Difference between revisions of "S14: Virtual Dog"

System Block Diagram:
The Hardware unit consist of three proximity sensors, SJOne board, four DC motors, bluetooth module, chassis, four wheels, and two batteries. All the three proximity sensors will measure their respective analog value and send it to the ADC pin of the SJOne board which will convert it to the digital value, the converted digital value will be utilized to determine the distance between the robot and the object. Based on the calculated distance the PWM value is determine for each DC motor, these PWM value is given as input to the DC motor via L293D IC. The Bluetooth device will read the value of the sensor from the SJOne board through UART and send it to the Android App which will display the real time value of the sensor as well as decision taken by robot.

Proximity Sensor:
This SHARP distance sensor bounces IR off objects to determine how far away they are. It returns an analog voltage that can be used to determine how close the nearest object is. These sensors are good for detection between 20cm-150cm. We are using three sensors for our project so that our robot can trace the position of object accurately in two dimensions. This sensor provide less influence on the colors of the reflected objects and reflectivity, due to optical triangle measuring method. There is no need of any external circuitry for this sensor. The recommended operating supply voltage for this sensor is from 4.5V to 5.5V.

DC Motor:
We are using four DC motors for our project, with rating 5-12V operating voltage @ 0.16Amp, 2000RPM. We are using DC motor so that we can provide 360 degree rotation to our robot wheel as well as it help to drive the robot at a very high speed. DC Motor converts electric energy into mechanical energy. A DC Motor uses direct current - in other words, the direction of current flows in one direction. The speed of DC motors is controlled using Pulse Width Modulation (PWM), a technique of rapidly pulsing the power on and off. The percentage of time spent cycling the on/off ratio determines the speed of the motor.

L293D IC:
L293D is a typical Motor driver or Motor Driver IC which allows DC motor to drive on either direction. L293D is a 16-pin IC which can control a set of two DC motors simultaneously in any direction. It means that you can control two DC motors with a single L293D IC. The L293D is designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V.

Bluetooth Module:
The RN-42 is compatible with the Bluetooth versions 2 and below. The advantage of using this module is it's low power and at the same time can provide a good data rate. This provides a high performance on chip antenna where data rates upto 3Mbps are transferred. The disadvantage is that, it has a very less distance which is approximately 20 meters. There is a pull up circuit of 1k to the Vcc. This is provided so that if the input power supply has instability or tends to bounce which causes the that device to be damaged. There is separate pin allocated for the Factory Reset such that this comes into the picture when the module is misconfigured. The toggle of the specific GPIO pins indicate the status of the module. When toggled at 1Hz, the module is discoverable and is waiting for a connection. When at 10Hz, it made to change to the command mode. If it is very low, then module is already connected to another device over the bluetooth.

Pin connections for IR Sensor through ADC:

Pin connections for Motor Driver using PWM:

Pin connections for Bluetooth Device:

Idea Behind Central Control Logic:

State Machine Diagram:
Based on the zones described earlier, we developed a state machine. Entire central logic relies on this state machine. Details of each state are described below:

• VD_STOP: This is the default state, when robot starts, it’s state first initialized to VD_STOP. When object is in Zone2, then also FSM is this state. In this state motor driver stops all the motors. If object moves to other zones, then FSM state is changed accordingly.
• VD_FWD: When object moves to Zone3 or Zone4, FSM is in this state. Based on the distance, motor driver drives the motors with appropriate speed when in this state. If object is detected in Zone2, FSM state is changed back to VD_STOP. If object suddenly disappears from middle sensor, FSM state is changed to VD_TURN.
• VD_REV: When object moves to Zone1, FSM is in this state. In this state, motor driver generates PWM signal in such a way that robot will move backwards. If object is detected in Zone2, FSM state is changed back to VD_STOP. If object suddenly disappears from middle sensor, FSM state is changed to VD_TURN.

• VD_FWD_LEFT: If object is detected in Zone3 or Zone4 of left sensor, FSM is in this state. In this state, motor driver generates PWM signal in such a way that robot will take left turn in forward direction. Robot will remain in this state until object is not detected back in Zone2 or Zone3 or Zone4 of middle sensor.
• VD_FWD_RIGHT: If object is detected in Zone3 or Zone4 of right sensor, FSM is in this state. In this state, motor driver generates PWM signal in such a way that robot will take right turn in forward direction. Robot will remain in this state until object is not detected back in Zone2 or Zone3 or Zone4 of middle sensor.
• VD_REV_LEFT: If object is detected in Zone1 or Zone2 of right sensor, FSM is in this state. In this state, motor driver generates PWM signal in such a way that robot will take left turn in backward direction. Robot will remain in this state until object is not detected back in Zone1 or Zone2 or Zone3 or Zone4 of middle sensor.
• VD_REV_RIGHT: If object is detected in Zone1 or Zone2 of left sensor, FSM is in this state. In this state, motor driver generates PWM signal in such a way that robot will take right turn in backward direction. Robot will remain in this state until object is not detected back in Zone1 or Zone2 or Zone3 or Zone4 of middle sensor.
• VD_TURN: When object suddenly disappears from middle sensor, FSM is in this state. In this state, motor driver stops all the motors. FSM remains in this state until object is detected by either of the sensor. Based on which sensor detects the object, FSM state is changed to appropriate state.
• VD_ALARM: If any other object/obstacle appears suddenly in between target object and robot, FSM is in this state. Motor driver stops all motors, and user is alarmed with the help of buzzer and blinking LED indicator.

