-98, ISSN: 0921-3449.

[7] Vittorio Belotti, Francesco Crenna, Rinaldo C. Michelini and Giovanni B. Rossi, “A client–server architecture for the remote sensing and control of a drilling robot”, Measurement, Volume 40, Issue 2, February 2007, Pages 109-122,



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[8] V. Belotti, R.C. Michelini, M. Zoppi, “Remote control and monitoring of an underground robotic drilling equipment for landfill remediation”, 22nd International Symposium On Automation And Robotics In Construction (ISARC 2005) September 11-14, 2005; Ferrara, Italy.

[9] V. Belotti, R.C. Michelini, M. Zoppi, “Remote controlled underground robot for landfill drainage”, in: 8th Biennial ASME Conference on Engineering Systems Design and Analysis (ESDA 2006), July 4–7, 2006, Torino, Italy.

AUTHORS V. Belotti is with the PMARlab of Dept. of Mechanics

and Machines Design, University of Genova - Via all’Opera Pia 15 A - 16145 Genoa, Italy. ([email protected])

R.C. Michelini is with the PMARlab of Dept. of Mechanics and Machines Design, University of Genova - Via all’Opera Pia 15 A - 16145 Genoa, Italy. ([email protected])

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