2012 Florida Conference on Recent Advances in Robotics 1 Boca Raton, Florida, May 10-11, 2012

Robotic Tennis Ball Collector

Neha Chawla, Wuqayan Alwuqayan, Ahmed Faizan, Sabri Tosunoglu Department of Mechanical and Materials Engineering

Florida International University Miami, Florida, USA

305-903-8455, 786-419-0915, 786-972-7523, 305-348-1091 nchaw002@fiu.edu, walwu001@fiu.edu, afnu001@fiu.edu, tosun@fiu.edu

ABSTRACT This paper describes a robot to collect tennis balls in a driving range and is called as Robotic Tennis Ball Collector (R.T.B.C). This system avoids stopping the players for ball collection permitting a higher use rate of the field. The purpose of this prototype is to avoid any object found on its way and pick up tennis balls by detecting and then collecting them. R.T.B.C will reduce the time and effort required in collecting the tennis balls from around the tennis court.

1. INTRODUCTION Robots have always been an object of fascination in our society. They have been portrayed as humble servants of man as well as evil creations that rise to overthrow their masters. All robots share one thing in common at the root of their design and purpose - they can perform tasks in place of humans. Life is filled with many repetitive tasks, and if robots are able to perform those tasks, they can help to ease an overarching burden. With that said, robots are optimal replacements for humans in a multitude of scenarios. As simple as it may seem, the primary action in many repetitive tasks is picking up objects and moving them to other locations. Be it picking up garbage from the floor, moving parts along an assembly line or removing fallen debris, robots that can pick up and move objects will always be useful. Tennis players develop their skills by repetition, in order to achieve that goal they practice with several balls one after the other. After the balls are finished, the player and the instructor have to pick up the balls to continue the training, wasting money and valuable time. Nowadays, the balls pick up and its delivery to the balls dispensing machine is carried out with human intervention, by using some machines with trolleys but always driven by humans. In order to improve this task, the need for dedicated and specialized vehicles is becoming a must, not only to speed up the task but also to reduce the maintenance costs of the whole system. The main goal of this project is to design and build a prototype of a tennis ball collector which will be useful indoors and outdoors. The prototype is able to walk freely on the floor avoiding obstacles. The prototype is able to locate tennis balls and pick them up

2. HISTORY OF TENNIS Some people believe that that the ancient Egyptians, Greeks, and Romans played different versions of tennis. Drawings and descriptions of any tennis-like games have not been discovered, but a few Arabic words dating from ancient Egyptian times are

cited as evidence. The theory goes that the name tennis derives from the Egyptian town of Tinnis alongside the Nile and the word racquet evolved from the Arabic word for palm of the hand, rahat. Tennis was first created by European monks to be played during religious ceremonies for entertainment. When it began, the player hit the ball with the hand. Soon after that leather glove came into existence which was later replaced with a handle for effective hitting and service of the ball and thus a racquet. Tennis balls underwent frequent alterations due to the evolution of racket from the first wooden ball to leather ball filled with cellulose material. The game was cherished by the monasteries across Europe during the 14th century. The royal family of France adopted this game during 16th and 18th centuries and was called Jeu de paumme and was regarded highly by kings and noblemen as the game of palm. The French players would shout Tenez which meant Play when the game would begin and later the game was called Tennis. In 1480, Louis XI of France forbade the filling of tennis balls with leather, sand and sawdust but instead be made with good leather and filled with wool. Scottish craftsmen made tennis balls from a wool-wrapped stomach of sheep or goat and tied with rope. Some that were recovered from hammer beam roof of Westminster Hall during restoration were found to be manufactured from a combination of putty and human hair. In 1874, Major Walter Wingfield acquired the patent rights for equipment and rules for the game which bore close resemblance to modern tennis. Charles Goodyear invented vulcanized rubber and since then Germans have been most successful in developing vulcanized air filled rubber balls. The first tennis court emerged in US in 1874. The original court devised by Wingfield was in the shape of an hourglass which tapered at the net. It was shorter than the modern court which we have today. Wiingfields design of tennis court and rules underwent several changes since then till the game gave to the modernized version which is played today. Later the game spread to different parts of the world like India, Russia, China and Canada. In 1877, the All England Club held the first Wimbledon tournament, and its tournament committee came up with a rectangular court and a set of rules that are essentially the game we know today. The net was still five feet high at the sides, a carryover from the games indoor ancestor, and the service boxes were 26 feet deep, but by 1882, the specifications had evolved to their current form.

