<TITLE: Impedance Control of a Water Hydraulic Manipulator for Teleoperation Applications
ACADEMIC DOMAIN: technology
DISCIPLINE: automation engineering
EVENT TYPE: doctoral defence presentation
FILE ID: UDEFP100
NOTES: continued in UDEFD100

RECORDING DURATION: 12 min 49 sec

RECORDING DATE: 23.6.2004

NUMBER OF PARTICIPANTS: unknown

NUMBER OF SPEAKERS: 1

S1: NATIVE-SPEAKER STATUS: Spanish, Catalan; ACADEMIC ROLE: research student; GENDER: male; AGE: 24-30>


<S1> well teleoperation is a technique that allows tasks to be performed remotely , tasks are performed remotely because it would be too dangerous for a person to carry out the task directly , with er teleoperation the operator and the task are separated by a safe distance , the structure of a general teleoperation system includes a local site where the operator is located and a remote site where the telemanipulator is placed and the tasks are performed , the interaction between the telemanipulator and the operator takes place with er control station , the control station transforms the operator's orders into a form appropriate for transmission and telemanipulator use , also the control station provides the state of the task to the operator er using er visual displays or force displays <P:05> i will er describe the evolution of er teleoperation with respect to the design and implementation of the interfaces between the task the telemanipulator the control station and the operator , i will er focus on er how impedance control can be used to manage the interaction between the telemanipulator and the task , i will present the main properties of a water hydraulic telemanipulator and er it will be described how , model based teleoperation can be used to handle the user interface between the operator and the control station . well teleoperation is an ancient technique , er for example blacksmith tongs er were used er by the operators to extent their reach and er to be able to handle hot objects without the risk of burning , already with this ancient teleoperation system we can find the same er parts as in the general teleoperation system we can find an operator we can have a control station represented by the handle of the , represented by the handle of the mhm <PUTTING UP A SLIDE> . of the tong and er we have a manipulator represented by the gripper which is er holding the (work) piece , this er blacksmith tong er allow the operator to feel forces and to er transfer motion from the hands to the gripper using the er tongs rod . er more modern version of a blacksmith's tong can be found in remote handling tongs which er are used for example in er nuclear laboratories to handle radioactive objects <P:07> modern teleoperation starts with the design and development of mechanical master slave manipulators in the late 40s , nuclear research created the need to develop a technique to handle dangerous materials in a precise way , and the problems of protecting the workers and at the same time er being able to manipulate dangerous materials precisely were not being met but er but er were tongs that er became longer and longer it was not possible to control those materials with this kind of tongs so telemanipulation became a critical need <P:06> the connection between the master and the the slave is carried out the through a mechanical transmission with mechanical master slave manipulators mechanical transmission consist of wires belts rods chains et cetera , this mechanical transmission allowed er forces and motions transferred from the operator to the telemanipulator and vice versa also forces and motions were transmitted from the slave to the master this kind of er property is er called bilateral control , and here i can find another example of a master slave manipulator , however with er mechanical manipulators there was still a limitation of distance between the master and the slave because of the mechanical transmission therefore in the mid-50s electrical telemanipulators were developed , with er electrical manipulators the mechanical transmission between the master and the slave was cut and was replaced by electrical transmission lines thus the distance between master and slave was increased , also the master and the slave arm were equipped with actuators and sensors therefore operator's orders captured by the sensors in the master arm was er transmitted through the electrical transmission lines to the actuators in the slave site , as well the state of the task captured by the sensors in the slave manipulator was transmitted through the same electrical transmission lines to the actuators in the master arm which allowed the operator to feel feedback , this way electrical telemanipulators became also servo- er became bilateral meaning that er forces and motions were transmitted from master to the salve and vice versa , this is an example of a electrical er master manipulator where the connection between the master is carried out , is carried out er only with er electrical transmission lines , in order to carry out the operator's orders the slave manipulator needs to be equipped with a control system able to handle control signals for the actuators and from the sensors , the task that the telemanipulator has to perform is to interact with er unknown environments and er several control architectures can be used for example position control force control hybrid position force control and impedance control , impedance control regulates the relation between force and position rather than er forces and position individually the impedance is noted with the letter Z , for example here in the schematic representation of a hydraulic cylinder with a mass the force applied by a hydraulic cylinder will cause the mass to move in such a way as er commanded by the impedance of the system , and usually in impedance control is desired that the , that the impedance of the system corresponds to some desired behaviour for example a second order system with er inertial dumping and stiffness terms , so the mechanical system to be controlled is er trying to emulate the behaviour of an ideal system , also reference position reference force and reference position can be added to the desired impedance , as well at the same time that er electrical manipulators were developed also hydraulic- oil hydraulic manipulators were constructed oil hydraulics er allowed the use of er higher loads than electrical manipulators but they're still having a compact size , however er using oil as the pressure medium can cause some difficulties in some environments where the risk of external leakage cannot be tolerated or there is the risk of er flammability is not accepted , also this is there is the problem of er disposal of used oil in case that the the manipulator has been in a radioactive environment , some of the problems of oil hydraulics can be solved with water hydraulics which provides a non-contaminant and fire-proof fluid while still keeping the good properties of hydraulics in general such as er high loads and er relative er small-size actuators . the design of the control station as shown in this example consist of er master arm and er several monitors which er display live video from the remote site , however however the use of er , of a live video images er requires requires a careful planning the location of the cameras cannot be always the right one , complex systems such as pan-tilt platforms are difficult to install and er the s- the field of the view of the cameras might be obstructed also they need er high transmission bandwidth they need er dedicated transmission lines and some image processing on both sites in the remote site and in the local site can cause some time delay , some of these problems can be solved er using model-based teleoperation , in model-based teleoperation there is a model of the manipulator and the remote environment and this model is used in the control station to visualise the state of the task , the manipu- the operator gets er the model updated with er with er manipulator data <P:06> some of the features that are not possible with video cameras are possible with er virtual reality for example the operator can choose any point of view can zoom in the critical zones or also er items can be highlighted or collisions can be prevented by measuring distance between objects in the remote environment , however not er everything can be modelled and not everything can be can be known in advance so the best approach is to have a combination of model-based teleoperation with er live video cameras this allows for example to reduce the number of cameras since some of the cameras camera views can be substituted by virtual views and er the use of er complex pan-tilt platforms for the cameras can be substituted by moving virtual camera . i would like to conclude this presentation by summarising the main issues in the evolution of teleoperation and also to give an outlook in for the development of teleoperation , initially teleoperation was used for handling er tasks that were carried out in dangerous locations , however it is my belief that er the in the future teleoperation will be oriented also to tasks that o- occur not in dangerous environments but in uncomfortable environments such as er high temperature places or low temperature places in these cases the performance of the operator will decrease because he or she doesn't feel comfortable however if teleoperation is used the same performance as hands-on teleoperation could be acquired , and there has been an increase in er in the presence of er computer systems in the evolution of teleoperation from the early days from mechanical master slave manipulators to nowadays where virtual reality is used in some applications , computer systems will increase their role in assisting and (accompanying) the operator they will become more intelligent and they will allow the operator to give er long term plans and higher level orders , thank you </S1>
