New Sensors for Ridgesoft Robot

Transcription

1 New Sensors for Ridgesoft Robot Joanne Sirois CEN 3213 Embedded Systems Programming Dr. Janusz Zalewski FGCU April 9, 2008

2 Sirois, 2 1. Introduction 1.1 Basics of IntelliBrain TM Robot The IntelliBrain TM robotics controller is a micro controller board designed to enable you to build robots using Java, and a powerful microcontroller, Atmel ATmega128. The IntelliBrain is made up of two circuit boards, a main board and an expansion board. The main board features are illustrated in Figure 1. The IntelliBrain controller s design makes it possible to use many kinds of sensors. Also, the IntelliBrain uses the LCD display, push buttons, thumbwheel, buzzer, and LEDs to help with user interface. 1.2 Features on My Robot Figure 1.1 IntelliBrain Main Board Features [3] Figure 1.2- My IntelliBrain Robot

3 Sirois, 3 CMUCam2+ can be used to track user defined color segments up to 50FPS and track motion using frame differencing at 26FPS. Other features include: transfer of realtime binary bitmap of tracked pixels in an image, arbitrary image windowing, dump a raw image (single or multiple channels) and more. Figure 1.3- Bluetooth Communicator (Female Module) The Bluetooth module uses Gaussian Frequency shifting GFSK and work at the ISM band of 2.4 GHz. The modules are divided into Master and Slave. The master module looks for any slave modules in range and saves their address and connects to it. The master is in charge of setting the frequency hopping sequence which insures that no other wireless devices are disturbed. Bluetooth communication uses Asynchronous Connectionless links (ACL) for its data communications. ACL link sends data at irregular intervals whenever data is available. Some of the ACL link ensures data accuracy by checking for errors and resending data if needed. The Access code, header and a payload are embedded into a packet which is transmitted. The control information is contained in the header part of the packet and the actual data message is contained in the payload part of the packet.

4 Sirois, 4 Figure 1.4- Infrared Range Sensor Infrared Range Sensor gives the IntelliBrain the ability to sense and avoid objects. Range sensors use infrared beams to determine the distance of an object under the exception of being exposed to direct sunlight or when facing reflective glittering surfaces where the sensors shall show inaccurate data. Figure 1.5- Sonar Sensor The sonar range finder works by generating a short burst of sound a ping then listening for the echo of the sound when it bounces off the nearest object, as shown in Figure 6. By measuring the time from the start of the ping until the echo returns back to the sensor, the distance to the nearest object can be easily calculated. Figure 1.6- Sonar Ping and Echo [1] 1.3 New Sensors to be added onto Robot Devantech Electronic Compass

5 Sirois, 5 Figure 1.7- Devantech Electronic Compass [2] This module has been specifically designed to aid robots in navigation. The compass uses two Philips KMZ51 magnetic field sensors. The output of the two of them mounted at right angles to each other are used to compute the direction of the horizontal component of the magnetic field. Devantech Thermal Array Sensor (TPA81) Figure 1.8- TPA81 [2] The TPA81 is an array sensor. This device is capable of detecting infra-red at radiant heat wavelengths (2µm-22µm). It can also control a servo to pan the module and build up a thermal image. Heat sources can be detected at a range of 2 meters, and the sensor is unaffected by ambient light. A TPA81 thermal array sensor consists of an array of thermopiles. A thermopile detector is a number of thermocouple, or thermistors, connected in a series. In the thermopiles the two sides of a thermocouple are exposed to different heat sources. One

6 Sirois, 6 side is the stable source the other can be directed at sources of interest. The difference in temperature produces a measurable voltage. The Eltec Pyroelectric Sensor Figure 1.9- Eltec Pyroelectric Sensor This sensor helps you detect the movements of humans and pets. It can also be used in finding sources of heat. This is accomplished through infrared energy detection. A single pryoelectric detector can find changes in infrared energy between 8-14 micrometers. 2. Problem Specification 2.1 Problem Description I will be attempting to make an extension on Neven Skoro s Bluetooth Robot Controller by adding sensors onto the IntelliBrain Robot. There is a need for a remote robot controller that will enable the two way communication between the user and the robot. With the Bluetooth technology we can have a two way communication which works on radio frequency up to 100 meters in distance. Furthermore, I want to control the robot with a user interface such as a joystick and keyboard. The robot could then pass the data such as distance, speed, battery power, etc. back to the user. [4] With combination of the new sensors the user could then decide what he wants to do with the robot according to the data received. With the extra sensors the user can choose to receive the direction he is travelling in, receive a thermal image or be noticed of changes in infrared energy between 8-14 micrometers. 2.2 Problem Requirements

