Introductory Description

Transcription

1 Introductory Description After months of research, I have decided to build a walking robot. Because the robot will be walking on legs, rather than rolling on wheels, it will be able to traverse over many different terrains. If time permits, I would like the robot to be able to walk on rough terrain and transform to wheels when traveling over smoother surfaces. Since time and resources are limited, the project I propose will only get me closer to the final application. What I propose is for the robot to be independent and self-directed. It will run on batteries and will have a voltage sensor and charging circuit on board. The robot will walk forward and backward and be capable of making turns to the left and right. I will also include the use of an ultrasonic rangefinder and infrared sensors. This will allow the robot to see what is in its path and avoid any obstacles. The application I am working towards is an autonomous metal detecting robot. If time permits, I would like to add the features that will be needed to get the robot to this end. The features I will need to add are a Global Positioning Sensor (GPS), a discriminating metal detector and a transmitter. This will allow the robot to be restrained to a specified area, determine what metal it has detected and send the coordinates of its find to me. Description The robot will run on two rechargeable battery packs. One will power the microcontroller and the other will run the servo motors. The batteries will be monitored by a voltage sensor. There will be an LED located on board that will flash when the battery voltage falls below approximately 4V. I will also include an onboard battery charger that will provide a fast charge to Nickel Metal Hydride batteries. 1

2 The Daventech SRF04 Ultrasonic Range Finder will be used to enable the robot to map a room from approximately 1-inch to10 feet. The rangefinder will be mounted on a servo motor, which will allow readings to be taken at approximately 45 degree intervals. After the readings have been taken, the microcontroller will calculate the distance at each position and direct the robot to move in the direction of the most open area. When the robot gets within 6 inches of an object it will stop and take a new reading and move off in a new direction, thus avoiding any obstacles in its path. With the use of three Hitec Servo Motors, the robot will walk forward and backward and be capable of making turns to the right and left. The servos will be controlled by the pulse width modulators (PWM) on the HCS12 micocontroller. (See Figure 1) The PWM will also be used to control two infrared sensors placed on the front and back of the robot. These sensors will be facing directly down so the robot can tell if there is a drop off directly in front or directly behind its position. Charger Voltage Sensor Battery 2 Battery 1 Infrared Sensors Ultrasonic Range Finder Microcontroller Servo 1 Servo 2 Servo 3 Servo 4 Optoisolators Figure 1 2

3 Benefits Robots are still in their infancy. At the present time, we are only seeing the tip of the iceberg. Many people see robots as a threat to their security because many jobs can be done more efficiently by a robot. There are other areas in which a robot could be of benefit to our future growth and not be such a threat to our livelihood. Exploration is one of many examples. NASA uses unmanned robotic explorers to gather and transmit back atmosphere and meteorological information, soil analysis and pictures of neighboring planets in the solar system. Because I do not have the resources available that NASA has, this robot will not be as highly advanced as their systems but my final application will be exploration. There are many clubs that use metal detectors. By having an autonomous robotic metal detector, the people in the clubs will be able to cover more ground within the same time frame and reach areas they would not normally go themselves. The discriminator on the metal detector will be sensitive enough so it will only transmit the coordinates of the types of metals programmed, thus saving precious time not digging for an unwanted item. Comparison of Similar Products Although I built my robot from scratch (See Figure 2), there are kits available in various stages of development. Here are a few sample comparisons of what is available on the market today. Hexapod 1 Robot Body (No electronics) $ Includes; the robot chassis components, 3 HS-422 servos and complete hardware set. 3

4 Hexapod 1 for Basic Stamp II $ Includes; the robot body, Next Step/Basic Stamp 2, IRPD, NiMH battery/charger, programming cable and manual. Specifications for the Hexapod 1 -Servo motion control = local closed loop -Steering = differential -Motion speed = More than 8 per second -Height = 4 -W idth = 9.5 (leg to leg) -Length = 9.5 -Ground Clearance = 1.5 -Servo Voltage = rated 6Vdc -Servo Current required (idle) = 10mA each -Servo Current required (moving) = 130mA each -Servo Torque = 49 oz-in -Servo Speed = 90 in.24 sec. -Next Step Current requirements = 7mA HexCrawler Robot Kit $ Includes; the HexCrawler chassis, 12 Parallax Servos, HexCrawler Assembly and Programming Manual, BASIC Stamp Manual, Parallax CD-ROM, BASIC Stamp 2 module, Board of Education programming board, (2) Scott Edwards Mini SSC II serial servo controllers, resistors, 2 pushbuttons, and 7 segment LED. 4

5 HexCrawler Specifications -Power Supplies = (1) 9V Battery and 6 cell battery pack -Chassis Dimensions = 13 long, 8 wide, 6 tall -Ground Clearance = 3 to 4.75 (adjustable) -Leg Movement = 2 degrees of freedom ( vertical and horizontal) -Weight = 4.2 lbs. -Payload Capacity = 7.5 lbs. Development Plan Figure 2 Although I have built the prototype body of the robot, I may choose to purchase the Hexapod 1 body from Lynxmotion. Because the Hexapod s walking gait is virtually the same as the one I built, changing the body will not add any extra work the project development. I will be designing and building the voltage sensors and charger in the Etec lab. This will be complete before the end of this quarter. After the voltage sensors and charger are tested, I will put the circuit design on Eagle and have the board etched in the Etec lab. 5

6 The next major step in development will be learning to program the HCS12 microcontroller. During Christmas break, I will study the HCS12 manuals. During winter quarter, I will take the Et454 microcontroller class. This will give me the skills and tools I will need to program the microcontroller in the C language. The robot will be developed in the Etec lab at Western Washington University and at my home. The hardware needed to support the development of my project consists of an oscilloscope, multimeter, power supply, the HCS12 microcontroller, and personal computer. The software development environment will include CodeWrite, Noral, Tina, and possibly CodeWarrior. Demonstration The robot will be demonstrated at Western Washington University. I will place obstacles around the robot within a 4 to 6 foot radius. The robot will take a reading of its surroundings and determine which obstacle is furthest from its position. It will then walk towards the most open area and stop within 6 inches of any obstacle and take a new reading. It will continue this process until the demonstration is over. If the robot senses a drop off from the infrared sensors, it will stop immediately and remove itself from the situation. 6

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