CONTROL 4 DOF TELE-OPERATION MANIPULATOR

Tele-operation manipulator (TM) is well-known as thebest solution for interacting between humans and the unsafe environment such as dangerous, toxic, infectious or sterile.In this study, a low cost TM system is introduced. In addition, the network control algorithms to overcome teleoperation are proposed.


INTRODUCTION
Tele-Operation Manipulator (TM) system is a remote control manipulator consists of two arms: the master and slave.Slave manipulator will be controlled to perform the same motion as master manipulator.To implement this control, master manipulator will be controlled by human.The desired motion of the master manipulator will be recognized by sensors and these values will be transmitted via LAN to the slave manipulator controller.
In 1898, Nikola Tesla made boat control model using radio in New York first to now, the TM has a history of development over a century [1].TM system as the first true master -slave is made a pure mechanical structure is benevolent R. Goertz late in 1940 at the National Laboratory Argone [2].In 1954, Goertz's team developed the first electro mechanical manipulator with feedback servo control.With the development of more modern techniques, the TM system appear in many areas more efficient service to people such as explosives detection arm of national defense and arm on the spacecraft, the main in space [3], hand-picking machine of nuclear fuel in nuclear power industry, the submersible manipulator on the seabed studies [4], and especially the type of arm surgery in remote health [5].

One of the outstanding research of robots
for medical applications such as manipulator system for remote microsurgery institute KAIST, Korea [6] and surgical manipulator system accuracy in medicine at the University of Washington , USA [7].TM control to execute as well as the ability to monitor and respond in real time, a number of studies related to model algorithms and system control are presented, such as adaptive control using a control algorithm slide is presented by Plato [11], and robust control with random time delay proposed by Prokopiou [12], etc..In this study, a low cost TM system which is attended to apply to healthcare service is presented.Regarding to healthcare service, the TM system should be respected to low costwith acceptable error and strong robustness without regard to external environments and reference inputs.For the purpose, a PID controller as well as network control algorithm are applied to control TM system with four degrees of freedom (4DOF) via LAN.Results obtained will be presented through experiment.

EXPERIMENTAL SETUP
The overview of system and schematic diagram of system are presented in figure 1 and figure 2 respectively.The PID controller output can be expressed in the time domain as: Taking the Laplace transform of (1) yields: The resulting PID controller transfer function of: A typical real-time implementation at sampling sequence k can be expressed as: From figure 12, it shows that response of system is stable.Time delay is happened due to the system response.Actually, time delay is sampling time which is set to control TM via LAN and it is 100 milliseconds.However, this is acceptable for low cost TM system which is applied to healthcare service.
In addition, from Fig. 12, with fast changes of joint angles, and performances with good tracking are also obtainedwith respect to step inputs.The errors are low and approximate of 2% of input amplitude.
In order to improvement control performance of system, triangle form and sinusoidal form are tested, and the experimental result is shown in figure 13 and figure 14 respectively.From experimental results, it is shown that the response of system with respect to PID controller is stable and good performance.Time delay is more happened with respected to sinusoidal form.It is because of the response of control system.
The system is limited with the signal inputs which have the frequency is greater than 2Hz.From the experimental results, it shows that delay of response is given, and improvement control performance of system using intelligent control such as neural network or fuzzy logic will be applied in next study.

[ 8 ]
, techniques to reduce transmission time over the network in control TM was suggested by Lee [9], Sano technical proposal in the time delay compensation control TM [10], with Towhidkhah modeling and predictive control TAÏ P CHÍ PHAÙ T TRIEÅ N KH&CN, TAÄ P 16, SOÁ K2-2013 Trang 27

Fig 1 .
Fig 1. Overview of the proposed TM system

Fig 2 .
Fig 2. Schematic diagram of system

Fig 3 .Fig 5 .Fig 6 .Fig 7 .
Fig 3. Photograph of the experimental apparatus 3. CONTROL SYSTEM 3.1.The overall of control system The overall of control system is shown in figure 4. The system will include control algorithms on the PC server, PC client, the algorithm for control circuit using PIC 18F4450 and PIC 18F4431.

Fig 9 .
Fig 9.The structure of the PID control algorithm Fig 12. Step response of PID Controller 4. EXPERIMENTAL RESULTS At first, PID controller is applied for control the motion of slave manipulator.The control parameters of PID controller are chosen through trial and error.And there are 3 10 5 . 1   x K p ,

FinallyFig 13 .Fig 15 .
Fig 13.Triangle response of PID Controller5.CONCLUSIONSIn this paper, a low cost TM system as well as network control algorithms are proposed .It is shown that the proposed control methods had a good performance for tele-operation manipulator.It can be seen from experimental results that the controller had stable and strong robustness.