BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de Universitatea Tehnică Gheorghe Asachi din Iaşi Tomul LIV (LVIII), Fasc. 3-4, 2008 Secţia AUTOMATICĂ şi CALCULATOARE VIRTUAL INSTRUMENTATION IN THE DRIVE SUBSYSTEM MONITORING OF A MOBIL ROBOT WITH GESTURE COMMANDS BY CRISTEA PAL, *MIHAI HORIA ZAHARIA, IOSIF OLAH, **ŞTEFAN GHEORGHE PENTIUC, NICOLETA ŞTEFANIA HULEA and FLORIN TIBERIU PAL Abstract. In this paper the use of virtual instrumentation system for academic research and educational purposes is presented. Nowadays Human Computer Interaction (HCI) at the communication level can be used to interact with complex robot systems. A dictionary was created in order to naturally interact with a complex cyberspace system using gestures. The experiments were conducted using a prototype of a mobile robot equipped with a complex computing system. The main functional parameters of the electrical drive subsystem are monitored using virtual instrumentation in order to obtain, by further analysis, an optimal control and high safety. Key words: robot, gesture commands, virtual instrumentation. 2000 Mathematics Subject Classification: 68U07. 1. Introduction In this paper an implementation of Virtual Instruments (VI) for educational purpose and research is presented. This approach is flexible and easy reconfigurable in the drive subsystem monitoring of a mobile robot with gesture commands in real operation conditions. For the drive motors the command optimization, electrical and thermal overload protection is required. The solution was to develop a VI based on LabVIEW and NI USB- 6009 module for monitoring the drive subsystems parameters in the real operation conditions. In order to proper design the control interface of the drive subsystem some real time parameters must be monitored. These parameters must be further off-line analyzed too. A typical interaction for human computer interaction based systems is
10 Cristea Pal et al. related to human gestures as primary source of information. This approach represents a natural and efficient interaction from human operator point of view. The primary design concerning the use of gestures in robotic control was further extended to fulfill the requirements of complex menu and interactions needed to be used in augmented reality [1]. 2. Human Operator Hand Gesture and Posture Design By analyzing the requirements for static or mobile robotic systems into well defined framework a hand based gesture dictionary were proposed. The gesture selection was made by taking into account the specific knowledge model of average educated operators that are usually used to interact with the system. Another selection criterion is to select the gestures that minimize the computing effort need in pattern recognition process. In Fig. 1 and Fig. 2 two gestures from dictionary are presented. Fig. 1 Vertically rise of robot arm. Fig. 2 Rotate anticlockwise robot arm. The dictionary design takes respect the following constraints: quick real time recognition of gesture and posture, reducing misunderstanding risks and user satisfaction. 3. The Mobil Robot with Gesture Commands The mobile robot was designed using differential active wheels with independent control systems driven by DC current. The design of the mobile platform for the robot is presented in Fig. 3. In Fig. 4 the implementation of the robotic system is presented. The trajectory of the robot is obtained by using his spatial coordinates and his direction vector [2], [7]. The trajectory control is given by the control of the speed and rotation direction for each wheel. In Fig. 5 the theoretical schema of
Bul. Inst. Polit. Iaşi, t. LIV (LVIII), f. 3-4, 2008 11 robot movement control schema is presented. Fig. 3 Mobile platform robot design. Fig. 4 The mobile robot with Gesture Commands. The electrical driven motors use 12V DC and a permanent magnet. The supervised parameters are the current, temperature and revolution of the motors. To do that current transducer 7KG 6131 1, temperature transducer AT-2F16 and revolution transducer VE Tachometer were used [5], [6]. Fig. 5 Control system block schema. 4. The Developed Virtual Instruments For the educational and research scope two virtual instruments were developed. The Virtual Instrumentation is used to acquire with a certain frequency the values of the physical parameters from the drive subsystem of the mobile robot with gesture commands. The monitored parameters are: motor
12 Cristea Pal et al. stator temperature, the current and servomotor speed. The monitoring of these parameters is made in various working stages of the robot and gives us the possibility of real-time analysis of drive subsystem functionality. As result proper commands can be designed for the subsystem. Also some thresholds are set to protect the system when the working limit conditions are reached. When the temperature threshold is reached the whole subsystem is halted immediately. When the current threshold is reached a temporized stop command is issued. This variable temporization is used to avoid system halt due to short current peaks [3], [4]. The designed and developed Virtual Instruments that solves the above mentioned problems has two components: the Front Panel and the Bloc Diagram. In the first approach the real time representation of the three supervised parameters onto one graphic were elected. Here the scales for each parameter were elected in accordance with his meaning as can be seen in Fig. 6 where a normal working situation is presented. Fig. 6 The VI with one graph. On the main panel of the Fig. 6 we can see a Waveform Chart with the real time variation of the monitored parameters, the data table that contains all measured data for further off line analysis. Also here we have the required controls for setting the sampling period, and LED indicators for reaching the temperature and current thresholds. The block diagram of the LabVIEW program for the Main Panel with one graph is presented in Fig. 7. By the use of some LabVIEW modules from Function Pallet in the design using While Loop a simple, flexible and easy reconfigurable program is obtained.
