Design Features and Characteristics of a Rescue Robot

Transcription

1 Design Features and Characteristics of a Rescue Robot Amon Tunwannarux and Supanunt Hirunyaphisutthikul School of Engineering, The University of The Thai Chamber of Commerce 126/1 Vibhavadee-Rangsit Rd., Dindaeng, Bangkok Thailand Tel: , Fax: amon_tun@utcc.ac.th, supanunt_hir@utcc.ac.th Abstract - This paper presents a design and implementation of a rescue robot. It has two front arms with track mechanism and tracks link between front and rear wheels. With the double track robot system, it is good for unstructured landscape and able to climb over the pile of collapse. This robot is equipped with a lot of sensors such as IR temperature sensors, distance sensors, odometer sensors, pitch/roll, compass sensor, three pan/tilt CCD cameras and voice sensor. For simple and practical concepts, hardware design is divided into control/locomotion subsystem and monitoring subsystem. The RC airplane remote control and receiver are modified to use in control/locomotion subsystem. In monitoring subsystem, three 8 bit CPUs are used for sensor information managing and sending it to serial port of a computer wirelessly. The operator station not only shows all sensors information but also plots the route of victim access and locates victim positions based on simple triangular calculation technique. Furthermore, for looking over obstacles to find the victims from the top view, a pan /tilt camera is placed at the top of the mast which can stretch to 125 cm. height. Audio signal from voice sensor is filtered for selecting only wanted frequencies by the parametric equalizer. This rescue robot design was implemented and worked excellent in the competition, especially it can climb up the stairs with 15 cm. high steps to find the victims on the second floor. Keywords: rescue robot, double track, monitoring system, mast, victim access route I. INTRODUCTION There are some developing of rescue robots for commercial purpose but still in a small group of research and very expensive. A lot of rescue robot competitions have been held lately with the main purpose of encouraging researchers to develop their robots for practical usage in the real situations.. The most popular rescue robot contest is the RoboCup Rescue Robot League Competition, which started in For rescue robots, the basic objective is usually used to survey and locate the victims of the disasters. They take the places of human who are sent to the risky area for finding the victims. There are many types of rescue robots for example, the Orpheus mobile robot from RoBrno team, Czech Republic, the winner of Rescue Robot Championship 2003 Competition, is the rescue robot which is controlled by joystick and head mounted display like virtual reality head set [1]. The other is the rescue robot from CEDRA team, Iran, the first runner up. Their robot has six wheels locomotion, which can operate well in unstructured environment [2]. Every team tries to put more reliability and special features for their rescue robots to get the maximum points in the contest. So we purpose the track type rescue robot, which has two front arms with tracks, and tracks link between front and rear wheels. With this tracked dual rotating arms feature, it allows the robot to easily to climb over the pile of collapse. We divided hardware design into two parts as control/locomotion subsystem and monitoring subsystem for simple, reliable and practical concepts. The plots of victim accessing route and victim location are shown at operator station. Moreover, this rescue robot has the mast, which is equipped with a pan / tilt camera and able to stretch to 125 cm. height for looking over obstacles to find the victims from the top view. The parametric equalizer is also developed and included in the operator suitcase for filtering the unwanted frequencies from victim voice. For other features, our robot was designed and implemented to correspond with the rules of the competition to identify the detailed victim information accurately and access all victims as fast as possible. II. CRITERIA OF DESIGN Our criteria of design a rescue robot is based on Thailand Rescue Robot Championship Competition rules They are the international rules, which will be used in the Robocup Rescue Robot Championship 2005, held in Osaka, Japan. The size of robot is limited to 70x70x70 cm 3, total weight should not be more than 70 kg. The competition rules and scoring metric both focus on the basic Urban Search and Rescue (USAR) tasks of identifying live victims, determining victim condition, providing accurate victim location, and enabling victim recovery, all without causing damage to the environment. All teams compete in several missions (three different arenas) lasting twenty minutes with the winner achieving the highest cumulative score from all missions. The details 277

