MASTER SHIFU. STUDENT NAME: Vikramadityan. M ROBOT NAME: Master Shifu COURSE NAME: Intelligent Machine Design Lab

Transcription

1 MASTER SHIFU STUDENT NAME: Vikramadityan. M ROBOT NAME: Master Shifu COURSE NAME: Intelligent Machine Design Lab COURSE NUMBER: EEL 5666C TA: Andy Gray, Nick Cox INSTRUCTORS: Dr. A. Antonio Arroyo, Dr. Eric M. Schwartz 1

2 TABLE OF CONTENTS 1. Abstract.3 2. Introduction 4 3. Integrated System Mobile Platform 8 5. Actuation Sensors Behavior Documentation 15 2

3 ABSTRACT Master Shifu. The King of Kung Fu. He looks small (yes he is a mouse in the movie!) but do not underestimate his powers. His petite limbs and flexible body make him the Master of the art. He demonstrates his prowess using chopsticks and leaves us all spellbound. Small and stunning, that s what it s all about! 3

4 INTRODUCTION I liked the character of Master Shifu from the movie Kung Fu Panda. I had always wanted to make a robot that walks on legs and not move on wheels. When I realized I could build one using chopsticks, I could not resist. The design and construction of this robot is relatively simple and cheap as well. The overall mass of the robot is also low. Micro servos will be used for movement of the robot and IR sensors for obstacle detection. The system will be run on an Arduino Due processor. 4

5 3. INTEGRATED SYSTEM µservo µservo IR IR µservo µservo Arduino Due µservo µservo LiPo µservo µservo Battery The robot is powered by Arduino Due processor. It will run 8 micro servo motors and 2 IR sensors. The board will be powered by a 7.4V LiPo Battery which will be regulated down to 5V by a regulator. At a given time, one micro servo will be run (temporarily) followed by sequential delays to make the robot walk. I soldered a regulator on a perf board to bring down the voltage to 5V from 7.4V, and got out the output wires. This will power the servos. 5

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7 7 Fig 3.2

8 4. Mobile Platform A rectangular frame will be the platform of the robot. This will accommodate the battery and the board, owing to supports given at the bottom. At each of the joints of these supports and frames, legs will be screwed in, and micro servos attached. This kind of construction made by wooden slabs or chopsticks will reduce the overall weight of the robot. Since only micro servos are used, it will hence be easier for movement. Also I realized that, framed platform would look better than boxed ones for my robot! Fig 4.1 8

9 5. ACTUATION Servos are controlled by sending them a pulse of variable width. The control wire is used to send this pulse. The parameters for this pulse are that it has a minimum pulse, a maximum pulse, and a repetition rate. Given the rotation constraints of the servo, neutral is defined to be the position where the servo has exactly the same amount of potential rotation in the clockwise direction as it does in the counter clockwise direction. It is important to note that different servos will have different constraints on their rotation but they all have a neutral position, and that position is always around 1.5 milliseconds (ms). Fig. 5.1 The angle is determined by the duration of a pulse that is applied to the control wire. This is called Pulse width Modulation. The servo expects to see a pulse every 20 ms. The length of the pulse will determine how far the motor turns. When a pulse is sent to a servo that is less than 1.5 ms the servo rotates to a position and holds its output shaft some number of degrees counterclockwise from the neutral point. When the pulse is wider than 1.5 ms the opposite occurs. The minimal width and the maximum width of pulse that will command the servo to turn to a valid position are functions of each servo. Different brands, and even different servos of the same brand, will have different maximum and minimums. Generally the minimum pulse will be about 1 ms wide and the maximum pulse will be 2 ms wide. 9

10 Fig. 5.2 My robot will involve a total of 8 micro servos. Each of these are: Size : 23x11x29 mm Voltage : 3V to 6V DC Weight: 9g / 0.32oz Speed : 0.12 sec/60 (at 4.8V) Torque : 1.6 kg-cm Fig 5.3 Since only one micro servo will be in action at one given time and given that the Arduino Due can function at 3.3V, minimum voltage can be fed in. 10

11 The robot consists of four legs. Each leg is made of two parts the shoulder and the arm. Two micro servos will be attached to each leg, one at the joint of the frame and the shoulder and the other at that of shoulder and the arm. Thus the servo at the shoulder is first rotated followed by the respective arm and this movement is repeated by the diagonally opposite leg. The same set is performed by the remaining two legs. The rotation of the shoulder will help cover the height required for the arm to lift and cover the horizontal distance. 11

12 6. SENSORS Sharp IR sensors will be used for detecting obstacles. If the robot detects an obstacle, it will move back walk away from it. The demo was done on the obstacle detection demo day. Here I used just the shoulders of the robot and I had not attached the arms yet. Fig

13 The coding used to control 4 motors is shown in the following screenshot. 13

14 7. BEHAVIOUR The robot will be able to move forward when the micro servos in the front leg are activated, followed by those on the diagonally opposite hind leg. The robot will have covered a certain distance in one cycle, which is called gait. For sideways movement, the micro servos on the forward leg is activated followed by the other forward leg, after which the hind leg servos are activated. The robot will have two PIR sensors mounted on both the forward legs which will detect obstacles in its range and command the robot accordingly to avoid them. The special sensor of my robot system will be the walking mechanism and the different movements that are possible. 14

15 8. DOCUMENTATION I used the following websites