Bul. Inst. Polit. Iaşi, t. LIV (LVIII), f. 3-4, 2008 13 Fig. 7 The Block Diagram of VI with one graph. To present at the laboratory hours the LabVIEW flexibility and the capacity of being easy reconfigurable a second version for the same virtual instrument was developed. This is presented in Fig. 8 and is most efficient for research needs due to his increased clarity. Fig. 8 VI with three graphs. Here three distinct Waveform Charts one for each monitoring parameter are placed. As result the visual analyze is improved. The LED for signaling
14 Cristea Pal et al. parameter thresholds are embedded into the corresponding charts. The thresholds are set directly from block diagram from Fig. 9. Fig. 9 The Block Diagram of VI with three graphs. The use of VI has some benefits as follows: a) The data acquisition for mobile robot with gesture commands are achieved with easy and low costs and with a friendly HMI; on the one hand due to the friendly reconfigurable virtual instruments and on the other hand owing to the possibility of using the conventional equipment existing at the location of the mobile (transducers, command devices-actuators, etc.) b) The resulted prototype is available at the department laboratory of automatic control for research and training students. c) The data samples analyze can give us enough flexibility in testing various control techniques to elect the fitted control solution for our robot with gesture commands. 5. Conclusions Using National Instruments software (LabVIEW) and hardware (NI USB-6009) it was obtained a flexible, reliable, user-friendly and cost effective mini tool-box for training students in data acquisition, visualization and utilization for expected performances of the robot electric drive subsystem. In addition they can study experimentally the drive subsystem functionality. Now the students have the opportunity to make a wide variety of experiments in order to improve them knowledge in process control engineering based on NI hardware and software. This procedure introduces the students in the research and developments activities for process control.
Bul. Inst. Polit. Iaşi, t. LIV (LVIII), f. 3-4, 2008 15 A c k n o w l e d g e m e n t s. This research was made under funding of CEEX 131/2006 research grant with client Managerial agency for Scientific Research, Innovation and Technological Transfer Minister of National Education and Research 2006-2008. Received: July 9, 2008 Gheorghe Asachi Technical University of Iaşi, Department of Automatic Control and Applied Informatics e-mail: cpal@ac.tuiasi.ro *Department of Computer Science and Engineering e-mail: mike@cs.tuiasi.ro and ** Stefan cel Mare - University of Suceava Department of Electrical Engineering e-mail: pentiuc@eed.usv.ro R E F E R E N C E S 1. Murphy R., Introduction to obotics. The MIT Press, Cambridge, Massachusetts, 2000. 2. Niţulescu M., Sisteme robotice cu capacitate de navigaţie. Edit. Universitaria Craiova, 2002. 3. * * * PROJET Centaure, Réalisation d un robot mobil autonome. Ecole Polytechnique de Lille, 2005. 4. Pănescu D., Sisteme de conducere a roboţilor industriali. Univ. Tehnică Gheorghe Asachi din Iaşi, 1996 PAC-MAN, EECE 474 Project. 5. Borenstein H., Enerett H. R., Sensors and Methods for Mobile Robot Positioning. The University of Michigan, 1996. 6. Nicolson E. J., Tactile Sensing and Control of Planar Manipulator. Berkely, 1994. 7. Popescu P., Negrean I., Vuşcan I., Haiduc N., Mecanica manipulatoarelor şi roboţilor. EDP, Bucureşti, 1994. FOLOSIREA INSTRUMENTAŢIEI VIRTUALE ÎN MONITORIZAREA SISTEMULUI DE MOTOARE PENTRU UN ROBOT MOBIL CU COMANDA GESTUALĂ (Rezumat) Se prezintă folosirea unui sistem de instrumentaţie virtuală în scop didactic şi de cercetare. La ora actuală interacţiunea om calculator permite comunicarea între utilizatori şi sisteme robotice complexe. Pentru a realiza acesta s-a creat un dicţionar de gesturi care permite interacţiunea naturală cu orice tip de sistem informatic sau robotic. Experimentele au fost realizate cu ajutorul unui prototip de robot mobil echipat cu un sistem de calcul dedicat. În acest context s-a realizat interfaţarea şi urmărirea parametrilor funcţionali ale motoarelor sistemului cu ajutorul tehnologiei hardware şi software pusă la dispoziţie de National Instruments. Această abordare permite realizarea
16 Cristea Pal et al. unor analize complexe privind alegerea celei mai bune forme de control al acestui sistem de mişcare. De asemenea se studiază şi aspectele legate de siguranţa utilizatorului. După cum am menţionat această abordare permite o înaltă flexibilitate în testarea şi implementarea a diverşi algoritmi precum şi structuri hardware atât din punct de vedere al cercetătorului cât şi din punct de vedere al studentului în cadrul unor lucrări practice din domeniul controlului automat.