Development of a Voice Controlled Surgical Robot

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The selection of the gearheads ratios was achieved ... The use of gearheads .... Congress on Medical Physics and Biomedical Engineering, Germany (2009). 4.
Development of a Voice Controlled Surgical Robot C. Vaida1 , D. Pisla1 , N. Plitea1 , B. Gherman1 , B. Gyurka1 , F. Graur2 , L. Vlad2 1 Technical

University of Cluj-Napoca, Romania, e-mail: [email protected] 2 University of Medicine and Pharmacy Cluj-Napoca, Romania, e-mail: [email protected]

Abstract. In the paper the first developed voice-controlled parallel robot PARAMIS (PARAllel robot for Minimally Invasive Surgery) in Romania, used for laparoscope camera positioning in the minimally invasive surgery, is presented. The development of the structure focused on the achievement of a simple, lightweight, cheap solution, able to work alone or as part of a multiarm robotic system. The adopted solution for the voice commands interface is presented. Some experimental results are illustrated pointing out the behavior of the robot in a surgical procedure. Key words: parallel structure, robotic surgery, open architecture, voice control.

1 Introduction The evolution of surgery, from open procedures to the chain - minimally invasive interventions - NOTES - single port surgery shows the evolution of surgical procedures towards the increase of the life quality of patients. The continuous research and achievements in the development of innovative medical equipments provide and answer the demand of surgeons for performing difficult procedures with minimal damage and discomfort for the patient. Some of the most complex tools developed for surgery are the robotic systems. Their use in surgical applications represented a challenge for many research centers which resulted in the development of several robotic systems [1], [2], [6]. Referring to endoscopic surgery, there exist several research directions which lead to different solutions aiming to increase the performances of the surgical act: the first refers to the development of laparoscope holders, the second one focuses on the development of complete robotic surgical systems while the third proposes robotic solutions acting as an assistant for the surgeon. Referring to laparoscope holders, the first achievement in this area of research was AESOP, the first robot ever to enter the surgical arena [13]. FreeHand [3] from Prosurgics is a robotic arm that positions the laparoscopic camera based on the head motions of the surgeon. Endocontrol provides ViKY, [5] a laparoscope holder with foot, hand and voice control for the camera positioning. Referring to complex robotic systems for surgery, several solutions were proposed. HERMES [2] is used

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to control all the intelligent equipments within the operating room using voice commands. The success of AESOP encouraged its developer, Computer Motion, to use the same platform for a multiarm solution, named Zeus, able to to manipulate 28 different instruments including scalpels, hooks to tie knots, scissors and dissector [2]. In the same time, Intuitive Surgical [7] launched the da Vinci robotic system, which became the first surgical robotic system which obtained clearance from the FDA to perform surgeries. The Centre for Simulation and Testing of Industrial Robots CESTER within the Technical University of Cluj-Napoca, Romania started in 2005 a joint research with the Surgical Clinic III, within the University of Medicine and Pharmacy Cluj-Napoca, Romania, aiming to develop robotic systems based on parallel architectures for surgical applications. In 2008, the first experimental model, PARAMIS, was developed [4], [8], [10], [14], [15]. The PARAMIS robot was designed to be used either as a laparoscope holder or as part of a multiarm robotic system. The control interface allows the positioning of the laparoscopic camera using either keyboard, joystick, voice or haptic commands. Regarding the use of voice control Punt presents a study [11] demonstrating some limitations of voice control, emphasizing the need for further research. PARAMIS control interface proposes a simple solution by implementing the free to use Speech SDK 6.1 from Microsoft which proved to be a valuable and reliable tool for the task. The paper is structured into 4 sections, presenting some aspects related to the design of the structure, the control system and the voice commands interface as well as experimental results and conclusions.

2 Experimental model of PARAMIS The first task of the joint research was the development of a low cost parallel robot arm used for the positioning of the laparoscopic camera in MIS procedures that would respect several characteristics: Simple, light and stiff structure; Affordable; No electrical components close to the patient; Customizable user interface; Adaptable to a multiarm solution.These characteristics would answer to some of the limitations encountered at existing systems, namely their prohibitive cost and the rigid interface. Making an analysis of the robot task, namely the positioning of the laparoscopic camera in any desired position within the operating field, a simple structure with three degrees of freedom (thus three actuated joints or three motors) can be used.The mathematical model which involves the geometric, kinematical and dynamic study of the PARAMIS robot has already been described in [8], [9], [14]. An experimental model has been developed in close cooperation with the Institute of Machine Tools and Production Technology of the Technical University Braunschweig, as presented in figure 1. The motion of the PARAMIS parallel robot is ensured by three actuators (q1, q2, q3) and several passive joints (4, 5), see figure 1, including also the virtual joint of class 2 represented by the entrance point in the surgical field. This joint, which constrains the laparoscopic camera to pass through a fixed point, is called

