AUTOMATIC CABLE SPOOLING for A ROBOTIC VACUUM CLEANER

Transcription

1 AUTOMATIC CABLE SPOOLING for A ROBOTIC VACUUM CLEANER 1 Min-Chie Chiu, 2 Long-Jyi Yeh, and 2 Cheng-Chen Shih 1 Department of Automatic Control Engineering, Chungchou Institute of Technology. 2 Department of Mechanical Engineering, Tatung University Abstract The main purpose of this paper is to create a mechanism that can automatically gather and loosen the power line on the mobile cleaning robot. A single-chip Microcontroller PIC18F452 is used as a control core in the robot. The robot driven by two stepping motors is equipped with six infrared-ray-distance detectors to detect obstacles and calculate the real distance between the sensor and obstacles. Moreover, a cable rewinding/loosening controller with a three-directional tension detecting switch is used to detect the appropriate rewinding/loosening. A cable-tray used to gather the cable is driven by a DC motor. The electric power of the robot is supplied by four sets of 12 v Pb-made batteries. The vacuum cleaning robot s plug-in action will be performed after the edge-searching is completed. The sweeping mode is started up and a s-type sweeping path is executed. The cable will be adjusted by using the cable rewinding/loosening controller during the vacuum-cleaning process. The robot will rewind the cable while moving back to the wall socket if the ground-cleaning is completed. Experimental results reveal that the robot can rewind and loosen the cable effectively during the vacuum-cleaning process. Key Words: infrared rays, microcontroller, cable spooling * Corresponding author: Min-Chie Chiu minchie.chiu@msa.hinet.net Mailing address: Department of Automatic Control Engineering, Chungchou Institute of Technology 6, Lane 2, Sec.3, Shanchiao Rd., Yuanlin, Changhua 51003, Taiwan, R.O.C. 1

2 1. Introduction Research for robots was started by employing photo reflection to guide a path of black tape [1]. In 1995, Audo [2] proposed a multi-ultrasonic-detector system to detect the obstacle distance in order to guide the robot along the wall. In 1998, Yata[3] proposed a obstacle-avoiding mechanism by using angle detection from the ultrasonic-detector. Recently, a vision-guided system used to direct the robot s motion by employing a web cam has prevailed [4,5]. Therefore, the robot has been widely adopted in house-keeping work such as the vacuum cleaning. Currently, even though a DC electric powered battery widely used in ground-cleaning robots can provide ground-cleaning convenience, the higher electricity-recharging frequencies and the longer recharging time will seriously interrupt the cleaning process. One such robot, roomba, created by irobot for ground cleaning, moves back to the electric recharging station. Therefore, the duration of battery is important. However, it s suction force during ground vacuuming becomes weak. Moreover, the life time of the battery will be short and will be renewed due to repeated recharging. Subsequently, the cordless vacuum cleaning robot becomes cumbersome and inefficient. In order to improve the drawback of a cordless vacuum cleaning robot, a cord vacuum robot equipped with an automatic plug-in system [6] as well as a cable rewinding/loosening control mechanism becomes essential. In this paper, a cord vacuum cleaning robot with AC power is developed by adjusting the cable with an automatic cable rewinding/loosening controlling system. The cord vacuum cleaning robot which is cheaper than the cordless model has a convenient access to its power supply and a flexible sweeping range. 2. System Design As indicated in Figure 1, a single-chip microcontroller PIC18F452 is used as the control core in the robot. The eight-bit signal distance between the sensor and the obstacles detected 2

3 by infrared-ray-distance detectors is obtained and processed by a filter. The signal will be transmitted to the kinetic control modules for further path-correcting processes if path-correction is required via the judging process. In case there is an obstacle located on the route, the infrared-ray-distance detector will emit an obstacle-existing signal to the kinetic control modules. The obstacle-avoiding module in the vacuum cleaning robot is then started up until the obstacle-existing signal vanishes; otherwise, the ground-sweeping modules will be performed and the cable rewinding/loosening control module will start up. The status of cable s tension will be detected by the cable rewinding/loosening control module when the cable length is insufficient during cleaning process. The cable will be released by the rewinding/loosening mechanism. However, the cable will be rewound if the cable is too long. Figure 1 System diagram of a vacuum-cleaning robot. 2.1 Structure of the vacuum cleaning robot As indicated in Figures 2~4, two infrared-ray detectors are positioned on each side of the 3