2012 Florida Conference on Recent Advances in Robotics 2 Boca Raton, Florida, May 10-11, 2012

Figure 1: Early field-tennis

Tennis balls must conform to certain criteria for weight, size, deformation and bounce criteria to be approved for regulation play. According to the International Tennis federation (ITF) the official diameter of the tennis ball is approximately 6.7 cm (2.63 in.) and weight is around 57 gms. It is generally bright green in color. To modify their aerodynamic properties they are covered in a fluffy fibrous felt. A ball is tested for bounce by dropping it from a height of 100 inches (2.54 m) onto concrete; a bounce between 53 and 58 inches (1.3462 - 1.4732 m) is acceptable (if taking place at sea-level and 20C / 68F; high-altitude balls have different characteristics when tested at sea-level). Modern regulation tennis balls are kept under pressure (approximately two atmospheres) until initially used. Professional tennis matches can generally last for more than 3 hours with a rest period of little more than 10 minutes between sets. Training for such endurance matches becomes difficult without a partner of adequate skills hence tennis players use automatic ball launching machines to train without a partner. An automatic ball launching machine that holds 100 balls will launch balls at an average rate of 10 balls every 29 seconds. Therefore, the total time the machine can last without the need to refill would be

Hence the maximum time that a tennis player can play with an automatic ball machine is around 4minutes and 50 seconds. After this, the player will have to stop to collect around the tennis court using a bottom loading basket. This is a stressful and time consuming procedure which is generally despised by avid players. By experimenting it was shown that it would take in an area of

2:15 to manually pick up 85 balls. It was thus determined that the player would take 2 minutes to pick up all the balls after using the full capacity of tennis ball machine.

Hence, it shows that according to the available technology, a player will spend approximately 35% of time collecting tennis balls instead of playing. The delay also leads to long annoying and tiring breaks and increases the match time considerably making the players more tired.

3. CONCEPTUAL DESIGNS Employing humans to collect balls from around the tennis court is generally done while playing a professional match but is not feasible for players while training because it will be costly. Various projects have been performed by students in colleges to find a solution for collecting balls around the tennis court. They have used the knowledge of Robotics to build robots which could perform the required tasks. Listed below are a few examples of the projects that were done for collecting the tennis balls.

3.1 Vacuum Cleaner Type Collector A tennis ball collector was designed on the principle of a vacuum cleaner. The handling is simple for any person. The capacity of the collector is up to 200 balls.

Figure 2: Conceptual design 1

3.2 Eagnas Roller Ball Collector Eagnas roller ball collector is a simple and effective way of quickly and easily gathering up tennis balls from the tennis court. As it is rolled along the balls pop up through the bars and get into the barrel section. Once all the balls are collected the collector is up-ended and sits upon the handle. A locking pin can then be used to prevent the barrel from turning and a section of the barrel hinges opens as a door.

2012 Florida Conference on Recent Advances in Robotics 3 Boca Raton, Florida, May 10-11, 2012

Figure 3: Conceptual design 2

3.3 Bear Claw Collector There have been several products which are introduced in the market in order to collect the tennis balls. Robots have been designed to collect balls from around the tennis court. Bear claw tennis ball collector has been designed by students at Berkeley University which uses a camera with color tracking that navigates to tennis ball and uses the mechanical claw to grab the ball, lift it and put in the onboard basket.

Figure 4: Conceptual design 3

3.4 Ballbot Project BallBot Project by Dominic Ford consists of a microcontroller which captures frames from camera on board the robot, analyses them, locates objects which look like tennis balls, navigates to them and collects them. After collecting all the balls around the court, it dumps all the balls in the assigned location.

Figure 5: Conceptual design 4

4. PROPOSED DESIGN When we decided that our final project would be a robotic tennis ball collector we had several ideas on the concept and the design. After trying to incorporate every important aspect of the different designs we considered we came up with our ideal design. The ideal design would be something as described here on. It would have an RC platform with the cavity or enclosure for storing the tennis balls underneath it.

The enclosure would have a one way valve which would act as a restriction offering motion of the balls only in one direction hence not allowing the balls to fall out once they were forced into the cavity or enclosure. The enclosure would have RC controlled gates in front of it which would open and close forcing the balls that are in its reach into the cavity. The RC platform would be able to charge using a charging pad which works on the principle of inductive charging. Due to the constraints of time and fiscal inputs we had to modify the design to something that would be more feasible. The final design had the enclosure in front of it in the form of a box made out of Styrofoam backed with very thin plywood layer to add strength.