Initialization:
On start process mainly does the initialization job. It initializes ADC pins (P0.26, P1.31, P1.30) that are used by IR sensors. Then PWM pins P2.1 through P2.4 are initialized for motor driver. We use GPIO to sound the buzzer, so GPIO pin P1.23 is configured as output in the init process. We use Bluetooth to connect to android device. Bluetooth device is connected via UART2 on the board. So init process also contains code part to init UART2 for Bluetooth device. After everything is set, three tasks start running, viz., sensor task, motor task and Bluetooth task. Sensor task continuously reads the sensor values, normalizes them and invokes our algorithm/FSM. Motor task generates appropriate PWM signals based on the current FSM state. Bluetooth task communicates with Android Application.

Sensor Driver:
In the Sensor Driver Task, the sensor values from all the three proximity sensors are read. They are normalized by using calculating the median of the previous 30 sensor values. Based on this, the object position is determined. If the object is located in the Zone 1 of the middle sensor, then the finite state machine is changed to reverse. The robot moves until the original position is achieved. If the object is located in the Zone 3 and Zone 4 of the middle sensor, then finite state machine is moved to the Forward state which causes the robot to move forward. If the left sensor detects the object in Zone 1 and Zone 2, the finite state machine is changed to reverse right. This moves the robot in the reverse right direction causing the direction of the robot indirectly to turn left. If the right sensor detects the object in Zone 1 and Zone 2, and the finite state machine is moved to the reverse left. This causes to change the direction of the robot indirectly to the right. If the left sensor detects the object in Zone 3 and Zone 4, the finite state machine is changed to forward left. This moves the robot in the forward and left direction causing the direction of the robot to turn left. If the right sensor detects the object in Zone 3 and Zone 4, the finite state machine is moved to the forward right. This causes to change the direction of the robot to the right. Thus based on the sensor values, the next stage of the Finite State Machine is decided and robot is move to that particular zone.

Motor Driver:
In the Motor Driver task, the finite state machine is read for each entry of the sensor data. Based on the state machine the Robot decides on the direction to move. If the decision made is forward, then the front two wheels which are connected to the driver are made to move. This causes the device to move forward. If it is forward left, then the front left wheel speed is decreased. This causes the device to turn left. If it is forward right, then the front right wheel speed is decreased. This causes the device to turn left. If the decision made is reverse, the wheels are made to rotate in the opposite direction. If it is reverse left, then the back left wheel direction is opposite and the speed is decreased. This causes the device to turn reverse left. If it is reverse right, then the back right wheel rotates in the opposite direction and the speed is decreased. This causes the device to turn reverse right. With the help of all the decisions, the Robot can be made to rotate 360 degree making the Robot to detect the object’s range and moving in appropriate direction. Finally, after Robot has moved such that the object comes into the ZONE_2, all the state machines are reset. This loop occurs until there is an indicator received telling the Robot to stop.

Virtual DOG Android Application:
The Android application helps in communicating with the Bluetooth module. The Bluetooth module is RN- 42. This module is directly placed in the location given for the zigbee module on the LPC board. Communication between the devices is full duplex. The initiation and the termination of the robot is controlled from the Android application.
On opening the application, the Bluetooth has to be turned ON. There are two Buttons for turning the Bluetooth ON and OFF. For the Bluetooth to be turned ON, permissions is required from the User. If the authentication is performed, then the devices which are available in the range of the Bluetooth module are listed down using the discovery method of the device. The Module’s name is selected in the mobile. The devices are paired together using a key. The key provides the security feature over the transmission and reception.
There are two buttons. The ‘START’ and ‘STOP’ button which indicate the robot to turn ON and OFF. This button is created in the XML. This language is used to build the UI functionalities. On clicking the START button, data is written to the Robot in order to indicate the Start status. The robot starts sensing and send back the values along with the direction in which it moves. This is sent in the form of a metadata, so that the time taken for transmitting is less. This improves the performance. The Metadata which comprises of the sensor values and the direction is received until the stop button is pressed. A separate data is written for stopping the data. The robot stops on receiving this data.
In order to connect with the robot faster, a separate list has been created which maintains the list of the paired devices. This will show the devices which were connected previously.
There is a new fragment (page) created from the MainActivity which is created and the device is opened with that new fragment. On successful completion of the pairing, there are some threads which are made to run in the background. On creation of the instance of the new fragment page, a thread to read the data on the output stream runs as one of the background process. This buffer which is read should happen continuously until there is ‘\n’ or ‘\r’ character is read. If it read, then the data from the UART of the module is read.

Front View:

Side View:

Top View:

When 1st and 4th LED are blinking, it indicates that object is in range, i.e. Zone2 and FSM state is VD_STOP.

When 2nd and 3rd LED glows continuously, it indicates that object has moved forward, i.e. in Zone3/Zone4 and FSM state is VD_FWD.

When 1st and 4th LED glows continuously, it indicates that object is coming closer, i.e. in Zone1 and FSM state is VD_REV.

When 1st and 4th LED blinks, it indicates that object is taking turn, and robot is trying to figure out where the object has turned and FSM state is VD_TURN. If robot is not able to find out turned object, it means that object has moved out of range.

When 1st and 2nd LED glows continuously, it indicates that object is turning to left and FSM state is VD_FWD_LEFT.

When 3rd and 4th LED glows continuously, it indicates that object is turning to right and FSM state is VD_FWD_RIGHT.

When only 1st LED glows continuously, it indicates that object is turning to left but in backward direction and FSM state is VD_REV_LEFT.

When only 4th LED glows continuously, it indicates that object is turning to right but in backward direction and FSM state is VD_REV_RIGHT.

When all LEDs blink fast, it indicates that some obstacle has detected and FSM state is VD_ALARM.