4 vacuum cleaning robot. The location plan of six infrared-ray detectors used to detect the obstacle is shown in Figure 5. The status of cable s tension will be continuously detected by a tension-detecting mechanism which is installed on the right side of the robot during the ground-sweeping process. Figure 2 The side view of a vacuum cleaning robot. Figure 3 The plan view of a vacuum cleaning robot. 4

5 Figure 4The front view of a vacuum-cleaning robot. Figure 5 The location of infrared-ray-distance detectors. 5

6 2.2 The distance of an obstacle detected by an infrared-ray detector As indicated in Figure 6, an infrared-ray detector (GP2D12) widely used and provided in the robot market is adopted in our vacuum cleaning robot. Figure 6 Infrared-ray detector (GP2D12). The characteristic curve of GP2D12 s voltage output with respect to distance is shown in Figure 7. As the efficient detecting distance is between 10cm~80cm, the relationship for the above range will be considered. As indicated in Figure 7, the related curve is non-linear. In order to transform the signal into a real distance value, the zone of 10~80cm is divided into ten linear pieces shown in Figure 8. 6

7 Figure 7 The characteristic curve of GP2D12 s voltage output with respect to distance. Figure 8 The zone of 10~80cm divided into ten linear pieces in GP2D12. and 115. As indicated in Figure 9, the first interval of 10~11 cm is mapped to digital values of 125 Figure 9 A digital mapping with respect to the detecting distance For a distance-signal located among the first interval (adc1), the related distance can be calculated as the following. adc1 = 115 ~ 125 y1 = 11 [( adc1 115) /10] (1) Where adc1 is the digitalized value of the voltage-output obtained by the A/D transform from micro-chip PIC18F452. Likewise, the distance for other intervals can be calculated as follows. adc2 = 104 ~ 115 y2 = 12 [( adc2 104) /11] (2) 7

8 .. adc10 = 20 ~ 31 y2 = 80 [( adc10 20) /11] (3) The real distance between the infrared-ray detector and obstacle can be approached by using the signal transform of Eq. (1) for a specified interval. 2.3 Cable tray As indicated in Figure 10, to facilitate the spooling and compact the volume, a single-layer cable-tray constructed with two pieces of transparent plate is located on the bottom plate of the robot. The related length and diameter of the electric cable is 5 meters and 8 mini-meters. The cable is driven by a DC motor that loosens and rewinds. Figure 10 Cable tray. 8

9 2.4 Cable rewinding/loosening control module The length of the electric cable will be automatically adjusted when the ground-sweeping process is performed. As indicated in Figure 11, to appropriately control the length of the cable, three-directional tension detectors for the cable shown in Figure 11 are established in advance. As indicated in Figure 12, the status of the cable s tension will appear in three directions when the vacuum cleaning robot is moving. In addition, three springs are installed in each direction so that the cable is in a neural position when the robot stops. The limit switch on the right side/left side will be touched when the right side/left side pulling is performed. Similarly, the limit switch on the upper side will be actuated when upper side pulling is performed. Consequently, the signal emitted from the limit switch will be transmitted to a cable rewinding/loosening control module to adjust the cable by actuating the DC motor of the cable tray. Figure 11 A tension-detecting mechanism. 9

10 Figure 12 (a) Cable pulled on right/left side; (b) Cable pulled on upper side;(c) Cable in no pulling condition. 2.5 Electricity detecting module As indicated in Figure 1, four sets of 12V/4Ah batteries (YUASA) are placed in the vacuum cleaning robot. To monitor the status of the electricity for each battery, the electricity detecting module is equipped with a chip IC TL431 shown in Figure 13. Four conditions of the battery are discussed below. As indicated in Figure 13(a), the LED will be not light when the voltage of the battery is lower than nine volts. The color of the LED will turn to yellow when the voltage of battery is 9~11 volts. Likewise, the color of the LED will turn to green when the voltage of battery is 11~12 volts. Consequently, the color of the LED will be in the red when the voltage of battery is greater than 12 volts. 10

11 (a) (b) (c) (d) Figure 13 The electricity detecting module for the battery. 3. Path Planning of Vacuum Cleaning Robot In order to facilitate the cable-adjusting of the rewinding/loosening when the vacuum cleaning robot is moving, an s-type sweeping path [7] is adopted. As indicated in Figure 14, the vacuum cleaning robot will move back to the socket when the sweeping time is even and the sweeping distance is near the total cable length. The related diagram of the sweeping path is shown in Figure

