WIRELESS VEHICLE WITH ANIMATRONIC ROBOTIC ARM

Transcription

1 WIRELESS VEHICLE WITH ANIMATRONIC ROBOTIC ARM PROJECT REFERENCE NO. : 37S0918 COLLEGE : P A COLLEGE OF ENGINEERING, MANGALORE BRANCH : ELECTRONICS & COMMUNICATION GUIDE : MOHAMMAD RAFEEQ STUDENTS : CHARANENDRA BEKAL KAR AKASH ARUN MB MOHAMMAD ANFIZ Keywords: Arduino, Flex sensors, Potentiometers, Wireless RF module, Teaching Robot, Data gloves Introduction: In today s world there is an increasing need to create artificial arms for different inhuman situations where human interaction is difficult or impossible. Robotic arms are becoming increasingly popular in several fields such as industrial automation, medical applications such as remote key-hole surgeries and military applications because of its preciseness and accuracy. In certain critical applications such as performing surgeries or diffusing a bomb, robotic arms could be of tremendous use to save lives. In such applications, controlling the robotic arm precisely is of at most importance. The Robotic arm used in industries and other sectors operates by executing the instructions stored in its processor. Hence Human-Robot interaction is less. As the technology improves there is a need to have greater interaction between Human and Robot so that the assigned work can be carried out as required by the user. At present, direct interaction between humans and robots is generally limited to physical guidance of assistive tools such as liftassist devices. Most of the robotic devices used are controlled by wired communication. Hence separate communication cables have to be laid for each device which increases the cost and maintenance. 1

2 In this project we have implemented wireless gesture controlled robotic arm using flex sensors and servo motors. The wireless communication is achieved using XBee modules. The wireless communication enables user to communicate with robotic arm from 300ft or 100m distance. The user can switch to different XBee easily while dealing with multiple robotic devices. The flex sensors where made manually using conductive plastics which are way cheaper than standard flex sensors. Objective: This Project aims at developing a novel, wireless embedded teaching system for a multijointed wireless robotic arm. Differing from the traditional teaching panel method, the proposed method does not require any complex computations for coordinate transformation and is a simpler scheme. The proposed teaching system includes a small teaching robot, which is scaled to the real jointed robot, however, joints are replaced with potentiometers and a flex sensor based Data Gloves for detecting the movements of the user s fingers. The main control board (Arduino) receives voltage signals from the teaching robot via its analog pins and transforms them into position commands for the motion of each joint and fingers. When a flex sensor is bent at certain angles, the voltage across it changes. This voltage sensed is processed by arduino to rotate the corresponding servo motors wirelessly using Xbee radio frequency module. In order to make the system mobile, the Robotic arm is mounted over a 4 wheeled robotic vehicle. The vehicle is controlled using joystick and wireless camera. With the aid of arm & vehicle movement controller and wireless camera the whole unit can be controlled from a span of 100 meters wirelessly. 2

3 Methodology: Schematic Diagram: Fig 1: Wireless Communication between User s hand and Robotic Arm The Fig 1 shows the internal connections required to establish wireless communication between the Robotic arm and Human Arm. The values from Potentiometers and or flex sensors are fed to analog inputs of Sender arduino. The processed output is passed via XBees to Receiver arduino by serial communication. The received signal is further processed and sent to respective servo motors using PWM output pins of Receiver arduino. List of Hardware components used for the Wireless Animatronic Robotic Arm: 1. Arduino. 2. Xbee Module. 3. Xbee Shield. 4. Potentiometers. 5. Flex Sensors. 6. Servo motors. 3