2 Fig. 1 Performance metric used for scoring [3]. of the performance metric used for scoring are shown in Fig. 1 [3]. Because of our time constraint and the arenas in the contest are placed by a lot of unpredictable obstacles, we decided to create the non-autonomous rescue robot and use one person only to control remotely. In this case, our score will be divided by 4, however we hope that the penalties should be reduced and our score should be greater than the autonomous robot. All sensors are set up to correspond with the rules and in order to get the maximum score. The robot needs multiple sensors for map creation, victim location, victim situation, victim states and sensors for penalty discouragement. III. RESCUE ROBOT HARDWARE CONCEPT Our main design concept is using the simplest method but highly effective and reliable. This robotic system composes of the control/locomotion subsystem and monitoring subsystem, see Fig. 2. For control part, the versatile multifunction 9-channel transmitter for airplane, FF9, is used to control all functions of this robot. For locomotion part, we design the double track type rescue robot with multiple sensors as mentioned before. And for monitoring subsystem, we made the sensor information managing board, which interfaces to all sensors. This board will transform analog/digital signal from sensors into formatted information and ready to send. All sensor information will be sent wirelessly to a notebook computer by serial transmitter. We separately send the audio and video signal via an analog transmitter. With this concept, three communication parts were set up. Although this concept may not be the best for robot communications, but it is the most suitable way to implement and finish in time. The control/locomotion subsystem is described first, then the details of mechanics and all sensors will be illustrated. Finally, the monitoring subsystem will be explained. IV. CONTROL/LOCOMOTION SUBSYSTEM Before describing the remote control unit and all sensors in this robot, the details of mechanics are illustrated. Fig. 3 specifies the various parts of the rescue robot. The hardware is separately explained as the following items. A. Body and locomotion driving system The 3.5 mm. thick aluminum sheet is folded to be the base frame and the locomotion driving system with all motors are placed in this frame in order to have the low level center of gravity. Our robot dimension is 50x60x60 cm 3. Two 24 V DC motors are used for driving two front wheels by driving each side separately. Because we need to drive both moving tracks (linked between front wheel and rear wheel) and arm tracks, two shafts at same rotating center are designed, as shown in Fig. 4. The double arm tracks are very useful for climbing over the pile of collapses. Arm Track A/V 125 cm high camera mast Compass Control / locomotion Subsystem Temp Robot Distance CEO MISSION I Battery& Weight Wheel Track Operator Side Notebook Computer Remote Wireless PCM MHz Compass Arm angle Odometer Robot Side Fig. 3 The robot hardware details. For driving arm track Monitor Wireless serial Video/Audio Parametric Equalizer Wireless 400 MHz Wireless 1.2 GHz Wireless serial Video/Audio Monitoring Subsystem Information Managing Board Camera Voice For driving arm track & wheel track For driving wheel track (movement driving) Fig. 2 Block diagram of rescue robot. For driving arm 278

3 Fig. 4 Track driving system and Robot arms driving system. B. Robot arms driving system These arms are created in order to raise its body up for better climbing. Because the rotating center of the front arm is the same position of the front wheel centers, so another hollow shaft is required to be placed between two shafts of track driving system (same rotating center), in Fig. 4. Two 24V dc motors and chains for power transmission are used. Fig. 7 The brake system. Fig. 8 Operation of weight transfer unit. Fig. 5 The robot head mechanism and sensors Fig. 6 Channel details in FF9 remote control and compass module C. H e a d o f r o b o t This is a very important part because it is the place on which many sensors are equipped such as two color CCD camera, distance sensor, temperature sensor, laser pointer, voice sensor. Its mechanism provides the pan and tilt ability by using two RC servomotors. The panning mechanism is placed under the tilt mechanism because we will use the laser pointer at the top of robot head for distance measuring calculation, which will be discussed later. The mechanism of robot head is shown on Fig. 5. D. The camera mast As the obstruction in the competition field, a lot of 80 cm. high partitions were placed for simulating the situations. The distance between partitions is quite narrow (max = 80 cm.), so we need to look over these partitions for finding victims and for better-controlled movement and not to touch the partitions. Thus the mast added on at the rear part of robot body giving the bird s-eye view is necessary. This mast is modified from car antenna and equipped with a color CCD small camera and small pan/tilt mechanism at the top of mast. It works very well because it can stretch up to 125 cm. high with lightweight mechanism. E. Brake system This mechanism is seriously required when robot stay on ramp or is climbing steps, because the robot needs to park at the ramp for surveying and stop for climbing over each step. The brake system is installed at the shaft of rear wheels because there is no room at the front. Fig. 7 shows our brake system with spring coil and two servos. F. W e i g h t t r a n s f e r u n i t The robot centers of gravity (C.G.) need to be closed to the front as much as possible, so the bottom of the robot can be raised up and climb over the step. Because the quite high step (higher than diameter of the front wheels) and the moment from brake system and camera mast, we need to install the weight transfer unit at the front in order to move its C.G. pass over the edge of step (fulcrum point). Thus a battery, 12V 7AH, 2.5 kg. and the sheet of 3 kg. lead are attached in order to overcome this step as shown in Fig. 8. G. Remote control unit The digital proportional radio control, T9CAP, FF9 Futaba is selected for controlling the robot because its high reliability even the receiver is in the concrete area. Moreover there are up to nine channels and has many operational functions in each channel and between channels such as inverting, mixing, end point setting, subtrim of position, fail safe, etc [4]. All channels are 279