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Fig. 1 PARAMIS Experimental Model

”virtual” because it is not actually built in the robotic structure. The laparoscope is mounted in the passive joint (5) and connected to the image processing unit and light source (6). The laparoscope is positioned inside a human torso trainer with cholecystectomy model (7) from Simulab [12] with internal organs transmitting the images to a display (8). The first two actuators (q1 and q2) are positioned on the same fixed ball screw by means of two rotary nuts while the third actuator (q3) is fixed on the base. This construction of the PARAMIS robotic system aimed to minimize the occupied volume in the neighborhood of the patient in the perspective of its integration in a multiarm surgical system which would imply the presence in the both sides of PARAMIS, of other arms manipulating surgical instruments.

3 PARAMIS Control System and User Interface The control system of PARAMIS consists in a four phase process illustrated in figure 2. The control input allows the user to issue commands using several interfaces. The processing of these commands is achieved by the computer and sent to the PLC which generate instructions for the actuators.The control system of PARAMIS uses a CanOpen communication protocol controlled by a PLC provided by BR Automation. The use of the CanOpen protocol allows the connection of up to 127 devices to the same controller allowing the extension of PARAMIS to a multiarm robotic system using the same control system, ensuring complete compatibility, compactness and low costs.

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The control system commands the three intelligent actuators MCD EPOS 60W from Maxon which integrate in a single drive a motor, a gear head, an encoder, a PID controller and a driver. The selection of the gearheads ratios was achieved based on the displacement speeds imposed by the application, namely 1:26 for the translation joints (q1 and q2) respectively 1:156 for the rotation joint (q3). As each actuator manipulates a different mass, the possibility of individual PID controller configuration ensured an optimal behavior of each motor [14]. The use of gearheads with high ratios resolve a safety issue, namely the self-blocking of the robot during a power loss. In the same, the user can rotate with a minium effort the robot by pulling the horizontal arm, the laparoscope is than removed and the operation continued without the robot.

Fig. 2 PARAMIS Control system - Actuation scheme (top) and User interface (bottom)

The functions of the user interface, figure2, can be groups in several main categories: configuration, control interface selection, positioning, motion configuration and safety volume definition commands. The configuration commands are used for the initial setup of the robot: Nest, Origin, Save B. They are used at the beginning of the procedure to reset the encoders and to define the relative position between the patient and the robot. This setup time is about 1.5 - 2 minutes. The control interface

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commands allow the user to select any of the available command modes, enabling him to control the robot using different equipments. The positioning commands refer strictly to the positioning of the laparoscopic camera inside the patient. Two sets of commands (enabling large or small motions) allow the positioning on each direction: In, Out, Up, Down, Left and Right. The displacement increment (or the camera resolution) for a motion can be set between 1 and up to 20 millimeters. Due to the fact that the surgeon is always viewing a larger area, during the experimental runs displacements below 5 millimeters were considered too small. The interface includes also three groups of commands that enable the saving of up to three points in the surgical field and a STOP command which stops the motion of the robot in any situation or configuration. The motion configuration commands allow the configuration of the motion parameters in terms of maximum displacement in any direction, and the maximum allowable speed or acceleration. The safety volume definition commands, optional, allow the definition of a volume, inside the patient, on each direction. Once a limit is set the robot will not allow any displacement beyond it. Even when all the limits are set, using the Override Limits option the surgeon can position the laparoscopic camera outside that volume until this override is cleared. The user can select from the interface one of the five control modes available. Motor actuation enables the independent control of each actuator, useful during the configuration, testing and calibration actions. Keyboard/Mouse mode enables the control of the robot with direct interactions upon the buttons and controls of the interface. Joystick control mode enables the user to position the laparoscopic camera using the motions of the stick while the other commands having other buttons assigned on the joystick. The Haptic control mode will position the laparoscopic camera following the motion of the haptic device. This mode is used as a preliminary step in the development of an active robot arm (capable of manipulating a surgical instrument). Thus experiments can be performed with the task of developing a tactile sensor (to provide feedback for the haptic device) before the actual construction of the new robotic arm.