The RC controller for the gates had to different than the remote for the RC platform. In the ideal design it would be replaced with just a button on the controller for the platform since that is what its essential function is, to act as a switch. Also we had to scale the whole design down to be used for smaller sized Nerf balls instead of tennis balls. At the end of the day as a team we were satisfied with the prototype for the project as it showed our potential design and validated its feasibility.

2012 Florida Conference on Recent Advances in Robotics 4 Boca Raton, Florida, May 10-11, 2012

Figure 6: Prototype of the proposed design

5. BUILDING THE PROTOTYPE A miniature scale prototype was built, assembled, and tested. For demonstration purposes the prototype utilizes an RC platform. The building process was divided into four major steps: Remote control circuit Gate controlling circuit Ball cavity enclosure Actuators operated gate

5.1 Remote Control Circuit To build a remote control circuit, a microcontroller out of a broken helicopter was used (Figure 01). The microcontroller outputs were identified. There were two sets of outputs, the left trigger uses a common ground (IO2) with one node that goes from 0 to 5 VDC (IO1) and the other goes from 0 to -5 VDC (IO3). As the remote control throttle is increase from the lowered position to the top position the voltage from IO1 and IO3 increase from 0, being the lowest position, to 5 VDC and -5 VDC respectively. IO2 and IO1 are then connected to a relay in our transition phase. The relay named K2 uses 5 VDC to activate a contact that connects the two lower legs. When activated our Vss is then allowed to ground out the center of the two resistors, giving us a low value. The right trigger uses a different circuit due to the changes in the circuit in the helicopter micro controller. The controller has two pins, IO4 and IO5, for the right stick. When in the neutral position (middle position) both IO4 and IO5 will give 0 VDC. When the controller is moved into the lower position we will get IO4 at 0 VDC and IO5 at 5 VDC. Finally when the controller is moved in the upward position we get IO4 at 5 VDC while IO5 is at 0 VDC.

Figure 7: RC microcontroller

5.2 Gate Controlling Circuit In order to build a circuit that would control the open/close gate, a Boe-Bot circuit board was used. The Boe-Bot circuit board must receive and interpret signals that would be coming from the RC circuit. Since the Boe-Bot does not interpret negative voltage a ULN2030A transistor array had to be used. This chip uses 5 VDC to power it, same as Boe-Bot circuit board. When the node on the left is given 5 VDC the node directly to its right will drop to 0 volts and when the node is grounded to 0 VDC the respective node will produce 5 VDC. The nodes are paired off horizontally 2 to 17, 3 to 16 and 4 to 15 continuing in this order. Using our 0 VDC ground as VSS we can produce a drop in the Boe-Bots circuit board Pine #1 and #2 by grounding the node between the resisters to VSS.

Figure 8: Gate circuit and circuit diagram

2012 Florida Conference on Recent Advances in Robotics 5 Boca Raton, Florida, May 10-11, 2012

5.3 Ball-Cavity Enclosure A rectangular shape box was designed and built to resemble the ball-collecting enclosure. The box has an open frontend and its dimensions were carefully considered such that it will not restrict the front wheels motion of the RC vehicle (Table 01). The weight of the box was also taken into consideration. IT has to be adequate, light enough to be moved around by the RC vehicle, yet rigid enough to withstand mounted actuators and prevent any possible collapse. The box interior was made out of foam board and the exterior was made out of lightwood board for reinforcement. The ball-collecting enclosure was double coated for surface protection and mounted to the frontend of the RC vehicle with 5mm ground clearance to ensure smooth maneuver and operation. Width length height dimension inches

Table 1: Ball-cavity dimensions

Ball-Cavity Enclosure Dimension cm

Length 11.5 Width 16.5 Height 7

Figure 9: Balls cavity enclosure

5.4 Actuators-Operated Gate Servo- actuator gate was designed and built. The gate consists of two open/close claws that would push the ball inside the cavity via remote control. Claws dimensions were carefully selected (Table 02); one claw is longer than the other to insure necessary force required to push the ball all the way in. The shorter claw acts as a bull-guide to prevent balls from slipping away upon collection. The claw frame was made out of aluminum to minimize the weight without compromising the needed rigidity and strength (Figure 10). The claw body was made out of Styrofoam for easy mold and mount. The claws were double coated for proper protection and functionality. The assembly was connected to the actuator servos and mounted on the ball-cavity walls.