4 assigned and used according to the channel controllable ability and ergonomic. The details are in Fig. 6. H. s The infrared (IR) temperature sensor is chosen to use for measuring the victim temperatures remotely and contactlessly. We use the Raytek MID module [5], which has the important specifications to be concerned as - Optical Resolution = 10: 1 provides the ability to measure temperature of the pointed area. - The miniature sensing head can be separated from main unit and has small size and lightweight (see Fig. 5). For visual system, two color CCD cameras are installed on the robot head. The 1 st one is for the front view and the 2 nd is for the rear view as in Fig. 5. Additional color CCD camera is installed at the top of mast as in Fig. 6. As the voice sensor, a small conventional wide range condenser microphone is equipped at robot head. It is installed at the center of parabolic cone for voice focusing as in Fig. 5. The sensing voice is sent together with the selected video signal via the 1.2GHz. 1 W wireless audio/video transmitter. At the remote operator site, this voice will pass via the parametric equalizer for selecting only the wanted frequencies. The infrared distance sensor, Sharp GP2Y0A02YK, with the detection range cm is used to measure the distance from the robot head to the pointed object (see Fig. 5). It has less influence on the colors of reflected objects and their reflectivity, due to optical triangle measuring method [6]. Our odometer sensor is comprised of a disc with holes along its perimeter and the infrared transmitter and receiver module. Two sets of this sensor are installed at each side of the shaft which drives the front wheels. The data of each wheel sensor can be used to plot the victim access route. Arm angle sensors are necessary for remote controlling. This information is sent to remote computer for robot graphic creation. A 10 turns potentiometer resister is use as sensor for each side of arm. The EZ-Compass 3 module is used for robot navigation. It is a low cost advanced pitch/roll Distance sensor IR Temp. Left Arm Angle Right Arm Angle Odometer s (Left/Right Wheels) s Information Managing Board A/D 12 BIT 8 CH. CPU 2 89C2051 LCD DISPLAY 16x2 CPU 1 (MAIN) 89S52 CPU 3 89C2051 Compass Pich Roll s Wireless Serial Pan/Tilt Angle Signal from R/C Fig. 9 Block diagram of sensor information managing board. compensated compass/magnetometer system. This module not only outputs the azimuth but sends the dual axis tilt of pitch and roll and temperature data over the standard RS- 232 interface [7]. Due to a strong metal object or magnetic anomaly affects to this module so the module should be placed as far as possible from the source of that anomaly. In this case we installed it at the top of robot body and placed in the plastic box, see Fig. 6. IV. MONITORING SUBSYSTEM A. information managing board From block diagram in Fig. 2, there are two communication paths in this subsystem. Video/audio signal are separated from all sensors and sent by 1 W, 1.2 GHz. analog transmitter. The rest of sensor signals used the 400 MHz. serial communication for sending all sensor information back to operator. This sensors information managing board, in Fig.9, collects all sensor signals and transforms to formatted information. Three MCS-51, 8 bit CPUs are used in this board. The CPU1, main CPU, manages key switches, LCD display, wireless serial transmitter and all sensors except odometer sensors handled by CPU2 and pan/tilt angle sensors handled by CPU3. All sensor information we get from this board is sent wirelessly to serial port of a computer at the operator site. B. Operator monitoring software At operator station, the operator monitoring software was developed with visual basic in order to process the data from the sensor information managing board and plot the victim access route and its location. The number of pulses counted by odometer sensors and the azimuth angles from compass sensor are used to plot the victim access route as shown in Fig.10. However because of track wheels and movement slipping, the moving route of robot on the map may not be accurate. So we need to update the robot position from time to time. In the competition, we have the arena map and landmarks such as poles or stair 280