4 PARAMIS Voice Control Interface During the experimental runs, the surgeons preferred to control the positioning of the laparoscopic camera using voice commands, figure 3. The surgeon’s option is easily justified as it permits him to operate with both hands looking at the display and moving the camera by issuing simple commands. The learning curve spreads over a couple of minutes as the surgeon has to look only at the intraoperatory images, decide where he wants to go and express that by voice. Using voice commands to position the laparoscopic camera eliminates the need of an assistant close to the surgeon while keeping his both hands free, as presented in figure 3. The control functions for the configuration and motion of PARAMIS have been implemented in Delphi, the same set of functions being used for all command interfaces. For the voice commands, the task is to make the computer recognize the

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a) Voice commands interface

b) Experimental run

Fig. 3 PARAMIS Voice control

voice of the surgeon and call the desired function. For that a simple and free to use solution has been adopted by using the Microsoft Speech SDK 6, released in 2008. The profile of the user is trained and saved on the computer (figure 4).

a) Pseudo code algorithm

b) Voice profile setup

Fig. 4 Voice control algorithm and speech setup

After a 25 minutes training session, a recognition level of 90% is achieved while after 45 minutes a recognition level of 99% is achieved. The pseudo code for the voice commands introduction is illustrated in figure 4. Using the Speech SDK implies the initialization of the Speech functions and the use of a set of variables defined under the Speech functions. For each command an instance is initialized. When the recognition function is active, the system searches for the predefined sequences and when such a line is recognized a function is called. The use of the Speech SDK brings some important advantages: any command can be modified at any time without the need of profile retraining, the training time is short, recogni-

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tion accuracy is high and commands can even be customized for each surgeon. An important aspect when using voice commands is also the prevention of a faulty or involuntary motion of the robot due to an unwanted given command or a command given by another person. The speech profile of each person can be configured to work with very high accuracy which reduces to a minimum the risk of recognizing a command line given by another person. In addition the use of a quality microphone with noise-canceling and the integration within the command line of a ”special” trigger word (ex. PARAMIS + command) will reduce to a minimum the risk of unwanted displacements of the laparoscopic camera. Furthermore the definition of the ”safety working volume” prevents any motion that might endanger the patient during the procedure both due to a human error or an unwanted and improbable faulty interpretation of a command. The voice commands interface is closed using the ”QUIT” command which stops the voice commands interface and the control system switches to the previous interface.

5 Experimental runs and results The evaluation of the PARAMIS parallel robot has been achieved through a series of experimental procedures. The tests were made on a Torso Trainer first with a Cholecystectomy Model [12] and then on a pork liver. The aim of the tests was to evaluate the interaction surgeon - robot, the acceptance of the robot and the advantages and drawbacks reported during the procedure. During the first set of experiments the robot was positioned caudal with respect to the surgeon, while the second setup, the robot has been placed on the left side of the patient, while the surgeon was placed in the ”French position” for the cholecystectomy (figure 3). Due to the very easy to use control system the surgeons adapted in a matter of minutes to the use of PARAMIS. From the surgical point of view, for PARAMIS were reported the following advantages: PARAMIS is able to manipulate the laparoscopic tool in a large area allowing the inspection and intervention in different points of the surgical field; The voicecontrol interface allows the surgeon to focus on the procedure without any concern regarding the robot controller; The system allows the positioning of the laparoscope with large displacement or fine positioning as the procedure imposes at a certain moment in time; The adaptability of the robot is increased as it allows the positioning, with respect to the patient, in any of the four cardinal points which allows the use of multiple intraoperative positions as well as several types of interventions (abdominal or thoracic); The possibility of recording different positions allows a fast and easy return of the camera in those specific positions. From the technical and economic point of view there are several aspects that have to be pointed out regarding PARAMIS: The cost of the robot is small compared to other existing solutions (15000 Eur); The easy to customize parameters of the robot makes it a versatile tool adaptable to the specific needs of each surgeon; The possibility to transform the system in a multiarm robot controlled from the console will allow the integration of the system in a new type of surgical robot.

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6 Conclusions An experimental parallel robot for camera positioning in MIS was developed. The experimental results shown that the robot is designed to respond quickly to the surgeon voice commands and can be moved safely in the defined surgical workspace. Its design is focused on two aspects: to provide a minimum occupied space in the insertion point and to be useful in a multiarm robotic system. The open-architecture voice control solution is simple, safe and customizable and fulfils the specific needs of the surgeons. The control system allows continuous improvements of the robot functions without any physical modifications, making it versatile and adaptable to the specific needs of surgical arena. The team will continue to work on the structure optimization and start the construction of a second robot, which will be destined to manipulate a surgical instrument, working in cooperation with PARAMIS. Acknowledgements The research work reported here was financed by the PNCDI-2 P4 Grant, entitled Multidisciplinary development of surgical robots using innovative parallel structures. It has been awarded by the Ministry of Education, Research, Youth and Sports of Romania.

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