7 Sirois, 7 a) Robot moves will respond to joystick positions b) Robot will be able to detect objects in its pathway c) Robot will store the path x and y coordinates in a double array variable d) Robot will be able to follow its previous memorized path [4] e) Robot will be able to detect the direction he is travelling in f) Robot will be able to send a thermal image g) Robot will report changes in infrared energy h) Robot will be able to send images i) Robot will be able to detect motion 2.3 Input Data Requirements a) It allows the use of two buttons for start and stop of the program. b) Using the range sensors it inputs the distance data and converts it to centimeters. c) The robot registers user inputs from joystick and keyboard. 2.4 Output Data Requirements a) The controller displays various data and warnings on the LCD screen. b) Range sensors output the infrared signal to the environment. c) Shaft encoders send out infrared beams to the wheels. d) The controller sends the signal to the servomotors to calibrate the power. e) Eltec Pyroelectric Sensor sends notice of changes in infrared energy between 8-14 micrometers. f) Devantech Electronic Compass sends the direction of the horizontal component of the magnetic field. g) TPA81 builds up a thermal image and send it. 2.5 Joint Input/output Data Requirements a) The controller shall send and receive the short burst of sound from the sonar sensors [5] 2.6 Detailed Functional Requirements

8 Sirois, 8 a) Sonar sensor sends a signal and receive an echo from an obstacle, it then converts the analog sound to digital, analyzes the data and calls the methods getdistance() to calculate how far away the obstacle is. [5] b) Different sensors send data to the LCD screen in a format of two lines, and the controller shall have a class that contains several screen objects, which are called via the update method. [5] c) Display different information on the LCD screen will get the minimum priority because they are not as crucial to be executed on time [5] d) Range sensors use infrared beams to determine the distance of an object under the exception of being exposed to direct sunlight or when facing reflective glittering surfaces. [2] e) By controlling servos control circuitry we can adjust different power levels to each of the servos thus enabling the robot to curve and not just move straight. [3] f) Calculations are used to determine if the robot should reverse and turn in order to go around an obstacle. [3] g) When using dead reckoning the robot will be able to keep track of Y, X and Theta variables on a graph. When the wheels rotate forward a counter shall add up and when the wheels rotate backwards the counter will reduce itself. Calculation of the counts per rotation on the other had shall be calculated by dividing the wheel diameter by the track width and multiplying it with the counts per revolution. [5] h) Pryoelectric detectors can find changes in infrared energy between 8-14 micrometers. i) TPA81 is capable of detecting infra-red at radiant heat wavelengths (2µm-22µm). Can be used to build up a thermal image. j) The compass uses two Philips KMZ51 magnetic field sensors, the output of the two of them mounted at right angles to each other are used to compute the direction of the horizontal component of the magnetic field.

9 Sirois, 9 3. Design Description The robot controller communicates with multiple classes as shown below. It sends warnings and data to the display screen and receives inputs from the front panel for start and stop or to scroll through different functions. It communicates with the 2 range sensors and the sonar sensor back and forth. The range sensors and the sonar sensor communicate with the robot controller and report any data that indicate there are obstacles in the way. The navigator class sends information to the servos of how much power to use in order to turn in the right direction and thus navigate towards the destination. Figure 3.1 IntelliBrain context diagram [5] Along with these basics, we also have the Bluetooth controller, which was implemented by Neven Skoro. The joystick used is an Analog Raider Pro Joystick which will be connected via a Male 15 pin cable through a game port. Both the serial communication between the PC and the Bluetooth and the communication between the robot and the Bluetooth module will be implemented. From the context diagram we can see which communication protocols are needed for this design.

10 Sirois, 10 Figure 3.2 Context Diagram [4] Also we have the sensors that I will be adding on. Which were the Devantech Electronic Compass, Devantech Thermal Array Sensor (TPA81), and Eltec Pyroelectric Sensor. 3.1 Devantech CMPS03 Magnetic Compass The Devantech magnetic compass allows a robot to sense direction based on the Earth's magnetic field. The CMPS03 has a pulse interface and an I2C interface. In Example Code 1 the class provides an example of the Devantech CMPS03 magnetic compass attached to the IntelliBrain. In the psuedocode the compass is only read once per iteration because it only generates a new reading every milliseconds. Example Code 1: (Pseudocode) public class IntelliBrainCMPS03 { public static void main(string args[]) { try { Get the LCD display Instantiate the compass object

11 Sirois, 11 while (true) { Read the compass (once per iteration) Sleep for 250 ms //end while //end try catch (Throwable t) { Display a stack trace for any error //end catch //end main //end class 3.2 Devantech Thermal Array Sensor (TPA81) The TPA81 is a thermopile array detecting infra-red in the 2um-22um range, which is the wavelength of radiant heat. The Pyro-electric sensors that are used commonly in burglar alarms and to switch on outside lights, detect infra-red in the same waveband. These Pyro-electric sensors can only detect a change in heat levels and therefore they are only movement detectors. Figure Spectral Response [2]