5 steps for updating robot position when we lost. At the top of robot head, a laser pointer is attached for marking center of camera and IR temperature sensor. Moreover we can use it for distance calculation by simple triangular method. Fig. 11(a) shows a side view of calculating method. If we tilt and point the laser dot to the known position, pole M1, the distance from pole M1 to robot is d = h/tan(t). Then the coordinate of robot can be obtained by x=x M1 +d 1 cos(a 1 + P R ), y=y M d 1 sin(a 1 +P R ). In Fig.11 (b), the victim position can be found at x V1 =x d 2 cos(a 1 P L ), y V1 =y d 2 sin(a 1 P L ). The arena map, the calculated information and all sensor data are displayed on the notebook computer and furthermore, audio/video signal from robot will be monitored at the suitcase as shown in Fig.10. B. testing The obtained results have been satisfactory for all sensors. The IR temperature sensor can accurately measure the temperature of victim. The data from compass sensor is quite fluctuate, but the programmed software can filter this ripple and get quite satisfied results. The victim access routes are plotted with some errors but not more than 50 cm./500 cm moving. With self-locating update and the route plotting, we succeed in the victim position locating. Fortunately, the arena grid is 50x50 cm 2, so we never make a mistake in specifying the victim position. Three cameras work excellent, especially in the area beneath the stairs or in the low illumination places. However the video picture will be so pale or too much white when the robot works in the bright light area. d1 d2 (X,Y) (X=0,Y=0) Fig. 12 The rescue robot in the arenas of the competition. Fig. 10 Plotting of victim access route and locating the victim position on the notebook computer, and A/V Suitcase at operator station. Pole M 1 T d = d h tant ( ) T T = Tilt angle h V1 (Xv1,Yv1) d 2 (XM1,YM1) P L ( A1 P L ) A = Azimuth angle P = Pan angle a) Side View b) Top View Fig. 11 Self-locating and victim locating by triangular calculation. V. TESTING RESULTS AND DISCUSSIONS A. Mechanic and movement testing This rescue robot works very well in all three arenas of the competition. The camera on the top of 125-cm. high mast is used for looking over the 80-cm. high partitions and accurately mark the locations of victims in the first area. In the second arena, it can climb the 15-cm. high steps to find the victims with climbing up speed 7 steps in 2 minutes. At the most difficult arena, it climbs over the pile of collapse well, see Fig. 12. The controller should be more careful with obstacles tie or stuck in the wheel tracks or fall over the robot. M1 d 1 P R A 1 VI. FUTURE WORK This is our first version for RoboCup competition. Our robot can run with speed only 0.25 meters /second and not practical in real situations. Many capabilities should be enhanced, such as the dust and water spraying proof body, the thermal resist wheel tracks, lightweight body material, using Ni-Cad instead of lead acid battery, using higher efficiency dc motors, the controllable light filter for camera. All wireless communications should be integrated to WiFi IEEE and the robot side view locomotion graphics should be added. VII. CONCLUSIONS The rescue robotics system with its arm track and wheel track mechanism has been briefly described. The remote monitoring system of robot was provided to manage a lot of sensor data for victim identification, localization and navigation. The robotic system has been tested in many areas and competitions. Its performance was observed to be excellent in unstructured environments and successfully climb over the 15cm. high steps. Finally, it did make very good score and got the 1 st runner up award with 130,000 Baht prize from Thailand Rescue Robot Championship REFERENCES 281

6 [1] Ludek Zalud, RoBrno Czech Republic, RoboCup Rescue Robot League Competition, Italy, July [2] Meghdari,etc., CEDRA Iran,RoboCup Rescue Robot League Competition, Italy, July [3] RoboCub Rescue League, USAR Robot Competition Rules 2004, /rules.htm [4] Futaba Corp., Manual of T9CAP R/C system, 2004 [5] Raytek Corp., Thermalert manual, [6] Sharp Corp., Distance measuring sensors notes,2003. [7] AOS Inc., EZ Compass-3 manual, 282