Table 2: Claws dimensions Gate-Claws Dimensions "cm"

Left Claw Right Claw Length 14 7

Height 7 7

Thickness 0.5 0.5

Figure 10: Gate-claws assembly

2012 Florida Conference on Recent Advances in Robotics 6 Boca Raton, Florida, May 10-11, 2012

6. PROGRAM ALGORITHM Two circuits were built to operate the open/close claws via remote control. The first circuit (RC-circuit) receives analog signal from the remote control unit and convert them into binaries via microcontroller and ULN2030A transistor array. The output binaries are transferred to the second circuit (Gate-circuit) inputs through ULN2030A transistor. The RC circuit receives continues 5 VDC thus its output remains 1 unless the circuit is tripped which leads to 0 VSS. A very high resistor was used in order to trip the RC circuit when the stick of the remote control unit is pushed UP. Gate-circuit input (P1) controls the status of the left and right actuators (P14 and P15). When the input is 1 (5 VDC) the gate remain close, and when the circuit is tripped the input would be 0 (VSS) thus the gate would open for 3 seconds enabling the user to position the RC platform in the proper place to collect the ball. A short and simple program code was made using PBASIC. To control the RC output two conditional statements were made and each would run certain subroutines.

1- If the input port is activated, the gate claws remain still. 2- If the input port is deactivated, the gate claws open for

three seconds and then close.

The code details are as follows: Table 3: Sample Code

'R.T.B.C. ' {$STAMP BS2} ' {$PBASIC 2.5}

counter VAR Word DEBUG ? IN1

IF IN1= 0 THEN Open IF IN1= 1 THEN still

END 'Subroutines' Open:

FOR counter = 1 TO 5 ' Number of pulses. PULSOUT 14, 750 ' Right servo stand still. PULSOUT 15, 850 ' Left servo full speed cw. PAUSE 100 NEXT

FOR counter = 1 TO 40 PULSOUT 14, 750 PULSOUT 15, 750 PAUSE 100 NEXT

FOR counter = 1 TO 6

PULSOUT 14,750 PULSOUT 15,650 PAUSE 75 NEXT RETURN

still:

FOR counter = 1 TO 5 ' Number of pulses. PULSOUT 14, 750 ' Reight Stand still. PULSOUT 15, 750 ' Left servo full speed ccw. PAUSE 100 NEXT RETURN

7. CONCLUSION A prototype of the proposed Robotic Tennis Ball Collector was successfully built. The design utilizes a remote control platform and integrates it with two other circuits. The first circuit receives analog signal from the remote control unit and transfer it to a binary through microcontroller and transistor. The second circuit receives the binary signal to control the open/close claws of the balls cavity enclosure. The prototype demonstrates the ability to maneuver easily and avoid obstacles along the way. The prototype displays minimum human intervention with the task on hand. However, there is still room for further improvements. The objective of the proposed design is to have a fully autonomous robotic platform to execute the task of tennis-ball-collecting. With more time and more available resources, the objective will be met. Furthermore, the model may incorporates some extra high-tech features such as ball weight and/or pressure check that will enable the R.T.B.C to distinguish between valid and invalid tennis balls.

8. REFERENCES [1] Heiner Gillmeister, Tennis: A Cultural History, Leicester

University Press, London, England, 1998. [2] Lus Fernando Costa Pacheco, Andr Joaquim Barbosa de

Oliveira, Antnio Fernando Macedo Ribeiro, Mobile Robot for Autonomous Golf Balls Picking , University of Minho, Guimaraes, Portugal, 2008.

[3] Justin Ellis , Tony Morelli, Amandeep Sohal, Autonomous Mobile Robots , University of Nevada, Reno, 2005.

[4] Johnathon Schultz, Peter Clain, Jesse Miner, Wall-E Robot, Final Report, Cornell University, Ithaca, New York, 2010.

[5] Ryan Collier, Mohammed Adham, Perry Haldenby, Kevin Smith, Autonomous Tennis Ball Collector, Design Report, University of Waterloo, Ontario, Canada, 2009.

[6] Kevin Dluzen, Jonathan Hall, Diyang Qiu, PV Autonomous Golf Ball Retriever, University of Illinois at Urbana Champaign, 2012.

[7] Rodrigo Andres Barbosa, Karina Chang, ,Luxon Laborieux , Juan Zuluaga, Self-Piloted Tennis Ball Collector, Final Report, Florida International University, Miami, Florida, 2008.