12 Sirois, 12 The response of the TPA81 is typically 2µm to 22µm as shown above. Commands 0 to 31 set the servo position. There are 32 steps (0-31) which typically represent 180 rotation on a Hitec HS311 servo. The calculation is SERVO_POS*60+540uS. So the range of the servo pulse is 0.54mS to 2.4mS in 60uS steps. Writing any other value to the command register will stop the servo pulses. [2] Table 3.1 Servo Positions In Example Code 2 the sensor array readings are compared to the room temperature and the resulting difference (range of 0-9) is printed out. Example Code 2: (Pseudocode) void main(){ set 400KHz I2C baud rate read the sensor 8 times per second while(true){ read all the pixels and compare with ambient temperature and print sleep(1250); //end while //end main 3.3 Eltec Pyroelectric Sensor A temperature change will cause the analog output of the sensor to produce a large peak and a large dip. Otherwise, the output will stay around 2.5 volts. A large

13 Sirois, 13 difference between the max and min indicates detection of something warm. The positions where the min and max occur give some indication of where the warm object is. Example Code 3: (Pseudocode) void eltec-1(void){ int value; while(true){ delay to stop display from flickering check the analog port check values (neutral values hover around 128) if(value > 134){ moving left else{ if(value < 122){ moving right else{ Neutral //end else //end else //end while //end main Example Code 3 is used to pick up a person s movement. The detector s output is relative it can be moved in front of the detector or be moved across the area to get a measurement. 4. Implementation and Testing

14 Sirois, 14 The implementation of the project turned out to be a lot more complex than originally thought. Although most of the coding in the project was pretty straight forward, calibration and initialization of the sensors at first turned out to be very complex. 4.1 Devantech CMPS03 Magnetic Compass The Devantech CMPS03 Magnetic Compass was the easiest of the three sensors was the easiest of the three sensors. Calibration only needs to be done once. Thanks to code from Rridgesoft.com I was able to calibrate the compass. I implemented a function so that whenever the IntelliBrain robot is moved it will out print on the LCD screen the direction it is traveling in. This is a relatively small function called run. It takes no inputs and out prints only to the LCD Screen. Below you can see a picture of the out print in Figure 4.1 and the function run. 4.1 Outprint for Compass Function Compass.run( ) public static void run() { try { // Instantiate the compass object, giving it the heading pulse input port. DevantechCMPS03I2C compass = new DevantechCMPS03I2C(IntelliBrain.getI2CMaster());

15 Sirois, 15 System.out.println("CMPS03, SW Version: " + compass.getsoftwarerevision()); Display display = IntelliBrain.getLcdDisplay(); // Get the LCD display display.print(0, "Devantech CMPS03"); // Write test name on first line display.print(1, ""); // Clear second line PushButton startbutton = IntelliBrain.getStartButton(); startbutton.waitreleased(); // Loop forever. while (true) { int heading = compass.heading(); display.print(1, compass.direction(heading) + ' ' + heading); Thread.sleep(250); catch (Throwable t) { t.printstacktrace(); // Display a stack trace for any error This function is called in the main class MyRobot, originally implemented by Neven Skoro, edited by me for my project. Again this is out printed when the robot moves. 4.2 Devantech Thermal Array Sensor (TPA81) This sensor was difficult to implement. Due to the fact that the array senses heat many objects interfered with the sensor. Even the computers messed up the sensor. I made a decision to not out print the information to the LCD screen. Instead the information is stored in an array on the computer. There are three functions in

16 Sirois, 16 ThermalArray.class, comparepixel(), takes in two char returns a char, readtpa81 stores the information., and run() executes the Thermal Array Sensor. ThermalArray.run() void run(){ //read the sensor 8 times per second while(true){ readtpa81(); // this function compares the pixels and stores data in an array Thread.sleep(1250); ThermalArray.comparePixel() char comparepixel(char x, char amb){ //scale comparison result to 0-9 if(x > amb){ x = (x-amb)/8 if(x > 9) x=9; else{ x = 0; return x; 4.3 Eltec Pyroelectric Sensor

17 Sirois, 17 This sensor was also very difficult to implement due to light leakage and other physical features. Since the detector is very sensitive outputs do not always act as expected. This sensor picked up movements from far away in the room and ended detecting objects I did not plan on being detected. The sensor is used to detect motion and return the direction it is traveling in. The function is named run() and is called in the main class. PyroSensor.run() public void run(){ line Display display = IntelliBrain.getLcdDisplay(); display.print(0, "Eltec Pyroelectric"); display.print(1, ""); int value; try{ while(true){ value = analog(0); Thread.sleep(2500); if(value > 134){ // Get the LCD display // Write test name on first // Clear second line display.print(1, "Moving Left"); else{ if (value < 122){ display.print(1, "Moving Right"); else{ display.print(1, "Neutral");

18 Sirois, 18 catch (Throwable t) { t.printstacktrace(); // Display a stack trace for any error Figure 4.2 Out Print for Eltec This out print was made by sweeping the IntelliBrain in front of me allowing it to get a good measurement without the interference of other unwanted detections. References [1] Ridgesoft Inc., [2] Robot Electronics, [3] Ridgesoft IntelliBrain Robot Manual [4] Bluetooth Robot Controller. Neven Skoro. [5]A Study on Robotics. Neven Skoro and Jonathan Eren.