4 Working of Robotic arm for Shoulder, Elbow and Wrist movements: Initially the control output potentiometers are connected to the analog pins of the arduino. A voltage of 5V is applied to the remaining 2 terminals of the potentiometers. When the user places his hand over the teaching robot and moves it, the values of potentiometers changes. These analog values from potentiometers are received by the arduino in analog form. The inbuilt analog to digital converter converts these analog values into corresponding digital values with values ranging from 0 to The values of all the potentiometers are checked sequentially with the delay of 15ms and are stored in the user defined variable. Then these values are mapped to angles in between 0 to 180 for servo to rotate. Basically map functions are used to convert values from one acceptable range to other acceptable range. They are then sent to receiver arduino using XBee modules. The XBees are configured to establish serial communication at the Baud rate of using XCTU software. At the receiving side, the arduino receives the data serially. During serial transmission the values that are sent may be added or subtracted by small factors due to presence of the noise through the channel. Hence by using constrain function the angles are restricted in between 0 & 180. The values are then sent to the respective servo motors via PWM digital pins. Working of Animatronic Finger: Workings of fingers are similar to that of the robotic arm but slight differ in assigning angles to the servos. The flex sensors attached to the Data gloves are connected in a voltage divider circuit by replacing one of the resistors as shown in figure below. 4

5 5V Flex Sensor To analog pin of arduino Resistor whose value is nearly equal to flex sensor at mid range condition Fig 2 Voltage Divider circuit using flex sensor and resistor When the flex sensors are stretched, the resistance increases. This voltage change is sent to the analog pins of arduino. The digital values after analog to digital conversion is very small compared to potentiometer reading i.e., between 0 to 50. These values are not mapped directly to angles between 0 to 180 degrees since slight change in flex sensor value will rotate the servo nearly by 3 to 4 degrees. This results in shaky fingers. To make the finger stable at different values, we consider a range of values from flex sensors to have one common value in degrees. For example, values from 0 to 10 to have constant value 0 degree, 11 to 20 to have constant value 25 and so on. These values are then sent to respective servo motors which rotate by desired angle. Working of Robotic Vehicle: The Robotic Vehicle is controlled by voltage divider circuit with different resistor values. When the push button is pressed the voltage across it is read from analog inputs of arduino and converted into digital values in the range 0 to If the value is 791 the motor moves forward or else if the value is 0 the motor moves backward. When the value is 994, the robot turns left and if 793 the motor turns right. To achieve this certain logical combinations has to be given as input to the motor driver for the motor to rotate in the required direction. The logic behind the working of motor driver is shown in table below. 5

6 Result: The entire unit except vehicle was powered by using 6V, 10A lead acid battery and the robot was controlled wirelessly from a distance of 50m. It was found that all the movements were imitated by the Animatronics Robotic arm with very small delay between the movements. The Robotic vehicle was powered by 12V, 2A battery. This battery was also used to power up the arduino s near the vehicle end. The entire system was powered up for testing and observing the behaviour of each unit while working together. It was found that the system was imitating the hand movements made by the user as defined by the objective of this project. The movement of vehicle was also synchronized with the joystick controller output. Fig 3 Data Gloves Fig 4 Teaching Robot Fig 5 Wireless Robotic vehicle with Animatronic Robotic arm 6

7 Conclusion: Growing demand for natural Human Machine Interfaces and robot easy programming platforms, a gesture recognition system that allows users to control an industrial robotic arm was proposed and implemented successfully. A potentiometer based teaching robot was selected to be the input device of this system, capturing the human arm behaviour to control the robotic arm movement and 5 flex sensors were used to control finger movement. When compared with other common input devices, this approach using the above mentioned devices over wireless medium is easier to work. Using this system, a non expert robot programmer can control a robot quickly and in a natural way. The low price and short set up time are other advantages of the system. In additional to this, other features like Wireless camera and mobility using Robotic vehicle was successfully implemented. Future work: Currently the Animatronic arm which we have designed has less power to lift any heavy weight objects. This is because we have used servo motor of less torque since high torque servo motors were quiet expensive. For Industrial and other applications high torque servo motors can be used to lift more weights. The finger movements can be made smoother by using good quality flex sensors or by using more carbon containing plastics. Also by using 360 degree rotation servo motors instead of 180 degrees servo motors the finger movements can be made more accurate and smoother. The range of XBees used in this project has been restricted to 100m in outdoor environment. By using repeaters and extenders the range of antenna can be increased. 7