12 Figure 14 Sweeping path for a vacuum cleaning robot. 3.1 Electricity detecting module Figure 15 The diagram of a sweeping path. 12

13 The moving position of a vacuum cleaning robot will be continuously changed under the sweeping mode. As indicated in Figure 16, the cable will be released for the real-line path and be pulled for the dashed-line path. The related cable-adjusting algorithm is shown in Figure 17. Figure 16 The path for cable pulling and releasing. Figure 17 The cable-adjusting algorithm. 13

14 4. Result and Discussion 4.1 Infrared-ray detection In order to obtain the distance between obstacle and infrared-ray detector, a non-linear characteristic curve is divided into ten pieces from 10~80 cm. Thereafter, the distance can be estimated by using a mathematic calculation for each approximate linear segment. As indicated in Figure 18, a comparison of real distance data and estimated distance data is rechecked. The related data for both real distance and estimated distance is shown in Table 1. As indicated in Table 1, it is obvious that the distance-detecting error will be acceptable if the distance is below 50 cm. Figure 18 (a) Real distance measurement; (b) Mathematic calculation of the distance. 14

15 Table 1 The result of both real distance data and calculated distance data. Real distance (cm) calculated distance (gray color for wall) (cm) Experiment of automatic vacuuming for a robot In the experimental process, the cleaning area was 450 cm in length and 280 cm in width. The continuous photos for a vacuum cleaning robot sweeping the ground in an s-type path without obstacle is shown in Figure 19. It is clear that the cable-adjusting function for pulling and releasing is appropriate. As indicated in Figure 20, the vacuum cleaning robot will move back to the socket along the wall. It is obvious that the cable will be suitably pulled by the cable tray. Consequently, the cable-adjusting mechanism can be efficiently performed during the robot s various motions so that the ground-sweeping work can be successfully achieved without extra cable interruption. 15

16 Figure 19 The continuous photos for a vacuum cleaning robot sweeping the ground in a s-type path without an obstacle. 16

17 Figure 20 The continuous photos for a vacuum cleaning robot moving back to the socket along the wall after the ground-sweeping work is finished. 5. Conclusion In this paper, an intelligent robot equipped with a cable-adjusting mechanism which can rewind and release the electric cable is developed. It can be used as a carrier for various existing AC-power vacuum cleaners. Three-directional tension detectors for the cable are built into the robot. The status of the cable s tension can be detected by the detector to actuate the cable tray to rewind/loosen the cable correctly when the vacuum cleaning robot is moving. In order to complete the ground cleaning work, an s-type sweeping path is adopted. Six infrared-ray detectors are equipped on the front side, right side, and left side of the vacuum cleaning robot to detect an obstacle within 10~80 cm. The signal emitted from the infrared-ray detectors will be transmitted to the A/D module of the micro-controller to 17

18 estimate the distance between obstacle and detector. Moreover, the status of the battery's electricity will be monitored online by using a electricity detecting module. References 1. Paromtchik, Igor E. and Asama, Hajime, Optical Guidance System for Multiple Mmobile Robots, In Proc. IEEE Int. Conf. Robot. Autom. (ICRA),volume 3, pages , Ando, Y. and Yuta, S., Following a wall by an Autonomous Mobile Robot with a Sonar-Ring,IEEE International Conference on Robotics and Automation, Vol.4, pp , Yata T., Kleeman L. and Yuta S., Wall Following Using Angle Information Measured by a Single Ultrasonic Transducer,IEEE International Conference on Robotics and Automation, Vol.2, pp , Das, A.K., Fierro, R., Kumar, V., Southall, B., Spletzer, J.,and Taylor, C.J. Real-Time Vision-Based Control of a Nonholonmic Mobile Robot,Proceedings of the 2001 IEEE International Conference on Robotics & Automation Seoul,Korea-May pp , Oliver Schreer,Ingo Feldmann,Uli Golz,Peter Kauff, Fast And Robust Shadow Detection In Videoconference Applications, VIPromCom-2002, 4th EURASIP-IEEE Region 8 International Symposium on Video/Image Processing and Multimedia Communications, pp.16-19, Yeh, L. J., Win, Jun-Hong, Wall Plug-in Power Supply System for AGV, Proceedings of the 25 th National Conference on the Chinese Society of Mechanical Engineers, Taiwan, R.O.C., Chiu, M. C., Yeh, L. J., Lin, Y.C., The Design and Application of a Robotic Vacuum Cleaner, 2008 Conference on Precision Machinery and Manufacturing Technology- PMMT, pp. B15,